Effects of STI571 (gleevec) on pancreatic cancer cell growth

Anticancer Activity of Sunitinib Analogues in Human Pancreatic Cancer Cell Cultures under Normoxia and Hypoxia

Pancreatic cancer remains one of the deadliest cancer types. It is usually characterized by high resistance to chemotherapy. However, cancer-targeted drugs, such as sunitinib, recently have shown beneficial effects in pancreatic in vitro and in vivo models. Therefore, we chose to study a series of sunitinib derivatives developed by us, that were proven to be promising compounds for cancer treatment. The aim of our research was to evaluate the anticancer activity of sunitinib derivatives in human pancreatic cancer cell lines MIA PaCa-2 and PANC-1 under normoxia and hypoxia. The effect on cell viability was determined by the MTT assay. The compound effect on cell colony formation and growth was established by clonogenic assay and the activity on cell migration was estimated using a ‘wound healing’ assay. Six out of 17 tested compounds at 1 µM after 72 h of incubation reduced cell viability by 90% and were more active than sunitinib. Compounds for more detailed experiments were chosen based on their activity and selectivity towards cancer cells compared to fibroblasts. The most promising compound EMAC4001 was 24 and 35 times more active than sunitinib against MIA PaCa-2 cells, and 36 to 47 times more active against the PANC-1 cell line in normoxia and hypoxia. It also inhibited MIA PaCa-2 and PANC-1 cell colony formation. Four tested compounds inhibited MIA PaCa-2 and PANC-1 cell migration under hypoxia, but none was more active than sunitinib. In conclusion, sunitinib derivatives possess anticancer activity in human pancreatic adenocarcinoma MIA PaCa-2 and PANC-1 cell lines, and they are promising for further research.

The effect of danusertib, an Aurora kinase inhibitor, onto the cytotoxicity, cell cycle and apoptosis in pancreatic ductal adenocarcinoma cells

Background

Pancreatic cancer is the second type of cancer that causes the most death among the digestive system cancers. Difficulties in early diagnosis and rapidly progressing to advanced stages are most common in high mortality rate of pancreatic carcinoma. The mutation of Bcr-Abl tyrosine kinase and mitotic kinases (such as Aurora kinases), which are involved in the cell cycle, plays an important role in the progression of cancer. Enzymes belonging to Aurora kinase family (-A, -B, -C) have been reported to play a major role in cancer progression, invasion and metastasis. Therefore, the purpose of this study, investigate of the effect of danusertib, an Aurora kinase inhibitor, onto cytotoxicity, apoptosis and cell cycle in human pancreatic carcinoma CFPAC-1 cells.

Materials and Methods

For determining the IC50 value, the 20,000 cells were seeded in E-plate 16 wells in a real-time cell analyzer and various concentrations of danusertib (1-10,000 nM) were applied onto CFPAC-1 cells incubated in IMDM medium. Cell index demonstrated that the proliferation of fraction cells was measured in real time. On the other hand, cell apoptosis and cell cycle arrest test were stained with Annexin V-APC/PI and DNA-cell cycle PI staining respectively by using flow cytometry.

Results

The IC₅₀ value was found to be approximately 400 nM. Danusertib at this concentration induced apoptosis in CFPAC-1 cells (%14,8 at 24 hours; %21,3 at 48 hours). Furthermore, in the cells treated with danusertib, 31.77% and 11.05% were arrested in the S and G2 phases, respectively.

Conclusions

Aurora kinase inhibitor danusertib induced a significant effect of cytotoxic, apoptotic and cell cycle arrest in CFPAC-1 ductal adenocarcinoma cells. Therefore, it may be a potential alternative to the treatment of pancreatic cancers.

Imatinib‑induced apoptosis of gastric cancer cells is mediated by endoplasmic reticulum stress

Imatinib is a powerful tyrosine kinase inhibitor that specifically targets BCR-ABL, c-KIT, and PDGFR kinases, and is used in the treatment of chronic myelogenous leukemia, gastrointestinal stromal tumors, and other types of cancers. However, the possible anticancer effects of imatinib in gastric cancer have not yet been explored. The present study evaluated the in vitro effects of imatinib on gastric cancer cells and determined the molecular mechanism underlying these effects. We determined that imatinib induced mitochondria-mediated apoptosis of gastric cancer cells by involving endoplasmic reticulum (ER) stress-associated activation of c-Jun NH₂-terminal kinase (JNK). We also found that imatinib suppressed cell proliferation in a time- and dose-dependent manner. Cell cycle analysis revealed that imatinib-treated AGS cells were arrested in the G2/M phase of the cell cycle. Moreover, imatinib-treated cells exhibited increased levels of phosphorylated JNK, and of the transcription factor C/EBP homologous protein, an ER stress-associated apoptotic molecule. Results of cell viability assays revealed that treatment with a combination of imatinib and chemotherapy agents irinotecan or 5-Fu synergistically inhibited cell growth, compared with treatment with any of these drugs alone. These data indicated that imatinib exerted cytotoxic effects on gastric cancer cells by inducing apoptosis mediated by reactive oxygen species generation and ER stress-associated JNK activation. Furthermore, we revealed that imatinib induced the apoptosis of gastric cancer cells by inhibiting platelet-derived growth factor receptor signaling. Collectively, our results strongly support the use of imatinib in the treatment of treating gastric cancer.

Acyclic congeners from Actinoalloteichus cyanogriseus provide insights into cyclic bipyridine glycoside formation

Inactivation of the O-methyltransferase gene crmM of Actinoalloteichus cyanogriseus WH1-2216-6 led to a mutant that produced three new acyclic bipyridine glycosides, cyanogrisides E-G (1-3). Further chemical analysis of the wild strain yielded 1 and another new analogue, cyanogriside H (4). Compounds 1-4 possess a skeleton consisting of a 2,2'-bipyridine and a d-quinovose or l-rhamnose sugar moiety. Cyanogriside G (3) was considered to be a key biosynthetic intermediate of the cyclic bipyridine glycosides cyanogrisides A-D. Compounds 2 and 3 showed cytotoxicities against HCT116 and HL-60 cells, and compounds 1 and 4 were cytotoxic on K562 cells.

