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Background Treatment failure for breast cancer is frequently due to lymph node metastasis and invasion to neighboring organs. The aim of the present study was to investigate invasion- and metastasis-related genes in breast cancer cells in vitro and in vivo. Identification of new targets will facilitate the developmental pace of new techniques in screening and early diagnosis. Improved abilities to predict progression and metastasis, therapeutic response and toxicity will help to increase survival of breast cancer patients. Methods Differential protein expression in two breast cancer cell lines, one with high and the other with low metastatic potential, was analyzed using two-dimensional liquid phase chromatographic fractionation (Proteome Lab PF 2D system) followed by matrix-assisted laser desorption/time-of-flight mass spectrometry (MALDI-TOF/MS). Results Up regulation of α-subunit of ATP synthase was identified in high metastatic cells compared with low metastatic cells. Immunohistochemical analysis of 168 human breast cancer specimens on tissue microarrays revealed a high frequency of ATP synthase α-subunit expression in breast cancer (94.6%) compared to normal (21.2%) and atypical hyperplasia (23%) breast tissues. Levels of ATP synthase expression levels strongly correlated with large tumor size, poor tumor differentiation and advanced tumor stages (P < 0.05). ATP synthase α-subunit over-expression was detected on the surface of a highly invasive breast cancer cell line. An antibody against the ATP synthase α-subunit inhibited proliferation, migration and invasion in these breast cancer cells but not that of a non-tumor derived breast cell line. Conclusions Over-expression of ATP synthase α-subunit may be involved in the progression and metastasis of breast cancer, perhaps representing a potential biomarker for diagnosis, prognosis and a therapeutic target for breast cancer. This finding of this study will help us to better understand the molecular mechanism of tumor metastasis and to improve the screening, diagnosis, as well as prognosis and/or prediction of responses to therapy for breast cancer.

The purpose of this study was to investigate invasion- and metastasis-related genes in gastric cancer. To this end, we used the transwell system to select a highly invasive subcell line from minimally invasive parent cells and compared gene expression in paired cell lines with high- and low-invasive potentials. Lysyl oxidase-like 2 (LOXL2) was overexpressed in the highly invasive subcell line. Immunohistochemical analysis revealed that LOXL2 expression was markedly increased in carcinoma relative to normal epithelia, and this overexpression in primary tumor was significantly associated with depth of tumor invasion, lymph node metastasis and poorer overall survival. Moreover, LOXL2 expression was further increased in lymph node metastases compared with primary cancer tissues. RNA interference-mediated knockdown and ectopic expression of LOXL2 showed that LOXL2 promoted tumor cell invasion in vitro and increased gastric carcinoma metastasis in vivo. Subsequent mechanistic studies showed that LOXL2 could activate both the Snail/E-cadherin and Src kinase/Focal adhesion kinase (Src/FAK) pathways. However, secreted LOXL2 induced gastric tumor cell invasion and metastasis exclusively via the Src/FAK pathway. Expression correlation analysis in gastric carcinoma tissues also revealed that LOXL2 promoted invasion via the Src/FAK pathway but not the Snail/E-cadherin pathway. We then evaluated secreted LOXL2 as a target for gastric carcinoma treatment and found that an antibody against LOXL2 significantly inhibited tumor growth and metastasis. Overall, our data revealed that LOXL2 overexpression, a frequent event in gastric carcinoma progression, contributes to tumor cell invasion and metastasis, and LOXL2 may be a therapeutic target for preventing and treating metastases.

Esophageal cancer is characterized by rapid clinical progression and poor prognosis due to adjacent tissue invasion and distant organs metastasis at a very early stage. TM4SF3 (transmembrane 4 superfamily 3), a member of tetraspanin family, has been reported as a metastasis associated gene in many types of tumors. Herein, we described new properties of TM4SF3 in tumor metastasis, which suggested that this gene might be involved in esophageal carcinoma metastasis. Western blotting revealed that TM4SF3 was overexpressed in 57.1% (8/14) of esophageal carcinomas and esophageal carcinoma cell lines with high-invasive potential. Exogenous expression of TM4SF3 in two low-invasive esophageal carcinoma cell lines, KYSE150 and EC9706, significantly promoted cell migration and invasion. Upregulating TM4SF3 expression in EC9706 cells promoted xenograft tumor invading into surrounding tissues, enhanced lung metastasis, and shortened the lifespan of mice (median survival EC9706-TM4SF3 106.5 days versus EC9706-Vector 169.0 days, P < 0.0001) in a spontaneous metastasis model. Further studies demonstrated that ADAM12m was upregulated by TM4SF3 overexpression in vitro and in vivo. Abrogating up-expression of ADAM12m by siRNA significantly suppressed TM4SF3-mediated invasion. Together, these data from our studies indicated that overexpression of TM4SF3 in esophageal cancer conferred advantage to the invasion and metastasis of this destructive disease. Upregulated expression of ADAM12m by TM4SF3 might play a key role in TM4SF3-mediated invasion and metastasis. TM4SF3 and ADAM12m might be potential targets of esophageal carcinoma for anti-metastasis therapy.