Targeted therapies for pancreatic cancer

Degalactotigonin, a Steroidal Glycoside from Solanum nigrum, Induces Apoptosis and Cell Cycle Arrest via Inhibiting the EGFR Signaling Pathways in Pancreatic Cancer Cells

Degalactotigonin (1) and three other steroidal compounds solasodine (2), O-acetyl solasodine (3), and soladulcoside A (4) were isolated from the methanolic extract of Solanum nigrum, and their chemical structures were elucidated by spectroscopic analyses. The isolated compounds were evaluated for cytotoxic activity against human pancreatic cancer cell lines (PANC1 and MIA-PaCa2) and lung cancer cell lines (A549, NCI-H1975, and NCI-H1299). Only degalactotigonin (1) showed potent cytotoxicity against these cancer cell lines. Compound 1 induced apoptosis in PANC1 and A549 cells. Further study on its mechanism of action in PANC1 cells demonstrated that 1 significantly inhibited EGF-induced proliferation and migration in a concentration-dependent manner. Treatment of PANC1 cells with degalactotigonin induced cell cycle arrest at G0/G1 phase. Compound 1 induced downregulation of cyclin D1 and upregulation of p21 in a time- and concentration-dependent manner and inhibited EGF-induced phosphorylation of EGFR, as well as activation of EGFR downstream signaling molecules such as Akt and ERK.

Signal-Targeted Therapies and Resistance Mechanisms in Pancreatic Cancer: Future Developments Reside in Proteomics

For patients with metastatic pancreatic cancer that are not eligible for surgery, signal-targeted therapies have so far failed to significantly improve survival. These therapeutic options have been tested in phase II/III clinical trials mostly in combination with the reference treatment gemcitabine. Innovative therapies aim to annihilate oncogenic dependency, or to normalize the tumoural stroma to allow immune cells to function and/or re-vascularisation to occur. Large scale transcriptomic and genomic analysis revealed that pancreatic cancers display great heterogeneity but failed to clearly delineate specific oncogene dependency, besides oncogenic Kras. Beyond these approaches, proteomics appears to be an appropriate approach to classify signal dependency and to identify specific alterations at the targetable level. However, due to difficulties in sampling, proteomic data for this pathology are scarce. In this review, we will discuss the current state of clinical trials for targeted therapies against pancreatic cancer. We will then highlight the most recent proteomic data for pancreatic tumours and their metastasis, which could help to identify major oncogenic signalling dependencies, as well as provide future leads to explain why pancreatic tumours are intrinsically resistant to signal-targeted therapies. We will finally discuss how studies on phosphatidylinositol-3-kinase (PI3K) signalling, as the paradigmatic pro-tumoural signal downstream of oncogenic Kras in pancreatic cancer, would benefit from exploratory proteomics to increase the efficiency of targeted therapies.

The significance of Trk receptors in pancreatic cancer

This study investigated the Trk receptor family as a therapeutic target in pancreatic ductal adenocarcinoma and assessed their prognostic significance. Global gene expression analysis was investigated in prospectively collected pancreatic ductal adenocarcinomas that had either undergone neoadjuvant chemoradiation or were treated by surgery. PANC-1 and MIA-PaCa-2 cell lines were investigated to establish whether fractionated radiation altered expression of four neuroendocrine genes and whether this resulted in subsequent changes in radiosensitivity. A specific inhibitor of TrkA, B, and C, AstraZeneca 1332, was investigated in vitro and in vivo in combination with radiation. A tissue microarray was constructed from 77 pancreatic ductal adenocarcinoma patients who had undergone neoadjuvant chemoradiation and the Trk receptor, and neurogenic differentiation 1 expression was assessed and correlated with overall survival. A total of 99 genes were identified that were differentially expressed in the chemoradiation patients with neuroendocrine genes and pathways, in particular the neurogenic differentiation 1 and Trk receptor family, being prominent. Fractionated radiation upregulated the expression of neuroendocrine genes, and AstraZeneca 1332 treatment in vitro enhanced radiosensitivity. No added effect of AstraZeneca 1332 was observed in vivo. Trk receptor expression varied between isoforms but did not correlate significantly with clinical outcome. Radiation treatment upregulated neuroendocrine gene expression but the Trk receptor family does not appear to be a promising treatment target.

