Beclin-1 as a neutrophil-specific immune checkpoint

Targeting autophagy and beyond: Deconvoluting the complexity of Beclin-1 from biological function to cancer therapy

Beclin-1 is the firstly-identified mammalian protein of the autophagy machinery, which functions as a molecular scaffold for the assembly of PI3KC3 (class III phosphatidylinositol 3 kinase) complex, thus controlling autophagy induction and other cellular trafficking events. Notably, there is mounting evidence establishing the implications of Beclin-1 in diverse tumorigenesis processes, including tumor suppression and progression as well as resistance to cancer therapeutics and CSC (cancer stem-like cell) maintenance. More importantly, Beclin-1 has been confirmed as a potential target for the treatment of multiple cancers. In this review, we provide a comprehensive survey of the structure, functions, and regulations of Beclin-1, and we discuss recent advances in understanding the controversial roles of Beclin-1 in oncology. Moreover, we focus on summarizing the targeted Beclin-1-regulating strategies in cancer therapy, providing novel insights into a promising strategy for regulating Beclin-1 to improve cancer therapeutics in the future.

Piceatannol enhances Beclin-1 activity to suppress tumor progression and its combination therapy strategy with everolimus in gastric cancer

The effects and regulation of Beclin-1-an autophagy-related protein-have not been fully defined, however, a negative correlation has been reported between Beclin-1 expression and carcinogenesis. Meanwhile, no compound has been shown to directly inhibit its activity. Here, we evaluate piceatannol, a naturally occurring polyphenolic compound, as a potential targeting agonist of Beclin-1, to assess its efficacy as an antitumor agent against gastric cancer. More specifically, we determine the effects of piceatannol treatment on cell viability using a monitoring system and colony forming assay. Piceatannol was found to efficiently inhibit the proliferation of several human gastric cancer cell lines. Autophagic flux is increased by piceatannol treatment, and correlates with inhibition of cell proliferation and colony formation. Additionally, microscale thermophoresis and surface plasmon resonance results show a direct interaction between piceatannol and Beclin-1, which reduces the phosphorylation activity of Beclin-1 at the Ser-295 site. Notably, piceatannol impairs the binding of Beclin-1 to Bcl-2 and enhances the recruitment of binding of UV radiation resistance-associated gene protein, which further triggers Beclin-1-dependent autophagy signaling. An increase in autophagic activity via treatment with the mTOR inhibitor, everolimus, effectively sensitizes piceatannol-induced antitumor effects. Xenograft models confirmed that piceatannol inhibits tumor development and elicits a potent synergistic effect with everolimus in vivo. Taken together, the findings of this study strongly support the application of combinatorial piceatannol and everolimus therapy in future clinical trials for gastric cancer patients.

Immunohistochemical Analysis of the Beclin-1 Expression Predicts the Progression of Oral Squamous Cell Carcinoma

Background: Autophagy is a cellular process responsible for maintaining homeostasis; a dysregulation of this process is involved in the development and progression of neoplasms. Beclin-1 is one of the major proteins linked to autophagy. However, the data regarding the association between the role of Beclin-1 and the progression of Oral Squamous Cell Carcinoma (OSCC) are rather low. For this reason, the objective of this study is to evaluate, through immunohistochemical techniques, the prognostic role of the expression of Beclin-1 autophagy marker in patients with OSCC. Methods: This is a single-centre retrospective study that includes patients with OSCC admitted to the Maxillofacial Unit of “Magna Graecia” University between January 2019 and September 2020. All the samples obtained from surgery were treated with anti Beclin-1 antibodies and subjected to immunohistochemical methods. Results: A total of 26 samples were analysed and the following variables were evaluated for each: percentage of positive Beclin-1 expression by tumour cells, signal strength of tumour cells, and total score. The variables considered were first normalised according to the D’Agostino and Pearson test, then analysed using the Pearson linear correlation coefficient: a statistically significant correlation was found between the parameters infiltration-intensity (p = 0.0088), infiltration-percent (p = 0.0123), intensity-total score (p = 0.0060). Conclusions: The immunohistochemical evaluation of Beclin-1 revealed a statistically significant correlation between the intensity of the molecule’s expression and a greater degree of infiltration of the neoplasm. Beclin-1 can, therefore, be considered a valid prognostic index of disease.

