5 to 1. 8 fold as compared to untreated cells in all three colon cancer cell lines tested. To study the mechanistic aspects of apoptosis induction by the combination of oxaliplatin and dovitinib, we next assessed the activation of caspases by Western blot ana lysis. Although treatment with oxaliplatin or Imatinib order dovitinib alone increased the levels of cleaved caspase 9 and ?3 in all three cell lines tested, the increase was more amplified with the combination of the two drugs indicating the involvement of these caspases in apoptosis induction. An important factor in inducing apoptosis is the enzyme Poly polymerase that de tects DNA strand breaks and functions in base excision repair. Once PARP is cleaved, it no longer supports the enzymatic DNA repair function.
It is a known marker of apoptosis and a downstream target of activated caspase 3. The expression of cleaved PARP was greatly en hanced after the treatment of HCT 116, HT 29 and SW 480 cells with combination of oxaliplatin and dovitinib, which might have contributed to the commitment to apoptosis . The quantitation intensity of PARP with respect to B actin is shown in Figure 3C. Combination of Dovitinib and Oxaliplatin inhibits tumor growth in Human Colorectal Cancer HT 29 Xenograft Based on our results showing strong efficacy of the com bination of oxaliplatin and dovitinib in colorectal cancer cells in culture, next we examined the in vivo efficacy of the combination against the colorectal cancer HT 29 xeno graft in athymic nude mice. Figure 1A shows tumor growth curve after treatment with oxaliplatin and/or Dovitinib.
Treatment with 3 weekly doses of oxaliplatin at 6. 7 mg/Kg was inactive as mono therapy in all animals. This is in agreement with a study showing inactivity of oxaliplatin as monotherapy in HT 29 animal model at MTD of 10 mg/Kg. Similarly an al ternate day dose of 60 mg/Kg Dovitinib showed a decrease of tumor growth as early as day 4 after treatment in all an imals. The combination of two drugs showed a significant decrease in tumor growth stating from an early stage as compared to vehicle or oxaliplatin treatment while at late stage compared to dovitinib alone. Similar re sults were also observed by Lee et al. in KM12L4a and HCT 116 colon cancer tumor models at dose level of 30 100 mg/Kg. The average final tumor volume was re duced from 2,036 327. 5 mm3 in control group to 1,957 204.
0 and 1,415 205. 9 mm3 in oxaliplatin and dovitinib treatment groups respectively, accounting for only 4% de Cilengitide crease in oxaliplatin group and 31% decrease in dovitinib treatment group at the end of the experimental regardless period. However, the combination treatment group showed a tumor volume of 906 94. 8 mm3, an ap proximate 55% decrease in tumor volume from vehicle or oxaliplatin group and 36% decrease from dovitinib treat ment group.