Indole diterpenoids and isocoumarin from the fungus, Aspergillus flavus, isolated from the prawn, Penaeus vannamei

Two new indole-diterpenoids (1 and 2) and a new isocoumarin (3), along with the known β-aflatrem (4), paspalinine (5), leporin B (6), α-cyclopiazonic acid (7), iso-α-cyclopiazonic acid (8), ditryptophenaline (9), aflatoxin B₁ (10), 7-O-acetylkojic acid (11) and kojic acid (12), were isolated from the fermentation broth of the marine-derived fungus, Aspergillus flavus OUCMDZ-2205. The structures of Compounds 1–12 were elucidated by spectroscopic analyses, quantum ECD calculations and the chemical method. New Compound 1 exhibited antibacterial activity against Staphylococcus aureus with a MIC value of 20.5 μM. Both new Compounds 1 and 2 could arrest the A549 cell cycle in the S phase at a concentration of 10 μM. Compound 1 showed PKC-beta inhibition with an IC₅₀ value of 15.6 μM. In addition, the absolute configurations of the known compounds, 4–6 and leporin A (6a), were also determined for the first time.

MicroRNA-100 regulates IGF1-receptor expression in metastatic pancreatic cancer cells

Patients with pancreatic adenocarcinoma have the lowest 5 year survival rate and yearly rates of incidence are nearly equal to the mortality rates. Long term cure rates by standard therapies are disappointing owing to disseminated disease at diagnosis and chemotherapeutic resistance. New therapeutic targets are necessary to decrease the progression of pancreatic cancer and the ability to identify targets specific to metastasis would improve patient care. We evaluated the levels of microRNA of metastatic and non-metastatic cell lines. The expression levels of microRNAs and mRNAs were determined using microarray analysis to examine and compare five pancreatic cancer cell lines, two that can metastasize in vivo (S2VP10 and S2CP9) and three that do not metastasize (MiaPaCa2, Panc-1 and ASPC-1). MicroRNA analysis indicated an increase in miR-100 and a decrease in miR-138 expression in metastatic cancer cells. Microarray analysis of different expressions of mRNAs in metastatic and non-metastatic pancreatic cell lines also indicated significantly increased insulin growth factor-1 receptor (IGF1-R) expression in metastatic pancreatic cancer cell lines compared to non-metastatic pancreatic cancer cell lines. To confirm microarray analysis results, western blot and immunocytochemistry were performed. Western blot revealed that IGF1-R expression exhibited in metastatic cancer cell lines a seven-fold increase compared to non-metastatic cell lines. In addition, downstream expressions of the proteins, GRB2 and phosphorylated PI3K, also were increased in aggressive cancer cell lines. Immunocytochemistry confirmed the linkage of IGF1-R to miR-100, because cells transfected with miR-100 inhibitor showed a decrease in IGF1-R. Cells transfected with a miR-138 mimic, however, did not affect IGF1-R expression.

A Multi-institutional Phase 2 Study of Imatinib Mesylate and Gemcitabine for First-Line Treatment of Advanced Pancreatic Cancer

BACKGROUND

The pancreatic tumor microenvironment is rich in receptors for platelet-derived growth factor (PDGFRs). Imatinib mesylate (IM) inhibits PDGFRs and decreases tumor interstitial fluid pressure, potentially improving drug access. These data and promising results in a phase 1 trial formed the rationale for a phase 2 trial combining IM and gemcitabine (GEM) in pancreatic cancer.

METHODS

Eligibility criteria included chemotherapy-naïve, locally advanced or metastatic pancreatic cancer; ECOG (Eastern Cooperative Oncology Group) performance status ≤2; and adequate end-organ function. The primary end point was progression-free survival (PFS). Secondary end points included response rate, toxicity, and overall survival (OS). GEM was given at 1200 mg/m(2)/120 min on days 3 and 10. IM (400 mg) was taken orally on days 1 to 5 and 8 to 12 of a 21-day cycle. Response was assessed every 3 cycles.

RESULTS

Forty-four patients from 7 centers were enrolled from October 2005 through July 2009. Median age was 62 years. The median number of cycles completed was 3 (range, 0-17). Common adverse effects included neutropenia, nausea, anemia, and fatigue. Half the patients required dose reductions. There were no complete responses to therapy. During treatment, 1 patient showed a partial response, 16 had stable disease, and 18 had progressive disease. The median PFS was 3.9 months (95% confidence interval, 2.1-5.1), the median OS was 6.3 months (95% confidence interval, 5.2-8.5), and the 1-year survival rate was 25.6% (95% confidence interval, 13.8-39.1).

CONCLUSION

IM in combination with GEM is tolerated in locally advanced, metastatic, or recurrent pancreatic cancer, but does not show a statistically significant PFS or OS benefit over chemotherapy with GEM alone.

Metabolic Profiling Comparison of Human Pancreatic Ductal Epithelial Cells and Three Pancreatic Cancer Cell Lines using NMR Based Metabonomics

Metabolic profiles of hydrophilic and lipophilic cell extracts from three cancer cell lines, Miapaca-2, Panc-1 and AsPC-1, and a non-cancerous pancreatic ductal epithelial cell line, H6C7, were examined by proton nuclear magnetic resonance spectroscopy. Over twenty five hydrophilic metabolites were identified by principal component and statistical significance analyses as distinguishing the four cell types. Fifteen metabolites were identified with significantly altered concentrations in all cancer cells, e.g. absence of phosphatidylgrycerol and phosphatidylcholine, and increased phosphatidylethanolamine and cholesterols. Altered concentrations of metabolites involved in glycerophospholipid metabolism, lipopolysaccharide and fatty acid biosynthesis indicated differences in cellular membrane composition between non-cancerous and cancer cells. In addition to cancer specific metabolites, several metabolite changes were unique to each cancer cell line. Increased N-acetyl groups in AsPC-1, octanoic acids in Panc-1, and UDP species in Miapaca-2 indicated differences in cellular membrane composition between the cancer cell lines. Induced glutamine metabolism and protein synthesis in cancer cells were indicated by absence of glutamine other metabolites such as acetate, lactate, serine, branched amino acids, and succinate. Knowledge of the specifically altered metabolic pathways identified in these pancreatic cancer cell lines may be useful for identifying new therapeutic targets and studying the effects of potential new therapeutic drugs.

