ALTERATIONS OF THE IN-VIVO GROWTH-PATTERN OF XENOTRANSPLANTED HUMAN-MALIGNANT MELANOMAS AFTER SURAMIN TREATMENT IN NUDE-MICE

The effect of suramin on the in vivo growth of 4 human malignant melan oma xenotransplantation lines in nude mice was studies. The drug (mult iple i.p. injections of 80 mg/kg) was well tolerated by the animals, h owever, no tumor regressions were seen. All 8 different sets of tumor growth data (4 treated and 4 control groups of 8 tumor-bearing animals each) fitted well to the Gompertz difference equation, which enables to precisely analyse the pattern of tumor growth. The results show tha t suramin treatment leads to a statistically significant inhibition of the intrinsic growth rate of all tumors and also a simultaneous parti al inhibition of the growth deceleration rate in three of the 4 tumor lines. As result of this complex alteration the growth of most melanom a lines presently studied is ultimately stimulated by suramin treatmen t in vivo. However, one recently established line is an exception: in this tumor suramin did not significantly affect growth retardation and thus, led to an overall growth inhibition. One possible interpretatio n might be, that suramin simultaneously inhibits both the positive and the negative growth regulatory mechanisms of the tumors to different degrees leading to a new balance between them, which is expressed in a different growth pattern.