The compound
317615 x 2HCl, a selective
protein kinase Cbeta inhibitor, was not very cytotoxic toward human CaKi1
renal cell carcinoma cells or human HT-29 colon
carcinoma cells in monolayer culture. Isobologram analysis was used to determine additivity or synergy of the combination regimens. Exposure of CaKi1 cells to
317615 x 2HCl (10 or 100 mM) along with
gemcitabine or
5-fluorouracil for 24 hours resulted in cytotoxicity that appeared to be less-than-additive to additive for the two agents. Exposure of HT-29 cells to
gemcitabine along with
317615 x 2HCl (10 mM or 100 mM) resulted in a synergistic cytotoxicity while combinations with
5-fluorouracil resulted in additive to greater-than-additive cytotoxicity for the agents.
After treatment of CaKi1 or HT-29 xenograft-bearing mice with
317615 x 2HCl, immunohistochemical staining for expression of endothelial specific markers, either CD31 or CD105, was used to quantify the number of intratumoral vessels in the samples. CaKi1
tumor angiogenesis was very responsive to treatment with
317615 x 2HCl such that the number of intratumoral vessels stained by CD31 or CD105 was decreased to 20% of the control. The HT-29 colon
carcinoma angiogenesis was also responsive to
317615 x 2HCl, such that the number of intratumoral vessels stained by CD31 or CD105 was decreased to 40% to 50% of the controL
5-fluorouracil,
cisplatin or fractionated
radiation therapy was combined with treatment with
317615 x 2HCl in the simultaneous combination treatment regimen in animals bearing HT-29 colon
carcinoma xenografts. The resulting
tumor growth delays indicated that administration of
317615 x 2HCl increased the effects of the cytotoxic
therapy. Both a simultaneous or an overlapping treatment regimen and a sequential treatment regimen were used to assess
317615 x 2HCl alone and along with fractionated
radiation therapy or
gemcitabine against the human CaKi1
renal cell carcinoma xenograft. The CaKi1
tumor was quite sensitive to fractionated
radiation therapy and to
gemcitabine and, although
317615 x 2HCl was an effective single agent in this
tumor, the combination regimens did not reach additivity for the combination regimens in vivo.
317615 x 2HCl is in early clinical testing.