Gene therapy developments for pancreatic cancer

Long-term survivors after pancreatectomy for cancer: the TNM classification is outdated

BACKGROUND

According to knowledge, patients with resectable pancreatic adenocarcinoma (PA) should receive adjuvant gemcitabine-based chemotherapy. Thus, the tumour node metastasis (TNM) classification is not used to determine post-operative treatment but rather only to establish patient prognosis. However, the TNM classification does not include strong factors influencing survival, such as perineural invasion or margin status. This study compared the survival of patients with very similar tumours.

METHODS

From 1997 to 2007, 118 patients underwent pancreatectomy for PA. Twenty-six patients (22%) had long-term survival (>5 years; LTS group). According to the major prognostic factors of PA, we matched (1:1) patients in the LTS group with patients who did not have long-term survival (<5 years; control group).

RESULTS

Surprisingly, we did not have any difficulty identifying patients to include in the control group. Consequently, no differences were noted between patients of the LTS group when compared with patients of the control group according to major prognostic factors and the TNM classification. Three patients (12%) in the LTS group had positive margin status, and two patients (8%) had positive lymph node status. Unsurprisingly, the median survival for the control group versus the LTS group was 16 months versus not reached (P < 0.01).

CONCLUSION

The lack of difficulty in matching the two groups confirmed that patients of the LTS group did not have an exclusive tumour pattern. TNM classification is outdated because it did not influence adjuvant therapies and did not include two crucial factors: tumour biology and tumour response to chemo/radio therapies.

Inhibition of cell proliferation and increase of chemosensitivity by simultaneous knockdown of XIAP and survivin in pancreatic carcinoma cells

At present, classic therapies provide limited benefits to the survival of patients with pancreatic cancer. However, clinically available gene therapy strategies have not been well established. This study investigates the effect of shRNA-mediated inhibition of XIAP and survivin expression on the proliferation, apoptosis, and chemosensitivity of pancreatic cancer cells. Stable inhibition of XIAP and survivin expression in SW1990 and Panc-1 pancreatic cancer cells was established by lentivirus-carried shRNAs. The mRNA and protein expression of XIAP and survivin were detected by real-time PCR and Western blot, respectively. Cell proliferation was measured by MTT assay, and apoptosis was detected by caspase-3/7 activity and Hoechst33342 staining. The lentivirus-carried shRNA significantly inhibited XIAP and survivin expression. Simultaneous inhibition of XIAP and survivin expression in pancreatic cells significantly reduced cell proliferation, increased caspase-3/7 activity, and increased cell sensitization to 5-FU and gemcitabine treatments compared to inhibition of XIAP or survivin expression alone. However, simultaneous silencing of XIAP and survivin showed no significant difference in inducing cell apoptosis compared to silencing of XIAP or survivin expression alone. Simultaneous inhibition of XIAP and survivin expression may be an effective strategy for gene therapy of pancreatic cancer.

The challenge of pancreatic cancer therapy and novel treatment strategy using engineered mesenchymal stem cells

Mesenchymal stem cells (MSCs) have attracted significant attention in cancer research as a result of their accessibility, tumor-oriented homing capacity, and the feasibility of auto-transplantation. This review provides a comprehensive overview of current challenges in pancreatic cancer therapy, and we propose a novel strategy for using MSCs as means of delivering anticancer genes to the site of pancreas. We aim to provide a practical platform for the development of MSC-based therapy for pancreatic cancer.