A dose escalation study of gemcitabine plus oxaliplatin in combination with imatinib for gemcitabine-refractory advanced pancreatic adenocarcinoma

BACKGROUND

Targeting platelet-derived growth factor receptor-β (PDGFR-β) is a potential strategy to reduce tumour-related interstitial fluid pressure, enhance cytotoxic drug uptake and reduce chemoresistance. This study aimed to define safe doses of gemcitabine plus oxaliplatin when combined with imatinib (potent PDGFR-β inhibitor) in patients with advanced gemcitabine-refractory pancreatic cancer (PC).

PATIENTS AND METHODS

Using a 3 + 3 dose escalation design, patients of performance status zero or one were entered into five sequential dose levels (DLs) of gemcitabine [day 1, from 400 (DL1) to 1000 mg/m(2) (DL4)] and oxaliplatin [day 2, 85 (DL1-4) and 100 mg/m(2) (DL5)] two weekly. Imatinib 400 mg od was given for 7 days (day minus 2-5) each cycle.

RESULTS

Twenty-seven patients received 168 cycles in total. Median age was 61 years (44-74 years). Dose-limiting toxicities occurred in two of two patients at DL5 (G4 thrombocytopenia, G3 lethargy), defined as the maximum tolerated dose and one of six patients at DL4 (G3 lethargy). DL4 was expanded. There were 2 of 27 partial responses and 14 of 27 stable disease [disease control 52%, 95% confidence interval (CI) 32% to 71%]. Median progression-free survival and overall survival were 4.6 (95% CI 2.1-7.0) and 5.6 months (95% CI 2.5-8.7), respectively.

CONCLUSION

In gemcitabine-refractory PC, gemcitabine (1000 mg/m(2)) and oxaliplatin (85 mg/m(2)) can be safely combined with imatinib given on a 7 days on and 7 days off intermittent schedule.

Mutational profiling of kinases in human tumours of pancreatic origin identifies candidate cancer genes in ductal and ampulla of vater carcinomas

Background

Protein kinases are key regulators of cellular processes (such as proliferation, apoptosis and invasion) that are often deregulated in human cancers. Accordingly, kinase genes have been the first to be systematically analyzed in human tumors leading to the discovery that many oncogenes correspond to mutated kinases. In most cases the genetic alterations translate in constitutively active kinase proteins, which are amenable of therapeutic targeting. Tumours of the pancreas are aggressive neoplasms for which no effective therapeutic strategy is currently available.

Methodology/Principal Findings

We conducted a DNA-sequence analysis of a selected set of 35 kinase genes in a panel of 52 pancreatic exocrine neoplasms, including 36 pancreatic ductal adenocarcinoma, and 16 ampulla of Vater cancer. Among other changes we found somatic mutations in ATM, EGFR, EPHA3, EPHB2, and KIT, none of which was previously described in cancers.

Conclusions/Significance

Although the alterations identified require further experimental evaluation, the localization within defined protein domains indicates functional relevance for most of them. Some of the mutated genes, including the tyrosine kinases EPHA3 and EPHB2, are clearly amenable to pharmacological intervention and could represent novel therapeutic targets for these incurable cancers.

In vitro effects of imatinib mesylate on radiosensitivity and chemosensitivity of breast cancer cells

Background

Breast cancer treatment is based on a combination of adjuvant chemotherapy followed by radiotherapy effecting intracellular signal transduction. With the tyrosine kinase inhibitors new targeted drugs are available. Imatinib mesylate is a selective inhibitor of bcr-abl, PRGFR alpha, beta and c-kit. The purpose of this study was to determine whether Imatinib has an influence on the effectiveness of radiotherapy in breast cancer cell lines and if a combination of imatinib with standard chemotherapy could lead to increased cytoreduction.

Methods

Colony-forming tests of MCF 7 and MDA MB 231 were used to study differences in cell proliferation under incubation with imatinib and radiation. Changes in expression and phosphorylation of target receptors were detected using western blot. Cell proliferation, migration and apoptosis assays were performed combining imatinib with doxorubicin.

Results

The combination of imatinib and radiotherapy showed a significantly stronger inhibition of cell proliferation compared to single radiotherapy. Differences in PDGFR expression could not be detected, but receptor phosphorylation was significantly inhibited when treated with imatinib. Combination of imatinib with standard chemotherapy lead to an additive effect on cell growth inhibition compared to single treatment.

Conclusions

Imatinib treatment combined with radiotherapy leads in breast cancer cell lines to a significant benefit which might be influenced through inhibition of PDGFR phosphorylation. Combining imatinib with chemotherapy enhances cytoreductive effects. Further in vivo studies are needed to evaluate the benefit of Imatinib in combination with radiotherapy and chemotherapy on the treatment of breast cancer.

