Why don't all whales have cancer? | Hacker News Reader

Why don't all whales have cancer?

icb.oxfordjournals.org

59 pointsalexwg20 comments

Related: As a means to fight cancer, large mammals have mechanisms to suppress telomerase and the other (alt) telomere repair mechanism. Small mammals like mice do not have this. Why? It wouldn't help them. Even if the cancer cells in a tumor could not lengthen their telomeres, many of them would still get big enough to kill the host. (An inch-wide tumor might be no big deal for us, but for a little field mouse, it's as big as the whole body!) Hence, there is no evolutionary benefit to these mechanisms, and small mammals do not have them.

It could be that whales do get cancer, but since it's much harder proportionately for cancer to kill them as compared to merely large mammals like us, the cancer often goes undetected, and something else kills the whale. After all, finding 1 inch tumors in a whale would be like finding a needle in a haystack.

Cancer cells mutate rather rapidly, to the extent that this often impairs their function. If a cancer doesn't achieve and maintain efficient metastatis, it won't keep spreading. Perhaps whales have enough bulk that they can simply absorb being riddled with tumors in what constitutes a small fraction of their bulk, allowing them to ride the cancer out until it mutates itself past the point of efficient spread and survival.

Some of the descendant cancer cells might lose their capacity for spreading and survival, but wouldn't selection favor those that maintain it? Is there really any reason to believe that its reproduction fidelity is so low that there wouldn't be enough non-mutated cells in each generation?

"spreading and survival" are contextual. "Cheater" cells might out-compete other tumor cells locally, but at the cost of the cancer surviving long term and successfully spreading elsewhere.

(Edit:Removed, so not to confuse people. Brain malfunction.

Didn't get the point that without new metastasis, the article's point is that the mutations of a given tumor will kill it.)

The question involves both. Can the cancer spread to new sites fast enough to escape dying in its present sites?

So basically, the theory is that once you get big enough, your tumors themselves get tumors?

Perhaps the reason whales are the largest mammals is that, for anything larger, their tumor-tumor get tumors, killing the tumor-tumor and allowing the tumor to kill the whale.

it is very counter-intuitive... but then again evolution is.

whales don't get larger because they need to eat more. whales may be perfectly sized for their food supply. A theory.

In any case I am about at my limits of my understanding of biology :P

What about bigger creatures, like dinosaurs? Is there any evidence of cancer among them? (I'm totally profane on the subject, just wondering).

Most (nearly all) dinosaurs were smaller than current whales.

To get a first hand impression, please visit the Museum of Natural History in New York City, which has many skeletons of both in display.

Why wouldn't the hypertumor go on to kill the host after it killed the tumor?

Maybe the hypertumor gets it's own tumor after a while, and the cycle continues. Or the immune system of the whale which doesn't react to the original tumor does react to the hypertumor. Or maybe the hypertumor only grows on the original tumors type of tissue. Etc.

This article is just about a hypothesis. It's anyones guess at the moment.

Moreover:

Why wouldn't the hypertumor have hyperhypertumors?

I was just discussing this exact topic with a geneticist friend of mine about 15 minutes ago. Small world.

One thing it does prove is that the problem of cancer suppression has been solved before. By evolution. That should give researchers a bit of hope at least.

Edit: He happens to think the linked hypothesis in the article is "bullshit."

Well, whales live under the water and most mammals have fur, so perhaps they are protected from the cancer causing sun more than humans. Elephants have thick protective skin.

Plus, humans tend to be closer to carcinogens like pesticides than other animals. Those deer in scandanavia are also herbivores...

It seems like they aren't limiting their variables enough. If they really wanted to determine the correlation between size and cancer, they'd need to use different sizes of the same species. What is the control group?

The sun is a cause of cancer, but not the only or even a primary cause. The real "cause" of cancer is cell mutation, which can be triggered by sun, chemical exposure, or simply sheer random chance -- part of the thesis of this article is that, since whales have so many more cells, the "random chance" type would be more likely to happen. And one tumor is enough to kill us, so why not whales? That's the question they're asking.

I may be mistaken, but I read the enzymes that allows cancer (and HIV) to continuously replicate unlike normal cells that die - may be a way to drastically reduce aging if engineered into human DNA.

You mean telomerases? Perhaps, but that also would probably increase cancer rates, as our own DNA copying enzymes would not have been increased in accuracy.

Maybe it also gives hope for a new cancer therapy: induce tumors on tumors. Similar to radiation therapy, except indirect.

Sup Dawg, We heard you like tumors so we...

No?

I'll get my coat.

Reply on news.ycombinator.com