Enhanced CRAd activity using enhancer motifs driven by a nucleosome positioning sequence

Cancer development involves changes driven by the epigenetic machinery, including nucleosome positioning. Recently, the concept that adenoviral replication may be driven by tumor specific promoters (TSPs) gained support, and several conditionally replicative adenoviruses (CRAd) exhibited therapeutic efficacy in clinical trials. Here, we show for the first time that placing a nucleosome positioning sequence (NPS) upstream of a TSP combined with Wnt-responsive motifs (pART enhancer) enhanced the TSP transcriptional activity and increased the lytic activity of a CRAd. pART enhanced the transcriptional activity of the gastrointestinal cancer (GIC)-specific REG1A promoter (REG1A-pr); moreover, pART also increased the in vitro lytic activity of a CRAd whose replication was driven by REG1A-Pr. The pART enhancer effect in vitro and in vivo was strictly dependent on the presence of the NPS. Indeed, deletion of the NPS was strongly deleterious for the in vivo antitumor efficacy of the CRAd on orthotopically established pancreatic xenografts. pART also enhanced the specific activity of other heterologous promoters; moreover, the NPS was also able to enhance the responsiveness of hypoxia- and NFκB-response elements. We conclude that NPS could be useful for gene therapy approaches in cancer as well as other diseases.

In vivo gene transfer targeting in pancreatic adenocarcinoma with cell surface antigens

BACKGROUND

Pancreatic ductal adenocarcinoma is a deadly malignancy resistant to current therapies. It is critical to test new strategies, including tumor-targeted delivery of therapeutic agents. This study tested the possibility to target the transfer of a suicide gene in tumor cells using an oncotropic lentiviral vector.

RESULTS

Three cell surface markers were evaluated to target the transduction of cells by lentiviruses pseudotyped with a modified glycoprotein from Sindbis virus. Only Mucin-4 and the Claudin-18 proteins were found efficient for targeted lentivirus transductions in vitro. In subcutaneous xenografts of human pancreatic cancer cells models, Claudin-18 failed to achieve efficient gene transfer but Mucin-4 was found very potent. Human pancreatic tumor cells were modified to express a fluorescent protein detectable in live animals by bioimaging, to perform a direct non invasive and costless follow up of the tumor growth. Targeted gene transfer of a bicistronic transgene bearing a luciferase gene and the herpes simplex virus thymidine kinase gene into orthotopic grafts was carried out with Mucin-4 oncotropic lentiviruses. By contrast to the broad tropism VSV-G carrying lentivirus, this oncotropic lentivirus was found to transduce specifically tumor cells, sparing normal pancreatic cells in vivo. Transduced cells disappeared after ganciclovir treatment while the orthotopic tumor growth was slowed down.

CONCLUSION

This work considered for the first time three aspect of pancreatic adenocarcinoma targeted therapy. First, lentiviral transduction of human pancreatic tumor cells was possible when cells were grafted orthotopically. Second, we used a system targeting the tumor cells with cell surface antigens and sparing the normal cells. Finally, the TK/GCV anticancer system showed promising results in vivo. Importantly, the approach presented here appeared to be a safer, much more specific and an as efficient way to perform gene delivery in pancreatic tumors, in comparison with a broad tropism lentivirus. This study will be useful in future designing of targeted therapies for pancreatic cancer.

Current knowledge on pancreatic cancer

Pancreatic cancer is the fourth leading cause of cancer death with a median survival of 6 months and a dismal 5-year survival rate of 3-5%. The development and progression of pancreatic cancer are caused by the activation of oncogenes, the inactivation of tumor suppressor genes, and the deregulation of many signaling pathways. Therefore, the strategies targeting these molecules as well as their downstream signaling could be promising for the prevention and treatment of pancreatic cancer. However, although targeted therapies for pancreatic cancer have yielded encouraging results in vitro and in animal models, these findings have not been translated into improved outcomes in clinical trials. This failure is due to an incomplete understanding of the biology of pancreatic cancer and to the selection of poorly efficient or imperfectly targeted agents. In this review, we will critically present the current knowledge regarding the molecular, biochemical, clinical, and therapeutic aspects of pancreatic cancer.

