Characteristics of rat carcinoma in culture

Rat chloroma cells have been propagated in permanent suspension cultures and are grown in Dulbecco's modified Eagle's medium with 10% fetal calf serum and 2.5% horse serum. Several lines have been established; the one of longest duration, Mia C51, has been maintained for over 18 months and has undergone over 100 transfers. Mia C51 cells have a doubling time of 12 hr and maintain many of the properties of the parent tumor, including the characteristic greenish color with high myeloperoxidase activity, an an aneuploid chromosomal pattern, and intact tumorigenicity. They will uniformly produce greenish chloroma tumors when injected into newborn rats. Electron microscopic examination of chloroma tumors and the cultured cells derived from them reveal the presence of extracellular mature and immature type C virus particles morphologically typical of oncornaviruses. Chloroma cells obtained from tumors that lost their alkaline phosphatase activity after repeated transfer regain full activity in culture. Studies using the antigen-antibody crossed electrophoresis indicate that the loss of alkaline phosphatase activity represents a true decrease in alkaline phosphatase protein, which is restored under culture conditions. The availability of a permanent chloroma cell line in culture that maintains the biological properties of the parent tumor provides a useful model for the study of myeloid leukemia.