Focus on pancreas cancer

Loss of runt-related transcription factor 3 induces gemcitabine resistance in pancreatic cancer

BACKGROUND & AIM

Runt-related transcription factor 3 (RUNX3) is a tumor suppressor gene that is expressed in gastric and other cancers including pancreatic cancer. However, the precise function of RUNX3 in pancreatic cancer has not been fully elucidated. In this study, we aimed to determine the effect of decreased RUNX3 expression in pancreatic cancer.

METHODS

This study included 36 patients with primary pancreatic cancer, who had undergone pancreaticoduodenectomy. All patients were treated with 1000 mg/m2 gemcitabine after the surgery. The pancreatic cancer cell lines PANC-1, MIAPaCa-2, BxPC-3, SUIT-2, and KLM-1 were used for immunoblotting analysis of RUNX3 and multidrug resistance protein (MRP) expressions. Ectopic RUNX3 expression was achieved by cDNA transfection of the cells, and small interfering RNA (siRNA) against RUNX3 was used to knock down endogenous RUNX3. Cell growth in the presence of gemcitabine was assessed using the MTT assay.

RESULTS

Patients with RUNX3-positive and RUNX3-negative pancreatic cancer had a median survival of 1006 and 643 days, respectively. Exogenous RUNX3 expression reduced the expression of MRP1, MRP2, and MRP5 in endogenous RUNX3-negative cells, whereas RUNX3 siRNA increased the expressions of these genes in endogenous RUNX3-positive cells. Exogenous RUNX3 expression decreased gemcitabine IC50 in RUNX3-negative cells.

CONCLUSION

Loss of RUNX3 expression contributes to gemcitabine resistance by inducing MRP expression, thereby resulting in poor patient survival.

Ras GTPases: codon bias holds KRas down but not out

Rare codons selectively limit the accumulation of Ras family member proteins with important consequences for Ras pathway activation and tumorigenesis.

Enhancing sorafenib-mediated sensitization to gemcitabine in experimental pancreatic cancer through EMAP II

Background

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive human malignancies and tends to be relatively resistant to conventional therapies. Activated Ras oncogene mutations are found in up to 90% of PDAC, leading to activation of the Ras/Raf/MEK/ERK signaling pathway. Sorafenib is a multikinase inhibitor of the Ras/Raf/MEK/ERK pathway and of tumor angiogenesis. Endothelial monocyte activating polypeptide II (EMAP) enhances gemcitabine effects in PDAC. Antitumor activity of sorafenib was evaluated in combination with gemcitabine (Gem) and the antiangiogenic agent EMAP in experimental PDAC.

Methods

Cell proliferation and protein expression were analyzed by WST-1 assay and Western blotting. Animal survival studies were performed in murine PDAC xenografts.

Results

Sorafenib decreased phospho-MEK, phospho-ERK1/2, phospho-p70S6K and phospho-4EBP-1 expression in PDAC cells. Sorafenib inhibited in vitro proliferation of all four PDAC cell lines tested. Additive effects on cell proliferation inhibition were observed in the gemcitabine-sorafenib combination in PDAC cells, and in combinations of sorafenib or EMAP with gemcitabine in endothelial (HUVEC) and fibroblast (WI-38) cells. Sorafenib, alone or in combination with gemcitabine and EMAP, induced apoptosis in HUVECs and WI-38 cells as observed via increased expression of cleaved poly (ADP-ribose) polymerase-1 (PARP-1) and caspase-3 proteins. Compared to controls (median survival: 22 days), animal survival increased after Gem therapy (29 days) but not in sorafenib (23 days) or EMAP therapy alone (25 days). Further increases in survival occurred in combination therapy groups Gem+sorafenib (30 days, p=0.004), Gem+EMAP (33 days, p=0.002), and Gem+sorafenib+EMAP (36 days, p=0.004), but not after the sorafenib+EMAP combination (24 days).

Conclusions

These findings demonstrate that the addition of a polymechanistic antiangiogenic agent such as EMAP can enhance the combination treatment effects of sorafenib and cytotoxic PDAC therapy.

Suppression of AKT phosphorylation restores rapamycin-based synthetic lethality in SMAD4-defective pancreatic cancer cells

mTOR has been implicated in survival signals for many human cancers. Rapamycin and TGF-β synergistically induce G1 cell-cycle arrest in several cell lines with intact TGF-β signaling pathway, which protects cells from the apoptotic effects of rapamycin during S-phase of the cell cycle. Thus, rapamycin is cytostatic in the presence of serum/TGF-β and cytotoxic in the absence of serum. However, if TGF-β signaling is defective, rapamycin induced apoptosis in both the presence and absence of serum/TGF-β in colon and breast cancer cell lines. Because genetic dysregulation of TGF-β signaling is commonly observed in pancreatic cancers-with defects in the Smad4 gene being most prevalent, we hypothesized that pancreatic cancers would display a synthetic lethality to rapamycin in the presence of serum/TGF-β. We report here that Smad4-deficient pancreatic cancer cells are killed by rapamycin in the absence of serum; however, in the presence of serum, we did not observe the predicted synthetic lethality with rapamycin. Rapamycin also induced elevated phosphorylation of the survival kinase Akt at Ser473. Suppression of rapamycin-induced Akt phosphorylation restored rapamycin sensitivity in Smad4-null, but not Smad4 wild-type pancreatic cancer cells. This study shows that the synthetic lethality to rapamycin in pancreatic cancers with defective TGF-β signaling is masked by rapamycin-induced increases in Akt phosphorylation. The implication is that a combination of approaches that suppress both Akt phosphorylation and mTOR could be effective in targeting pancreatic cancers with defective TGF-β signaling.

Chapter One---Cancer terminator viruses and approaches for enhancing therapeutic outcomes

No single or combinatorial therapeutic approach has proven effective in decreasing morbidity or engendering a cure of metastatic cancer. In principle, conditionally replication-competent adenoviruses that induce tumor oncolysis through cancer-specific replication hold promise for cancer therapy. However, a single-agent approach may not be adequate to completely eradicate cancer in a patient because most cancers arise from abnormalities in multiple genetic and signal transduction pathways and targeting disseminated metastases is difficult to achieve. Based on these considerations, a novel class of cancer destroying adenoviruses have been produced, cancer terminator viruses (CTVs), in which cancer-specific replication is controlled by the progression-elevated gene-3 promoter and replicating viruses produce a second transgene encoding an apoptosis-inducing and immunomodulatory cytokine, either melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) or interferon-γ. This review focuses on these viruses and ways to improve their delivery systemically and enhance their therapeutic efficacy.

Transforming mutations of RAC guanosine triphosphatases in human cancers

Members of the RAS superfamily of small guanosine triphosphatases (GTPases) transition between GDP-bound, inactive and GTP-bound, active states and thereby function as binary switches in the regulation of various cellular activities. Whereas HRAS, NRAS, and KRAS frequently acquire transforming missense mutations in human cancer, little is known of the oncogenic roles of other small GTPases, including Ras-related C3 botulinum toxin substrate (RAC) proteins. We show that the human sarcoma cell line HT1080 harbors both NRAS(Q61K) and RAC1(N92I) mutant proteins. Whereas both of these mutants were able to transform fibroblasts, knockdown experiments indicated that RAC1(N92I) may be the essential growth driver for this cell line. Screening for RAC1, RAC2, or RAC3 mutations in cell lines and public databases identified several missense mutations for RAC1 and RAC2, with some of the mutant proteins, including RAC1(P29S), RAC1(C157Y), RAC2(P29L), and RAC2(P29Q), being found to be activated and transforming. P29S, N92I, and C157Y mutants of RAC1 were shown to exist preferentially in the GTP-bound state as a result of a rapid transition from the GDP-bound state, rather than as a result of a reduced intrinsic GTPase activity. Activating mutations of RAC GTPases were thus found in a wide variety of human cancers at a low frequency; however, given their marked transforming ability, the mutant proteins are potential targets for the development of new therapeutic agents.

Exomic sequencing of medullary thyroid cancer reveals dominant and mutually exclusive oncogenic mutations in RET and RAS

CONTEXT

Medullary thyroid cancer (MTC) is a rare thyroid cancer that can occur sporadically or as part of a hereditary syndrome.

OBJECTIVE

To explore the genetic origin of MTC, we sequenced the protein coding exons of approximately 21,000 genes in 17 sporadic MTCs.

PATIENTS AND DESIGN

We sequenced the exomes of 17 sporadic MTCs and validated the frequency of all recurrently mutated genes and other genes of interest in an independent cohort of 40 MTCs comprised of both sporadic and hereditary MTC.

