Aging and cancer are two harsh but inescapable realities of life as a multicellular organism and while humanity can strive to treat one or the other, eventual death is mathematically guaranteed, according to a new study.
A pair of researchers from the University of Arizona have developed the first general model of the interaction between intercellular competition, aging and the onset and development of cancer in humans. The model asserts that aging is a fundamental and inescapable feature of multicellular life as we know it.
"Aging is mathematically inevitable - like, seriously inevitable. There's logically, theoretically, mathematically no way out," said Joanna Masel, co-author of the study and professor of evolutionary biology at the University, as cited by Phys.org.
Masel and her colleague, postdoctoral researcher Paul Nelson, published their findings in a study entitled, "Intercellular Competition and Inevitability of Multicellular Aging," which features in the latest edition of Proceedings of the National Academy of Sciences.
Current models posit that if we could perfect the purification process between cells that we could, theoretically, delay the aging process indefinitely. However, the fitness and ultimate survival of a multicellular organism depends not just on the efficiency of each individual cell but also on the interaction and cooperation between cells.
The newly developed theory expands on this existing thinking, which maintains that a failure to remove weakened alleles (types of gene responsible for hereditary traits and variations) as we age increases our chances of mortality as we reach later life, and goes one step further by claiming that multicellular organisms would age whether we perfected such selection processes or not.
Two things happen as we age: cells slow down and deteriorate, as evidenced by our hair turning grey as we age or the growth rate of cells increases rapidly which is a fundamental cause of cancer, even if it never materialises in malignant tumors that create detectable symptoms.
"As you age, most of your cells are ratcheting down and losing function, and they stop growing, as well," said Nelson, lead author of the study, as cited by Phys.org. "But some of your cells are growing like crazy. What we show is that this forms a double bind - a Catch-22.”
“If you get rid of those poorly functioning, sluggish cells, then that allows cancer cells to proliferate, and if you get rid of, or slow down, those cancer cells, then that allows sluggish cells to accumulate. So you're stuck between allowing these sluggish cells to accumulate or allowing cancer cells to proliferate, and if you do one you can't do the other. You can't do them both at the same time," Nelson added.
While you can fix one of the the problems of aging, you will never, mathematically speaking, be able to escape the other. So we can slow down the aging process but will ultimately succumb to cancer, or vice versa.
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"Either all of your cells will continue to get more sluggish, or you'll get cancer. And the basic reason is that things break,” Massel said. “It doesn't matter how much you try and stop them from breaking, you can't.”