Pancreatic ductal adenocarcinoma (PDA) is a lethal disease with etiological association with cigarette smoking. Nicotine, an important component of cigarettes, exists at high concentrations in the bloodstream of smokers. Osteopontin (OPN) is a secreted phosphoprotein that confers on cancer cells a migratory phenotype and activates signaling pathways that induce cell survival, proliferation, invasion, and metastasis. Here, we investigated the potential molecular basis of nicotine’s role in PDA through studying its effect on OPN. Nicotine significantly (p<0.02) increased OPN mRNA and protein secretion in PDA cells through activation of the OPN gene promoter. The OPN mRNA induction was inhibited by the nicotinic acetylcholine receptor antagonist, mechamylamine. Further, the tyrosine kinase inhibitor genistein inhibited the nicotine-mediated induction of OPN, suggesting that mitogen activated protein kinase signaling mechanism is involved.
Nicotine activated the phosphorylation of ERK1/2, but not p38 or c-Jun NH2-terminal MAP kinases. Inhibition of ERK1/2 activation reduced the nicotine-induced OPN synthesis. Rats exposed to cigarette smoke showed a dose-dependent increase in pancreatic OPN that paralleled the rise of pancreatic and plasma nicotine levels. Analysis of cancer tissue from invasive PDA patients, the majority of whom were smokers, showed the presence of significant amounts of OPN in the malignant ducts and the surrounding pancreatic acini. Our data suggest that nicotine may contribute to PDA pathogenesis through upregulation of OPN. They provide the first insight into a nicotine-initiated signal transduction pathway that regulates OPN as a possible tumorigenic mechanism in PDA.
pancreatic cancer; nicotine; cigarette smoke; osteopontin
Deoxycytidine kinase (dCK) and human antigen R (HuR) have been associated with response to gemcitabine in small studies. The present study investigates the prognostic and predictive value of dCK and HuR expression levels for sensitivity to gemcitabine and 5-fluorouracil (5-FU) in a large phase III adjuvant trial with chemoradiation backbone in pancreatic ductal adenocarcinoma (PDA). The dCK and HuR expression levels were determined by immunohistochemistry on a tissue microarray of 165 resected PDAs from the Radiation Therapy Oncology Group (RTOG) 9704 trial. Association with overall survival (OS) and disease-free survival (DFS) status were analyzed using the log-rank test and the Cox proportional hazards model. Experiments with cultured PDA cells were performed to explore mechanisms linking dCK and HuR expression to drug sensitivity. dCK expression levels were associated with improved OS for all patients analyzed from RTOG 9704 (HR: 0.66, 95% CI [0.47–0.93], P = 0.015). In a subset analysis based on treatment arm, the effect was restricted to patients receiving 5-FU (HR: 0.53, 95% CI [0.33–0.85], P = 0.0078). Studies in cultured cells confirmed that dCK expression rendered cells more sensitive to 5-FU. HuR cytoplasmic expression was neither prognostic nor predictive of treatment response. Previous studies along with drug sensitivity and biochemical studies demonstrate that radiation interferes with HuR’s regulatory effects on dCK, and could account for the negative findings herein based on the clinical study design (i.e., inclusion of radiation). Finally, we demonstrate that 5-FU can increase HuR function by enhancing HuR translocation from the nucleus to the cytoplasm, similar to the effect of gemcitabine in PDA cells. For the first time, in the pre-treatment tumor samples, dCK and HuR cytoplasmic expression were strongly correlated (chi-square P = 0.015). This dual-institutional follow up study, in a multi-institutional PDA randomized clinical trial, observed that dCK expression levels were prognostic and had predictive value for sensitivity to 5-FU.
pancreatic cancer; gemcitabine; 5-fluorouracil; HuR; dCK
Pancreatic ductal adenocarcinoma (PDA) has a dismal prognosis and insights into both disease etiology and targeted intervention are needed. A total of 109 micro-dissected PDA cases were subjected to whole-exome sequencing. Microdissection enriches tumour cellularity and enhances mutation calling. Here we show that environmental stress and alterations in DNA repair genes associate with distinct mutation spectra. Copy number alterations target multiple tumour suppressive/oncogenic loci; however, amplification of MYC is uniquely associated with poor outcome and adenosquamous subtype. We identify multiple novel mutated genes in PDA, with select genes harbouring prognostic significance. RBM10 mutations associate with longer survival in spite of histological features of aggressive disease. KRAS mutations are observed in >90% of cases, but codon Q61 alleles are selectively associated with improved survival. Oncogenic BRAF mutations are mutually exclusive with KRAS and define sensitivity to vemurafenib in PDA models. High-frequency alterations in Wnt signalling, chromatin remodelling, Hedgehog signalling, DNA repair and cell cycle processes are observed. Together, these data delineate new genetic diversity of PDA and provide insights into prognostic determinants and therapeutic targets.
