Genetic variant within CDK6 regulates immune response to palbociclib treatment

Everyone carries a set of genetic variants that contribute to regulation of the levels of blood cells, with unknown clinical impact. One of them, rs445 within the cell-cycle checkpoint gene CDK6, reduces the levels of myeloid cell types including granulocytes.& nbsp;We treated CD3+ T cells and whole blood with palbociclib in 41 individuals, who were stratified by genotype for analyses. In T cells we assessed cell cycle and apoptosis, whereas in whole blood, apoptosis in activated (CD11b+), unactivated (CD11b-) granulocytes, cytotoxic (CD8 + CD4-), and helper (CD8-CD4+) T cells.& nbsp;We find that rs445 modulates the immune response of CD8+ T cells. It also increases the level of apoptotic CD11b + activated granulocytes after palbociclib treatment, which, in synergy with neutropenia, may affect drug related adverse events.& nbsp;These results suggest that the effect of palbociclib treatment may depend on underlying genetically encoded individual immune response as well as the direct response to the drug.