Abstract 3287: Pro-inflammatory factors secreted by pancreatic cancers with evasive resistance to anti-VEGF treatment contribute to malignant progression by inducing EMT
Authors: Carbone Carmine , Moccia Tania , Zhu Cihui , Paradiso Genni , Simbolo Michele , Budillon Alfredo , Chiao Paul J. , Abbruzzese James L. , Melisi Davide 
Published: June 2012

Background: Resistance of tumors to anti-angiogenic therapies is becoming an increasingly relevant issue. Moreover, recent studies provided evidences that VEGF-targeted drugs could make tumor cells more aggressive and metastatic.

Methods: To identify the tumor-derived factors responsible for the evasive resistance of pancreatic cancer to anti-VEGF treatment we established and validated two models of human pancreatic cancer cell lines resistant in vivo to bevacizumab. We compared gene expression profiles from sensitive versus resistant cell lines using Ingenuity Pathways Analysis software.

Results: The cellular functions significantly associated to the anti-VEGF- resistance gene expression profiles concerned with the chemoattraction of leucocytes, especially granulocytes, and with the mobilization of myeloid progenitor cells. Beside the minor over-expression of well-recognized direct pro-angiogenic factors, we identified several pro-inflammatory factors overexpressed by the anti-VEGF resistant cells in comparison to their sensitive controls. In this regard, the anti-VEGF- resistant tumors demonstrated a significantly higher infiltration by CD11b+ pro-angiogenic myeloid cells in comparison to the anti-VEGF- sensitive tumors.

Anti-VEGF resistant cell lines demonstrated in vitro and in vivo a more aggressive phenotype. Expression of transcription factors Zeb1, Zeb2, and SMAD3, which are involved in Epithelial- to- Mesenchymal Transition (EMT), were significantly up-regulated in both anti-VEGF- resistant cell lines in comparison to the respective controls Consistently, anti-VEGF- resistant cell lines expressed significantly lower levels of E-Cadherin, and higher levels of Vimentin proteins in comparison to the respective anti-VEGF- sensitive cell lines when cultured in vitro. In vivo, anti-VEGF- sensitive tumors showed a strong expression of E-cadherin and a moderate expression of Vimentin. On the contrary, resistant tumors demonstrated no expression of E-cadherin, a strong expression of Vimentin, and a significant desmoplastic reaction. In co-colture assays, secreted factors over-expressed by the anti-VEGF- resistant cells induced EMT and a more aggressive phenotype in control sensitive cells.

Conclusion: anti-VEGF therapy induces a selection of pancreatic cancer cells over-expressing secreted mediators of vascular inflammation. These factors could act in a paracrine manner recruiting pro-angiogenic myeloid cells and thus inducing an indirect angiogenesis. In addition, they could act in an autocrine manner to induce EMT and in turn a more aggressive behavior of pancreatic cancer.

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 3287. doi:10.1158/1538-7445.AM2011-3287