RESULTS

We discovered 305 high-confidence mutations in the 17 sporadic MTCs in the discovery phase, or approximately 17.9 somatic mutations per tumor. Mutations in RET, HRAS, and KRAS genes were identified as the principal driver mutations in MTC. All of the other additional somatic mutations, including mutations in spliceosome and DNA repair pathways, were not recurrent in additional tumors. Tumors without RET, HRAS, or KRAS mutations appeared to have significantly fewer mutations overall in protein coding exons.

CONCLUSIONS

Approximately 90% of MTCs had mutually exclusive mutations in RET, HRAS, and KRAS, suggesting that RET and RAS are the predominant driver pathways in MTC. Relatively few mutations overall and no commonly recurrent driver mutations other than RET, HRAS, and KRAS were seen in the MTC exome.

Inhibition of S6 kinase suppresses the apoptotic effect of eIF4E ablation by inducing TGF-β-dependent G1 cell cycle arrest

The mammalian target of rapamycin complex 1 (mTORC1) is a critical regulator of cap-dependent translation through its direct activation of ribosomal protein p70 S6 kinase (S6 kinase) and indirect activation of eukaryotic initiation factor 4E (eIF4E). We recently reported that inhibition of eIF4E expression caused apoptosis in cancer cells in the absence of serum. This was indicated by treatment with the mTORC1 inhibitor rapamycin, which suppressed both S6 kinase and 4E-BP1 phosphorylation (dephosphorylated 4E-BP1 binds and inactivates eIF4E), or by knockdown of eIF4E. We report here that knockdown of eIF4E also causes apoptosis in the presence of serum. This was unexpected because rapamycin induces G1 cell cycle arrest in the presence of serum. Upon investigation, we have found that inactivated S6 kinase prevents the apoptotic effect observed by singular knockdown of eIF4E and results in G1 cell cycle arrest. This effect is dependent on TGF-β (transforming growth factor-β) signaling which contributes to G1 cell cycle arrest. Suppression of S6 kinase phosphorylation alone is insufficient to mediate cell cycle arrest, indicating that complete G1 cell cycle arrest is due to suppression of both S6 kinase and eIF4E. These data indicate that the cytostatic effect of rapamycin is suppression of both S6 kinase and eIF4E, while the cytotoxic effects are due suppression of eIF4E in the absence of S6 kinase-dependent activation of TGF-β signals. Our findings place an importance on the evaluating the activity/expression level of S6 kinase and eIF4E as readouts for rapamycin/rapalog efficacy.

Characterization of a membrane-active anti-tumor agent, UA8967

Deletions or mutations in the tumor suppressor gene DPC4 (deleted in pancreatic carcinoma locus 4) are common in colon and pancreatic cancers. Using the Target-related Affinity Profiling (TRAP) chemical library screening method, a novel agent, UA8967, was selected for further studies because it showed greater potency in DPC4-deleted HCT-116 colon cancer cells. Cytotoxicity studies in six pancreatic cancer cell lines (MiaPaca-2, Panc-1, BxPC3, CF-PAC1, AsPC1, and T3M4), one normal human pancreatic ductal epithelial line (HPDE-6) and the HCT-116 DPC4(+/+) and HCT-116 DPC4(-/-) colon cancer cells showed IC50s ranging from 12-61 μM for exposure times of 72 h. Analysis of schedule dependence showed no advantage for long drug exposure times. There was also no selective inhibition of DNA, RNA or protein synthesis after exposure to UA8967. At 24-48 h, there was an accumulation of cells in G0/G1-phase and a proportionate reduction in S-phase cells. Within 1-6 h of exposure, cells were found to undergo an autophagic response, followed at 24 h by a low level of caspase-independent apoptosis with some necrosis. Because of the relatively non-specific mechanistic effects of UA8967, plasma membrane viability was evaluated using uptake of trypan blue and Sytox® Green dyes, and leakage of LDH. There was a dose dependent increase in Sytox® Green staining, trypan blue uptake and LDH leakage with increasing concentrations of UA8967, suggesting that UA8967 is affecting the plasma membrane. The DPC4(-/-) cells were more sensitive to UA8967 but not to DMSO, suggesting a drug-specific effect on cell membrane integrity.

miR-148b functions as a tumor suppressor in pancreatic cancer by targeting AMPKα1

miRNAs are small noncoding RNAs that participate in a variety of biologic processes, and dysregulation of miRNA is always associated with cancer development and progression. Aberrant expression of miR-148b has been found in some types of cancer, but its expression and potential biologic role in pancreatic cancer are still largely unknown. In this study, our data showed that miR-148b was significantly downregulated in 48 pairs of human pancreatic cancer tissues and five cell lines. Furthermore, the deregulated miR-148b was correlated with increased tumor size, late tumor-node-metastasis stage, lymphatic invasion, distant metastasis, and worse prognosis in pancreatic cancer. Functional studies indicated overexpression of miR-148b dramatically suppressed the growth of cancer cells, attributable to induction of apoptosis and cell-cycle arrest at S-phase. Meanwhile, miR-148b remarkably inhibited invasion and enhanced chemosensitivity of pancreatic cancer cells. Moreover, ectopic expression of miR-148b was able to inhibit tumorigenicity in nude mice. Further studies revealed that AMPKα1 might be the direct target gene of miR-148b, and overexpressed AMPKα1 inversely correlated with miR-148b in pancreatic cancer. Silencing of AMPKα1 with RNA interference inhibited the growth of pancreatic cancer cells in vitro and in vivo and also induced apoptosis, cell-cycle arrest, and inhibited invasion of cancer cells, which is consistent with the effects of miR-148b overexpression. In conclusion, miR-148b can inhibit cell proliferation, invasion, and enhance chemosensitivity of pancreatic cancer by targeting AMPKα1. Our present results implicate the potential effects of miR-148b on prognosis and treatment of pancreatic cancer.

LCL124, a cationic analog of ceramide, selectively induces pancreatic cancer cell death by accumulating in mitochondria

Treatment of pancreatic cancer that cannot be surgically resected currently relies on minimally beneficial cytotoxic chemotherapy with gemcitabine. As the fourth leading cause of cancer-related death in the United States with dismal survival statistics, pancreatic cancer demands new and more effective treatment approaches. Resistance to gemcitabine is nearly universal and appears to involve defects in the intrinsic/mitochondrial apoptotic pathway. The bioactive sphingolipid ceramide is a critical mediator of apoptosis initiated by a number of therapeutic modalities. It is noteworthy that insufficient ceramide accumulation has been linked to gemcitabine resistance in multiple cancer types, including pancreatic cancer. Taking advantage of the fact that cancer cells frequently have more negatively charged mitochondria, we investigated a means to circumvent resistance to gemcitabine by targeting delivery of a cationic ceramide (l-t-C6-CCPS [LCL124: ((2S,3S,4E)-2-N-[6'-(1″-pyridinium)-hexanoyl-sphingosine bromide)]) to cancer cell mitochondria. LCL124 was effective in initiating apoptosis by causing mitochondrial depolarization in pancreatic cancer cells but demonstrated significantly less activity against nonmalignant pancreatic ductal epithelial cells. Furthermore, we demonstrate that the mitochondrial membrane potentials of the cancer cells were more negative than nonmalignant cells and that dissipation of this potential abrogated cell killing by LCL124, establishing that the effectiveness of this compound is potential-dependent. LCL124 selectively accumulated in and inhibited the growth of xenografts in vivo, confirming the tumor selectivity and therapeutic potential of cationic ceramides in pancreatic cancer. It is noteworthy that gemcitabine-resistant pancreatic cancer cells became more sensitive to subsequent treatment with LCL124, suggesting that this compound may be a uniquely suited to overcome gemcitabine resistance in pancreatic cancer.

