AN EXPERIMENTAL-MODEL OF MULTISTEP LARYNGEAL CARCINOGENESIS - COMBINED EFFECT OF HUMAN PAPILLOMAVIRUS TYPE-16 GENOME AND N-METHYL-N'-NITRO-N-NITROSOGUANIDINE

This report describes the two-step in vitro transformation of human la ryngeal epithelial cells (HLEC cells). Primary cultured HLEC cells wer e first transfected with cloned full-length human papillomavirus type 16 DNA, and two immortalized cell lines (HLEC-16 cell lines) were sele cted by subculturing transfected cells that continued to proliferate. The HLEC-16 cell lines were not tumorigenic in nude mice, and did not proliferate well in a culture medium containing a physiological level of calcium (Dullbecco's minimum essential medium supplemented with 10% fetal bovine serum = DMEM + 10%FBS). The HLEC-16 cell lines were seco ndarily exposed to N-methyl-N'-nitro-N-nitrosoguanidine, and several p roliferating colonies were isolated in DMEM + 10%FBS. Among these calc ium/serum-resistant cell colonies, one colony exhibited enhanced proli feration capacity in nude mice. These results support the hypothesis t hat human laryngeal epithelial cells may be the target for neoplastic transformation by a combined effect of human papillomaviruses and chem ical carcinogens.