Fig. 5

The sensitivity to palbociclib is associated with the lack of RB1 deletion/mutation in CCND1+ human myeloma cell lines. a Cells were cultured for 24 h with palbociclib (500 nM); cell cycle modifications (a) and Rb phosphorylation (b) were assessed by propidium iodide staining and Western blotting, respectively. For HMCLs harboring a functional RB1, mean phase S/G2 reduction was 26% (95% CI = 16–34%) (paired t test, p = 0.03) and mean (pRb/Rb reduction was 63% (95% CI = 42–91%) (paired t test, p = .03). c, d, e Cells were cultured for 4 days with increasing concentrations of palbociclib, and sensitivity was determined by the area under the curve (AUC) using the MTT assay. c Correlation between S/G2 phase inhibition and palbociclib sensitivity (AUC z-score), bootstrapped robust linear regression. d, e Palbociclib sensitivity according to either the CDKN2A/CDKNC status or MM molecular classification. RB1 abnormal HMCLs are indicated (Mann–Whitney test)