Caspase-3 drives apoptosis in pancreatic cancer cells after treatment with gemcitabine |
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Authors: | Chandler Nicole M. Canete Jonathan J. Callery Mark P. |
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Affiliation: | (1) Department of Surgery, University of Massachusetts Medical School, Worcester, Massachusetts;(2) Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts;(3) Division of General Surgery, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Stoneman 920, 02215 Boston, MA |
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Abstract: | Pancreatic cancer remains a highly chemoresistant malignancy. Gemcitabine, the most effective first-line agent available, acts by disrupting cellular replication. Caspases belong to a family of proteases that function as key components of the apoptotic death machinery. We investigated the mechanisms by which gemcitabine blocks proliferation and whether it can induce apoptosis in pancreatic cancer cells. Quiescent pancreatic cancer cells (BxPC-3) were stimulated to proliferate (10% fetal calf serum) with or without gemcitabine, PS-341 (26S proteasome inhibitor), or both. Proliferation was measured by MTT assay and apoptosis by propidium iodine staining. To determine activation of the apoptotic regulatory cell proteins, caspase-3 and cleavage of poly(ADP-ribose)polymerase (PARP) into its 85-kDa fragment were assessed by Western blotting. Gemcitabine at even low doses (10 micromol/L) significantly inhibited cellular proliferation, whereas PS-341 (10 nmol/L) had no effect. With combined treatment, PS-341 potentiated the antiproliferative effects of gemcitabine (P=0.001). At 48 hours, the apoptotic fraction was greatly enhanced by the presence of PS-341 compared with gemcitabine alone. Caspase-3 accumulated as early as 30 minutes and was associated with cleavage of PARP to its apoptotic fragment. Gemcitabine, a nucleoside analogue, may in part exert its antiproliferative effects by directing pancreatic cancer cells to a default pathway of apoptosis. 26S proteasome inhibition potentiates this effect, suggesting its potential clinical value against chemoresistance in pancreatic cancer. |
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Keywords: | Caspase pancreatic cancer apoptosis gemcitabine |
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