by Justin Lee

Created on: February 25, 2009

Fighting Cancer with Bacteria

There are three unique ways that bacteria have been used to help fight cancer: they have been used as probiotics to help prevent cancer, they have been introduced into patients on purpose in order to elicit a fever (heat + immune) response, and (very recently) they have been used as a vehicle for cancer drug delivery.

A. Bacteria as probiotics against cancer

Lactic acid bacteria (LAB) are the most common type of bacteria used as probiotics; they are present in bacteria-treated foods that we eat such as yogurt. The lactic acid bacteria covert the foods' complex sugars into lactic acid, generating the characteristic sour taste of fermented dairy foods.

Several studies have shown that milk fermented by LAB may show beneficial effects for preventing colon cancer and breast cancer (1). Animals studies have shown that lactice acid bacteria can help protect against colon cancer in rodents, and human epidemiological studies have confirmed lower rates of colon cancer in populations who consume higher amounts of fermented dairy products as part of their staple diet.

The mechanism of action for these probiotics reducing cancer risk is not well understood, but several hypotheses exist, including:

1. Probiolotics may exert anti-carcinogenic effects by decreasing the activity pro-cancerous enzymes. For instance, lactic acid bacteria might exert anti-mutagenic effects by binding with (and inactivating) heterocyclic amines (carcinogenic substances formed in cooked meat).

2. Probiotics' lowering of food pH (via lactic acid secretion) reduces the chances of other organisms ("bad bacteria") growing and spoiling food. The corresponding decrease in gastrointestinal infections may also decrease risk of cellular aggravations and tumor development.

3. Probiotics may suppress the growth of bacteria that convert procarcinogens into carcinogens, thereby reducing the amount of carcinogens in the intestine. (e.g., lactic acid bacteria inhibit beta-glucuronidase, an enzyme which generates carcinogens in the digestive system.)

4. Probiotics may protect the detoxification function of the kidney and liver.

5. Probiotics may aid in adaptation to smoke irritation generated during cooking, heating and/or tobacco smoking (possibly by restoring natural killer cell activity which is lowered in smokers). Smoking is the most important lifestyle risk factor for bladder cancer, and epidiomiological evidence shows that consumption of probiotic foods reduces the risk of this specific

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