C-JUN and CPP32 (CASPASE 3) in human pancreatic cancer: relation to cell proliferation and death

GPX3 represses pancreatic cancer cell proliferation, migration and invasion, and improves their chemo‑sensitivity by regulating the JNK/c‑Jun signaling pathway

Pancreatic cancer (PC) is a deadly and aggressive disease, which is characterized by poor prognosis. It has been reported that glutathione peroxidase 3 (GPX3) is involved in the development of several types of cancer. The present study aimed to explore the regulatory role of GPX3 in PC and uncover its underlying mechanism. Bioinformatics analysis was initially carried out to predict the expression profile of GPX3 in PC and its association with prognosis. The expression levels of GPX3 were also detected in PC cells by reverse transcription-quantitative PCR and western blot analysis. Following transfection to induce GPX3 overexpression, the proliferation ability of PC cells was assessed by Cell Counting Kit-8, colony formation and 5-ethynyl-2'-deoxyuridine incorporation assays. In addition, wound healing and Transwell assays were performed to evaluate the migration and invasion abilities of PC cells. Cell apoptosis was assessed by flow cytometric analysis. The expression levels of epithelial-mesenchymal transition (EMT)-, apoptosis-, and JNK signaling-related proteins were detected by western blot analysis. Additionally, for rescue experiments, JNK signaling was activated following cell treatment with anisomycin. The results showed that GPX3 was downregulated in PC and its expression was associated with favorable prognosis. In addition, cell transfection-induced GPX3 overexpression markedly inhibited cell proliferation, migration and invasion, and inhibited EMT. In addition, GPX3 improved the chemo-sensitivity of PC and gemcitabine (GEM)-resistant PC cells to GEM. Furthermore, GPX3 significantly suppressed JNK/c-Jun signaling in PC, while anisomycin treatment reversed the inhibitory effects of GPX3 on the malignant behavior and chemo-resistance of PC cells. The results of the present study indicated that GPX3 could serve as a tumor suppressor in PC via inhibiting JNK/c-Jun signaling, thus providing novel insights into the treatment of PC.

β-defensin 118 attenuates inflammation and injury of intestinal epithelial cells upon enterotoxigenic Escherichia coli challenge

Background

Antimicrobial peptides including various defensins have been attracting considerable research interest worldwide, as they have potential to substitute for antibiotics. Moreover, AMPs also have immunomodulatory activity. In this study, we explored the role and its potential mechanisms of β-defensin 118 (DEFB118) in alleviating inflammation and injury of IPEC-J2 cells (porcine jejunum epithelial cell line) upon the enterotoxigenic Escherichia coli (ETEC) challenge.

Results

The porcine jejunum epithelial cell line (IPEC-J2) pretreated with or without DEFB118 (25 μg/mL) were challenged by ETEC (1×10⁶ CFU) or culture medium. We showed that DEFB118 pretreatment significantly increased the cell viability (P<0.05) and decreased the expressions of inflammatory cytokines such as the interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in IPEC-J2 cells exposure to ETEC (P<0.05). Interestingly, DEFB118 pretreatment significantly elevated the abundance of the major tight-junction protein zonula occludens-1 (ZO-1), but decreased the number of apoptotic cells upon ETEC challenge (P<0.05). The expression of caspase 3, caspase 8, and caspase 9 were downregulated by DEFB118 in the IPEC-J2 cells exposure to ETEC (P<0.05). Importantly, DEFB118 suppressed two critical inflammation-associated signaling proteins, nuclear factor-kappa-B inhibitor alpha (IκB-α) and nuclear factor-kappaB (NF-κB) in the ETEC-challenged IPEC-J2 cells.

Conclusions

DEFB118 can alleviate ETEC-induced inflammation in IPEC-J2 cells through inhibition of the NF-κB signaling pathway, resulting in reduced secretion of inflammatory cytokines and decreased cell apoptosis. Therefore, DEFB118 can act as a novel anti-inflammatory agent.

