Abstract 5016: IL-6 influences PIM1 expression in renal cell carcinoma

Abstract Renal cell carcinoma (RCC) is the most common kidney neoplasm, accounting for over 430,000 new cases worldwide and 179,000 deaths annually. The overexpression of the proviral integration site for moloney murine leukemia virus 1 (PIM1) kinase is associated with poor clinical outcomes in patients with RCC. PIM1 is a constitutively active effector serine/threonine kinase with roles in tumor progression including cell proliferation, apoptosis, invasion, and migration. Yet, the mechanisms underlying PIM1 expression and its function in RCC are not fully delineated. IL-6 is a pleiotropic cytokine involved in the activation of the JAK/STAT signaling cascade. High serum IL-6 levels are implicated in the poor prognosis of RCC patients and are hypothesized to contribute to RCC invasion and metastasis. PIM1 is shown to be transcriptionally regulated downstream of JAK/STAT signaling and an IL-6/STAT3/PIM1 axis exists in pancreatic cancer. We thus hypothesize that this pathway also regulates expression of PIM1 in RCC. Here, we explore the levels of PIM1 in RCC and identify potential signaling pathways influencing PIM1 expression. Our results show five RCC cell lines, 769-P, 786-O, ACHN, CAKI-1, and RCC-4 cells overexpress PIM1 relative to normal renal proximal tubule epithelial cells. In RCC cell lines, IL-6 secretion correlates with PIM1 protein levels. Treatment with ruxolitinib, a JAK1/2 inhibitor, leads to a dose and concentration dependent decrease in PIM1 levels. We then tested whether incubation with an IL-6 neutralizing antibody is sufficient to regulate PIM1 protein levels. Indeed, use of an IL-6 antibody resulted in decreased pJAK2 protein and PIM1 protein. Our initial studies suggest that differential expression of PIM1 among RCC cell lines may be linked to autocrine IL-6 signaling. Interestingly, 769-P cells demonstrate increased PIM1 levels but do not secrete IL-6 and neither ruxolitinib treatment nor incubation with an IL-6 neutralizing antibody appear to affect PIM1 levels. Therefore, an IL-6/JAK-independent pathway resulting in increased PIM1 protein levels likely exists in 769-P cells. Further investigation is required to elucidate the contexts of PIM1 regulatory pathways in order to develop novel targeted anti-cancer strategies in RCC. Citation Format: Kimberly S. Meza, Sheldon L. Holder. IL-6 influences PIM1 expression in renal cell carcinoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5016.