Experimental cancer treatment
Encyclopedia
Experimental cancer treatments are medical therapies intended or claimed to treat cancer
(see also tumor
) by improving on, supplementing or replacing conventional methods (surgery
, chemotherapy
, radiation
, and immunotherapy
).
The entries listed below vary between theoretical therapies to unproven controversial therapies. Many of these treatments are alleged to help against only specific forms of cancer. It is not a list of treatments widely available at hospitals.
) and whether it is sufficiently safe. Regulatory processes attempt to balance the potential benefits with the potential harms, so that people given the treatment are more likely to benefit from it than to be harmed by it.
Medical research for cancer begins much like research for any disease. In organized studies of new treatments for cancer, the pre-clinical development
of drugs, devices, and techniques begins in laboratories, either with isolated cells or in small animals, most commonly rats or mice. In other cases, the proposed treatment for cancer is already in use for some other medical condition, in which case more is known about its safety and potential efficacy.
Clinical trial
s are the study of treatments in humans. The first-in-human tests of a potential treatment are called Phase I studies. Early clinical trials typically enroll a very small number of patients, and the purpose is to identify major safety issues and the maximum tolerated dose
, which is the highest dose that does not produce serious or fatal adverse effect
s. The dose given in these trials may be far too small to produce any useful effect. In most research, these early trials may involve healthy people, but cancer studies normally enroll only people with relatively severe forms of the disease in this stage of testing. On average, 95% of the participants in these early trials receive no benefit, but all are exposed to the risk of adverse effects. Most participants show signs of optimism bias
(the irrational belief that they will beat the odds).
Later studies, called Phase II and Phase III studies, enroll more people, and the goal is to determine whether the treatment actually works. Phase III studies are frequently randomized controlled trial
s, with the experimental treatment being compared to the current best available treatment rather than to a placebo
. In some cases, the Phase III trial provides the best available treatment to all participants, in addition to some of the patients receiving the experimental treatment.
drugs
have a hard time penetrating tumors to kill them at their core because these cells may lack a good blood supply. Researchers have been using anaerobic bacteria, such as Clostridium novyi
, to consume the interior of oxygen-poor tumours. These should then die when they come in contact with the tumour's oxygenated sides, meaning they would be harmless to the rest of the body. A major problem has been that bacteria do not consume all parts of the malignant tissue. However combining the therapy with chemotheraputic treatments can help to solve this problem.
Another strategy is to use anaerobic bacteria that have been transformed with an enzyme that can convert a non-toxic prodrug
into a toxic drug. With the proliferation of the bacteria in the necrotic
and hypoxic
areas of the tumour, the enzyme is expressed solely in the tumour. Thus, a systemically applied prodrug is metabolised to the toxic drug only in the tumour. This has been demonstrated to be effective with the nonpathogenic anaerobe Clostridium sporogenes
.
that kills tumor cells by a process resembling programmed cell death (apoptosis
). It has been tested in humans with skin papilloma
s and bladder cancer
.
. Because it was tested for other conditions, DCA is known to be relatively safe, available, and inexpensive, and it can be taken by mouth as a pill, which is convenient. Early animal studies received attention in the media, and some doctors began controversially using the chemical off-label. , no patients had been treated with DCA in a clinical trial, and so its actual effectiveness is unknown.
shows some antitumor activity. Cultured skin and prostate cancer cells showed significant mortality (compared to nonmalignant cells) when treated with a combination of quercetin and ultrasound
Note that ultrasound also promotes topical
absorption by up to 1,000 times, making the use of topical quercetin and ultrasound wands an interesting proposition.
High dietary intake of fruits and vegetables is associated with reduction in cancer, and some scientists suspect quercetin may be partly responsible. Research shows that quercetin influences cellular mechanisms in vitro and in animal studies, and there is limited evidence from human population studies that quercetin may reduce the risk of lung cancer.
(IPT), insulin
is a controversial supplement to low-dose chemotherapy. Its proponents claim insulin therapy increases the uptake of chemotherapeutic drugs by malignant cells, permitting the use of lower total drug doses and reducing side-effects.
The first clinical trial, involving 30 women with breast cancer
, combined insulin with low-dose methotrexate
(a common chemotherapy drug) resulted in greatly increased stable disease, and much reduced progressive disease, compared with insulin or low-dose methotrexate alone.