Mechanical Stress Signaling in Pancreatic Cancer Cells Triggers p38 MAPK- and JNK-Dependent Cytoskeleton Remodeling and Promotes Cell Migration via Rac1/cdc42/Myosin II

Advanced or metastatic pancreatic cancer is highly resistant to existing therapies, and new treatments are urgently needed to improve patient outcomes. Current studies focus on alternative treatment approaches that target the abnormal microenvironment of pancreatic tumors and the resulting elevated mechanical stress in the tumor interior. Nevertheless, the underlying mechanisms by which mechanical stress regulates pancreatic cancer metastatic potential remain elusive. Herein, we used a proteomic assay to profile mechanical stress-induced signaling cascades that drive the motility of pancreatic cancer cells. Proteomic analysis, together with selective protein inhibition and siRNA treatments, revealed that mechanical stress enhances cell migration through activation of the p38 MAPK/HSP27 and JNK/c-Jun signaling axes, and activation of the actin cytoskeleton remodelers: Rac1, cdc42, and myosin II. In addition, mechanical stress upregulated transcription factors associated with epithelial-to-mesenchymal transition and stimulated the formation of stress fibers and filopodia. p38 MAPK and JNK inhibition resulted in lower cell proliferation and more effectively blocked cell migration under mechanical stress compared with control conditions. The enhanced tumor cell motility under mechanical stress was potently reduced by cdc42 and Rac1 silencing with no effects on proliferation. Our results highlight the importance of targeting aberrant signaling in cancer cells that have adapted to mechanical stress in the tumor microenvironment, as a novel approach to effectively limit pancreatic cancer cell migration.

IMPLICATIONS

Our findings highlight that mechanical stress activated the p38 MAPK and JNK signaling axis and stimulated pancreatic cancer cell migration via upregulation of the actin cytoskeleton remodelers cdc42 and Rac1.

Expression of activator protein-1 in papillary thyroid carcinoma and its clinical significance

Background

The abnormal expression of activator protein-1(AP-1) has recently been investigated in a variety of tumors. While the relationship between AP-1 and thyroid cancer is poorly studied, our study was to evaluate the protein expression and clinical value of AP-1 in papillary thyroid carcinoma (PTC).

Methods

The expression of AP-1 was examined by immunohistochemistry on paraffin-embedded tissues obtained from PTC and correspondent paracancerous tissues of 82 patients.

Results

Compared with paracancerous tissues, AP-1 expression was significantly elevated in PTC tissues and the positive rate was 79.3% (65/82). Our study found a linear trend relationship between the expression of AP-1 and tumor size. However, the differences in AP-1 expression among gender, age, lymph node metastasis, number of lesions, location of the lesion, and extrathyroid invasion are not statistically significant.

Conclusions

The expression of AP-1 plays an important role in the proliferation process of PTC.

Lily extracts inhibit the proliferation of gastric carcinoma SGC-7901 cells by affecting cell cycle progression and apoptosis via the upregulation of caspase-3 and Fas proteins, and the downregulation of FasL protein

The present study aimed to investigate the effect of alkaloids and carbinol extracts from lily on the proliferation of SGC-7901 cells, as well as the underlying mechanism. SGC-7901 cells were incubated with different concentrations of alkaloid or carbinol extracts for 24, 48 or 72 h. MTT assays were used to measure the inhibition rate of SGC-7901 cell proliferation. Inverted phase contrast and fluorescence microscopy was used to observe morphological changes of SGC-7901 cells. Flow cytometry was employed to detect cell cycle progression and apoptosis rates of SGC-7901 cells. Western blotting was performed to measure the expression of caspase-3, Fas and Fas ligand (FasL) proteins in SGC-7901 cells. The inhibition rate of SGC-7901 cell proliferation was significantly enhanced with increasing drug concentrations and time elapsed. Treatment with alkaloid or carbinol extracts deteriorated the morphology of SGC-7901 cells in a dose-dependent manner. Alkaloid and carbinol extracts arrested SGC-7901 cells in the G₂/M phase, and induced apoptosis in a dose-dependent manner. Alkaloid and carbinol extracts enhanced caspase-3, and Fas expression, but reduced FasL expression in SGC-7901 cells. The present study demonstrated that alkaloids and carbinol extracts from lily inhibited the proliferation of gastric carcinoma SGC-7901 cells by arresting cells in the G₂/M phase. The upregulation of caspase-3 and Fas proteins, and the downregulation of FasL protein may be an important mechanism for the induction of SGC-7901 cell apoptosis.

