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Biomedical subjects

Murray Korc

Publications and source records attributed to Murray Korc.

At least 19 recordsLinked to original sources
PubMed2007

Expression and differential signaling of heregulins in pancreatic cancer cells.

The EGF family of ligands and receptors plays an important role in the pathogenesis of pancreatic ductal adenocarcinoma (PDAC) and contributes to its aggressiveness. A number of molecular approaches have been developed to block these pathways, and studies have already proven the clinical benefit of this concept in PDAC. In the present study, we sought to determine the potential role of heregulins (HRGs), a family of EGF-like growth factors, in PDAC. Quantitative RT-PCR analysis revealed that HRGs as well as its signaling ErbB receptors were present in 4 of 4 human pancreatic cancer cell lines (PCCL). HRG-beta1 stimulated the growth of 3 of 4 PCCL, whereas HRG-alpha1 inhibited cell growth in 3 of 4 cell lines. Responses towards HRGs could in part be predicted by ErbB2 and ErbB3 expression levels. HRGs induced phosphorylation of different ErbB receptors as well as activation of MAPK, p38MAPK, JNK and PI3K in a cell- and ligand-specific manner. In vivo, HRG was upregulated in pancreatic cancer tissues and localized predominantly in the cancer cells. High HRG-beta levels but not HRG-alpha levels were associated with decreased patient survival. In conclusion, HRG is expressed by pancreatic cancer cells and influences pancreatic cancer cell growth and patient survival.

Cell Line, Tumor↗
PubMed2007

The histone deacetylase inhibitor suberoylanilide hydroxamic acid induces growth inhibition and enhances gemcitabine-induced cell death in pancreatic cancer.

PURPOSE: Pancreatic cancer is an aggressive human malignancy that is generally refractory to chemotherapy. Histone deacetylase inhibitors are novel agents that modulate cell growth and survival. In this study, we sought to determine whether a relatively new histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA), inhibits pancreatic cancer cell growth. EXPERIMENTAL DESIGN: The effects of SAHA on the growth of three pancreatic cancer cell lines (BxPC3, COLO-357, and PANC-1) were examined with respect to cell cycle progression, p21 induction and localization, and interactions with the nucleoside analogue gemcitabine. RESULTS: SAHA induced a G(1) cell cycle arrest in BxPC-3 cells and COLO-357 cells but not in PANC-1 cells. This arrest was dependent, in part, on induction of p21 by SAHA, as p21 was not induced in PANC-1 cells, and knockdown of p21 using small interfering RNA oligonucleotides nearly completely suppressed the effects of SAHA on cell cycle arrest in COLO-357 and partly attenuated the effects of SAHA in BxPC-3. COLO-357 and BxPC-3 cells, but not PANC-1 cells, were also sensitive to gemcitabine. In the gemcitabine-resistant PANC-1 cells, a 48-h cotreatment with SAHA rendered the cells sensitive to the inhibitory and proapoptotic effects of gemcitabine. An additive effect on growth inhibition by SAHA and gemcitabine was observed in COLO-357 and BxPC-3 cells. Moreover, analysis of p21 distribution in COLO-357 cells revealed that SAHA induced the cytoplasmic localization of both p21 and phospho-p21. CONCLUSIONS: These data indicate that SAHA exerts proapoptotic effects in pancreatic cancer cells, in part, by up-regulating p21 and sequestering it in the cytoplasm, raising the possibility that SAHA may have therapeutic potential in the treatment of pancreatic cancer.

Animals↗
PubMed2006

Suppression of transforming growth factor beta signalling aborts caerulein induced pancreatitis and eliminates restricted stimulation at high caerulein concentrations.

