Combinatorial treatment using CTO with paclitaxel or paclitaxel orotate in sc-implanted human OVCAR-5 ovarian tumor model.

Abstract

e15515 Background: Paclitaxel (PXL) was converted to paclitaxel orotate (PXLO). Different combinations of Carboxyamidotriazole orotate (CTO) and PXL or PXLO were first evaluated in female non-tumored athymic NCr-nu/nu mice to determine the tolerance of the combinations. 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, and inhibit FGF-2-induced tyrosine kinase. Methods: The antitumor effect of combinations was tested for: i) PXLO compared to PXL, ii) combinatorial effect of low (342mg/kg/dose) and high (513mg/kg/dose) doses of CTO (Q1Dx14, PO) with low (11.6 and 10mg/kg/inj, Q2Dx3/2 weeks, IV) and high (23.2 and 20mg/kg/inj, Q2Dx3/2 weeks, IV) respectively, doses of PXLO or PXL, against sc-implanted human OVCAR-5 ovarian tumor xenografts. Results: Results obtained in non-tumored mice show high PXLO plus CTO was better tolerated than high PXL plus CTO. In tumor bearing mice, oral CTO at doses of 513 or 342mg/kg/dose Q1Dx14 given alone resulted in slight inhibition of tumor growth, reaching statistical significance only when administered at a low dose (two tumor mass doubling: p=0.036 for 342mg/kg/dose). PXLO at 23.2 and 11.6mg/kg/inj. given alone inhibited tumor growth (p<0.001, 0.029, respectively). PXL at 20 and 10mg/kg/inj inhibited tumor growth (p<0.001 and 0.011, respectively). Since body weight loss was less with the orotate form of PXL, PXLO should be the preferred drug over PXL. Addition of oral CTO 513 or 342mg/kg/dose to PXLO 23.2 or PXL 20mg/kg/inj resulted in comparable tumor inhibition to PXLO or PXL alone. However, combination of PXLO 11.6 and PXL 10mg/kg/inj with CTO 513 or 342mg/kg/dose resulted in tumor inhibition suggesting that a low dose of PXL or PXLO may be combined with CTO to achieve tumor inhibition and to allow the use of the lower doses of PXL to reduce toxicity. Conclusions: Results suggest that PXLO is less toxic than PXL and CTO influences the sensitivity of PXL suggesting a role for combinatorial therapy with low doses of PXL and CTO in this ovarian tumor model.