TGF-β sensitivity is determined by N-linked glycosylation of the type II TGF-β receptor

N-linked glycosylation is a critical determinant of protein structure and function, regulating processes such as protein folding, stability and localization, ligand–receptor binding and intracellular signalling. TβRII [type II TGF-β (transforming growth factor β) receptor] plays a crucial role in the TGF-β signalling pathway. Although N-linked glycosylation of TβRII was first demonstrated over a decade ago, it was unclear how this modification influenced TβRII biology. In the present study, we show that inhibiting the N-linked glycosylation process successfully hinders binding of TGF-β1 to TβRII and subsequently renders cells resistant to TGF-β signalling. The lung cancer cell line A549, the gastric carcinoma cell line MKN1 and the immortal cell line HEK (human embryonic kidney)-293 exhibit reduced TGF-β signalling when either treated with two inhibitors, including tunicamycin (a potent N-linked glycosylation inhibitor) and kifunensine [an inhibitor of ER (endoplasmic reticulum) and Golgi mannosidase I family members], or introduced with a non-glycosylated mutant version of TβRII. We demonstrate that defective N-linked glycosylation prevents TβRII proteins from being transported to the cell surface. Moreover, we clearly show that not only the complex type, but also a high-mannose type, of TβRII can be localized on the cell surface. Collectively, these findings demonstrate that N-linked glycosylation is essentially required for the successful cell surface transportation of TβRII, suggesting a novel mechanism by which the TGF-β sensitivity can be regulated by N-linked glycosylation levels of TβRII.

EGCG inhibits growth of human pancreatic tumors orthotopically implanted in Balb C nude mice through modulation of FKHRL1/FOXO3a and neuropilin

Human pancreatic cancer is currently one of the fourth leading causes of cancer-related mortality with a 5-year survival rate of less than 5 %. Since pancreatic carcinoma is largely refractory to conventional therapies, there is a strong medical need for the development of novel and innovative cancer preventive strategies. The forkhead transcription factors of the O class (FOXO) play a major role in cell proliferation, angiogenesis, metastasis, and tumorigenesis. The objectives of this study were to examine whether FKHRL1/FOXO3a modulates antitumor activity of (-)-epigallocatechin-3-gallate (EGCG), an active ingredient in green tea, in pancreatic cancer model in vivo. PANC-1 cells were orthotopically implanted into Balb c nude mice and gavaged with EGCG after tumor formation. Cell proliferation and apoptosis were measured by Ki67 and TUNEL staining, respectively. The expression of PI3K, AKT, ERK, and FOXO3a/FKHRL1 and its target genes were measured by the western blot analysis and/or q-RT-PCR. FOXO-DNA binding was measured by gel shift assay. EGCG-treated mice showed significant inhibition in tumor growth which was associated with reduced phosphorylation of ERK, PI3K, AKT, and FKHRL1/FOXO3a, and modulation of FOXO target genes. EGCG induced apoptosis by upregulating Bim and activating caspase-3. EGCG modulated markers of cell cycle (p27/KIP1), angiogenesis (CD31, VEGF, IL-6, IL-8, SEMA3F, and HIF1α), and metastasis (MMP2 and MMP7). The inhibition of VEGF by EGCG was associated with suppression of neuropilin. EGCG inhibited epithelial-mesenchymal transition by upregulating the expression of E-cadherin and inhibiting the expression of N-cadherin and Zeb1. These data suggest that EGCG inhibits pancreatic cancer orthotopic tumor growth, angiogenesis, and metastasis which are associated with inhibition of PI3K/AKT and ERK pathways and activation of FKHRL1/FOXO3a. As a conclusion, EGCG can be used for the prevention and/or treatment of pancreatic cancer.

AGR2 is a SMAD4-suppressible gene that modulates MUC1 levels and promotes the initiation and progression of pancreatic intraepithelial neoplasia

The mechanisms controlling expression of the putative oncogene AGR2 in pancreatic ductal adenocarcinoma (PDAC) are not well understood. We now show that AGR2 is a TGF-β-responsive gene in human pancreatic cancer cells, whose down-regulation is SMAD4-dependent. We also provide evidence supporting a role for AGR2 as an ER-chaperone for the cancer-associated mucin, MUC1. AGR2 is both sufficient and required for MUC1 expression in pancreatic cancer cells. Furthermore, AGR2 is co-expressed with MUC1 in mouse pancreatic intraepithelial neoplasia (mPanIN)-like lesions and in the cancer cells of four distinct genetically engineered mouse models of PDAC. We also show that Pdx1-Cre/LSL-Kras^G12D/Smad4^lox/lox mice heterozygous for Agr2 exhibit a delay in mPanIN initiation and progression to PDAC. It is proposed that loss of Smad4 may convert TGF-β from a tumor suppressor to a tumor promoter by causing the up-regulation of AGR2, which then leads to increased MUC1 expression, at which point both AGR2 and MUC1 facilitate mPanIN initiation and progression to PDAC.

Chronic cadmium exposure in vitro causes acquisition of multiple tumor cell characteristics in human pancreatic epithelial cells

BACKGROUND

Cancer may be a stem cell (SC)-based disease involving formation of cancer SCs (CSCs) potentially arising from transformation of normal SCs. Cadmium has been linked to human pancreatic cancer.

OBJECTIVE

We studied cadmium exposure of human pancreatic ductal epithelial (HPDE) cells and whether SCs may be targeted in this process.

METHODS

We chronically exposed HPDE cells to low level cadmium (1 μM) for ≤ 29 weeks. Nonadherent spheroid formation was used to indicate CSC-like cell production, and we assessed tumor cell characteristics in such spheres. Assessed tumor cell characteristics including secretion of matrix metalloproteinase-9 (MMP-9), invasion, and colony formation were fortified by evaluating expression of relevant genes by real-time reverse transcription polymerase chain reaction and by Western blot.

RESULTS

Increased MMP-9 secretion and overexpression of the pancreatic cancer marker S100P occurred in chronic (29 weeks of exposure) cadmium-exposed (CCE) cells. CCE cells also showed markedly higher colony formation and invasion, typical of cancer cells. Floating "spheres" of viable cells, known to contain an abundance of normal SCs or CSCs, form in vitro with many cell types. CCE cells produced 3-fold more spheres than control cells and were more invasive, secreted more MMP-9, and overexpressed markers for pancreatic SCs/CSCs (i.e., CXCR4, OCT4, CD44) and S100P, a marker for pancreatic cancer. CCE-derived spheres rapidly produced aggressive, highly branched, and poorly differentiated glandular-like structures in Matrigel.

CONCLUSIONS

Chronic cadmium exposure produced multiple tumor cell characteristics in HPDE cells and CCE cell-derived spheres. These data support the plausibility of cadmium as a human pancreatic carcinogen.

Silencing expression of ribosomal protein L26 and L29 by RNA interfering inhibits proliferation of human pancreatic cancer PANC-1 cells

Oncogenic KRAS, an important target for antitumor therapy, contributes to pancreatic cancer tumorigenesis, progression and maintenance. However, intracellular compensation regulation can help cells to resist the targeted therapy. Gene knockdown method such as RNAi may help to understand this intracellular regulatory system and discover novel therapeutic approach. In this study, two stable transfected cell lines were constructed through lentivirus-mediated shRNA targeting KRAS of PANC-1 cells, to investigate cell response to the knockdown of KRAS. Human whole genome microarray was then used to compare the gene expression profile. As a result, ribosomal proteins L26 and L29 (RPL26 and RPL29) were dramatically upregulated by KRAS-shRNA specifically. To identify whether RPL26 or RPL29 was critical for PANC-1 cells, siRNAs against RPL26 and RPL29 were designed and transfected in vitro. The results showed that knockdown of RPL26 or RPL29 expression significantly suppressed cell proliferation, induced cell arrest at G0/G1 phase and enhanced cell apoptosis. Reactive oxygen species (ROS) assay indicated that silencing of RPL26 or RPL29 markedly decreased the intracellular ROS generation. Our findings imply that siRNA interference against RPL26 and RPL29 is of potential value for intervention of pancreatic cancer.

Overcoming nucleoside analog chemoresistance of pancreatic cancer: a therapeutic challenge

Clinical refractoriness to nucleoside analogs (e.g., gemcitabine, capecitabine) is a major scientific problem and is one of the main reasons underlying the extremely poor prognostic state of pancreatic cancer. The drugs' effects are suboptimal partly due to cellular mechanisms limiting their transport, activation, and overall efficacy. Nonetheless, novel therapeutic approaches are presently under study to circumvent nucleoside analog resistance in pancreatic cancer. With these new approaches come additional challenges to be addressed. This review describes the determinants of chemoresistance in the gemcitabine cytotoxicity pathways, provides an overview of investigational approaches for overcoming chemoresistance, and discusses new challenges presented. Understanding the future directions of the field may assist in the successful development of novel treatment strategies for enhancing chemotherapeutic efficacy in pancreatic cancer.

