Time Ranges for Biochemical Processes

August 16, 2022 8:52 AM

I am trying to get a rough order-of-magnitude understanding of the time needed for human mitosis, in order to understand the progression of an "aggressive" cancer.

I'd like to know times (or ranges) for the following cellular events:

* Normal mitosis: starting at whatever trigger event, about how long does it take for one cell to turn into two daughter cells?

* Is the length of time similar across tissue types?

* Is the length of time similar for any mitosis, or could one type-X cell divide in an hour, while a neighboring type-X cell takes 6 hours?

* Is there a refractory period during which new daughter cells cannot begin mitosis? Is this a resource bound (e.g. the new cell needs to grow to a certain minimum size, or needs to collect amino acids or something before it can divide again)?

posted by spacewrench to Science & Nature (5 answers total)

HeLa cells (from Henrietta Lacks’s cervical cancer) are routinely grown in biomedical lab settings. Those cells have an optimal doubling time of about 23 hours. Optimal being the fastest they can go— fully resourced cells.

In a solid tumor cancer setting, only the cells that are getting adequate nutrition are growing and dividing. Many solid tumors are not well vascularized, so the cells in the center of the tumor are starved of oxygen and nutrients; the centers of many solid tumors are necrotic (dead) because of this.

So, order of magnitude (as you asked) — under optimal conditions, it takes about one day for a cancer cell to divide once forming 2 daughter cells. Everything else slows down from that approximate benchmark.
posted by Doc_Sock at 9:08 AM on August 16, 2022 [2 favorites]

Best answer: According to this wikipedia article on the cell cycle, intestinal crypt cells reproduce even faster than HeLa cells in culture - as short as 9-10 hours.

There are several phases to the cell cycle:
G₀, when the cell is not dividing at all, just living its life (some cells spend all there time here, others spend basically no time here)
G₁, when the cell is growing (generating more cytoplasm, mitochondria, and other cell stuff)
S, when a new copy of the DNA is Synthesized
G₂, more growing
M, mitosis (separation of the chromosomes) and cytokinesis (cell actually splits in two)

The S and M phases always take about the same amount of time; the G phases can vary a lot by type of cell.

All the phases are resource-bound and will take longer/fail if the cell is lacking something (energy, precursor molecules, coenzymes, etc.). Different deficiencies will have an effect at different points in the cycle.
posted by mskyle at 9:30 AM on August 16, 2022

Response by poster: Wikipedia for the win! Thanks very much for the pointer.
posted by spacewrench at 9:50 AM on August 16, 2022

Doc_Sock is exactly right, and they describe the nuances of a solid tumor. Yes, there are some fast-dividing cells in the body like intestine, but not all organs have cells that divide that quickly or even very often. Cancer in a particular organ will induce more frequent cell division, although not necessarily faster cell division. If a certain organ has cells that only divide once a month in healthy tissue, and that division takes ~24h, then having those divide every day in a cancer situation is significant growth.
posted by Knowyournuts at 10:04 AM on August 16, 2022 [1 favorite]

Doc_Sock: Many solid tumors are not well vascularized
In the 00s, I used to work adjacent to a breast-cancer research lab. One of the cunning ways in which cancer cells got to promote their own interests was to produce more vascular endothelial growth factor (VEGF) which encouraged the development of local blood vessels. The lab was working on ways to counter the production of VEGF and slow down progression.
posted by BobTheScientist at 1:22 PM on August 16, 2022