Nasopharyngeal carcinoma ecology theory: cancer as multidimensional spatiotemporal "unity of ecology and evolution" pathological ecosystem

Nasopharyngeal carcinoma (NPC) is a particular entity of head neck cancer that is generally regarded as a genetic disease with diverse intertumor and intratumor heterogeneity. This perspective review mainly outlines the up-to-date knowledge of cancer ecology and NPC progression, and presents a number of conceptual stepping-stones. At the beginning, I explicitly advocate that the nature of NPC (cancer) is not a genetic disease but an ecological disease: a multidimensional spatiotemporal "unity of ecology and evolution" pathological ecosystem. The hallmarks of cancer is proposed to act as ecological factors of population fitness. Subsequently, NPC cells are described as invasive species and its metastasis as a multidirectional ecological dispersal. The foundational ecological principles include intraspecific relationship (e.g. communication) and interspecific relationship (e.g. competition, predation, parasitism and mutualism) are interpreted to understand NPC progression. "Mulberry-fish-ponds" model can well illustrate the dynamic reciprocity of cancer ecosystem. Tumor-host interface is the ecological transition zone of cancer, and tumor buddings should be recognized as ecological islands separated from the mainland. It should be noted that tumor-host interface has a significantly molecular and functional edge effect because of its curvature and irregularity. Selection driving factors and ecological therapy including hyperthermia for NPC patients, and future perspectives in such field as "ecological pathology", "multidimensional tumoriecology" are also discussed. I advance that "nothing in cancer evolution or ecology makes sense except in the light of the other". The cancer ecology tree is constructed to comprehensively point out the future research direction. Taken together, the establishment of NPC ecology theory and cancer ecology tree might provide a novel conceptual framework and paradigm for our understanding of cancer complex causal process and potential preventive and therapeutic applications for patients.

Hes1 is involved in the self-renewal and tumourigenicity of stem-like cancer cells in colon cancer

A small subpopulation of cancer cells with stem cell-like features might be responsible for tumour generation, progression, and chemoresistance. Hes1 influences the maintenance of certain stem cells and progenitor cells and the digestive systems. We found upregulated Hes1 in poorly differentiated cancer samples compared with well-differentiated tumour samples, and most of the adenocarcinomas exhibited significantly higher levels of Hes1 mRNA compared with that observed in matched normal colon samples. Moreover, Hes1 expression was found to be correlated with the expression of stem cell markers in colon cancer samples, and Hes1 upregulates the expression of stemness-related genes in colon cancer cells. In addition, Hes1 enhances the self-renewal properties of the stem-like cells by increasing the sizes of CD133+ cells and SP cells and the ability of tumour sphere formation. Additionally, the Hes1-overexpressing cells formed significantly larger and higher number of colonies, as determined through the colony and the soft agar assays. More importantly, Hes1 enhances the tumourigenicity of colon cancer cell lines in nude mice and exhibits a strong tumour-formation ability at a cell density of 1 × 10(3). Taken together, our data indicate that Hes1 induces stem-like cell self-renewal and increases the number of tumour-initiating cells in colon cancer.

Hes1 triggers epithelial-mesenchymal transition (EMT)-like cellular marker alterations and promotes invasion and metastasis of nasopharyngeal carcinoma by activating the PTEN/AKT pathway

Overexpression of the transcriptional factor Hes1 (hairy and enhancer of split-1) has been observed in numerous cancers, but the precise roles of Hes1 in epithelial-mesenchymal transition (EMT), cancer invasion and metastasis remain unknown. Our current study firstly revealed that Hes1 upregulation in a cohort of human nasopharyngeal carcinoma (NPC) biopsies is significantly associated with the EMT, invasive and metastatic phenotypes of cancer. In the present study, we found that Hes1 overexpression triggered EMT-like cellular marker alterations of NPC cells, whereas knockdown of Hes1 through shRNA reversed the EMT-like phenotypes, as strongly supported by Hes1-mediated EMT in NPC clinical specimens described above. Gain-of-function and loss-of-function experiments demonstrated that Hes1 promoted the migration and invasion of NPC cells in vitro. In addition, exogenous expression of Hes1 significantly enhanced the metastatic ability of NPC cells in vivo. Chromatin immunoprecipitation (ChIP) assays showed that Hes1 inhibited PTEN expression in NPC cells through binding to PTEN promoter region. Increased Hes1 expression and decreased PTEN expression were also observed in a cohort of NPC biopsies. Additional studies demonstrated that Hes1-induced EMT-like molecular changes and increased motility and invasion of NPC cells were mediated by PTEN. Taken together, our results suggest, for what we believe is the first time, that Hes1 plays an important role in the invasion and metastasis of NPC through inhibiting PTEN expression to trigger EMT-like phenotypes.