Mechanism of interaction of small transcription inhibitors with DNA in the context of chromatin and telomere

Small molecules from natural and synthetic sources have long been employed as human drugs. The transcription inhibitory potential of one class of these molecules has paved their use as anticancer drugs. The principal mode of action of these molecules is via reversible interaction with genomic DNA, double and multiple stranded. In this article we have revisited the mechanism of the interaction in the context of chromatin and telomere. The established modes of association of these molecules with double helical DNA provide a preliminary mechanism of their transcription inhibitory potential, but the scenario assumes a different dimension when the genomic DNA is associated with proteins in the transcription apparatus of both prokaryotic and eukaryotic organisms. We have discussed this altered scenario as a prelude to understand the chemical biology of their action in the cell. For the telomeric quadruplex DNA, we have reviewed the mechanism of their association with the quadruplex and resultant cellular consequence.

Pancreatic cancer: pathobiology, treatment options, and drug delivery

Pancreatic cancer is the fourth leading cause of cancer-related deaths in the USA. The high mortality rate is partly due to lack of effective treatments. This review summarizes the pathobiology and current treatment options for pancreatic cancer. Moreover, the review discusses the opportunities of developing novel therapies for pancreatic cancer provided by the progress in understanding the genetic mutations, tumor microenvironment, cancer stem cells, and drug delivery.

Anti-viral state segregates two molecular phenotypes of pancreatic adenocarcinoma: potential relevance for adenoviral gene therapy

Background

Pancreatic ductal adenocarcinoma (PDAC) remains a leading cause of cancer mortality for which novel gene therapy approaches relying on tumor-tropic adenoviruses are being tested.

Methods

We obtained the global transcriptional profiling of primary PDAC using RNA from eight xenografted primary PDAC, three primary PDAC bulk tissues, three chronic pancreatitis and three normal pancreatic tissues. The Affymetrix GeneChip HG-U133A was used. The results of the expression profiles were validated applying immunohistochemical and western blot analysis on a set of 34 primary PDAC and 10 established PDAC cell lines. Permissivity to viral vectors used for gene therapy, Adenovirus 5 and Adeno-Associated Viruses 5 and 6, was assessed on PDAC cell lines.

Results

The analysis of the expression profiles allowed the identification of two clearly distinguishable phenotypes according to the expression of interferon-stimulated genes. The two phenotypes could be readily recognized by immunohistochemical detection of the Myxovirus-resistance A protein, whose expression reflects the activation of interferon dependent pathways. The two molecular phenotypes discovered in primary carcinomas were also observed among established pancreatic adenocarcinoma cell lines, suggesting that these phenotypes are an intrinsic characteristic of cancer cells independent of their interaction with the host's microenvironment. The two pancreatic cancer phenotypes are characterized by different permissivity to viral vectors used for gene therapy, as cell lines expressing interferon stimulated genes resisted to Adenovirus 5 mediated lysis in vitro. Similar results were observed when cells were transduced with Adeno-Associated Viruses 5 and 6.

Conclusion

Our study identified two molecular phenotypes of pancreatic cancer, characterized by a differential expression of interferon-stimulated genes and easily recognized by the expression of the Myxovirus-resistance A protein. We suggest that the detection of these two phenotypes might help the selection of patients enrolled in virally-mediated gene therapy trials.

RNA inhibition, microRNAs, and new therapeutic agents for cancer treatment

Over the past few years, molecular oncology research has revealed that abnormalities in both protein-coding genes (PCGs) and noncoding RNAs (ncRNAs) can be identified in tumors and that the interplay between PCGs and ncRNAs is causally involved in the initiation, progression, and metastases of human cancers. MicroRNAs (miRNAs), which are among the most studied ncRNAs, are small 19- to 25-nucleotide genes involved in the regulation of PCGs and other ncRNAs. With the recent findings of miRNAs' involvement in cancer, RNA inhibition can be used to treat cancer patients in two ways: (1) by using RNA or DNA molecules as therapeutic drugs against messenger RNA of genes involved in the pathogenesis of cancers and (2) by directly targeting ncRNAs that participate in cancer pathogenesis. In this review, we focus on the possible use of miRNAs or compounds interacting with miRNAs as new therapeutic agents in cancer patients.