Diagnosis of pancreatic ductal adenocarcinoma (PDA) has poor long-term survival rates with limited therapy options. Here Witkiewicz et al. use microdissection and whole-exome sequencing to identify novel recurrent PDA mutations, highlighting the genetic diversity of this aggressive cancer.
HuR (ELAV1), an RNA binding protein abundant in cancer cells, primarily resides in the nucleus, but under specific stress (e.g., gemcitabine), HuR translocates to the cytoplasm where it tightly modulates the expression of mRNA survival cargo. Herein, we demonstrate for the first time that stressing pancreatic ductal adenocarcinoma (PDA) cells by treatment with DNA damaging anti-cancer agents (mitomycin C, oxaliplatin, cisplatin, carboplatin and a PARP-inhibitor) results in HuR’s translocation from the nucleus to the cytoplasm. Importantly, silencing HuR in PDA cells sensitized the cells to these agents, while overexpressing HuR caused resistance. HuR’s role in the efficacy of DNA damaging agents in PDA cells was, in part, attributed to the acute upregulation of WEE1 by HuR. WEE1, a mitotic inhibitor kinase, regulates the DNA damage repair pathway, and therapeutic inhibition of WEE1 in combination with chemotherapy is currently in early phase trials for the treatment of cancer. We validate WEE1 as a HuR target in vitro and in vivo by demonstrating: (1) direct binding of HuR to WEE1’s mRNA (a discrete 56-bp region residing in the 3’UTR), and (2) HuR siRNA silencing and overexpression directly affects the protein levels of WEE1, especially after DNA damage. HuR’s positive regulation of WEE1 increases γH2AX levels, induces Cdk1-phosphorylation and promotes cell cycle arrest at the G2/M transition. We describe a novel mechanism that PDA cells utilize to protect against DNA damage in which HuR post-transcriptionally regulates the expression and downstream function of WEE1 upon exposure to DNA damaging agents.
DNA damage; γH2AX; WEE1; HuR; Pancreatic ductal adenocarcinoma
PARP-1 is a nuclear protein that has important roles in maintenance of genomic integrity. During genotoxic stress, PARP-1 recruits to sites of DNA damage where PARP-1 domain architecture initiates catalytic activation and subsequent poly(ADP-ribose)-dependent DNA repair. PARP-1 inhibition is a promising new way to selectively target cancers harboring DNA repair deficiencies. However, current inhibitors target other PARPs raising important questions concerning long-term off-target effects. Here we propose a new strategy that targets PARP-1 allosteric regulation as a selective way of inhibiting PARP-1. We found that disruption of PARP-1 domain-domain contacts through mutagenesis held no cellular consequences on recruitment to DNA damage or a model system of transcriptional regulation, but prevented DNA-damage dependent catalytic activation. Further, PARP-1 mutant overexpression in a pancreatic cancer cell line (MIA PaCa-2) increased sensitivity to platinum-based anti-cancer agents. These results not only highlight the potential of a synergistic drug combination of allosteric PARP inhibitors with DNA damaging agents in genomically unstable cancer cells (regardless of homologous recombination status), but also signify important applications of selective PARP-1 inhibition. Lastly, the development of a high-throughput (HT) PARP-1 assay is described as a tool to promote discovery of novel PARP-1 selective inhibitors.
PARP; pancreatic cancer; allosteric; cisplatin; assay design
Cancer cell metabolism differs from normal cells, yet the regulatory mechanisms responsible for these differences are incompletely understood, particularly in response to acute changes in the tumor microenvironment. HuR, an RNA-binding protein, acts under acute stress to regulate core signaling pathways in cancer through post-transcriptional regulation of mRNA targets. We demonstrate that HuR regulates the metabolic phenotype in pancreatic cancer cells and is critical for survival under acute glucose deprivation. Using three pancreatic cancer cell line models, HuR-proficient cells demonstrated superior survival under glucose deprivation when compared with isogenic cells with siRNA-silencing of HuR expression (HuR-deficient cells). We found that HuR-proficient cells utilized less glucose, but produced greater lactate, as compared with HuR-deficient cells. Acute glucose deprivation was found to act as a potent stimulus for HuR translocation from the nucleus to the cytoplasm, where HuR stabilizes its mRNA targets. We performed a gene expression array on ribonucleoprotein-immunoprecipitated mRNAs bound to HuR and identified 11 novel HuR target transcripts that encode enzymes central to glucose metabolism. Three (GPI, PRPS2 and IDH1) were selected for validation studies, and confirmed as bona fide HuR targets. These findings establish HuR as a critical regulator of pancreatic cancer cell metabolism and survival under acute glucose deprivation. Further explorations into HuR’s role in cancer cell metabolism should uncover novel therapeutic targets that are critical for cancer cell survival in a metabolically compromised tumor microenvironment.