BACKGROUND: Transforming growth factors betas (TGF-betas) are implicated in pancreatic tissue repair but their role in acute pancreatitis is not known. To determine whether endogenous TGF-betas modulate the course of caerulein induced acute pancreatitis, caerulein was administered to wild-type (FVB-/-) and transgenic mice that are heterozygous (FVB+/-) for expression of a dominant negative type II TGF-beta receptor. METHODS: After 7 hourly supramaximal injections of caerulein, the pancreas was evaluated histologically and serum was assayed for amylase and lipase levels. Next, the effects of caerulein on amylase secretion were determined in mouse pancreatic acini, and cholecystokinin (CCK) receptor expression was assessed. RESULTS: The normal mouse pancreas was devoid of inflammatory cells whereas the pancreas from transgenic mice contained lymphocytic infiltrates. Caerulein injection in wild-type mice resulted in 6- and 36-fold increases in serum amylase and lipase levels, respectively, increased serum trypsinogen activation peptide (TAP) levels, gross oedema and a marked inflammatory response in the pancreas that consisted mainly of neutrophils and macrophages. By contrast, FVB+/- mice exhibited minimal alterations in response to caerulein with attenuated neutrophil-macrophage infiltrates. Moreover, acini from FVB+/- mice did not exhibit restricted stimulation at high caerulein concentrations, even though CCK receptor mRNA levels were not decreased. CONCLUSION: Our findings indicate that a functional TGF-beta signalling pathway may be required for caerulein to induce acute pancreatitis and for the CCK receptor to induce acinar cell damage at high ligand concentrations. Our results also support the concept that restricted stimulation at high caerulein concentrations contributes to the ability of caerulein to induce acute pancreatitis.

Acute Disease↗
PubMed2006

FXYD3 is overexpressed in pancreatic ductal adenocarcinoma and influences pancreatic cancer cell growth.

The expression and localization of FXYD domain containing ion transport regulator 3 (FXYD3), a transmembrane protein that acts as a chloride channel or chloride channel regulator, was analyzed in pancreatic tissues derived from donors and patients suffering from chronic pancreatitis (CP) or pancreatic ductal adenocarcinoma (PDAC) as well as in pancreatic cancer cells using QRT-PCR, laser-capture microdissection and microarray analysis, in situ hybridization and immunohistochemistry. FXYD3 antisense expressing T3M4 pancreatic cancer cells were generated and compared to control cells using anchorage-dependent and independent growth assays, and xenotransplantation into nude mice. FXYD3 mRNA levels were 3.4-fold increased in PDAC tissues compared to donor specimens (p = 0.006), and 3.9-fold increased in microdissected cancer cells compared to normal pancreatic ductal cells (p = 0.02). FXYD3 was localized in the tubular complexes and PanIN lesions of both CP and PDAC, as well as in pancreatic cancer cells. Downregulation of FXYD3 by stable antisense transfection increased significantly the doubling time of T3M4 pancreatic cancer cells from 44 +/- 2 hr to 55 +/- 12 hr (p = 0.02). Nude mice transplanted with antisense transfected cells displayed a significant increase in tumor doubling time from 3.3 days +/- 1.0 to 4.3 days +/- 0.43 (p = 0.058). Anchorage-independent growth and sensitivity to 5-fluorouracil, gemcitabine and cisplatin as well as to MgCl(2) were not dependent on the level of FXYD3 expression. In conclusion, overexpression of FXYD3 in pancreatic cancer may contribute to the proliferative activity of this malignancy.

Adenocarcinoma↗
PubMed2006

Advances, challenges, and limitations in serum-proteome-based cancer diagnosis.

Recent advances in medicine have dramatically reduced the incidence and mortality of many cardiovascular, infectious, and certain neoplastic diseases; the overall mortality for most malignant solid tumors remains high. The poor prognosis in these cancers is due, in part, to the absence of adequate early screening tests, leading to delays in diagnosis. Three strategies have been applied to fight cancer: analysis of the molecular mechanisms involved in its pathogenesis and progression, improvement of early diagnosis, and the development of novel treatment strategies. There have been major advances in our understanding of cancer biology and pathogenesis and in the development of new (targeted) treatment modalities. However, insufficient progress has been made with respect to improving the methods for the early diagnosis and screening of many cancers. Therefore, cancer is often diagnosed at advanced stages, delaying timely treatment and leading to poor prognosis. Proteome analysis has recently been used for the identification of biomarkers or biomarker patterns that may allow for the early diagnosis of cancer. This tool is of special interest, since it allows for the identification of tumor-derived secretory products in serum or other body fluids. In addition, it may be used to detect reduced levels or loss of proteins in the serum of cancer patients that are present in noncancer individuals. These changes in the serum proteome may result from cancer-specific metabolic or immunological alterations, which are, at least partly, independent of tumor size or mass, thereby facilitating early discovery.