Effect of siRNA-mediated FOXC1 gene silencing on proliferation of pancreatic cancer cells

AIM: To investigate small interfering RNA (siRNA)-mediated silencing of fork head box protein C1 (FOXC1) gene on the proliferation human pancreatic cancer Capan-2 and PANC-1 cells and to explore the possible underlying mechanisms.

METHODS: Quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) was used to examine the expression of FOXC1 mRNA in pancreatic cancer cell lines and primary carcinoma tissues from human patients. The human pancreatic cancer cells were divided into two groups: an FOXC1 siRNA group (experimental group) and an NC siRNA group (negative control group). qRT-PCR and Western blot were used to detect FOXC1 mRNA and protein expression in pancreatic cancer cells and to determine proliferation rate after transfection with 5-ethynyl-2'-deoxyuridine (EdU). Flow cytometry was used to examine cell cycle distribution. Western blot analysis was used to detect the expression of cell cycle related proteins P21, P53, and Cyclin D1.

RESULTS: FOXC1 mRNA expression in pancreatic cancer cells and pancreatic cancer tissues were significantly higher than in normal epithelial cells and matched tumor adjacent pancreatic tissue, respectively (P < 0.05). qRT-PCR and Western blot analysis showed that FOXC1 siRNA effectively silenced the transcription and expression of FOXC1 in pancreatic cancer cells. EdU cell proliferation experiments showed that compared with the control group, silencing FOXC1 gene expression in pancreatic cancer cells significantly decreased cell proliferation (P < 0.05). FCM results showed that compared with the control group, FOXC1 silencing arrested the tumor cells in G₀/G₁ phase (P < 0.05). Western blot analysis showed that compared with the control group, Cyclin D1 expression was significantly decreased (P < 0.05), while P21 and P53 expression was unchanged.

CONCLUSION: FOXC1 siRNA can effectively silence the FOXC1 gene expression in human pancreatic cancer Capan-2 PANC-1 cells. FOXC1 silencing inhibits pancreatic cancer cell proliferation and arrests cell cycle in G₀/G₁ phase, suggesting that FOXC1 alters cell proliferation possibly by regulation of the cell cycle through, in part, regulating the expression of Cyclin D1.

Novel therapeutic targets for pancreatic cancer

Pancreatic cancer has become the fourth leading cause of cancer death in the last two decades. Only 3%-15% of patients diagnosed with pancreatic cancer had 5 year survival rate. Drug resistance, high metastasis, poor prognosis and tumour relapse contributed to the malignancies and difficulties in treating pancreatic cancer. The current standard chemotherapy for pancreatic cancer is gemcitabine, however its efficacy is far from satisfactory, one of the reasons is due to the complex tumour microenvironment which decreases effective drug delivery to target cancer cell. Studies of the molecular pathology of pancreatic cancer have revealed that activation of KRAS, overexpression of cyclooxygenase-2, inactivation of p16^INK4A and loss of p53 activities occurred in pancreatic cancer. Co-administration of gemcitabine and targeting the molecular pathological events happened in pancreatic cancer has brought an enhanced therapeutic effectiveness of gemcitabine. Therefore, studies looking for novel targets in hindering pancreatic tumour growth are emerging rapidly. In order to give a better understanding of the current findings and to seek the direction in future pancreatic cancer research; in this review we will focus on targets suppressing tumour metastatsis and progression, KRAS activated downstream effectors, the relationship of Notch signaling and Nodal/Activin signaling with pancreatic cancer cells, the current findings of non-coding RNAs in inhibiting pancreatic cancer cell proliferation, brief discussion in transcription remodeling by epigenetic modifiers (e.g., HDAC, BMI1, EZH2) and the plausible therapeutic applications of cancer stem cell and hyaluronan in tumour environment.

