Pancreatic cancer tumour initiating cells: the molecular regulation and therapeutic values

Knockdown of Notch1 inhibits nasopharyngeal carcinoma cell growth and metastasis via downregulation of CCL2, CXCL16, and uPA

Notch pathway is a highly conserved cell signaling system that plays very important roles in controlling multiple cell differentiation processes during embryonic and adult life. Multiple lines of evidence support the oncogenic role of Notch signaling in several human solid cancers; however, the pleiotropic effects and molecular mechanisms of Notch signaling inhibition on nasopharyngeal carcinoma (NPC) remain unclear. In this study, we evaluated Notch1 expression in NPC cell lines (CNE1, CNE2, SUNE1, HONE1, and HK1) by real-time quantitative PCR and Western blot analysis, and we found that CNE1 and CNE2 cells expressed a higher level of Notch1 compared with HONE1, SUNE1, and HK1 cells. Then Notch1 expression was specifically knocked down in CNE1 and CNE2 cells by Notch1 short hairpin RNA (shRNA). In Notch1 knockdown cells, cell proliferation, migration, and invasion were significantly inhibited. The epithelial-mesenchymal transition of tumor cells was reversed in Notch1-shRNA-transfected cells, accompanied by epithelioid-like morphology changes, increased protein levels of E-cadherin, and decreased expression of vimentin. In addition, knockdown of Notch1 markedly inhibited the expression of urokinase plasminogen activator (uPA) and its receptor uPAR, and chemokines C-C motif chemokine ligand 2 and C-X-C motif chemokine ligand 16, indicating that these factors are downstream targets of Notch1. Furthermore, deleting uPA expression had similar effects as Notch1. Finally, knockdown of Notch1 significantly diminished CNE1 cell growth in a murine model concomitant with inhibition of cell proliferation and induction of apoptosis. These results suggest that Notch1 may become a novel therapeutic target for the clinical treatment of NPC.

Gastric cancer cell growth and epithelial-mesenchymal transition are inhibited by γ-secretase inhibitor DAPT

The Notch signaling pathway may be important in the development and progression of several malignancies. However, the functions of Notch signaling in epithelial-mesenchymal transition (EMT) remain largely unknown. The aim of the present study was to delineate Notch1 expression in gastric cancer (GC) and its function in GC EMT. Using quantitative polymerase chain reaction and western blot analysis, the expression of Notch1 was found to increase in GC cell lines compared with the normal gastric mucosa cell line. In addition, Notch1 expression was found to be downregulated in the non-metastatic-derived GC cell line compared with the metastatic-derived cell line. Furthermore, Notch1 expression was significantly increased in the tumor tissues compared with the adjacent normal mucosa tissues, as well as in patients with metastases than in patients without metastases. To explore the role of the Notch1 signaling pathway in EMT, the GC cell lines, AGS and MKN45, were treated with γ-secretase inhibitor DAPT. Using MTT, Transwell and clonality assays, DAPT was found to inhibit the expression of the Notch1 downstream target, Hes1, and impair the ability of the GC cell lines to migrate, invade and proliferate. The protein levels of the mesenchymal markers, vimentin, neural cadherin and Snail, were decreased; however, the expression of the epithelial marker, epithelial cadherin, was increased in the GC cell lines treated with DAPT. These results indicated that the Notch1 signaling pathway may be important in the development and progression of GC. In conclusion, DAPT inhibits the Notch1 signaling pathway, as well as the growth, invasion, metastasis and EMT of GC cells.

Molecular mechanism underlying lymphatic metastasis in pancreatic cancer

As the most challenging human malignancies, pancreatic cancer is characterized by its insidious symptoms, low rate of surgical resection, high risk of local invasion, metastasis and recurrence, and overall dismal prognosis. Lymphatic metastasis, above all, is recognized as an early adverse event in progression of pancreatic cancer and has been described to be an independent poor prognostic factor. It should be noted that the occurrence of lymphatic metastasis is not a casual or stochastic but an ineluctable and designed event. Increasing evidences suggest that metastasis-initiating cells (MICs) and the microenvironments may act as a double-reed style in this crime. However, the exact mechanisms on how they function synergistically for this dismal clinical course remain largely elusive. Therefore, a better understanding of its molecular and cellular mechanisms involved in pancreatic lymphatic metastasis is urgently required. In this review, we will summarize the latest advances on lymphatic metastasis in pancreatic cancer.

Highly lymphatic metastatic pancreatic cancer cells possess stem cell-like properties

Cancer stem cells are thought to be the origin of tumor metastasis. However, evidence of cancer stem cells as the source of lymphatic metastasis in pancreatic cancer is not clear. In this study, we examined the stem cell-like properties of the highly lymphatic metastatic pancreatic cancer cells BxPC-3-LN. Compared with the parental BxPC-3 cells, the BxPC-3-LN cells showed stem cell-like properties, including high lymphatic metastasis potential, self-renewal ability and chemoresistance. In addition, the BxPC-3-LN cells also expressed higher levels of sonic hedgehog and migrating cancer stem cell surface markers (CD133 and CXCR4) compared to the parental BxPC-3 cells. The growth of BxPC-3-LN cells was significantly inhibited by gemcitabine combined with the sonic hedgehog inhibitor cyclopamine. The BxPC-3-LN cells expressed lower levels of let-7, miR-34, miR-107, miR-125, miR-128, miR-130, miR-132 and miR-141 than the parental BxPC-3 cells detected by microRNA PCR array, which were reported to have close relation to stem cell factors. This study provides evidence that cancer stem cells are the major sources of pancreatic cancer lymphatic metastasis, and microRNAs may regulate lymphatic metastasis in pancreatic cancer through modulating cancer stem cells.

Imaging-guided curative surgical resection of pancreatic cancer in a xenograft mouse model

Pancreatic cancer is the fourth leading cause of cancer related deaths in North America. The poor survival statistics are due to the fact that there are no reliable tests for early diagnosis and no effective therapies once metastasis has occurred. Surgical resection is the only curative treatment for pancreatic cancer; however, only less than 15% of the patients are eligible for surgery at diagnosis. New therapies are urgently needed for this malignant disease. And combinational therapy including surgery, chemotherapy and molecular targeted therapy may further improve the efficacy of individual therapies. However, a reliable mouse model which mimics the human disease and can be used for testing the surgical treatment and surgery-based combinational therapy is not available. In this study, we have established a mouse model for curative surgical resection of pancreatic cancer. Human pancreatic cancer cells were used to create orthotopic xenografts in nude mice, distal pancreatectomy was performed using imaging-guided technology to remove the pancreatic tumors, and sham surgery was performed in the control group. All mice survived the operation and no complication was observed. Surgical resection at early stage improved the survival rate and quality of life of the mice compared with the sham surgery and surgical resection at the late stage. If combined with other therapies such as chemotherapy and molecular targeted therapy, it could further improve the outcome of pancreatic cancer. This mouse model is a useful tool to study the surgical therapy and the tumor recurrence of pancreatic cancer, and could potentially impact the therapeutic choices for this deadly disease.