TAC1 and neoplasm: They also inhibit mitogenesis by the same neuropeptides in both Swiss 3T3 cells and SCLC cells (Woll and Rozengurt, 1988; Sethi et al, 1992; Seckl et al, 1995) In addition to the in vitro growth inhibitory effects of substance-P analogues, these compounds inhibit the growth of tumours in xenograft models in nude mice (Langdon et al, 1992) and are more effective than specific neuropeptide receptor antagonists.