ADAR1-regulated cytoplasmic dsRNA-sensing pathway is a novel mechanism of lenalidomide resistance in multiple myeloma

• Lenalidomide induces immunomodulating responses through activation of dsRNA-sensing pathway

• ADAR1 drives lenalidomide resistance in MM via suppression of lenalidomide-induced dsRNA-sensing response.

Immunomodulatory agents (IMiDs) are a major class of drugs for treating multiple myeloma (MM); however, acquired resistance to IMiDs remains a significant clinical challenge. While alterations in cereblon (CRBN) and its pathway are known to contribute to IMiD resistance, they account for only 20-30% of cases, and the underlying mechanisms in the majority of the resistance cases remain unclear. Here, we identified ADAR1 as a novel driver of lenalidomide resistance in MM. We showed that lenalidomide activates the MDA5-mediated dsRNA-sensing pathway in MM cells, leading to interferon (IFN)-mediated apoptosis, with ADAR1 as the key regulator. Mechanistically, ADAR1 loss increased lenalidomide sensitivity through endogenous dsRNA accumulation, which in turn triggered dsRNA-sensing pathways and enhanced IFN responses. Conversely, ADAR1 overexpression reduced lenalidomide sensitivity, attributed to increased RNA editing frequency, reduced dsRNA accumulation and suppression of the dsRNA-sensing pathways. In summary, we report the involvement of ADAR1-regulated dsRNA-sensing in modulating lenalidomide sensitivity in MM. These findings highlight a novel RNA-related mechanism underlying lenalidomide resistance and underscore the potential of targeting ADAR1 as a novel therapeutic strategy.