Activation of Phosphatidylinositol 3-Kinase/Akt Signaling Pathway Mediates Acquired Resistance to Sorafenib in Hepatocellular Carcinoma Cells

Abstract

Hepatocellular carcinoma (HCC) is one of the most common potentially lethal human malignancies worldwide. Sorafenib, a tyrosine kinase inhibitor, was recently approved by the United States Food and Drug Administration for HCC. In this study, we established two sorafenib-resistant HCC cell lines from Huh7, a human HCC cell line, by long-term exposure of cells to sorafenib. Sorafenib induced significant apoptosis in Huh7 cells; however, Huh7-R1 and Huh7-R2 showed significant resistance to sorafenib-induced apoptosis at the clinical relevant concentrations (up to 10 M). Thorough comparisons of the molecular changes between Huh7 and resistant cells showed that the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway played a significant role in mediating acquired resistance to sorafenib in Huh7-R1 and Huh7-R2 cells. Phospho-Akt and p85 (a regulatory subunit of PI3K) were up-regulated, whereas tumor suppressor phosphatase and tensin homolog were down-regulated in these resistant cells. In addition, ectopic expression of constitutive Akt in Huh7 demonstrated similar resistance to sorafenib. The knockdown of Akt by RNA interference reversed resistance to sorafenib in Huh7-R1 cells, indicating the importance of Akt in drug sensitivity. Furthermore, the combination of 8-[4-(1-aminocyclobutyl)phenyl]-9-phenyl-1,2,4-triazolo[3,4-f][1,6]naphthyridin-3(2H)-one dihydrochloride (MK-2206), a novel allosteric Akt inhibitor, and sorafenib restored the sensitivity of resistant cells to sorafenib-induced apoptosis. In conclusion, activation of PI3K/Akt signaling pathway mediates acquired resistance to sorafenib in HCC, and the combination of sorafenib and MK-2206, an Akt inhibitor, overcomes the resistance at clinical achievable concentrations.

Inhibition of insulin‐like growth factor 1 receptor enhances the efficacy of sorafenib in inhibiting hepatocellular carcinoma cell growth and survival

“…4A), even when phosphorylation of AKT was increased by sorafenib treatment in HepG2 and Huh7 cells (Fig. 4A); this is consistent with results reported by other groups 5. Notably, the level of phosphorylated ERK was not further decreased by ceritinib in HCC cells treated with a combination of ceritinib and sorafenib compared to such cells treated with sorafenib alone (Fig.…”

“…Although sorafenib inhibits multiple kinase activities to suppress tumor angiogenesis and proliferation, other signaling pathways, such as PI3K/AKT, which sorafenib does not inhibit at low or even higher doses, contribute to cell growth and survival in sorafenib‐acquired resistant cells 5. The IGF1R signal pathway has been reported to be enriched in sorafenib‐acquired resistant tumor cells 27.…”

“…Sorafenib suppresses tumor proliferation and angiogenesis by inhibiting multiple serine/threonine and receptor tyrosine kinases, including serine/threonine‐protein kinase Raf‐1 (or c‐Raf), wild‐type and mutant B‐Raf, vascular endothelial growth factor receptor (VEGFR)‐1, VEGFR‐2, VEGFR‐3, platelet‐derived growth factor receptor β, tyrosine‐protein kinase Kit (c‐KIT), FMS‐like tyrosine kinase 3 (FLT‐3), and proto‐oncogene tyrosine‐protein kinase receptor Ret (RET) 4. However, other signaling pathways that sorafenib fails to inhibit can contribute to cell growth and survival in sorafenib‐acquired resistant cells, such as the phosphatidylinositol 3‐kinase (PI3K)/protein kinase B (AKT) signaling pathway 5. Therefore, combination drug treatment to inhibit the remaining active cell survival and growth pathways appears to be a promising approach to improve sorafenib efficacy 6, 7…”

Meta-analysis of the Efficacy of Sorafenib for Hepatocellular Carcinoma

“…It was used in renal cell carcinoma first, which prolongs neutral progression free survival time from 2.8 months to 5.5 months (Escudier et al, 2007). Based on further investigation, sorafenib improves the survival of patients with advanced hepatocellular carcinoma (HCC) (HuitzilMelendez et al, 2008;Chen et al, 2011). In the present paper, OS, TTP, TTSP, DCR and adverse reactions in clinical randomized controlled trials were summarized and assessed to confirm the efficacy of sorafenib in HCC therapy, providing clinical practice guidelines of evidencebased-medicine.…”

Quantitative proteomics and phosphoproteomics on serial tumor biopsies from a sorafenib-treated HCC patient

“…Sorafenib is largely cytostatic (6), suggesting that intrinsic resistance is more common in tumors, although some reports describe tumor shrinkage upon sorafenib treatment (7). Studies involving HCC cell lines or immunohistochemical staining of tumor sections revealed that sorafenib resistance correlates with the up-regulation of several signaling pathways, including the mammalian target of rapamycin (mTOR) pathway as assayed by S6 S235/236 (8) and Akt S473 phosphorylation (9). Other potential resistance mechanisms involve epithelial-to-mesenchymal transition (EMT) and autophagy (10, 11).…”