Dissociation of the K-Ras4B/PDEδ complex upon contact with lipid membranes: membrane delivery instead of extraction

K-Ras4B is a small GTPase whose selective membrane localization and clustering into microdomains are mediated by its polybasic farnesylated C-terminus. The importance of the subcellular distribution for the signaling activity of K-Ras4B became apparent from recent in vivo studies, showing that the delta subunit of cGMP phosphodiesterase (PDEδ), which possesses a hydrophobic prenyl-binding pocket, is able to function as a potential binding partner for farnesylated proteins, thereby leading to a modulation of the spatiotemporal organization of K-Ras. Even though PDEδ has been suggested to serve as a cytosolic carrier for Ras, the functional transport mechanism still remains largely elusive. In this study, the effect of PDEδ on the interaction of GDP- and GTP-loaded K-Ras4B with neutral and anionic model biomembranes has been investigated by a combination of different spectroscopic and imaging techniques. The results show that PDEδ is not able to extract K-Ras4B from membranes. Rather, the K-Ras4B/PDEδ complex formed in bulk solution turned out to be unstable in the presence of heterogeneous membranes, resulting in a release of farnesylated K-Ras4B upon membrane contact. With the additional observation of enhanced membrane affinity for the K-Ras4B/PDEδ complex, a molecular mechanism for the PDEδ-K-Ras4B-membrane interaction could be proposed. This includes an effective delivery of PDEδ-solubilized K-Ras4B to the plasma membrane, probably through cytoplasmic diffusion, the dissociation of the K-Ras4B/PDEδ complex upon plasma membrane contact, and finally the membrane binding of released farnesylated K-Ras4B that leads to K-Ras4B-enriched microdomain formation.

Different subtypes of intraductal papillary mucinous neoplasm in the pancreas have distinct pathways to pancreatic cancer progression

BACKGROUND

Intraductal papillary mucinous neoplasm (IPMN) is recognized as a precursor lesion to pancreatic cancer, a unique pathological entity. IPMN has subtypes with different clinical characteristics. However, the molecular mechanisms of cancer progression from IPMN remain largely unknown. In this study we examined the differences in genetic alteration(s) among the IPMN subtypes.

METHODS

Surgically resected IPMNs (n = 25) were classified into four subtypes by hematoxylin and eosin (H&E) and mucin immunostaining. Mutations in KRAS, BRAF, and PIK3CA genes and expression of CDKN2A, TP53, SMAD4, phospho-ERK, and phospho-SMAD1/5/8 proteins were examined.

RESULTS

There were 11 gastric, 11 intestinal, one pancreatobiliary, and two oncocytic types in this study. We then compared the two major subtypes, gastric-type and intestinal-type IPMN. Gastric-type IPMN showed a significantly higher incidence of KRAS mutations (9/11, 81.8%) compared with intestinal type (3/11, 27.3%; p < 0.05), although the intestinal type showed a higher grade of dysplasia than gastric type (p < 0.01). All cases with KRAS mutations showed phospho-ERK immunostaining. In contrast, intestinal type (9/11, 81.8%) showed more frequent SMAD1/5/8 phosphorylation compared with gastric-type IPMN (3/11, 27.3%; p < 0.05%).

CONCLUSIONS

There may be distinct mechanisms of pancreatic cancer progression in the different subtypes of IPMN. In particular, KRAS mutation and bone morphogenetic protein-SMAD signaling status may be crucial diverging steps for the two representative pathways to pancreatic cancer in IPMN patients.

Chemotherapy and autophagy-mediated cell death in pancreatic cancer cells

Autophagy is an evolutionarily preserved degradation process of cytoplasmic cellular constituents and plays important physiological roles in human health and disease. It has been proposed that autophagy plays an important role both in tumor progression and in promotion of cancer cell death, although the molecular mechanisms responsible for this dual action of autophagy in cancer have not been elucidated. Pancreatic ductal adenocarcinoma is one of the most aggressive human malignancies with 2-3% five-year survival rate. Its poor prognosis has been attributed to the lack of specific symptoms and early detection tools, and its relatively refractory to traditional cytotoxic agents and radiotherapy. Experimental evidence pointed at autophagy as a pancreatic cancer cell mechanism to survive under adverse environmental conditions, or as a defective programmed cell death mechanism that favors pancreatic cancer cell resistance to treatment. Here, we consider several phenotypical alterations that have been related to increase or decrease the autophagic process in pancreatic tumor cells. We specially review autophagy as a cell death mechanism in response to chemotherapeutic drugs.

Functional specificity of ras isoforms: so similar but so different

H-ras, N-ras, and K-ras are canonical ras gene family members frequently activated by point mutation in human cancers and coding for 4 different, highly related protein isoforms (H-Ras, N-Ras, K-Ras4A, and K-Ras4B). Their expression is nearly ubiquitous and broadly conserved across eukaryotic species, although there are quantitative and qualitative differences of expression depending on the tissue and/or developmental stage under consideration. Extensive functional studies have determined during the last quarter century that these Ras gene products are critical components of signaling pathways that control eukaryotic cell proliferation, survival, and differentiation. However, because of their homology and frequent coexpression in various cellular contexts, it remained unclear whether the different Ras proteins play specific or overlapping functional roles in physiological and pathological processes. Initially, their high degree of sequence homology and the observation that all Ras isoforms share common sets of downstream effectors and upstream activators suggested that they were mostly redundant functionally. In contrast, the notion of functional specificity for each of the different Ras isoforms is supported at present by an increasing body of experimental observations, including 1) the fact that different ras isoforms are preferentially mutated in specific types of tumors or developmental disorders; 2) the different transforming potential of transfected ras genes in different cell contexts; 3) the distinct sensitivities exhibited by the various Ras family members for modulation by different GAPs or GEFs; 4) the demonstration that different Ras isoforms follow distinct intracellular processing pathways and localize to different membrane microdomains or subcellular compartments; 5) the different phenotypes displayed by genetically modified animal strains for each of the 3 ras loci; and 6) the specific transcriptional networks controlled by each isoform in different cellular settings.

Crosstalk between the canonical NF-κB and Notch signaling pathways inhibits Pparγ expression and promotes pancreatic cancer progression in mice

The majority of human pancreatic cancers have activating mutations in the KRAS proto-oncogene. These mutations result in increased activity of the NF-κB pathway and the subsequent constitutive production of proinflammatory cytokines. Here, we show that inhibitor of κB kinase 2 (Ikk2), a component of the canonical NF-κB signaling pathway, synergizes with basal Notch signaling to upregulate transcription of primary Notch target genes, resulting in suppression of antiinflammatory protein expression and promotion of pancreatic carcinogenesis in mice. We found that in the Kras(G12D)Pdx1-cre mouse model of pancreatic cancer, genetic deletion of Ikk2 in initiated pre-malignant epithelial cells substantially delayed pancreatic oncogenesis and resulted in downregulation of the classical Notch target genes Hes1 and Hey1. Tnf-α stimulated canonical NF-κB signaling and, in collaboration with basal Notch signals, induced optimal expression of Notch targets. Mechanistically, Tnf-α stimulation resulted in phosphorylation of histone H3 at the Hes1 promoter, and this signal was lost with Ikk2 deletion. Hes1 suppresses expression of Pparg, which encodes the antiinflammatory nuclear receptor Pparγ. Thus, crosstalk between Tnf-α/Ikk2 and Notch sustains the intrinsic inflammatory profile of transformed cells. These findings reveal what we believe to be a novel interaction between oncogenic inflammation and a major cell fate pathway and show how these pathways can cooperate to promote cancer progression.

Clinical trials of vaccines for immunotherapy in pancreatic cancer

A greater understanding of the molecular events that trigger oncogenesis and events that negatively regulate immune responses has allowed for the development of targeted therapies with specific vaccines to match tumor antigens coupled with immunotherapy specifically directed against that tumor's immunosuppressive microenvironment. In order to be effective, vaccine therapies need to both expand the immune response to tumors and overcome immunosuppressive microenvironments therein. Specifically, targeted therapy must be personalized for each cancer patient. While the idea of personalized targeted therapy may seem like a daunting task, it may not be that difficult as it could involve a relatively simple genetic test to identify gene mutations and additional immunohistochemical staining of tumors with antibodies directed against markers of negative immune regulation. The additional cost to personalize cancer therapy with these diagnostic tests is relatively small in comparison to the cost afforded to our healthcare system when inappropriate targeting therapies are administered to patients whose tumors do not express the targets of either the vaccine or the immune modulator. Despite the large cost, cancer patients whose tumors lack the targets of these therapies often receive no benefit from the therapy. The most illogical approach is to develop a study design and perform clinical trials of potential novel targeting drugs without knowledge or confirmation that the patients' tumors express the targets. Current cancer trials for pancreatic cancer patients are discussed in this article.

