Abstract 3294: Augmentation of antiangiogenic therapies to enhance Gemcitabine response in pancreatic cancer
Authors: Awasthi Niranjan , Schwarz Margaret A. , Schwarz Roderich E. 
Published: June 2012

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related deaths in the United States. Gemcitabine (Gem) is currently a standard treatment for PDAC with limited clinical benefits. Angiogenesis has been shown to play an important role in the progression of primary and metastatic solid tumors including PDAC. Sunitinib (Su) is a multitarget RTK inhibitor with antiangiogenic and antitumor activities. Bevacizumab (Bev) is a recombinant anti-VEGF monoclonal antibody. Endothelial monocyte activating polypeptide II (EMAP, E) is an antiendothelial and antiangiogenic agent that enhances antitumor effects of Gem and Bev in PDAC. In experimental PDAC, we investigated combination treatment benefits of Gem with the antiangiogenic agents Su, Bev and EMAP.

The human PDAC cell line AsPC-1, the endothelial cell line HUVECs and fetal fibroblast WI-38 cells were maintained in vitro. Cell proliferation and protein expression were analyzed by WST-1 assay and Western blotting. Tumor growth and survival experiments were performed in murine xenografts. Intratumoral proliferative activity was measured using Ki67 nuclear antigen staining.

Inhibition of proliferation in AsPC-1 cells by Gem (10 μM), Bev (1 mg/ml) Su (10 μM) and EMAP (20 μM) was 45, 24, 92 and 2 percent; combination of Su with Gem, Bev or EMAP had small additive effects. In HUVECs, Gem, Bev, Su and EMAP caused 95, 23, 88 and 59 percent inhibition in cell proliferation, and combining Su with Gem, Bev and EMAP had significant additive effects. In WI-38 cells, Gem, Bev, Su and EMAP caused 95, 17, 87 and 23 percent inhibition in cell proliferation and combination of Su with Gem, Bev or EMAP had no additive effects. Sunitinib treatment either alone or in combination with Gem, Bev or EMAP induced apoptosis as observed by PARP-1 cleavage. In vivo, the inhibitory effect on tumor growth after Gem (as reference, 100) was enhanced in combination with Bev, E, Su, Bev+E, Bev+Su, E+Su and Bev+E+Su by 32, 16, 56, 38, 48, 47 and 64 percent respectively; combining antiangiogenic agents without Gem did not enhance local tumor growth inhibition. Inhibition of intra-tumoral proliferative index based on Ki67 positive cells was comparable to tumor growth inhibition data. Median animal survival in controls or Gem, Bev+Gem, E+Gem, Su+Gem, Bev+E+Gem, Su+E+Gem, Bev+Su+Gem and Bev+E+Su+Gem groups was 19, 26, 36, 36, 37, 43, 36, 27 and 46 days, respectively.

Combination of antiangiogenic agents with gemcitabine improves in vivo results, despite the differential inhibitory effects on various cell types in vitro. Sunitinib alone has benefits, and its effects are not limited to endothelial cells. Addition of Su to anti-VEGF and anti-integrin agents adds little benefit in the absence of Gem. However, the results strongly corroborate the benefits of combining multitargeting antiangiogenic agents with standard Gemcitabine therapy for PDAC treatment.

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 3294. doi:10.1158/1538-7445.AM2011-3294