Biomarkers, Tumor↗
PubMed2006

Defined localization of nestin-expressing cells in L-arginine-induced acute pancreatitis.

OBJECTIVE: Nestin is a stem cell marker originally described as an intermediate filament protein expressed in neuroepithelial stem cells. In the pancreas, a small number of nestin-expressing cells, which are believed to represent either stem cells or progenitor cells, are known to be present in islets, as well as in some stellate cells, pericytes, and endothelial cells. We monitored pancreatic nestin expression to delineate the location of stem cells/progenitor cells in the pancreas after L-arginine-induced pancreatitis. METHODS: Male Wistar rats received 2 intraperitoneal injections of L-arginine, each consisting of 250 mg/100 g of body weight, and were killed 3, 6, and 12 hours and 1, 4, 7, and 14 days later. RESULTS: Serum amylase and lipase levels increased after L-arginine injection, maximal levels occurring at 3 and 12 hours postinjection, respectively. Six hours after L-arginine injection, interstitial edema was observed in the pancreas, whereas on day 4 postinjection, there was severe pancreatic necrosis. Neovascularization and ductal-ductular proliferation were also present in the pancreas. Immunohistochemical analysis revealed increased Ki-67 labeling in acinar cells and capillary endothelial cells. Immunoblotting using antinestin antibody revealed increased nestin expression after L-arginine injection. In the control rat pancreas, nestin immunoreactivity was detected in a few capillary endothelial cells in some islets. After L-arginine injection, nestin was expressed in proliferating capillary endothelial cells, in stellate cells surrounding ductular structures and in submesothelial cells. CONCLUSIONS: Transient nestin expression occurs in specific cell types during the proliferative stage after recovery from L-arginine-induced pancreatitis and may represent the contribution of stem cells and/or progenitor cells to the regenerative capacity of the pancreas.

Acute Disease↗
PubMed2006

Connective tissue growth factor-specific antibody attenuates tumor growth, metastasis, and angiogenesis in an orthotopic mouse model of pancreatic cancer.

Connective tissue growth factor (CTGF) plays an important role in fibrosis by modulating cell migration and cell growth but may also modify tumor growth and metastasis. Because CTGF is overexpressed in pancreatic ductal adenocarcinoma, we investigated the in vitro effects of CTGF on the proliferation and invasiveness of PANC-1 pancreatic cancer cells and examined the consequences of its in vivo inhibition on the growth and metastasis of these cells using a fully human CTGF-specific monoclonal antibody (FG-3019) in an orthotopic nude mouse model. Although PANC-1 cells expressed relatively high levels of endogenous CTGF mRNA, the addition of CTGF to conditioned medium increased the proliferation and invasiveness of PANC-1 cells. Moreover, transforming growth factor-beta1 caused a further increase in CTGF expression in these cells. In vivo, the twice weekly i.p. administration of FG-3019 decreased tumor growth and metastasis and attenuated tumor angiogenesis and cancer cell proliferation. FG-3019 did not enhance apoptosis and did not attenuate the inhibitory effects of gemcitabine on tumor growth and metastasis. These findings suggest that CTGF may contribute to aberrant autocrine and paracrine pathways that promote pancreatic cancer cell growth, invasion, metastasis, and angiogenesis. Therefore, blocking CTGF actions with FG-3019 may represent a novel therapeutic approach in pancreatic ductal adenocarcinoma.

