Expression of Snail in Pancreatic Cancer Promotes Metastasis and Chemoresistance

doi:10.1016/j.jss.2006.09.027

Journal of Surgical Research

Volume 141, Issue 2, August 2007, Pages 196-203

https://doi.org/10.1016/j.jss.2006.09.027 Get rights and content

Background

Pancreatic cancer is a dreadful malignancy. Because of its tendency to metastasis and its resistance to chemotherapy, the prognosis remains poor. Snail is a transcriptional factor that endows epithelial cells with migratory and anti-apoptotic abilities. Its expression has been demonstrated in many tumors. We hypothesized that Snail may be expressed in pancreatic cancer, and it may confer invasive and chemoresistant properties.

Materials, methods, and results

We immunohistochemically examined Snail expression in pancreatic cancer and found that it was expressed in 20 of 56 (36%) samples of pancreatic cancer. The Snail expression had a close correlation with lymph node invasion and distant metastasis. After transfecting Snail cDNA into pancreatic cancer cell line Panc-1, we found that Snail triggered overt epithelial to mesenchymal transitions in Panc-1 cells. The tumor invasive ability in vitro was evaluated using a transwell invasive chamber. Snail dramatically promoted the invasive ability of Panc-1 cells. Chemosensitivity of Panc-1 cells to 5-fluorouracil or gemcitabine after Snail transfection was assayed by MTT cell proliferation assay. Overexpression of Snail enhanced the chemoresistance to 5-fluorouracil of gemcitabine at different dosages. Moreover, Snail-transfected Panc-1 cells produced more spontaneous metastasis than parental untransfected cells after orthotopically injected into the pancreas of nude mice.

Conclusion

Snail is expressed in pancreatic cancer; it confers enhanced invasive ability and chemoresistance to pancreatic cancer cells. Snail may be a marker for predicting the malignancy of pancreatic cancer. Further therapy target to Snail may be of great benefit to pancreatic cancer patients.

Introduction

Pancreatic cancer is a highly malignant carcinoma, which is a leading cause of cancer-related deaths in the developed world [1, 2]. Despite improvement in diagnosis and treatment, the prognosis remains poor. Most patients diagnosed with pancreatic cancer cannot receive curative surgical resection. Even after surgical resection, the 5-year survival rate is only about 20% [3]. One major characteristic of pancreatic cancer is its early systemic dissemination and its extraordinary local tumor progression [4, 5]. At the time of diagnosis, a large percentage of pancreatic cancer patients have found locally invasion or distant metastasis. Besides, this malignancy is resistant to nearly all of the existing chemotherapeutic agents. To improve the prognosis of pancreatic cancer, there is an urgent need to elucidate the molecular mechanisms underlying the malignant behaviors of pancreatic cancer.

Metastasis is a multistep process in which cancer cells must decrease adhesion with their neighbors, acquire the ability to migrate, and invade to surrounding tissues. This has often been correlated with loss of epithelial properties and acquisition of fibroblast-like phenotype. The phenomenon is referred to as epithelial to mesenchymal transitions (EMT) in which polarized epithelial cells are converted into motile mesenchymal cells. EMT is crucial in embryo development, wound repair, and tissue remolding, in which it is under tight regulation. While in cancer, the tightly regulated process is out of control. This is often used by cancer cells to have unlimited migrating abilities [6, 7]. Moreover, EMT may be a mechanism for cancer cells to survive in the aberrant environment: fetal rat hepatocytes that underwent EMT can resist the apoptotic effects induced by TGF-β1 [8]. EMT has been shown to occur in the progression of many malignancies such as breast cancer, melanoma, and pancreatic cancer [9, 10, 11].

Snail is a transcriptional factor that is required for mesoderm and neural crest formation during metazoan development. It has been identified as a key regulator for EMT during embryonic development [12, 13]. Snail is overexpressed when ectodermal epithelial cells transit into mesenchymal cells [14, 15]. Moreover, Snail has been implicated in the progression of cancer in which it converts cancer cells with migratory properties by triggering EMT. Ectopic expression of Snail in epithelial cancer cells led to repression of epithelial markers, activation of mesenchymal markers, and acquisition of migratory ability [16]. Besides, Snail may promote metastasis through conferring resistance to cell death [17]. Overexpression of Snail has been demonstrated in the progression of many malignancies such as breast cancer, colon cancer, gastric cancer, and melanoma [18, 19, 20, 21]. However, expression of Snail in pancreatic cancer and its significance has not been elucidated. We hypothesized that Snail may be expressed in pancreatic cancer and may endow pancreatic cancer cells with invasive and chemoresistant abilities.

