Isolation from the spleen of myeloproliferative sarcoma virus-infected mice of a myelomonocytic tumor cell line secreting hematopoietic colony stimulating factors.

Clonogenic tumor cells were detected in the spleen of DBA/2 mice infected with the myeloproliferative sarcoma virus (MPSV). These cells could be isolated because of their ability to proliferate on the greater omentum of sublethally irradiated isogenic recipient mice. We have established a permanent suspension myelomonocytic cell line in vitro (TE8), from a tumor obtained after subcutaneous transplantation of the omental tumor masses. The TE8 cells are clonogenic in semi-solid medium containing agarose. The colonies thus obtained gave rise to myelomonocytic cell lines growing in suspension in liquid medium. One of those cloned cell lines, C1(1011) was studied in details. It is exclusively composed of initial donor cells, it is tumorigenic in vivo, clonogenic in vitro and produces MPSV. It also secretes a colony stimulating activity (CSA), and an activity termed mixed colony promoting activity (MPA), which enables pluripotent hematopoietic stem cells to proliferate and differentiate. It differentiates through the granulomacrophage cell line independently of exogenous factors other than those which may be present in the serum.