Investigation of possible autocrine functions for rat GRO/CINC (cytokine-induced neutrophil chemoattractant)

Rat cytokine-induced neutrophil chemoattractant (CINC) is an eight kilodalton polypeptide originally purified from media conditioned by interleukin-1 beta stimulated 52E, an epithelioid clone derived from normal rat kidney (NRK) cells. Using a fibroblastic clone of the NRK cells, 49F, we found expression of the CINC gene to be induced by either serum or cytokines in growth-arrested cultures within 1 hour of stimulation. There was no observable CINC expression in exponentially growing cells in the absence of cytokine stimulation. CINC protein had no significant effect on 3H-thymidine incorporation or growth rate of NRK49F. We have observed that CINC is constitutively produced by some transformed NRK cells, clone RC20, suggesting an association with the expression of a transformed phenotype. Unlike the parent 49F, RC20 cells are capable of growth in soft agar and serum-free media and form highly metastatic tumors in nude mice. We have examined the possible autocrine functions of CINC and its possible links to the expression of the transformed phenotype by these cells. The use of a blocking CINC polyclonal antibody demonstrated that CINC did not function as an autocrine growth factor for RC20. Though CINC is a potent chemoattractant for neutrophils, it did not induce migration of either RC20 or 49F cells. CINC only moderately promoted adhesion of RC20 cells when used as a matrix protein. These data do not support the hypothesis that production of CINC by the RC20 cells provides an obvious advantage for the transformed cells constitutively producing it.