Pancreatic Tumor Progression Associated With CD133 Overexpression: Involvement of Increased TERT Expression and Epidermal Growth Factor Receptor-Dependent Akt Activation.

OBJECTIVES: The aim of this study was to investigate the role of CD133 in pancreatic ductal adenocarcinoma malignancy and its involvement in epidermal growth factor receptor (EGFR) signaling. METHODS: The effects of CD133 overexpression on cell proliferation, migration, invasiveness, and angiogenesis were investigated in the human pancreatic ductal adenocarcinoma cell line AsPC-1 in vitro and severe combined immunodeficiency xenografts in vivo. RESULTS: AsPC-1 cells overexpressing CD133 (AsPC-1 CD133 cells) had elevated cell proliferation, tumorigenesis, cell cycle progression, adhesion, migration, and angiogenesis. AsPC-1 CD133 cells displayed increased survival during treatment with chemotherapeutic agents. CD133 overexpression resulted in decreased EGF expression, increased telomerase reverse transcriptase expression, and increased Akt phosphorylation. Immunoprecipitation assays and immunofluorescent labeling studies revealed that CD133 physically interacts with EGFR. The EGFR inhibitor gefitinib was shown to have potent anti-CD133 activity, decreasing the CD133-induced migration of AsPC-1 CD133 cells. Knockdown of CD133 was also observed to inhibit AsPC-1 CD133 cell proliferation, migration, and invasion. CONCLUSION: Our results indicate that CD133-induced cancer stem cell activity may arise from enhanced telomerase reverse transcriptase expression and CD133 ligand-independent EGFR activation to exhibit the cancer stem cell phenotype, promoting cancer stem cell proliferation independent of cytokines, with high metastatic potential and the development of chemoresistance.

Aurora-A signaling is activated in advanced stage of squamous cell carcinoma of head and neck cancer and requires osteopontin to stimulate invasive behavior.

The clinical significances, cellular effects, and molecular mechanisms by which Aurora-A mediate its invasive effects in HNSCC are still unclear. Here, we found that Aurora-A expression is significantly higher in tumor tissues on 14-microarray of HNSCC in Oncomine-databases. The activity of Aurora-A was not only found in HNSCC specimens, but also significantly correlated with advanced-T-classification, positive-N-classification, TNM-stage and the poor 5-year survival rate. HNSCC-microarray profile showed that osteopontin and Aurora-A exhibited positive correlation. Stimulation of HNC cells with osteopontin results in an increase in Aurora-A expression where localized at the centrosome. Functionally, Aurora-A had the abilities to stimulate cell motility in HNC cells through increase ERK1/2 activity under osteopontin stimulation. Conversely, depletion of Aurora-A expression by siRNAs suppressed ERK1/2 activity as well as inhibition of cell invasiveness. Treatment with anti-CD44 antibodies in HNC cells not only caused a decrease of mRNA/protein of Aurora-A and ERK1/2 activity upon osteopontin stimulation, but also affected the abilities of Aurora-A-elicited cell motility. Finally, immunohistochemical/Western-blotting analysis of human aggressive HNSCC specimens showed a significant positively correlation between osteopontin-Aurora-A and ERK1/2. These findings suggest that Aurora-A is not only an important prognostic factor but also a new therapeutic target in the osteopontin/CD44/ERK pathway for HNSCC treatment.

Stem cell marker nestin is critical for TGF-ß1-mediated tumor progression in pancreatic cancer.

The stem cell marker nestin is an intermediate filament protein that plays an important role in cell integrity, migration, and differentiation. Nestin expression occurs in approximately one third of pancreatic ductal adenocarcinoma (PDAC), and its expression strongly correlates with tumor staging and metastasis. Little is known about the mechanisms by which nestin influences PDAC progression. Here, nestin overexpression in PDAC cells increased cell motility and drove phenotypic changes associated with the epithelial-mesenchymal transition (EMT) in vitro; conversely, knockdown of endogenous nestin expression reduced the migration rate and reverted cells to a more epithelial phenotype. Mouse xenograft studies showed that knockdown of nestin significantly reduced tumor incidence and volume. Nestin protein expression was associated with Smad4 status in PDAC cells; hence, nestin expression might be regulated by the TGF-ß1/Smad4 pathway in PDAC. We examined nestin expression after TGF-ß1 treatment in human pancreatic cancer PANC-1 and PANC-1 shSmad4 cells. The TGF-ß1/Smad4 pathway induced nestin protein expression in PDAC cells in a Smad4-dependent manner. Moreover, increased nestin expression caused a positive feedback regulator of the TGF-ß1 signaling system. In addition, hypoxia was shown to induce nestin expression in PDAC cells, and the hypoxia-induced expression of nestin is mediated by the TGF-ß1/Smad4 pathway. Finally, the antimicrotubule inhibitors, cytochalasin D and withaferin A, exhibited anti-nestin activity; these inhibitors might be potential antimetastatic drugs. Our findings uncovered a novel role of nestin in regulating TGF-ß1-induced EMT. Anti-nestin therapeutics may serve as a potential treatment for PDAC metastasis.