Abstract 4767: C6 ceramide sensitizes multiple aggressive pancreatic cancer cell lines to gemcitabine, paclitaxel and cetuximab mediated anti tumor effects in vivo and in vitro

Abstract

Abstract Introduction: Pancreatic adenocarcinoma continues to be a highly lethal malignancy (5 yr survival 5%) poorly responsive to all chemo radiation therapies, with only modest improvement with Gemcitabine the current “main line” drug. We have previously demonstrated the C6 Ceramide chemo enhancement of Gemcitabine and other pancreatic chemo agents. The current study explores the mechanism of C6 Ceramide effects on pancreatic chemo resistance pathways – pro-survival and ras-signaling in pancreatic cancer cells. Methods: In vivo: 2-3 month SCID male mice with pancreatic (pan) tumor implants (2 × 106 L3.6 cells) received intraperitoneal (I.P.) injections (3x/wk) of Paclitaxel (Pax) (3.0mg/gm), Gemcitabine (Gem, 10mg/gm) with/without C6 ceramide (10mg/ml) and were observed 6 weeks and tumor response/survival recorded. In vitro: Drug dose Pax 3 ug/ml, Gem 3 ug/ml, C6 Ceramide 10 ug/ml. The MTT anti tumor response was measured in 3 pancreatic lines L3.6, PANC-1, and MIA (Kras mutated). Signaling activation by Western blot utilized antibodies: LY294002, and Wortmannin to block PI3K/AKT pathway, U0126 and PD 98059 to block ERK pathway and Rapamycin to block mTORC1 pathway. Results: Combined therapy with C6 Ceramide induced significant inhibition of exponential tumor growth and prolonged survival by Gem and Pax. Administration of Gem or Pax with C6 Ceramide induced a significant increase in cell death and apoptosis in pancreatic cancer cells (L3.6, PANC-1 and MIA PaCa-2) which were associated with inhibiting perturbations of cell signaling pathways including pro-survival PI3K/Akt/mTOR, and ERK/MAPK, Ras signaling pathways. Pharmacological inhibition with specific signaling pathway inhibitors enhanced cytotoxicity by Gem or Pax, suggesting that survival pathway inhibition might be the key mechanism contributing to C6 Ceramide synergism of Pax or Gem anti-tumor effects. We also showed C6 ceramide potentiation of Cetuximab anti tumor effects on Kras mutant MIA cells thus overcoming (EGFR mAb) resistance by inhibiting pro-survival PI3K/AKT/mTOR pathways and bypassing K-RAS mutant Ras-ERK pathways. Conclusion: C6 Ceramide an apoptosis signal potentiates the anti tumor effects of chemo agents Gemcitabine and Paclitaxel and the biologic EGFR Inhibitor Cetuximab against 3 aggressive pancreatic cancer cell lines by apparent inhibition of the pro-survival PI3K/AKT/mTOR pathways and the Kras mutated ERK/MAPK pathway. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4767. doi:10.1158/1538-7445.AM2011-4767