BMP8B mediates the survival of pancreatic cancer cells and regulates the progression of pancreatic cancer

Pancreatic cancer has become one of the most common types of cancer. It is believed that inhibiting the apoptosis of tumor cells as well as overgrowth of tumor cells accelerate the progression and development of cancer. However, the detailed mechanisms of pancreatic cancer progression remain to be fully elucidated. Although bone morphogenetic protein (BMP) families are crucial mediators in some types of cancer, whether BMP8B is involved in regulating the growth and apoptosis of pancreatic cancer cells and the progression of pancreatic cancer is not clear. In the present study, we found that the expression of BMP8B was downregulated in pancreatic cancer tissue compared with the normal tissue adjacent to the tumors. Moreover, the overexpression of BMP8B inhibited cell growth and promoted activation of caspase-3 and -9, the decrease of mitochondrial membrane potential and cell apoptosis in PANC-1, while silencing the BMP8B gene expression with BMP8B shRNA exerted anti-apoptotic effects and boosted the growth of pancreatic cancer cells in BxPC-3. Therefore, we concluded that BMP8B mediates the survival of pancreatic cancer cells and regulates the progression of pancreatic cancer, making it a potential therapeutic target for pancreatic cancer.

S100 family signaling network and related proteins in pancreatic cancer (Review)

The occurrence and development of pancreatic cancer is a complex process convoluted by multi-pathogenies, multi-stages and multi-factors. S100 proteins are members of the S100 family that regulate multiple cellular pathways related to pancreatic cancer progression and metastasis. S100 proteins have a broad range of intracellular and extracellular functions, including the regulation of protein phosphorylation and enzyme activity, calcium homeostasis and the regulation of cytoskeletal components and transcriptional factors. S100 proteins interact with receptor for advanced glycation end-products (RAGE), p53 and p21, which play a role in the degradation of the extracellular matrix (ECM) and metastasis, and also interact with cytoskeletal proteins and the plasma membrane in pancreatic cancer progression and metastasis. S100A11 and S100P are significant tumor markers for pancreatic cancer and unfavorable predictors for the prognosis of patients who have undergone surgical resection. Recently, S100A2 has been suggested to be a negative prognostic biomarker in pancreatic cancer, and the expression of S100A6 may be an independent prognostic impact factor. The expression of S100A4 and S100P is associated with drug resistance, differentiation, metastasis and clinical outcome. This review summarizes the role and significance of the S100 family signaling network and related proteins in pancreatic cancer.

Targeting the Ras-ERK pathway in pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PAC) stands as the poorest prognostic tumor of the digestive tract with limited therapeutic options. PAC carcinogenesis is associated with the loss of function of tumor suppressor genes such as INK4A, TP53, BRCA2, and DPC4, and only a few activated oncogenes among which K-RAS mutations are the most prevalent. The K-RAS mutation occurs early in PAC carcinogenesis, driving downstream activation of MEK and ERK1/2 which promote survival, invasion, and migration of cancer cells. In PAC models, inhibition of members of the Ras-ERK pathway blocks cellular proliferation and metastasis development. As oncogenic Ras does not appear to be a suitable drug target, inhibitors targeting downstream kinases including Raf and MEK have been developed and are currently under evaluation in clinical trials. In this review, we describe the role of the Ras-ERK pathway in pancreatic carcinogenesis and as a new therapeutic target for the treatment of PAC.

