Gemcitabine-based chemogene therapy for pancreatic cancer using Ad-dCK::UMK GDEPT and TS/RR siRNA strategies

Molecular predictors of gemcitabine response in pancreatic cancer

Gemcitabine is one of the most used anti-neoplastic drugs with documented activity in almost all major localizations of cancer. In pancreatic cancer treatment, gemcitabine occupies a prominent place as a first line chemotherapy, partly because of the paucity of other efficacious chemotherapy options. In fact, only a minority of pancreatic cancer patients display a response or even stability of disease with the drug. There are currently no clinically applicable means of predicting which patient will derive a clinical benefit from gemcitabine although several proposed markers have been studied. These markers are proteins involved in drug up-take, activation and catabolism or proteins that define the ability of the cell to undergo apoptosis in response to the drug. Several of these markers are reviewed in this paper. We also briefly discuss the possible role of stem cells in drug resistance to gemcitabine.

Epigenetic markers for chemosensitivity and chemoresistance in pancreatic cancer--a review

Adjuvant first-line gemcitabine monochemotherapy presents a standard treatment for patients with advanced pancreatic adenocarcinoma and improves overall survival in chemosensitive patients. Nonetheless, 6-month progression-free survival remains below 15%, despite interdisciplinary approaches. The success of gemcitabine treatment is disappointing and-in the absence of reliable tumor markers--challenging to quantify. Epigenetic alterations have been recently identified to take on important roles in cancer development and possibly cancer treatment. In this context, microRNAs are becoming increasingly acknowledged as useful biomarkers for classifying cancers and providing information on their chemo- and radiosensitivity. This review illustrates the potential of genetic and epigenetic markers in the prediction of chemosensitivity in pancreatic cancer patients and in the monitoring of their response rates to adjuvant therapy.

Novel strategy with gemcitabine for advanced pancreatic cancer

5-fluorouracil (5-FU) is widely used in chemotherapy for gastric and colorectal cancer, but gemcitabine (GEM), and not 5-FU, is approved as a standard drug for use in pancreatic cancer. Interindividual variation in the enzyme activity of the GEM metabolic pathway can affect the extent of GEM metabolism and the efficacy of GEM chemotherapy. Human equilibrative nucleoside transporter 1 (hENT1) is recognized as a major transporter of GEM into cells. In addition, a factor that activates hENT1 is the inhibition of thymidylate synthase (TS), one of the 5-FU metabolic enzymes; TS inhibition mediates depleting intracellular nucleotide pools, resulting in the activation of the salvage pathway mediated through hENT1. In this paper, the role of 5-FU in GEM-based chemotherapy for pancreatic cancer is discussed with special emphasis on enzymes involved in the 5-FU and GEM metabolic pathways and in the correlation between GEM responsiveness and the expression of 5-FU and GEM metabolic enzymes.

Deoxycytidine kinase is overexpressed in poor outcome breast cancer and determines responsiveness to nucleoside analogs

Only a minority of breast cancer patients responds to chemotherapy and we lack predictive biomarkers that help to select a patient-tailored therapy that takes into consideration the molecular heterogeneity of the cancer type. Responsiveness to the clinically important nucleoside analogs gemcitabine and decitabine may be critically determined by Deoxycytidine kinase (DCK) expression as this enzyme is required to convert the inactive prodrugs into their pharmacologically active forms. Here, we examined whether DCK is differentially expressed in breast cancer and evaluated whether DCK expression levels control responsiveness to these nucleoside analogs in vitro by experimentally modulating DCK expression levels. We examined DCK expression in gene expression data sets of breast tumors including the series of 295 consecutive patients that have been classified into low or high risk for recurrence using the MammaPrint 70 gene profile. We found that DCK is expressed at higher levels in patients having poor clinical outcome as judged by the MammaPrint assay. As such, patients that have a poor prognosis may thus be susceptible to treatment with nucleoside analogs. In support of this, we found a causal relationship between DCK levels and sensitivity to these nucleoside analogs in breast cancer cell lines. The data indicate that breast cancers that are at high risk of recurrence express higher levels of DCK, which we find to be strongly correlated to a favorable response to nucleoside analogs. The data suggest that DCK expression in breast cancer could be exploited to select patients that are likely to respond to treatment with nucleoside analogs.

Dinosaurs and ancient civilizations: reflections on the treatment of cancer

Research efforts in the area of palaeopathology have been seen as an avenue to improve our understanding of the pathogenesis of cancer. Answers to questions of whether dinosaurs had cancer, or if cancer plagued ancient civilizations, have captured the imagination as well as the popular media. Evidence for dinosaurian cancer may indicate that cancer may have been with us from the dawn of time. Ancient recorded history suggests that past civilizations attempted to fight cancer with a variety of interventions. When contemplating the issue why a generalized cure for cancer has not been found, it might prove useful to reflect on the relatively limited time that this issue has been an agenda item of governmental attention as well as continued introduction of an every evolving myriad of manmade carcinogens relative to the total time cancer has been present on planet Earth. This article reflects on the history of cancer and the progress made following the initiation of the "era of cancer chemotherapy."

