STRUCTURE-FUNCTION ANALYSIS OF SIGNAL AND GROWTH-INHIBITION BY CARBOXYAMIDO-TRIAZOLE, CAI

Evidence is accumulating that calcium homeostasis and calcium-regulate d events may be selectively important in generation and maintenance of the malignant phenotype. CAI, a carboxyamido-triazole with a halogena ted benzophenone tail, is a novel inhibitor of receptor-operated calci um influx and arachidonic acid release which inhibits malignant prolif eration, invasion, and metastasis. The focus of this investigation was structural analysis of CAI and to determine if the inhibition of calc ium influx and arachidonic acid release by CAI and its antiproliferati ve activity were mediated through the same chemical domains. Four fami lies of molecular modifications of the CAI parent were synthesized: (I ) modification or substitution of the triazole ring; (II) removal of t he substituted benzophenone tail; (III) dehalogenation or partial trun cation of the benzophenone moiety; and (IV) removal of the triazole an d altered substitutions of the benzophenone tail. Compounds were teste d for the inhibition of calcium influx and arachidonic acid release an d inhibition of proliferation and colony formation in soft agar using the malignant CHO line transfected with the m5 muscarinic receptor and the A2058 human melanoma cell line. Only CAI and Group I compounds in hibited stimulated calcium influx, arachidonic acid release, and proli feration. Linear regression analysis of the relationship of the 50% in hibitory concentration values for all compounds in inhibition of calci um influx and arachidonate release was statistically significant (r(2) = 0.993). Similarly, a linear relationship was demonstrated between i nhibition of calcium influx and inhibition of tumor cell proliferation (r(2) = 0.971). Groups II-IV had minimal or no signal or growth inhib itory activity. This investigation provides the first evidence for a c oordinate link between calcium influx, calcium-mediated arachidonic ac id release, and malignant proliferation and metastasis and constitutes the initial analysis of structurally important domains of the CAI mol ecule.