Vicky Yu

Electronic cigarettes induce DNA strand breaks and cell death independently of nicotine in cell lines

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 h 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.

Transcriptome sequencing uncovers novel long noncoding and small nucleolar RNAs dysregulated in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma persists as one of the most common and deadly malignancies, with early detection and effective treatment still posing formidable challenges. To expand our currently sparse knowledge of the noncoding alterations involved in the disease and identify potential biomarkers and therapeutic targets, we globally profiled the dysregulation of small nucleolar and long noncoding RNAs in head and neck tumors. Using next-generation RNA-sequencing data from 40 pairs of tumor and matched normal tissues, we found 2808 long noncoding RNA (lncRNA) transcripts significantly differentially expressed by a fold change magnitude ≥2. Meanwhile, RNA-sequencing analysis of 31 tumor-normal pairs yielded 33 significantly dysregulated small nucleolar RNAs (snoRNA). In particular, we identified two dramatically down-regulated lncRNAs and one down-regulated snoRNA whose expression levels correlated significantly with overall patient survival, suggesting their functional significance and clinical relevance in head and neck cancer pathogenesis. We confirmed the dysregulation of these noncoding RNAs in head and neck cancer cell lines derived from different anatomic sites, and determined that ectopic expression of the two lncRNAs inhibited key EMT and stem cell genes and reduced cellular proliferation and migration. As a whole, noncoding RNAs are pervasively dysregulated in head and squamous cell carcinoma. The precise molecular roles of the three transcripts identified warrants further characterization, but our data suggest that they are likely to play substantial roles in head and neck cancer pathogenesis and are significantly associated with patient survival.

Nicotine Promotes Acquisition of Stem Cell and Epithelial-to-Mesenchymal Properties in Head and Neck Squamous Cell Carcinoma

The ability of nicotine to enhance the malignancy of cancer cells is known; however, the possibility that nicotine could regulate a cancer stem cell phenotype remains to be well-established. In this study we sought to determine whether long-term exposure to nicotine could promote cancer stem cell-like properties in two head and neck squamous cell carcinoma cell lines, UMSCC-10B and HN-1. Nicotine treatment induced epithelial-to-mesenchymal transition (EMT) in both cell lines by repressing E-cadherin expression, and led to the induction of stem cell markers Oct-4, Nanog, CD44 and BMI-1, which was reversed upon ectopic re-expression of E-cadherin. Nicotine-treated cells formed spheres at a higher efficiency than non-treated cells, formed larger tumors when injected into mice, and formed tumors with 4-fold greater efficiency compared to control cells when injected at limiting doses. Consistent with previous literature, nicotine-treated cells demonstrated a greater capacity for survival and also a higher tendency to invade. Comparison of microRNA profiles between nicotine and control cells revealed the upregulation of miR-9, a repressor of E-cadherin, and the downregulation of miR-101, a repressor of EZH2. Taken together, these results suggest that nicotine may play a critical role in the development of tobacco-induced cancers by regulating cancer stem cell characteristics, and that these effects are likely mediated through EMT-promoting, microRNA-mediated pathways. Further characterization of such pathways remains a promising avenue for the understanding and treatment of tobacco-related cancers.

The non-coding landscape of head and neck squamous cell carcinoma

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.

Pseudopodium-enriched atypical kinase 1 mediates angiogenesis by modulating GATA2-dependent VEGFR2 transcription

PEAK1 is a newly described tyrosine kinase and scaffold protein that transmits integrin-mediated extracellular matrix (ECM) signals to facilitate cell movement and growth. While aberrant expression of PEAK1 has been linked to cancer progression, its normal physiological role in vertebrate biology is not known. Here we provide evidence that PEAK1 plays a central role in orchestrating new vessel formation in vertebrates. Deletion of the PEAK1 gene in zebrafish, mice, and human endothelial cells (ECs) induced severe defects in new blood vessel formation due to deficiencies in EC proliferation, survival, and migration. Gene transcriptional and proteomic analyses of PEAK1-deficient ECs revealed a significant loss of vascular endothelial growth factor receptor 2 (VEGFR2) mRNA and protein expression, as well as downstream signaling to its effectors, ERK, Akt, and Src kinase. PEAK1 regulates VEGFR2 expression by binding to and increasing the protein stability of the transcription factor GATA-binding protein 2 (GATA2), which controls VEGFR2 transcription. Importantly, PEAK1-GATA2-dependent VEGFR2 expression is mediated by EC adhesion to the ECM and is required for breast cancer-induced new vessel formation in mice. Also, elevated expression of PEAK1 and VEGFR2 mRNA are highly correlated in many human cancers including breast cancer. Together, our findings reveal a novel PEAK1-GATA2-VEGFR2 signaling axis that integrates cell adhesion and growth factor cues from the extracellular environment necessary for new vessel formation during vertebrate development and cancer.

Abstract 4069: The carcinogenic effects of electronic cigarettes in oral cancer

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 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.

Abstract 3767: Nicotine promotes acquisition of stem cell and epithelial-to-mesenchymal properties in head and neck squamous cell carcinoma.

The ability of nicotine to enhance the malignancy of cancer cells is known; however, the possibility that nicotine could regulate a cancer stem cell phenotype remains to be well-established. In this study we sought to determine whether long-term exposure to nicotine could promote cancer stem cell-like properties in two head and neck squamous cell carcinoma cell lines, UMSCC-10B and HN-1. Nicotine treatment induced epithelial-to-mesenchymal transition (EMT) in both cell lines by repressing E-cadherin expression, and led to the induction of stem cell markers Oct-4, Nanog, CD44 and BMI-1, which was reversed upon ectopic re-expression of E-cadherin. Nicotine-treated cells formed spheres at a higher efficiency than non-treated cells, formed larger tumors when injected into mice, and formed tumors with 4-fold greater efficiency compared to control cells when injected at limiting doses. Consistent with previous literature, nicotine-treated cells demonstrated a greater capacity for survival and also a higher tendency to invade. Comparison of microRNA profiles between nicotine and control cells revealed the upregulation of miR-9, a repressor of E-cadherin, and the downregulation of miR-101, a repressor of EZH2. Taken together, these results suggest that nicotine may play a critical role in the development of tobacco-induced cancers by regulating cancer stem cell characteristics, and that these effects are likely mediated through EMT-promoting, microRNA-mediated pathways. Further characterization of such pathways remains a promising avenue for the understanding and treatment of tobacco-related cancers. Citation Format: Michael A. Yu, Alan Kiang, Jessica Wang-Rodriguez, Elham Rahimy, Martin Haas, Vicky Yu, Lesley G. Ellies, Jian-Bing Fan, Kevin T. Brumund, Robert A. Weisman, Weg M. Ongkeko. Nicotine promotes acquisition of stem cell and epithelial-to-mesenchymal properties in head and neck squamous cell carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3767. doi:10.1158/1538-7445.AM2013-3767