Biomedical subjects

Eric Benoit

Publications and source records attributed to Eric Benoit.

8 recordsLinked to original sources

PubMed2005

RNA interference demonstrates a novel role for integrin-linked kinase as a determinant of pancreatic adenocarcinoma cell gemcitabine chemoresistance.

Integrin-linked kinase (ILK) facilitates signal transduction between extracellular events and important intracellular survival pathways involving protein kinase B/Akt. We examined the role of ILK in determining pancreatic adenocarcinoma cellular chemoresistance to the nucleoside analogue gemcitabine. Cellular ILK expression was quantified by Western blot analysis. We examined the effects of overexpression of active ILK and of ILK knockdown induced by RNA interference on gemcitabine chemoresistance. We also examined the effects of modulating ILK expression on gemcitabine-induced caspase 3-mediated apoptosis, phosphorylation status of Akt (Ser473) and glycogen synthase kinase. Overexpression of ILK increased cellular gemcitabine chemoresistance, whereas ILK knockdown induced chemosensitization via increased caspase 3-mediated apoptosis. ILK knockdown attenuated Akt Ser473 and glycogen synthase kinase phosphorylation, whereas overexpression of constitutively active myristoylated Akt was sufficient to induce significant recovery in gemcitabine chemoresistance in the presence of ILK knockdown. Levels of ILK expression affect gemcitabine chemoresistance in pancreatic adenocarcinoma cells. This novel finding suggests that therapies directed against ILK and its downstream signaling targets may have the potential to enhance the efficacy of gemcitabine-based chemotherapy.

Adenocarcinoma↗

PubMed2004

RETRACTED: Prostaglandin E2 enhances pancreatic cancer invasiveness through an Ets-1-dependent induction of matrix metalloproteinase-2.

Accumulating evidence suggests an important role for cyclooxygenase-2 (COX-2) in the pathogenesis of a wide range of malignancies. Here we tested the hypothesis that the COX-2 product prostaglandin E(2) (PGE(2)) increases cellular invasive potential by inducing matrix metalloproteinase-2 (MMP-2) expression and activity through an extracellular signal-regulated kinase (ERK)/Ets-1-dependent mechanism in pancreatic cancer. PANC-1 and MIAPaCa-2 pancreatic cancer cells were treated with PGE(2) or rofecoxib, a selective COX-2 inhibitor. MMP-2 expression and activity were assayed using Western blot analysis and zymography, respectively. MMP-2 promoter activity was analyzed with a luciferase-based assay. Ets-1 activity was analyzed using gel shift assay. Ets-1 expression was specifically silenced using RNA interference. Cellular invasive and migratory potentials were determined using a Boyden chamber assay with or without Matrigel, respectively. Exogenous PGE(2) induced MMP-2 expression and activity and increased ERK1/2 phosphorylation, Ets-1 binding activity, and MMP-2 promoter activity. PGE(2) also increased cellular migratory and invasive potentials. The mitogen-activated protein kinase kinase inhibitor PD98059 and Ets-1 silencing each abolished PGE(2)-induced increases in MMP-2 expression. PD98059 and Ets-1 silencing each abrogated the effect of PGE(2) on cellular invasive potential but not on cellular migratory potential. Rofecoxib suppressed MMP-2 expression and activity, Ets-1 binding activity, MMP-2 promoter activity, and cellular migratory and invasive potentials. These results suggest that PGE(2) mediates pancreatic cancer cellular invasiveness through an ERK/Ets-1-dependent induction of MMP-2 expression and activity. They also suggest that COX-2 inhibition may represent a strategy to inhibit invasive potential in pancreatic cancer.

Cell Line, Tumor↗

PubMed2004

Rectal complications after prostate brachytherapy.