Monoclonal antibodies and other targeted therapies for pancreatic cancer

Pancreatic cancer continues to be a challenging disease to treat because of its aggressive nature, advanced stage at the time of diagnosis, and limited treatment options that are available. Traditional cytotoxic chemotherapy provides modest benefit to patients with pancreatic adenocarcinoma. Recently, a FOLFIRINOX regimen revealed improved response in overall and progression-free survival over single-agent gemcitabine in metastatic pancreatic cancer, but there is still much needed advancement in the systemic treatment of pancreatic cancer. There is a growing interest in the development of novel agents, while our understanding of molecular pathogenesis of pancreatic adenocarcinoma continues to expand. With identification of various molecular pathways in pancreatic cancer tumorigenesis, potential targets for drug development have been pursued with the use of monoclonal antibodies and small-molecule inhibitors. Although preclinical studies with multiple targeted therapies demonstrated encouraging results in pancreatic cancer, only erlotinib, an epidermal growth factor receptor inhibitor, showed a marginal survival benefit in a phase III clinical trial, when combined with gemcitabine. As further signaling pathways and their importance in pancreatic cancer tumorigenesis are better understood, further clinical trials will need to be designed to study these targeted agents as single agents, in combination with other novel agents or in combination with cytotoxic chemotherapy. In this review, we present the current knowledge on targeted therapy in pancreatic adenocarcinoma and its application in clinical practice.

Inhibition of SIRT1 combined with gemcitabine therapy for pancreatic carcinoma

BACKGROUND

Pancreatic carcinoma possesses one of the highest lethality rates, highest drug-resistance, and highest incidence rates. The objective of this research was to enhance the efficacy and drug-resistance for pancreatic carcinoma by using inhibition of SIRT1 combined with gemcitabine therapy methods.

METHODS

Three pancreatic carcinoma cells (PANC-1 cells, BxPC-3 cells, and SW1990 cells) received treatment with physiological saline, inhibition of SIRT1, gemcitabine, and combination therapy with inhibition of SIRT1 and gemcitabine in vitro; then BxPC-3 pancreatic cancer xenogeneic mice also received treatment with physiological saline, inhibition of SIRT1, gemcitabine, and combination therapy with inhibition of SIRT1 and gemcitabine in vivo.

RESULTS

The cleaved poly ADP ribose polymerase (PARP)-1 effect of drug in pancreatic carcinoma cells was significantly different (P < 0.05) and the efficacy in descending order was the combination therapy with inhibition of SIRT1 and gemcitabine, inhibition of SIRT1, and gemcitabine. The BxPC-3 pancreatic cancer xenogeneic mice model received treatment with physiological saline, inhibition of SIRT1, gemcitabine, and combination therapy with inhibition of SIRT1 and gemcitabine in vivo and the results showed that the tumor volumes decreased and the survival rate within 45 days increased according to the order of the given drugs and the difference was significant (P < 0.05).

CONCLUSION

Combination therapy with inhibition of SIRT1 and gemcitabine could improve efficacy and survival time in a BxPC-3 pancreatic cancer xenogeneic mice model, compared with single inhibition of SIRT1, or single gemcitabine therapy. The combination therapy method is a potential treatment method for pancreatic carcinoma.

Validation of a robust proteomic analysis carried out on formalin-fixed paraffin-embedded tissues of the pancreas obtained from mouse and human

A number of reports have recently emerged with focus on extraction of proteins from formalin-fixed paraffin-embedded (FFPE) tissues for MS analysis; however, reproducibility and robustness as compared to flash frozen controls is generally overlooked. The goal of this study was to identify and validate a practical and highly robust approach for the proteomics analysis of FFPE tissues. FFPE and matched frozen pancreatic tissues obtained from mice (n = 8) were analyzed using 1D-nanoLC-MS(MS)(2) following work up with commercially available kits. The chosen approach for FFPE tissues was found to be highly comparable to that of frozen. In addition, the total number of unique peptides identified between the two groups was highly similar, with 958 identified for FFPE and 1070 identified for frozen, with protein identifications that corresponded by approximately 80%. This approach was then applied to archived human FFPE pancreatic cancer specimens (n = 11) as compared to uninvolved tissues (n = 8), where 47 potential pancreatic ductal adenocarcinoma markers were identified as significantly increased, of which 28 were previously reported. Further, these proteins share strongly overlapping pathway associations to pancreatic cancer that include estrogen receptor α. Together, these data support the validation of an approach for the proteomic analysis of FFPE tissues that is straightforward and highly robust, which can also be effectively applied toward translational studies of disease.

