Sequence-dependent inhibition of human colon cancer cell growth and of prosurvival pathways by oxaliplatin in combination with ZD6474 (Zactima), an inhibitor of VEGFR and EGFR tyrosine kinases

Abstract

To date, clinical studies combining the new generation of targeted therapies and chemotherapy have had mixed results. Preclinical studies can be used to identify potential antagonism/synergy between certain agents, with the potential to predict the most efficacious combinations for further investigation in the clinical setting. In this study, we investigated the sequence-dependent interactions of ZD6474 with oxaliplatin in two human colon cell lines in vitro. We evaluated the in vitro antitumor activity of ZD6474, an inhibitor of vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR) and RET tyrosine kinase activity, and oxaliplatin using three combination schedules: ZD6474 before oxaliplatin, oxaliplatin before ZD6474, and concurrent exposure. Cell proliferation studies showed that treatment with oxaliplatin followed by ZD6474 was highly synergistic, whereas the reverse sequence was clearly antagonistic as was concurrent exposure. Oxaliplatin induced a G 2 -M arrest, which was antagonized if the cells were previously or concurrently treated with ZD6474. ZD6474 enhanced oxaliplatin-induced apoptosis but only when added after oxaliplatin. The sequence-dependent antitumor effects appeared, in part, to be based on modulation of compensatory prosurvival pathways. Thus, expression of total and active phosphorylated EGFR, as well as AKT and extracellular signal-regulated kinase, was markedly increased by oxaliplatin. This increase was blocked by subsequent treatment with ZD6474. Furthermore, the synergistic sequence resulted in reduced expression of insulin-like growth factor-I receptor and a marked reduction in secretion of vascular endothelial growth factor protein. ZD6474 in combination with oxaliplatin has synergistic antiproliferative properties in human colorectal cancer cell lines in vitro when oxaliplatin is administered before ZD6474.

ZD6474 reverses multidrug resistance by directly inhibiting the function of P-glycoprotein

“…However, ZD6474 does not modulate chemosensitivity in parental chemosensitive cells. These results seem inconsistent with previous reports (Morelli et al, 2005;Troiani et al, 2006) and the mechanisms underlying this difference are currently unclear. However, it is noted in these previous reports that the ZD6474 treatment schedule is the key aspect for its combination effect with cytotoxic agents.…”

“…For example, an antagonistic effect was observed when cells were pretreated with ZD6474 followed by cytotoxic agents. On the contrary, a synergistic effect was evident when cells were pretreated with cytotoxic agents prior to EGFR antagonists (Morelli et al, 2005;Troiani et al, 2006). In this study, we treated MCF-7 cells with ZD6474 and cytotoxic agents simultaneously.…”

“…It has been reported that the effects of ZD6474 are synergistic with those of oxaliplatin and docetaxel in cells which do not overexpress P-gp, such as KYSE30 esophageal squamous epithelial cancer cells and HCT-116 and HT29 colon cancer cells (Morelli Troiani et al, 2006). A dose-dependent supra-additive effect in cell growth inhibition, in vitro, and tumour growth inhibition, in vivo, was also observed when ZD6474 was used in combination with paclitaxel or docetaxel (Ciardiello et al, 2003).…”

Investigation of Two Dosing Schedules of Vandetanib (ZD6474), an Inhibitor of Vascular Endothelial Growth Factor Receptor and Epidermal Growth Factor Receptor Signaling, in Combination with Irinotecan in a Human Colon Cancer Xenograft Model

“…In fact, we and other groups have shown that the combination of cytotoxic drugs and anti-EGFR or VEGFR-2 agents caused different antiproliferative effects in vitro depending on the treatment schedule (25,26). In this context, our group has shown that vandetanib possesses antiproliferative antitumor activity in vitro, which acts in a sequence-dependent manner with chemotherapeutic agents, such as oxaliplatin and irinotecan, in two human colon cancer cell lines (27). 5 In that study, treatment with chemotherapeutic agents followed by vandetanib resulted in enhanced antitumor activity in vitro.…”

Synergistic inhibition of human colon cancer cell growth by the cannabinoid CB1 receptor antagonist rimonabant and oxaliplatin

“…It has been very reported that oxaliplatin has synergistic effects in combination with ZD6474 (Zactima), an inhibitor of vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR) and RET tyrosine kinase activity. In fact, ZD6474 in combination with oxaliplatin is synergistic when oxaliplatin is administered before ZD6474 in colorectal cancer cells in vitro (19). Furthermore, combined exposure to ZD1839 (Iressa), a novel EGFR tyrosine kinase inhibitor and oxaliplatin also exerted synergy in colorectal cancer cell lines (20).…”