A review of kinases implicated in pancreatic cancer

The current 5-year survival rate of pancreatic cancer is about 3% and the median survival less than 6 months because the chemotherapy and radiation therapy presently available provide only marginal benefit. Clearly, pancreatic cancer requires new therapeutic concepts. Recently, the kinase inhibitors imatinib and gefitinib, developed to treat chronic myelogenous leukaemia and breast cancer, respectively, gave very good results. Kinases are deregulated in many diseases, including cancer. Given that phosphorylation controls cell survival signalling, strategies targeting kinases should obviously improve cancer treatment. The purpose of this review is to summarize the present knowledge on kinases potentially usable as therapeutic targets in the treatment of pancreatic cancer. All clinical trials using available kinase inhibitors in monotherapy or in combination with chemotherapeutic drugs failed to improve survival of patients with pancreatic cancer. To detect kinases relevant to this disease, we undertook a systematic screening of the human kinome to define a 'survival kinase' catalogue for pancreatic cells. We selected 56 kinases that are potential therapeutic targets in pancreatic cancer. Preclinical studies using combined inhibition of PAK7, MAP3K7 and CK2 survival kinases in vitro and in vivo showed a cumulative effect on apoptosis induction. We also observed that these three kinases are rather specific of pancreatic cancer cells. In conclusion, if kinase inhibitors presently available are unfortunately not efficient for treating pancreatic cancer, recent data suggest that inhibitors of other kinases, involved more specifically in pancreatic cancer development, might, in the future, become interesting therapeutic targets.

Radiosensitization effect of STI-571 on pancreatic cancer cells in vitro

PURPOSE

To examine STI-571-induced radiosensitivity in human pancreatic cancer cells in vitro.

METHODS AND MATERIALS

Three human pancreatic cancer cell lines (Bxpc-3, Capan-1, and MiaPaCa-2) exhibiting different expression levels of c-Kit and platelet-derived growth factor receptor beta (PDGFRbeta) and showing different K-ras mutation types were used. For evaluation of the antitumor activity of STI-571 in combination with radiation, clonogenic survival assays, Western blot analysis, and the annexin V/propidium iodide assay with microscopic evaluation by 4',6-diamidino-2-phenylindole were conducted.

RESULTS

Dramatic phosphorylated (p)-c-Kit and p-PDGFRbeta attenuation, a modest dose- and time-dependent growth inhibition, and significant radiosensitization were observed after STI-571 treatment in view of apoptosis, although the levels of growth inhibition and increased radiosensitization were different according to cell lines. The grades of radiosensitivity corresponded to the attenuation levels of p-c-Kit and p-PDGFRbeta by STI-571, particularly to those of p-c-Kit, and the radiosensitivity was partially affected by K-ras mutation in pancreatic cancer cells. Among downstream pathways associated with c-Kit or PDGFRbeta, p-PLCgamma was more closely related to radiosensitivity compared with p-Akt1 or p-extracellular signal-regulated kinase 1.

CONCLUSION

STI-571 enhances radiation response in pancreatic cancer cells. This effect is affected by the attenuation levels of p-c-Kit or p-PDGFRbeta, and K-ras mutation status. Among them, p-c-Kit plays more important roles in the radiosensitivity in pancreatic cancer compared with p-PDGFRbeta or K-ras mutation status.

Changes in pERK1/2 and pAKT expression in melanoma lesions after imatinib treatment

Response to treatment with imatinib mesylate has been associated in preclinical models with the inhibition of two signaling pathways that promote cellular survival - the phosphatidylinositol 3-kinase/AKT pathway and the mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) pathway. We sought to evaluate the extent of inhibition of these two pathways in metastatic melanoma specimens from patients treated with imatinib. Metastatic melanoma tumor samples were obtained before and during the second week of imatinib treatment from patients enrolled in a phase II study. A tissue microarray was constructed using formalin-fixed, paraffin-embedded tissues, and immunohistochemical analysis was performed using standard techniques to detect phosphorylated (p) ERK1/2 and pAKT expression. Of 21 patients who were treated with imatinib, tumor samples adequate for analysis were available both at baseline and during the second week of treatment from 10 patients for pERK1/2 expression and from nine patients for pAKT expression. No consistent pattern of change in pAKT or pERK expression after treatment with imatinib was observed. No apparent correlation between the clinical benefit of imatinib treatment and changes in pAKT and pERK1/2 expression was observed. A better understanding of the AKT and mitogen-activated protein kinase pathways is needed to optimize the clinical benefit of targeted therapy, such as imatinib.

New treatment options for advanced pancreatic cancer

Pancreatic cancer has a very high mortality rate and affects approximately 230,000 individuals worldwide. Gemcitabine has become established as the standard therapy for advanced pancreatic cancer; however, the survival advantage is small. Adjuvant chemotherapy using either 5-fluorouracil or gemcitabine is now established in pancreatic cancer as an alternative therapy. Combinations of gemcitabine with either platin agents or capecitabine may be advantageous. Anti-EGFR and anti-VEGF agents have been unsuccessful but multiple tyrosine kinase inhibitors are under investigation. Of the increasing number of immunological agents, the GV1001 antitelomerase vaccine holds some interest. Targeted agents against important mitogenic pathways, including MEK/ERK, Src, PI3K/Akt, mTOR, Hedgehog and NF-kappaB, as well as agents targeting histone deacetylase, poly(ADP-ribose) polymerase, heat shock protein 90 and other agents such as beta-lapachone, hold considerable interest for further development. However, the probability of individual success is low.