To test our hypothesis, we immunohistochemically examined the Snail expression in pancreatic cancer tissues. Besides, we transfected the Snail-encoding sequence into pancreatic cancer cell line Panc-1 and tested the changes of biological behavior after transfection. We found that Snail enhanced the invasive ability and chemoresistance of Panc-1 cells.

Section snippets

Tissue Samples and Immunohistochemistry

Fifty-eight paraffin-embedded tissue samples of pancreatic cancer were obtained from the Pancreatic Center of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology between 2000 and 2004. The tumors were staged according to the pathologic tumor-node-metastasis staging system [22]. There were 14 cases of well differentiation, 18 cases of moderate differentiation, and 24 cases of poor differentiation. The paraffin-embedded tissue samples were consecutively cut into

Expression of Snail in Pancreatic Cancer

We immunohistochemically examined the Snail expression in pancreatic cancer tissues. The positive Snail staining was mainly found in the nucleus and cytoplasms of a proportion of cancer cells (Fig. 1). According to the criteria described earlier, 20 of 56 pancreatic cancers (36%) were positive for Snail staining, and 36 pancreatic cancers (64%) were negative. Moreover, Snail expression had a close correlation with lymph node invasion and distant metastasis (Table 1). Seven of eight cases with

Discussion

In our experiment, we demonstrated that Snail is expressed in pancreatic cancer. Twenty of 56 (36%) cases of pancreatic cancer were positive for Snail expression. Snail may be used by a part of cancer cells to its own purpose. In our study, we found that Snail had a close correlation with lymph node invasion (P = 0.005) and distant metastasis (P = 0.002). Patients with lymphatic invasion and distant metastasis had a high Snail-positive expression rate. It suggested that Snail may be involved in

Acknowledgments

We thank Professor Masayuki Ozawa (Department of Biochemistry and Molecular Biology, Graduate School of Medical and Dental Sciences, Kagoshima University, Japan) for providing the Snail-expressing vector. We thank Dr. Quansheng Wang (Union Hospital, Tongji Medical College, Huazhong University of Science and Technology) for providing the Snail antibody.

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Oncology/endocrineExpression of Snail in Pancreatic Cancer Promotes Metastasis and Chemoresistance

Background

Materials, methods, and results

Conclusion

Introduction

Section snippets

Tissue Samples and Immunohistochemistry

Expression of Snail in Pancreatic Cancer

Discussion

Acknowledgments

Trends Mol Med

Gastroenterology

Mutat Res

J Biol Chem

Trend Genet

Am J Pathol

J Biol Chem

J Biol Chem

Curr Biol

Pancreatology

Radiation to stromal fibroblasts increases invasiveness of pancreatic cancer cells through tumor-stromal interactions

Cancer Res

Long-term results of partial pancreaticoduodenectomy for ductal adenocarcinoma of the pancreatic head: 25-year experience

World J Surg

Invasion and metastasis in pancreatic cancer

Mol Cancer

Epithelial-mesenchymal transitions in tumor progression

Nat Rev Cancer

The epithelial mesenchymal transition confers resistance to the apoptotic effects of transforming growth factor Beta in fetal rat hepatocytes

Mol Cancer Res

Host microenvironment in breast cancer development: Extracellular matrix–stromal cell contribution to neoplastic phenotype of epithelial cells in the breast

Breast Cancer Res

N-cadherin expression and epithelial-mesenchymal transition in pancreatic carcinoma

Clin Cancer Res

Overexpression of Snail family members highlights their ability to promote chick neural crest formation

Development

The mouse Snail gene encodes a key regulator of the epithelial-mesenchymal transition

Mol Cell Biol

Epithelium-mesenchyme transition during neural crest development

Acta Anat (Basel)

The transcription factor Snail controls epithelial-mesenchymal transitions by repressing E-cadherin expression

Nat Cell Biol

Snail blocks the cell cycle and confers resistance to cell death

Genes Dev

Oncology/endocrine
Expression of Snail in Pancreatic Cancer Promotes Metastasis and Chemoresistance