BACTERIA TO GRAPPLE CANCER: BACTERIUM MEDIATED CANCER THERAPY (BMCT)

Cancer is characterized by uncontrolled and invasive growth of cells. These cells may spread to other parts of body and this is called metastasis. Cancer may be benign or malignant. The International Agency for Research on Cancer (IARC) estimates that 1 in every 5 people develop cancer during their lifetime. These new estimates suggest that more than 50 million people are living within 5 years of a past cancer diagnosis.

Conventional anticancer therapies consisting of surgical resection, radiotherapy, chemotherapy, are effective in management of many patients, but for about half of cancer sufferers these are ineffective. Resistance to conventional anticancer therapies has prompted the need for novel strategies.

The success of the alternative therapies depends on their cancer selectivity and reduced tissue toxicity. Despite being an  unconventional and contentious  therapy, the last two decades have seen a significant renaissance of bacterium mediated cancer therapy.

Scientists are harnessing a harmless soil bug to kill tumours by using it as a drug delivery vehicle. A bacterium found in the soil and harmful in its natural state has been converted through genetic methods into precise tumour destroyer. Researchers from USA’s John Hopkins Cancer Centre excised the toxin producing gene from the bacterium and the spores of. modified bacterium were introduced directly into the tumours and there was significant reduction in the tumour size or eradication without damaging healthy tissues.

The therapy uses Clostridium sporogenes – a bacterium that is widespread in the soil. Spores of the bacterium are injected into patients and only grow in solid tumours, where a specific bacterial enzyme is produced. An anti-cancer drug is injected separately into the patient in an inactive ‘pro-drug’ form. When the pro-drug reaches the site of the tumour, the bacterial enzyme activates the drug, allowing it to destroy only the cells in its vicinity – the tumour cells.

Bacterial anticancer therapy is an important weapon in the arsenal of fight against cancer. Strength of bacterial therapy depend in its specific targeting to the cancer cells. Different mechanisms responsible for anticancer activity include secretion of cytotoxic agent, immune engagement by the bacteria and engineered bacterial vectors for the expression and release of tumoricidal proteins.

Researchers at the University of Nottingham and the University of Maastricht have introduced a gene for a much-improved version of the enzyme into the C. sporogenes DNA. The improved enzyme can now be produced in far greater quantities in the tumour than previous versions, and is more efficient at converting the pro-drug into its active form.

Professor Nigel Minton, states that “Clostridia are an ancient group of bacteria that evolved on the planet before it had an oxygen-rich atmosphere and so they thrive in low oxygen conditions. When Clostridia spores are injected into a cancer patient, they will only grow in oxygen-depleted environments, i.e. the centre of solid tumours. This is a totally natural phenomenon, which requires no fundamental alterations and is exquisitely specific. We can exploit this specificity to kill tumour cells but leave healthy tissue unscathed,” he said.

The research will ultimately lead to a simple and safe procedure for curing a wide range of solid tumours. A successful outcome could lead to its adoption as a frontline therapy for treating solid tumours. If the approach is successfully combined with more traditional approaches this could increase our chance of winning the battle against cancerous tumours.

 Dona Basil, II^nd  Pharm D