, the tumour suppressor gene that protects the cell in response to damage and stress. It is analogous to deciding what to do with a damaged car: p53 brings everything to a halt, and then decides whether to fix the cell or, if the cell is beyond repair, to destroy the cell. This protective function of p53 is disabled in most cancer cells, allowing them to multiply without check. Restoration of p53 activity in tumours (where possible) has been shown to inhibit tumour growth and can even shrink the tumour.
As p53 protein levels are usually kept low, one could block its degradation and allow large amounts of p53 to accumulate, thus stimulating p53 activity and its antitumour effects. Drugs that utilize this mechanism include nutlin
and MI-219, which are both in phase I clinical trials. There are also other drugs that are still in the preclinical stage of testing, such as RITA and MITA.
is a small molecule
inhibitor
of the Aurora B kinase
protein being developed by Boehringer Ingelheim for use as an anti-cancer agent. BI 811283 is currently in the early stages of clinical development and is undergoing first-in-human trials in patients with solid tumors and Acute Myeloid Leukaemia
.
s into rapidly dividing cells has been thought to slow down or arrest tumor growth. Adenoviruses
are a commonly utilized vector for this purpose. Much research has focused on the use of adenoviruses that cannot reproduce, or reproduce only to a limited extent, within the patient to ensure safety via the avoidance of cytolytic
destruction of noncancerous cells infected with the vector. However, new studies focus on adenoviruses that can be permitted to reproduce, and destroy cancerous cells in the process, since the adenoviruses' ability to infect normal cells is substantially impaired, potentially resulting in a far more effective treatment.
Another use of gene therapy is the introduction of enzyme
s into these cells that make them susceptible to particular chemotherapy agents; studies with introducing thymidine kinase
in glioma
s, making them susceptible to aciclovir
, are in their experimental stage.
for their immortality, it has been proposed that a drug that inactivates telomerase might be effective against a broad spectrum of malignancies. At the same time, most healthy tissues in the body express little if any telomerase, and would function normally in its absence. Currently, Inositol hexaphosphate, which is available over-the-counter, is undergoing testing in cancer research due to its telomerase-inhibiting abilities.
A number of research groups have experimented with the use of telomerase inhibitors in animal model
s, and as of 2005 and 2006 phase I and II human clinical trials
are underway. Geron Corporation, is currently conducting two clinical trials involving telomerase inhibitors. One uses a vaccine (GRNVAC1) and the other uses a lipidated drug (GRN163L).
(PDT) is generally a non-invasive treatment using a combination of light and a photosensitive drug, such as 5-ALA, Foscan, Metvix, Tookad, WST09, WST11, Photofrin, or Visudyne. The drug is triggered by light of a specific wavelength.
and coagulation of cellular
protein
s, rapidly killing cells within a tumour.
More prolonged moderate heating to temperatures just a few degrees above normal can cause more subtle changes. A mild heat treatment combined with other stresses can cause cell death by apoptosis
. There are many biochemical consequences to the heat shock response
within in cell, including slowed cell division and increased sensitivity to ionizing radiation therapy
.
There are many techniques by which heat may be delivered. Some of the most common involve the use of focused ultrasound
(FUS or HIFU), microwave
heating, induction heating
, magnetic hyperthermia
, and direct application of heat through the use of heated saline pumped through catheters. Experiments with carbon nanotubes that selectively bind to cancer cells have been performed. Lasers are then used that pass harmlessly through the body, but heat the nanotubes, causing the death of the cancer cells. Similar results have also been achieved with other types of nanoparticles, including gold-coated nanoshells and nanorods that exhibit certain degrees of 'tunability' of the absorption properties of the nanoparticles to the wavelength of light for irradiation. The success of this approach to cancer treatment rests on the existence of an 'optical window' in which biological tissue (i.e., healthy cells) are completely transparent at the wavelength of the laser light, while nanoparticles are highly absorbing at the same wavelength. Such a 'window' exists in the so-called near-infrared region of the electromagnetic spectrum. In this way, the laser light can pass through the system without harming healthy tissue, and only diseased cells, where the nanoparticles reside, get hot and are killed.
