CXCL16 and CXCR6 are coexpressed in human lung cancer in vivo and mediate the invasion of lung cancer cell lines in vitro.

Weidong Hu,Liang Ren,Yue Liu,Wenhui Zhou,Lianlian Si,Vladimir V Kalinichenko

doi:10.1371/journal.pone.0099056

Abstract

Despite advances in early diagnosis and multimodality therapy for cancers, most of lung cancer patients have been locally advanced or metastatic at the time of diagnosis, suggesting the highly progressive characteristic of lung cancer cells. The mechanisms underling invasiveness and metastasis of lung cancer are yet to be elucidated. In the present study, immunohistochemistry was performed to detect the expression of CXCL16-CXCR6 in human lung cancer tissues. It was demonstrated that similar to CXCL12 and CXCR4, CXCL16 and CXCR6 were also coexpressed in human primary lung cancer tissues. After confirming the functional existence of CXCL16 and CXCR6 protein in A549, 95D and H292 cells by ELSA and flow cytometry analysis, we further explored the significance of CXCL16-CXCR6 axis in the biological functions of lung cancer cell lines in vitro. It was found that CXCL16 had no effects on the PCNA (proliferating cell nuclear antigen) expression of A549, 95D and H292 cells. However, both exogenous CXCL16 and CM (conditioned medium from A549, 95D or H292) significantly improved the in vitro viability and invasion of three lung cancer cell lines. The neutralizing antibody to CXCL16 or down-regulation of CXCR6 was able to inhibit the increased viability and invasiveness of A549, 95D and H292 cells stimulated by CXCL16 or CM. Our results imply that CXCL16-CXCR6 axis is involved in the regulation of viability and invasion rather than PCNA expression of lung caner cells, which opens the door for better understanding the mechanisms of lung tumor progression and metastasis.

Highlights

Lung cancer is a common malignant tumor which ranks as the leading cause of malignancy-related death worldwide, and the incidence of lung cancer has been increasing in recent years in some big cities in China [1]
Our previous study confirmed the excessive expression of CXCR6 protein in human native prostate cancer cells and the activation of CXCL16-CXCR6 pathway could promote the migration and invasion of PC3 and LNcap cells in vitro [19]. These results suggest that CXCL16-CXCR6 may be a novel chemokine ligand/receptor pairs implicated in tumorigenesis and metastasis
Moderateto-strong, brown-coloured staining for CXCL16 and CXCR6 was observed in normal lung tissues, but the positive expression was mainly restricted to the alveolar epithelial cells and inflammatory cells

Summary

Introduction

Lung cancer is a common malignant tumor which ranks as the leading cause of malignancy-related death worldwide, and the incidence of lung cancer has been increasing in recent years in some big cities in China [1]. Despite advances in early diagnosis and multimodality therapy for cancers, the five-year overall survival rate for most advanced lung cancer patients is still less than 20%. The mechanisms underling invasiveness and metastasis of lung cancer have attracted a lot of attentions from thoracic oncologists for decades of years. Some hypotheses and molecules have been put forward, but a thorough understanding of the intricate invasive and metastatic processes of carcinoma cells is still an open question. Activation of chemokine/receptor signal pathway has been confirmed to mediate a series of physiological and pathological events, especially the recruitment of lymphocyte as well as tumor growth and metastatic spread, which provides the possibility for the elucidation of metastatic process of malignant cells from the immunology perspectives [2,3,4,5,6]

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Results

Conclusion