MAPK8 and Miyoshi myopathy: We found that both JJN3 and RPMI 8226 cells are resistant to these inhibitors (Figure S8A); also, co‐treatment of MM cells with PIs and CI‐1040 or JNK‐IN‐8 inhibitors for 24 hours slightly increased cell death for both cell lines only in the case of co‐exposure with BTZ (Figure S8B,C).