Confluent BALB/c 3T3 cells monolayer provides selective and efficient growth of neoplastic cells

In an attempt to further characterize non-irradiated contact-inhibited confluent monolayer of BALB/c 3T3 cells (= Contact-Sensitive Plates; CSP) as substrata for in vitro drug sensitivity testing, we compared the efficiency of colony formation with panels of cell lines on CSP with that on plastic dishes or in agar. Tumorigenicity in athymic nude mice was also examined. We found that: (1) HeLa cells, 2 esophageal cancer lines, rat 3Y1 fibroblasts transformed by either adenovirus type 12, mouse polyoma virus, Rous avian sarcoma virus, or plasmid DNA carrying v-Ha-ras oncogene all formed colonies on CSP and in agar and at the same time was tumorigenic. The efficiency of colony formation on CSP proved always to be higher than that in agar. (2) None of the 4 "normal" fibroplastic cell lines formed colonies on CSP or in agar and were tumorigenic. (3) Simian virus 40 and adenovirus E1A gene transformed rat 3Y1 fibroblasts formed colonies on CSP but not in agar, and were not tumorigenic. Therefore, CSP was found to provide selective and efficient growth of neoplastic cells when compared to other substrata and is also helpful in detecting incompletely transformed cells.