Ursolic acid nanoparticles inhibit cervical cancer growth in vitro and in vivo via apoptosis induction

Cervical cancer is a cause of cancer death, making it one of the most common causes of death among women globally. Previously, a variety of studies have revealed the molecular mechanisms by which cervical cancer develops. However, there are still limitations in treatment for cervical cancer. Ursolic acid is a naturally derived pentacyclic triterpene acid, exhibiting broad anticancer effects. Nanoparticulate drug delivery systems have been known to better the bioavailability of drugs on intranasal administration compared with only drug solutions. Administration of ursolic acid nanoparticles is thought to be sufficient to lead to considerable suppression of cervical cancer progression. We loaded gold-ursolic acid into poly(DL-lactide-co-glycolide) nanoparticles to cervical cancer cell lines due to the properties of ursolic acid in altering cellular processes and the easier absorbance of nanoparticles. In addition, in this study, ursolic acid nanoparticles were administered to cervical cancer cells to find effective treatments for cervical cancer inhibition. In the present study, ELISA, western blotting, flow cytometry and immunohistochemistry assays were carried out to calculate the molecular mechanism by which ursolic acid nanoparticles modulated cervical cancer progression. Data indicated that ursolic acid nanoparticles, indeed, significantly suppress cervial cancer cell proliferation, invasion and migration compared to the control group, and apoptosis was induced by ursolic acid nanoparticles in cervical cancer cells through activating caspases, p53 and suppressing anti-apoptosis-related signals. Furthermore, tumor size was reduced by treatment of ursolic acid nanoparticles in in vivo experiments. In conclusion, this study suggests that ursolic acid nanoparticles inhibited cervical cancer cell proliferation via apoptosis induction, which could be a potential target for future therapeutic strategy clinically.

JunD Is Required for Proliferation of Prostate Cancer Cells and Plays a Role in Transforming Growth Factor-β (TGF-β)-induced Inhibition of Cell Proliferation

TGF-β inhibits proliferation of prostate epithelial cells. However, prostate cancer cells in advanced stages become resistant to inhibitory effects of TGF-β. The intracellular signaling mechanisms involved in differential effects of TGF-β during different stages are largely unknown. Using cell line models, we have shown that TGF-β inhibits proliferation in normal (RWPE-1) and prostate cancer (DU145) cells but does not have any effect on proliferation of prostate cancer (PC3) cells. We have investigated the role of Jun family proteins (c-Jun, JunB, and JunD) in TGF-β effects on cell proliferation. Jun family members were expressed at different levels and responded differentially to TGF-β treatment. TGF-β effects on JunD protein levels, but not mRNA levels, correlated with its effects on cell proliferation. TGF-β induced significant reduction in JunD protein in RWPE-1 and DU145 cells but not in PC3 cells. Selective knockdown of JunD expression using siRNA in DU145 and PC3 cells resulted in significant reduction in cell proliferation, and forced overexpression of JunD increased the proliferation rate. On the other hand, knockdown of c-Jun or JunB had little, if any, effect on cell proliferation; overexpression of c-Jun and JunB decreased the proliferation rate in DU145 cells. Further studies showed that down-regulation of JunD in response to TGF-β treatment is mediated via the proteasomal degradation pathway. In conclusion, we show that specific Jun family members exert differential effects on proliferation in prostate cancer cells in response to TGF-β, and inhibition of cell proliferation by TGF-β requires degradation of JunD protein.

Reduced expression of caspase-8 and cleaved caspase-3 in pancreatic ductal adenocarcinoma cells

Pancreatic ductal adenocarcinoma (PDAC) is a rare neoplasm that affects the gastrointestinal system, and is characterized by a high mortality rate. It has been demonstrated that apoptosis has a significant role in the regulation of cancer cells. Therefore, the aim of the present study was to immunohistochemically assess the expression of proteins belonging to the caspase family, namely caspase-8, pro-caspase-3 and cleaved (active) caspase-3 in pancreatic cancer. The study group consisted of 29 patients exhibiting PDAC. Protein expression was evaluated by immunohistochemical methods. The expression of caspase-8 in normal cells was negative in 17.2% of cases and positive in 82.8% of cases. All cases demonstrated pro-caspase-3 expression in normal pancreatic cells, compared with 93.1% of cancer cells. Staining for activated caspase-3 was positive in 27 normal tissue cases, compared with positivity in only 10 cancer cases. Caspase-8 expression positively correlated with cleaved caspase-3 expression in the cytoplasm of cancer cells (P<0.002). Caspase-3 expression was identified to correlate with inflammatory peritumoral infiltration (P<0.015). No correlation was observed between caspase expression and any other clinicopathological parameters. The results of the present study demonstrated aberrant initiation of cancer cell apoptosis in PDAC via a decrease in caspase-8 expression, which may lead to disorders in the activation of effector caspase-3.

