Over-expression of lipocalin 2 promotes cell migration and invasion through activating ERK signaling to increase SLUG expression in prostate cancer.
BACKGROUND
Metastasis is the primary cause of prostate cancer (PCa) lethality and poses a huge clinical obstacle. Lipocalin 2 (LCN2), a member of the lipocalin family, is aberrantly expressed in some human cancers and has been implicated in the progression of some tumors. However, the role of LCN2 in the metastatic capacity of prostate cancer (PCa) is poorly understood.


METHODS
LCN2 expression was examined by RT-qPCR and/or immunoblotting in human prostate tissue specimens and prostate cancer cell lines LNCaP, C4-2, 22RV1, PC3, DU-145, and PC3MM2. LCN2 protein level in human serum samples was determined by ELISA. Lentiviruses-mediated over-expression of LCN2 and knockdown of LCN2 was conducted to evaluate the role of LCN2 in cell migratory and invasive capacities of prostate cancer cells. Cell migration and invasion was examined by transwell chamber assay. Knockdown of SLUG by lentivirus was performed to investigate its role in LCN2-promoted cell migration and invasion in vitro (22RV1 cell line) and metastasis in vivo (tail vein metastasis assay in nude mice). Role of ERK signaling in LCN2-mediated up-regulation of SLUG was assayed by using ERK inhibitor U0126.


RESULTS
We confirmed that LCN2 levels were correlated positively with invasive prostate cancer in human tissue and serum samples, and were also consistently associated with the invasive capacity of prostate cancer cell lines. The over-expression of LCN2 in 22RV1 cells (not highly invasive) promoted the epithelial-mesenchymal transition (EMT), increasing cell motility and invasiveness, while the knockdown of LCN2 in PC3 cells (highly invasive) inhibited EMT, decreasing cell motility and invasiveness. Among the multiple EMT transcription factors, LCN2 specifically induces the expression of SLUG, which was shown here to be required for the LCN2-induced increase in the invasive capacity of prostate cancer cells both in vitro and in vivo. Mechanistically, LCN2 promoted SLUG expression via activating ERK signaling pathway.


CONCLUSIONS
LCN2 plays an important role in promoting cell migration and invasion of prostate cancer by inducing EMT through the ERK/SLUG axis. Therefore, targeted inhibition of LCN2 may represent a therapeutic strategy to prevent the metastasis of prostate cancer.
Department of Urology, Huashan Hospital, Fudan University, Shanghai, China.
Guanxiong
G
Ding
Jie
J
Fang
Shijun
S
Tong
Lianxi
L
Qu
Haowen
H
Jiang
Qiang
Q
Ding
Jun
J
Liu
D000209:Acute-Phase Proteins / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D058750:Epithelial-Mesenchymal Transition; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D064593:Heterografts; D006651:Histocytochemistry; D006801:Humans; D000071068:Lipocalin-2; D054834:Lipocalins / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009361:Neoplasm Invasiveness; D009570:Nitriles / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000097:blood / Q000235:genetics / Q000473:pathology*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics; D012313:RNA / Q000737:chemistry / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics
D000209:Acute-Phase Proteins; D002070:Butadienes; D004791:Enzyme Inhibitors; C489506:LCN2 protein, human; D000071068:Lipocalin-2; D054834:Lipocalins; D009570:Nitriles; D011518:Proto-Oncogene Proteins; C000604407:SNAI1 protein, human; C000604449:Snai2 protein, mouse; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; C113580:U 0126; D012313:RNA; D048049:Extracellular Signal-Regulated MAP Kinases
EMT; ERK; LCN2; SLUG; prostate cancer