Imatinib mesylate inhibits proliferation and exerts an antifibrotic effect in human breast stroma fibroblasts

Tumor stroma plays an important role in cancer development. In a variety of tumors, such as breast carcinomas, a desmoplastic response, characterized by stromal fibroblast and collagen accumulation, is observed having synergistic effects on tumor progression. However, the effect of known anticancer drugs on stromal cells has not been thoroughly investigated. Imatinib mesylate is a selective inhibitor of several protein tyrosine kinases, including the receptor of platelet-derived growth factor, an important mediator of desmoplasia. Recently, we have shown that imatinib inhibits the growth and invasiveness of human epithelial breast cancer cells. Here, we studied the effect of imatinib on the proliferation and collagen accumulation in breast stromal fibroblasts. We have shown that it blocks the activation of the extracellular signal-regulated kinase and Akt signaling pathways and up-regulates cyclin-dependent kinase inhibitor p21(WAF1), leading to the inhibition of fibroblast proliferation, by arresting them at the G(0)/G(1) phase of the cell cycle. Imatinib inhibits more potently the platelet-derived growth factor-mediated stimulation of breast fibroblast proliferation. By using specific inhibitors, we have found that this is due to the inhibition of the Akt pathway. In addition, imatinib inhibits fibroblast-mediated collagen accumulation. Conventional and quantitative PCR analysis, as well as gelatin zymography, indicates that this is due to the down-regulation of mRNA synthesis of collagen I and collagen III-the main collagen types in breast stroma-and not to the up-regulation or activation of collagenases matrix metalloproteinase 2 and matrix metalloproteinase 9. These data indicate that imatinib has an antifibrotic effect on human breast stromal fibroblasts that may inhibit desmoplastic reaction and thus tumor progression.

A phase II trial of imatinib mesylate in patients with metastatic pancreatic cancer

OBJECTIVES

The aim of the study was to assess the clinical efficacy and toxicity of single-agent imatinib mesylate in patients with advanced, unresectable metastatic pancreatic cancer.

METHODS

Previously treated or untreated patients with histologically proven, unresectable pancreatic adenocarcinoma with adequate organ and bone marrow function were enrolled. Patients received imatinib 400 mg orally twice a day for a 28-day cycle. Response was evaluated every 4 weeks by imaging scans. Response was defined as lack of tumor progression at 3 months.

RESULTS

Eleven patients were enrolled, and 9 were evaluable for response. Best response was stable disease in 3 patients after 2 cycles of therapy. All of them subsequently progressed. No patients remained on treatment for 3 months or longer, which was the response end point. Median time to tumor progression was 47 days (range, 19-76 days) and median overall survival was 118 days (range, 40-221 days). The first 3 patients received imatinib 400 mg orally twice a day. Due to unexpected grades 2 and 3 toxicities, the dose was reduced to 600 mg daily which was well tolerated. Most common adverse events included grades 1 to 2 edema, liver enzyme elevations, nausea, and rash.

CONCLUSION

Single-agent imatinib does not have a significant activity in pancreatic cancer.

MEK inhibitor enhances the inhibitory effect of imatinib on pancreatic cancer cell growth

Imatinib mesylate (imatinib) inhibits the c-Kit-dependent tyrosine kinase activities and highly effective in the treatment of CML and GIST patients. Although pancreatic cancer is reported to express c-Kit, imatinib does not effectively inhibit pancreatic cancer cell growth at physiological concentrations. Therefore, we investigated the mechanism of resistance of pancreatic cancer to imatinib treatment. Imatinib inhibited growth of pancreatic cancer cell lines in concentration and time-dependent fashion regardless of c-Kit expression. However, 5 microM imatinib, which is almost a mean maximal plasma concentration in clinical setting, failed to suppress pancreatic cancer cell growth. Western blot analysis demonstrated that 5 microM imatinib treatment for 1h activated the MEK-MAPK pathway and the activation was independent of Ras activation. Administration of 5 microM imatinib and 1 microM U0126 (MEK inhibitor) significantly suppressed pancreatic cell growth. Our results indicate that a combination therapy of imatinib and MEK inhibitor can be a new therapeutic strategy to suppress the progression of pancreatic cancer.

Over-expression and siRNA of a novel environmental lipopolysaccharide-responding gene on the cell cycle of the human hepatoma-derived cell line HepG2

Lipopolysaccharide (LPS) is the toxic determinant for Gram-negative bacterium infection. The individual response to LPS was related to its gene background. It is necessary to identify new molecules and signaling transduction pathways about LPS. The present study was undertaken to evaluate the effects of a novel environmental lipopolysaccharide-responding (Elrg) gene on the regulation of proliferation and cell cycle of the hepatoma-derived cell line, HepG2. By means of RT-PCR, the new molecule of Elrg was generated from a human dental pulp cell cDNA library. Expression level of Elrg in HepG2 cells was remarkably upgraded by the irritation of LPS. Localization of Elrg in HepG2 cells was positioned mainly in cytoplasm. HepG2 cells were markedly arrested in the G1 phase by over-expressing Elrg. The percentage of HepG2 cells in G1 phase partly decreased after Elrg-siRNA. In conclusion, Elrg is probably correlative with LPS responding. Elrg is probably a new protein in cytoplasm which plays an important role in regulating cell cycle. The results will deepen our understanding about the potential effects of Elrg on the human hepatoma-derived cell line HepG2.

Regulation and functional role of the Runt-related transcription factor-2 in pancreatic cancer

Recent evidence suggests that Runt-related transcription factors play a role in different human tumours. In the present study, the localisation of the Runt-related transcription factor-2 (Runx2), its transcriptional activity, as well as its regulation of expression was analysed in human pancreatic ductal adenocarcinoma (PDAC). Quantitative real-time PCR and immunohistochemistry were used for Runx2 expression and localisation analysis. Runt-related transcription factor-2 expression was silenced using specific siRNA oligonucleotides in pancreatic cancer cells (Panc-1) and immortalised pancreatic stellate cells (IPSCs). Overexpression of Runx2 was achieved using a full-length expression vector. TGF-β1, BMP2, and other cytokines were assessed for their potential to regulate Runx2 expression. There was a 6.1-fold increase in median Runx2 mRNA levels in PDAC tissues compared to normal pancreatic tissues (P<0.0001). Runt-related transcription factor-2 was localised in pancreatic cancer cells, tubular complexes, and PanIN lesions of PDAC tissues as well as in tumour-associated fibroblasts/stellate cells. Coculture of IPSCs and Panc-1 cells, as well as treatment with TGF-β1 and BMP2, led to increased Runx2 expression in Panc-1 cells. Runt-related transcription factor-2 overexpression was associated with decreased MMP1 release as well as decreased growth and invasion of Panc-1 cells. These effects were reversed by Runx2 silencing. In conclusion, Runx2 is overexpressed in PDAC, where it is regulated by certain cytokines such as TGF-β1 and BMP2 in an auto- and paracrine manner. In addition, Runx2 has the potential to regulate the transcription of extracellular matrix modulators such as SPARC and MMP1, thereby influencing the tumour microenvironment.