Resveratrol inhibits growth of orthotopic pancreatic tumors through activation of FOXO transcription factors

BACKGROUND

The forkhead transcription factors of the O class (FOXO) play a direct role in cellular proliferation, oxidative stress response, and tumorigenesis. The objectives of this study were to examine whether FOXOs regulate antitumor activities of resveratrol in pancreatic cancer cells in vitro and in vivo.

METHODOLOGY/PRINCIPAL FINDINGS

Pancreatic cancer cell lines were treated with resveratrol. Cell viability, colony formation, apoptosis and cell cycle were measured by XTT, soft agar, TUNEL and flow cytometry assays, respectively. FOXO nuclear translocation, DNA binding and transcriptional activities were measured by fluorescence technique, gelshift and luciferase assay, respectively. Mice were orthotopically implanted with PANC1 cells and orally gavaged with resveratrol. The components of PI3K and ERK pathways, FOXOs and their target gene expressions were measured by the Western blot analysis. Resveratrol inhibited cell viability and colony formations, and induced apoptosis through caspase-3 activation in four pancreatic cancer cell lines (PANC-1, MIA PaCa-2, Hs766T, and AsPC-1). Resveratrol induced cell cycle arrest by up-regulating the expression of p21/CIP1, p27/KIP1 and inhibiting the expression of cyclin D1. Resveratrol induced apoptosis by up-regulating Bim and activating caspase-3. Resveratrol inhibited phosphorylation of FOXOs, and enhanced their nuclear translocation, FOXO-DNA binding and transcriptional activities. The inhibition of PI3K/AKT and MEK/ERK pathways induced FOXO transcriptional activity and apoptosis. Furthermore, deletion of FOXO genes abrogated resveratrol-induced cell cycle arrest and apoptosis. Finally, resveratrol-treated mice showed significant inhibition in tumor growth which was associated with reduced phosphorylation of ERK, PI3K, AKT, FOXO1 and FOXO3a, and induction of apoptosis and FOXO target genes.

CONCLUSIONS

These data suggest that inhibition of ERK and AKT pathways act together to activate FOXO transcription factors which are involved in resveratrol-mediated pancreatic tumor growth suppression.

DNA mismatch repair network gene polymorphism as a susceptibility factor for pancreatic cancer

DNA repair plays a critical role in human cancers. We hypothesized that DNA mismatch repair gene variants are associated with risk of pancreatic cancer. We retrospectively genotyped 102 single-nucleotide polymorphisms (SNPs) of 13 mismatch repair related genes in 706 patients with pancreatic cancer and 706 cancer-free controls using the mass spectroscopy-based MassArray method. Association of genotype with pancreatic cancer risk was tested by multivariate logistic regression models. A significance level of P ≤ 0.0015 was set at the false discovery rate (FDR) <1% using the Beta-Uniform Mixture method. We found 28 SNPs related to altered pancreatic cancer risk (P < 0.05). Adjusting for multiple comparisons, MGMT I143V AG/GG, PMS2 IVS1-1121C > T TC/TT, and PMS2L3 Ex1 + 118C > T CT/TT genotypes showed significant main effects on pancreatic cancer risk at FDR <1% with OR (95% CI) of 0.60 (0.46-0.80), 1.44 (1.14-1.81), and 5.54 (2.10-14.61), respectively (P ≤ 0.0015). To demonstrate genotype-phenotype association, we measured O(6)-ethylguanosine (O(6)-EtGua) adduct levels in vitro by immunoslot blot assay in lymphocytes treated with N-ethyl-N-nitrosourea (ENU) in 297 case/control subjects. MGMT I143V GG, MGMT K178R GG, MSH6 G39E AG/AA, PMS2L3 IVS3 + 9A > G GA and TP73 IVS1-7449G > C CG/CC genotypes correlated with a higher level of ENU-induced DNA adducts. Haplotypes of MGMT, MSH6, PMS2, PMS2L3, and TP73 were significantly associated with pancreatic cancer risk (P ≤ 0.0015). Our findings suggest that mismatch repair gene variants may affect susceptibility to pancreatic cancer.

Insig2 is overexpressed in pancreatic cancer and its expression is induced by hypoxia

A hypoxic microenvironment is a characteristic feature of pancreatic cancer, and induces the expressions of various genes involved in malignant behaviors. Insulin-induced gene 2 (Insig2) has recently been shown to be correlated with cellular invasion in colon cancer. However, there have been no reports regarding its expression in pancreatic cancer. In this study, we evaluated Insig2 mRNA expression and the biological function of Insig2 in pancreatic cancer. We measured Insig2 mRNA expression in cultured pancreatic cancer cell lines and invasive ductal carcinoma (IDC) cells, normal pancreatic epithelial cells, and pancreatic intraepithelial neoplasia cells obtained by laser-capture microdissection. We also investigated the effects of Insig2-targeting siRNAs on the cell proliferation and cell invasion of pancreatic cancer cell lines. All pancreatic cancer cell lines expressed Insig2 mRNA. The PANC-1 and MIA PaCa-2 pancreatic cancer cell lines showed >2-fold higher Insig2 mRNA expression levels under hypoxic conditions (1% O2) than under normoxic conditions (21% O2 ). Cell proliferation was significantly decreased in SUIT-2 cells and cell invasion was significantly decreased in SUIT-2, Capan-2, and CFPAC-1 cells after transfection of the Insig2-targeting siRNAs. In analyses of microdissected cells, cells from IDC tissues expressed significantly higher levels of Insig2 mRNA than normal pancreatic cells (P < 0.001) and pancreatic intraepithelial neoplasia cells (P = 0.082). In analyses of IDC cells, the levels of Insig2 mRNA expression were significantly higher in late-stage patients than in early-stage patients. The present data suggest that Insig2 is associated with the malignant potential of pancreatic cancer under hypoxic conditions.

Activation of nuclear TR3 (NR4A1) by a diindolylmethane analog induces apoptosis and proapoptotic genes in pancreatic cancer cells and tumors

NR4A1 (Nur77, TR3) is overexpressed in pancreatic tumors and activation of TR3 by 1,1-bis(3'-indolyl)-1-(p-methoxyphenyl)methane (DIM-C-pPhOCH(3)) inhibits cell and tumor growth and induces apoptosis. Microarray analysis demonstrates that in L3.6pL pancreatic cancer cells DIM-C-pPhOCH(3) induces genes associated with metabolism, homeostasis, signal transduction, transcription, stress, transport, immune responses, growth inhibition and apoptosis. Among the most highly induced growth inhibitory and proapoptotic genes including activating transcription factor 3 (ATF3), p21, cystathionase, dual specificity phosphatase 1 and growth differentiation factor 15, RNA interference studies demonstrated that induction of all but the later gene by DIM-C-pPhOCH(3) were TR3-dependent. We also observed that DIM-C-pPhOCH(3) induced Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and induction of TRAIL was ATF3 dependent. Results of this and previous studies demonstrate that TR3 is unique among nuclear receptors since nuclear TR3 is activated or deactivated by diindolylmethane derivatives to induce different apoptotic and growth inhibitory pathways that inhibit pancreatic cancer cell and tumor growth.

The serum bone morphogenetic protein-2 level in non-small-cell lung cancer patients

Bone morphogenetic proteins (BMPs) are members of the TGF-β superfamily, and some studies demonstrated that BMPs enhance tumorigenesis and metastasis. The purpose of this study was to identify whether BMP-2 levels are elevated in the serum of non-small-cell lung cancer (NSCLC) patients and are associated with the stage and overall survival. Blood samples from 150 patients with NSCLC were analyzed. Also, 69 healthy volunteers were tested as control group. In NSCLC patients, whole blood was obtained before beginning any treatment modalities, and serum BMP-2 levels were quantified by commercially available ELISA kit. The NSCLC group demonstrated a significantly higher level of serum BMP-2 than the control group. (The median levels were 25.50 pg/ml for the control group and 72.23 pg/ml for the NSCLC group, P < 0.001). The median serum BMP-2 level in the advanced stage group (stage IIIb or IV) was significantly more elevated than that of the localized stage group (stage I, II, IIIa) (75.66 pg/ml and 44.36 pg/ml, P = 0.006). Patients with multiple metastatic sites (≥5) showed significantly higher level of serum BMP-2 than the patients with less than 5 metastatic sites. (79.39 pg/ml vs. 59.70 pg/ml, P = 0.013), and the median serum BMP-2 level from the patients with multiple metastatic organs (≥3) was significantly higher than that from the patients with single or two metastatic organs (<2) (89.39 pg/ml vs. 66.90 pg/ml, P = 0.001). Moreover, the patients with relatively lower BMP-2 level (≤70 pg/ml) had longer median overall survival than the patients with higher BMP-2 level (>70 pg/ml). (525 days vs. 260 days). One-year survival rate for the patients with lower BMP-2 level was also higher than that for the patients with higher BMP-2 level. (59.6% versus 40.2%, P = 0.034). The serum BMP-2 level is positively correlated with the stage and metastatic burden and maybe a probable predictor of survival in the NSCLC patients.

