Sequential cytomorphological and cytochemical changes during development of bronchial carcinoma in beagle dogs exposed to 20-methylcholanthrene.

Abstract

The sequence of cytomorphological and cytochemical changes during 20-methylcholanthrene(20-MC)-induced malignant transformation of the bronchial epithelium was studied in 6 beagle dogs. Submucosal injection of 20-MC in the bronchus results in the occurrence of metaplastic cells without atypia, metaplastic cells with mild, moderate and severe atypia, and finally in cancer cells. In 2 control dogs treated with submucosal water injections squamous metaplastic cells without atypia, with mild, and occasionally with moderate atypia could be demonstrated. In individual morphologically classified cells quantitative cytochemical determinations of DNA and nuclear proteins were performed. In both groups of dogs squamous metaplastic cells without atypia, or with mild atypia, showed cytochemical changes similar to those found in growth-activated normal cells. Cells from 20-MC treated dogs morphologically classified as squamous metaplastic cells with severe atypia or cancer cells all showed highly increased and scattered amounts of nuclear proteins and DNA significantly deviating from those in normal proliferating cells.