Abstract 1582: Comparative transforming effects of ultra low tar (ULT) and full flavor low tar (FFLT) cigarette smoke particulate extracts on human oral epithelial cells

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA ULT cigarettes produce much lower levels of tars and particulate matter than FFLT cigarettes, but are generally not safer alternatives with respect to carcinogenesis, possibly because of compensatory smoking behavior. In a previous study (P.G. Sacks, et al., Food Chem Toxicol 49 (2011) 2348-2355) we reported that tobacco smoke particulate (TSP) extracts from FF, FFLT and ULT cigarettes exerted similar effects on the induction of phase I and II proteins and the activation of the tobacco carcinogen, benzo(a)pyrene (BaP) to genotoxic metabolites in primary oral epithelial cells when compared on a concentration basis, although ULT cigarettes were less effective on a per cigarette basis. Here we report that both a FFLT and an ULT TSP extract transform a human oral epithelial cell line to growth independence in soft agar, and enhance the transforming effects of BaP. At equal concentrations the ULT extract was more effective than the FFLT extract. A human oral leukoplakia cell line, MSKleuk1, was employed in these studies. Cells were treated twice over a two week period or 3 times over a 3 week period with: a) one uM BaP, b) 4ug/ml TSP extract, c) TSP extract + BaP, or d) vehicle control. One week after the last treatment cells were seeded on soft agar and were assayed either by counting colonies 3 weeks after seeding, or 8 days after seeding using an anchorage-independent growth assay (CytoSelect 96-Well Cell Transformation Assay Kit, Cell Biolabs). Results in initial experiments for the two week treatment were assayed by counting colonies, and the fraction of growth-independent cells for groups a-d resp. were: a, 5.5 +/- 0.2; b, 6.0 +/- 0.6; c, 6.6 +/- 0.3 and d, 0.78 +/- 0.3 (all in units of 10E-4). For the three week treatment the results were: a, 9.1 +/- 0.5; b, 9.2 +/- 1.2; c, 11.9, +/- 2.5; d, 1.4 +/- 0.7. The TSP extract was from a reference filtered cigarette, 2RF4. A further soft agar assay was carried out using the cell transformation assay; and TSP extracts from a commercial ULT and 2RF4 cigarettes were compared, in the presence and absence of BaP. The groups were a) 1 uM BaP, b) 4ug/ml 2RF4 extract, c) 4ug/ml 2RF4 extract + 1 uM BaP, d) 4ug/ml ULT extract, e) 4ug/ml ULT extract + 1uM BaP and f) vehicle control. All groups were treated 2x as described above. Results are expressed relative to the vehicle control which is set as 1. a, 1.9 +/- 0.4; b, 1.4 +/- 0.3; c, 2.2 +/- 0.4; d, 2.1 +/ 0.3; e, 2.6 +/- 0.6.The results of these show: 1) human oral epithelial cells can be transformed by BaP, and TSP extracts from FFLT and ULT cigarettes, 2) the effects of BaP and TSP extracts are approximately additive, 3) when compared on a concentration of particulate basis, ULT TSP extracts were more effective than FFLT TSP extracts. Unlike previous studies relating primarily to carcinogenesis initiation, ULT TSP extracts appear to more effective at transformation than FFLT TSP extracts. Citation Format: Tianzhen Han, Peter Sacks, Joseph B. Guttenplan. Comparative transforming effects of ultra low tar (ULT) and full flavor low tar (FFLT) cigarette smoke particulate extracts on human oral epithelial cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1582. doi:10.1158/1538-7445.AM2014-1582