The Effects of Strontium on the Viability of Oral Carcinoma Cell Lines in the Presence of Simulated Smoking Environment

Abstract

Background: Oral squamous cell carcinoma (OSCC) is the sixteenth most common cancer worldwide and the most common malignancy that occurs in the oral cavity. Studies revealed a strong association between OSCC and smoking. However, the specific mechanistic effects of smoking on oral epithelium and its association with OSCC is still under investigation. A previous study suggested a positive influence of strontium citrate solution on human oral gingival fibroblasts viability and migration in the conditions of simulated smoking environment.

Aim: This in vitro study aimed to evaluate the effects of nicotine or cigarette smoke condensate (CSC) on the viability of a model gingival keratinocyte cell line (TIGK) as compared to oral carcinoma cell lines (SCC-25 or KB cell lines). In addition, to investigate the ability of strontium to mediate the impact of nicotine or CSC on those epithelial cell lines.

Materials & Methods: Using MTT assay, the viability of SCC-25, KB and TIGK cell lines was tested after the exposure to different concentrations of nicotine or CSC (5 – 500 μg/ml). Then, cellular viability was assessed after the addition of 1 mM of strontium citrate solution combined with 250 or 50 μg/ml of nicotine or CSC to evaluate the ability of strontium to reverse the effects of those materials.

Results: There was a dose-dependent reduction in SCC-25 viability with significant reduction seen with 500 μg/ml of nicotine or CSC. No significant effect of nicotine was noticed on KB cellular viability. Regarding TIGK cells, 50 μg/ml of nicotine and higher increased cellular activity while 250 μg/ml of CSC caused significant decrease in their activity. In general, the effect of CSC was stronger than nicotine. The addition of 1 mM of strontium citrate solution caused decreased viability of all three cell lines tested. This reduction in viability is consistent when cells were exposed to strontium alone or in the presence of nicotine or CSC.

Conclusion: Overall, CSC has a negative effect on the viability of both normal gingival keratinocytes and OSCC cell lines. The effect of nicotine may be variable depending on the cell type. Moreover, this study suggests a negative effect of strontium on an immortalized normal gingival keratinocyte cell line and oral carcinoma cell lines. Further studies are needed to evaluate the effects of strontium on the whole periodontal tissue and additional oral cancer cell lines.