[IL-17A/lL-17RA reduces cisplatin sensitivity of ovarian cancer SKOV3 cells by regulating autophagy]

OBJECTIVE

To investigate the effect of interleukin-17A (IL-17A) on chemosensitivity of ovarian cancer cells to cisplatin (DDP) and explore the mechanism in light of autophagy regulation.

METHODS

Ovarian cancer SKOV3 cells cultured in vitro were treated with different concentrations of DDP (1-20 μg/mL). MTT assay was used to observe the changes in proliferation of the treated cells and the effect of treatment with 100 ng/mL IL-17A for 24 h on DDP-induced apoptosis of SKOV3 cells. We then examined the expression of IL-17A receptor (IL-17RA) in SKOV3 cells using flow cytometry. Annexin V-FITC/PI double staining was used to detect the cell apoptosis rate, and early apoptosis of the cells was detected with JC-1 assay. A neutralizing monoclonal antibody (mAb) against IL-17RA was used to block IL-17RA. We also observed the effects of IL-17RA silencing mediated by a siRNA targeting IL-17RA (siRNA-IL-17RA) and treatment with 3-methyladenine (3-MA) for inhibiting autophagy on DDP-induced apoptosis of SKOV3 cells. The expressions of apoptosis-related proteins (Bcl-2, Bax, and cleaved caspase-3) and autophagy-related proteins (P62 and Beclin-1) in the treated cells were detected using Western blotting.

RESULTS

DDP increased the expression of IL-17RA in ovarian cancer SKOV3 cells. Treatment with IL-17A significantly reduced the susceptibility of SKOV3 cells to cisplatin-induced apoptosis (P < 0.05). DDP obviously augmented the expression of Beclin-1 and reduced the autophagy degradation substrate P62 protein in the cells (P < 0.05). IL-17A/IL-17RA strongly enhanced the DDPinducted autophagy of the cells (P < 0.05). Blocking autophagy with 3-MA significantly increased DDP- induced apoptosis of SKOV3 cells with IL-17RA silencing, lowered the expression of Bcl-2 and enhanced Bax expression in the cells (P < 0.05).

CONCLUSIONS

IL-17A/IL-17RA can decrease chemosensitivity of SKOV3 cells to DDP by upregulating DDP-induced autophagy.

MicroRNA-874-5p regulates autophagy and proliferation in pulmonary artery smooth muscle cells by targeting Sirtuin 3

Autophagy is a major cause of pathological vascular remodeling under hypoxic pulmonary hypertension (PH). Sirtuin 3 (Sirt 3) has recently been reported to be involved in the regulation of autophagy, however, its role as an autophagy regulator during hypoxic PH, particularly the molecular mechanism, remains poorly understood. In the present study, Western blot, immunohistochemistry, immunofluorescence, bromodeoxyuridine incorporation and cell cycle analyses were performed to elucidate the underlying mechanism of hypoxia-induced autophagy and cell proliferation with respect to Sirt 3. We observed that the Sirt 3 expression was decreased under hypoxia and that Sirt 3 overexpression significantly inhibited the effects of hypoxia on autophagy. Next, we investigated the mechanistic role of microRNAs in Sirt 3-associated autophagy under hypoxic conditions, with luciferase reporter, microscale thermophoresis and RNA immunoprecipitation assays, results confirming that Sirt 3 is a direct target of miR-874-5p. Furthermore, miR-874-5p was upregulated following hypoxia, and miR-874-5p depletion in turn inhibited autophagy and consequently suppressed abnormal smooth muscle cell proliferation. These findings provide insight into the contribution of the miR-874-5p/Sirt 3 cascade with regard to changes in autophagy and proliferation associated with PH.