HuR; post-transcriptional gene regulation; cancer metabolism; pancreatic cancer
Pancreatic ductal adenocarcinoma (PDA) has the worst prognosis among cancers, mainly due to the high incidence of early metastases. RAN small GTPase (RAN) is a protein that plays physiological roles in the regulation of nuclear transport and microtubule spindle assembly. RAN was recently shown to mediate the invasive functions of the prometastatic protein osteopontin (OPN) in breast cancer cells. We and others have shown previously that high levels of OPN are present in PDA. In this study, we analyzed the expression and correlation of RAN with OPN in human pancreatic lesions, and explored their regulation in PDA cell lines.
Real time PCR was used to analyze RAN and OPN mRNA levels in PDA, adjacent non-malignant, and benign pancreatic tissues. Expression levels were correlated with survival and different clinicopathological parameters using different statistical methods. Transient transfection studies using OPN and RAN plasmids, and knockdown experiments using siRNA were used to examine their mutual regulation.
OPN and RAN levels highly correlated with each other (p<0.0001). OPN or RAN levels did not correlate with venous lymphatic invasion, diabetes, obesity, T stage, BMI, or survival. However, we found a significant association between RAN levels and perineural invasion (HR=0.79, 95% CI 0.59, 1.07; p=0.0378.). OPN and RAN colocalized in PDA tissues and cell lines. Increasing RAN expression in PDA cells induced OPN transcription and RAN silencing reduced total OPN levels. OPN did not have any significant effect on RAN transcription.
The high levels of RAN in PDA and its correlation with OPN and with perineural invasion suggest that RAN may contribute to PDA metastasis and progression through the induction of OPN. RAN’s role in the regulation of OPN in PDA is unique and could provide potential novel therapeutic strategies to combat PDA aggressiveness.
Pancreatic cancer; RAN; OPN
Apoptosis is one of the core signaling pathways disrupted in pancreatic ductal adenocarcinoma (PDA). Death receptor 5 (DR5) is a member of the tumor necrosis factor (TNF)-receptor superfamily that is expressed in cancer cells. Binding of TNF-related apoptosis-inducing ligand (TRAIL) to DR5 is a potent trigger of the extrinsic apoptotic pathway, and numerous clinical trials are based on DR5-targeted therapies for cancer, including PDA. Human antigen R (HuR), an RNA-binding protein, regulates a select number of transcripts under stress conditions. Here we report that HuR translocates from the nucleus to the cytoplasm of PDA cells upon treatment with a DR5 agonist. High doses of DR5 agonist induce cleavage of both HuR and caspase 8. HuR binds to DR5 mRNA at the 5′-untranslated region (UTR) in PDA cells in response to different cancer-associated stressors and subsequently represses DR5 protein expression; silencing HuR augments DR5 protein production by enabling its translation and thus enhances apoptosis. In PDA specimens (n = 53), negative HuR cytoplasmic expression correlated with elevated DR5 expression (odds ratio 16.1, p < 0.0001). Together, these data demonstrate a feedback mechanism elicited by HuR-mediated repression of the key apoptotic membrane protein DR5.
DR5; TRAIL; TRAIL-resistance; TRAILR2; apoptosis; pancreatic cancer; pancreatic ductal adenocarcinoma; post-transcriptional regulation
Gemcitabine is considered the standard first-line therapy for patients with advanced pancreatic cancer. More recent strategies have focused on improving the efficacy of gemcitabine by either improving the method of delivery or by combining gemcitabine with other non-cross-resistant chemotherapy agents or with small-molecule drugs. However, the clinical benefits, response rates, and duration of responses have been modest. Deoxycytidine kinase (dCK) is the rate-limiting enzyme involved in the metabolism of gemcitabine. The expression of dCK has been postulated to be correlative of gemcitabine resistance. We determined the relationship of dCK immunohistochemical protein expression and/or genetic status of dCK in a panel of human pancreatic cancer tissues and pancreatic cancer cell lines and determined the relationship of these variables to the clinical outcome of patients treated with gemcitabine. We report that dCK protein expression is expressed in the majority of pancreatic cancers analyzed (40 of 44 cases, 91%) and showed a range of labeling intensities ranging from 1+ (labeling weaker in intensity than normal lymphocytes present in same section) to 3+ (labeling greater in intensity than normal lymphocytes present in same section). When labeling intensity was compared with survival, low dCK expression (1+ labeling) was correlated with both overall survival (P < 0.009) and progression-free survival following gemcitabine treatment (P < 0.04). Low dCK labeling intensity was also significantly correlated with patient age (70.3 ± 8.1 versus 59.8 ± 7.4 years; P < 0.0006), suggesting that age-related methylation of the dCK gene may account in part for the observed differences. Sequencing of the entire dCK coding sequence in 17 cell lines and 9 patients’ cancer tissues with disease progression while on gemcitabine did not identify any mutations, suggesting that genetic alterations of dCK are not a common mechanism of resistance to gemcitabine for this tumor type. Moreover, dCK labeling showed similar patterns and intensities of labeling among matched pretreatment and post-treatment tissues. In summary, pretreatment levels of dCK protein are most correlated with overall survival following gemcitabine treatment and are stable even after resistance to gemcitabine is clinically documented.