Magnetic hyperthermia
makes use of magnetic nanoparticles, which can be injected into tumours and then generate heat when subjected to an alternating magnetic field.
One of the challenges in thermal therapy is delivering the appropriate amount of heat to the correct part of the patient's body. A great deal of current research focuses on precisely positioning heat delivery devices (catheters, microwave, and ultrasound applicators, etc.) using ultrasound or magnetic resonance imaging
, as well as of developing new types of nanoparticles that make them particularly efficient absorbers while offering little or no concerns about toxicity to the circulation system. Clinicians also hope to use advanced imaging techniques to monitor heat treatments in real time—heat-induced changes in tissue
are sometimes perceptible using these imaging instruments.
s are the most likely candidate. Promising preclinical trials have been conducted, although clinical trials may not be held for another few years.
(CAM) treatments are the diverse group of medical and healthcare systems, practices, and products that are not part of conventional medicine and have not been shown to be effective. Complementary medicine usually refers to methods and substances used along with conventional medicine, while alternative medicine refers to compounds used instead of conventional medicine. CAM use is common among people with cancer.
Most complementary and alternative medicines for cancer have not been rigorously studied or tested. Some alternative treatments that have been proven ineffective continue to be marketed and promoted.
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
(see also tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
) by improving on, supplementing or replacing conventional methods (surgery
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
, chemotherapy
Chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
, radiation
Radiation therapy
Radiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...
, and immunotherapy
Immunotherapy
Immunotherapy is a medical term defined as the "treatment of disease by inducing, enhancing, or suppressing an immune response". Immunotherapies designed to elicit or amplify an immune response are classified as activation immunotherapies. While immunotherapies that reduce or suppress are...
).
The entries listed below vary between theoretical therapies to unproven controversial therapies. Many of these treatments are alleged to help against only specific forms of cancer. It is not a list of treatments widely available at hospitals.
Studying treatments for cancer
The twin goals of research are to determine whether the treatment actually works (called efficacyEfficacy
Efficacy is the capacity to produce an effect. It has different specific meanings in different fields. In medicine, it is the ability of an intervention or drug to reproduce a desired effect in expert hands and under ideal circumstances.- Healthcare :...
) and whether it is sufficiently safe. Regulatory processes attempt to balance the potential benefits with the potential harms, so that people given the treatment are more likely to benefit from it than to be harmed by it.
Medical research for cancer begins much like research for any disease. In organized studies of new treatments for cancer, the pre-clinical development
Pre-clinical development
In drug development, pre-clinical development is a stage of research that begins before clinical trials can begin, and during which important feasibility, iterative testing and drug safety data is collected....
of drugs, devices, and techniques begins in laboratories, either with isolated cells or in small animals, most commonly rats or mice. In other cases, the proposed treatment for cancer is already in use for some other medical condition, in which case more is known about its safety and potential efficacy.
Clinical trial
Clinical trial
Clinical trials are a set of procedures in medical research and drug development that are conducted to allow safety and efficacy data to be collected for health interventions...
s are the study of treatments in humans. The first-in-human tests of a potential treatment are called Phase I studies. Early clinical trials typically enroll a very small number of patients, and the purpose is to identify major safety issues and the maximum tolerated dose
Maximum tolerated dose
Maximum tolerated dose refers to the highest dose of a radiological or pharmacological treatment that will produce the desired effect without unacceptable toxicity...
, which is the highest dose that does not produce serious or fatal adverse effect
Adverse effect
In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...
s. The dose given in these trials may be far too small to produce any useful effect. In most research, these early trials may involve healthy people, but cancer studies normally enroll only people with relatively severe forms of the disease in this stage of testing. On average, 95% of the participants in these early trials receive no benefit, but all are exposed to the risk of adverse effects. Most participants show signs of optimism bias
Optimism bias
Optimism bias is the demonstrated systematic tendency for people to be overly optimistic about the outcome of planned actions. This includes over-estimating the likelihood of positive events and under-estimating the likelihood of negative events. Along with the illusion of control and illusory...
(the irrational belief that they will beat the odds).