LY294002 enhances inhibitory effect of gemcitabine on proliferation of human pancreatic carcinoma PANC-1 cells

Phosphatidylinositide 3-kinase (PI3K)/protein kinase B (PKB, Akt) pathway plays a major role in proliferation and survival of many types of cells. The inhibitory effect of LY294002, widely applied as an inhibitor of PI3K, in combination with gemcitabine on proliferation of PANC-1 cells was investigated. The expression of PI3K, phosphorylated Akt (p-Akt) and multidrug-resistance like protein (MRP) in normal pancreas tissues, chronic pancreatitis tissues and pancreatic carcinoma tissues was detected. The effects of LY294002 combined with gemcitabine on proliferation of PANC-1 cells and protein levels of p-Akt and MRP were detected. The results showed that the positive expression rate of PI3K, p-Akt and MRP in pancreatic carcinoma tissues was significantly higher than that in normal pancreas tissues and chronic pancreatitis tissues (P<0.01 and P<0.05 respectively). LY294002 could effectively enhance the inhibitory effect of gemcitabine on proliferation of PANC-1 cells. Furthermore, Western blotting revealed that LY294002 combined with gemcitabine reduced the protein levels of p-Akt and MRP, which contributed to the inhibition of proliferation. It is concluded that LY294002 in combination with gemcitabine may represent an alternative therapy for pancreatic carcinoma.

The role of stroma in pancreatic cancer: diagnostic and therapeutic implications

Pancreatic ductal adenocarcinoma (PDAC) is one of the five most lethal malignancies worldwide and survival has not improved substantially in the past 30 years. Desmoplasia (abundant fibrotic stroma) is a typical feature of PDAC in humans, and stromal activation commonly starts around precancerous lesions. It is becoming clear that this stromal tissue is not a bystander in disease progression. Cancer-stroma interactions effect tumorigenesis, angiogenesis, therapy resistance and possibly the metastatic spread of tumour cells. Therefore, targeting the tumour stroma, in combination with chemotherapy, is a promising new option for the treatment of PDAC. In this Review, we focus on four issues. First, how can stromal activity be used to detect early steps of pancreatic carcinogenesis? Second, what is the effect of perpetual pancreatic stellate cell activity on angiogenesis and tissue perfusion? Third, what are the (experimental) antifibrotic therapy options in PDAC? Fourth, what lessons can be learned from Langton's Ant (a simple mathematical model) regarding the unpredictability of genetically engineered mouse models?

Developments in metastatic pancreatic cancer: is gemcitabine still the standard?

In the past 15 years, we have seen few therapeutic advances for patients with pancreatic cancer, which is the fourth leading cause of cancer-related death in the United States. Currently, only about 6% of patients with advanced disease respond to standard gemcitabine therapy, and median survival is only about 6 mo. Moreover, phase III trials have shown that adding various cytotoxic and targeted chemotherapeutic agents to gemcitabine has failed to improve overall survival, except in cases in which gemcitabine combined with erlotinib show minimal survival benefit. Several meta-analyses have shown that the combination of gemcitabine with either a platinum analog or capecitabine may lead to clinically relevant survival prolongation, especially for patients with good performance status. Meanwhile, many studies have focused on the pharmacokinetic modulation of gemcitabine by fixed-dose administration, and metabolic or transport enzymes related to the response and toxicity of gemcitabine. Strikingly, a phase III trial in 2010 showed that, in comparison to gemcitabine alone, the FOLFIRINOX regimen in patients with advanced disease and good performance status, produced better median overall survival, median progression-free survival, and objective response rates. This regimen also resulted in greater, albeit manageable toxicity.