Intraductal papillary mucinous neoplasm (IPMN) is an increasingly recognized pancreatic neoplasm characterized by excessive mucin secretion by ductal epithelial cells resulting in a cystic dilation of the pancreatic duct.
The objective of this study was to review Thomas Jefferson University’s experience and the literature to determine the significance of extra-pancreatic mucin when associated with an IPMN.
A retrospective analysis at our institution revealed only two cases of IPMN associated with extra-pancreatic mucin, which were classic IPMNs with rupture of the pancreatic duct and peritoneal mucin spillage. This specific finding is not previously described, although is assumed as five cases were reported in the literature with IPMN and mucin extension demonstrated by pseudomyxoma peritonei (PMP). We propose IPMN of the pancreas may be grossly compared to a mucocele of the appendix, as both are characterized by excessive secretion of mucin by ductal epithelial cells. A morbid complication of a mucocele is PMP. The presence of extra-pancreatic mucin with an IPMN could present a rare but important marker of the eventual seeding of tumor outside the primary IPMN. This has been documented with cases of iatrogenic spilling of pancreatic mucin, as well as multiple cases of IPMN associated with pseudomyxoma peritonei.
At this time, there is scant reporting and consensus for the treatment of IPMN with extra-pancreatic mucin.
Intraductal papillary mucinous neoplasm (IPMN); Extra-pancreatic mucin; Pancreatic cancer; Pseudomyxoma peritonei
Dorsal agenesis of the pancreas (DAP) is a rare congenital anomaly, with only 44 cases having been reported in the English literature since 1966.
Materials and Methods
A retrospective review of our IRB-approved pancreatic surgery database was performed from November 2005 to November 2010 searching for cases of DAP.
Disorders in the retinoic acid (Raldh) and hedgehog (Hh) signaling pathways, which appear to play a role in the development of DAP, have been implicated in other diseases of the pancreas such as pancreatic ductal adenocarcinoma (PDA) and nonalcoholic chronic calcific pancreatitis (NCCP).
In this report, we describe three cases of DAP in the setting of PDA, two of which include the third component of NCCP. We provide a discussion of the clinical features of this novel triad and address the molecular pathways that relate to these respective diseases.
Dorsal agenesis of the pancreas; Pancreatic ductal adenocarcinoma; Nonalcoholic chronic calcific pancreatitis
Pancreatic ductal adenocarcinoma (PDA) is a highly lethal disease in which a prominent desmoplastic reaction is a defining characteristic. Fibrillar collagens, such as collagen I and to a lesser extent, collagen III and V comprise the majority of this stromal fibrosis. Type VI collagen (COL6) forms a microfibrillar network associated with type I collagen fibrils. The expression of COL6 has been linked to inflammation and survival. Importantly, tumor-specific alternative splicing in COL6A3 has been identified in several cancers by genome exon arrays. We evaluated the expression and localization of COL6A3 in PDA and premalignant lesions and explored the presence of alternative splicing events.
We analyzed paired PDA-normal (n=18), IPMN (n=5), pancreatic cystadenoma (n=5), and eight PDA cell lines with RT-PCR, using unique primers that identify total COL6A3 gene and alternative splicing sites in several of its exons. Western blot analysis and immunohistochemistry were used to analyze the expression levels and localization of COL6A3 protein in the different lesions, and in two animal models of PDA.
COL6A3 protein levels were significantly upregulated in 77% of the paired PDA-adjacent tissue examined. COL6A3 was mainly present in the desmoplastic stroma of PDA, with high deposition around the malignant ducts and in between the sites of stromal fatty infiltration. Analysis of the COL6A3 splice variants showed tumor-specific consistent inclusion of exons 3 and 6 in 17 of the 18 (94%) paired PDA-adjacent tissues. Inclusion of exon 4 was exclusively tumor-specific, with barely detectable expression in the adjacent tissues. IPMN and pancreatic cystadenomas showed no expression of any of the examined exons. Total COL6A3 mRNA and exon 6 were identified in six PDA cell lines, but only two cell lines (MIA PACA-2 and ASPC-1) expressed exons 3 and 4. In both the xenograft and transgenic models of PDA, COL6A3 immunoreactivity was present in the stroma and some PDA cells.
