A Cell Culture System for the Assessment of Tumor-Promoting Activity

Summary

A tissue culture system was developed to aid in the identification of tumor-promoting agents from tobacco leaf extracts and to study their mechanisms of action. Growth of clones of either viral or chemically transformed cells was enhanced in a mixed culture system, containing a large excess of contact-inhibited cells, by tumor-promoting agents from tobacco leaf extracts, by phorbol esters from croton oil, and by other chemicals. Without toxicity, the enhancement of outgrowth of transformed clones was related directly to the dose of the tumor-promoting agent and the density of the contact-inhibited cell overlay.