The Methods and Effects of Gene Therapy Concerning Cancer indsay Adams Abstract It has been proposed that gene therapy could yield to future treatment of cancers and other diseases and genetic disorders. Various literature sites have expressed that gene therapy is currently only used in research studies, and is still very young and unpredictable in clinical studies. Gene therapy has become more and more applicable to current and future medical studies concerning the treatment of cancer.
The reviewed literature has shown that researchers and scientists firmly believe in the promise of gene therapy, and hat it could indeed hold the cures for many diseases and the tools to prevent them. The reviewed literature has revealed that gene therapy has been very successful in many experimental trials with animals and models, but is not yet ready for human clinical trials because of the unpredictability of side effects and problems that have occurred in early studies. In the future, the literature has suggested the possible development of a cancer vaccine in addition to individualized chemotherapy and gene targeting in patients.
It is the hopes of all that gene therapeutic methods will be used in the future to treat cancer nd further its predictability and prevention. Literature Review Genes, or the specific order of nucleotides on a segment of DNA that encode the instructions for making proteins, are the basic operative units of heredity (Peault et al. 2007). Throughout the recent years of genomics through the Human Genome Project, researchers have identified all of the genes in the human genome. Located on the chromosomes, genes are the keys to revealing the genotypes and phenotypes of all living things.
When they are mutated, inactive, or altered, the encoded proteins cannot continue ith their conventional functions, and genetic disorders are often developed (Peault et al. 2007). Current research is underway to determine the functions of these genes. Once researchers and scientists understand the functions of the genes in the human genome, they can hope to understand the relationship between genes and disease. Through further research, researchers believe they will discover the key for correction, treatment, and even prevention Of disease and disorder that mutations in the genome can cause (Peault et al. 007). Gene therapy is an experimental technique that nvolves correcting defective or mutated genes to treat or prevent disease (Alto 2008). Through genetic engineering, Recombinant DNA Tech nology allows for researchers to alter the genetic structure of viruses to transform them into harmless plasmids for gene therapy. It is researchers’ hope that in the future, gene therapy may allow the treatment of cancer or another disorder by inserting a gene into a patients somatic cells without the use of surgery or drugs (Alto 2008).
Although gene therapy is a fairly new technique, researchers have already developed several methods of correcting the efective genes. The most common approach involves inserting a normal, functional gene into an unspecified location within the genome to “overrule” a nonfunctional gene. In another, less common approach, a functional gene may be inserted to replace a nonfunctional gene via homologous recombination. A third method involves repairing an abnormal or nonfunctional gene by way of selective reverse mutation, ultimately returning the gene to its expected function.
A fourth and final method of gene therapy involves altering a specific gene by either activating, or deactivating it (Peault et al. 007). In a vast majority of studies regarding gene therapy, a functional gene is inserted into a genome to replace a nonfunctional, or abnormal gene that causes disease. A vector, or carrier molecule, is used to introduce the new, therapeutic gene into the patient’s genome. Typically, the vector used most often is a genetically altered virus that can sustain human DNA.
Common gene therapy vectors include retroviruses, adenoviruses, adeno- associated viruses, and Herpes simplex viruses to infect the target cells (typically liver cells or lung cells). The vector containing the gene of interest an either be given intravenously (with the use of an IV) into the target cells, or exposed to a sample of the patient’s cells that have been removed in a laboratory-type setting. If the latter method is used, only the cells that have taken up the vector will be returned to the patient. If the treatment is a success, the new gene transported fabricates a properly functioning protein (Alto 2008).
In addition to viral vectors, several non-viral options for gene delivery are being tested. These methods include direct induction of therapeutic DNA into target cells, the creation of artificial liposomes, chemical inking of DNA to a molecule with specific cell receptors, and even the introduction of a 47th chromosome into target cells. Through further research and experimentation, researchers aspire to eliminate cancer cells and tumors with gene therapy. Cancer cells differ from normal cells only slightly.
While cancer cells and normal cells have the same set of genes, cancer cells can grow rapidly and indefinitely due to the over expressed BcI-2 proto-oncogene, a normal gene that can be mutated to form a gene that causes a cell to be malignant (Kosinski 2008). Current research is taking place o introduce genes to cancer cells that will induce a type of “cell suicide” called apoptosis, or programmed cell death. The gene used by researchers the majority of the time is one that produces p53, a protein that binds to DNA to stop cell division in cells with mutated DNA and to repair mutated DNA.
The p53 plays an important role in keeping the cell cycle in check. If any DNA in a cell is damaged, it is the responsibility of p53 to either pause the cycle and repair the problem, or to induce apoptosis when damage becomes too prevalent. However, if p53 becomes deactivated or mutated, DNA cannot be hecked or repaired and tumors may develop (Kosinski 2008). Several cancer gene therapy techniques focus on adding the p53 gene into cancer cells to trigger apoptosis and stop them from replicating further (Lu et al. 008) . Chemotherapy for cancer treatment deploys its deadly effect in cancer cells by means of triggering apoptosis with a functional pS3 gene. However, over fifty percent of tumors’ p53 gene is either absent or malfunctioned, yielding their resistance to anti-cancer therapy. However, a recently discovered protein, Apoptin–, derived from the chicken anemia virus (CAV), will provoke poptosis in cultured (human) cells acquired from miscellaneous tumors such as those that occur in the lung, colon, and breast.