Later studies, called Phase II and Phase III studies, enroll more people, and the goal is to determine whether the treatment actually works. Phase III studies are frequently randomized controlled trial
Randomized controlled trial
A randomized controlled trial is a type of scientific experiment - a form of clinical trial - most commonly used in testing the safety and efficacy or effectiveness of healthcare services or health technologies A randomized controlled trial (RCT) is a type of scientific experiment - a form of...
s, with the experimental treatment being compared to the current best available treatment rather than to a placebo
Placebo
A placebo is a simulated or otherwise medically ineffectual treatment for a disease or other medical condition intended to deceive the recipient...
. In some cases, the Phase III trial provides the best available treatment to all participants, in addition to some of the patients receiving the experimental treatment.
Bacterial treatments
ChemotherapeuticChemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....
drugs
Medication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
have a hard time penetrating tumors to kill them at their core because these cells may lack a good blood supply. Researchers have been using anaerobic bacteria, such as Clostridium novyi
Clostridium novyi
Clostridium novyi a Gram-positive, endospore- forming, obligate anaerobic bacteria of the class clostridia. It is ubiquitous, being found in the soil and faeces. It is pathogenic, causing a wide variety of diseases in man and animals. It comes in three types, labelled A, B, and a non-pathogenic...
, to consume the interior of oxygen-poor tumours. These should then die when they come in contact with the tumour's oxygenated sides, meaning they would be harmless to the rest of the body. A major problem has been that bacteria do not consume all parts of the malignant tissue. However combining the therapy with chemotheraputic treatments can help to solve this problem.
Another strategy is to use anaerobic bacteria that have been transformed with an enzyme that can convert a non-toxic prodrug
Prodrug
A prodrug is a pharmacological substance administered in an inactive form. Once administered, the prodrug is metabolised in vivo into an active metabolite, a process termed bioactivation. The rationale behind the use of a prodrug is generally for absorption, distribution, metabolism, and...
into a toxic drug. With the proliferation of the bacteria in the necrotic
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
and hypoxic
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
areas of the tumour, the enzyme is expressed solely in the tumour. Thus, a systemically applied prodrug is metabolised to the toxic drug only in the tumour. This has been demonstrated to be effective with the nonpathogenic anaerobe Clostridium sporogenes
Clostridium sporogenes
Clostridium sporogenes is the name given to strains of Clostridium botulinum that do not produce botulinum neurotoxins. Like other strains of C. botulinum, it is an anaerobic Gram-positive, rod-shaped bacterium that produces oval, subterminal endospores and is commonly found in soil...
.
HAMLET (human alpha-lactalbumin made lethal to tumor cells)
HAMLET (human alpha-lactalbumin made lethal to tumor cells) is a molecular complex derived from human breast milkBreast milk
Breast milk, more specifically human milk, is the milk produced by the breasts of a human female for her infant offspring...
that kills tumor cells by a process resembling programmed cell death (apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
). It has been tested in humans with skin papilloma
Papilloma
Papilloma refers to a benign epithelial tumor growing exophytically in finger-like fronds. In this context papilla refers to the projection created by the tumor, not a tumor on an already existing papilla . When used without context, it frequently refers to infections caused by human...
s and bladder cancer
Bladder cancer
Bladder cancer is any of several types of malignant growths of the urinary bladder. It is a disease in which abnormal cells multiply without control in the bladder. The bladder is a hollow, muscular organ that stores urine; it is located in the pelvis...
.
Dichloroacetate
Dichloroacetate (DCA) has been found to shrink tumors in vitro in rats, and has a plausible scientific mechanism: DCA appears to reactivate suppressed mitochondria in some types of oxygen-starved tumor cells, and thus promotes apoptosisApoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
. Because it was tested for other conditions, DCA is known to be relatively safe, available, and inexpensive, and it can be taken by mouth as a pill, which is convenient. Early animal studies received attention in the media, and some doctors began controversially using the chemical off-label. , no patients had been treated with DCA in a clinical trial, and so its actual effectiveness is unknown.
