Expression, mutation, and methylation of cereblon-pathway genes at pre- and post-lenalidomide treatment in multiple myeloma.

Cereblon (CRBN) is a target for immunomodulatory drugs. This study investigated the prognostic value of the expression of CRBN-pathway genes on the clinical relevance of lenalidomide (Len) treatment and evaluated the levels of CRBN-binding proteins and mutations in these genes after Len treatment. Forty-eight primary multiple myeloma cells were collected prior to treatment with Len and dexamethasone (Ld) and 25 paired samples were obtained post-Ld therapy. These tumor cells were used to determine the expression and mutated forms of the CRBN-pathway genes. Following normalization with CRBN levels, there was a significantly reduced IKZF1/CRBN ratio in samples that responded poorly to Ld therapy. Moreover, patients with low ratios of IKZF1/CRBN showed a significantly shorter progression-free survival (PFS) and overall survival (OS) than those with higher ratios. However, patients with high ratios of KPNA2/CRBN showed a significantly shorter PFS and OS than patients with lower ratios. Of the 25 paired samples analyzed, most samples showed a reduction in the expression of CRBN and an increase in IKZF1 gene expression. No mutations were observed in CRBN, IKZF1, or CUL4A genes in the post-Ld samples. In conclusion, a decreased expression of IKZF1 and increased expression of KPNA2 compared to that of CRBN mRNA predicts poor outcomes of Ld therapy.