Kasi, A. | bioRxiv Science

bioRxiv2025

Macrophage-derived WNT regulates tumor immune microenvironment to reduce colitis-associated colon cancer

Prolonged colonic inflammation and ulcerative colitis lead to colon cancer. The rapid growth and treatment-resistant nature of these tumors are primarily influenced by an immunosuppressive tumor microenvironment, which is led by tumor-associated macrophages (TAMs). However, factors influencing or regulating the immunosuppressive nature of TAMs have not been sufficiently studied. In this manuscript, we use a mouse model of colitis-associated colorectal cancer (CRC) to demonstrate that WNT expression in TAMs regulates their immunosuppressive function by inhibiting Glycogen synthase kinase-3 beta (GSK-3{beta}) within the macrophages, possibly through an autofeedback loop. GSK3{beta} is a positive regulator of PD-1 and PDL1 expression in macrophages and promotes an immunosuppressive microenvironment. Therefore, GSK-3{beta} inhibition alters the immunosuppressive nature of the immune microenvironment and effectively controls tumor growth. In Csf1r-iCre; Porcnfl/fl mice, the absence of macrophage-derived WNT promotes tumor growth in the model of colitis-associated colon cancer. Absence of macrophage-derived WNT stabilizes GSK-3{beta} in macrophages and promotes an immunosuppressive tumor microenvironment. We also show that pharmacological inhibition of GSK-3{beta} in a macrophage-specific manner, achieved by systemic delivery of a lipo-GSK3{beta} inhibitor, effectively inhibits tumor growth. Therefore, this manuscript demonstrates for the first time that the macrophage-specific modulation of GSK3{beta} can be a potential target to treat colitis-associated colon cancer.

cancer biology↗

bioRxiv2024

ATF4 regulates mitochondrial dysfunction, mitophagy, and autophagy, contributing to corneal endothelial apoptosis under chronic ER stress in Fuchs dystrophy

PURPOSEEndoplasmic reticulum (ER) stress, mitochondrial dysfunction, and mitophagy are known to contribute independently to corneal endothelial cell (CEnC) apoptosis in Fuchs endothelial corneal dystrophy (FECD). However, the role of a specific ER stress pathway (PERK-ATF4-CHOP) in regulating these events is unknown. This study aims to investigate the role of ATF4 in regulating mitochondrial dysfunction and mitophagy, which ultimately leads to CEnC apoptosis in FECD. METHODSHuman corneal endothelial cell line (21T), Fuchs corneal endothelial cell line (F35T), and primary human corneal endothelial cells were treated with ER stressor tunicamycin (Tun). ATF4 siRNA was used to knock down ATF4 in 21T cell line and primary corneal endothelial cells. Mitophagy and apoptotic proteins were analyzed using Western blotting. ATF4+/- and ATF4 +/+ mice were irradiated with UVA to assess ER stress and corneal endothelial apoptosis. RESULTSF35T cell line had significantly increased expression of the ER stress pathway as well as caspase-mediated apoptotic molecules compared to 21T at baseline, which further increased after tunicamycin treatment. F35T cells exhibited significantly decreased ATP and MMP, and increased mitochondrial fragmentation, which was further exacerbated after Tunicamycin. F35T cell line also demonstrated inhibition of mitophagy, similar to 21T, after treatment with Tunicamycin, despite the upregulation of mitophagy initiators. ATF4 knockdown attenuated ER and mitochondrial stress proteins, rescued mitochondrial membrane potential (MMP) loss, downregulated mitochondrial fragmentation, activated mitophagy, and prevented cell death under chronic ER stress. ATF4+/-mice had increased CE numbers, with improved cellular morphology and decreased ER stress CHOP expression, compared to ATF4+/+ mice post-UVA. CONCLUSIONSPro-apoptotic ATF4 induction following ER stress disrupts mitochondrial function, leading to mitophagy inhibition and CEnC apoptosis. This study highlights the importance of ATF4 in ER-mitochondrial crosstalk and its contribution to CEnC apoptosis in FECD.

cell biology↗