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Tumors are known to burn glucose and secrete lactate (this is known as the Warburg effect). Where does this lactate go?

Does it steadily accumulate in the neighborhood of the tumor? This doesn't seem likely. I mean, eventually an equilibrium concentration of lactate in the neighborhood of the tumor must be reached that is balanced by some process taking lactate away from the tumor. The nature of this lactate drain is what I am asking about.

Does it enter the circulation system and is degraded somewhere else in the body (as a part of the Cori cycle)?

Is it consumed by neighboring non-malignant cells?

A combination of all of the above?

Something else?

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Most of the lactate produced by tumors probably enters the circulation and is taken up by other tissues (like the Cori cycle, correct). There are several studies like this one measuring glucose uptake and lactate release by tumors in vivo, and it is clear that a substantial amount of lactate is released into the veins draining the tumor site.

Oxidation of lactate by neighboring cells within tumors has been reported as well, but I don't know of any quantitative data on exactly how much lactate this process can consume. But it seems unlikely that this can remove a major fraction of lactate produced by glycolytic tumors, since glycolysis produces lactate at a much higher rate than respiration consumes it (per ATP generated).

It's also true that tumors can accumulate lactate. Some tumors are poorly perfused, with "disorganized" blood vessels and blood flow, and then waste products may not be cleared away efficiently.

So yes, all of the above :) There are large differences between individual tumors in all these parameters, so there is no generally valid answer I think.

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  • $\begingroup$ I guess I'm not expecting to find a general answer. But at least some references in the literature would be nice. The papers you point out are already useful. $\endgroup$ – becko Feb 7 '16 at 17:47
  • $\begingroup$ "But it seems unlikely that this can remove a major fraction of lactate produced by glycolytic tumors, since glycolysis produces lactate at a much higher rate than respiration consumes it" Has this been measured/estimated? $\endgroup$ – becko Nov 13 '17 at 16:52
  • $\begingroup$ @becko I'm not aware of any quantitative data on how much lactate is re-oxidized in tumors. But given that respiration yields 10--15 times more ATP than glycolysis for the same amount of carbon, it seems that a large population of purely oxidative cells would be needed re-oxidize all surplus lactate from glycolytic cancer cells. And again, there is plenty of data showing that tumors generally produce lactate. (In some cases even causing life-threatening acidosis: ncbi.nlm.nih.gov/pmc/articles/PMC4497494 ) $\endgroup$ – Roland Nov 13 '17 at 17:34

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