Pancreatic cancer microenvironment

Pancreatic ductal adenocarcinoma remains an extremely aggressive malignancy that is virtually therapy-resistant and has therefore one of the worst prognoses of all human cancers. The focus of research, which had been placed mostly on genetic and epigenetic alterations of the cancer cells themselves, has shifted gradually towards the microenvironment. The cancer microenvironment consists of various components, including fibroblasts, endothelial cells, immune cells, and endocrine cells, that interact with each other and the cancer cells in a complex fashion. This interplay has implications for pancreatic cancer cell growth, migration and invasion, angiogenesis, and immunological recognition of cancer cells. Evidence is accumulating that the cancer microenvironment plays an active role in disease progression, and efforts are being made to target this interplay between cancer cells and host cells to improve the outcome of this deadly disease.

Stem cell factor/c-kit receptor signaling enhances the proliferation and invasion of colorectal cancer cells through the PI3K/Akt pathway

In this study, we examined the role of c-kit receptor (KIT) signal transduction on the proliferation and invasion of colorectal cancer cells. We found that c-kit was expressed in 2 colorectal cancer cell lines as determined by RT-PCR, Western blot, and flow cytometry. In KIT-positive lines, KIT was activated by stem cell factor (SCF). SCF enhanced cellular proliferation of positive lines as demonstrated by the WST-1 proliferation assay. Furthermore, SCF enhanced the invasive ability of KIT-positive cell lines. SCF stimulation upregulated p44/42 mitogen-activated protein kinase (MAPK) and Akt as shown by Western blot. We examined the roles played by p44/42 MAPK and phosphatidylinositol 3-kinase (PI3K)/Akt pathways in proliferation and invasion. PI3K/Akt activity strongly correlated with proliferation and invasion and p44/42 MAPK was correlated with only invasion. In conclusion, the SCF-enhanced proliferation and invasion of KIT-positive colorectal cancer cells is achieved mainly through the PI3K/Akt pathway.

Emerging role of platelet-derived growth factor receptor-beta inhibition in radioimmunotherapy of experimental pancreatic cancer

PURPOSE

Thus far, the therapy of pancreatic cancer remains an insurmountable challenge. Not a solitary therapeutic modality in the battery of available therapeutic options is capable to cure or, at the very least, stop the progression of this disease in any meaningful way. The purpose of reported here studies was to implement a multimodality approach to radioimmunotherapy of pancreatic cancer and, ultimately, to develop a course of therapy with the clinical value.

EXPERIMENTAL DESIGN

Animal model was NCr-nu/nu mouse bearing s.c. xenografts of SW1990 pancreatic adenocarcinoma. Radioimmunotherapy based on (131)ICC49, a TAG-72-targeting monoclonal antibody, was augmented with imatinib, a potent inhibitor of platelet-derived growth factor receptor-beta. The postulated interactions between these two modalities depended on the imatinib-induced drop in the tumor interstitial fluid pressure and the subsequent increase of (131)ICC49 uptake into the tumor, resulting in improved tumor responses to radioimmunotherapy.

RESULTS

Biodistribution studies revealed a 50% improvement in the tumor uptake of (131)ICC49 in mice treated with imatinib. Tumor development was practically arrested for approximately 3 weeks in response to the treatment composed of (131)ICC49 and imatinib with tumor quadrupling time (T(Q)) of 40.8 days. (131)ICC49 alone and imatinib alone also delayed the tumor growth to T(Q) of 30.2 and 31.2 days, respectively. Unanticipated was the significant response of SW1990 to a brief treatment with imatinib given i.p. at 100 mg/kg b.i.d. for 3 days. Xenografts in control mice receiving injection of PBS had T(Q) of 23 days.

CONCLUSIONS

The inclusion of imatinib in the radioimmunotherapy regimen is beneficial and it does not produce any overt side effects. The improved responses of pancreatic cancer xenografts to the multimodality treatment comprising radioimmunotherapy and platelet-derived growth factor receptor-beta inhibition suggest that this approach to therapy of pancreatic cancer may also be successful in patients.

The stem cell factor/c-kit receptor pathway enhances proliferation and invasion of pancreatic cancer cells

BACKGROUND

The transmembrane protein c-kit is a receptor tyrosine kinase (KIT) and KIT is expressed in solid tumors and hematological malignancies such as gastrointestinal stromal tumor (GIST), small-cell lung cancer and chronic myelogenous leukemia (CML). KIT plays a critical role in cell proliferation and differentiation and represents a logical therapeutic target in GIST and CML. In pancreatic cancer, c-kit expression has been observed by immunohistochemical techniques. In this study, we examined the influence of c-kit expression on proliferation and invasion using five pancreatic cancer cell lines. In addition, the inhibitory effect of imatinib mesylate on stem cell factor (SCF)-induced proliferation and invasion was evaluated. Finally, we also analyzed KIT and SCF expression in pancreatic cancer tissues using immunohistochemistry and correlated the results with clinical features.

RESULTS

RT-PCR revealed that two pancreatic cancer cell lines, PANC-1 and SW1990, expressed c-kit mRNA. By Western blot analysis, c-kit protein was also present in those lines. In KIT-positive pancreatic cancer cell lines, proliferation and invasion were significantly enhanced by addition of SCF. In contrast, SCF did not enhance proliferation and invasion in the three KIT-negative lines (BxPC-3, Capan-2 and MIA PaCa-2). 5 muM imatinib mesylate significantly inhibited SCF-enhanced proliferation to the same extent compared with the control. Similarly, SCF-enhanced invasive ability was significantly inhibited by 5 muM imatinib mesylate. KIT was expressed in 16 of 42 clinical specimens by immunohistochemistry, and KIT expression was significantly related to venous system invasion. Furthermore, patients expressing both KIT and SCF had a somewhat lower survival.

