Combinatorial treatment with carboxyamidotriazole- orotate and temozolomide in sc-implanted human LOX IMVI melanoma xenografts

Abstract

Background: Carboxyamidotriazole orotate (CTO) is the orotic acid salt of 5-amino-1(4-(4-chlorobenzoyl)-3, 5-dichlorobenzyl)-1, 2, 3-triazole-4-carboxamide (CAI). CTO possesses increased solubility as compared to CAI as the free base. The antiproliferative and antimetastatic effects of CTO are related to inhibition of receptor-operated, calcium-channel-mediated calcium influx. CTO can inhibit calcium-sensitive signal transduction in the VEGF and the PI3K pathways, inhibition of FGF-2-induced tyrosine kinase, VEGF-mediated activation of phospholipase Cy, generation of IP3 and nitric oxide synthase activation, and induction of apoptosis in imatinib mesylate resistant CML cells by downregulating bcr-abl. Methods: Different combinations of CTO and temozolomide were first tested in female athymic NCr- nu/nu mice to evaluate tolerance of the combination. The tolerated combinations were then tested to evaluate the antitumor activity against subcutaneously implanted human LOX IMVI melanoma xenografts. Results: Oral CTO at doses of 513 or 342 mg/kg/dose Q1D × 14 resulted in inhibition of tumor growth ( p <0.001 and p =0.004). Oral TEM at doses of 90 and 60 mg/kg/dose Q4D × 3 resulted in dose-dependent inhibition of tumor growth ( p <0.001 and p <0.001). Oral CTO at 513 or 342 mg/kg/dose in combination with temozolomide 90 mg/kg/dose resulted in comparable tumor inhibition to temozolomide alone. However, oral CTO at 513 mg/kg/dose in combination with temozolomide 60mg/kg/dose resulted in additive antitumor activity compared to each drug alone. Also, CTO at 342 mg/kg/dose in combination with temozolomide 60mg/kg/dose had more than additive antitumor activity and was statistically different from the group treated with temozolomide 60 mg/kg/dose alone ( p =0.001). Conclusions: These results suggest that this combination of previously configured therapeutic doses of temozolomide with CTO enhances the sensitivity of temozolomide and may permit use of lower temozolomide doses to obtain an optimum antitumor effect in combination therapy. This dose-dilution combinatorial strategy fulfills the need for increased tumor sensitivity and efficacy. Additionally, this strategy reduces drug resistance and toxicity associated with dose dense strategy of temozolomide treatment in this melanoma model.