Abstract
Background: Hepatocellular carcinoma (HCC) represents a major health burden with limited curative treatment options. There is a substantial unmet need to develop innovative approaches to impact the progression of advanced HCC. Haprolid is a novel natural component isolated from myxobacteria. Haprolid has been reported as a potent selective cytotoxin against a panel of tumor cells in recent studies including HCC cells. The aims of this study are to evaluate the antitumor effect of haprolid in HCC and to understand its underlying molecular mechanisms. Methods: The efficacy of haprolid was evaluated in human HCC cell lines (Huh-7, Hep3B and HepG2) and xenograft tumors (NMRI-Foxn1nu mice with injection of Hep3B cells). Cytotoxic activity of haprolid was determined by the WST-1 and crystal violet assay. Wound healing, transwell and tumorsphere assays were performed to investigate migration and invasion of HCC cells. Apoptosis and cell-cycle distribution were measured by flow cytometry. The effects of haprolid on the Rb/E2F and Akt/mTOR pathway were examined by immunoblotting and immunohistochemistry. Results: haprolid treatment significantly inhibited cell proliferation, migration and invasion in vitro. The epithelial–mesenchymal transition (EMT) was impaired by haprolid treatment and the expression level of N-cadherin, vimentin and Snail was downregulated. Moreover, growth of HCC cells in vitro was suppressed by inhibition of G1/S transition, and partially by induction of apoptosis. The drug induced downregulation of cell cycle regulatory proteins cyclin A, cyclin B and CDK2 and induced upregulation of p21 and p27. Further evidence showed that these effects of haprolid were associated with Rb/E2F downregulation and Akt/mTOR inhibition. Finally, in vivo nude mice experiments demonstrated significant inhibition of tumor growth upon haprolid treatment. Conclusion: Our results show that haprolid inhibits the growth of HCC through dual inhibition of Rb/E2F and Akt/mTOR pathways. Therefore, haprolid might be considered as a new and promising candidate for the palliative therapy of HCC.
Highlights
Hepatocellular carcinoma (HCC) is one of the most common cancers globally and its incidence and mortality rate have still been increasing over the past decades [1]
We report for the first time about the positive antitumor effect of haprolid, a novel natural polyketide–peptide hybrid, in HCC models, both in vitro and in vivo through dual inhibition of Rb/E2F
Our results indicate that haprolid treatment leads to a strong inhibitory effect of cell growth, migration and invasion in human HCC cell lines
Summary
Hepatocellular carcinoma (HCC) is one of the most common cancers globally and its incidence and mortality rate have still been increasing over the past decades [1]. Haprolid has been reported as an effective cytotoxic compound against many tumor cell lines including HCC cells and its IC50 values are within the nanomolar range [5,6]. This study is the first report for the application of haprolid in an in vitro and in vivo model of HCC. Haprolid has been reported as a potent selective cytotoxin against a panel of tumor cells in recent studies including HCC cells. The aims of this study are to evaluate the antitumor effect of haprolid in HCC and to understand its underlying molecular mechanisms. Methods: The efficacy of haprolid was evaluated in human HCC cell lines (Huh-7, Hep3B and HepG2) and xenograft tumors (NMRI-Foxn1nu mice with injection of Hep3B cells). Results: haprolid treatment significantly inhibited cell proliferation, migration and invasion in vitro. The epithelial–mesenchymal transition (EMT) was impaired by haprolid treatment and the expression level of N-cadherin, vimentin and
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