Squalenoyl gemcitabine nanomedicine overcomes the low efficacy of gemcitabine therapy in pancreatic cancer

Development of chemoresistance and rapid inactivation of gemcitabine (Gem), the standard therapy for advanced pancreatic cancer, are responsible of the major therapeutic failures. To overcome the above drawbacks we designed a novel nanomedicine strategy for Gem nanoparticle (NP) formulation based on squalene conjugation. The purpose was to investigate the antitumor efficacy of gemcitabine-squalene (SQ-Gem) NPs on chemoresistant and chemosensitive pancreatic adenocarcinoma models. Cell viability and apoptosis assays showed that SQ-Gem NPs displayed higher antiproliferative and cytotoxic effects, particularly in chemoresistant Panc1 tumor cells. In in vivo studies, compared to native Gem, SQ-Gem NPs decreased significantly the tumor growth, prevented tumor cell invasion, and prolonged the survival time of mice bearing orthotopic pancreatic tumors. These results correlate with a greater reduction of Ki-67 and induction of apoptosis. These findings demonstrate the feasibility of utilizing SQ-Gem NPs to make tumor cells more sensitive to Gem and thus provide an efficient new therapeutic alternative for pancreatic adenocarcinoma.

FROM THE CLINICAL EDITOR

Pancreatic malignancies represent some of the most notoriously treatment resistant cancer varieties. This paper discusses a novel and promising nanotechnology-based treatment approach, currently at the basic science stage.

Potential clinical applications of siRNA technique: benefits and limitations

BACKGROUND

RNA interference (RNAi) has become the method of choice for researchers wishing to target specific genes for silencing and has provided immense potential as therapeutic tools. This narrative review article aimed to understand potential benefits and limitations of RNAi technique for clinical application and in vivo studies through reading the articles published during the recent 3 years.

MATERIALS AND METHODS

Medline database was searched by using 'siRNA' or 'RNAi' and 'in vivo' with limits of dates 'published in the last 3 years', language 'English' and article type 'clinical trial' for obtaining articles on in vivo studies on the use of RNAi technique. Characteristics of clinical trials on siRNA registered at the http://www.ClinicalTrials.gov were analysed.

RESULTS

The only three clinical studies published so far and many in vivo studies in animals showed that the RNAi technique is safe and effective in treatment of cancers of many organ/systems and various other diseases including viral infection, arterial restenosis and some hereditary diseases with considerable benefits such as high specificity, many possible routes of administration and possibility of silencing multiple genes at the same time. Limitations and uncertainty include efficiency of cellular uptake, specific guidance to the target tissue or cell, long-term safety, sustained efficacy and rapid clearance from the body.

CONCLUSIONS

RNAi technique will become an important and potent weapon for fighting against various diseases. RNAi technique has benefits and limitations in its potential clinical applications. Overcoming the obstacles is still a formidable task.

Three-dimensional collagen I promotes gemcitabine resistance in pancreatic cancer through MT1-MMP-mediated expression of HMGA2

One of the hallmarks of human pancreatic ductal adenocarcinoma (PDAC) is its pronounced type I collagen-rich fibrotic reaction. Although recent reports have shown that the fibrotic reaction can limit the efficacy of gemcitabine chemotherapy, the underlying mechanisms remain poorly understood. In this article, we show that the type I collagen allows PDAC cells to override checkpoint arrest induced by gemcitabine. Relative to cells grown on tissue culture plastic, PDAC cells grown in 3-dimensional collagen microenvironment have minimal Chk1 phosphorylation and continue to proliferate in the presence of gemcitabine. Collagen increases membrane type 1 matrix metalloproteinase (MT1-MMP)-dependent ERK1/2 phosphorylation to limit the effect of gemcitabine. Collagen also increases MT1-MMP-dependent high mobility group A2 (HMGA2) expression, a nonhistone DNA-binding nuclear protein involved in chromatin remodeling and gene transcription, to attenuate the effect of gemcitabine. Overexpression of MT1-MMP in the collagen microenvironment increases ERK1/2 phosphorylation and HMGA2 expression, and thereby further attenuates gemcitabine-induced checkpoint arrest. MT1-MMP also allows PDAC cells to continue to proliferate in the presence of gemcitabine in a xenograft mouse model. Clinically, human tumors with increased MT1-MMP show increased HMGA2 expression. Overall, our data show that collagen upregulation of MT1-MMP contributes to gemcitabine resistance in vitro and in a xenograft mouse model, and suggest that targeting MT1-MMP could be a novel approach to sensitize pancreatic tumors to gemcitabine.