Cancer cells that do not have the p53 gene can receive Apoptin-induced apoptosis, which is not inhibited by any downstream p53-pathway inhibitors. Conveniently, Apoptin fails to set-off apoptosis in dermal, epidermal, lymphoid, endothelial, and smooth muscle cells in humans. This surprising fact renders Apoptin to potentially be an antitumor perpetrator, since it induces programmed cell death in malignant cells and not in normal diploid benign cells. Further trategies concerning the Apoptin-based viral vectors in gene therapy are underway (Noteborn et al 1994).
Of all cancer types, lung cancer holds the number one rank in cancer-related death in the developed world. Therefore, gene-therapy strategies are highly desired. Gene therapy holds an experimental advantage over present treatment methods. Due to further apprehension into the molecular biology of cancer cells, researchers have identified and determined the regulatory gene pattern used to discriminately activate the p53 gene specifically in cancer cells and initiate apoptosis.
Many further improvements are necessary, but promise for future gene therapy In the clinical atmosphere is shown resulting from recent encouraging results in the lab (Cancer Info. Group 2005). Future Directions As Lu et al. 2008’s research indicates, the human gene, hpHyde, has successfully been cloned and its genomic location has been accurately identified on the human chromosome. Lu et al. believe that there is a potential use of pHyde for prostate cancer gene therapy in future treatments accompanied with chemotherapy.
In addition, cancer vaccines are becoming promising tactic to treating tumors or preventing tumor relapse in cancer patients. In Elia et al. ‘s experiments, he tested this through the introduction Of an immune response against TAAs (tumor-associated antigens) His results indicated that the combined CD25+ gene deactivation along with genetic vaccination yielded remarkable tumor protection in a metastatic tumor model, su pporting the future possibility of this cancer vaccine strategy as a type of therapy to put an end to tumor relapse in cancer patients (Elia et al. 007). Furthermore, stage Ill colorectal cancer patients’ inferior prognosis to hose in other stages. In such patients, the ability to predict development of recurrence would further guide intensive follow-up treatments and additional chemotherapy. The results of Wantanabe et al. current study corroborated that gene expression outlining is useful in anticipating recurrence in stage Ill colorectal cancer. The authors identified CABINI gene amid discerning genes that could render a key part in the development of recurrence.
These results could assist in the establishment of future, individualized therapy for stage Ill colorectal cancer patients (Wantanabe et al. 2008). Although the research and rogress of gene therapy has many positive results and promises for the future, it has not proven to be very successful in clinical environments and trials. The FDA (Food and Drug Administration) has yet to approve any human gene therapy product to be sold. In fact, according to Peault et al. , very little progress has been made since the very first clinical trial of gene therapy began in 1990.
The idea and practice of gene therapy in clinical studies suffered greatly when 18-year-old Jesse Gelsinger died of multiple organ failures just four days after beginning his gene therapy treatment. He was ndergoing a gene therapy trial in the hope of treating his OTCD (ornithine transcarvoxylase deficiency, and his death was thought to be a result of a severe immune response to the adenovirus vector (Peault et al. 2007). Despite the researchers’ and doctors’ good intentions and high hopes for treating Jesse the way they did, they proved to be unsuccessful.
Because the case occurred in the late 90’s, the researchers did not yet have the knowledge that they possess now and in the future (Donegan 1995). Instead of injecting the vector with the gene Of interest directly into his target cells, future clinical rials would benefit from extracting target cells from the patient, injecting the vector with the gene of interest into the cells in a laboratory, and if the cells react the way they should and no problems arise, return the functional cells back to the patient’s body.
Right now, gene therapy is only available in a research environment, as the FDA has yet to approve it in clinical studies. Nonetheless, gene therapy is currently undergoing rigorous studies and testing to determine whether or not it can ever be possible to be used in the future to treat and prevent cancers as well as other diseases and disorders. Researchers are presently evaluating and determining the safety of gene therapy, because several studies, such as Jesse’s case, have demonstrated that gene therapy can have serious health risks, and many are unpredictable because the techniques are so new.
Various institutions such as the National Institutes of Health (NIB), the F-DA, and an Institutional Review Board (IRB), as well as medical researchers and regulatory agents are working as hard as they can to ensure that gene therapy research is as safe as possible (Peault et al. 2007). Future studies will determine if it could ever be an effective reatment option for cancer patients. Current research teams are focusing on treating individuals by targeting the gene therapy to patients’ somatic cells such as blood cells and bone marrow.
In the future, it is aimed possible that gene therapy could be targeted to germ cells (Alto 2008). This would allow the inserted or modified gene to be passed on to future generations, possibly eliminating hereditary disease forever. However, there are many ethical concerns regarding germ cell gene therapy, and the United States government currently does not permit researchers to se federal funds for research on the issue because of the vast ethical debate concerning it. Therefore, before gene therapy can be used as a practical approach to treat cancer and disease, researchers must overcome many technical and ethical challenges.