MDA5 activation enhances lenalidomide sensitivity in ADAR1-deficient MM cells. (A) Cell growth curves of MDA5-KD, RIG-I-KD, or PKR-KD in ADAR1-KD RPMI-8226 and OCI-MY5 cells over 5 days, determined using CTG assay. (B) Relative mRNA expression of ISGs and IFNs (IFN-α and IFN-β) in MDA5-KD, RIG-I-KD, or PKR-KD in ADAR1-KD RPMI-8226 and OCI-MY5 cells, determined by qRT-PCR and compared against their respective shSCR. (C) Cell viability of MDA5-KD, RIG-I-KD, or PKR-KD in ADAR1-KD RPMI-8226 and OCI-MY5 cells at 6 days after treatment with increasing concentration of lenalidomide, determined by CTG assay. (D) Western blot validation of the OE of MDA5 in KMS-11 and MM1.S LenR cells. Blot with ADAR1 p150 and ADAR1 p110 was probed with ab88574 (Abcam), and the blot with only ADAR1 p150 was immunoblotted with ab126745 (Abcam). (E) Cell viability of MDA5-overexpressing KMS-11 and MM1.S LenR cells at 6 days after treatment with increasing concentration of lenalidomide, determined by CTG assay. Data are presented as mean ± SD of biological triplicates. Significance differences were determined by two-tailed Student t test and for the line bracket by one-way ANOVA with Tukey post hoc test. Statistical significance is denoted by ∗P ≤ 0.05; ∗∗P ≤ 0.01.