suramin interference with transforming growth factorbeta inhibition of human renal cell carcinoma in culture suramin is a polyanionic compound used clinically for the treatment of trypanosomiasis which is known to inhibit the action of many protein factors in vitro transforming growth factorbeta tgfbeta is a multifunctional regulatory protein which inhibits the growth of renal cell carcinoma in culture while suramin at 50500 microgramsml had no significant effect on the growth of renal cell carcinoma in culture in our experiments it did partially reverse the growth inhibition induced by tgfbeta in the two cell lines tested this effect apparently is caused by suramins direct interference with 125ilabeled tgfbetas ability to bind to the cell and not by any effect of suramin on the tgfbeta receptor furthermore suramin dissociates tgfbeta bound to the cell with a t12 of less than 30 min these results are consistent with those previously reported regarding suramins interaction with other protein growth factors and suggest that suramin may interact with the tgfbeta protein itself to inactivate it