PURPOSE: Prostate brachytherapy is gaining wide popularity as an alternative to resection for the treatment of locally advanced prostate cancer. Rectal-urethral fistula after prostate brachytherapy is a rare but serious complication, and its incidence, presentation, risk factors, and clinical management have not been well described. METHODS: From January 1997 to October 2002, seven patients with rectal-urethral fistulas were referred to two institutions (Brigham and Women's Hospital and West Roxbury Veteran's Administration Hospital) of a major teaching referral center. Clinical presentation, risk factors, prostate staging, and clinical management were examined in a retrospective fashion. RESULTS: Seven rectal-urethral fistulas developed from roughly 700 (1 percent) patients treated with prostate brachytherapy for prostate cancer. The average patient age was 67.7 years, preimplant prostate-specific antigen was 7.1, and Gleason score was 3+3. Symptoms occurred at a mean of 27.3 months after prostate brachytherapy was started and included anorectal pain (57 percent), clear mucous discharge (57 percent), diarrhea (43 percent), and rectal ulceration (43 percent). Coronary artery disease was a common comorbidity (71 percent). Previous transurethral resection of prostate (28 percent) and pelvic irradiation or external beam radiation therapy (14 percent) were not associated with increased risk of rectal-urethral fistula. All patients underwent a diverting colostomy (86 percent) or ileostomy (14 percent), and four patients went on to have definitive therapy. Definitive resection was performed between 5 and 43 months after diverting ostomy and was chosen on the basis of comorbid disease, quality of life, and degree of operation. Two patients required a second diversion after definitive resection because of anorectal pain and a colocutaneous fistula. Postoperative complications included myocardial infarction (14 percent), blood transfusion (14 percent), and bowel perforation (14 percent). Patients became symptom-free nine months after surgery. Six patients are alive and well today; one died from an unrelated cause. CONCLUSIONS: Rectal-urethral fistula after prostate brachytherapy is a rare but devastating complication. Patients should be followed for at least three years after prostate brachytherapy because symptoms can develop late in the course. Although diversion of fecal stream does not heal the fistula, all patients diagnosed with rectal-urethral fistula should first undergo diverting ostomy to alleviate symptoms. Then, one should consider definitive resection and ostomy closure.

Aged↗

PubMed2004

Overexpression of CEACAM6 promotes insulin-like growth factor I-induced pancreatic adenocarcinoma cellular invasiveness.

Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is a glycosylphosphatidylinositol-linked immunoglobulin superfamily member that is overexpressed in a variety of human cancers. We have recently reported that suppression of CEACAM6 expression impairs pancreatic adenocarcinoma progression in vivo. In order to characterize the mechanisms through which CEACAM6 influences the malignant phenotype, CEACAM6-overexpressing Capan2 pancreatic adenocarcinoma cells were established by stable transfection. We determined the effect of CEACAM6 overexpression on cellular invasiveness towards insulin-like growth factor I (IGF-I), a peptide of critical importance in pancreatic cancer malignant cellular behavior and tumor progression. IGF-I-induced cellular invasiveness and IGF-IR expression were significantly increased in clones overexpressing CEACAM6. Using inhibitory anti-IGF-IR antibody, a requirement for IGF-IR signaling in the enhanced invasiveness towards IGF-I induced by CEACAM6 overexpression was confirmed. CEACAM6-overexpressing clones exhibited increased Akt and c-Src kinase activities, as well as higher levels of matrix metalloproteinase-2 (MMP-2) expression and activity in the presence of IGF-I. While Akt kinase is both necessary and sufficient to induce IGF-IR upregulation, c-Src kinase activity is necessary, but alone is insufficient to upregulate IGF-IR expression. CEACAM6 is an important determinant of pancreatic adenocarcinoma malignant cellular behavior and, together with its downstream targets, warrants further investigation as a therapeutic target in this disease.

Adenocarcinoma↗

PubMed2004

A novel role for carcinoembryonic antigen-related cell adhesion molecule 6 as a determinant of gemcitabine chemoresistance in pancreatic adenocarcinoma cells.