[New perspectives for radiosensitization in pancreatic carcinoma: a review of mechanisms involved in pancreatic tumorigenesis]

Pancreatic carcinoma is the fifth leading cause of cancer-related mortality. The 5-year overall survival is less than 5 %. This very poor prognosis can be explained both by late diagnosis and by treatment resistance, including resistance to radiation therapy. A better understanding of the pancreatic tumorigenesis and knowledge of the most frequent mutations in pancreatic adenocarcinoma (KRAS, p16, TP53, Smad4) open new perspectives for the development of more effective treatments. This review presents the major genetic and molecular alterations in pancreatic cancer that could be targeted to improve radiosensitization.

Genome-wide screen identifies PVT1 as a regulator of Gemcitabine sensitivity in human pancreatic cancer cells

Gemcitabine has been a first-line chemotherapy agent for advanced pancreatic cancer, which is associated with one of the lowest 5 years survival rates among human cancers. Due to our lack of understanding of the genetic determinants of Gemcitabine sensitivity in pancreatic cancer, the therapeutic effectiveness of Gemcitabine chemotherapy is typically unpredictable. Using a genome-wide and piggyBac transposon-based genetic screening platform, we identified the PVT1 gene as a regulator of Gemcitabine sensitivity and showed that functional inactivation of the PVT1 gene led to enhanced Gemcitabine sensitivity in human pancreatic cancer ASPC-1 cells. The integration of the piggyBac transposon-based vector system into intron 3 of PVT1 was within a common site of oncogenic retroviral insertions and chromosomal translocations. PVT1 is a non-protein encoding gene; the genomic arrangement of PVT1 and its co-amplification with MYC have been implicated in the tumorigenesis of a variety of cancers. The molecular mechanism of PVT1 transcripts in gene regulation remains a puzzle. We demonstrated that overexpression of a full length PVT1 cDNA in the antisense orientation reconstituted enhanced sensitivity to Gemcitabine in naïve ASPC-1 cells, whereas overexpression of a full length PVT1 cDNA in the sense orientation resulted in decreased sensitivity to Gemcitabine. Our results identified PVT1 as a regulator of Gemcitabine sensitivity in pancreatic cancer cells and validated the genome-wide genetic screening approach for the identification of genetic determinants as well as potential biomarkers for the rational design of Gemcitabine chemotherapies for pancreatic cancer.

Palliative chemotherapy for pancreatic malignancies

Metastatic pancreatic cancer is often one of the most challenging malignancies a medical oncologist faces. Although the primary endpoint of many studies remains overall survival, palliation and quality of life are now more commonly being addressed. The author discusses the most common chemotherapeutic modalities for the treatment of metastatic pancreatic cancer, such as single agent chemotherapy, combination therapy, targeted therapy, and second line treatment.

Five steps for structural reform in clinical cancer research

Despite advances in the prevention and early detection of cancer and the treatment of some malignancies, clinical research has not yet delivered treatment benefits of the magnitude anticipated after the launch of imatinib, which established highly effective new treatment standards. The primary impediments to progress are scientific, but the efficiency of research is also affected by structural deficiencies relating to where and by whom it is conducted, as well as how it is organized and regulated. To optimize the research environment and maximize the benefits of improved funding, adjustments in the roles of government, industry, the academic community, national research bodies, and regulatory authorities are needed. A patchwork of reforms that are enabling in character and build on existing expertise can deliver substantial progress without the need for radical intervention.

Intrinsic chemoresistance to gemcitabine is associated with constitutive and laminin-induced phosphorylation of FAK in pancreatic cancer cell lines

Background

One of the major reasons for poor prognosis of pancreatic cancer is its high resistance to currently available chemotherapeutic agents. In recent years, focal adhesion kinase (FAK), a central molecule in extracellular matrix (ECM)/integrin-mediated signaling, has been thought to be a key determinant of chemoresistance in cancer cells. In this study, we aimed to determine the roles of FAK phosphorylation in the intrinsic chemoresistance of pancreatic cancer cell lines.

