Uncovering the Role of PIM2 in Modulating MCL1 Dependency and Activation of ISR-Mediated NOXA Expression

Our study delves into the intricate dynamics of the integrated stress response (ISR) axis, focusing on the pivotal role of PIM2 kinase and its interaction with the BCL2 family of proteins, revealing crucial mechanisms governing cell survival and tumor progression. Elevated PIM2 expression is a hallmark of various cancers, often correlating with disease aggressiveness. Using a model of normal and malignant plasma cells, we unveil that inhibiting PIM2 kinase triggers not only the production of phosphorylated BAD but also activates ISR-mediated NOXA expression. This shift towards heightened dependence on MCL1 underscores the synergy achieved through combined PIM/MCL1 inhibition, largely propelled by ISR-mediated NOXA expression. In mouse xenograft models, dual targeting of PIM2 and MCL1 effectively controls tumor growth, a response reversed by ISR-specific inhibition, concomitant with the upregulation of genes associated with tumor cell dissemination. These findings illuminate the molecular intricacies of PIM2 inhibition and its implications for cancer therapy, particularly in tumors marked by elevated PIM2 expression.