CONCLUSION

Our results demonstrated that the SCF-KIT pathway enhanced the proliferation and invasiveness in KIT-positive pancreatic cancer cell lines and that the enhanced proliferation and invasion were inhibited by imatinib mesylate. We propose that inhibitors of c-kit tyrosine kinase receptor have the potential to slow the progression of KIT-positive pancreatic cancers.

The tyrosine kinase inhibitor imatinib fails to inhibit pancreatic cancer progression

Imatinib targets KIT and platelet-derived growth factor receptors (PDGFR) and is highly effective in the treatment of CML and GIST patients. Pancreatic cancers express KIT and PDGFRs. Therefore, 26 patients with unresectable pancreatic cancer were randomized to either gemcitabine (1000 mg/m2 weekly) or imatinib (2x400 mg po) treatment daily. Pancreatic adenocarcinoma was confirmed histologically and expression of KIT and PDGFRbeta was determined immunohistochemically in the biopsy specimens. Quality of life was assessed with two standard questionnaires. No objective responses were seen in either group. Median time to progression was 77 and 29 days (P=0.411) and median survival time was 140 and 60 days (P=0.517) for gemcitabine and imatinib, respectively. Survival and treatment responses were independent of KIT and PDGFRbeta expression in patients treated with imatinib. Grade 3/4 toxicities of imatinib treatment were anemia, elevated liver enzymes, vomiting, and dyspnea. Patients treated with imatinib reported diarrhoea and/or altered bowel function more frequently, which were treatable symptomatically. Quality of life was similar in both groups. In this small series of pancreatic cancer patients, treatment with imatinib was not associated with a significant control of cancer progression.

Protein kinase PKC delta and c-Abl are required for mitochondrial apoptosis induction by genotoxic stress in the absence of p53, p73 and Fas receptor

Doxorubicin, cis-diamminedichloroplatinum (II) and 5-fluorouracil used in chemotherapy induce apoptosis in Hep3B cells in the absence of p53, p73, and functional Fas. Since mediators remain unknown, the requirement of PKC delta (PKCdelta) and c-Abl was investigated. Suppression of c-Abl or PKCdelta expression using SiRNAs impaired PARP cleavage, Gleevec and/or rottlerin inhibited the induction of the subG1 phase and the increase of reactive oxygen species level. Co-precipitations and phosphorylations to mitochondria of c-Abl, PKCdelta and Bcl-X(L/s) were induced. A depolarization of the mitochondrial membrane and activations of caspase-2 and -9 were observed. We propose that, in the absence of p53, p73 and Fas, genotoxic drugs could require both PKCdelta and c-Abl to induce apoptosis through the mitochondrial pathway.

Differential effects of imatinib on PDGF-induced proliferation and PDGF receptor signaling in human arterial and venous smooth muscle cells

Platelet-derived growth factor (PDGF) has been implicated in smooth muscle cell (SMC) proliferation, a key event in the development of myointimal hyperplasia in vascular grafts. Recent evidence suggests that the PDGF receptor (PDGFR) tyrosine kinase inhibitor, imatinib, can prevent arterial proliferative diseases. Because hyperplasia is far more common at the venous anastomosis than the arterial anastomosis in vascular grafts, we investigated whether imatinib also inhibited venous SMC (VSMC) proliferation, and examined possible differences in its mechanism of action between VSMC and arterial SMC (ASMC). Human ASMC and VSMC were stimulated with PDGF-AB, in the presence or absence of imatinib (0.1-10 microM). Proliferation was assayed using the 5-bromo-2'-deoxyuridine (BrdU) incorporation assay, while PDGFR, Akt and ERK1/2-mitogen activated protein kinase (MAPK) signaling pathways were investigated by immunoblotting. The proliferative response to PDGF at 50 and 100 ng/ml was 32 and 43% greater, respectively, in VSMC than in ASMC. Similarly, PDGF-stimulated proliferation was more sensitive to inhibition by imatinib in VSMC than ASMC (IC(50) = 0.05 microM vs. 0.4 microM; P < 0.01). Imatinib also more effectively inhibited PDGF-induced phosphorylation of PDGFRbeta and Akt in VSMC, compared to ASMC. These data highlight inherent pharmacodynamic differences between VSMC and ASMC in receptor and cell signaling functions and suggest that imatinib therapy may be useful for the prevention of venous stenosis in vascular grafts.

Imatinib mesylate (Gleevec) downregulates telomerase activity and inhibits proliferation in telomerase-expressing cell lines

Imatinib mesylate (IM) is a tyrosine kinase inhibitor, which inhibits phosphorylation of downstream proteins involved in BCR-ABL signal transduction. It has proved beneficial in treating patients with chronic myeloid leukaemia (CML). In addition, IM demonstrates activity against malignant cells expressing c-kit and platelet-derived growth factor receptor (PDGF-R). The activity of IM in the blastic crisis of CML and against various myeloma cell lines suggests that this drug may also target other cellular components. In the light of the important role of telomerase in malignant transformation, we evaluated the effect of IM on telomerase activity (TA) and regulation in various malignant cell lines. Imatinib mesylate caused a dose-dependent inhibition of TA (up to 90% at a concentration of 15 μM IM) in c-kit-expressing SK-N-MC (Ewing sarcoma), SK-MEL-28 (melanoma), RPMI 8226 (myeloma), MCF-7 (breast cancer) and HSC 536/N (Fanconi anaemia) cells as well as in ba/F3 (murine pro-B cells), which do not express c-kit, BCR-ABL or PDGF-R. Imatinib mesylate did not affect the activity of other DNA polymerases. Inhibition of TA was associated with 50% inhibition of proliferation. The inhibition of proliferation was associated with a decrease in the S-phase of the cell cycle and an accumulation of cells in the G2/M phase. No apoptosis was observed. Inhibition of TA was caused mainly by post-translational modifications: dephosphorylation of AKT and, to a smaller extent, by early downregulation of hTERT (the catalytic subunit of the enzyme) transcription. Other steps of telomerase regulation were not affected by IM. This study demonstrates an additional cellular target of IM, not necessarily mediated via known tyrosine kinases, that causes inhibition of TA and cell proliferation.

