β cells suffer from hypoxia due to the rapid metabolic rate to supply insulin production. Mechanistic study of β cell survival under hypoxia may shed light on the β cell mass loss in type 2 diabetes mellitus (T2DM). Here, we found that the expressions of LC3 and p62/SQSTM1, two key autophagy regulators, were significantly higher in β cells than that in non-β endocrine cells in both non-diabetic and T2DM human pancreases, and the autophagy process was accelerated upon Cobalt Chloride (CoCl2) treatment in ex vivo cultured primary human islets. Meanwhile, CoCl2 induced the upregulation of FOXO1 in human islets, where HIF-1α played a key role. CoCl2 treatment caused the increase of β cell apoptosis, yet inhibiting autophagy by Chloroquine or by FOXO1 knockdown further aggravated apoptosis, suggesting that FOXO1-regulated autophagy is protective for β cell survival under hypoxia. Immunofluorescence staining showed that LC3 and p62/SQSTM1 expressions were significantly decreased in T2DM patients and negatively correlated with HbA1c, indicating that the autophagy capacity of β cells is impaired along with the progression of the disease. Our study revealed that HIF-1α/FOXO1 regulated autophagy benefits β cell survival under hypoxia and autophagy dysregulation may account for β cell mass loss in T2DM. BRIEF SUMMARY: Our study revealed that HIF-1α/FOXO1 regulated autophagy benefits β cell survival under hypoxia and autophagy dysregulation may account for β cell mass loss in T2DM.

Background: Circular dorsal ruffles (CDRs) are rounded membrane ruffles induced on the dorsal surfaces of cells stimulated by growth factors (GF). They can serve as signal platforms to activate AKT protein kinase. After GF stimulation, phosphatidylinositol 3-kinase (PI3K) generates phosphatidylinositol (3,4,5)-triphosphate (PIP3) in the plasma membrane. PIP3 accumulates inside CDRs, recruits AKT into the structures, and phosphorylates them (pAKT). Given the importance of the PI3K-AKT pathway in GF signaling, CDRs are likely involved in cell growth. Interestingly, some cancer cell lines express CDRs. We hypothesized that CDRs contribute to carcinogenesis by modulating the AKT pathway. In the present study, we identified CDR-expressing cancer cell lines and investigated their cellular functions. Methods: CDR formation was examined in six cancer cell lines in response to epidermal growth factor (EGF) and insulin. The morphology of the CDRs was characterized, and the related signaling molecules were observed using confocal and scanning electron microscopy. The role of CDRs in the AKT pathway was studied using biochemical analysis. The actin inhibitor cytochalasin D (Cyto D) and the PI3K inhibitor TGX221 were used to block CDRs. Results: GF treatment induced CDRs in the hepatocellular carcinoma (HCC) Hep3B cell line, but not in others, including HCC cell lines HepG2 and Huh7, and the LO2 hepatocyte cell line. Confocal microscopy and western blot analysis showed that the PI3K-PIP3-AKT pathway was activated at the CDRs and that receptor proteins were recruited to the structures. Cyto D and TGX221 completely blocked CDRs and partially attenuated GF-induced pAKT. These results indicate that CDRs regulate the receptor-mediated PI3K-AKT pathway in Hep3B cells and the existence of CDR-independent pAKT mechanisms. Conclusions: Our results showed that CDRs modulate the AKT pathway in Hep3B cells. Since CDRs were not observed in other HCC and hepatocyte cell lines, we propose that CDRs in Hep3B would determine the carcinoma characteristic of the cell by aberrantly triggering the AKT pathway. Signaling molecules involved in CDR formation are promising therapeutic targets for some types of HCC.

Transplant oncology is a newly emerging discipline integrating oncology, transplant medicine, and surgery and has brought malignancy treatment into a new era via transplantation. In this context, obtaining a drug with both immunosuppressive and antitumor effects can take into account the dual needs of preventing both transplant rejection and tumor recurrence in liver transplantation patients with malignancies. Capecitabine (CAP), a classic antitumor drug, has been shown to induce reactive oxygen species (ROS) production and apoptosis in tumor cells. Meanwhile, we have demonstrated that CAP can induce ROS production and apoptosis in T cells to exert immunosuppressive effects, but its underlying molecular mechanism is still unclear. In this study, metronomic doses of CAP were administered to normal mice by gavage, and the spleen was selected for quantitative proteomic and phosphoproteomic analysis. The results showed that CAP significantly reduced the expression of HSP90AB1 and SMARCC1 in the spleen. It was subsequently confirmed that CAP also significantly reduced the expression of HSP90AB1 and SMARCC1 and increased ROS and apoptosis levels in T cells. The results of in vitro experiments showed that HSP90AB1 knockdown resulted in a significant decrease in p‐Akt, SMARCC1, p‐c‐Fos, and p‐c‐Jun expression levels and a significant increase in ROS and apoptosis levels. HSP90AB1 overexpression significantly inhibited CAP‐induced T cell apoptosis by increasing the p‐Akt, SMARCC1, p‐c‐Fos, and p‐c‐Jun expression levels and reducing the ROS level. In conclusion, HSP90AB1 is a key target of CAP‐induced T cell apoptosis via Akt/SMARCC1/AP‐1/ROS axis, which provides a novel understanding of CAP‐induced T cell apoptosis and lays the experimental foundation for further exploring CAP as an immunosuppressant with antitumor effects to optimize the medication regimen for transplantation patients.