The effect of the cell microenvironment on cell functions associated with tumor promotion and progression

To study the role of the cellular microenvironment in tumor promotion and progression, transformed cells of rat embryonic fibroblasts (CL-1 clone) were transplanted into transgenic immunodeficient mice and cells of the formed tumor were converted into culture (CL-1-1 cells). Cells before and after transplantation were compared in morphology, growth rate, and permeability of intercellular gap junction. CL-1-1 cells were shown to have a changed morphology, to grow faster than the CL-1 cell, and to have no contact inhibition. In the G₁ phase of the cell cycle, there were many more CL-1 than CL-1-1 cells, whereas, in the G₂ and M phases, CL-1-1 cells were predominant. The permeabilities of the gap junction in the CL-1 and CL-1-1 cells were approximately the same. It was concluded that the cell microenvironment can stimulate tumor promotion and tumor progression upon transplantation of transformed cells into immunodeficient animals.