Apoptosis in glioma-bearing rats after neural stem cell transplantation

Abnormal activation of the Ras/Raf/Mek/Erk signaling cascade plays an important role in glioma. Inhibition of this aberrant activity could effectively hinder glioma cell proliferation and promote cell apoptosis. To investigate the mechanism of glioblastoma treatment by neural stem cell transplantation with respect to the Ras/Raf/Mek/Erk pathway, C6 glioma cells were prepared in suspension and then infused into the rat brain to establish a glioblastoma model. Neural stem cells isolated from fetal rats were then injected into the brain of this glioblastoma model. Results showed that Raf-1, Erk and Bcl-2 protein expression significantly increased, while Caspase-3 protein expression decreased. After transplantation of neural stem cells, Raf-1, Erk and Bcl-2 protein expression significantly decreased, while Caspase-3 protein expression significantly increased. Our findings indicate that transplantation of neural stem cells may promote apoptosis of glioma cells by inhibiting Ras/Raf/Mek/Erk signaling, and thus may represent a novel treatment approach for glioblastoma.

Hepatoprotective effects of lychee (Litchi chinensis Sonn.): a combination of antioxidant and anti-apoptotic activities

AIM OF THE STUDY

Gimjeng and Chakapat lychee (Litchi chinensis Sonn.) were evaluated for hepatoprotective activity on CCl(4)-induced hepatotoxicity in rats.

MATERIALS AND METHODS

Fruit pulp extracts of the lychees were examined for vitamin C, phenolic contents, anti-lipid peroxidation activity and hepatoprotective effect. Male Wistar albino rats were intraperitoneally injected (ip) with CCl(4) (2 ml/kg), then were orally administered (po) with silymarin (100mg/kg), and Gimjeng or Chakapat extracts (100 and 500 mg/kg). After ten days, the rats were sacrificed and their livers were examined histopathologically and immunohistochemically. Their serum glutamate-pyruvate transaminase, glutamate-oxalate transaminase, and alkaline phosphatase activities were analyzed. Apoptotic activity of the livers was assessed quantitatively.

RESULTS

The Gimjeng and Chakapat extracts showed the contents of vitamin C (1.2±0.6 and 4.3±0.1mg/100g) and phenolics like trans-cinnamic acid and pelargonidin-3-O-glucoside (9.80±0.21 and 19.56±0.4 mg GAE/g extract, respectively), and trolox equivalent antioxidant capacity (TEAC) values (11.64 and 9.09 g/mg trolox), respectively. The Gimjeng as compared to the Chakapat demonstrated a better antioxidant activity as revealed by anti-lipid peroxidation activity with the TEAC values. Administration of CCl(4) in rats elevated the serum GPT, GOT, and ALP level whereas silymarin, Gimjeng and Chakapat extracts prevented these increases significantly. Significant decrease of apoptotic cells together with restoration of morphological changes confirmed the hepatoprotective effect in the CCl(4)-induced rats pretreated with the extracts.

CONCLUSION

Antioxidant properties of the Gimjeng and Chakapat lychees as evidenced by the vitamin C and phenolic compounds, anti-lipid peroxidation and anti-apoptosis could explain the hepatoprotective effects in CCl(4)-induced hepatotoxicity.

Screening the pathogenic genes and pathways related to DMBA (7,12-dimethylbenz[a]anthracene)-induced transformation of hamster oral mucosa from precancerous lesions to squamous cell carcinoma

This study aimed to screen the pathogenic genes and pathways that relate to the transformation of hamster buccal mucosa from precancerous lesions to squamous cell carcinoma by whole genome microarray and bioinformatics analysis. A DMBA (7,12-dimethylbenz[a]anthracene)-induced hamster model of a precancerous lesion and squamous cell carcinoma was established. The differentially expressed genes were detected using an Agilent whole rat genome microarray, which contains 41,000 genes/ESTs. Gene ontology (GO) functional classification and pathway analyses were performed, and a subset of differentially expressed genes were validated using RT-PCR. The results showed that during the transformation of hamster buccal mucosa from the precancerous lesion to squamous cell carcinoma, a total of 1,981 genes were differentially expressed, of which 1,037 were up-regulated and 944 were down-regulated. GO analysis revealed that the differentially expressed genes are mainly involved in 14 functional groups including those of metabolism and cell structure. Additionally, 9 significantly altered pathways were identified. Among the 1,861 known differentially expressed genes, 14 genes including Casp3, CCL5 and CXCL12 were enriched in the 9 altered pathways. The up-regulation of SPARC and down-regulation of Casp3 were confirmed by RT-PCR. In conclusion, a total of 1,981 differentially expressed genes and 9 significantly altered pathways were identified in the transformation of hamster buccal mucosa from precancerous lesions to squamous cell carcinoma. A total of 14 pathway-enriched genes including Casp3, CCL5 and CXCL12 may play critical roles in the alteration of cellular pathways leading to the transformation of buccal mucosa from precancerous lesions to squamous cell carcinoma. Future studies focusing on these genes and pathways are required in order to gain a better understanding and provide effective prevention and treatment of oral squamous cell carcinoma.

