CK1α is essential for the survival of a majority of PEL cell lines. (A) Growth curve analyses of a panel of 8 Cas9-expressing PEL cell lines after transduction of 2 independent sgRNAs targeting CK1α. All cell lines were Cas9-transduced cell pools, except for BC-3/Cas9, which is a Cas9-expressing clone (described in “Methods”). sgIRF4 was included as a positive control and confirms that IRF4 is essential in all 8 PEL cell lines (supplemental Figure 3A). Cumulative live cell counts were normalized to those from cells transduced with the negative control guide sgAAVS1. Final reduction in live cell numbers after CK1α inactivation was statistically significant, except for BC-2 and VG-1 (n ≥ 3; all error bars represent standard error of the mean). (B) Representative western blot analyses confirm efficient CRISPR-induced inactivation of CK1α and demonstrate lack of regulation of IRF4. GAPDH served as loading control. Samples for westerns were taken at the end of the growth curves, except for BC-1, BC-2, and BC-5 (day 6).