Existing parasites often have an extraordinary ability to navigate through the host's body to specific target organs. Can we tweak nematode worms through genetic engineering (fashionable but easier said than done) or through selective breeding (slow) so that they home in on cancer tumors and then destroy them? Each nematode cultivar would probably be attuned to the chemical signature of a particular kind of cancer. The worms would have to be non-destructive to normal tissue, perhaps circulating through the bloodstream as inactive juveniles (I forget the name for that state but it's not uncommon in these little beasties) and maturing only in the tumor. Some nematode species have both free-living and parasitic forms, and if we used one of these we could culture them in labs easily--we wouldn't need to mess about with intermediate hosts. (I believe this is an advantage over most trematodes, or flukes; also, the activities of liver flukes and possibly other varieties of fluke seem to trigger some forms of cancer, which is obviously counterproductive.)

The main advantage of nematodes over similarly modified bacteria or viruses? I suspect that the worms, being multicellular and relatively complex, would be less likely to mutate into viable pathogenic forms. Their life cycle also allows better control of the infestation, I think, and therefore less risk of runaway infection.
-- Dog Ed, Apr 21 2001

(?) The Guinea Worm http://www.carterce...org/guineaworm.html
One year life cycle--requires reinfestation. [That should keep the UR folks at our HMOs happy] [reensure, Apr 21 2001]

Phage Therapy Review http://www.evergree...py/webaddition.html
I'm not a biomedical researcher, but I play one on the web. [Uncle Nutsy, Apr 21 2001, last modified Oct 05 2004]

BBC News: "Handheld scanner 'detects cancer'" http://news.bbc.co..../health/2982442.stm
"Simply passing a handheld device over the body of a suspected cancer patient could reveal a tumour, inventors have claimed ... " [(), Oct 04 2004, last modified Oct 05 2004]

Herpes used to treat brain tumors http://www.ncbi.nlm...76132&dopt=Abstract
[mystic2311, Oct 04 2004, last modified Oct 05 2004]

Bakable or not, your heart is in right place.
-- thumbwax, Apr 21 2001


I just don't know. It seems so unappealing than patients might elect it only as a last resort, at which point the treatment would be much less likely to work. That aside, however, won't the worms grow as they attack the cancer? I'm not exactly clear on whether they eat the diseased cells or what.
-- centauri, Apr 21 2001


egnor: S_Bug = Silly Buggers. A high S_Bug number means that Peter can stop reading right there if he's not in the mood for silliness.

centauri: Yeah, pretty uappealing treatment, but most cancer therapies are pretty unpleasant. (Much less horrible than they were 15 years ago, though.)

No, the worms don't grow indefinitely. Some varieties of nematode are microscopic, and stay that way no matter how many donuts and bags of chips they eat.

I envision the worms feeding on tumor cells, preferentially next to blood vessels. Formation of scar tissue gradually narrows the blood vessels feeding the tumor and starves it. The worms clean up any stray cells.
-- Dog Ed, Apr 21 2001


The idea has merit, but I'm not thinking blood borne delivery, the way schistosomes behave. Since most cancers develop rather slowly and insideously prior to being detected, and they normally don't show up exactly where they are expected, use a parasite whose behavior mimics the cancer.

I'd recommend the Guinea Worm, since it has outlived its eradication programs timetable by five years. [see link--]

Of course I'm not really that nasty, but I do think that genetic engineering can provide us with specific insertion genes for cancer therapy that do not involve the creation of symbiotic parasites.
-- reensure, Apr 21 2001


Scientists are looking into something like this, but the interest is on a smaller scale. Phages, viruses that attack bacteria, show some real promise in treating bacterial infections, while something called "phage display" can help with the early detection if not treatment of viral infections. Cancer cells present a much more difficult problem, though I am not qualified to explain why.