Expression of oncogenic K-ras and loss of Smad4 cooperate to induce the expression of EGFR and to promote invasion of immortalized human pancreas ductal cells

Activating mutation of K-ras and inactivation of DPC4 are two common genetic alterations that occur in the development and progression of pancreatic ductal adenocarcinomas (PDAC). A separate common event in PDAC progression is increased expression of phosphotyrosine kinase receptors (PTKRs). In our study, we examined whether activating mutations of K-ras and loss of Smad4 play a role in causing the aberrant expression of PTKRs. Immortalized human pancreas ductal cells (HPNE) were genetically modified by expressing oncogenic K-ras and/or by shRNA knockdown of Smad4. EGFR and erbB2 protein levels but not Ron or IGF-1R were substantially upregulated in HPNE cells that express K-ras((GD12)). The increased expression of EGFR in HPNE cells that expressed K-ras((GD12)) was mediated by both stabilizing EGFR protein and by increasing EGFR transcription. TGF-beta signaling partially suppressed K-ras((GD12)) induced EGFR transcription in Smad4 intact HPNE cells; whereas knockdown of Smad4 in cells expressing K-ras((GD12)) further enhanced expression of EGFR and erbB2. The upregulation of EGFR and erbB2 was associated with an increase of invasion, which was blocked by a kinase inhibitor of EGFR. Our study indicates for the first time, that oncogenic ras and loss of Smad signaling cooperate to upregulate EGFR and erbB2, which plays a role in promoting invasion.

Membrane proteomic analysis of pancreatic cancer cells

Background

Pancreatic cancer is one of the most aggressive human tumors due to its high potential of local invasion and metastasis. The aim of this study was to characterize the membrane proteomes of pancreatic ductal adenocarcinoma (PDAC) cells of primary and metastatic origins, and to identify potential target proteins related to metastasis of pancreatic cancer.

Methods

Membrane/membrane-associated proteins were isolated from AsPC-1 and BxPC-3 cells and identified with a proteomic approach based on SDS-PAGE, in-gel tryptic digestion and liquid chromatography with tandem mass spectrometry (LC-MS/MS). X! Tandem was used for database searching against the SwissProt human protein database.

Results

We identified 221 & 208 proteins from AsPC-1 and BxPC-3 cells, respectively, most of which are membrane or membrane-associated proteins. A hundred and nine proteins were found in both cell lines while the others were present in either AsPC-1 or BxPC-3 cells. Differentially expressed proteins between two cell lines include modulators of cell adhesion, cell motility or tumor invasion as well as metabolic enzymes involved in glycolysis, tricarboxylic acid cycle, or nucleotide/lipid metabolism.

Conclusion

Membrane proteomes of AsPC-1 (metastatic) and BxPC-3 (primary) cells are remarkably different. The differentially expressed membrane proteins may serve as potential targets for diagnostic and therapeutic interventions.

Inhibition of NFkappaB and pancreatic cancer cell and tumor growth by curcumin is dependent on specificity protein down-regulation

Curcumin activates diverse anticancer activities that lead to inhibition of cancer cell and tumor growth, induction of apoptosis, and antiangiogenic responses. In this study, we observed that curcumin inhibits Panc28 and L3.6pL pancreatic cancer cell and tumor growth in nude mice bearing L3.6pL cells as xenografts. In addition, curcumin decreased expression of p50 and p65 proteins and NFkappaB-dependent transactivation and also decreased Sp1, Sp3, and Sp4 transcription factors that are overexpressed in pancreatic cancer cells. Because both Sp transcription factors and NFkappaB regulate several common genes such as cyclin D1, survivin, and vascular endothelial growth factor that contribute to the cancer phenotype, we also investigated interactions between Sp and NFkappaB transcription factors. Results of Sp1, Sp3, and Sp4 knockdown by RNA interference demonstrate that both p50 and p65 are Sp-regulated genes and that inhibition of constitutive or tumor necrosis factor-induced NFkappaB by curcumin is dependent on down-regulation of Sp1, Sp3, and Sp4 proteins by this compound. Curcumin also decreased mitochondrial membrane potential and induced reactive oxygen species in pancreatic cancer cells, and this pathway is required for down-regulation of Sp proteins in these cells, demonstrating that the mitochondriotoxic effects of curcumin are important for its anticancer activities.

The zinc-finger protein KCMF1 is overexpressed during pancreatic cancer development and downregulation of KCMF1 inhibits pancreatic cancer development in mice

Potassium channel modulatory factor 1 (KCMF1) was found upregulated in a differential screen in the metaplastic epithelium in the pancreas of transforming growth factor (TGF)-alpha transgenic mice. Expression analysis indicated broad overexpression in human cancer tissues. Therefore, we investigated the hypothesis that KCMF1 promotes metaplastic changes and tumor development. KCMF1 represents an evolutionarily highly conserved protein with a 95% identity between human and zebrafish. KCMF1 is expressed during embryonic development and in the majority of adult tissues investigated. Upregulation of nuclear KCMF1 expression is evident in preneoplastic lesions and in several epithelial malignancies, such as pancreatic cancer in mice and humans. In cell culture and in the chicken chorioallantoic membrane model, KCMF1 enhances proliferation, migration and invasion of HEK-293 and Panc1 cells. In crossbreeding experiments, KCMF1-knockdown gene trap mice showed a reduced number and size of premalignant lesions and absence of pancreatic cancer formation in TGF-alpha transgenic mice. This effect is related to the decreased expression of G1 to S cell-cycle regulators such as cyclin D and cyclin-dependent kinase (CDK) 4. Our data support the hypothesis that KCMF1 mediates pro-oncogenic functions in vitro and in vivo and downregulation of KCMF1 results in the inhibition of pancreatic cancer formation in mice. These effects are mediated through downregulation of cell-cycle control genes such as cyclin D and CDK4.

Gemcitabine induces the VMP1-mediated autophagy pathway to promote apoptotic death in human pancreatic cancer cells

BACKGROUND/AIM

Autophagy is a degradation process of cytoplasmic cellular constituents. We have described the vacuole membrane protein-1 (VMP1) whose expression triggers autophagy in mammalian cells. The aim of this study was to analyze the role of autophagy in human pancreatic cancer cell death.

METHODS/RESULTS

Here we show that gemcitabine, the standard chemotherapy for pancreatic cancer, induced autophagy in PANC-1 and MIAPaCa-2 cells, as evidenced by the accumulation of acidic vesicular organelles, the recruitment of microtubule-associated protein-1 light chain-3, and electron microscopy. In addition, gemcitabine treatment induced early expression of VMP1 in cancer cells. Gemcitabine also induced apoptosis detected by morphology, annexin V-positive cells, and cleavage of caspase-3. Surprisingly, 3-methyladenine, an autophagy inhibitor, decreased apoptosis in gemcitabine-treated cells, showing that autophagy leads to cancer cell apoptotic death. Finally, VMP1 knockdown decreased autophagy and apoptosis in gemcitabine-treated cancer cells.

CONCLUSIONS

The VMP1-autophagy pathway promotes apoptosis in pancreatic cancer cells and mediates gemcitabine-induced cytotoxicity. and IAP.

Fabrication of gold nanoparticles for targeted therapy in pancreatic cancer

The targeted delivery of a drug should result in enhanced therapeutic efficacy with low to minimal side effects. This is a widely accepted concept, but limited in application due to lack of available technologies and process of validation. Biomedical nanotechnology can play an important role in this respect. Biomedical nanotechnology is a burgeoning field with myriads of opportunities and possibilities for advancing medical science and disease treatment. Cancer nanotechnology (1-100 nm size range) is expected to change the very foundations of cancer treatment, diagnosis and detection. Nanomaterials, especially gold nanoparticles (AuNPs) have unique physico-chemical properties, such as ultra small size, large surface area to mass ratio, and high surface reactivity, presence of surface plasmon resonance (SPR) bands, biocompatibility and ease of surface functionalization. In this review, we will discuss how the unique physico-chemical properties of gold nanoparticles may be utilized for targeted drug delivery in pancreatic cancer leading to increased efficacy of traditional chemotherapeutics.

