This thesis of Itamar Braga Dias set out to answer that question. Using stem cell technology, we built living, beating cardiac tissue in the laboratory and exposed it to drug concentrations mimicking actual patient treatment. We found that doxorubicin drives heart cells into cellular senescence, a permanent standstill where cells stop functioning normally but do not die, closely mirroring natural cardiac aging. Attempts to remove these senescent cells with targeted drugs backfired, worsening heart function.
A key discovery came from comparing heart cells of patients who suffered heart failure with those who tolerated far higher doses without problems. Vulnerable patients carried higher levels of damage in the DNA of their mitochondria, the cell's energy factories, before treatment began. This genetic wear-and-tear, combined with weaker antioxidant defenses, left their hearts with insufficient reserve to absorb the stress of chemotherapy. Vulnerability is not simply about dose; it is written into the cells from the start.
Finally, a newer drug, ribociclib, was found to damage the heart through an entirely different mechanism, showing that cardiac protection during cancer treatment must be tailored to the individual.