FoxM1 Promotes Cell Proliferation, Invasion, and Stem Cell Properties in Nasopharyngeal Carcinoma

Background: The self-renewal and tumourigenicity of FoxM1 in nasopharyngeal carcinoma (NPC) remain largely unknown. In this study, we attempt to investigate the self-renewal and tumourigenicity of FoxM1 and its clinical significance in nasopharyngeal carcinoma (NPC). Methods: Several assays including cell counting Kit-8 (CCK-8) assays, colony formation, flow cytometry, immunofluorescence, tumor spheres, and mice model were used to detect the biological function of FoxM1 in NPC. The association between FoxM1 and clinical pathological features, and stem cell markers was analyzed using immunohistochemistry. Results: High expression of FoxM1 was prominently present in the T4 stages, cancer cells migrating into the stroma and vasculature. Overexpression of FoxM1 enhanced tumor proliferation, cell cycle progression, migration and stress fibers formation in vitro. In NPC tissues, FoxM1 correlated significantly with stem cells-related clinical pathological features including late clinical stage, tumor recurrence and distant metastasis. Meanwhile, FoxM1 linked closely with the expression levels of stem cell markers including Nanog, Sox2, and OCT4 in tumor samples, and also promoted the expression of these stemness-related genes in vitro. Moreover, FoxM1 conferred the self-renewal properties of cancer cells by increasing side populations (SP) cells and formed larger and more tumor spheres. Importantly, FoxM1 enhanced the ability of tumourigenicity of NPC cell lines in mice xenograft. Conclusions: We demonstrate that FoxM1 greatly induces cancer progression and cancer stem cell (CSC) features in NPC.

Molecular characterization and clinical implications of spindle cells in nasopharyngeal carcinoma: a novel molecule-morphology model of tumor progression proposed

Up to now, the precise molecular and morphological changes underlying the invasive and metastatic properties of nasopharyngeal carcinoma (NPC) remain largely unresolved. We speculate that neoplastic spindle cells, which are prominently found in the invasive tumor front and the surrounding stroma, might be responsible for the aggressive patterns. Expression profiling of various biomarkers relevant to cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT) was performed by tissue microarray-based immunohistochemistry in NPC samples. The expression of EBER and LMP1 was detected by in situ hybridization and immunohistochemistry, respectively. We found that overexpression of CSCs-related markers (ALDH1, Nanog and ABCG2) and up-regulation of EMT markers (Fibronectin, MMP-2, Periostin, SPARC, Snail and Slug), together with E- to N-cadherin switching, occurred preferentially in tumors containing a large proportion of spindle-shaped malignant cells. Furthermore, CSCs-like properties were highly present in spindle cells compared with non-spindle cells of tumors, and correlated strongly with EMT features. In addition, EBV-related factors EBER and LMP1 were highly expressed and correlated strongly with CSCs and EMT characteristics in neoplastic spindle cells. Importantly, high proportion of spindle cells (≥20%) correlated significantly with various aggressive aspects including lymph node metastasis (P = 0.031) and local recurrence (P = 0.014). Patients with high proportion of spindle cells had poor survival (P = 0.004), though it was not an independent value. In conclusion, we demonstrate that spindle cells could be valuable morphological indicators of tumor progression and unfavorable prognosis of NPC. An integrated molecule-morphology model of NPC firstly constructed may shed significant light on the metastatic cascade and clinical relevance of patients.

Matrix metalloproteinase 2 contributes to aggressive phenotype, epithelial-mesenchymal transition and poor outcome in nasopharyngeal carcinoma

BACKGROUND

Though matrix metalloproteinase 2 (MMP-2) involvement in tumor aggressiveness and invasion is well-known, its prognostic impacts still remain largely controversial. Furthermore, the correlations between MMP-2 and epithelial-mesenchymal transition (EMT) have not been directly established in nasopharyngeal carcinoma (NPC).

MATERIALS AND METHODS

The purpose of this study was to investigate MMP-2 expression in NPC. Tissue microarrays from 144 patients with NPC and 45 non-cancerous pharynx tissues were analyzed for MMP-2 expression by immunohistochemistry. MMP-2 expression in relation to clinicopathological characteristics and EMT were assessed in NPC. Tumor-invasive potential affected by exogenous expression of MMP-2 in NPC cells was also detected in vitro.

RESULTS

Compared to normal nasopharyngeal epithelium, high expression of tumoral MMP-2 was detected in 47.9% of NPC samples. Significant association was found between MMP-2 expression and various aggressive features including T classification, M classification and tumor stage (P<0.05). Of note, high expression of MMP-2 was prominently observed at tumor invasive front, neoplastic spindle cells migrating into the stroma and vessel invasion. Importantly, high MMP-2 expression predicted worse survival in patients with stage III-IV (P=0.039). Overexpression of MMP-2 could decrease cell-cell adhesion, promote tumor invasion and EMT including downregulation of E-cadherin and upregulation of N-cadherin, Fibronectin and Slug of NPC cells.

CONCLUSION

Our findings demonstrate that MMP-2 expression contributes to tumor aggressiveness and poor prognosis, and induces the occurrence of EMT in NPC.