Non-visual arrestins (β-arrestins) are endocytic proteins that mediate agonist activated GPCRs internalization and signaling pathways in an independent manner. The involvement of β-arrestins in cancer invasion and metastasis is increasingly reported. So, it is hypothesized that inhibition of β-arrstins may diminish the survival chances of cancer cells. This study aimed to evaluate the in vitro impact of inhibiting β-arrestins on the autophagic and/or apoptotic responsiveness of breast cancer cells.We used Barbadin to selectively inhibit β-Arr/AP2 interaction in AVP stimulated V2R receptor of triple negative breast cancer cells (MDA MB-231). Autophagy was assessed by the microtubule-associated protein 1 light chain 3-II (LC3II), apoptosis was measured by Annexin-V/PI staining and cell cycle distribution was investigated based upon the DNA content using ow cytometry. Barbadin reduced cell viability to 69.1% and increased the autophagy marker LC3 II and its autophagic effect disappeared in cells transiently starved in Earle's balanced salt solution (EBSS). Also, Barbadin mildly enhanced the expression of P62 mRNA and arrested 63.7% of cells in G0/G1 phase. In parallel, the drug induced apoptosis in 29.9% of cells (by AV/PI) and 27.8% of cells were trapped in sub-G1 phase. The apoptotic effect of Barbadin was enhanced when autophagy was inhibited by the PI3K inhibitor (Wortmannin).Conclusively, the data demonstrate the dual autophagic and apoptotic effects of β-βArr/AP2 inhibition in triple negative breast cancer cells. These observations nominate β-Arrs as selective targets in breast cancer treatment.Thus, this work was designed to explore the autophagic and apoptosis effects of the inhibition of β-Arr/AP2 interaction in hormonally stimulated breast cancer cells. Materials And MethodsKey Reagents: Barbadin (3-amino-5-(4-benzylphenyl)-3H,4H-thieno[2,3-d]pyrimidin-4-one) (Cat No. B118250), Arginine Vasopressin acetic acid salt (AVP) (Cat No. V991535) and Wortmannin (Cat No. W499400), were purchased from Toronto Research Chemicals, Toronto, Ontario, Canada). Trichostatin A (TSA) and dimethyl sulfoxide (DMSO) were from Sigma Chemicals, USA. Earle's balanced salt solution (EBSS) and other cell culture reagents (DMEM 4.5 g/L glucose with L glutamine, penicillin/streptomycin, fetal bovine serum (FBS) and Trypsin/EDTA) were from Lonza Pharma & Biotech. Cell culture and treatment MDA MB-231 cells [16] was generously provided by Department of Cancer Biology, NCI, Cairo University.Cells were cultured in Dulbecco's modi ed Eagle's Minimal Essential Medium (DMEM) supplemented with 10% heat inactivated FBS, 1% Penicillin/Streptomycin in a humidi ed atmosphere of 95% air and 5% CO 2 at 37 °C. Initially, cells were seeded with a low cell density then subcultured with particular densities in 100 mm, 6 wells, or 96 wells plates according to the experimental settings. Cell treatmentsAutophagy was induced by glucose oxygen deprivation, where cells were starved for 4 hours in EBSS, which does not contain nutrients nor growth factors, at...

Non-visual arrestins (β-arrestins) are endocytic proteins that mediate agonist activated GPCRs internalization and signaling pathways in an independent manner. The involvement of β-arrestins in cancer invasion and metastasis is increasingly reported. So, it is hypothesized that inhibition of β-arrstins may diminish the survival chances of cancer cells. This study aimed to evaluate the in vitro impact of inhibiting β-arrestins on the autophagic and/or apoptotic responsiveness of breast cancer cells. We used Barbadin to selectively inhibit β-Arr/AP2 interaction in AVP stimulated V2R receptor of triple negative breast cancer cells (MDA MB-231). Autophagy was assessed by the microtubule-associated protein 1 light chain 3-II (LC3II), apoptosis was measured by Annexin-V/PI staining and cell cycle distribution was investigated based upon the DNA content using flow cytometry. Barbadin reduced cell viability to 69.1% and increased the autophagy marker LC3 II and its autophagic effect disappeared in cells transiently starved in Earle's balanced salt solution (EBSS). Also, Barbadin mildly enhanced the expression of P62 mRNA and arrested 63.7% of cells in G0/G1 phase. In parallel, the drug induced apoptosis in 29.9% of cells (by AV/PI) and 27.8% of cells were trapped in sub-G1 phase. The apoptotic effect of Barbadin was enhanced when autophagy was inhibited by the PI3K inhibitor (Wortmannin). Conclusively, the data demonstrate the dual autophagic and apoptotic effects of β-βArr/AP2 inhibition in triple negative breast cancer cells. These observations nominate β-Arrs as selective targets in breast cancer treatment.