We describe, for the first time, a dynamic process of tumor-specific alternative splicing in several exons of stromal COL6A3. Alternatively spliced proteins may contribute to the etiology or progression of cancer and may serve as markers for cancer diagnosis. Identification of COL6A3 isoforms as PDA-specific provides the basis for future studies to explore the oncogenic and diagnostic potential of these alternative splicing events.
pancreatic cancer; COL6A3; stroma; microenvironment
Reactive oxygen species (ROS) are mutagenic and may thereby promote cancer1. Normally, ROS levels are tightly controlled by an inducible antioxidant program that responds to cellular stressors and is predominantly regulated by the transcription factor Nrf2 and its repressor protein Keap12-5. In contrast to the acute physiological regulation of Nrf2, in neoplasia there is evidence for increased basal activation of Nrf2. Indeed, somatic mutations that disrupt the Nrf2-Keap1 interaction to stabilize Nrf2 and increase the constitutive transcription of Nrf2 target genes were recently identified, suggesting that enhanced ROS detoxification and additional Nrf2 functions may in fact be pro-tumorigenic6. Here, we investigated ROS metabolism in primary murine cells following the expression of endogenous oncogenic alleles of K-Ras, B-Raf and Myc, and find that ROS are actively suppressed by these oncogenes. K-RasG12D, B-RafV619E and MycERT2 each increased the transcription of Nrf2 to stably elevate the basal Nrf2 antioxidant program and thereby lower intracellular ROS and confer a more reduced intracellular environment. Oncogene-directed increased expression of Nrf2 is a novel mechanism for the activation of the Nrf2 antioxidant program, and is evident in primary cells and tissues of mice expressing K-RasG12D and B-RafV619E, and in human pancreatic cancer. Furthermore, genetic targeting of the Nrf2 pathway impairs K-RasG12D-induced proliferation and tumorigenesis in vivo. Thus, the Nrf2 antioxidant and cellular detoxification program represents a previously unappreciated mediator of oncogenesis.
RRM1 and ERCC1 overexpression has been extensively investigated as potential predictive markers of tumor sensitivity to conventional chemotherapy agents, most thoroughly in lung cancer. However, data in pancreatic cancer are scarce.
We investigated the mRNA and protein expression of ERCC1 and RRM1 by RT-PCR and immunohistochemistry (IHC) in formalin-fixed, paraffin-embedded pancreatic ductal carcinoma (PDA) tissues. The primary outcome investigated was the association between RRM1 and ERCC1 expression and overall survival (OS) or disease-free survival (DFS).
A total of 94 patients with resected PDA were included in this study. Most of them (87%) received gemcitabine based chemotherapy. Data for OS analysis was available in all cases but only 68% had enough information to estimate DFS. IHC analysis revealed information for 99% (93/94) and 100% of the cases for RRM1 and ERCC1 expression respectively. However, PCR data interpretation was possible in only 49 (52%) and 79 (84%) cases respectively. There was no significant association between high or low expression of either RRM1 or ERCC1, detected by IHC and OS (14.4 vs. 19.9 months; P = 0.5 and 17.1 vs. 19.9; P = 0.83 respectively) or PCR and OS (48.0 vs. 24.1 months; P = 0.21 and 22.0 vs. 16.0 months; P = 0.39 respectively). Similar results were obtained for DFS.
RRM1 and ERCC1 expression does not seem to have a clear predictive or prognostic value in pancreatic cancer. Our data raise some questions regarding the real clinical and practical significance of analyzing these molecules as predictors of outcomes.
Preclinical data support further investigation of ascorbic acid in pancreatic cancer. There are currently insufficient safety data in human subjects, particularly when ascorbic acid is combined with chemotherapy.
Methods and Findings
14 subjects with metastatic stage IV pancreatic cancer were recruited to receive an eight week cycle of intravenous ascorbic acid (three infusions per week), using a dose escalation design, along with standard treatment of gemcitabine and erlotinib. Of 14 recruited subjects enrolled, nine completed the study (three in each dosage tier). There were fifteen non-serious adverse events and eight serious adverse events, all likely related to progression of disease or treatment with gemcitabine or erlotinib. Applying RECIST 1.0 criteria, seven of the nine subjects had stable disease while the other two had progressive disease.
These initial safety data do not reveal increased toxicity with the addition of ascorbic acid to gemcitabine and erlotinib in pancreatic cancer patients. This, combined with the observed response to treatment, suggests the need for a phase II study of longer duration.
