Chronic inflammation is a cancer hallmark and chronic exposure to interleukin-1 (IL-1) transforms castration-sensitive prostate cancer (PCa) cells into more fit castration-insensitive PCa cells. p62 is a scaffold protein that protects cells from nutrient deprivation via autophagy and from cytotoxic reactive oxygen via NFκB and NRF2 antioxidant signaling. Herein, we report that the LNCaP PCa cell line acquires high basal accumulation of the p62-KEAP1 complex when chronically exposed to IL-1. p62 promotes non-canonical NRF2 antioxidant signaling by binding and sequestering KEAP1 to the autophagosome for degradation. But despite high basal p62-KEAP1 accumulation, only two of several NRF2-induced genes analyzed, GCLC and HMOX1, showed high basal mRNA levels, suggesting that the high basal p62-KEAP1 accumulation does not result in overall high basal NRF2 activity. Nutrient starvation induces NRF2-dependent GCLC upregulation and HMOX1 repression, and we found that chronic IL-1-exposed LNCaP cells show hypersensitivity to serum starvation-induced GCLC and HMOX1 regulation. Thus, chronic IL-1 exposure affects cell response to nutrient stress. While HMOX1 expression remains NRF2/KEAP1-dependent in chronic IL-1-exposed LNCaP cells, GCLC expression is NRF2/KEAP1-independent. Furthermore, the high basal p62-KEAP1 complex accumulation is not required to regulate GCLC or HMOX1 expression, suggesting cells chronically exposed to IL-1 evolve a novel NRF2-independent role for the p62/KEAP1 axis.

Background/Objectives: The milieu of inflammatory cytokines present in the prostate cancer (PCa) tumor microenvironment exerts various effects on cancer progression. Chronic exposure to the inflammatory cytokine interleukin-1 (IL-1) has been shown to impact signaling via the RELA/NF-kB pathway; however, the effects of chronic inflammation on the integration of different inflammatory signaling pathways, such as the interleukin-6 (IL-6)/STAT3 axis, requires further exploration. Methods: We generated in vitro subline models by exposing the C4-2 and LNCaP PCa cell lines to either IL-1α or IL-1β for several months. We then treated the resulting sublines with acute IL-1 alone, IL-6 alone, or IL-1/IL-6 in combination and assessed for sensitivity to cytokine signaling. We observed changes in proliferation and quantified using Ki-67 immunostaining. Cell proliferation was assessed after siRNA silencing RELA or STAT3. Results: IL-1/IL-6 signaling in combination enhanced the signaling effects of either cytokine alone, particularly cytostasis. While the chronic IL-1 sublines maintained sensitivity to acute IL-6 signaling, they lost sensitivity to acute IL-1 signaling and did not show the enhanced IL-1/IL-6 cytostatic response. Inhibition of RELA and STAT3 rescued cytostasis after IL-1/IL-6 treatment in parental PCa cell lines, but only STAT3 inhibition rescued proliferation in the chronic IL-1 sublines. Conclusions: Our work shows that IL-1/RELA and IL-6/STAT3 work in parallel to synergistically induce cytostasis. However, chronic IL-1 exposure selects for cells that attenuate IL-1/RELA signaling, subsequently attenuating IL-1/IL-6 synergy.

Chronic inflammation is a hallmark of the breast cancer tumor microenvironment and is also known to be associated with disease progression and therapeutic response. Interleukin-1 (IL-1) signaling has been widely studied in breast cancer biology; however, the long-term effect of sustained IL-1 exposure on hormone receptor-positive breast cancer cells remain poorly understood. In this study, we investigated how chronic IL-1 exposure influences inflammatory response, hormone dependency, and therapeutic sensitivity in ERα+/PR+ breast cancer models, MCF7 and T47D. Chronic IL-1 exposure attenuated response to subsequent acute IL-1 treatment, but the chronically exposed cells remained sensitive to serum deprivation, retained dependence on estrogen or progesterone receptor signaling, and responded robustly to endocrine and chemotherapeutic treatments. Extensive changes in basal gene expression and histone modification revealed that chronic IL-1 exposure alters transcriptional reprogramming and chromatin remodeling. Together, these findings demonstrate that chronic IL-1 signaling drives selective inflammatory response in hormone receptor-positive MCF7 and T47D breast cancer cells. This work underscores the continued therapeutic relevance of hormone receptor-targeted strategies in chronically inflamed tumors and provides insight into how sustained inflammatory stress shapes tumor behavior and gene regulation predicted to promote tumor progression.