Quercetin
In vitro, quercetinQuercetin
Quercetin , a flavonol, is a plant-derived flavonoid found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.-Occurrence:...
shows some antitumor activity. Cultured skin and prostate cancer cells showed significant mortality (compared to nonmalignant cells) when treated with a combination of quercetin and ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
Note that ultrasound also promotes topical
Topical
In medicine, a topical medication is applied to body surfaces such as the skin or mucous membranes such as the vagina, anus, throat, eyes and ears.Many topical medications are epicutaneous, meaning that they are applied directly to the skin...
absorption by up to 1,000 times, making the use of topical quercetin and ultrasound wands an interesting proposition.
High dietary intake of fruits and vegetables is associated with reduction in cancer, and some scientists suspect quercetin may be partly responsible. Research shows that quercetin influences cellular mechanisms in vitro and in animal studies, and there is limited evidence from human population studies that quercetin may reduce the risk of lung cancer.
Insulin potentiation therapy
In insulin potentiation therapyInsulin potentiation therapy
Insulin potentiation therapy is an alternative cancer treatment using insulin and low-dose chemotherapy.The therapeutic approach is said to take advantage of the endogenous molecular biology of cancer cells, specifically the secretion of insulin and insulin-like growth factor, and the interaction...
(IPT), insulin
Insulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
is a controversial supplement to low-dose chemotherapy. Its proponents claim insulin therapy increases the uptake of chemotherapeutic drugs by malignant cells, permitting the use of lower total drug doses and reducing side-effects.
The first clinical trial, involving 30 women with breast cancer
Breast cancer
Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...
, combined insulin with low-dose methotrexate
Methotrexate
Methotrexate , abbreviated MTX and formerly known as amethopterin, is an antimetabolite and antifolate drug. It is used in treatment of cancer, autoimmune diseases, ectopic pregnancy, and for the induction of medical abortions. It acts by inhibiting the metabolism of folic acid. Methotrexate...
(a common chemotherapy drug) resulted in greatly increased stable disease, and much reduced progressive disease, compared with insulin or low-dose methotrexate alone.
Drugs that restore p53 activity
Several drug therapies are being developed based on p53P53
p53 , is a tumor suppressor protein that in humans is encoded by the TP53 gene. p53 is crucial in multicellular organisms, where it regulates the cell cycle and, thus, functions as a tumor suppressor that is involved in preventing cancer...
, the tumour suppressor gene that protects the cell in response to damage and stress. It is analogous to deciding what to do with a damaged car: p53 brings everything to a halt, and then decides whether to fix the cell or, if the cell is beyond repair, to destroy the cell. This protective function of p53 is disabled in most cancer cells, allowing them to multiply without check. Restoration of p53 activity in tumours (where possible) has been shown to inhibit tumour growth and can even shrink the tumour.
As p53 protein levels are usually kept low, one could block its degradation and allow large amounts of p53 to accumulate, thus stimulating p53 activity and its antitumour effects. Drugs that utilize this mechanism include nutlin
Nutlin
Nutlins are cis-imidazoline analogs which inhibit the interaction between mdm2 and tumour suppressor p53, and were discovered by screening a chemical library by Vassilev et al. Nutlin-1, Nutlin-2 and Nutlin-3 were all identified in the same screen, however Nutlin-3 is the compound most commonly...
and MI-219, which are both in phase I clinical trials. There are also other drugs that are still in the preclinical stage of testing, such as RITA and MITA.
BI811283
BI811283BI811283
BI 811283 is a small molecule inhibitor of the Aurora B kinase protein being developed by Boehringer Ingelheim for use as an anti-cancer agent. BI 811283 is currently in the early stages of clinical development and is undergoing first in human trials in patients with solid tumors and Acute Myeloid...
is a small molecule
Small molecule
In the fields of pharmacology and biochemistry, a small molecule is a low molecular weight organic compound which is by definition not a polymer...
inhibitor
Inhibitor
Something that restrains, blocks, or suppresses.Inhibitor or inhibition may refer to:* Corrosion inhibitor, a substance that decreases the rate of metal oxidation...
of the Aurora B kinase
Aurora B kinase
Aurora B kinase is a protein that functions in the attachment of the mitotic spindle to the centromere.In cancerous cells, over-expression of these enzymes causes unequal distribution of genetic information, creating aneuploid cells, a hallmark of cancer....
protein being developed by Boehringer Ingelheim for use as an anti-cancer agent. BI 811283 is currently in the early stages of clinical development and is undergoing first-in-human trials in patients with solid tumors and Acute Myeloid Leukaemia
Acute myeloid leukemia
Acute myeloid leukemia , also known as acute myelogenous leukemia, is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal white blood cells that accumulate in the bone marrow and interfere with the production of normal blood cells. AML is the most common acute...