Plumbagin, isolated from Plumbago zeylanica, induces cell death through apoptosis in human pancreatic cancer cells

BACKGROUND AND AIMS

Pancreatic cancer is one of the most resistant malignancies. Several studies have indicated that plumbagin isolated from Plumbago zeylanica possesses anticancer activity. However, its antitumor effects against pancreatic cancer have not been explored.

METHODS

We investigated the effect of plumbagin on the growth of human pancreatic carcinoma cells and its possible underlying mechanisms.

RESULTS

Plumbagin inhibited the growth of Panc-1 and Bxpc-3 cells in a dose-dependent and time-dependent manner. Liu's staining and transmission electron microscopy demonstrated morphological changes resembling apoptosis in Panc-1 cells treated with plumbagin. The degree of apoptosis was assessed by measuring the proportions of sub-G(1), annexin V+/propidium iodide-, and terminal- deoxynucleotidyl-transferase-mediated-nick-end labeling (TUNEL)+ cells, and a significant increment in apoptotic cells was observed. Exposure to plumbagin caused the upregulation of Bax, a rapid decline in mitochondrial transmembrane potential, apoptosis-inducing factor overexpression in cytosol, and the cleavage of procaspase-9 and poly ADP-ribose polymerase. Activation of caspase-3, but not caspase-8, was evidenced by fluorometric substrate assay. Pretreatment with caspase inhibitors did not block plumbagin-induced apoptosis. Alternatively, it is possible that plumbagin downregulated phosphoinositide 3-kinase activity through a negative feedback mechanism. In an orthotopic pancreatic tumor model, plumbagin markedly inhibited the growth of Panc-1 xenografts without any significant effect on leukocyte counts or body weight.

CONCLUSION

Plumbagin may induce apoptosis in human pancreatic cancer cells primarily through the mitochondria-related pathway followed by both caspase-dependent and caspase-independent cascades. It indicates that plumbagin can be potentially developed as a novel therapeutic agent against pancreatic cancer.

BITC Sensitizes Pancreatic Adenocarcinomas to TRAIL-induced Apoptosis

Pancreatic adenocarcinoma is an aggressive cancer with a greater than 95% mortality rate and short survival after diagnosis. Chemotherapeutic resistance hinders successful treatment. This resistance is often associated with mutations in codon 12 of the K-Ras gene (K-Ras 12), which is present in over 90% of all pancreatic adenocarcinomas. Codon 12 mutations maintain Ras in a constitutively active state leading to continuous cellular proliferation. Our study determined if TRAIL resistance in pancreatic adenocarcinomas with K-Ras 12 mutations could be overcome by first sensitizing the cells with Benzyl isothiocyanate (BITC). BITC is a component of cruciferous vegetables and a cell cycle inhibitor. BxPC3, MiaPaCa2 and Panc-1 human pancreatic adenocarcinoma cell lines were examined for TRAIL resistance. Our studies show BITC induced TRAIL sensitization by dual activation of both the extrinsic and intrinsic apoptotic pathways.

Advances in pancreatic cancer detection

Pancreatic cancer represents a major challenge for research studies and clinical management. No specific tumor marker for the diagnosis of pancreatic cancer exists. Therefore, extensive genomic, transcriptomic, and proteomic studies are being developed to identify candidate markers for use in high-throughput systems capable of large cohort screening. Understandably, the complex pathophysiology of pancreatic cancer requires sensitive and specific biomarkers that can improve both early diagnosis and therapeutic monitoring. The lack of a single diagnostic marker makes it likely that only a panel of biomarkers is capable of providing the appropriate combination of high sensitivity and specificity. Biomarker discovery using novel technology can improve prognostic upgrading and pinpoint new molecular targets for innovative therapy.

EP300--a miRNA-regulated metastasis suppressor gene in ductal adenocarcinomas of the pancreas

Genetic and epigenetic alterations during development of pancreatic ductal adenocarcinomas (PDACs) are well known. This study investigates genetic and epigenetic data together with tumor biology to find specific alterations responsible for metastasis formation. Using 16 human PDAC cell lines in a murine orthotopic PDAC model, local infiltration and metastatic spread were assessed by standardized dissemination scores. The cell lines were further classified into 3 hierarchical groups according to their metastatic potential. Their mRNA and microRNA (miRNA) expression was profiled via mRNA-microarray as well as Taqman Low Density Array, and validated by single quantitative RT-PCR and Western blotting. In the highly metastatic group, a significant induction of EP300 targeting miRNAs miR-194 (fold change: 26.88), miR-200b (fold change: 61.65), miR-200c (fold change: 19.44) and miR-429 (fold change: 21.67) (p < 0.05) was detected. Corresponding to this, decreased expression of EP300 mRNA (p < 0.0001) and protein (p < 0.05) were detected in the highly metastatic PDAC cell lines with liver metastases compared to the nonmetastatic or marginally metastatic cell lines, while no correlation with local tumor growth was found. In conclusion, epigenetic alterations with upregulated EP300 targeting miRNAs miR-194, miR-200b, miR-200c and miR-429 are related to reduced EP300 mRNA and protein in PDAC. These results demonstrate that miRNAs might be able to modulate the expression of metastasis-specific suppressor genes and metastatic behavior in PDAC, suggesting diagnostic and therapeutic opportunities for EP300 and its targeting miRNAs in PDAC.

Context-dependent transformation of adult pancreatic cells by oncogenic K-Ras

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal human malignancies. To investigate the cellular origin(s) of this cancer, we determined the effect of PDAC-relevant gene mutations in distinct cell types of the adult pancreas. We show that a subpopulation of Pdx1-expressing cells is susceptible to oncogenic K-Ras-induced transformation without tissue injury, whereas insulin-expressing endocrine cells are completely refractory to transformation under these conditions. However, chronic pancreatic injury can alter their endocrine fate and allow them to serve as the cell of origin for exocrine neoplasia. These results suggest that one mechanism by which inflammation and/or tissue damage can promote neoplasia is by altering the fate of differentiated cells that are normally refractory to oncogenic stimulation.

Familial association of pancreatic cancer with other malignancies in Swedish families

Background:

The aim of this study was to characterise the familial association of pancreatic cancer with other malignancies.

Methods:

Relative risks (RRs) of pancreatic cancer according to family history of cancer were calculated using the updated Swedish Family-Cancer Database, which includes over 11.5 million individuals. Estimates were based on Poisson regression. RRs of tumours for individuals with a parental history of pancreatic cancer were also estimated.

Results:

The risk of pancreatic cancer was elevated in individuals with a parental history of cancers of the liver (RR 1.41; 95% CI 1.10–1.81), kidney (RR 1.37; 95% CI 1.06–1.76), lung (RR 1.50; 95% CI 1.27–1.79) and larynx (RR 1.98; 95% CI 1.19–3.28). Associations were also found between parental history of pancreatic cancer and cancers of the small intestine, colon, breast, lung, testis and cervix in offspring. There was an increased risk of pancreatic cancer associated with early-onset breast cancer in siblings.

Conclusion:

Pancreatic cancer aggregates in families with several types of cancer. Smoking may contribute to the familial aggregation of pancreatic and lung tumours, and the familial clustering of pancreatic and breast cancer could be partially explained by inherited mutations in the BRCA2 gene.

Up-regulation of integrin beta3 in radioresistant pancreatic cancer impairs adenovirus-mediated gene therapy

Adenovirus-mediated gene therapy is a promising approach for the treatment of pancreatic cancer. We previously reported that radiation enhanced adenovirus-mediated gene expression in pancreatic cancer, suggesting that adenoviral gene therapy might be more effective in radioresistant pancreatic cancer cells. In the present study, we compared the transduction efficiency of adenovirus-delivered genes in radiosensitive and radioresistant cells, and investigated the underlying mechanisms. We used an adenovirus expressing the hepatocyte growth factor antagonist, NK4 (Ad-NK4), as a representative gene therapy. We established two radioresistant human pancreatic cancer cell lines using fractionated irradiation. Radiosensitive and radioresistant pancreatic cancer cells were infected with Ad-NK4, and NK4 levels in the cells were measured. In order to investigate the mechanisms responsible for the differences in the transduction efficiency between these cells, we measured expression of the genes mediating adenovirus infection and endocytosis. The results revealed that NK4 levels in radioresistant cells were significantly lower (P < 0.01) than those in radiosensitive cells, although there were no significant differences in adenovirus uptake between radiosensitive cells and radioresistant cells. Integrin beta3 was up-regulated and the Coxsackie virus and adenovirus receptor was down-regulated in radioresistant cells, and inhibition of integrin beta3 promoted adenovirus gene transfer. These results suggest that inhibition of integrin beta3 in radioresistant pancreatic cancer cells could enhance adenovirus-mediated gene therapy.

