Chronic exposure to chewing tobacco selects for overexpression of stearoyl-CoA desaturase in normal oral keratinocytes

Abstract

Chewing tobacco is a common practice in certain socio-economic sections of southern Asia, particularly in the Indian subcontinent and has been well associated with head and neck squamous cell carcinoma. The molecular mechanisms of chewing tobacco which leads to malignancy remains unclear. In large majority of studies, short-term exposure to tobacco has been evaluated. From a biological perspective, however, long-term (chronic) exposure to tobacco mimics the pathogenesis of oral cancer more closely. We developed a cell line model to investigate the chronic effects of chewing tobacco. Chronic exposure to tobacco resulted in higher cellular proliferation and invasive ability of the normal oral keratinocytes (OKF6/TERT1). We carried out quantitative proteomic analysis of OKF6/TERT1 cells chronically treated with chewing tobacco compared to the untreated cells. We identified a total of 3,636 proteins among which expression of 408 proteins were found to be significantly altered. Among the overexpressed proteins, stearoyl-CoA desaturase (SCD) was found to be 2.6-fold overexpressed in the tobacco treated cells. Silencing/inhibition of SCD using its specific siRNA or inhibitor led to a decrease in cellular proliferation, invasion and colony forming ability of not only the tobacco treated cells but also in a panel of head and neck cancer cell lines. These findings suggest that chronic exposure to chewing tobacco induced carcinogenesis in non-malignant oral epithelial cells and SCD plays an essential role in this process. The current study provides evidence that SCD can act as a potential therapeutic target in head and neck squamous cell carcinoma, especially in patients who are users of tobacco.

Multiomic analysis of oral keratinocytes chronically exposed to shisha

“…We have previously investigated cellular models using cigarette smoke and chewing tobacco to understand molecular alterations associated with different forms of tobacco. 12,13 In this study, we investigated mutational spectrum and dysregulation of gene expression pattern in immortalized normal human oral keratinocytes (OKF6/TERT1) chronically treated with shisha extract.…”

Cytogenetic Biomonitoring in Buccal Mucosa Cells from Young Smokers

“…Epidemiologic studies have proven that cigarette smoking is the major cause of oral cancer [1,2]. Therefore, tobacco has been considered the single most important man-made cause of cancer that can be avoided.…”

Molecular alterations associated with chronic exposure to cigarette smoke and chewing tobacco in normal oral keratinocytes

“…Adaptation of oral keratinocytes to smokeless tobacco extract and cigarette smoke condensate OKF6/TERT1 cells were chronically treated with 1% smokeless tobacco extract (STE) (preparation detailed in Supplementary Methods) for a period of 8 months as previously described. 40 Cell stocks of cells treated for two, four, six and eight months were periodically frozen and stored in liquid nitrogen for further experiments. STE treated cells were grown at 37 C in a humidified 5% CO 2 incubator.…”

“…[37][38][39] Our group has previously reported the proteome-wide alterations in oral keratinocytes upon chronic exposure to smokeless tobacco and identified stearoyl CoA desaturase as a potential therapeutic target in head and neck squamous cell carcinoma. 40 Metabolic differences have been reported between smokers and snuff users but the molecular/proteomic alterations between smokers and tobacco chewers are not well elucidated. 41 A recent study employed microarray analysis to elucidate gene expression differences in peripheral blood mononuclear cells (PBMCs) obtained from smokers and moist snuff users.…”