.
Gene therapy
Introduction of tumor suppressor geneTumor suppressor gene
A tumor suppressor gene, or anti-oncogene, is a gene that protects a cell from one step on the path to cancer. When this gene is mutated to cause a loss or reduction in its function, the cell can progress to cancer, usually in combination with other genetic changes.-Two-hit hypothesis:Unlike...
s into rapidly dividing cells has been thought to slow down or arrest tumor growth. Adenoviruses
Adenoviridae
Adenoviruses are medium-sized , nonenveloped icosahedral viruses composed of a nucleocapsid and a double-stranded linear DNA genome...
are a commonly utilized vector for this purpose. Much research has focused on the use of adenoviruses that cannot reproduce, or reproduce only to a limited extent, within the patient to ensure safety via the avoidance of cytolytic
Lytic cycle
The lytic cycle is one of the two cycles of viral reproduction, the other being the lysogenic cycle. The lytic cycle is typically considered the main method of viral replication, since it results in the destruction of the infected cell...
destruction of noncancerous cells infected with the vector. However, new studies focus on adenoviruses that can be permitted to reproduce, and destroy cancerous cells in the process, since the adenoviruses' ability to infect normal cells is substantially impaired, potentially resulting in a far more effective treatment.
Another use of gene therapy is the introduction of enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s into these cells that make them susceptible to particular chemotherapy agents; studies with introducing thymidine kinase
Thymidine kinase
Thymidine kinase is an enzyme, a phosphotransferase : 2'-deoxythymidine kinase, ATP-thymidine 5'-phosphotransferase, . It can be found in most living cells. It is present in two forms in mammalian cells, TK1 and TK2...
in glioma
Glioma
A glioma is a type of tumor that starts in the brain or spine. It is called a glioma because it arises from glial cells. The most common site of gliomas is the brain.-By type of cell:...
s, making them susceptible to aciclovir
Aciclovir
Aciclovir or acyclovir , chemical name acycloguanosine, abbreviated as ACV,is a guanosine analogue antiviral drug, marketed under trade names such as Cyclovir, Herpex, Acivir, Acivirax, Zovirax, and Zovir...
, are in their experimental stage.
Telomerase therapy
Because most malignant cells rely on the activity of the protein telomeraseTelomerase
Telomerase is an enzyme that adds DNA sequence repeats to the 3' end of DNA strands in the telomere regions, which are found at the ends of eukaryotic chromosomes. This region of repeated nucleotide called telomeres contains non-coding DNA material and prevents constant loss of important DNA from...
for their immortality, it has been proposed that a drug that inactivates telomerase might be effective against a broad spectrum of malignancies. At the same time, most healthy tissues in the body express little if any telomerase, and would function normally in its absence. Currently, Inositol hexaphosphate, which is available over-the-counter, is undergoing testing in cancer research due to its telomerase-inhibiting abilities.
A number of research groups have experimented with the use of telomerase inhibitors in animal model
Animal model
An animal model is a living, non-human animal used during the research and investigation of human disease, for the purpose of better understanding the disease without the added risk of causing harm to an actual human being during the process...
s, and as of 2005 and 2006 phase I and II human clinical trials
Clinical trial
Clinical trials are a set of procedures in medical research and drug development that are conducted to allow safety and efficacy data to be collected for health interventions...
are underway. Geron Corporation, is currently conducting two clinical trials involving telomerase inhibitors. One uses a vaccine (GRNVAC1) and the other uses a lipidated drug (GRN163L).
Photodynamic therapy
Photodynamic therapyPhotodynamic therapy
Photodynamic therapy is used clinically to treat a wide range of medical conditions, including malignant cancers, and is recognised as a treatment strategy which is both minimally invasive and minimally toxic...
(PDT) is generally a non-invasive treatment using a combination of light and a photosensitive drug, such as 5-ALA, Foscan, Metvix, Tookad, WST09, WST11, Photofrin, or Visudyne. The drug is triggered by light of a specific wavelength.
