MCT1 as molecularly validated predictive marker for lenalidomide-maintenance therapy in multiple myeloma

Biomarkers that predict response to lenalidomide maintenance therapy in patients with multiple myeloma (MM) have remained elusive. We have shown that IMiDs exert anti-MM activity via destabilization of MCT1 and CD147. Here, samples of 654 patients receiving lenalidomide (n=455), thalidomide (n=98) or bortezomib (n=101) maintenance were assessed using gene expression profiling and RNA-sequencing, followed by correlation of MCT1 and CD147 expression with progression-free (PFS) and overall survival (OS) data. Patients with high gene expression levels of MCT1 showed significantly reduced PFS (31.9 vs. 48.2 months in MCT1high vs. MCT1low, P=.03) and OS (75.9 months vs. not reached (NR) months in MCT1high vs. MCT1low; P=.001) in case of lenalidomide maintenance, whereas MCT1 expression had no significant impact on PFS or OS in patients with bortezomib maintenance. We validated the predictive role of MCT1 for IMiD-based maintenance in an independent cohort of patients receiving thalidomide (OS 83.6 months vs. NR in MCT1high vs. MCT1low; P=.03). Functional validation showed that MCT1 overexpression in human MM cell lines significantly reduced efficacy of lenalidomide, while no change was observed upon bortezomib treatment, both in vitro and in an MM xenograft model. Together, we establish MCT1-expression as a predictive marker for response to lenalidomide-based maintenance treatment.