Pulmonary Adenocarcinoma in Malignant Pleural Effusion Enriches Cancer Stem Cell Properties during Metastatic Cascade

Abstract

BackgroundMetastasis occurs in a series of discrete steps involving invasion, angiogenesis, lymphovascular space permeation, and establishment of secondary tumors. Malignant pleural effusion (MPE), a type of tumor metastasis, is usually a poor prognostic sign for patients with pulmonary adenocarcinoma, although its underlying mechanism has received less attention than other types of metastases have. The objective of the current study was to confirm whether cancer stem cells (CSCs) in MPE contribute to the “metastatic cascade” through the epithelial – mesenchymal transition (EMT), anoikis, and adaptation in the microenvironment.MethodsPulmonary tissue and corresponding cell blocks of MPE samples from 20 patients with primary adenocarcinoma were analyzed by immunohistochemical staining with CSC-representative markers (CD133, Nanog, and OCT-4) and EMT-associated markers (E-cadherin and vimentin). Correlations between these variables and clinico-pathological parameters were analyzed. Primary cultures from eight cases of MPE were investigated to characterize the CSC properties, including marker expression, sphere formation, and differentiation.ResultsExpressions of CSC-representative markers for 20 cases of MPE cell blocks were quite diverse and variable ranging from 15% to 90%. Stronger expression of CSC-representative markers and alteration of EMT-associated markers were found at the invasive fronts and in MPEs compared with the expression in primary pulmonary tumor tissues. The expression of OCT-4 in MPEs significantly related to distant metastasis and stage, as well as inversely correlated with patient survival. Primary cultures confirmed the CSC properties in MPE. Five of eight cases of MPE yielded adequate cell clusters, which also showed variable expressions of CSC markers in addition to sphere formation and the ability for differentiation and metastasis.ConclusionThis pilot study offers a better understanding of the metastatic cascade. Establishing a model of MPE will provide further insight into the role of CSCs in metastasis and may explain the high therapeutic failure rates for patients with MPE.

Malignant Pleural Effusion and ascites Induce Epithelial-Mesenchymal Transition and Cancer Stem-like Cell Properties via the Vascular Endothelial Growth Factor (VEGF)/Phosphatidylinositol 3-Kinase (PI3K)/Akt/Mechanistic Target of Rapamycin (mTOR) Pathway

“…We found here, from clinical specimens and in vitro experiments, that cancer cells in malignant PE/ascites underwent EMT and displayed a cancer stem cells phenotype, which could account for the poor prognosis. Here, besides confirming the phenomena described previously (9,19,20), we also found that malignant exudates had universal induction activity regardless of tumor type and origin. More importantly, we noted that non-CSCs could undergo EMT process and be directly converted into the CSC state when exposed to malignant PE/ascites; therefore, blocking the process in combination with conventional chemotherapies is critical to better control malignant PE/ascites.…”

“…EMT and gain a stem cell phenotype within malignant PE/ascites (9,19,20). So far, however, there are no available strategies to inhibit these processes because the underlying mechanisms are barely understood.…”

Immunohistochemical analysis of NANOG expression and epithelial-mesenchymal transition in pulmonary sarcomatoid carcinoma

“…In addition, no statistically significant difference was observed between the two groups in terms of the expression of Snail-1/Snail-2 and p-p38 MAPK, which are major signal transducing molecules in EMT. A previous study provides one possible explanation for the reduced expression of NANOG observed in PSC: Chen et al (36) assessed the expression of NANOG in primary tumours at the frontline between tumour and normal tissue, and in malignant pleural effusions of PA, demonstrating that a situation-dependent up-regulation of the NANOG gene occurred at the frontline of tumour progression compared with quiescent areas. According to the hypothesis of Chen et al (36), quiescent tumour cells obtained from PSC may express only small amounts of NANOG.…”

Clinical significance of tumor cells and CD133+ cells from malignant pleural effusion in patients with lung cancer

“…Nearly 15% of newly diagnosed lung cancer patients have pleural effusion, and 40–50% of lung cancer patients will have pleural effusion during disease progression. Malignant pleural effusion has a complex composition, containing a small number of tumor cells and cancer stem cells (CSCs) . In pleural effusions, lymphocytes account for 50–70% of all nucleated cells.…”