Most patients with pancreatic adenocarcinoma present with surgically incurable disease. Gemcitabine, the principal agent used to treat such patients, has little impact on outcome. Overexpression of carcinoembryonic antigen-related cell adhesion molecule (CEACAM) 6, a feature of this malignancy, is associated with resistance to anoikis and increased metastasis. The purpose of this study was to determine the role of CEACAM6 in cellular chemoresistance to gemcitabine. CEACAM6 was stably overexpressed in Capan2 cells, which inherently express very low levels of the protein. Suppression of CEACAM6 expression was achieved in BxPC3 cells, which inherently overexpress CEACAM6, by stable transfection of a CEACAM6 small interfering RNA-generating vector. The effects of modulating CEACAM6 expression on gemcitabine-induced cytotoxicity were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cytotoxicity assay, flow cytometric apoptosis quantification, caspase profiling, and Western analysis of cytoplasmic cytochrome c release. The roles of Akt and c-Src kinases as downstream targets of CEACAM6 signaling were examined. Stable overexpression of CEACAM6 in Capan2 increased gemcitabine chemoresistance, whereas CEACAM6 gene silencing in BxPC3 markedly increased the sensitivity of these cells to gemcitabine. Differential expression of CEACAM6 modulates Akt activity in a c-Src-dependent manner, and CEACAM6 overexpression appears to protect cells from cytochrome c-induced caspase 3 activation and apoptosis.

Adenocarcinoma↗

PubMed2004

Fibronectin-induced COX-2 mediates MMP-2 expression and invasiveness of rhabdomyosarcoma.

Although accumulating evidence suggests the importance of cyclooxygenase-2 (COX-2) and prostaglandin E(2) (PGE(2)) in the pathogenesis of many cancers, the mechanism by which this enzyme and its metabolite promote cancer progression is unknown. In this study, we investigated the role of COX-2 in fibronectin-induced up-regulation of rhabdomyosarcoma matrix metalloproteinase (MMP)-2 activity and cellular invasiveness. We tested three human rhabdomyosarcoma cell lines: RMS559, RD, and SJRH30. Cell attachment to fibronectin up-regulated both COX-2 expression and PGE(2) production and concomitantly enhanced MMP-2 activity. Exogenous PGE(2) stimulated MMP-2 promoter activity, increased MMP-2 expression, and increased cellular invasiveness. Aspirin and rofecoxib (non-selective and selective COX-2 inhibitor, respectively) each abolished fibronectin-associated induction of MMP-2 and induced dose-dependent reductions in cellular invasiveness. These data implicated a role for inducible COX-2 and PGE(2) in the regulation of rhabdomyosarcoma cellular invasiveness and MMP-2 activity.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2004

RETRACTED: Retrovirally mediated RNA interference targeting the M2 subunit of ribonucleotide reductase: A novel therapeutic strategy in pancreatic cancer.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editors-in-Chief, because an investigation by Harvard Medical School and the Brigham and Women’s Hospital has concluded that Figure 1A is invalid and no underlying research data are available to resolve the discrepancies or validate the reported results.

Apoptosis↗

PubMed2003

RNA interference targeting focal adhesion kinase enhances pancreatic adenocarcinoma gemcitabine chemosensitivity.

Focal adhesion kinase (FAK) is an important regulator of cellular signaling, migration, apoptosis, and cell cycle progression. We tested the hypothesis that FAK is a determinant of gemcitabine chemoresistance in pancreatic adenocarcinoma cells and examined the effect of inhibiting FAK expression on gemcitabine-induced cytotoxicity in vitro and in vivo. FAK expression was quantified by Western and Northern blots. Expression of FAK was suppressed using small interfering RNA (siRNA). Gemcitabine-induced cytotoxicity was quantified and apoptosis was characterized. Akt activity was determined by in vitro kinase assay. We assessed the therapeutic applicability of FAK siRNA in a nude mouse orthotopic xenograft model. While not affecting cellular proliferation or apoptosis in the absence of gemcitabine, FAK siRNA potentiated gemcitabine-induced cytotoxicity in vitro and in vivo. FAK siRNA treatment suppressed Akt activity, which may contribute to its chemosensitizing effect.

Adenocarcinoma↗