Results

Our results showed that, the level of constitutive phosphorylation of FAK at Tyr397 correlated with the extent of intrinsic resistance to Gemcitabine (Gem) in four pancreatic cancer cell lines. Moreover, in Panc-1 cells, which had high expression of pFAK, specific inhibition of constitutive FAK phosphorylation by either RNAi or FRNK overexpression decreased the phosphorylation of Akt, reduced the levels of survivin expression and Bad phosphorylation at Ser136 and increased Gem-induced cytotoxicity and apoptosis. However, in AsPC-1 cells with a low level of pFAK, neither FAK RNAi nor FRNK overexpression affected Gem-induced cell apoptosis. We further found that laminin (LN) induced FAK and Akt phosphorylation in a time-dependent manner, increased the levels of survivin and pBad (pS136) and decreased Gem-induced cytotoxicity and apoptosis in AsPC-1 cells; Specific inhibition of LN-induced FAK phosphorylation by either FAK RNAi or FRNK overexpression suppressed the effects of LN on AsPC-1 cells. Moreover, inhibition of constitutive FAK phosphorylation in Panc-1 cells and LN-induced FAK phosphorylation in AsPC-1 cells by a novel and more specific FAK phosphorylation inhibitor PF-573,228 showed similar results with those of FAK phosphorylation inhibition by FAK RNAi or FRNK overexpression.

Conclusions

In conclusion, our research demonstrates for the first time that both constitutive and LN-induced FAK phosphorylation contribute to increased intrinsic chemoresistance to Gem in pancreatic cancer cell lines and these effects are partly due to the regulation of Akt and Bad phosphorylation and survivin expression. Development of selective FAK phosphorylation inhibitors may be a promising way to enhance chemosensitivity in pancreatic cancer.

Novel agents for the treatment of adenocarcinoma of the pancreas

Pancreatic cancer is a particularly challenging malignancy, given its usually advanced stage at diagnosis and its rather limited treatment options. Gemcitabine has been standard therapy for advanced pancreatic cancer for well over a decade. The addition of capecitabine or erlotinib to gemcitabine has resulted in modestly improved, although still poor, overall survival. The majority of the recently completed randomized trials, however, have failed to demonstate an improvement of newer treatments over single-agent gemcitabine. Efforts currently underway center on new cytotoxic chemotherapy drugs, as well as novel targeted agents inhibiting various molecular pathways. Newly discovered proteins and cellular elements involved in tumor growth and invasion are potential therapeutic targets, and have become the focus of current trials, as well as future clinical trials. A better understanding of the biology of the disease at the basic science level, and epidemiology and risk factors from a public-health perspective, are needed. Continued research is clearly warranted with the goal of improving survival and optimizing treatment outcomes in locally advanced and metastatic pancreatic cancer.

Id1/Id3 knockdown inhibits metastatic potential of pancreatic cancer

BACKGROUND

The Id (inhibitor of DNA binding/differentiation) proteins belong to the helix-loop-helix transcriptional regulatory factors, and play important roles in tumor development. Previously, we and others have shown that targeting Id in tumor cells could have important clinical implications. In the present study, we aimed to evaluate the effects of Id inhibition in human pancreatic cancer cells.

MATERIALS AND METHODS

Id1 and Id3 were stably double-knockdown in human pancreatic cancer cell line MIA-Paca2 by means of RNA interference. Expression of Id and integrins were analyzed by flow-cytometry. Cell proliferation was evaluated by MTS assay. Migration was measured by wound closure assay. Adhesion assay was performed to evaluate binding capacity for different extracellular matrix proteins. Finally, in vivo properties of tumor cells were observed in a mouse model of peritoneal metastasis.

RESULTS

Id1/Id3 double-knockdown resulted in decreased ability of pancreatic cancer cells to proliferate and migrate. In addition, Id1/Id3 double-knockdown caused decreased expression of integrins alpha3, alpha6, and beta1, and consequently reduced adhesion of tumor cells to laminin. Finally, peritoneal metastases of Id1/Id3 double-knockdown tumor cells were significantly reduced.

CONCLUSIONS

We concluded that the Id proteins play a pivotal role in the development of peritoneal metastasis of pancreatic cancer, and consequently, their targeting would be a novel strategy for the prevention and treatment of pancreatic cancer.