QuestforLife, how can I possibly assess the efficacy of a proposed telomere-hand-over mechanism that would selectively deliver benefit only to mitochondrially healthy cells (body perspective) when such a proposed mechanism isn't discussed in the paper?
It is you, not the paper, that has made a selective claim that "...handing over such telomeres only to mitochondrially healthy cells IS a pretty good defence against cancer.".
The "you" in the following refers to me, AD (see my nick): "Then you might be able to postulate some situation where a cancer cell could take advantage of that to the detriment of the body."
QuestforLife, it is you that are making the selective-mechanism claim. Not me, and not the paper. So, in your explanation of how this selective mechanism works, you would have to explain why a cancer cell would not (remember, your mechanism is selective only to healthy non-cancer cells) be able to take advantage of the mechanism for its benefit.
QuestforLife writes: "If you bothered reading the paper..."
The following summarizes my understanding of the paper, in brief:
The paper does not contain explicit, detailed statements that directly address the receptor or molecular mechanism by which a "River" is taken up by a target cell.
The paper is significantly more detailed about the release mechanism than the uptake mechanism. And it is you that are inferring, by way of your claim, that the paper suggests that there could be a selective uptake mechanism that targets only mitochondrially healthy cells.
The paper uses the word "targeted" but does not define the targeting mechanism. The abstract states that Rivers enable "targeted rejuvenation of senescent tissues across multiple organs". It also claims that Rivers travel systemically, acting as a youth signal that reaches the brain, liver, heart, and lungs. However, the paper does not identify the specific receptor or ligand that allows a River to bind specifically to a senescent cell versus any other cell--such as a cancer cell, for example.
The paper demonstrates that after Rivers are injected, senescent cells in distant organs show rejuvenation . This proves that uptake occurs, but it does not explain the molecular "address label" that guides the River to a specific cell. And, knowing the address label would be crucial in determining whether a River can be beneficially used by a cancer cell or not.
The paper places an emphasis on cargo, not delivery. The proteomics analysis focuses heavily on what is inside the River (depletion of GAPDH, enrichment of stemness factors) . The paper does not contain a parallel analysis of the River's surface markers (the "keys") or the corresponding receptors on target tissues (the "locks").
There is no experimental data in the paper demonstrating that uptake is dependent on the metabolic state of the recipient. Dependence is an inference that can be drawn from targeting claims of an undefined targeting mechanism (see above), not a fact that the paper actually demonstrates.
The paper manipulates FAO in T cells (via CPT1A restoration, ceramide modulation, PE supplementation) and directly measures River release. As an aside, you now admit that cancer cells can burn fat.
Proteomics (DIA and DDA) compare Rivers to APC vesicles, showing GAPDH depletion and stemness factor enrichment.
The paper injects Rivers into aged mice and observes rejuvenation in brain, liver, heart, etc. However, the paper does not manipulate recipient metabolic states (e.g., blocking FAO in target tissues, inducing different metabolic profiles) to see if uptake is blocked or altered.
The paper shows that Rivers "target" senescent tissues but does not identify the receptor-ligand pair. There were no experiments blocking putative receptors, no knockout models, no competition assays.
The paper states that Rivers enable "targeted rejuvenation of senescent tissues across multiple organs". That is an outcome statement—it shows that after injection, senescent cells in various organs improve. But it does not establish the mechanism of that targeting.
If, upon reflection, you find that your claim was poorly worded, then fine. However, if you continue to maintain there could be an "only" mechanism then the burden is on you to present it along with any material that supports it.