Objectives Evaluate the cytotoxicity and genotoxicity of short- and long-term e-cigarette vapor exposure on a panel of normal epithelial and head and neck squamous cell carcinoma (HNSCC) cell lines. Materials and Methods HaCaT, UMSCC10B, and HN30 were treated with nicotine-containing and nicotine-free vapor extract from two popular e-cigarette brands for periods ranging from 48 hours to 8 weeks. Cytotoxicity was assessed using Annexin V flow cytometric analysis, trypan blue exclusion, and clonogenic assays. Genotoxicity in the form of DNA strand breaks was quantified using the neutral comet assay and γ-H2AX immunostaining. Results E-cigarette-exposed cells showed significantly reduced cell viability and clonogenic survival, along with increased rates of apoptosis and necrosis, regardless of e-cigarette vapor nicotine content. They also exhibited significantly increased comet tail length and accumulation of γ-H2AX foci, demonstrating increased DNA strand breaks. Conclusion E-cigarette vapor, both with and without nicotine, is cytotoxic to epithelial cell lines and is a DNA strand break-inducing agent. Further assessment of the potential carcinogenic effects of e-cigarette vapor is urgently needed.

BackgroundAlcohol consumption is a well-established risk factor for head and neck squamous cell carcinoma (HNSCC); however, the molecular mechanisms by which alcohol promotes HNSCC pathogenesis and progression remain poorly understood. Our study sought to identify microRNAs that are dysregulated in alcohol-associated HNSCC and investigate their contribution to the malignant phenotype.MethodUsing RNA-sequencing data from 136 HNSCC patients, we compared the expression levels of 1,046 microRNAs between drinking and non-drinking cohorts. Dysregulated microRNAs were verified by qRT-PCR in normal oral keratinocytes treated with biologically relevant doses of ethanol and acetaldehyde. The most promising microRNA candidates were investigated for their effects on cellular proliferation and invasion, sensitivity to cisplatin, and expression of cancer stem cell genes. Finally, putative target genes were identified and evaluated in vitro to further establish roles for these miRNAs in alcohol-associated HNSCC.ResultsFrom RNA-sequencing analysis we identified 8 miRNAs to be significantly upregulated in alcohol-associated HNSCCs. qRT-PCR experiments determined that among these candidates, miR-30a and miR-934 were the most highly upregulated in vitro by alcohol and acetaldehyde. Overexpression of miR-30a and miR-934 in normal and HNSCC cell lines produced up to a 2-fold increase in cellular proliferation, as well as induction of the anti-apoptotic gene BCL-2. Upon inhibition of these miRNAs, HNSCC cell lines exhibited increased sensitivity to cisplatin and reduced matrigel invasion. miRNA knockdown also indicated direct targeting of several tumor suppressor genes by miR-30a and miR-934.ConclusionsAlcohol induces the dysregulation of miR-30a and miR-934, which may play crucial roles in HNSCC pathogenesis and progression. Future investigation of the alcohol-mediated pathways effecting these transformations will prove valuable for furthering the understanding and treatment of alcohol-associated HNSCC.Electronic supplementary materialThe online version of this article (doi:10.1186/s12943-015-0452-8) contains supplementary material, which is available to authorized users.

Head and neck squamous cell carcinoma (HNSCC) is an aggressive disease marked by frequent recurrence and metastasis and stagnant survival rates. To enhance molecular knowledge of HNSCC and define a non-coding RNA (ncRNA) landscape of the disease, we profiled the transcriptome-wide dysregulation of long non-coding RNA (lncRNA), microRNA (miRNA), and PIWI-interacting RNA (piRNA) using RNA-sequencing data from 422 HNSCC patients in The Cancer Genome Atlas (TCGA). 307 non-coding transcripts differentially expressed in HNSCC were significantly correlated with patient survival, and associated with mutations in TP53, CDKN2A, CASP8, PRDM9, and FBXW7 and copy number variations in chromosomes 3, 5, 7, and 18. We also observed widespread ncRNA correlation to concurrent TP53 and chromosome 3p loss, a compelling predictor of poor prognosis in HNSCCs. Three selected ncRNAs were additionally associated with tumor stage, HPV status, and other clinical characteristics, and modulation of their expression in vitro reveals differential regulation of genes involved in epithelial-mesenchymal transition and apoptotic response. This comprehensive characterization of the HNSCC non-coding transcriptome introduces new layers of understanding for the disease, and nominates a novel panel of transcripts with potential utility as prognostic markers or therapeutic targets.

