Inflammation and Invasion in Oral Squamous Cell Carcinoma Cells Exposed to Electronic Cigarette Vapor Extract

Abstract

Electronic cigarettes (eCig) represent a new avenue of tobacco exposure that involves heating oil-based liquids and the delivery of aerosolized flavors with or without nicotine, yet little is known about their overall health impact. The oral cavity is an anatomic gateway for exposure that can be compromised by activating myriad of signaling networks. Oral squamous cell carcinoma (OSSC) is a common malignancy affecting 30,000 people in the United States each year. Our objective was to determine the impact of eCig and nicotine on gingival OSSC invasion and their secretion of pro-inflammatory molecules. Gingiva-derived Ca9-22 cells and tongue-derived Cal27 cells were exposed to eCig vapor extract (EVE) generated from Red Hot or Green Apple (Apple) flavored eCig solution +/- nicotine for 6 hours. Isolation of protein lysates and collection conditioned media was done after treatment. Real-time cellular invasion was assessed using a RTCA DP instrument. Protein expression was determined using western blot. Compared to controls, we observed: elevated NF-kB, TNF-α, ERK, JNK, MMP-13 and cell invasion by Ca9-22 treated with Apple EVE; increased TNF-α and JNK by Ca9-22 treated with Red Hot EVE; and increased TNF-α and JNK by Cal27 cells treated with both Apple and Red Hot EVE. We conclude that eCig flavoring and nicotine orchestrated differential cell invasion and inflammatory effects. This study provides an important initial step in dissecting mechanisms of cancerous invasion and molecular avenues employed by OSCC.

Prevalence, Knowledge, and Attitudes among Health Professions Students toward the Use of Electronic Cigarettes

“…That was also found in a similar study among university students in Jordan, where most students think that e-cigarette smoking is safer than conventional cigarette smoking [ 11 ]. In fact, e-cigarettes vapor is considered very harmful and is linked to oral squamous cell carcinoma [ 33 ]. Moreover, the nicotine contained in e-cigarettes is not only addictive, but can also lead to mouth cancer [ 34 ].…”

The Toxicological Effects of e‐Cigarette Use in the Upper Airway: A Scoping Review

“…These included elevated levels of secreted soluble inflammatory mediators (IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70, IL-13, tumor necrosis factorα, interferon-γ, CCL-5, CXCL-10, MCP-1, matrix metalloproteinase [MMP]-2, MMP-9, MMP-13, MUC5AC, MUC5B), increased expression of genes or proteins involved in inflammatory signaling (ERK1/2, p38, COX-2, JNK, and NF-kB), and enrichment of gene sets or pathways associated with inflammatory processes. 16,18,25,28,30,35,40,[42][43][44][45][46]49,53,62 Genotoxicity was seen primarily in the oral cavity, but also in the oropharynx and larynx, and was detected by increased DNA fragmentation, adducts, double-or single-strand breaks, appearance of micronuclei or metanuclear abnormalities, or increased expression of genes or proteins involved with DNA damage or repair pathways. 14,19,[22][23][24][25]27,32,51 Histological changes associated with acute and subchronic e-cigarette aerosol exposure in animal models were seen in the oral cavity, submandibular gland, nasal cavity, larynx, and trachea; however, the majority of these changes were considered adaptive and resolved following a recovery period.…”

“…Additionally, flavoring compounds associated with common flavor names (eg, fruit) often vary across brands, which precludes accurate comparisons of their toxicological impact. Our review found 11 studies 14,17,18,22,28,32,34,39,52,60,64 that directly compared flavors against one another; however, only menthol and tobacco were included in more than 2 studies. Notably, tobacco flavoring appeared to be generally less harmful than the other flavors studied.…”

“…One study 22 compared the effects of 10 different flavored e-liquids versus unflavored e-liquid of the same brand on oral epithelial cells and showed that, in general, flavored e-liquids (±nicotine) were associated with increased oxidative stress, lipid peroxidation, cytotoxicity, and micronuclei formation compared to unflavored e-liquid. Eleven studies 14,17,18,22,28,32,34,39,52,60,64 directly compared various e-cigarette flavors to one another; however, the flavors varied between studies limiting the generalizability of results.…”

“…In clinical studies, the brand of e-cigarettes used by subjects was generally not provided, and no information was included regarding whether devices contained added flavorings and/or nicotine. Thirteen human in vitro studies 14,[16][17][18]22,25,28,38,40,42,51,53,55 analyzed the effects of e-cigarette aerosol/condensate exposure with and without nicotine and showed mixed toxicological effects: 8 studies 14,16,17,22,25,51,53,55 demonstrated similar effects with and without nicotine; whereas 5 studies 18,28,38,40,42 showed aerosol/condensate exposure from nicotinecontaining e-cigarettes had enhanced toxicity. In these 5 studies, the addition of nicotine to e-cigarettes enhanced cytotoxicity, increased secretion of inflammatory mediators, increased intracellular oxidative stress, increased bacterial infectivity and enhanced cellular invasion and RAGE expression.…”