Vasoformative sarcomas arising from BALB/3T3 cells attached to solid substrates.

The BALB/3T3 mouse embryo cell line, noted for its marked postconfluence inhibition of proliferation, anchorage dependence, and high serum requirement, and frequently studied as a prototype nontumorigenic "fibroblast" line that is compared with tumorigenic sublines transformed with various agents, produced tumors within 2 to 3 months when an average of 3 X 10(4) cells were implanted s.c. attached to 1- X 5- X 10-mm polycarbonate platelets. Plastic platelets alone produced no tumors after 1 year of observation. The tumors, as well as others arising from implants of BALB/3T3 cells attached to 3-mm glass beads, were given the histological diagnosis of "vasoformative saroma" because the tumor cells frequently formed vascular channels. The vasoformative pattern and the results of specific staining for reticulin and collagen support the likelihood that BALB/3T3 cells originated from endothelial cells rather than from fibroblasts. That the tumors were derived from BALB/3T3 cells and not host cells was proved when tumors arising in BALB/c X C57BL/6 F1 hybrids were shown to be transplantable to BALB/c but not to C57BL/6 mice. The cultured tumor cells showed loss of both postconfluence inhibition of proliferation and anchorage dependence. Evidence of the induction of endogenous oncornaviruses was obtained in only one of four tumors tested. These tumors also exhibited tumor-unique transplantation rejection antigens. We conclude that BALB/3T3 cells are preneoplastic and give rise to different spontaneously transformed clones bearing unique tumor rejection antigens when implanted in vivo attached to a solid substrate.