Kimberly A Clawson

University of Minnesota Duluth, Duluth, Minnesota, United States

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Publications (5)11.99 Total impact

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    ABSTRACT: Cholangiocarcinoma originates from bile duct epithelial cells in the intrahepatic and extrahepatic biliary system. We recently observed that triptolide (a diterpenoid triepoxide) is effective in inducing apoptosis in pancreatic tumors. Death receptors 4 and 5 are overexpressed in several cancer types, and their activation by tumor-necrosis factor-related apoptosis-inducing ligand (TRAIL) induces cell death. The principal objective of this study was to determine the effects of combination therapy with TRAIL and triptolide in cholangiocarcinoma. Two cholangiocarcinoma cell lines were incubated with various doses of triptolide and TRAIL, alone and in combination; cell viability was assessed at 24 and 48 h. Annexin-V staining and caspase-3 activity were measured after 24 h of triptolide, TRAIL or combination treatment. Western blots assessed protein levels of poly(ADP-ribose) polymerase (PARP) and X-linked inhibitor of apoptosis (XIAP). Combination treatment using TRAIL and triptolide decreased cell viability in all cell lines at 48 h, with greater cell killing than that which was observed with either drug alone. This decrease in viability was associated with increases in annexin-V staining and caspase-3 activity. Western blot analysis demonstrated increases in PARP cleavage and decreases in XIAP expression that were dose-dependent. TRAIL and triptolide in combination decreased cell viability and enhanced apoptosis. Furthermore, Western blot analysis suggests that triptolide sensitizes cells to TRAIL-induced apoptotic cell death by inhibiting expression of XIAP, a protein known to inhibit apoptosis. Our results demonstrate that combination of TRAIL and triptolide enhance apoptosis in cholangiocarcinoma cell lines.
    Full-text · Article · Oct 2010 · Journal of Surgical Research
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    ABSTRACT: Our recent work demonstrated that treatment of neuroblastoma with triptolide causes apoptotic cell death in vitro and decreases tumor size in vivo. Triptolide therapy has been associated with reduced expression of Hsp-70, suggesting a mechanism of cell killing involving Hsp-70 inhibition. The principal objective of this study was to investigate the role of Hsp-70 in triptolide-mediated cell death in neuroblastoma. Neuroblastoma cells were transfected with Hsp-70-specific siRNA. Viability, caspase activity, and phosphatidylserine externalization were subsequently measured. An orthotopic, syngeneic murine tumor model was developed, and randomized mice received daily injections of triptolide or vehicle. At 21 d, mice were sacrificed. Immunohistochemisty was used to characterize Hsp-70 levels in residual tumors, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was performed to identify cells undergoing apoptosis. Targeted silencing of Hsp-70 with siRNA significantly decreased cellular viability, augmented caspase-3 activity, and resulted in increased annexin-V staining. These effects parallel those findings obtained following treatment with triptolide. Residual tumors from triptolide-treated mice showed minimal staining with Hsp-70 immunohistochemistry, while control tumors stained prominently. Tumors from treated mice demonstrated marked staining with the TUNEL assay, while control tumors showed no evidence of apoptosis. Use of siRNA to suppress Hsp-70 expression in neuroblastoma resulted in apoptotic cell death, similar to the effects of triptolide. Residual tumors from triptolide-treated mice expressed decreased levels of Hsp-70 and demonstrated significant apoptosis. These findings support the hypothesis that Hsp-70 inhibition plays a significant role in triptolide-mediated neuroblastoma cell death.
    Full-text · Article · Sep 2010 · Journal of Surgical Research

  • No preview · Article · Feb 2010 · Journal of Surgical Research
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    ABSTRACT: An emerging therapy in oncology is the induction of apoptotic cell death through anti-death receptor therapy. However, pancreatic cancer is resistant to apoptosis including anti-death receptor therapy. We have previously described how triptolide decreases resistance to apoptosis in pancreatic cancer cells in vitro and in vivo. We hypothesized that triptolide decreases tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) resistance in pancreatic cancer cells. The aim of this study was to evaluate the effects that combined therapy with TRAIL and triptolide have on different parameters of apoptosis. Four different pancreatic cancer cell lines were exposed to triptolide, TRAIL, or a combination of both drugs. We assessed the effects that combined therapy with TRAIL and triptolide has on cell viability, apoptosis, caspase-3 and caspase-9 activities, and poly(ADP)-ribose polymerase cleavage. Pancreatic cancer cells were resistant to TRAIL therapy; however, combined therapy with triptolide and TRAIL significantly decreased the cell viability in all the cell lines and increased apoptotic cell death as a result of caspase-3 and caspase-9 activation. Pancreatic cancer is highly resistant to anti-death receptor therapy, but combined therapy with TRAIL and triptolide is an effective therapy that induces apoptotic cell death in pancreatic cancer cells.
    No preview · Article · Dec 2009 · Journal of Gastrointestinal Surgery
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    ABSTRACT: Heat shock protein (Hsp)-70 is overexpressed in several human malignancies, and its inhibition has been shown to kill cancer cells. Our objectives were to assess the effectiveness of triptolide, an Hsp-70 inhibitor, in treating neuroblastoma in vitro and in vivo, and to measure the associated effects on Hsp-70 levels and apoptosis markers. After exposing N2a and SKNSH cell lines to triptolide, cell viability was assessed. Caspase-3 and -9 activities were measured and annexin staining performed to determine if cell death occurred via apoptosis. Hsp-70 protein and mRNA levels were determined using Western blot and real-time polymerase chain reaction. In an orthotopic tumor model, mice received daily triptolide injections and were humanely killed at study completion with tumor measurement. Triptolide treatment resulted in dose- and time-dependent N2a cell death and dose-dependent SKNSH killing. Triptolide exposure was associated with dose-dependent increases in caspase activity and annexin staining. Triptolide decreased Hsp-70 protein and mRNA levels in a dose-dependent fashion. Mice receiving triptolide therapy had significantly smaller tumors than controls. Triptolide therapy decreased neuroblastoma cell viability in vitro and inhibited tumor growth in vivo. Our studies suggest that triptolide killed cells via apoptosis and in association with inhibition of Hsp-70 expression. Triptolide may provide a novel therapy for neuroblastoma.
    No preview · Article · Sep 2009 · Surgery