Hyperthermia therapy
Localized and whole-body application of heat has been proposed as a technique for the treatment of malignant tumours. Intense heating will cause denaturationDenaturation (biochemistry)
Denaturation is a process in which proteins or nucleic acids lose their tertiary structure and secondary structure by application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent , or heat...
and coagulation of cellular
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s, rapidly killing cells within a tumour.
More prolonged moderate heating to temperatures just a few degrees above normal can cause more subtle changes. A mild heat treatment combined with other stresses can cause cell death by apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
. There are many biochemical consequences to the heat shock response
Heat shock protein
Heat shock proteins are a class of functionally related proteins involved in the folding and unfolding of other proteins. Their expression is increased when cells are exposed to elevated temperatures or other stress. This increase in expression is transcriptionally regulated...
within in cell, including slowed cell division and increased sensitivity to ionizing radiation therapy
Radiation therapy
Radiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...
.
There are many techniques by which heat may be delivered. Some of the most common involve the use of focused ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
(FUS or HIFU), microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
heating, induction heating
Induction heating
Induction heating is the process of heating an electrically conducting object by electromagnetic induction, where eddy currents are generated within the metal and resistance leads to Joule heating of the metal...
, magnetic hyperthermia
Magnetic hyperthermia
Magnetic hyperthermia is the name given to an experimental cancer treatment. It is based on the fact that magnetic nanoparticles, when subjected to an alternating magnetic field, produce heat...
, and direct application of heat through the use of heated saline pumped through catheters. Experiments with carbon nanotubes that selectively bind to cancer cells have been performed. Lasers are then used that pass harmlessly through the body, but heat the nanotubes, causing the death of the cancer cells. Similar results have also been achieved with other types of nanoparticles, including gold-coated nanoshells and nanorods that exhibit certain degrees of 'tunability' of the absorption properties of the nanoparticles to the wavelength of light for irradiation. The success of this approach to cancer treatment rests on the existence of an 'optical window' in which biological tissue (i.e., healthy cells) are completely transparent at the wavelength of the laser light, while nanoparticles are highly absorbing at the same wavelength. Such a 'window' exists in the so-called near-infrared region of the electromagnetic spectrum. In this way, the laser light can pass through the system without harming healthy tissue, and only diseased cells, where the nanoparticles reside, get hot and are killed.
Magnetic hyperthermia
Magnetic hyperthermia
Magnetic hyperthermia is the name given to an experimental cancer treatment. It is based on the fact that magnetic nanoparticles, when subjected to an alternating magnetic field, produce heat...
makes use of magnetic nanoparticles, which can be injected into tumours and then generate heat when subjected to an alternating magnetic field.
One of the challenges in thermal therapy is delivering the appropriate amount of heat to the correct part of the patient's body. A great deal of current research focuses on precisely positioning heat delivery devices (catheters, microwave, and ultrasound applicators, etc.) using ultrasound or magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
, as well as of developing new types of nanoparticles that make them particularly efficient absorbers while offering little or no concerns about toxicity to the circulation system. Clinicians also hope to use advanced imaging techniques to monitor heat treatments in real time—heat-induced changes in tissue
Biological tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
are sometimes perceptible using these imaging instruments.
Non-invasive RF cancer treatment
This preclinical treatment involves using radio waves to heat up tiny metals that are implanted in cancerous tissue. Gold nanoparticles or carbon nanotubeCarbon nanotube
Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material...
s are the most likely candidate. Promising preclinical trials have been conducted, although clinical trials may not be held for another few years.
Complementary and alternative treatments
Complementary and alternative medicineAlternative medicine
Alternative medicine is any healing practice, "that does not fall within the realm of conventional medicine." It is based on historical or cultural traditions, rather than on scientific evidence....
(CAM) treatments are the diverse group of medical and healthcare systems, practices, and products that are not part of conventional medicine and have not been shown to be effective. Complementary medicine usually refers to methods and substances used along with conventional medicine, while alternative medicine refers to compounds used instead of conventional medicine. CAM use is common among people with cancer.
Most complementary and alternative medicines for cancer have not been rigorously studied or tested. Some alternative treatments that have been proven ineffective continue to be marketed and promoted.