Ablation of Survivin in T Cells Attenuates Acute Allograft Rejection after Murine Heterotopic Heart Transplantation by Inducing Apoptosis.

Although studies in oncology have well explored the pharmacological effects of Birc5, little is known about its role in allogeneic T-cell responses. Therefore, the present study used a mouse model of acute heart allograft rejection to investigate the protective effect and mechanism of conditional knockout of Birc5 in T cells. Survivin (encoded by Birc5) was up-regulated in T cells activated in vivo and in vitro. Deletion of Birc5 in T cells attenuated acute heart allograft rejection by reducing the ratio of effector to naive T cells and Th1 to Tregs. In addition, deletion of Birc5 had no noticeable effect on proliferation but on apoptosis and the secretion of IFN-γ. The results revealed a significant increase in the percentage of Annexin V positive CD4+ T cells in the Birc5-/- group, compared to the WT. Moreover, there was significant increase in early apoptotic alloreactive T cells in Birc5-/- mice and this was partly mediated by caspase-3. Furthermore, treatment with YM155 inhibited acute heart allograft rejection in vivo and increased T-cell apoptosis in healthy human PBMCs in vitro. The results highlight a potential therapeutic target for the prevention and treatment of acute transplant rejection.

BIRC5 is a prognostic biomarker associated with tumor immune cell infiltration.

BIRC5 is an immune-related gene that inhibits apoptosis and promotes cell proliferation. It is highly expressed in most tumors and leads to poor prognosis in cancer patients. This study aimed to analyze the relationship between the expression level of BIRC5 in different tumors and patient prognosis, clinical parameters, and its role in tumor immunity. Genes co-expressed with BIRC5 were analyzed, and functional enrichment analysis was performed. The relationship between BIRC5 expression and the immune and stromal scores of tumors in pan-cancer patients and the infiltration level of 22 tumor-infiltrating lymphocytes (TILs) was analyzed. The correlation of BIRC5 with immune checkpoints was conducted. Functional enrichment analysis showed that genes co-expressed with BIRC5 were significantly associated with the mitotic cell cycle, APC/C-mediated degradation of cell cycle proteins, mitotic metaphase, and anaphase pathways. Besides, the high expression of BIRC5 was significantly correlated with the expression levels of various DNA methyltransferases, indicating that BIRC5 regulates DNA methylation. We also found that BIRC5 was significantly correlated with multiple immune cells infiltrates in a variety of tumors. This study lays the foundation for future research on how BIRC5 modulates tumor immune cells, which may lead to the development of more effective targeted tumor immunotherapies.

Cytoproliferative effect of low dose alpha radiation in human lung cancer cells is associated with connexin 43, caveolin-1, and survivin pathway.

PURPOSE: High LET including alpha radiation-based approaches have been proved as a promising mode for cancer therapy owing to their biophysical and radiobiological advantages compared to photon beams. Studies pertaining to effect of α-radiation on cancer cells are limited to cytotoxic high doses. MATERIALS AND METHODS: In this study, human lung adenocarcinoma (A549) cells were α-irradiated using 241Am α-irradiator and effects of low dose of alpha radiation on these cells was studied under in vitro and in vivo conditions. RESULTS: Clonogenic and other assays showed increased cellular proliferation at lower doses (1.36 and 6.8 cGy) but killing at higher doses (13.6-54.4 cGy). Further studies at low dose of alpha (1.36 cGy) showed increased TGF-ß1 in the conditioned medium (CM) at early time point (24 h) but CM replacement did not affect the clonogenic survival. In these cells, increased phosphorylation of connexin 43 was correlated with decrease in gap-junction communication observed by dye transfer co-culture experiment. A decrease in caveolin-1 but increase in survivin expression was observed in low dose α-irradiated cells. An increase in cyclinD1 and decrease in Bcl-2, the target proteins of survivin, was observed in these cells. Low dose α-irradiated cancer cells transplanted in SCID mice showed significantly higher tumor volume, which was accompanied with an increased fraction of mitotic and PCNA/Ki67 positive cells in these tumor tissues. CONCLUSIONS: Taken together, our results suggest an increase in proliferation and tumor volume at in vitro and in vivo levels, respectively, when A549 cells were irradiated with low dose of α-radiation. These findings may be relevant for a better understanding of radiobiological processes during high LET-based cancer radiotherapy.

Anti-apoptotic proteins in the autophagic world: an update on functions of XIAP, Survivin, and BRUCE.

X-linked inhibitor of apoptosis protein (XIAP), survivin, and BRUCE are members of the inhibitor-of-apoptosis protein (IAP) family known for their inhibitory effects on caspase activity and dysregulation of these molecules has widely been shown to cause embryonic defects and to promote tumorigenesis in human. Besides the anti-apoptotic functions, recent discoveries have revealed that XIAP, survivin, and BRUCE also exhibit regulatory functions for autophagy in cells. As the role of autophagy in human diseases has already been discussed extensively in different reviews; in this review, we will discuss the emerging autophagic role of XIAP, survivin, and BRUCE in cancer cells. We also provide an update on the anti-apoptotic functions and the roles in maintaining DNA integrity of these molecules. Second mitochondria-derived activator of caspases (Smac) is a pro-apoptotic protein and IAPs are the molecular targets of various Smac mimetics currently under clinical trials. Better understanding on the functions of XIAP, survivin, and BRUCE can enable us to predict possible side effects of these drugs and to design a more "patient-specific" clinical trial for Smac mimetics in the future.

Mitochondrial membrane depolarization enhances TRAIL-induced cell death in adult human granulosa tumor cells, KGN, through inhibition of BIRC5.

BACKGROUND: Cellular metabolic changes that accompany malignant transformation have been heralded as hallmark features of cancer. However, metabolic signatures between neoplasms can be unique, allowing for distinctions in malignancy, invasion and chemoresistance between cancer types and subtypes. Mitochondria are central metabolic mediators, as cellular bioenergetics veers from oxidative phosphorylation to glycolysis. Herein, we evaluate the role of mitochondria in maintenance of cellular metabolism, proliferation, and survival in the adult granulosa tumor cell line, KGN, as well as three epithelial ovarian cancer cell lines to determine distinctions in specific features. RESULTS: Notably, KGN cells were susceptible to TRAIL- and cisplatin-induced death following pretreatment with the metabolic inhibitor FCCP, but not oligomycin A. Collapse of mitochondrial membrane potential was found concomitant with cell death via apoptosis, independent from extrinsic canonical apoptotic routes. Rather, treatment with FCCP resulted in elevated cytochrome c release from mitochondria and decreased responsiveness to BIRC5. Following knockdown of BIRC5, mitochondrial membrane depolarization further sensitized KGN cells to induction of apoptosis via TRAIL. CONCLUSIONS: These results indicate an essential role, distinct from metabolism, for mitochondrial membrane potential in KGN cells to sense and respond to external mediators of apoptotic induction.