Using lentiviral vectors for efficient pancreatic cancer gene therapy

Pancreatic cancer (PC) remains a life-threatening disease. Efficient therapeutic gene delivery to PC-derived cells continues to present challenges. We used self-inactivated lentiviral vectors to transduce PC-derived cells in vitro and in vivo. We showed that lentiviral vectors transduce PC-derived cell lines with high efficiency (>90%), regardless of the differentiation state of the cell. Next, we transferred human interferon beta (hIFN-beta) gene. Expression of hIFN-beta in PC cells using lentiviral vectors resulted in the inhibition of cell proliferation and the induction of cell death by apoptosis. In vivo, lentiviral administration of hIFN-beta prevented PC tumor progression for up to 15 days following gene therapy, and induced tumor regression/stabilization in 50% of the mice treated. Again, hIFN-beta expression resulted in cancer cell proliferation inhibition and apoptosis induction. We provide evidence that human immunodeficiency virus (HIV)-1-based lentiviral vectors are very efficient for gene transfer in PC-derived cells in vitro and in vivo. As a consequence, delivery of hIFN-beta stopped PC tumor progression. Thus, our approach could be applied to the 85% of PC patients with a locally advanced disease.

Lister strain vaccinia virus, a potential therapeutic vector targeting hypoxic tumours

Hypoxia contributes to the aggressive and treatment-resistant phenotype of pancreatic ductal adenocarcinoma (PDAC). Oncolytic vaccinia virus has potential as an anti-tumour agent but the ability to lyse hypoxic tumour cells is vital for clinical efficacy. We hypothesised that unique aspects of the poxvirus lifecycle would protect it from attenuation in hypoxic conditions. We characterised and compared the viral protein production, viral replication, cytotoxicity and transgene expression of Lister strain vaccinia virus in a panel of pancreatic cancer cell lines after exposure to normoxic or hypoxic conditions. Viral protein production was not affected by hypoxia, and high viral titres were produced in both normoxic and hypoxic conditions. Interestingly there was a five-fold (P<0.001) and 10-fold (P<0.0001) increase in viral cytotoxicity for CFPac1 and MiaPaca2 cell lines respectively in hypoxic conditions. Cytotoxicity was equivalent in the remaining cell lines. Levels of transgene expression (luciferase reporter gene) from the vaccinia viral vector were comparable regardless of the ambient oxygen concentration. The present study suggests that vaccinia virus is a promising vector for targeting pancreatic cancer and potentially other hypoxic tumour types.

Lister strain of vaccinia virus armed with endostatin-angiostatin fusion gene as a novel therapeutic agent for human pancreatic cancer

Survival following pancreatic cancer remains poor despite incremental advances in surgical and adjuvant therapy, and new strategies for treatment are needed. Oncolytic virotherapy is an attractive approach for cancer treatment. In this study, we have evaluated the effectiveness of the Lister vaccine strain of vaccinia virus armed with the endostatin-angiostatin fusion gene (VVhEA) as a novel therapeutic approach for pancreatic cancer. The Lister vaccine strain of vaccinia virus was effective against all human pancreatic carcinoma cells tested in vitro, especially those insensitive to oncolytic adenovirus. The virus displayed inherently high selectivity for cancer cells, sparing normal cells both in vitro and in vivo, with effective infection of tumors after both intravenous (IV) and intratumoral (IT) administration. The expression of endostatin-angiostatin fusion protein was confirmed in a pancreatic cancer model both in vitro and in vivo, with evidence of inhibition of angiogenesis. This novel vaccinia virus demonstrated significant antitumor potency in vivo against the Suit-2 model by IT administration. The present study suggests that the novel Lister strain of vaccinia virus armed with the endostatin-angiostatin fusion gene is a potential therapeutic agent for pancreatic cancer.

Inhibitory effect of Slug gene silencing with siRNA on pancreatic cancer

AIM: To study the effect on pancreatic cancer in rats of rAAV carrying Slug-siRNA to interfere Slug gene expression.

