Bacterial Cure for Cancer - Essay Example

? Bacterial Cure for Cancer 16-09-11 Bacterial Cure for Cancer Introduction: Today, in developing countries cancer is one of the leading causes of death. The incidence of cancer as a cause of death is rapidly increasing. Cancer cells originate due to mutation of a host cell in response to chemical carcinogens, viruses or radiation. Regardless, of their origin most cancerous cells have certain surface antigens which distinguish them from the surrounding normal host cells. These antigens serve as an ideal target for elimination by the defense mechanisms of the body. In accordance with the theory of Immune Surveillance, cytotoxic T cells and Natural killer cells identify these abnormal cells and destroy them before they get a chance to develop into cancer. Therefore, we only develop cancer when our immune cells fail to either recognize or destroy these abnormal cells. Unfortunately, most tumor and cancerous cells show little response to the control mechanisms of the human immune system. One reason why cytotoxic T cells fail to recognize malignant cells is due to the actions mediated by the antigens on these malignant cells (Medicine Net 2011). Breakthrough in Cancer treatment: Dr. Jane They of Maastricht University states that an effective cancer treatment with gene therapy involves three aspects. Firstly, we need to identify and isolate a therapeutic gene which will show tumor regression. Secondly, the anti cancer agent used must be equipped with the ability to differentiate between cancerous and normal host cells. Last but not the least; the employed therapeutic gene must be capable of effectively locating the necrotic areas within the tumor. This is where the bacterial use for cancer treatment comes in i.e. to provide a way to deliver the therapeutic gene to the cancerous cells. (Spreen et al 2009) Over the years scientists have been continuously striving to develop a cure for cancer; from surgery, drugs and chemotherapy. However, scientists have been successful in finding an effective cure for cancer by using an innocuous soil bacterium known as Clostridium. However, the observation that bacteria can be used to target and destroy cancerous cells is not a new one, in fact the idea dates back to almost 150 years. Two German physicians W. Busch and F. Fehleisen observed cancer regression in patients who suffered from accidental erysipelas infections during the time they were hospitalized. Moreover, an American physician William Coley observed that one of his neck cancer patient started showing dramatic recovery after contracting an erysipelas infection. The discovery that bacteria can cause cancer regression motivated Coley and he dedicated his entire life to seek ways to use bacteria in cancer therapy. Unfortunately, no effective bacterial cure for cancer could be discovered which did not cause serious toxicological complications in patients. However, several years later, the interest to use bacteria for the treatment of solid tumors was re sparked. Clinical trials involving Clostridium began in the early 1960s. The pathogenic species of Clostridium are responsible for serious illnesses such as tetanus and botulism. Whereas, most Clostridium species are innocuous that thrive in anaerobic conditions. These anaerobic bacteria form highly resistant spores when exposed to oxygen rich conditions. However, the bacteria cannot grow or multiply within these highly resistant spores. Several experiments in animals revealed that preferential proliferation in necrotic areas of tumor was shown by anaerobic pathogenic species of Clostridium. Although tumor regression was observed in animals treated with clostridium but most of them developed acute toxicity and later died. Therefore, researchers decided to use non pathogenic species strains such as Clostridium M55 for the treatment of tumors. Clostridium M55 and Clostridium sporongenes are non pathogenic species which can only grow in anaerobic surroundings such as deep soils or within the necrotic regions of tumors. Therefore, an intravenous administration of Clostridium M55 showed that the bacteria had the ability to colonize the anaerobic necrotic areas within a tumor. Later this bacterial cancer therapy was progressed to human trials but unfortunately tumor regression was not observed with non pathogenic strains. Therefore, human clinical trials were halted. However, recently researchers discovered that various anaerobic bacterial species such as bifidobacteria, lactobacilli and Clostridium novyi exhibit the ability to concentrate and cause tumor lyses. However, the animals subjected to Clostridium novyi later died. Therefore, genetic engineers were called upon to locate and delete the gene coding the lethal toxin from the genome of Clostridium novyi which was responsible for death of the animals. The experiments involving both classical chemotherapy and attenuated Clostridium novyi showed extraordinary results and attracted immense attention from the media. Unfortunately, attenuated Clostridium novyi had the ability to stimulate a tumor targeted immune response which resulted in inflammation. The inflammation associated with the use of attenuated Clostridium novyi caused the death of animals. To overcome the problem of bacterial toxicity associated with bacterial dose required for effective therapeutic activity, researches diverted their attention to search alternative ways for the use of bacteria as anti cancer agents. Therefore, now Clostridium species are used as ‘magic bullets’ in Bacterially Directed Enzyme Prodrug Therapy (BDEPT). This therapy includes arming the bacteria with specific genes that encode certain enzymes which are capable of converting harmless prodrugs into active drugs which cause cytotoxicity in the tumor. Bacterially Directed Enzyme Prodrug Therapy is carried out in two steps. The first step involves intravenous administration of genetically engineered Clostridium bacteria which has the gene encoding the enzyme, incorporated within its genome. Modified Clostridium locates the tumor and proliferates within the anaerobic necrotic areas and results in therapeutic enzyme expression. Once the expression of the therapeutic enzyme reaches an optimal level, the administration of a harmless prodrug is carried out. Once the prodrug reaches the tumor, the expressed enzymes convert it into the cytotoxic drug. This process ensures tumor cytotoxicity and the chances of systemic toxicity are narrowed down to zilch. Therefore, only the tumor cells are destroyed without harming the surrounding normal tissues. Today, several enzyme prodrug combinations are available but the most effective one is Cytosine deaminase which converts the harmless prodrug known as 5-flurocysteine to the cytotoxic drug known as 5-fluorouracil. These enzyme prodrug systems have been used in vitro experiments with the vector Clostridium sporogenes. The results of such experiments were phenomenal and showed that tumor cells can be effectively destroyed without harming normal tissues (The journal of the American Medical Association. 291, no. 5, (2004): 625). References: Medicine Net. 2011 www.medicinenet.com Spreen, A. N., & Enten, R. (2009). Tomorrow's cancer cures today: 25 secret therapies from around the world. Baltimore, Md: Health Sciences Institute. The journal of the American Medical Association. 291, no. 5, (2004): 625 Read More