Abstract: OBJECTIVE: To explore the influence of expression of human papilloma virus (HPV) on MNNG-induced malignant transformation of Het-1A normal esophageal epithelial cells,and to provide better understanding for pathogenesis of esophageal cancer. METHODS: Cells were divided into HPV (transferred with HPV lentivirus),control (transferred with empty vector),MNNG,and combined HPV and MNNG groups. HPV expression and empty carrier cells were exposed to MNNG (2 μmol/L) for 24 hours per generation. The morphology of these cells was observed at the same time. Functional tests were conducted in cells of the 10^th,20^th and 35^th generations. CCK-8 and cell cycle distribution detection assays were conducted to document changes of viability and proliferation activity. Proliferation indexes were used to monitor proliferation. Apoptosis was detected by Annexin V-APC/PI double staining. Invasion and migration ability of cells were detected by transwell assay. Soft agar colony forming experiments were performed. Nude mice tumorigenicity assay was conducted to detect malignantly transformation. RESULTS: Among the different cell groups,the MNNG and the combined HPV and MNNG groups had the most obvious change in morphology,with the formation of loose,slender and pseudopods. These observations were consistent with that from the CCK-8 and the cell cycle distribution assays. The proliferative activities for the MNNG and the combined HPV and MNNG groups were increased first,then inhibited and finally increased again (P < 0.05). Compared with the MNNG exposure group,the anti-apoptotic ability of the combined HPV and MNNG group was increased (P < 0.05). The results of invasion and migration tests showed that the number of transmembrane in cells of the combined HPV and MNNG group was significantly higher than that in the other groups (P < 0.05) which was followed by the MNNG exposure group. In the soft agar cloning experiment,the colony formation rate of the combined HPV and MNNG group was (30.8±0.2)% higher than that of the MNNG group (27.1±0.3)% (P < 0.05). Cells from the MNNG and the combined groups induced tumors in nude mice while the HPV and the control groups did not form any local mass. CONCLUSION: Combined exposure of HPV and MNNG caused malignant transformation of the Het-1A normal esophageal epithelial cells via significant enhancement of cell proliferation,anti-apoptosis,invasion,cell migration and non-anchorage independent growth. HPV expression could therefore participate in and promote the malignant transformation process.

Key words: HPV, MNNG, Het-1A cells, malignant transformation