ASCITES SARCOMA-180, A TUMOR-ASSOCIATED WITH HYPERCALCEMIA, SECRETES POTENT BONE-RESORBING FACTORS INCLUDING TRANSFORMING GROWTH-FACTOR-ALPHA, INTERLEUKIN-1-ALPHA AND INTERLEUKIN-6

Ascites sarcoma 180 (S180A) is a transplantable tumor which causes hyp ercalcemia in tumor-bearing mice, and stimulates bone resorption witho ut parathyroid hormone-like activity. In the present study, parathyroi d hormone-related protein (PTHrP) mRNA could not be detected in total RNA from S180A cells. Bone-resorbing activity (BRA) derived from serum -free conditioned medium of S180A cells (S180A-CM) was coeluted with e ither transforming growth factor alpha (TGF alpha) activity (peak A, a pproximate M(r), 29 kDa) or lymphocyte-activating factor (LAF) activit y (peak B, M(r), 20.1-24 kDa) in Bio-Gel P-100 column chromatography. Fractions in peak A and B contained IL-6 but not tumor necrosis factor alpha (TNF alpha). Subsequent separation of peak A by reverse-phase h igh performance liquid chromatography produced a single fraction which contained both BRA and TGF alpha activity. Recombinant human TGF alph a-induced bone resorption was completely inhibited by indomethacin. Th e BRA in peak A was partially inhibited by indomethacin and almost com pletely inhibited by simultaneous treatment of indomethacin and anti-I L-6 antibody. The BRA in peak B was partially inhibited by neutralizat ion with anti-IL-1 alpha antibody and was completely inhibited by simu ltaneous treatment with anti-IL-1 alpha and anti-IL-6 antibody in the absence of indomethacin. Bone resorption induced by S180A-CM was assoc iated with an increased production of prostaglandin E(2) (PGE(2)) by c alvaria. The BRA in S180A-CM, however, was not completely abolished by the simultaneous addition of indomethacin and anti-IL-1 alpha, anti-I L-1 beta and anti-IL-6 antibodies. Our findings indicate that (1) BRA derived from S180A cells includes TGF alpha, IL-1 alpha, IL-6 and some other unknown factor(s), distinct from PTHrP, IL-1 beta and TNF alpha , and (2) these unknown factors resorb bone in part via a PGE(2)-indep endent pathway.