METHODS: A model of subcutaneous tumor was generated through injection of human pancreatic cancer cells BxPC-3 into the nude mice, two weeks later, the nude mice were divided into 3 groups randomly with 6 per group. A recombinant adeno-associated virus vector containing Slug-siRNA gene (rAAV-Slug-siRNA) was constructed. By continuous infusions over 14 d, in negative controls, 1 × 10⁹ puf (50 µL) rAAV-EGFP was injected, while in black controls, 50 µL normal saline was given, in experimental groups, 1 × 10⁹ puf (50 µL) rAAV2-EGFP-slug-siRNA was injected. The general condition, feeding, activities of the rats, and weight were observed. The growth curve of the rats was drawn. After 6 wk, the rats were killed with CO₂, and tumor tissues were cut off and weighed. The expression of Slug protein was detected using the IHC SP method, the apoptosis was detected by TUNEL, and the ultrastructure was detected with TEM.

RESULTS: In the beginning of 2 wk, not any apparent growth change was found in three groups. But 2 wk later, the tumor grew slowly in experimental groups than in negative controls and blank controls (P < 0.05). After treatment of 6 wk, the tumor weight in experimental groups was lower than in negative control group or than blank controls group (3.26 ± 0.48 g vs 7.56 ± 1.25 g, 7.50 ± 1.23 g, all P < 0.05). The AI was significant higher in experimental group than in the negative control group or blank control group (0.27 ± 0.06 vs 0.024 ± 0.01, 0.025 ± 0.01, all P < 0.05). The inhibitory rate was 71.4% in the experimental group, and 0.04% in the negative group, showing a significant difference (P < 0.01). Under TEM, the organelle had fuzzy structure, and karyopyknosis, chromatin margination was found in tumor cells in experimental group. The expression of Slug was down-regulated in experimental groups.

CONCLUSION: RNAi-mediated Slug gene with rAAV silencing could transfect to pancreatic cancer cells and silence Slug effectively and selectively, which results in the growth and proliferation inhibition in pancreatic cancer in vivo.

Identification of a new G-quadruplex motif in the KRAS promoter and design of pyrene-modified G4-decoys with antiproliferative activity in pancreatic cancer cells

A new quadruplex motif located in the promoter of the human KRAS gene, within a nuclease hypersensitive element (NHE), has been characterized. Oligonucleotides mimicking this quadruplex are found to compete with a DNA-protein complex between NHE and a nuclear extract from pancreatic cancer cells. When modified with (R)-1-O-[4-1-(1-pyrenylethynyl) phenylmethyl]glycerol insertions (TINA), the quadruplex oligonucleotides showed a dramatic increase of the T(m) (deltaT(m) from 22 to 32 degrees C) and a strong antiproliferative effects in Panc-1 cells.

Endoscopic ultrasound-guided intratumoural therapy for pancreatic cancer

Pancreatic cancer is the second most frequent gastrointestinal malignancy and carries a dismal prognosis. The current standard of care includes resection, if possible, as well as systemic chemoradiation therapy. Endoscopic ultrasound (EUS) is an established technique for the diagnosis and staging of pancreatic adenocarcinoma. Interventional EUS via fine needle injection (FNI) for the treatment of pancreatic cancer is a rapidly expanding field. The present article reviews the up-to-date developments in EUS FNI for intratumoural pancreatic cancer therapy, including antitumoural agents, immunotherapy, ablative techniques and new delivery systems. The therapeutic modalities discussed are currently under development and will hopefully reach clinical practice if benefit is demonstrated through clinical trials. EUS FNI may be an exciting new technique for the delivery of desperately needed novel therapies for pancreatic cancer.