Animals↗
PubMed2006

Yes-associated protein (YAP65) in relation to Smad7 expression in human pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by multiple alterations in the TGF-beta signaling pathway. Yes-associated protein (YAP65) interacts with Smad7 thereby influencing TGF-beta signaling. In the present study, the expression of YAP65 in PDAC was analyzed in order to elucidate the potential role of this molecule in the pathogenesis of pancreatic cancer. YAP65 mRNA expression levels in human pancreatic tissue samples and cell lines were analyzed by Northern blotting and quantitative RT-PCR. Immunohistochemistry was carried out to localize and quantify YAP65 expression in relation to Smad7 expression and Smad4 mutations. The effects of TGF-beta1 on Smad7 and YAP65 mRNA expression were analyzed by quantitative RT-PCR. Enhanced expression of YAP65 mRNA was identified by Northern blotting and quantitative RT-PCR in PDAC in comparison to the normal pancreas (2.5-fold increase) and to chronic pancreatitis (1.3-fold increase). In the normal pancreas, YAP65 was absent in acinar cells, large ducts and islet cells, but exhibited moderate to strong immunoreactivity in centroacinar cells and ductules. Tubular complexes in CP and CP-like lesions in PDAC also exhibited strong staining. In contrast, weak to moderate YAP65 immunoreactivity was present in the cancer cells. There was no correlation between YAP65 immunostaining and Smad7 staining or Smad4 mutations in the cancer samples. TGF-beta1 strongly induced Smad7 mRNA in Colo-357 and in Panc-1 cells, but only slightly induced YAP65 mRNA in Colo-357 cells. In conclusion, YAP65 is expressed mainly in centroacinar and small ductal cells in the normal pancreas. In PDAC, YAP65 is present in tubular complexes and to a lesser extent in cancer cells. Together with the known function of YAP65 in different growth and differentiation regulating pathways, it is suggested that this gene plays a role in the normal and diseased pancreas.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Correlation of glypican-1 expression with TGF-beta, BMP, and activin receptors in pancreatic ductal adenocarcinoma.

Glypican1 (GPC1) is a cell surface heparan sulfate proteoglycan that acts as a co-receptor for heparin-binding growth factors as well as for members of the TGF-beta family. GPC1 plays a role in pancreatic cancer by regulating growth factor responsiveness. In view of the importance of members of the TGF-beta family in pancreatic cancer, in the present study, the role of GPC1 in TGF-beta, BMP and activin signaling was analyzed. Quantitative RT-PCR and immunohistochemistry were utilized to analyze GPC1 and TGF-beta, BMP and activin receptor expression levels. Panc-1 and T3M4 pancreatic cancer cells were transfected in a stable manner with a GPC1 antisense expression construct. Anchorage-dependent and -independent growth was determined by MTT and soft agar assays. TGF-beta1, activin-A and BMP-2 responsiveness was determined by MTT assays and immunoblotting with p21, p-Smad1, and p-Smad2 antibodies. QRT-PCR demonstrated increased GPC1 mRNA levels in pancreatic ductal adenocarcinoma (PDAC) compared to normal pancreatic tissues (NPT), as described previously. There was a significant correlation between GPC1 mRNA levels and TbetaRII, act-R1a, act-R1b, act-R2a, BMP-R1a, and BMP-R2 mRNA expression in NPT. In contrast, GPC1 mRNA expression correlated directly with act-R1a and BMP-R1a in N0 PDAC cases and with act-R2a and BMP-R1a in lymph node positive cases. Down-regulation of GPC1 resulted in increased doubling time in Panc-1 but not in T3M4 cells, and decreased anchorage-independent growth in both cell lines. GPC1 down-regulation resulted in a slightly altered response towards TGF-beta1, activin-A and BMP-2 in terms of growth, p21 induction and Smad2 phosphorylation. In conclusion, enhanced GPC1 expression correlates with BMP and activin receptors in pancreatic cancer. GPC1 down-regulation suppresses pancreatic cancer cell growth and slightly modifies signaling of members of the TGF-beta family of growth factors.

Activin Receptors↗
PubMed2005

Growth factor-induced shedding of syndecan-1 confers glypican-1 dependence on mitogenic responses of cancer cells.

The cell surface heparan sulfate proteoglycan (HSPG) glypican-1 is up-regulated by pancreatic and breast cancer cells, and its removal renders such cells insensitive to many growth factors. We sought to explain why the cell surface HSPG syndecan-1, which is also up-regulated by these cells and is a known growth factor coreceptor, does not compensate for glypican-1 loss. We show that the initial responses of these cells to the growth factor FGF2 are not glypican dependent, but they become so over time as FGF2 induces shedding of syndecan-1. Manipulations that retain syndecan-1 on the cell surface make long-term FGF2 responses glypican independent, whereas those that trigger syndecan-1 shedding make initial FGF2 responses glypican dependent. We further show that syndecan-1 shedding is mediated by matrix metalloproteinase-7 (MMP7), which, being anchored to cells by HSPGs, also causes its own release in a complex with syndecan-1 ectodomains. These results support a specific role for shed syndecan-1 or MMP7-syndecan-1 complexes in tumor progression and add to accumulating evidence that syndecans and glypicans have nonequivalent functions in vivo.

