RPS15 mutations rewire RNA translation in chronic lymphocytic leukemia.

Recent studies of chronic lymphocytic leukemia (CLL) have reported recurrent mutations in the RPS15 gene, which encodes the ribosomal protein S15 (RPS15), a component of the 40S ribosomal subunit. Despite some evidence about the role of mutant RPS15 (mostly obtained from the analysis of cell lines), the precise impact of RPS15 mutations on the translational program in primary CLL cells remains largely unexplored. Here, using RNA sequencing and ribosome profiling, a technique that involves measuring translational efficiency, we sought to obtain global insight into changes in translation induced by RPS15 mutations in CLL cells. To this end, we evaluated primary CLL cells from patients with wild-type or mutant RPS15 as well as MEC1 CLL cells transfected with mutant or wild-type RPS15. Our data indicate that RPS15 mutations rewire the translation program of primary CLL cells by reducing their translational efficiency, an effect not seen in MEC1 cells. In detail, RPS15 mutant primary CLL cells displayed altered translation efficiency of other ribosomal proteins and regulatory elements that affect key cell processes, such as the translational machinery and immune signaling, as well as genes known to be implicated in CLL, hence highlighting a relevant role for RPS15 in the natural history of CLL.

Clonal analysis of granulocyte-monocyte colony-forming unit cells with the human androgen receptor gene in chronic myeloid leukemia.

Coexistence of Philadelphia chromosome-negative (Ph-) progenitors with the Ph+ clone in the early chronic phase of chronic myeloid leukemia (CML) has been documented in previous reports. A different evaluation of methods is needed to justify the clonality of the residual Ph- progenitors. Therefore, the X chromosome inactivation patterns in individual granulocyte-monocyte colony-forming unit (CFU-GM) colonies were studied with the clonality assay for the human androgen receptor gene. A prerequisite for this evaluation was the validation of T-lymphocytes and buccal cells as control cells representing the constitutional lyonization. The percentages of polyclonal CFU-GM cells were determined in 9 Ph+ women with CML and in 5 healthy women. Results of the clonal analysis of CFU-GM colonies were compared with those from reverse transcriptase-polymerase chain reaction analysis of single colonies for BCR/ABL transcripts. Both methods of CFU-GM cell analysis were in agreement regarding the presence of variable proportions (0%-94%) of normal cells in CML. Our results suggest that (a) T-cells and buccal cells have potential for use as controls for the clonal analysis of CML cases and (b) this method can evaluate the frequency of polyclonal/clonal CFU-GM cells in CML cases and is applicable to the analysis of myeloid clonal disorders that lack specific molecular markers.