Establishment and molecular profiling of a novel human pancreatic cancer panel for 5-FU

Ten novel human pancreatic carcinoma cell lines (Sui65 through Sui74) were established from a transplantable pancreatic carcinoma cell line. All the cell lines resembled the original clinical carcinoma in terms of the morphological and biological features, presenting with genetic alterations such as point mutations of K-ras and p53, attenuation or lack of SMAD4 and p16 and other relevant cellular characteristics. Using this panel, we evaluated the effects of 5-FU in suppressing the proliferation of pancreatic carcinoma cells. When tested in vitro, although Sui72 was highly susceptible to 5-FU, the other cell lines were found to be resistant to the drug. When Sui72 and Sui70 were implanted subcutaneously in SCID mice followed by treatment with 5-FU, the drug was found to be effective against Sui72 but not Sui70, consistent with the results in vitro. In order to identify the molecular determinant for high sensitivity of Sui72 to 5-FU, we examined the mRNA expression levels of the metabolic enzymes of 5-FU. Decreased expression of DPYD was observed in Sui72 as compared with other cell lines (0.1 versus 0.6 +/- 0.5, 0.1-fold). It is believed that the novel cell lines established in the present study will be useful for analyzing the pattern of progression of pancreatic cancer and for evaluating the efficacy of anticancer agents.

Ultrasound-mediated microbubble destruction enhances gene transfection in pancreatic cancer cells

INTRODUCTION

The purpose of this study was to determine whether ultrasound exposure combined with microbubble destruction could be used to enhance non-viral gene delivery in human pancreatic carcinoma cells (PANC-1).

METHODS

The study was performed with four experimental groups: Group P, plasmid alone; Group P+M, plasmid and microbubbles; Group P+U, plasmid and ultrasound; Group P+U+M, plasmid with ultrasound and microbubbles. Plasmid DNA encoding enhanced green fluorescent protein (pEGFP) was gently mixed with commercially available ultrasound microbubble contrast agents (SonoVue; Bracco Diagnostics Inc, Milan, Italy) in Group P+M and Group P+U+M. The different combinations of DNA and DNA plus microbubbles were added to cultured PANC-1 cells under different conditions. Transfection efficiency and cell viability were assessed by FACS analysis (Becton Dickinson, San Jose, CA, USA), confocal laser scanning microscopy, and trypan blue staining.

RESULTS

The results demonstrated that microbubbles with ultrasound exposure could significantly enhance the reporter gene expression as compared with other groups (Group P+U+M, 21.4%+/-3.16%; Group P, 2.9%+/-0.45%; Group P+M, 3.1%+/-0.51%; Group P+U, 6.1%+/-1.27%; P<0.01). No statistically significant difference was observed in the PANC-1 cell viability between Group P+U+M and other groups (P>0.05).

CONCLUSION

Our in-vitro findings suggest that ultrasound-mediated microbubble destruction has the potential to promote efficient gene transfer into PANC-1 cells without significant cell death. This non-invasive gene transfer method may be a useful tool for safe clinical gene therapy of pancreatic cancer in the future.

Selective killing of Smad4-negative tumor cells via a designed repressor strategy

Smad4 is a key tumor suppressor that is frequently deleted or inactive in pancreatic and colon tumors. In this report, we describe an approach for attaining selective killing of Smad4-deficient tumor cells. Using a vector system involving a designed repressor with zinc finger binding domains and the herpes simplex virus thymidine kinase (HSV-TK) "suicide gene," we demonstrate Smad4-responsive regulation of HSV-TK expression and consequent altered susceptibility to the prodrug ganciclovir (GCV). In pancreatic tumor cell lines stably transfected with the vector system, a robust differential of HSV-TK expression and GCV toxicity was attained depending on the presence or absence of cotransfected Smad4. In matched colon tumor cell lines lacking Smad4 or expressing physiological levels of Smad4, an adenoviral version of the vector system attained a significant degree of preferential killing of Smad4-negative tumor cells in response to GCV. These findings demonstrate the possibility of achieving selective killing of pancreatic and colon cells depending on their Smad4 status.

