Abstract 3618: Synergistic anti-tumor efficacy of a multi kinase inhibitor, Sorafenib combined with Paclitaxel in vitro and in vivo lung cancer models

Sorafenib (BAY 43-9006), a multi-kinase inhibitor, targets a serine-threonine kinase, BRAF as well as several tyrosine kinases. Paclitaxel has been known to exhibit potent anti-tumor activity in non-small cell lung cancer (NSCLC). Our aim of this study was to examine anti-proliferation, anti-angiogenesis and apoptosis induction when Sorafenib combined with Paclitaxel in vitro and in vivo NSCLC models. We measured the inhibitory activities of Sorafenib or Paclitaxel single and their sequential combinations(PS: Paclitaxel 24h → Sorafenib 48h and SP: Sorafenib 48h → Paclitaxel 24h) on cell proliferation in A549 (KRAS mutation), H1666 (BRAF mutation), and Calu-3 (p53 mutation) by SRB assay. We evaluated phosphorylation of ERK, AKT and BRAF proteins using Western bloting and analyzed the cell cycle distribution in A549 cell line. Xenograft tumor model was established with A549 tumor cells implanted in the Balb/c nu/nu mice. Together with single treatments, two different combination schedules of Sorafenib with Paclitaxel were examined. PPS, 20mg/kg of paclitaxel IP at 2 times in 1st wk followed by 40mg/kg of Sorafenib PO during 5 consecutive days in 2nd wk, PSS, 20mg/kg of Paclitaxel IP one time at 1st day followed by 40mg/kg of Sorafenib PO during 5 consecutive days in 1st week. Intratumoral molecular changes were studied on paraffin-embedded tumor tissue obtained from xenograft mice using immunohistochemistry and the apoptotic induction was evaluated with TUNEL assay. Single Sorafenib or Paclitaxel showed active cytotoxicities with dose-dependent manner in three cell lines. Their IC50s at 72hrs were as follows: A549, 5.7 ± 1.3 µM and 1.6 ± 0.1 nM; H1666, 3.7 ± 0.2 µM and 2.2 ± 0.6 nM; Calu-3, 8.8 ± 1.0 µM and 1.4 ± 1.3 nM, respectively, and the combination effect of PS was superior to SP in the three cell lines. A549 cells were treated with Paclitaxel (24h/48h), Sorafenib (24h/48h), PS and SP. Sorafenib significantly reduced the expressions of pBRAF, pERK and pAKT. PS showed greater reduction of pBRAF, pERK and pAKT compared to Sorafenib. However, downregulation of pERK expression was not detected in SP. Sorafenib induced G0/G1 arrest of cell cycle (54.5% at baseline vs. 61.9% at 48hr). PS demonstrated greater increase of G0/G1 arrest than SP (66.8% vs. 50.8%). In xenograft tumor model, Sorafenib combined with Paclitaxel (PPS or PSS) more effectively suppressed tumor growth compared to their single treatments. In immunohistochemistry study, greater inhibition of Ki-67 as well as pAKT, pERK, and CD31 were observed in two sequential combinations compared to single treatment. Additionally, significant increase of apoptotic change was also found in these two combinations. Taken together, sequential combination of Sorafenib with Paclitaxel demonstrated synergistic interaction and potent anti-tumor efficacy compared to their single treatment in vitro and in vivo NSCLC models. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3618.