EFFECT OF AMITRIPTYLIN ON THE GROWTH-KINETICS OF 2 HUMAN CANCER XENOGRAFT LINES IN NUDE-MICE

With respect to the controversial discussion of the effect of antidepr essants on the development of cancer in the literature, elicited by a recent report on growth stimulating effects of antidepressants (Brande s et al, Cancer Res 52: 3796, 1992), the effect of daily doses of amit riptylin (80 mg/m2 body surface, intraperitoneally) on the macroscopic growth of two human tumor xenograft lines in nude mice was studied (a malignant. melanoma, FO-1 and a renal cell adenocarcinoma, RCC). The application of the Gompertzian difference equation to compare the grow th patterns of treated and untreated tumors shows that amitriptylin do es modify the growth characteristics of both lines (p<0.05). however, in opposite directions: The growth of the melanoma FO-1 is stimulated whereas that of the RCC is inhibited. The growth pattern analysis furt her indicates, that this difference mainly consists of the differentia l effect of amitriptylin on the growth retarding processes of the tumo rs: amitriptylin inhibits the initial intrinsic growth rate of both tu mor lines, however, only in the case of the FO-1 does it inhibit simul taneously also the growth retarding process and, thus, it ultimately s timulates its growth. On the contrary the near exponential growth of t he RCC is not affected by amitriptylin. However, it cannot be excluded that at least some of the tumor growth modifying effects of the prese nt treatment may be attributed to the potentiation of the animal weigh t loss by amitriptylin in the tumor-bearing animals (p<0.05).