Pancreatic cancer is the fourth leading cause of cancer-related deaths in this country, and there is currently no effective targeted treatment for this deadly disease. A dire need exists to rapidly translate our molecular understanding of this devastating disease into effective, novel therapeutic options. Mesothelin is a candidate target protein shown by a number of laboratories to be specifically overexpressed in pancreatic cancers and not in the adjacent normal tissue. Translational investigations have shown promising results using this molecule as a therapeutic target (e.g., vaccine strategies). In addition, the mesothelin promoter has been cloned and dissected and can therefore be used as a vehicle for regulating expression of DNA sequences. Using a novel, proven, biodegradable nanoparticulate system, we sought to target mesothelin-expressing pancreatic cancer cells with a potent suicide gene, diphtheria toxin-A (DT-A). We first confirmed reports that a majority of pancreatic cancer cell lines and resected pancreatic ductal adenocarcinoma specimens overexpressed mesothelin at the mRNA and protein levels. High mesothelin-expressing pancreatic cancer cell lines produced more luciferase than cell lines with undetectable mesothelin expression when transfected with a luciferase sequence under the regulation of the mesothelin promoter. We achieved dramatic inhibition of protein translation (>95%) in mesothelin-expressing pancreatic cancer cell lines when DT-A DNA, driven by the mesothelin promoter, was delivered to pancreatic cancer cells. We show that this inhibition effectively targets the death of pancreatic cancer cells that overexpress mesothelin. The work presented here provides evidence that this strategy will work in pre-clinical mouse pancreatic cancer models, and suggests that such a strategy will work in the clinical setting against the majority of pancreatic tumors, most of which overexpress mesothelin.
nanoparticles; mesothelin; pancreatic cancer; targeted DNA delivery
Gene therapy protocols for the treatment of cancer often employ gene promoter sequences that are known to be overexpressed in specific tumor cell types relative to normal cells. These promoters, while specific, are often weakly active. It would be desirable to increase the activity of such promoters, while at the same time retain specificity, so that the therapeutic gene is more robustly expressed. Using a luciferase reporter DNA construct in both in vitro cell transfection assays and in vivo mouse tumor models, we have determined that in the absence of any other DNA sequence, a previously identified 18-base pair enhancer sequence called CanScript, lying upstream of the MSLN gene, has ∼25% of the promoter activity of CAG, a very strong non-specific promoter/enhancer, in tumor cells in which MSLN is highly expressed. Furthermore, tandem repeat copies of CanScript enhance transcription in a dose-dependent manner and, when coupled with promoter sequences that are active in tumor cells, increase promoter activity. These findings suggest that the incorporation of CanScript into gene constructs may have application in enhancing activity of promoters used in cancer-targeting gene therapy strategies, thereby improving therapeutic efficacy.
targeted gene therapy; mesothelin; canscript; gene promoter
Background/Aims. Pancreatic ductal adenocarcinoma (PDA) has etiological association with chronic inflammation. Elevated circulating levels of inflammatory mediators, such as monocyte chemoattractant protein-1 (MCP-1), are found in obese individuals. We hypothesized that serum MCP-1 levels are elevated in obese PDA patients. Methods. ELISA was used to analyze MCP-1 serum levels in PDA (n = 62) and intraductal papillary mucinous neoplasms (IPMN) (n = 27). Recursive partitioning statistical analysis investigated the relationship between log MCP-1 and clinicopathological parameters. Results. Log MCP-1 values were significantly (P < 0.05) elevated in patients with BMI ≥ 37.5. In patients with BMI < 37.5, average log MCP-1 values were significantly elevated in PDA patients when compared to IPMN patients. Within the IPMN group, higher log MCP-1 levels correlated with increased age. Recursive partitioning analysis of IPMN versus PDA revealed a strategy of predicting characteristics of patients who are more likely to have cancer. This strategy utilizes log MCP-1 as the primary factor and also utilizes smoking status, gender, and age. Conclusion. MCP-1 is a promising biomarker in pancreatic cancer. The potential of using MCP-1 to distinguish PDA from IPMN patients must be studied in larger populations to validate and demonstrate its eventual clinical utility.
We recently discovered that the enzyme indoleamine 2,3-dioxygenase (IDO) is overexpressed in primary pancreatic ductal adenocarcinomas (PDA) and in lymph node metastases (J Am Coll Surg. 5:849-54: 2008). IDO2 is a recently discovered relative of IDO that has unique signaling properties (Cancer Res. 67:7082-7087: 2007). Notably, the IDO2 gene has two functional polymorphisms commonly found in human populations that abolish its enzymatic activity (R235W and Y359STOP). Both IDO and IDO2 repress the immune system and we hypothesize that expression of these enzymes in PDA may help cancer cells evade immune detection.
Based on evidence that the IDO2 may be a preferential target of D-1-methyl-tryptophan (1-MT), a clinical lead inhibitor of IDO currently being evaluated in Phase I trials, we sequenced IDO2 in 36 resected PDAs and evaluated its expression in relation to the two known genetic polymorphisms.
