Malignization In Vitro of Hamster Embryonic Cells by Chemical Carcinogens

Abstract

Hamster embryonic cells were cancerized successfully by treatment in vitro with 4-NQO, 4-HAQO, and 6-chloro 4-NQO. The characteristic changes appeared in the cells 2 or 3 days after the treatment with carcinogens such as necrosis and criss-crossed arrangement of fusiform cells. These early changes were later followed by morphological transformation, i.e., the appearance of transformed foci in which the cells grew actively, piled up and formed dense layer. Malignization of these cells was confirmed by transplantation into newborn and adult hamsters. The animals died of tumor, sometimes with metastasis. The time required for the malignization of normal cells was different, depending on the frequency of treatment and given amount of carcinogen. It was noteworthy that even one single treatment of 4-HAQO could induce the malignization of normal cells, although it took longer time. In the untreated cultures, no transformed cells were found. The control cells revealed a monolayer growth of fibroblastic cells, which was later followed by a non-proliferating state of large, flat and granulated cells. The control cells failed to produce tumor in animals.
The techniques of in vitro system on experimental carcinogenesis seem to be a useful and new approach to uncover various problems in carcinogenesis, especially the early stage of cancer development, i.e., cancerization of normal cells to malignant.