The Unfolded Protein Response Mediator PERK Governs Myeloid Cell-Driven Immunosuppression in Tumors through Inhibition of STING Signaling

The primary mechanisms supporting immunoregulatory polarization of myeloid cells upon infiltration into tumors remain largely unexplored. Elucidation of these signals could enable better strategies to restore protective anti-tumor immunity. Here, we investigated the role of the intrinsic activation of the PKR-like endoplasmic reticulum (ER) kinase (PERK) in the immunoinhibitory actions of tumor-associated myeloid-derived suppressor cells (tumor-MDSCs). PERK signaling increased in tumor-MDSCs, and its deletion transformed MDSCs into myeloid cells that activated CD8⁺ T cell-mediated immunity against cancer. Tumor-MDSCs lacking PERK exhibited disrupted NRF2-driven antioxidant capacity and impaired mitochondrial respiratory homeostasis. Moreover, reduced NRF2 signaling in PERK-deficient MDSCs elicited cytosolic mitochondrial DNA elevation and, consequently, STING-dependent expression of anti-tumor type I interferon. Reactivation of NRF2 signaling, conditional deletion of STING, or blockade of type I interferon receptor I restored the immunoinhibitory potential of PERK-ablated MDSCs. Our findings demonstrate the pivotal role of PERK in tumor-MDSC functionality and unveil strategies to reprogram immunosuppressive myelopoiesis in tumors to boost cancer immunotherapy.

Prognostic impact of Additional Chromosomal Abnormalities in Egyptian Chronic Myeloid Leukemia Patients

BACKGROUND: Emergence of additional chromosomal abnormalities (ACAs) in chronic myeloid leukemia (CML) is associated with disease progression to advanced phases and reflects the genetic instability of CML. AIM: Is to evaluate the frequency of ACAs in chronic phase (CP) and advanced disease (AP) CML patients and study their impact on patient’s outcome, overall survival (OS) and event-free survival (EFS). RESULTS: The studied group (n = 73) included 31 males (43%) and 42 females (57%). Median age of patients at diagnosis was 37 years (17–76). Median TLC was 208×109/L (2.1–784.2), median Hb was 9.4 g/dL (5.7–13), and median platelets count was 290.5×109/L (13–1271). We identified 32 patients (44%) with ACAs. ACAs emergence was significantly associated with advanced phases of CML (13/21, 62%) compared to CP (19/52, 36%) (p = 0.048). ACAs were associated with lower median OS and EFS in CP compared to AP (38 vs. 120 ms) and (58.3 vs. 77 ms) (p = 0.026 and p = 0.065, respectively). Early molecular responders (6/17, 35%) at 3 months, and 6 months (10/26, 38%) developed ACAs less than nonoptimal responders. Disease phase, hepatomegaly and bone marrow eosinophilia were significant predictors of OS (p < 0.001, p = 0.02, p = 0.04, respectively). CONCLUSION: Early identification of ACAs in Ph+ metaphases at diagnosis and during therapy predicts CML outcome. ACAs emergence occurred at a higher frequency and at a younger age in our CML patients and are related to inferior EFS and OS.