Characterization of novel diaryl oxazole-based compounds as potential agents to treat pancreatic cancer

A series of diaryl- and fluorenone-based analogs of the lead compound UA-62784 [4-(5-(4-methoxyphenyl)oxazol-2-yl)-9H-fluoren-9-one] was synthesized with the intention of improving upon the selective cytotoxicity of UA-62784 against human pancreatic cancer cell lines with a deletion of the tumor suppressor gene deleted in pancreas cancer locus 4 (DPC-4, SMAD-4). Over 80 analogs were synthesized and tested for antitumor activity against pancreatic cancer (PC) cell lines (the PC series). Despite a structural relationship to UA-62784, which inhibits the mitotic kinesin centromere protein E (CENP-E), none of the analogs was selective for DPC-4-deleted pancreatic cancer cell lines. Furthermore, none of the analogs was a potent or selective inhibitor of four different mitotic kinesins (mitotic kinesin-5, CENP-E, mitotic kinesin-like protein-1, and mitotic centromere-associated kinesin). Therefore, other potential mechanisms of action were evaluated. A diaryl oxazole lead analog from this series, PC-046 [5-(4-methoxyphenyl)-2-(3-(3-methoxyphenyl)pyridin-4-yl) oxazole], was shown to potently inhibit several protein kinases that are overexpressed in human pancreatic cancers, including tyrosine receptor kinase B, interleukin-1 receptor-associated kinase-4, and proto-oncogene Pim-1. Cells exposed to PC-046 exhibit a cell cycle block in the S-phase followed by apoptotic death and necrosis. PC-046 effectively reduced MiaPaca-2 tumor growth in severe combined immunodeficiency mice by 80% compared with untreated controls. The plasma half-life was 7.5 h, and cytotoxic drug concentrations of >3 muM were achieved in vivo in mice. The diaryl oxazole series of compounds represent a new chemical class of anticancer agents that inhibit several types of cancer-relevant protein kinases.

Distinct gene mutation profiles among luminal-type and basal-type breast cancer cell lines

Breast cancer has for long been recognized as a highly diverse tumor group, but the underlying genetic basis has been elusive. Here, we report an extensive molecular characterization of a collection of 41 human breast cancer cell lines. Protein and gene expression analyses indicated that the collection of breast cancer cell lines has retained most, if not all, molecular characteristics that are typical for clinical breast cancers. Gene mutation analyses identified 146 oncogenic mutations among 27 well-known cancer genes, amounting to an average of 3.6 mutations per cell line. Mutations in genes from the p53, RB and PI3K tumor suppressor pathways were widespread among all breast cancer cell lines. Most important, we have identified two gene mutation profiles that are specifically associated with luminal-type and basal-type breast cancer cell lines. The luminal mutation profile involved E-cadherin and MAP2K4 gene mutations and amplifications of Cyclin D1, ERBB2 and HDM2, whereas the basal mutation profile involved BRCA1, RB1, RAS and BRAF gene mutations and deletions of p16 and p14ARF. These subtype-specific gene mutation profiles constitute a genetic basis for the heterogeneity observed among human breast cancers, providing clues for their underlying biology and providing guidance for targeted pharmacogenetic intervention in breast cancer patients.

Targeting the sphingolipid metabolism to defeat pancreatic cancer cell resistance to the chemotherapeutic gemcitabine drug

Defeating pancreatic cancer resistance to the chemotherapeutic drug gemcitabine remains a challenge to treat this deadly cancer. Targeting the sphingolipid metabolism for improving tumor chemosensitivity has recently emerged as a promising strategy. The fine balance between intracellular levels of the prosurvival sphingosine-1-phosphate (S1P) and the proapoptotic ceramide sphingolipids determines cell fate. Among enzymes that control this metabolism, sphingosine kinase-1 (SphK1), a tumor-associated protein overexpressed in many cancers, favors survival through S1P production, and inhibitors of SphK1 are used in ongoing clinical trials to sensitize epithelial ovarian and prostate cancer cells to various chemotherapeutic drugs. We here report that the cellular ceramide/S1P ratio is a critical biosensor for predicting pancreatic cancer cell sensitivity to gemcitabine. A low level of the ceramide/S1P ratio, associated with a high SphK1 activity, correlates with a robust intrinsic pancreatic cancer cell chemoresistance toward gemcitabine. Strikingly, increasing the ceramide/S1P ratio, by using pharmacologic (SphK1 inhibitor or ceramide analogue) or small interfering RNA-based approaches to up-regulate intracellular ceramide levels or reduce SphK1 activity, sensitized pancreatic cancer cells to gemcitabine. Conversely, decreasing the ceramide/S1P ratio, by up-regulating SphK1 activity, promoted gemcitabine resistance in these cells. Development of novel pharmacologic strategies targeting the sphingolipid metabolism might therefore represent an interesting promising approach, when combined with gemcitabine, to defeat pancreatic cancer chemoresistance to this drug.

Involvement of CD40 targeting miR-224 and miR-486 on the progression of pancreatic ductal adenocarcinomas

BACKGROUND

Genetic and epigenetic alterations during development of pancreatic ductal adenocarcinomas (PDAC) are well known. Genetic and epigenetic data were correlated with tumor biology to find specific alterations responsible for invasion and metastasis in pancreatic ductal adenocarcinomas.

METHODS

A total of 16 human PDAC cell lines were used in murine orthotopic PDAC models. By means of standardized dissemination scores, local invasion and metastatic spread were assessed. mRNA and microRNA expression were studied by microarray and TaqMan low-density array. Quantitative real-time-polymerase chain reaction and flow cytometry were used for expression validation.

RESULTS

CD40 was detected as a relevant target gene for differentially expressed miRNAs observed in highly invasive and metastatic PDAC only. A significant overexpression (P < .05) of CD40-related miRNAs miR-224 and miR-486 was detected in highly invasive and metastatic PDAC, whereas CD40 mRNA expression was not significantly altered. Instead, CD40 protein expression at cell surfaces of these highly invasive and metastatic PDAC was significantly reduced (P < .01).

CONCLUSIONS

Epigenetic alterations with upregulated CD40-targeting miR-224 and miR-486 are related to downregulated CD40 protein expression at cell surfaces in highly invasive and metastatic PDAC. Thus, miRNA-regulated CD40 expression seems to play an important role in progression of PDAC. These data suggest a diagnostic and therapeutic potential for CD40 and/or its targeting miRNAs in PDAC.

Role of RAF/MEK/ERK pathway, p-STAT-3 and Mcl-1 in sorafenib activity in human pancreatic cancer cell lines

Sorafenib is a multikinase inhibitor that has shown promising therapeutic results in different tumor histotypes, both as a single agent or in combination with other treatments. We analyzed the in vitro activity of sorafenib in pancreatic cancer, one of the most lethal and chemo-radio-resistant tumors, using four human pancreatic cancer cell lines (t3m4, Capan 1, Capan 2, and MiaPaca 2), characterized by different K-ras gene status and RAF/MEK/ERK profile. Sorafenib exerted a strong anti-proliferative effect independently of RAS/RAF/MEK/ERK and induced various degrees of apoptosis in the cell lines. The mechanisms involved were explored in detail in t3m4 and Capan 1, in which sorafenib induced the highest and lowest levels of apoptosis, respectively. In t3m4, the RAF/AKT/STAT-3 rather than the RAF/MEK/ERK pathway was involved, whereas in Capan 1 cells there was a strong decrease in pMEK and pERK which was not accompanied by an important reduction in RAF, AKT, and STAT-3 proteins or in their phosphorylation. Moreover, U0126-induced MEK inhibition did not induce apoptosis in any cell line, reinforcing the hypothesis of a MEK/ERK-independent mechanism of sorafenib activity. Mcl-1 appears to play a crucial role in sorafenib-induced apoptosis. In fact, both protein and mRNA were downregulated in t3m4 and upregulated in Capan 1, in which siRNA-induced silencing resulted in the same level of apoptosis as observed in t3m4. Our results show that sorafenib exerts anti-proliferative and pro-apoptotic activity in pancreatic cancer cells. Used singly or in combination with other drugs, it could therefore represent valid treatment for pancreatic cancer.