LEN selectively induces apoptosis of del(5q) MDS cells through ubiquitination and degradation of CSNK1A1, located on chromosome 5 [2, 3], a process dependent on functioning TP53. Bernard, et al recently described 378 TP53-mutated MDS patients showing that a multiple-hit TP53 lesion independently predicts poor outcome, while mono-allelic mutational status is more similar to wild-type TP53 [4]. The gene discussed is CSNK1A1; the disease is myelodysplastic syndrome.