Alcohol consumption, tobacco use, and human papillomavirus infection have been well-established as the primary risk factors for head and neck squamous cell carcinoma (HNSCC). However, the surge in popularity of e-cigarettes (e-cigs) has prompted speculation of e-cig use potentially emerging as a new risk factor. With previous research on the safety of e-cigs still collectively inconclusive, a comprehensive study of the carcinogenicity of these devices remains urgently necessary. We therefore investigated the potential genotoxic, cytotoxic, and invasive and migratory effects of e-cig vapor exposure on human epithelial cells. A panel of normal epithelial and head and neck cancer cell lines was treated with 0.5%, 1.0%, and 2.0% by volume e-cig vapor from two popular e-cig brands, over periods ranging from 24 hours to 4 weeks. Neutral comet assay and immunostaining for γ-H2AX foci revealed significant induction of DNA double-stranded breaks (up to 3-fold increase, p < 0.05) in cell lines incubated with both nicotinized and nicotine-free e-cig vapor. To evaluate the cytotoxicity of e-cigarettes, trypan blue exclusion and clonogenic assays were performed following short-term e-vapor exposure. Our results indicate that in epithelial cells, short-term treatment induces up to a 5-fold increase in cell death without nicotine, and up to a 10-fold increase with nicotine as compared to untreated controls (p < 0.001). We subsequently assessed the effects of e-cigarettes on HNSCC progression and metastatic potential through exposure of established HNSCC cell lines to e-cigarette vapor. Wound healing assays revealed increased migration of HNSCC cells following e-cigarette treatment, with significant upregulation of key EMT-promoting genes observed via qRT-PCR. We will next examine the effects of long-term (6-9 months) e-cig vapor exposure in vivo using mouse models. Mouse oral epithelium will be harvested for histologic analysis and sequenced to determine the mutagenic potential of long-term e-cig vapor exposure. Nevertheless, our present findings based on short-term e-vapor exposure alone already pose alarming implications for the carcinogenic effects of e-cigarette use. Citation Format: Avinaash Korrapati, Vicky Yu, Maarouf A. Saad, Mehran Rahimy, Yinan Xuan, Angela Zou, Aswini Krishnan, Kevin Brumund, Weg M. Ongkeko. The carcinogenic effects of electronic cigarettes in oral cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4069.

Aberrant expression of microRNAs and piwi-interacting RNAs, two distinct classes of non-coding RNA (ncRNA) and important regulators of gene expression, is known to be implicated in human diseases including cancer. The exact roles of microRNAs and piwi-interacting RNAs in the pathogenesis of head and neck squamous cell carcinoma (HNSCC), however, remain poorly understood. Utilizing next generation RNA sequencing analysis of raw data obtained from The Cancer Genome Atlas, we discovered significant dysregulation (fold change ≥ 2) in 231 microRNAs and 60 piwi-interacting RNAs between forty-three matched samples of tumor and adjacent normal tissues, including down-regulation of mirs 30e and let7-c, and up-regulation of piR34736 and mir-196a-1 in tumor tissue compared to adjacent, non-tumor tissue. Further statistical survival modeling using patient survival data and cox proportional hazard regression analysis revealed that miRs 30e, 196a-1, and let7-c, and piR34736 correlated significantly with survival in patients with HNSCC. To further investigate these microRNAs and piwi-interacting RNAs, quantitative reverse transcriptase PCR (qRT-PCR) and MTT cell proliferation assays were performed in-vitro to assess their isolated effects on cancer gene expression in established HNSCC cell lines. Endogenous expression of these ncRNA was compared between a set of three normal oral keratinocytes and five HNSCC cell lines using qRT-PCR which confirmed miR-30e and mir-let7-c down-regulation and piR34736 and mir-196a-1 up-regulation in cancer. MTT cell proliferation assays upon knock-down of miR-196a-1 and ectopically expressed mir-let7-c in HNSCC revealed significant decreases in cell proliferation compared to cells transfected with their respective negative control. Identification of key ncRNAs differentially expressed between cancer tissue and adjacent normal tissue may reveal important steps in the initiation and progression of HNSCC as they are strongly correlated with patient survival. These key microRNAs and piwi-interacting RNAs may serve as potential biomarkers and therapeutic targets for future epigenetic-based cancer therapies. Citation Format: Jonjei Ku, Angela E. Zou, Thomas K. Honda, Hao Zheng, Maarouf A. Saad, Vicky Yu, Yinan Xuan, Pranav Singh, Mehran Rahimy, Selena Z. Kuo, Weg M. Ongkeko, Jessica Wang-Rodriguez. Identification of key survival-correlating microRNAs and Piwi-interacting RNAs dysregulated in head and neck squamous cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3836. doi:10.1158/1538-7445.AM2015-3836