Bilal Ünal

• Ünal, Bilal & Saatcioglu, Fahri (2025). Targeting the unfolded protein response for cancer therapy: mitigating tumor adaptation and immune suppression. Biomarker Research. 13. doi: 10.1186/s40364-025-00813-y. Full text in Research Archive Show summary

  There are significant stress factors within the tumor microenvironment (TME), such as hypoxia, oxidative stress, and nutrient deprivation. These disrupt endoplasmic reticulum (ER) function in cancer cells, as well as the infiltrating immune cells, leading to activation of the unfolded protein response (UPR) signaling, which the tumor uses to mitigate stress and survive. There are three canonical UPR pathways that are regulated by respective ER-resident transmembrane sensors: inositol-requiring protein 1α (IRE1α), PKR-like ER kinase (PERK), and activating transcription factor 6 (ATF6); activation of these pathways results in expression of cognate transcription factors that regulate gene expression to mitigate ER stress. Persistent UPR activation in the TME has been linked to aberrant tumor growth, progression, metastasis, angiogenesis, and therapy resistance in different cancer types. In addition, modulation of UPR activity significantly impacts immune cell function at different levels further impacting its role on the TME. Therefore, there is now significant interest to design novel therapies that target the UPR to kill cancer cells and simultaneously enhance protective anti-tumor immunity. Here we summarize recent findings as to how targeting UPR signaling can induce tumor regression and at the same time galvanize the immune response. We discuss the potential of integrating UPR targeting with other therapies, such as immune checkpoint inhibition, highlighting emerging strategies to improve therapeutic efficacy and overcome resistance. These recent insights underscore the importance of UPR as a novel therapeutic target for cancer treatment.

• Hansen, Stian Bakke; Ünal, Bilal; Kuzu, Ömer Faruk & Saatcioglu, Fahri (2024). Immunological facets of prostate cancer and the potential of immune checkpoint inhibition in disease management. Theranostics. 14(18), p. 6913–6934. doi: 10.7150/thno.100555. Full text in Research Archive Show summary

  Prostate cancer (PCa) is the most common non-cutaneous cancer in men and a major cause of cancer-related deaths. Whereas localized PCa can be cured by surgery and radiotherapy, metastatic disease can be treated, but is not curable. Inhibition of androgen signaling remains the main therapeutic intervention for treatment of metastatic PCa, in addition to chemotherapy, radionuclide therapy and emerging targeted therapies. Although initial responses are favorable, resistance to these therapies invariably arise with development of castration resistant PCa (CRPC) and lethal phenotypes. Recent findings have implicated the crosstalk between PCa cells and the tumor microenvironment (TME) as a key factor for disease progression and metastasis, and the immune system is becoming an increasingly attractive target for therapy. Given the striking success of immune checkpoint inhibitors (ICIs) in various cancer types, preclinical and clinical studies have begun to explore their potential in PCa. It has become clear that the PCa TME is largely immunosuppressive, and ICI therapy does not have efficacy for PCa. Intense effort is therefore being made in the field to understand the mechanisms of suppression and to turn the immunosuppressive TME into an immune active one that would enable ICI efficacy. Herein we examine this recent body of knowledge and how the mutational landscape of PCa integrates with an immunosuppressive TME to circumvent ICI-mediated T-cell activity and tumor killing. We then review the emerging potential success of combinatorial ICI approaches, utility of careful patient selection, and potential novel strategies to improve the efficacy of ICI for PCa therapy.

• Ünal, Bilal; Kuzu, Omer; Yang, Jin; Osorio, Daniel; Kildal, Wanja & Pradhan, Manohar [Show all 14 contributors for this article] (2024). Targeting IRE1α reprograms the tumor microenvironment and enhances anti-tumor immunity in prostate cancer. Nature Communications. 15(1), p. 1–21. doi: 10.1038/s41467-024-53039-1. Full text in Research Archive Show summary

  Unfolded protein response (UPR) is a central stress response pathway that is hijacked by tumor cells for their survival. Here, we find that IRE1α signaling, one of the canonical UPR arms, is increased in prostate cancer (PCa) patient tumors. Genetic or small molecule inhibition of IRE1α in syngeneic mouse PCa models and an orthotopic model decreases tumor growth. IRE1α ablation in cancer cells potentiates interferon responses and activates immune system related pathways in the tumor microenvironment (TME). Single-cell RNA-sequencing analysis reveals that targeting IRE1α in cancer cells reduces tumor-associated macrophage abundance. Consistently, the small molecule IRE1α inhibitor MKC8866, currently in clinical trials, reprograms the TME and enhances anti-PD-1 therapy. Our findings show that IRE1α signaling not only promotes cancer cell growth and survival but also interferes with anti-tumor immunity in the TME. Thus, targeting IRE1α can be a promising approach for improving anti-PD-1 immunotherapy in PCa.

• Sikkeland, Jørgen; Ng, Matthew; Nenseth, Hatice Zeynep; Ünal, Bilal; Qu, Su & Jin, Yang [Show all 8 contributors for this article] (2022). STAMP2 suppresses autophagy in prostate cancer cells by modulating the integrated stress response pathway. American Journal of Cancer Research. 12(1), p. 327–336. Full text in Research Archive Show summary

  Six Transmembrane Protein of Prostate 2 (STAMP2) is critical for prostate cancer (PCa) growth. We previously showed that STAMP2 regulates the expression of stress induced transcription factor ATF4, which is implicated in starvation-induced autophagy. We therefore investigated whether STAMP2 is involved in the regulation of autophagy in PCa cells. Here we show that STAMP2 suppresses autophagy in PCa cells through modulation of the integrated stress response axis. We also find that STAMP2 regulates mitochondrial respiration. These findings suggest that STAMP2 has significant metabolic effects through mitochondrial function and autophagy, both of which support PCa growth.

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