In our patient cohort, we found that 58% (21/36) of the cases were heterozygous for the R235W polymorphism; 28% (10/36) were homozygous wild-type; and only 14% (5/36) were homozygous for the functionally inactive polymorphism. Interestingly, IDO2 had a homozygous wild-type configuration in two pancreatic cancer cell lines whereas one cell line (MiaPaCa2 cells) was homozygous for the R235W polymorphism. As for the Y359STOP polymorphism (seen in the cell line Hs766T), we found that 27% (10/36) of the cases were heterozygous, 62% (22/36) were homozygous wild-type, and only 11% (4/36) were homozygous for this functionally inactive allele. Ruling out the possibility of compound polymorphic variants, we estimated 75% of our resected patient cohort had an active IDO2 enzyme with a conservative estimate that 58% of the patients had at least one functional allele. In immunohistochemical analyses, we found that IDO2 was equally overexpressed in pancreatic cancer tissue from each genetially polymorphic subgroup. We also detected IDO2 protein expression in the genetically distinct pancreatic cancer cell lines after exposure with IFN-γ, establishing that even functionally polymorphic IDO2 sequences can generate IDO2 protein.
These are the first data to report IDO2 expression in PDA and indicate that IDO2 genetic polymorphisms do not negate IFN-γ-inducible protein expression. IDO2 genotyping and expression analysis of our PDA patient tissue bank and cell lines show that IDO2 is active and expressed in a majority of PDA patients. Taken together, these data strongly suggest that the clinical lead compound D-1-MT acting through IDO2 might be useful in treatment of PDA, either alone or in combination with other anti-tumor modalities.
Cigarette smoke and nicotine are among the leading environmental risk factors for developing pancreatic ductal adenocarcinoma (PDA). We showed recently that nicotine induces osteopontin (OPN), a protein that plays critical roles in inflammation and tumor metastasis. We identified an OPN isoform, OPNc, that is selectively inducible by nicotine and highly expressed in PDA tissue from smokers. In this study, we explored the potential proinflammatory role of nicotine in PDA through studying its effect on the expression of monocyte chemoattractant protein- (MCP)-1 and evaluated the role of OPN in mediating these effects.
MCP-1 mRNA and protein in PDA cells treated with or without nicotine (3–300 nM) or OPN (0.15–15 nM) were analyzed by real time PCR and ELISA. Luciferase-labeled promoter studies evaluated the effects of nicotine and OPN on MCP-1 transcription. Intracellular and tissue colocalization of OPN and MCP-1 were examined by immunofluorescence and immunohistochemistry.
Nicotine treatment significantly increased MCP-1 expression in PDA cells. Interestingly, blocking OPN with siRNA or OPN antibody abolished these effects. Transient transfection of the OPNc gene in PDA cells or their treatment with recombinant OPN protein significantly (P<0.05) increased MCP-1 mRNA and protein and induced its promoter activity. MCP-1 was found in 60% of invasive PDA lesions, of which 66% were smokers. MCP-1 colocalized with OPN in PDA cells and in the malignant ducts, and correlated well with higher expression levels of OPN in the tissue from patients with invasive PDA.
Our data suggest that cigarette smoking and nicotine may contribute to PDA inflammation through inducing MCP-1 and provide a novel insight into a unique role for OPN in mediating these effects.
pancreatic cancer; nicotine; osteopontin; monocyte chemoattractant protein-1
Surgical resection provides the only possibility of cure for pancreas cancer. A standard adjuvant approach has not been established. We tested the safety and efficacy of a granulocyte-macrophage colony-stimulating factor (GM-CSF)-based immunotherapy administered in patients with resected pancreatic adenocarcinoma.
Patients and Methods
A single institution phase II study of 60 patients with resected pancreatic adenocarcinoma was performed. Each immunotherapy treatment consisted of a total of 5 × 108 GM-CSF-secreting cells distributed equally among 3 lymph node regions. The first immunotherapy treatment was administered 8 to 10 weeks after surgical resection. Subsequently, patients received 5-FU based chemoradiation. Patients who remained disease-free after completion of chemoradiotherapy received treatments 2 to 4, each 1 month apart. A fifth and final booster was administered 6 months after the fourth immunotherapy. The primary endpoint was disease free survival and secondary endpoints were overall survival and toxicity, and the induction of mesothelin-specific T cell responses.
The median disease-free survival is 17.3 months (95% CI, 14.6–22.8) with median survival of 24.8 months (95% CI, 21.2–31.6). The administration of immunotherapy was well tolerated. In addition, the postimmunotherapy induction of mesothelin-specific CD8+ T cells in HLA-A1+ and HLA-A2+ patients correlates with disease-free survival.
An immunotherapy approach integrated with chemoradiation is safe and demonstrates an overall survival that compares favorably with published data for resected pancreas cancer. These data suggest additional boost immunotherapies given at regular intervals beyond 1 year postsurgery should be tested in future studies, and provide the rationale for conducting a multicenter phase II study.
