E3 ubiquitin ligase Cbl-b potentiates the apoptotic action of arsenic trioxide by inhibiting the PI3K/Akt pathway

Abstract

Arsenic trioxide (ATO) is a strong inducer of apoptosis in malignant hematological cells. Inducible phosphatidyl inositol 3 kinase (PI3K)-Akt activation promotes resistance to ATO. In the present study, we evaluated whether E3 ubiquitin ligase Cbl-b, a negative regulator of PI3K activation, is involved in the action of ATO. The effect of ATO on cell viability was measured by the Trypan blue exclusion assay or by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was determined by flow cytometry and protein expression was assayed by Western blotting. ATO decreased the viability of HL60 cells and induced cellular apoptosis, which was accompanied by transient activation of Akt. The PI3K/Akt inhibitor, LY294002, significantly increased ATO-induced apoptosis (P < 0.05). In addition, ATO up-regulated the expression of Cbl-b proteins. Furthermore, ATO inhibited cell viability with an IC 50 of 18.54 μM at 24 h in rat basophilic leukemia-2H3 cells. ATO induced cellular apoptosis with transient activation of Akt and Cbl-b was also up-regulated. Rat basophilic leukemia-2H3 cells transfected with a dominant negative (DN) Cbl-b mutation showed overexpression of Cbl-b (DN) and enhanced Akt activation. Compared with cells transfected with vector, ATO-induced apoptosis was decreased and G2/M phase cells were increased at the same concentration (P < 0.05). The PI3K/Akt inhibitor, LY294002, re-sensitized Cbl-b (DN) overexpressing cells to ATO and reversed G2/M arrest (P < 0.05). Taken together, these results suggest that Cbl-b potentiates the apoptotic action of ATO by inhibition of the PI3K/Akt pathway.

53BP1 suppresses tumor growth and promotes susceptibility to apoptosis of ovarian cancer cells through modulation of the Akt pathway

“…Yet, further studies are needed to confirm that other proteins are involved in the anti-apoptosis caspase pathway in relation to the effect of the alteration of 53BP1 in ovarian cancer cells. Coincident with our results, recent studies have shown that the downregulation of Akt has an impact on inducing G 2 /M arrest (22–24). P21 waf1/Cip1 is an inhibitor of CDK (cyclin-dependent kinase) in mammalian cells and the transcriptional target of P53 (30).…”

“…Several lines of evidence suggest that activated p-Akt serves as a multifunctional regulator of cellular processes, including cell proliferation, cell cycle and apoptosis (19–21). Research has shown that modulation of the genetic background of cancer cells or therapeutic interventions may induce G 2 /M arrest accompanied by the downregulation of p-Akt (22–24). …”

Ubiquitin ligase Cbl-b represses IGF-I-induced epithelial mesenchymal transition via ZEB2 and microRNA-200c regulation in gastric cancer cells

“…Almost all cellular processes are regulated by the ubiquitin proteasome system, including EMT [12]. Cbl-b is the second member of the E3 ubiquitin ligase Cbl family, and our group and others have revealed that Cbl-b regulates cancer cell proliferation, drug sensitivity, and migration [13-15]. Knock-down of Cbl-b enhances epidermal growth factor-induced disruption of human mammary epithelial cell adherens junctions (AJs) and cell motility [16].…”

Immunohistochemical Analysis and Pathological Assessment of B-Cbl Proto-Oncogene in Gastric Carcinoma Cells

“…Cbl-b is a second member of the E3 ubiquitin ligase Cbl family, some studies have revealed that Cbl-b regulates gastric cancer cell proliferation, drug sensitivity and also migration [1,7,8]. In addition, Cbl-b can degrade as well IGF-I signaling intermediate IRS-1 and decrease protein synthesis in unloading-induced muscle atrophy [9].…”