Head and neck cancer ranks amongst the sixth most prevalent cancers worldwide and oral squamous cell carcinomas (OSCC) constitute 90% thereof. Erufosine is an ether-lipid-derived synthetic compound belonging to alkylphosphocholines (APCs), which has been shown to inhibit the proliferation of OSCC cells. It simultaneously induces apoptosis and autophagy by modulating the Akt-mTOR signaling pathway, however, its exact mechanism of action is not fully understood. Here, we describe the activity of erufosine on the expression of cell cycle related genes in OSCC cells.

The anti-proliferative effect of erufosine in cells of two human OSCC cell lines, HN-5 and SCC-61, was determined by MTT assay after 24h, 48h and 72h exposure. Based on these results, HN-5 cells were exposed to erufosine at concentrations corresponding to IC25, IC50 and IC75 concentrations, and then their mRNA was isolated and analyzed by Illumina Chip array. Gene expression modulation was confirmed qRT-PCR and Western blot. Gene set enrichment analysis was performed to identify core KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways and GO (Gene Ontology) terms. In addition, erufosine’s effect on cell cycle distribution and colony formation was determined as well as its antineoplastic effect on respective xenografts in nude mice.

As shown from TCGA data, cell cycle deregulation in HNSCC ranks amongst the top three out of 24 different types of cancers. In line with this, the median expression of cell cycle genes was higher than that of other genes within HNSCC. We also looked at the median gene expression of all CDKs and cyclins in 519 HNSCC patient samples from TCGA and found that the expression levels were higher than the global gene expression. This was in agreement with IHC staining of CCND1 in tumors from 30 South East Asian HNSCC patients. Furthermore, increased CCND1 and CDK6 expression levels from TCGA data had negative implication on patient survival. In our experimental results erufosine caused a dose dependent growth inhibition of OSCC cell lines and negative enrichment of genes related to

the cell cycle process. Our microarray findings revealed that cyclins and CDKs were downregulated in a dose dependent manner in response to erufosine exposure. These findings were verified at both, mRNA and protein levels. Erufosine not only caused a massive G2M block but also inhibition of colony formation thus preparing the OSCC cells to undergo apoptosis. We are the first to show that erufosine inhibited tumor growth in vivo in a HNSCC xenograft model and caused downregulation of cyclinD1, CDK4 and CDK6 in lesions of the animals.

These findings collectively show the potential of erufosine to be used as a cell cycle inhibitor in HNSCC progression and support the future evaluation of erufosine as a therapeutic approach in cancer treatment alone, or in combination.

Citation Format: Shariq S. Ansari, Ashwini K. Sharma, Michael Zepp, Frank Bergmann, Rainer König, Martin R. Berger. Downregulation of cell cycle genes in HNSCC by erufosine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2339. doi:10.1158/1538-7445.AM2017-2339