Thymidylate synthase is a target of 5-fluoruracil, a pyrimidine analog used to treat gastrointestinal and other cancers. The 5-fluorouracil metabolite, fluoro-deoxyuridine monophosphate, forms a ternary complex with thymidylate synthase and 5,10-methylene tetrahydrofolate. The purpose of this study was to evaluate the time-honored connection between thymidylate synthase and 5-fluorouracil. From our literature search spanning reports from 1995 to 2007 published in journals having an impact factor greater than two, we stratified the tumors within each article, according to low versus high thymidylate synthase expression. These groups were subdivided into responders, stable disease or disease progression. The relationship between thymidylate synthase expression and 5-fluorouracil response was analyzed for the overall group, as well as for subsets. Overall, the literature supported an approximately two-fold inverse relationship between thymidylate synthase expression and response to 5-fluoruracil. We found no change in the trend for a relationship between thymidylate synthase and 5-fluorouracil when the literature was stratified by date of publication, impact factor of the journal in which the report was published, or substrate (mRNA versus protein) for measuring thymidylate synthase expression. Of note, there is no significant change in the trend when comparing 5-fluorouracil treatment alone or in combination with leucovorin. We found a decline of this trend when certain chemotherapeutics were used in combination with 5-fluorouracil. In sum, the connection between thymidylate synthase expression and patient response to 5-fluorouracil does not satisfy expectations for an effective drug-target relationship; and thus, studies of the thymidylate synthase tandem repeat status might only be clinically valuable in regards to patient toxicity. Thus, we question the reliability of thymidylate synthase expression as a clinical predictor of 5-fluorouracil response. Future research could perhaps be directed towards alternate targets and metabolites of 5-fluorouracil, in an effort to find a clinically relevant biomarker panel for response and to optimize fluoropyrimidine-based therapy.
thymidylate synthase; 5-fluorouracil; clinical response; pharmacogenomics; chemotherapeutic resistance; pharamocogenetic window; resistance; sensitivity
The expression of protein phosphatase 32 (PP32, ANP32A) is low in poorly differentiated pancreatic cancers and is linked to the levels of HuR (ELAV1), a predictive marker for gemcitabine response. In pancreatic cancer cells, exogenous overexpression of pp32 inhibited cell growth, supporting its long-recognized role as a tumor suppressor in pancreatic cancer. In chemotherapeutic sensitivity screening assays, cells overexpressing pp32 were selectively resistant to the nucleoside analogs gemcitabine and cytarabine (ARA-C), but were sensitized to 5-fluorouracil; conversely, silencing pp32 in pancreatic cancer cells enhanced gemcitabine sensitivity. The cytoplasmic levels of pp32 increased after cancer cells are treated with certain stressors, including gemcitabine. pp32 overexpression reduced the association of HuR with the mRNA encoding the gemcitabine-metabolizing enzyme deoxycytidine kinase (dCK), causing a significant reduction in dCK protein levels. Similarly, ectopic pp32 expression caused a reduction in HuR binding of mRNAs encoding tumor-promoting proteins (e.g., VEGF and HuR), while silencing pp32 dramatically enhanced the binding of these mRNA targets. Low pp32 nuclear expression correlated with high-grade tumors and the presence of lymph node metastasis, as compared to patients' tumors with high nuclear pp32 expression. Although pp32 expression levels did not enhance the predictive power of cytoplasmic HuR status, nuclear pp32 levels and cytoplasmic HuR levels associated significantly in patient samples. Thus, we provide novel evidence that the tumor suppressor function of pp32 can be attributed to its ability to disrupt HuR binding to target mRNAs encoding key proteins for cancer cell survival and drug efficacy.
Osteopontin (OPN) is a secreted phosphoprotein that confers on cancer cells a migratory phenotype. We showed recently that nicotine, a major risk factor in pancreatic ductal adenocarcinoma (PDA), increases OPN expression in PDA cells. An OPN splice variant, OPNc, supports anchorage independence and maybe the most potent OPN isoform to convey metastatic behavior. In this study, we tested the effect of nicotine on OPNc expression, and analyzed the correlation between total OPN/OPNc levels and patients’ smoking history.
Real time PCR and UV-light-illumination of ethidium-bromide staining were used to examine the mRNA expression in tissue and in PDA cells treated with or without nicotine (3-300 nM). OPN and OPNc were localized by immunohisotchemistry, and ELISA was used to analyze OPN serum levels.
Nicotine treatment of PDA cells selectively induced denovo expression of OPNc. OPNc was found in 87% of invasive PDA lesions, of which 73% were smokers. The levels of OPNc correlated well with higher expression levels of total OPN in the tissue and serum from patients with invasive PDA.
Our data suggest that smoking and nicotine may contribute to PDA metastatic potential through promoting OPNc expression. Although the direct role of OPNc in PDA progression is not defined, OPNc may have value as a diagnostic and prognostic marker, especially in invasive PDA.
pancreatic cancer; nicotine; osteopontin