Mechanism of apoptosis induced in hepatoma G2 (HepG2) cell lines by Tinospora crispa: targeting signalling of the insulin-like growth factor (IGF) system and the insulin signalling (IS) pathway

Abstract

IntroductionHepatoma G2 (HepG2) cell line proliferation is controlled by insulin-like growth factor (IGF) signalling system. It is affected by exaggeration of self-producing IGF-1 ligand and disruption of the insulin signalling (IS) pathway which are later inhibit apoptotic activity. Tinospora crispa, a local herbal plant used as folklore medicine, contains natural insulin enhancer and possesses antiproliferative effects. The plant will be used in the study to observe its effect in restoring physiological function of the IS pathway, subsequently inducing apoptosis. ObjectiveTo evaluate the mechanism of T. crispa in compensating insulin resistance thus inducing apoptosis in HepG2 cancer cell line. MethodsThe protein expression of the IGF and IS pathways was investigated by the Western blotting method in order to track the compensatory mechanism. Results & DiscussionIGF-1R overexpression in HepG2 impaired insulin-induced AKT phosphorylation thus inactivated glucose intake through GLUT4. After treated with T. crispa crude methanolic extract, IGF-1R function of the cells was downregulated (p< 0.002). Meanwhile, apoptosis was induced through the increased of Bad (p<0. 04), caspases 8 (p<0.01), caspase 9 (p<0.02) and caspase 3 (p<0.01) protein expression. Concomitantly, it diminished the anti-apoptosis protein, Bcl-2 (p>0.32). The extract permitted the function of the IS pathway of HepG2 by enhancing insulin-induced autophosphorylation (PY20) on the ß – insulin receptor (IR-β) (p<0.03). Therefore, T. crispsa stimulated phosphorylation of IRS, and increased protein expressions of Akt and GAPDH (p<0.001). The condition was further improved glucose uptake (GLUT4) (p<0.01) process in the cells. ConclusionTinospora crispa has the potential as an anti-cancer agent via targeting insulin-like growth factor system and insulin signalling pathway in HepG2 cancer cell line.