Efficacy of systemic therapy in advanced pancreatic carcinoma

Calcitriol enhances gemcitabine anti-tumor activity in vitro and in vivo by promoting apoptosis in a human pancreatic carcinoma model system

Gemcitabine is the standard care chemotherapeutic agent to treat pancreatic cancer. Previously we demonstrated that calcitriol (1, 25-dihydroxycholecalciferol) has significant anti-proliferative effects in vitro and in vivo in multiple tumor models and enhances the activity of a variety of chemotherapeutic agents. We therefore investigated whether calcitriol could potentiate the cytotoxic activity of gemcitabine in the human pancreatic cancer Capan-1 model system. Isobologram analysis revealed that calcitriol and gemcitabine had synergistic antiproliferative effect over a wide range of drug concentrations. Calcitriol did not reduce the cytidine deaminase activity in Capan-1 tumors nor in the livers of Capan-1 tumor bearing mice. Calcitriol and gemcitabine combination promoted apoptosis in Capan-1 cells compared with either agent alone. The combination treatment also increased the activation of caspases-8, -9, -6 and -3 in Capan-1 cells. This result was confirmed by substrate-based caspase activity assay. Akt phosphorylation was reduced by calcitriol and gemcitabine combination treatment compared to single agent treatment. However, ERK1/2 phosphorylation was not modulated by either agent alone or by the combination. Tumor regrowth delay studies showed that calcitriol in combination with gemcitabine resulted in a significant reduction of Capan-1 tumor volume compared to single agent treatment. Our study suggests that calcitriol and gemcitabine in combination promotes caspase-dependent apoptosis, which may contribute to increased anti-tumor activity compared to either agent alone.

Inactivation of Lactobacillus leichmannii ribonucleotide reductase by 2',2'-difluoro-2'-deoxycytidine 5'-triphosphate: covalent modification

Ribonucleotide reductase (RNR) from Lactobacillus leichmannii, a 76 kDa monomer using adenosylcobalamin (AdoCbl) as a cofactor, catalyzes the conversion of nucleoside triphosphates to deoxynucleotides and is rapidly (<30 s) inactivated by 1 equiv of 2',2'-difluoro-2'-deoxycytidine 5'-triphosphate (F(2)CTP). [1'-(3)H]- and [5-(3)H]F(2)CTP were synthesized and used independently to inactivate RNR. Sephadex G-50 chromatography of the inactivation mixture revealed that 0.47 equiv of a sugar was covalently bound to RNR and that 0.71 equiv of cytosine was released. Alternatively, analysis of the inactivated RNR by SDS-PAGE without boiling resulted in 33% of RNR migrating as a 110 kDa protein. Inactivation of RNR with a mixture of [1'-(3)H]F(2)CTP and [1'-(2)H]F(2)CTP followed by reduction with NaBH(4), alkylation with iodoacetamide, trypsin digestion, and HPLC separation of the resulting peptides allowed isolation and identification by MALDI-TOF mass spectrometry (MS) of a (3)H/(2)H-labeled peptide containing C(731) and C(736) from the C-terminus of RNR accounting for 10% of the labeled protein. The MS analysis also revealed that the two cysteines were cross-linked to a furanone species derived from the sugar of F(2)CTP. Incubation of [1'-(3)H]F(2)CTP with C119S-RNR resulted in 0.3 equiv of sugar being covalently bound to the protein, and incubation with NaBH(4) subsequent to inactivation resulted in trapping of 2'-fluoro-2'-deoxycytidine. These studies and the ones in the preceding paper (DOI: 10.1021/bi9021318 ) allow proposal of a mechanism of inactivation of RNR by F(2)CTP involving multiple reaction pathways. The proposed mechanisms share many common features with F(2)CDP inactivation of the class I RNRs.

FTY720, a synthetic compound from Isaria sinclairii, inhibits proliferation and induces apoptosis in pancreatic cancer cells

FTY720, a synthetic compound produced by modification of a metabolite from Isaria sinclairii, is known as a unique immunosuppressive agent that exerts its activity by inducing apoptosis of lymphocytes [S. Suzuki, FTY720: Mechanisms of action and its effect on organ transplantation, Transplant. Proc. 31 (1999) 2779-2782]. Additionally, it has been found that FTY720 has inhibitory effects on various cancer growth and metastasis [J.D. Wang, S. Takahara, N. Nonomura, Early induction of apoptosis in androgen-independent prostate cancer cell line by FTY720 requires caspase-3 activation, Prostate 40 (1999) 50-55]. To investigate its effect on the growth and metastasis of pancreatic cancer, FTY720 was used to treat three pancreatic cancer cell lines (BxPC-3, AsPC-1, and PANC-1). The MTT assay and flow cytometry were used to evaluate the cell death after FTY720 treatment; the wound closure assay, three-dimensional (3D) Matrigel assay, and invasive assay were used to evaluate the migration, colony formation and invasion abilities after FTY720 treatment, respectively. Protein expression in BxPC-3, AsPC-1, and PANC-1 cells after FTY720 treatment was detected by Western blotting. The MTT assay indicated that the growth of pancreatic cancer cells could be inhibited by FTY720 at various concentrations between 0 and 17 microM in a dose-dependent manner, which was also confirmed by flow cytometry. The wound closure assay, 3D Matrigel assay and cell invasion assay all showed that FTY720 significantly suppressed migration, colony formation and invasion ability of cancer cells at concentrations from 5 to 17 microM. After FTY720 treatment, the phospho-Akt, Bcl-2, pro-caspase-3 expression were down-regulated while the caspase-9 protein expression was increased. In conclusion, FTY720 can inhibit the growth, migration and invasion of pancreatic cancer cells. Our study provides a preclinical support for chemotherapeutic approach with FTY720 for the treatment of pancreatic cancer.