Effects of STI571 and p27 gene clone on proliferation and apoptosis of K562 cells

AIM: To investigate the combined effect of STI571 and p27 gene clone on the regulation of proliferation, cell cycle and apoptosis of K562 cell line.

METHODS: p27 gene was obtained by RT-PCR, and its sequence was approved to be correct. Then p27-pcDNA3.1 vector was constructed and transfected into K562 cell line. p27-pcDNA3.1-K562 cell clone was screened by G418 after transfection, p27 protein was identified by Western blot. MTT was used to detect the survival rate of the cell. Flow cytometry was used to detect cell cycle and apoptosis index.

RESULTS: The expression of p27 protein could be detected by Western blot in p27-pcDNA3.1-K562 cells. A strong inhibition of cell proliferation was observed in p27-pcDNA3.1 -K562 cells as compared with that of the control (pcDNA3.1 -K562 cells). The cells at G0/G1 phase were significantly increased, and cells at S phase were greatly declined. The apoptosis index was increased greatly after p27-pcDNA3.1-K562 cells were treated with STI571, and survival rate of the cell was markedly declined (0.35-0.58, P<0.05-0.048 vs STI571-K562 cell, 0.35-0.72, P<0.01-0.001 vs p27-K562 cell).

CONCLUSION: p27 and STI571 have a synergistic action on inhibition of proliferation and induction of apoptosis on K562 cells.

Survival after surgical management of pancreatic adenocarcinoma: does curative and radical surgery truly exist?

Surgery for pancreatic cancer offers a low success rate but it provides the only likelihood of cure. Modern series show that, in experienced hands, the standard Whipple procedure is associated with a 5-year survival of 10%-20%, with a perioperative mortality rate of less than 5%. Most patients, however, will develop recurrent disease within 2 years after curative treatment. This occurs, usually, either at the site of resection or in the liver. This suggests the presence of micrometastases at the time of operation. Negative lymph nodes are the strongest predictor for long-term survival. Other predictors for a favourable outcome are tumour size, radical surgery and a histopathologically well-differentiated tumour. Adjuvant therapy has, so far, shown only modest results, with 5FU chemotherapy, to date, the only proven agent able to increase survival. Nowadays, the choice of therapy should be based on histopathological assessment of the tumour. Knowledge of the molecular basis of pancreatic cancer has led to various discoveries concerning its character and type. Well-known examples of genetic mutations in adenocarcinoma of the pancreas are k-ras, p53, p16, DPC4. Use of molecular diagnostics and markers in the assessment of tumour biology may, in future, reveal important subtypes of this type of tumour and may possibly predict the response to adjuvant therapy. Defining the subtypes of pancreatic cancer will, hopefully, lead to target-specific, less toxic and finally more effective therapies. Long-term survival is observed in only a very small group of patients, contradicting the published actuarial survival rates of 10%-45%. Assessment of clinical benefit from surgery and adjuvant therapy should, therefore, not only be based on actuarial survival but also on progression-free survival, actual survival, median survival and quality of life (QOL) indicators. Survival in surgical series is usually calculated by actuarial methods. If there is no information on the total number of patients and the number of actual survivors, and no clear definition of the subset of patients, actuarial survival curves can prove to be misleading. Proper assessment of QOL after surgery and adjuvant therapy is of the utmost importance, as improvements in survival rates have, so far, proved to be disappointing.

Hypertonic stress activates glycogen synthase kinase 3beta-mediated apoptosis of renal medullary interstitial cells, suppressing an NFkappaB-driven cyclooxygenase-2-dependent survival pathway

The survival of renal medullary interstitial cells (RMICs) requires their adaptation to rapid shifts in ambient tonicity normally occurring in the renal medulla. Previous studies determined that cyclooxygenase-2 (COX 2) activation is critical for this adaptation. The present studies find that these adaptive mechanisms are dampened by the simultaneous activation of an apoptotic pathway linked to a glycogen synthase kinase 3beta (GSK 3beta). Inhibition of GSK 3 by LiCl or specific small molecule GSK inhibitors increased RMIC survival following hypertonic stress, and transduction of RMICs with a constitutively active GSK 3beta (AdGSK 3betaA9) significantly increased apoptosis, consistent with a proapoptotic role of GSK 3beta. Following GSK 3beta inhibition, increased survival was accompanied by increased COX 2 expression and COX 2 reporter activity. In contrast, GSK 3beta overexpression reduced COX 2 reporter activity. Importantly, enhanced RMIC survival produced by GSK 3beta inhibition was completely dependent on COX 2 because it was abolished by a COX 2-specific inhibitor, SC58236. The signaling pathway by which GSK 3beta suppresses COX 2 expression was then explored. GSK 3beta inhibition increased both NFkappaB and beta-catenin activity associated with decreased IkappaB and increased beta-catenin levels. The increase in COX 2 following GSK 3beta inhibition was entirely blocked by NFkappaB inhibition using mutant IkappaB adenovirus. However, adenoviral overexpression of beta-catenin did not increase COX 2 levels. These findings suggest that GSK 3beta negatively regulates COX 2 expression and that GSK 3beta inhibitors protect RMICs from hypertonic stress via induction of NFkappaB-COX 2-dependent pathway.