However, some cancers are linked with viruses and bacteria. HPV, the human papillomavirus, is a major risk factor for cervical cancer, while the bacterium heliobacter pylori is associated with gastric cancer. Phage treatments can be used to head off possible cancers in such cases.
-- Uncle Nutsy, Apr 22 2001


reensure: I suspect you're right about genetics, and I believe viruses are front-runners for a delivery system. But I found it interesting to think of myself as a walking (or sort of shambling) ecosystem. Considering all the symbiotic, parasitic, and commensal organisms on my skin and hair, under my toenails, and in my gut and mouth, maybe an ecological point of view would yield some insights if pursued far enough. Look at the human animal as the scaffolding for a (mostly microbial) food web, and perhaps tweaking the predator-prey balance by introducing artificial species might someday be a standard treatment for certain diseases. Whattya think?
-- Dog Ed, Apr 23 2001


If cancer and virus are linked together or similar in many ways. Why not use cancer to attack cancer ? This is a longshot. But it feels alright.
-- Jonas, Aug 23 2002


First of all, parasite can't home in on anything. The small lava go where the blood take them. If they don't find the right place that they can stay; liver, large intestine, brain, they die. So you will only find them where they can live. To equip a parasite with tools that only attach them to cancer cell, you will need to design a specie from scratch.

Cancer cells are difficult to target because they are so much resemble the healthy cells. There are certain features that distinguish them apart. That is how biosy is done. But those are very minor.

I don't know the details. Bacteria and virus don't normally home in to specific cells either. Some cells are just easier target for them because their structure and availability. Some of more violent viral infections target the blood cell, cause them to spread across the body very rapidly and cause death in matter of days.
-- bing, Aug 24 2002


There is a very cool cancer treating strategy being tested right now using a variation on this idea. The main cellular defense against viral infection is suicide - the cell dies and chops up all its machinery so the virus cant use it and reproduce - the virus is trapped in the dying cell it tried to use. Cancer cells dont commit suicide - if they did they would have done it when they realized they were getting screwed up and becoming cancer. So - the perfect host for a virus.

The virus being tested cant live in normal cells, only those with defective p53 (the master suicide gene). So: injected it into a cancer, and it will affect only the bad ones! I think it is cool as stink.

As regards parasites, worms are sort of big and they generate big immune responses. Something like malaria or trichomonas would probably be better - less immune reaction.
-- bungston, Dec 10 2002


This is not a joke, and I wish I had a web link.

You are spot-on with your thinking. A recent study suggested limited success with using a variant of a cold sore bug to treat brain tumors.

I think the logic was that the brain doesn't grow after you become an adult, so any new cells in the brain are probably part of the cancer. Apparently cold sores attack new cells which is why they 'attack' new-growth areas (the lips and mouth). This is probably way to simplistic, but this was the basic idea being presented on some science show. I might be wrong, though....
-- not_only_but_also, Mar 28 2003


I'm a little cautious about using a virus or whatever foreign bug intentionally. Mind you if I had a brain tumour I'd grab anything that offered hope.

Other than the risk of whatever it is spreading in you and amongst you r loved ones, the problem is that the body is really quite good at killing things it doesn't recognise.

Your nematodes probably wouldn't last long. On the other hand, culturing the body's own immune cells (if it could be done) might help tremendously.

All you need is a source of stem cells. Your parents did remember to cryogenically store your umbilical cord blood, didn't they?
-- FloridaManatee, Mar 28 2003


not_only_but_also is right (see link):

The application of genetically engineered herpes simplex viruses to the treatment of experimental brain tumors.

Andreansky SS, He B, Gillespie GY, Soroceanu L, Markert J, Chou J, Roizman B, Whitley RJ.

Department of Pediatrics, University of Alabama at Birmingham 35233, USA.

Due to lack of effective therapy, primary brain tumors are the focus of intense investigation of novel experimental approaches that use vectors and recombinant viruses. Therapeutic approaches have been both indirect, whereby vectors are used, or direct to allow for direct cell killing by the introduced virus. Genetically engineered herpes simplex viruses are currently being evaluated as an experimental approach to eradicate malignant human gliomas.
-- mystic2311, Dec 12 2003



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