Abstract 913: Erufosine simultaneously induces apoptosis and autophagy by modulating the mTOR signaling pathway in oral squamous cell carcinoma

Abstract

Abstract Erufosine (erucylphospho-N, N, N-trimethylpropylammonium) is an i.v. injectable alkylphosphocholine analog, which is active against various hematological malignancies in vitro. In this study, we reveal activity in oral squamous carcinoma cell lines and down-regulation of the mTOR signaling cascade as novel mechanism underlying the anticancer activity of erufosine. To that purpose, four oral squamous cell carcinoma cell lines (Cal27, FaDu, SCC9 and SCC25) were exposed to erufosine and assessed for modulation of cell proliferation, colony formation, induction of autophagy/apoptosis, cell cycle distribution, and signaling of the mTOR pathway. In addition, combination effects of erufosine with decreased p-mTOR expression or cytotoxic drugs were investigated. Erufosine showed dose-dependent cytotoxicity in all cell lines as observed by MTT and clonogenicity assays. It simultaneously induced both autophagy and apoptosis via conversion of LC3BI to LC3BII, caspase 3/7 activation and PARP cleavage, respectively. In addition, G2 cell cycle arrest was observed along with cyclin D1 down-regulation. Subsequently, we observed that erufosine readily down-regulated in a dose-dependent manner the phosphorylation of components of the mTOR signaling pathway, like p-Akt, p-Raptor, p-mTOR, and its downstream substrates p-p70S6K and p-4EBP1. p-PRAS40 was reduced to undetectable levels at the highest concentrations of erufosine. Moreover, blockage of p-mTOR expression by siRNA, increased tumor cell sensitivity to erufosine and the resulting antiproliferative effect was comparable to the respective combination with cisplatin but superior to that with rapamycin. Further, erufosine showed additive tumor cell cytotoxicity in combination with 5-flourouracil and cisplatin. In conclusion, these data indicate that erufosine induces apoptosis, autophagy, cell cycle arrest and down-regulates mTOR signaling in oral cancer cell lines. Thus, it has potential as an anti-oral cancer drug either alone or in combination with other chemotherapeutic agents. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 913. doi:1538-7445.AM2012-913