EGCG enhances TRAIL-mediated apoptosis in human melanoma A375 cell line

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anti-cancer agent. Epigallocatechin-3-gallate (EGCG) is a polyphenolic constituent of green tea. In this study, inhibitory effect of combined use of EGCG and TRAIL on human melanoma A375 cells was examined and the possible mechanism investigated. The cells were divided into 4 groups: control group, EGCG group (EGCG: 10, 20 mug/mL), TRAIL group (TRAIL: 25 ng/mL) and EGCG+TRAIL group (combined group). The growth inhibition was measured in the A375 cells treated with different concentrations of TRAIL ((25, 50, 75, 100, 125, 150 ng/mL) by MTT assay. The apoptosis was assessed by flow cytometry. The expressions of DR4 and DR5 were detected by flow cytometry and western blotting. The activities of caspase-8 and caspase-3 were determined by colorimetric assay. The results showed that TRAIL could dose-dependently inhibit the growth of A375 cells and the IC(50) of TRAIL was 150 ng/mL. The apoptosis rate was 11.8% in the TRAIL group, 5%-7% in the EGCG group and 48.9%-59.1% in the combined group. Significant difference was found in the apoptosis rate between the combined group and the EGCG or TRAIL group (P<0.05 for each). The expression of DR4 instead of DR5 was significantly increased in the EGCG group. The activity of caspase-3 rather than caspase-8 was substantially enhanced in the EGCG group. These results suggest that EGCG is useful for the TRAIL-based treatment for melanoma.

Effect of gemcitabine on the expression of apoptosis-related genes in human pancreatic cancer cells

AIM: To investigate the expression of genes involved in the gemcitabine-induced cytotoxicity in human pancreatic cancer cells.

METHODS: A human pancreatic cancer cell line, PANC-1, was cultured. 1 x 10⁴ PANC-1 cells were plated in 96-well microtiter plates. After being incubated for 24 h, gemcitabine was added to the medium at concentrations ranging 2.5 -1 000 mg/L. The AlamarBlue dye method was used for cell growth analysis. DNA fragmentation was quantitatively assayed using a DNA fragmentation enzyme-linked immunosorbent assay (ELISA) kit. PAP and TP53INP1 mRNA expression was determined using the reverse transcription-polymerase chain reaction with semi-quantitative analysis. The expression of GSK-3β and phospho-GSK-3β proteins was examined with Western blot analysis.

RESULTS: The IC₅₀ for the drug after a 48-h exposure to gemcitabine was 16 mg/L. The growth of PANC-1 cells was inhibited by gemcitabine in a concentration-dependent manner (P < 0.0001) and the cell growth was also inhibited throughout the time course (P < 0.0001). The DNA fragmentation rate in the gemcitabine-treated group at 48 h was 44.7 %, whereas it was 25.3 % in the untreated group. The PAP mRNA expression was decreased after being treated with gemcitabine, whereas the TP53INP1 mRNA was increased by the gemcitabine treatment. Western blot analysis showed that phospho- GSK-3β^ser9 was induced by the gemcitabine treatment.

CONCLUSION: Gemcitabine suppresses PANC-1 cell proliferation and induces apoptosis. Apoptosis is considered to be associated with the inhibition of PAP and GSK-3β, and the activation of TP53INP1 and pospho-GSK-3β^ser9.

Expression of c-jun oncogene in hyperplastic and carcinomatous human prostate

OBJECTIVES

To investigate c-jun oncoprotein (JUN) expression in diseases of the human prostate gland at the tissue level and to determine its relationship to clinicopathologic variables.

METHODS

The expression of JUN was studied using immunohistochemistry in archival tissue from benign prostatic hyperplasia (BPH) (n = 16) and prostate adenocarcinoma (PCa) (n = 36) specimens.

RESULTS

JUN-specific positive nuclear immunostaining was observed in 13 (81.25%) of 16 BPH and 31 (86.1%) of 36 PCa specimens. JUN-specific immunostaining was significantly stronger in the PCa than in the BPH tissue (P = 0.006). In the PCa tissue, no significant correlation was found between JUN immunohistochemical expression and tumor histologic grade (Gleason score) or serum prostate-specific antigen level.