Both HIV- and EIAV-based lentiviral vectors mediate gene delivery to pancreatic cancer cells and human pancreatic primary patient xenografts

Few effective treatments for pancreatic cancer exist, especially for patients with advanced disease. Gene therapy alone, or combined with current treatments, offers an alternative approach. Here we examined the potential of primate and nonprimate lentivectors to mediate gene delivery to this cancer type. VSV-G pseudotyped lentivectors based on human immunodeficiency type-1 virus (HIV-1) and equine infectious anemia virus (EIAV), containing the enhanced green fluorescent protein (EGFP) reporter gene were prepared and characterized for titer and RNA content. Vector-mediated gene delivery was examined in five pancreatic cancer cell lines in vitro, and in MiaPaCa-2 cells as well as in five human primary patient biopsies xenografted subcutaneously in nude mice. While individual cell lines showed differential sensitivities to transduction with lentivectors, all cell lines were successfully transduced with both vector types. Similarly, both vectors transduced MiaPaCa-2 and all of the human primary patient xenografts. We observed 6-29% transduction with HIV-based vectors (n=3 xenografts) and 1.8-30% with EIAV-based vectors (n=4 xenografts). Long-term EIAV-mediated gene expression was recorded in cell lines for up to 6 months. We conclude that these vectors have potential as mediators of clinical gene therapy for pancreatic cancer treatment. Moreover, they are useful laboratory research tools for pancreatic cancer research.

RNAi-mediated knockdown of target genes: a promising strategy for pancreatic cancer research

Pancreatic cancer is one of the most aggressive malignancies with a very poor prognosis, partially due to its very low accessibility to resection and resistance to chemoradiotherapy. As such, it is reasonable to find more effective, specific therapies and the related therapeutic targets. The identification of certain genes contributing to the tumorigenesis and poor prognosis provides the specific targets for efficient silencing by RNA interference (RNAi). As a powerful tool to suppress gene expression in mammalian cells, RNAi can be directed against pancreatic cancer through various pathways, including the inhibition of overexpressed oncogenes, suppression of tumor growth, metastasis and enhancement of apoptosis. In combination with chemoradiotherapy agents, RNAi can also attenuate the chemoradiation resistance of pancreatic cancer. In addition, RNAi has been used to define the 'loss of function' of endogenous genes in pancreatic cancer. This review provides a brief introduction to recent developments of RNAi applications in pancreatic cancer studies and suggestions for further exploration. It substantially demonstrates that RNAi holds a promising therapeutic potential as a future treatment for pancreatic cancer.

Pancreatic cancer: pathogenesis, prevention and treatment

Pancreatic cancer is the fourth leading cause of cancer death in the United States with a very low survival rate of 5 years. To better design new preventive and/or therapeutic strategies for the fight against pancreatic cancer, the knowledge of the pathogenesis of pancreatic cancer at the molecular level is very important. It has been known that the development and the progression of pancreatic cancer are caused by the activation of oncogenes, the inactivation of tumor suppressor genes, and the deregulation of many signaling pathways among which the EGFR, Akt, and NF-kappaB pathways appear to be most relevant. Therefore, the strategies targeting EGFR, Akt, NF-kappaB, and their downstream signaling could be promising for the prevention and/or treatment of pancreatic cancer. In this brief review, we will summarize the current knowledge regarding the pathogenesis, prevention, and treatment of pancreatic cancer.

The Myc oncoprotein as a therapeutic target for human cancer

Myc expression is deregulated in a wide range of human cancers and is often associated with aggressive, poorly differentiated tumors. The Myc protein is a transcription factor that regulates a variety of cellular processes including cell growth and proliferation, cell-cycle progression, transcription, differentiation, apoptosis, and cell motility. Potential strategies that either inhibit the growth promoting effect of Myc and/or activate its pro-apoptotic function are presently being explored. In this review, we give an overview of Myc activation in human tumors and discuss current strategies aimed at targeting Myc for cancer treatment. Such therapies could have potential in combination with mechanistically different cytotoxic drugs to combat and eradicate tumors cells.

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