Cell Line, Tumor↗
PubMed2005

Suppression of ovarian cancer cell tumorigenicity and evasion of Cisplatin resistance using a truncated epidermal growth factor receptor in a rat model.

The overexpression of the epidermal growth factor receptor (EGFR) is associated with a poor prognosis in ovarian cancer. The dominant-negative EGFR (EGFR-DNR) is a truncated receptor that lacks the tyrosine kinase domain and is devoid of signaling capability. This study tested the effects of a EGFR-DNR approach in ovarian cancer cells. NuTu-19, a rat ovarian cancer cell line was rendered resistant to cisplatin. Both NuTu-19 and resistant cells were infected with a retroviral vector containing the EGFR-DNR. NuTu-19 and NuTu-DNR (NuTu-19 cells expressing the EGFR-DNR) were injected into Fisher 344 immunocompetent rats. Western blot analyses were used to assess signal transduction pathways. All rats injected with NuTu-DNR cells remained healthy following tumor injection. In contrast, 100% of the rats injected with the NuTu-19 and NuTu-Sham (NuTu-19 cells expressing an empty vector) died of disease progression at the end of 15 weeks (P = 0.00009). On Western blot analysis, both NuTu-19 and NuTu-Sham cells showed a strong activation of mitogen-activated protein kinase (MAPK) after exposure to EGF. Cisplatin-resistant cell lines showed an enhanced EGF stimulatory effect via the MAPK pathway compared with parental cells. The EGFR-DNR significantly reduced the ability of EGF to induce cell signaling through the MAPK pathway. Lastly, the EGFR-DNR can partially reverse cisplatin resistance in drug-resistant cells. The EGFR-DNR approach suggests that EGFR confers a growth advantage to NuTu-19 cells in vivo. Thus, EGFR blockade may ultimately prove to be a useful therapeutic tool in the treatment of cisplatin-sensitive and cisplatin-resistant ovarian cancers.

Animals↗
PubMed2005

Smad7 abrogates transforming growth factor-beta1-mediated growth inhibition in COLO-357 cells through functional inactivation of the retinoblastoma protein.

Smad7 is overexpressed in 50% of human pancreatic cancers. COLO-357 pancreatic cancer cells engineered to overexpress Smad7 are resistant to the actions of transforming growth factor-beta1 (TGF-beta1) with respect to growth inhibition and cisplatin-induced apoptosis but not with respect to modulation of gene expression. To delineate the mechanisms underlying these divergent consequences of Smad7 overexpression, we studied the effects of Smad7 on TGF-beta1-dependent signaling pathways and cell cycle regulating proteins. TGF-beta1 induced the phosphorylation of MAPK, p38 MAPK, and AKT2 irrespective of the levels of Smad7, and inhibitors of these pathways did not alter TGF-beta1 actions on cell growth. By contrast, Smad7 overexpression interfered with TGF-beta1-mediated attenuation of cyclin A and B levels, inhibition of cdc2 dephosphorylation and CDK2 inactivation, up-regulation of p27, and the maintenance of the retinoblastoma protein (RB) in a hypophosphorylated state. Smad7 also suppressed TGF-beta1-mediated inhibition of E2F activity but did not alter TGF-beta1-mediated phosphorylation of Smad2, the nuclear translocation of Smad2/3/4, or DNA binding of the Smad2/3/4 complex. Although Smad7 did not associate with the type I TGF-beta receptor (TbetaRI), SB-431542, an inhibitor of the kinase activity of this receptor, blocked TGF-beta1-mediated effects on Smad-2 phosphorylation. These findings point toward a novel paradigm whereby Smad7 acts to functionally inactivate RB and de-repress E2F without blocking the activation of TbetaRI and the nuclear translocation of Smad2/3, thereby allowing for TGF-beta1 to exert effects in a cancer cell that is resistant to TGF-beta1-mediated growth inhibition.

