From: Steve Harris <sbharris@ix.netcom.com> Newsgroups: sci.med.nutrition,sci.med,sci.med.pharmacy Subject: Re: Drugmakers not following up speedy approval-US study Date: 3 Jun 2005 10:36:16 -0700 Message-ID: <1117820176.628850.215870@g47g2000cwa.googlegroups.com> Without knowing the mechanism for all cancers, obviously I can't give you a complete answer. At least SOME cancers are due to a gene mutation in a cell. It's NOT present in all cells in that individual, or even all cells in that tissue. It happens during replication in ONE cell, and it's somehow conserved in the lineage of that cell. Often it takes MORE than one of these events to trigger off a cancer (two or more somatic mutations), but the concept is still the same--- not all cells in the parent tissue have the cancer genetics. Therefore, once you kill all the cells which do, you go back to the original state of risk. Which may not be that high. Indeed may be low enough to allow a reasonable probability that the organism will make it to old age and die of something else before cancer strikes in that tissue again. Now, what constitutes the baseline risk? Some of it is genetics of the host, but not a lot. You have to work hard to find the increased correlation in cancer risk between identical twins vs fraternal twins. So don't imagine that what you're going to die of is written in your DNA like some program. It isn't. Some of the excess risk is environment. We all know about carcinogens like cigarette smoke and chimney soot, and people often asssume that all cancer risk which isn't genetic, some from mutagens and carcinogens in the environment. Certainly if you've had lung cancer once and cure it, you have an increase risk in the other lung if you continue to smoke, and for many years, even if you quit. Colon cancer suffers presumably also if they keep eating hot dogs (or whatever). That's why people blame polution or food or something whenever their kids get cancer. But population studies suggest that the environment is responsible for no more than half the variation in cancer risk. So what IS the rest due to? Probably to some kind of roll of the dice in cell division. For years I used to do aging studies in rodents, where the animals were all genetically essentially genetically identical, identically housed side by side, and fed the same diet. We had no other variables left to control. And yet they all died of different things. Some got lymphomas, some hepatomas, some lived to old age with arthritis and died of pneumonia. Every time we repeated the experiment with the same strain we got the same percentages of the same kinds of cancers, but we could never tell which animal was going to get what. That says something. There ARE events in cell division which are random. Indeed some are due to straight quantum mechanical events like enol-keto form tautomersm in cytidine. And these DO cause mutations. So perhaps we're seeing the basic quantum dice roll at the most fundamental level of the laws of nature operate here. Or not. Random processes in science are where we sweep up all the things for which we can't identify causal markers. Not all my mice had the same mothers, nor the same place in the uterous during gestation, etc, etc. The diets weren't PERFECTLY identical, and the radiation environment from cosmic rays wasn't EACTLY the same for each animal, and could never be, even for animal in the same cage. And so on. Hope that helps. Bottom line is it's a risky world, and some of the risk is in the deal of the cards where you can't get at it. Complain to the Great Dealer about that. But not necessarily to your doctor or to city hall. SBH From: "Steve Harris" <sbharris@ix.RETICULATEDOBJECTcom.com> Newsgroups: sci.med Subject: Re: A Vaccine for Cervical Cancer...? Message-ID: <ExiD9.3454$It3.311284@newsread2.prod.itd.earthlink.net> Date: Fri, 22 Nov 2002 04:39:00 GMT Wyle E. Coyote, M.D. wrote in message <768D945F9AD84345.F92BD758D9671008.6477476985105E1B@lp.airnews.net>... > >"Steve Harris" <sbharris@ix.RETICULATEDOBJECTcom.com> wrote in message >news:R6gD9.2677$OZ4.280531@newsread1.prod.itd.earthlink.net... >> Carey Gregory wrote in message ... >> >Coyotedave <Coyotedave_member@newsguy.com> wrote: >> > >> >>Well , I not a doctor, but I find it hard to believe that a Virus >> >>alone can cause Cancer in Humans, >> > >> >Well, so much for your opinions. >> >> >> No kidding. If viruses cause cancers in animals (RSV, hepadnaviruses, >> FeLV and so on) then why should it not be also the case with humans? >> There's nothing special about our cells, or the way viruses attack >> them. >> > >You mean like HIV (lymphoma) and hepatitis B (liver cancer)? > >All the best, > >Wyle Yep. There are even family resemblances in viruses, so that a cancer causing virus in animals causes the same kinds of cancers in people. The hepadna viruses cause liver cancer in woodchucks, and hep B is a hepadnavirus of humans. FeLV causes leukemia in house cats, and HTLVs, the human analogues, cause leukemia in humans (though most human leukemias are not caused by this virus). FIV predisposes to lymphoma in house cats, SIV to lymphoma in Asian monkeys, and HIV to lymphoma in humans-- all are lentiviruses, a type of retrovirus. Kaposi's sarcoma isn't a typical cancer, but it's certainly caused by a virus: HHV-8, also known as KSV. This virus causes KS in people immunosuppressed, as for transplant, or from infection by HIV. And by the way, viruses aren't the only cancer causing infectious agents. Cancer is a consequence of too rapid cell turnover, and this can be caused by an irritative factor, including irritative infections. There's a very clear association, which is no doubt causal, between gastric lymphoma and H. pylori infection. -- I welcome email from any being clever enough to fix my address. It's open book. A prize to the first spambot that passes my Turing test. |