To alleviate the difficulty of the detection of labile phosphorylation events in formalin-fixed, paraffin-embedded (FFPE) tissue samples associated with the low cellular concentration of Thr172-phosphorylated CDK4 [24], Raspé et al. identified a gene expression signature of 11 genes that correlated with the Thr172 phosphorylation status and correctly predicted the CDK4 modification profile to palbociclib in 49 out of 52 breast tumors analyzed and sensitivity in 20 of 25 cell lines tested [91]. The gene discussed is CDK4; the disease is breast neoplasm.