Abstract 2459: Interferon-α contributes to combined chemotherapy for CD133+ cancer stem cells in pancreatic cancer

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Abstract Objectives: Pancreatic cancer is a highly lethal disease because of high resistance to anti-cancer agents. Recent evidence suggests that a small population of cancer stem cells (CSCs) in solid tumors sustain tumor formation, self-renewal and drug resistance. CD133+ CSCs are reportedly essential for the development and perpetuation of pancreatic cancer and may account for resistance to standard chemotherapy drugs such as gemcitabine (GEM). Interferon-alpha (IFN-α) is a cytokine with pleiotropic effects, possessing direct cytotoxic and cytostatic effects on tumor cells. In the present study, we investigate the effect of IFN-α on combined chemotherapy in CD133+ pancreatic cancer cells. Methods: CD133+ and CD133− populations of Capan-1 cells, a human pancreatic cancer cell line, were isolated by FACS, and sphere formation assay and tumorigenic assay were performed. Capan-1 cells were treated by GEM with or without IFN-α and BrdU assay was used for cell-cycle analysis. Growth of xenograft tumors in nude mice was assessed after 3-weeks treatment with vehicle, GEM (1200 mg/kg/wk) alone, IFN-α (20000 U/mouse/every 2 days) alone or GEM combined with IFN-α. Results: 1) CD133+ population of Capan-1 cells showed CSC-like properties such as generation of spheres in the serum-free culture and tumorigenesis when implanted into NOD/SCID mice. 2) The growth inhibition by GEM treatment (IC50: 100 ng/mL) showed a significant difference between CD133+ and CD133− populations of Capan-1 cells, resulting in an increase of the CD133+ population. Similarly, CD133 protein levels increased in a time-dependent manner after GEM treatment by Western blot. 3) GEM treatment reduced S phase of both CD133+ and CD133− cells, and significantly induced apoptosis of CD133− cells more than that of CD133+ cells by BrdU assay. However, GEM treatment increased G0/G1 phase of CD133+ cells, indicating that CD133+ cells showed GEM resistance through the increase of G0/G1 phase. 4) All Capan-1 cells expressed IFN-α/β receptor II by FCM and immunohistochemical analyses and IFN-α (MED: 5000 U/mL) treatment reduced the CD133+ population ratio of Capan-1 cells. Importantly, IFN-α showed not only the decrease of G0/G1 phase but also the increase of S phase in CD133+ cells. Consequently, GEM combined with IFN-α treatment significantly increased the apoptotic phases in both CD133+ and CD133− cells. 5) In the in vivo experiment, GEM combined with IFN-α treatment similarly suppressed the tumor growth of Capan-1 cells. Conclusions: Our results indicate that IFN-α contributes to combined chemotherapy for CD133+ pancreatic cancer stem cells by modulating the cell cycle and/or cell proliferation, suggesting a clinical potential for treatment of pancreatic CSCs. Further investigation of the interactions between IFN-α and key regulatory pathways in CSC should be considered. 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 2459. doi:10.1158/1538-7445.AM2011-2459