The 'Adaptive Fidelity' Hypothesis: mCAs as Regulatory Switches for Senescence-Associated Secretory Phenotypes
I propose that mosaic chromosomal alterations (mCAs) in hematopoietic stem cells (HSCs) aren't just signs of genomic instability or random drift. Instead, they act as "evolutionary tuners" of the Senescence-Associated Secretory Phenotype (SASP). I hypothesize that recurring mCAs, such as the loss of 12p or 13q, function as stochastic rheostats. They force cells into a pro-inflammatory state, effectively decoupling individual cellular fitness from the stability of the surrounding tissue.
While recent work treats CHIP-associated mCAs primarily as drivers of cancer risk via clonal expansion [https://pubmed.ncbi.nlm.nih.gov/39012906/], I suspect the higher hazard ratios for solid tumors and mortality are actually driven by a secondary, non-cell-autonomous mechanism.
If we view mCAs as "entropy tags" for aging, we have to explain why certain copy-number variants show such contradictory effects—appearing protective in some Alzheimer’s models while simultaneously raising cancer risk [https://www.frontiersin.org/journals/aging-neuroscience/articles/10.3389/fnagi.2023.1241412/full]. I believe these mCAs operate within a Selection-Mutation Equilibrium. In the high-entropy environment of aging, an mCA that triggers a constitutive SASP might offer a temporary selective advantage to the HSC by shifting the local cytokine landscape. This, however, inadvertently helps pre-malignant solid-tumor cells thrive elsewhere in the body.
This "Adaptive Fidelity" framework relies on two points:
- Threshold Dynamics: The 10% cell fraction threshold [https://pubmed.ncbi.nlm.nih.gov/39012906/] isn't just an arbitrary number; it’s likely the "critical mass" where the combined SASP signal from a clonal population begins to override local tissue quiescence.
- WGD as a Buffer: If whole-genome duplication (WGD) protects against extreme instability [https://www.sciencedaily.com/releases/2026/01/260125083344.htm], then mCAs that occur after WGD might be "stabilized deviations." These mutations allow cells to survive in an inflammatory milieu that would normally trigger apoptosis.
To test this, we need to move past simple clonal expansion and start mapping the secretome to the genotype. I propose using CRISPR-engineered iPSCs to recreate the specific mCA profiles seen in high-risk patients. By applying single-cell secretome profiling (sc-SASP), we can measure the inflammatory "noise" produced by these clones against wild-type cells.
This hypothesis is falsifiable: if mCAs in HSCs don't produce a quantifiable change in the inflammatory secretome of the clonal niche, or if that secretome is identical to standard senescent cells, then the "Adaptive Fidelity" model doesn't hold.
By reframing mCAs as functional regulatory switches rather than simple mutations, we start to see the "genetic sandbox" [https://dceg.cancer.gov/research/how-we-study/genomic-studies/genetic-mosaicism-study] as being governed by predictable evolutionary rules—rules where the body trades long-term malignancy risk for short-term immune fitness.