CONCLUSIONS

JUN expression may play a role in normal cell function of the prostatic epithelium and is expressed in most BPH and PCa samples. The finding that JUN-specific immunostaining intensity was stronger in the vast majority of PCa than in the BPH samples implies that the role of c-jun may be enhanced during malignant transformation.

Oncogenes as novel targets for cancer therapy (part III): transcription factors

This is the third paper in a four-part serial review on potential therapeutic targeting of oncogenes. The previous parts described the involvement of oncogenes in different aspects of cancer growth and development, and considered the new technologies responsible for the advancement of oncogene identification, target validation, and drug design. Because of such advances, new specific and more efficient therapeutic agents can be developed for cancer. This part of the review continues the exploration of various oncogenes that we have grouped within seven categories: growth factors, tyrosine kinases, intermediate signaling molecules, transcription factors, cell cycle regulators, DNA damage repair genes, and genes involved in apoptosis. Part one discussed growth factors and tyrosine kinases and part two discussed intermediate signaling molecules. This portion of the review covers transcription factors and the various strategies being used to inhibit their expression or decrease their activities.

c-Jun phosphorylation by the human vaccinia-related kinase 1 (VRK1) and its cooperation with the N-terminal kinase of c-Jun (JNK)

The VRK1 kinase is a novel Ser-Thr kinase in the human kinome that diverged from the casein kinase 1 branch. These kinases phosphorylate transcription factors related to stress responses, such as p53. In this report we have studied the phosphorylation of the transcription factor c-Jun in its N-terminal region. The VRK1 protein phosphorylates c-Jun with a Km of 0.4 muM, and is not inhibited by SP600125. VRK1 phosphorylates c-Jun in Ser63 and Ser73 in vitro, the same residues targeted by the N-terminal kinase of c-Jun (JNK). This phosphorylation induces the stabilization and accumulation of the c-Jun protein. VRK1 phosphorylates the endogenous c-Jun in Ser63. VRK1 activates c-Jun dependent transcription, which is dependent on phosphorylation of Ser63 and Ser73. The c-Jun with Ser63Ala and Ser73Ala substitutions is not transcriptionally active when cotransfected with VRK1. VRK1 interacts with c-Jun but not with JNK. The cotransfection of VRK1 and JNK has an additive effect on the transcriptional activation of c-Jun indicating that they can cooperate when both are at suboptimal dose; otherwise, maximum effect by one of them prevents the effect of the other. The VRK1-c-Jun connection represents a component of a new signaling pathway whose upstream elements remain to be identified.

Caspase-3 drives apoptosis in pancreatic cancer cells after treatment with gemcitabine

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.

An increased high-mobility group A2 expression level is associated with malignant phenotype in pancreatic exocrine tissue

The altered form of the high-mobility group A2 (HMGA2) gene is somehow related to the generation of human benign and malignant tumours of mesenchymal origin. However, only a few data on the expression of HMGA2 in malignant tumour originating from epithelial tissue are available. In this study, we examined the HMGA2 expression level in pancreatic carcinoma, and investigated whether alterations in the HMGA2 expression level are associated with a malignant phenotype in pancreatic tissue. High-mobility group A2 mRNA and protein expression was determined in eight surgically resected specimens of non-neoplastic tissue (six specimens of normal pancreatic tissue and two of chronic pancreatitis tissue) and 27 pancreatic carcinomas by highly sensitive reverse transcriptase–polymerase chain reaction (RT–PCR) techniques and immunohistochemical staining, respectively. Reverse transcriptase–polymerase chain reaction analysis revealed the expression of the HMGA2 gene in non-neoplastic pancreatic tissue, although its expression level was significantly lower than that in carcinoma. Immunohistochemical analysis indicated that the presence of the HMGA2 gene in non-neoplastic pancreatic tissue observed in RT–PCR reflects its abundant expression in islet cells, together with its focal expression in duct epithelial cells. Intense and multifocal or diffuse HMGA2 immunoreactivity was noted in all the pancreatic carcinoma examined. A strong correlation between HMGA2 overexpression and the diagnosis of carcinoma was statistically verified. Based on these findings, we propose that an increased expression level of the HMGA2 protein is closely associated with the malignant phenotype in the pancreatic exocrine system, and accordingly, HMGA2 could serve as a potential diagnostic molecular marker for distinguishing pancreatic malignant cells from non-neoplastic pancreatic exocrine cells.