Active Transport, Cell Nucleus↗
PubMed2005

Restoration of Smad4 in BxPC3 pancreatic cancer cells attenuates proliferation without altering angiogenesis.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive human malignancy in which the transforming growth factor beta (TGF-beta) signal transducer, Smad4, is commonly mutated or deleted. BxPC3 human pancreatic cancer cells exhibit a homozygous deletion of the Smad4 gene, yet are growth inhibited by TGF-beta1. In the present study, we sought to determine whether reintroduction of Smad4 into BxPC3 cells alters their behavior in vitro and in vivo. Sham transfected and Smad4 expressing BxPC3 cells exhibited similar responses to TGF-beta1 with respect to p21 upregulation, hypophosphorylation of the RB protein, Smad2 phosphorylation, and Smad2/3 nuclear translocation. TGF-beta1 did not alter p27 expression, and silencing of p21 with an appropriate siRNA markedly attenuated TGF-beta1-mediated growth inhibition. Nonetheless, the presence of Smad4 was associated in vitro with a more prolonged doubling time, enhanced sensitivity to the growth inhibitory actions of exogenous TGF-beta1, and a more flattened cellular morphology. In vivo, Smad4 expression resulted in delayed tumor growth and decreased cellular proliferation, without effects on either apoptosis or angiogenesis. These findings indicate that, in spite of the absence of Smad4, growth inhibition in BxPC3 cells by TGF-beta1 is dependent on p21 upregulation and maintenance of RB in a hypophosphorylated, active state. Moreover, the presence of a functional Smad4 attenuates the capacity of BxPC3 cells to proliferate in vivo. However, this effect is transient, indicating that Smad4 growth inhibitory actions are circumvented in the later stages of pancreatic tumorigenicity.

Active Transport, Cell Nucleus↗
PubMed2004

Membrane-associated heparan sulfate proteoglycans are involved in the recognition of cellular targets by NKp30 and NKp46.

Lysis of virus-infected and tumor cells by NK cells is mediated via natural cytotoxicity receptors (NCRs). We have recently shown that the NKp44 and NKp46 NCRs, but not the NKp30, recognize viral hemagglutinins. In this study we explored the nature of the cellular ligands recognized by the NKp30 and NKp46 NCRs. We demonstrate that target cell surface heparan sulfate proteoglycans (HSPGs) are recognized by NKp30 and NKp46 and that 6-O-sulfation and N-acetylation state of the glucose building unit affect this recognition and lysis by NK cells. Tumor cells expressing cell surface heparanase, CHO cells lacking membranal heparan sulfate and glypican-1-suppressed pancreatic cancer cells manifest reduced recognition by NKp30 and NKp46 and are lysed to a lesser extent by NK cells. Our results are the first clue for the identity of the ligands for NKp30 and NKp46. Whether the ligands are particular HSPGs, unusual heparan sulfate epitopes, or a complex of HSPGs and either other protein or lipid moieties remains to be further explored.

Animals↗
PubMed2004

Glypican-1 antisense transfection modulates TGF-beta-dependent signaling in Colo-357 pancreatic cancer cells.

The heparan sulfate proteoglycan glypican-1 is essential as a co-receptor for heparin binding growth factors, such as HB-EGF and FGF-2, in pancreatic cancer cells. In the present study, the role of glypican-1 in the regulation of TGF-beta signaling was investigated. Colo-357 pancreatic cancer cells were stably transfected with a full-length glypican-1 antisense construct. Cell growth was determined by MTT and soft agar assays. TGF-beta1 induced p21 expression and Smad2 phosphorylation were analyzed by immunoblotting. PAI-1 promoter activity was determined by luciferase assays. Down-regulation of glypican-1 expression by stable transfection of a full-length glypican-1 antisense construct resulted in decreased anchorage-dependent and -independent cell growth in Colo-357 pancreatic cancer cells and attenuated TGF-beta1 induced cell growth inhibition, Smad2 phosphorylation, and PAI-1 promoter activity. There was, however, no significant difference in TGF-beta1 induced p21 expression and Smad2 nuclear translocation. In conclusion, glypican-1 is required for efficient TGF-beta1 signaling in pancreatic cancer cells.

Cell Division↗