N. SAITO1, Y. Shirai1, T. Horiuchi1, H. Sugano1, R. Iwase1, K. Haruki1, Y. Fujiwara1, K. Furukawa1, H. Shiba1, T. Uwagawa1, T. Ohashi2, K. Yanaga1 1The Jike University School Of Medicine,Department Of Surgery,Minato-ku, TOKYO, Japan 2The Jikei University School of Medicine,Division Of Gene Therapy, Research Center For Medical Sciences,Minato-ku, TOKYO, Japan
Introduction: NF-κB plays an important role in chemoresistance. Although gemcitabine and nab-paclitaxel therapy (GN) has been effective for pancreatic cancer, the therapeutic efficacy is attenuated by anticancer agents-induced activation of NF-κB. Meanwhile, pomalidomide is a novel immunomodulatory drug derived from thalidomide. Since thalidomide is a NF-κB inhibitor in digestive cancer, we hypothesized that pomalidomide also inhibits NF-κB activation, and enhances antitumor effects of GN for pancreatic cancer cell lines.
Methods: In vitro, we used human pancreatic cancer cell lines (MIA PaCa-2, PANC-1). We compared the antitumor effect of pomalidomide plus GN (GNP) with GN. Concentration of NF-κB, cell proliferation, cell cycle, and induction of apoptosis were evaluated by each assay. In vivo, we created xenograft orthotopic pancreatic cancer model (BALB/c with PANC-1). The animals were treated with oral polmalidomide five times a week and i.p. injection of GN once a week for 5 weeks. We evaluated sequential tumor volume by MRI and conclusive tumor weight and volume. We assessed the in vivo protein and apoptosis levels examined in vitro.
Results:
Pomalidomide suppressed GN-induced NF-κB activation (MIA PaCa-2; GN : GNP = 9.57 ± 0.47 : 7.09 ± 0.20 ng/mg; p<0.01, PANC-1; GN : GNP = 69.58 ± 5.18 : 32.34 ± 13.61 ng/mg; p<0.05). Cell viability in GNP was significantly lower than that in GN (MIA PaCa-2; GN : GNP = 51.6 ± 9.0 : 24.1 ± 7.7 % ; p?0.01 , PANC-1; GN : GNP = 70.4 ± 7.5 : 41.7 ± 2.7 % ; p?0.01).
Moreover, in GNP, the levels of apoptotic protein (cleaved caspase 8, cleaved caspase 3, cleaved PARP) were higher than those in GN. Similar to nuclear NF-κB concentrations, phosphorylated IκBα was lower in GNP than that in GN. In addition, pomalidomide suppressed the expression levels of VEGF of pancreatic cancer in a dose-dependent manner.
In vivo, the tumor weight (GN : GNP = 538 ± 36 : 385 ± 88 mg; p<0.05) and tumor volume (GN : GNP = 587 ± 51 : 313 ± 89 mm3; p=0.01) were significantly lower in GNP than those in the GN after five weeks of treatment. Moreover, immunohistochemical staining revealed down-regulation of VEGF and Ki-67 in GNP.
Conclusion: Pomalidomide inhibited NF-κB activation and enhanced the antitumor effects of GN on pancreatic cancer cells.