Abstract 627: IL-6 signaling via JAK/STAT axis influences PIM1 expression in renal cell carcinoma

Abstract Renal cell carcinoma (RCC) is a top ten malignancy in the U. S. Overexpression of the proviral integration site for moloney murine leukemia virus 1 (PIM1) kinase is associated with poor clinical outcomes in RCC patients. PIM1 is a constitutively active serine/threonine kinase promoting cell proliferation, apoptosis resistance, invasion, and migration. The mechanisms underlying PIM1 expression and its function in RCC are not fully delineated. IL-6 is a pleiotropic cytokine that activates the JAK/STAT signaling cascade. High serum IL-6 levels are associated with the poor prognosis of RCC patients and may contribute to RCC invasion and metastasis. STAT3/5 binds directly to the PIM1 promoter inducing PIM1 expression. An IL-6/STAT3/PIM1 axis exists in pancreatic and breast cancer. We previously reported that PIM1 is overexpressed in a panel of human RCC cell lines relative to normal and immortalized renal proximal tubule epithelial cells. We also identified that RCC cells secrete IL-6. Our prior studies suggest that differential expression of PIM1 may be linked to autocrine IL-6 signaling. We thus hypothesize that an IL-6/JAK/STAT pathway regulates the expression of PIM1 in RCC. To understand how IL-6 signaling through the JAK/STAT pathway may regulate PIM1 expression in RCC cells, we examined whether IL-6 blockade using anti-IL-6 antibody or tocilizumab, would modulate PIM1 expression. Similarly, we assessed whether ruxolitinib, and LLL12, a STAT3 inhibitor could regulate PIM1 expression. We then evaluated the effect of ruxolitinib treatment on cell viability. In RCC cell lines, IL-6 blockade through either anti-IL-6 antibody or tocilizumab was sufficient to decrease PIM1 protein levels. Treatment with ruxolitinib leads to a dose and time-dependent decrease in PIM1 levels. Incubation with a STAT3 inhibitor also resulted in decreased PIM1 levels in RCC cells. Treatment with ruxolitinib also appears to decrease cell viability in a dose-dependent manner. These results suggest that differential expression of PIM1 in RCC may be linked to autocrine IL-6 signaling via a JAK/STAT/PIM1 axis. Multiple FDA-approved agents are available that target this pathway. Further investigation is required to determine the efficacy of these agents in pre-clinical models and even clinical trials. Citation Format: Kimberly S. Meza, Kimberly Seymour, Sheldon L. Holder. IL-6 signaling via JAK/STAT axis influences PIM1 expression in renal cell carcinoma abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 627.