Despite the advances in treatment and detection, cancer has remained a major health problem and one of the leading causes of death worldwide. Cancer Research UK suggests that 2018 has seen 17 million new cases of cancer worldwide, with 9.6 million death as a result of cancer.
The cancer research and awareness charity also estimate that there will be 27.5 million new cases of cancer worldwide each year by 2040. So it comes as no surprise that cancer is one of the most intensely studied biomedical conditions in the modern era and there are many streams of research. To mark breast cancer awareness month, we take a look at the role of bacteria in the treatment of cancer.
Bacteria mediated tumor therapy (BMTT)
Whilst the idea of using bacteria in cancer treatment is not new, the actual implementation of bacterial therapy has not been feasible due to many obstacles including infections and other adverse side effects. State-of-the-art genetic engineering has been recently applied to bacterial therapy and resulted in greater efficacy and a reduction of side effects. An adequate balance between the control of infection and the therapeutic benefit of bacteria is an essential requirement for a successful Bacteria Mediated Tumour Therapy (BMTT).
Different species of bacteria demonstrate the ability to invade and colonise solid tumours, and to destroy tumour cells. Recently, a number of studies have found that genetically modified bacteria prefer to replicate and accumulate within tumours rather than normal tissues. These studies successfully used Salmonella and Clostridium spp. bacteria as delivery vectors to selectively colonise mice tumours without a severe immune response or toxic side effects.
Bacteria create anti-tumour environments through the depletion of nutrients required for cancer cell metabolism. Apart from their direct effect on targeting cancer cells, tumour-targeting bacteria can also be used as carriers for cancer therapeutic agents in cancer treatments.
While bacteria alone may not demonstrate fully therapeutic potential, their combination with other more conventional therapies, such as chemotherapy and radiotherapy, will improve their potential for cancer treatment.
Chemotherapy is the main treatment for inoperable cancer, but it comes with numerous shortcomings like drug resistance or systemic toxicity. In addition, the remaining tumour cells after therapy usually show increased aggressiveness and probability of metastasis. Therefore, combining chemotherapy with bacteriotherapy could be the novel approach needed to increase effectiveness and reduce the toxicity of chemotherapy alone. This is due to the hypoxic areas of tumours being frequently the most resistant to chemotherapy, but they can be specifically targeted by bacteria.
Although the use of bacteria in cancer therapy has been a double-edged sword over the years, the fairly recent identification of attenuated species of bacteria capable of treating cancer has made them safe for cancer therapeutic application with little or no side effects. Despite the encouraging results, the use of bacteria in anti-cancer therapy is still fairly new and requires further studies to scrutinise its clinical significance.