CXCL12-CXCR4 signalling axis confers gemcitabine resistance to pancreatic cancer cells: a novel target for therapy

BACKGROUND

Pancreatic cancer cells are highly resistant to drug therapy; however, underlying causes remain largely unknown. We hypothesised that the activation of CXCL12-CXCR4 signalling confers drug resistance to pancreatic cancer cells by potentiating survival. CXCR4 is overexpressed in precancerous/malignant pancreatic lesions and cancer stem cells, and implicated in its pathogenesis.

METHODS

Effect of CXCR4 activation by CXCL12 on restricting the gemcitabine-induced cytotoxicity and stimulating the survival signalling was examined in pancreatic cancer cells by MTT, DNA laddering, caspase activity, immunoblot, and promoter-reporter assays. Subsequently, we examined the effect of CXCR4 antagonist, AMD3100, in abrogating the rescue effect of activated CXCL12-CXCR4 signalling.

RESULTS

The pancreatic cancer cells treated with gemcitabine exhibited reduced cytotoxicity in the presence of CXCL12 as compared with the cells treated with drug alone. CXCL12 induced the activation of FAK, ERK, and Akt signalling pathways, enhanced transcriptional activities of β-catenin and NF-κB, and expression of survival proteins. AMD3100 arrested the CXCL12-induced pancreatic cancer cell growth and drug resistance.

CONCLUSION

Our findings demonstrate, for the first time, a role of CXCL12-CXCR4 signalling axis in conferring drug resistance to pancreatic cancer cells and suggest that it could serve as a novel therapeutic target for pancreatic cancer therapy, alone and in combination with the cytotoxic drug.

Contribution of thymidylate synthase to gemcitabine therapy for advanced pancreatic cancer

OBJECTIVES

Thymidylate synthase (TS) inhibitors activate human equilibrative nucleoside transporter 1. We evaluated the contribution of TS expression to determine a treatment method providing an effect from gemcitabine (GEM).

METHODS

The expression of 5-fluorouracil (5-FU) and GEM metabolic factors (5-FU: TS, dihydropyrimidine dehydrogenase, orotate phosphoribosyltransferase; GEM: human equilibrative nucleoside transporter 1, deoxycytidine kinase, cytidine deaminase, 5'-nucleotidase) were studied in 7 pancreatic cancer cell lines by Western blotting, and drug resistance was evaluated by 3-[4,5-dimethylthiazol]-2,5-dephenyl tetrazolium bromide assay. The expression of 5-FU factors was observed immunohistochemically in resected pancreatic cancer specimens.

RESULTS

Gemcitabine concentrations that inhibited colony formation by 50% correlated with TS protein expression (P = 0.0169). With a 5-FU non-growth-inhibiting dose, GEM concentrations that inhibited colony formation by 50% were significantly reduced by one fourth to one tenth. Knockout of TS expression by small interfering RNA decreased resistance to GEM in the cell lines (P = 0.0019). Immunohistochemically, TS expression related to disease-free survival time of patients treated with GEM (P = 0.0224). A high expression of 5-FU factors was detected: orotate phosphoribosyltransferase: differentiated cases (P = 0.0137), lower T factor (P = 0.0411); dihydropyrimidine dehydrogenase: nerve invasion (P = 0.0188), lymph node recurrence (P = 0.0253); TS, positive N factor (P = 0.0061).

CONCLUSIONS

The expression of TS provides an alternative source of substrate for DNA synthesis and positively correlates with GEM resistance and shortened patient survival.

The War on Cancer rages on

In 1971, the "War on Cancer" was launched by the US government to cure cancer by the 200-year anniversary of the founding of the United States of America, 1976. This article briefly looks back at the progress that has been made in cancer research and compares progress made in other areas of human affliction. While progress has indeed been made, the battle continues to rage on.

Viral-based gene delivery and regulated gene expression for targeted cancer therapy

IMPORTANCE OF THE FIELD

Cancer is both a major health concern and a care-cost issue in the US and the rest of the world. It is estimated that there will be a total of 1,479,350 new cancer cases and 562,340 cancer deaths in 2009 within the US alone. One of the major obstacles in cancer therapy is the ability to target specifically cancer cells. Most existing chemotherapies and other routine therapies (such as radiation therapy and hormonal manipulation) use indiscriminate approaches in which both cancer cells and non-cancerous surrounding cells are treated equally by the toxic treatment. As a result, either the cancer cell escapes the toxic dosage necessary for cell death and consequently resumes replication, or an adequate lethal dose that kills the cancer cell also causes the cancer patient to perish. Owing to this dilemma, cancer- or organ/tissue-specific targeting is greatly desired for effective cancer treatment and the reduction of side effect cytotoxicity within the patient.

AREAS COVERED IN THIS REVIEW

In this review, the strategies of targeted cancer therapy are discussed, with an emphasis on viral-based gene delivery and regulated gene expression.

WHAT THE READER WILL GAIN

Numerous approaches and updates in this field are presented for several common cancer types.

TAKE HOME MESSAGE

A summary of existing challenges and future directions is also included.