Ras pathway activation in hepatocellular carcinoma and anti-tumoral effect of combined sorafenib and rapamycin in vivo

Abstract

Background/Aims-The success of sorafenib in the treatment of advanced hepatocellular carcinoma (HCC) has focused interest on the role of Ras signaling in this malignancy. We investigated the molecular alterations of the Ras pathway in HCC and the antineoplastic effects of sorafenib in combination with rapamycin, an inhibitor of mTOR pathway, in experimental models.Methods-Gene expression (qRT-PCR, oligonucleotide microarray), DNA copy number changes (SNP-array), methylation of tumor suppressor genes (methylation-specific PCR) and protein activation (immunohistochemistry) were analysed in 351 samples. Anti-tumoral effects of combined therapy targeting the Ras and mTOR pathways were evaluated in cell lines and HCC xenografts.Results-Different mechanisms accounted for Ras pathway activation in HCC. H-ras was upregulated during different steps of hepatocarcinogenesis. B-raf was overexpressed in advanced tumors and its expression was associated with genomic amplification. Partial methylation of RASSF1A and NORE1A was detected in 89% and 44% of tumors respectively, and complete methylation was found in 11 and 4% of HCCs. Activation of the pathway (pERK immunostaining) was identified in 10.3% of HCC. Blockade of Ras and mTOR pathways with sorafenib and rapamycin Conclusions-Ras activation results from several molecular alterations, such as methylation of tumor suppressors and amplification of oncogenes (B-raf). Sorafenib blocks signaling and synergizes with rapamycin in vivo, preventing tumor progression. These data provide the rationale for testing this combination in clinical studies.

Everolimus Augments the Effects of Sorafenib in a Syngeneic Orthotopic Model of Hepatocellular Carcinoma

“…Our positive results contrast with those of Newell and colleagues, who found no difference in tumor growth with this combination (14). This disparity is perhaps explained by our propitious choice of an orthotopic syngeneic model, which is a closer representation of HCC than the xenograft model chosen by previous investigators (7,14,15) HCC is a hypervascular tumor, relying on angiogenesis for growth (16). Focal hypoxia is a potent angiogenic stimulus and both everolimus and sorafenib treatment regimens exerted their antitumoral effects within a local environment that was subject to such stimuli, as shown by the increased expression of HIF-1a in all treated tumors (Fig.…”

“…Everolimus also retains its antitumoral potency in vivo when administered sequentially after sorafenib, a finding that carries important clinical implications. Our positive results contrast with those of Newell and colleagues, who found no difference in tumor growth with this combination (14). This disparity is perhaps explained by our propitious choice of an orthotopic syngeneic model, which is a closer representation of HCC than the xenograft model chosen by previous investigators (7,14,15) HCC is a hypervascular tumor, relying on angiogenesis for growth (16).…”

Oleate-mediated activation of phospholipase D and mammalian target of rapamycin (mTOR) regulates proliferation and rapamycin sensitivity of hepatocarcinoma cells

“…Indeed, in some cancer cells rapamycin is effective in inhibiting mTOR, but with a benefit that is limited by the concomitant relief of the Ras/mitogen-activated protein kinase (MAPK) pathway from an mTORC1-initiated negative feedback loop [32]. This suggested a promising approach to HCC therapy consisting of a combination of mTORC1 and Ras/MAPK inhibitors [33]. Additional explanations for rapamycin resistance may involve mTORC2-dependent outputs, because this complex, which is involved in PKB activation by phosphorylation of serine 473, has been shown to be less sensitive to rapamycin inhibition compared with mTORC1 [12].…”

Biotinylated polyurethane-urea nanoparticles for targeted theranostics in human hepatocellular carcinoma

“…In this context, tyrosine kinase receptors are highaffinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones. These receptors have a critical role in the development and progression of many types of cancer and are being used as therapeutic candidates for multi-target drug therapy in HCC [15]. Therefore the use of drugs with multiple antitumor effects appears to be a promising approach for the treatment of HCC.…”