Pancreatic cancer (PC) is a devastating disease with almost uniform lethality despite aggressive treatment (5-year survival rate of <6%). Developing novel strategies to prevent/delay/inhibit progression of PC is currently of intense interest. Epidermal growth factor receptor (EGFR) is over-expressed in ∼87% human pancreatic cancers and plays a pivotal role in tumor cell proliferation. An interaction between ornithine decarboxylase (ODC) overexpression and EGFR was suggested by the elevation of EGFR Tyr-K activity. Clinical and preclinical studies have clearly demonstrated chemopreventive potential of difloromethyl ornithine (DFMO), an ODC inhibitor. Higher doses of gefitinib (EGFR inhibitor) and DFMO has been associated with skin- and oto-toxicity respectively. Hence, to target EGFR and ODC simultaneously, we tested the effects of lower doses of gefitinib and DFMO individually and in combination on pancreatic intraepithelial neoplasms (PanINs) and their progression to pancreatic ductal adenocarcinoma (PDAC) in p48Cre/+-LSL-KrasG12D/+ transgenic mice.

Six-week old male and female KrasG12D/+ (24-34/group) mice were fed (AIN-76A) diets containing 0%, 0.01% gefitinib, 0.1% DFMO or combination of both for 38 weeks. Pancreata were collected, weighed, and evaluated histopathologically for PanINs and PDAC. To understand molecular mechanisms, we analyzed levels of proliferation, apoptosis and cell cycle makers; PCNA, p21, β-catenin, Cav-1, Bcl-XL, c-MYC, cyclin E and pERK expressions by IHC, IHF, Western blotting, and/or RT-PCR methods. Results suggest that control diet fed mice showed 80 and 65% incidence of PDAC in male and female mice, respectively. Dietary gefitinib and DFMO significantly inhibited incidence of PDAC in both male (90 & 87%, respectively, p<0.0001) and female (84 & 75%, respectively, p<0.0001) mice. Most importantly, the combination drug treatment showed complete (100%, p<0.0001) inhibition of PDAC incidence in both genders of mice. Also, significant suppression of PanIN 3 (carcinoma in-situ) was observed in mice fed by gefitinib, DFMO and their combination. Importantly, ∼77% of the pancreas was free from lesions and carcinoma in the combination treatment compared to only 4 % in control and 39 and 23 % in gefitinib and DFMO fed mice respectively. The pancreas of mice fed combination diets showed a significant inhibition of PCNA, β-catenin, Cav-1, Bcl-XL, c-MYC, cyclin E and pERK expression levels (p<0.05-0.001); and increased p21 when compared to the pancreatic cancer derived from control diet or individual drug fed mice. In summary, targeting the EGFR and ODC pathways simultaneously may provide synergistic and/or additive chemopreventive effects in suppression of PC and has significant potential for undertaking clinical trials of pancreatic cancer chemoprevention. {Supported by NCI-CN-N01-53300}.

Citation Format: Altaf Mohammed, Naveena B. Janakiram, Rebekah L. Ritchie, Laura Biddick, Misty Brewer, Stan Lightfoot, Vernon E. Steele, Chinthalapally V. Rao. Combinational Targeting of EGFR and ODC pathways by Gefitinib and DFMO lead to complete blockade of PanIN progression to pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2969. doi:10.1158/1538-7445.AM2014-2969