Minor Thoughts from me to you

James Byrne wrote about new developments in cancer treatment for Scientific American. Researchers are looking at ways to use bacteria to kill cancerous tumours, without making you sick the way chemotherapy and radiation do.

The usefulness of bacteria is limited to certain types of cancer as the requirement for this therapy to be useful is tumours large enough to be dead in the middle.

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Large tumours with dead or necrotic nodes (necrosis can develop as one large deposit or multiple small foci in the centre of the tumourous tissue) are very common and in many cases act as a marker of the primary tumour where metastases are observed. This makes them very interesting target locations for therapeutics even though direct treatment of the necrosis itself has not been shown to aid recovery.

The current limitations with traditional treatments are reasonable well known and this stems largely from the nature if these therapies. Chemotherapy and radiotherapy are designed to kill all fast growing cells including cancerous cells but other cells grow quickly too leading to hair loss, depletion of the immune system, fatigue and fertility problems. It's the inability to target the therapy that results in much tissue damage associated with treatment. So naturally its been suggested that if a there were a way to target chemo- or radio- therapy these treatments would sho significantly less toxicity. But how do you target tumours alone?

It is here that bacteria can prove their worth. Bacterial species such as Clostridia, Listeria monocytogenes and Salmonella cannot grow well or in some cases at all in the presence of oxygen and so find it very difficult to grow in most locations of the body unless its necrotic.

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Despite the positive activity observed over the last 20 years in particular a purely bacterial therapy for cancer treatment will not be the full answer to cancer. The real promise lies in combination therapies that place bacterial approaches alongside traditional approaches.

Under extensive research now is the possibility of altering Clostridial species the express pro-drug converting enzymes such as Cytosine Deaminase (CD) or Thymidine Kinase (TK). CD converts the non-toxic 5-Flurocytosine into the cytotoxic 5-Flurouracil and TK phosphorylates the non-toxic Ganciclovir converting it into the active toxic compound. Ordinarily chemotherapeutic agents are administered intravenously and allowed to spread throughout the entire body before eliciting their effects on the quickly reproducing cells of the body. By including the pro-drug converting enzymes within the Clostridia the non-toxic pro-drug can be administered in higher concentrations, as the toxic form will only be present where the bacteria are expressing the enzymes required for its conversion.

I'll freely admit that I only understand about 50% of this article. Here's what it sounds like to me. Bacteria grow best in the dead cancer cells. Researchers will put chemotherapy drugs inside of the bacteria. The bacteria will travel through the body, looking for the dead cancer cells where they can grow and survive. Once the bacteria start reproducing, they'll release the chemotherapy drugs, which will attack the living cancer cells. Between the bacteria attacking the dead cells and the chemotherapy attacking the living cancer cells (and only cancer cells), the combination drug will knock out the tumour without knocking out the rest of your body.

I think the whole article is definitely worth a read through. (If nothing else, you can check my understanding of it.) This is the kind of medical research that really excites me. I really hope researchers are successful in targeting cancers this way.

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