Antiangiogenic and antitumor effects of a protein kinase Cβ inhibitor in murine Lewis lung carcinoma and human Calu-6 non-small-cell lung carcinoma xenografts

Abstract.

In cell culture, the compound 317615·2HCl, a potent inhibitor of VEGF-stimulated HUVEC proliferation, was not very effective against Calu-6 non-small-cell lung carcinoma cells (IC₅₀ 26 µM). Exposure to combinations of paclitaxel or carboplatin and 317615·2HCl with Calu-6 cells in culture resulted in cell survival that reflected less-than-additivity to additivity of the two agents. Administration of 317615·2HCl orally twice daily to nude mice bearing subcutaneous Calu-6 tumors resulted in a decreased number of intratumoral vessels as determined by CD31 and CD105 staining to 50% of the number in control tumors. 317615·2HCl showed antitumor activity against the Lewis lung carcinoma and increased the tumor growth delay produced by paclitaxel by 5-fold, that produced by gemcitabine by 2-fold and that produced by carboplatin by 1.7-fold. There was a decrease in the number of lung metastases in the Lewis lung carcinoma that paralleled the increased response of the primary tumor with each treatment combination. Administration of 317615·2HCl also increased the tumor growth delay produced by fractionated radiation therapy in the Lewis lung tumor. Treatment with 317615·2HCl was an effective therapy in the Calu-6 non-small-cell lung carcinoma xenograft when the compound was administered early (days 4–18) or later (days 14–30). Combination treatment regimens in which 317615·2HCl was administered along with or sequentially with paclitaxel or carboplatin were much more effective than the chemotherapeutic agents administered alone. 317615·2HCl is in early clinical testing.