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The term "tumor suppressor" doesn't necessarily mean that the gene exists for the sole purpose of preventing cancer. It just means that the protein's normal fun

The term "tumor suppressor" doesn't necessarily mean that the gene exists for the sole purpose of preventing cancer. It just means that the protein's normal function happens to prevent cells from becoming cancerous. Many DNA-repair proteins fall into this category, for example, simply because repairing errors in a cell's DNA reduces the probability of that cell accumulating cancer-causing mutations. And yet, DNA-repair proteins pre-date the evolution of multicellular organisms, so they cannot possibly have evolved as a response to cancer. In practice, the term "tumor suppressor" generally means a gene for which recessive loss of function mutations are associated with cancer (i.e. you have to lose function of both copies of the gene in the same cell before there's an effect), while "oncogene" means a gene for which dominant gain of function mutations are associated with cancer (i.e. mutation in one copy of the gene is sufficient to have an effect). Neither term implies anything about how the gene evolved or whether selection due to cancer was a factor in the evolution of the gene.

dekhn 10y ago
While most of what you say is generally consistent with mainstream science (including my copy of Cancer by Weinberg, AKA, "the bible"), it neither refutes my point, nor provides any support for the parent poster's claim. Also, "DNA-repair proteins pre-date the evolution of multicellular organisms, so they cannot possibly have evolved as a response to cancer." is not a valid argument. There are eukaryotic DNA repair proteins not found in bacteria, for which evolutionary evidence shows they evolved more recently. A number of such genes aren't just DNA repair, but cell cycle controllers that respond to DNA damage and coordinate complex activity. Whether they are "sole purpose of preventing cancer", is a very deep question, and goes to the heart of the nature of cancer. For example, naked mole rats either never or very rarely get cancer; current thinking is that hyaluronase they produce has a protective effect. Did the genes that make enzymes that produce hyaluronase evolve "specifically to prevent cancer", or did they play other roles and just incidentally provide cancer protection? Those are challenging hypotheses to express and prove either way. I'm sure you're familiar with the Hallmarks of Cancer.

dekhn 10y ago

While most of what you say is generally consistent with mainstream science (including my copy of Cancer by Weinberg, AKA, "the bible"), it neither refutes my point, nor provides any support for the parent poster's claim. Also, "DNA-repair proteins pre-date the evolution of multicellular organisms, so they cannot possibly have evolved as a response to cancer." is not a valid argument. There are eukaryotic DNA repair proteins not found in bacteria, for which evolutionary evidence shows they evolved more recently. A number of such genes aren't just DNA repair, but cell cycle controllers that respond to DNA damage and coordinate complex activity. Whether they are "sole purpose of preventing cancer", is a very deep question, and goes to the heart of the nature of cancer. For example, naked mole rats either never or very rarely get cancer; current thinking is that hyaluronase they produce has a protective effect. Did the genes that make enzymes that produce hyaluronase evolve "specifically to prevent cancer", or did they play other roles and just incidentally provide cancer protection? Those are challenging hypotheses to express and prove either way. I'm sure you're familiar with the Hallmarks of Cancer.