Prospero Homeobox 1 Promotes Epithelial–Mesenchymal Transition in Colon Cancer Cells by Inhibiting E-cadherin via miR-9

Abstract

Purpose: Prospero homeobox 1 (PROX1) has been shown to function as a tumor suppressor in various types of cancer. However, it promotes colon cancer progression. The aim of this study is to clarify the underlying mechanism by which PROX1 regulates tumorigenicity of colon cancer.Experimental Design: Association of PROX1 and clinicopathological features was studied by immunohistochemical staining. Pri-miR-9-2 and miR-9 were detected by quantitative real-time PCR. Assays of cell invasion, adhesion, and matrix metalloproteinase activity were used to study PROX1-mediated epithelialmesenchymal transition (EMT).Results: PROX1 was overexpressed in 43% (59/136) of colon cancer tissues and its expression was correlated with E-cadherin downregulation (P ¼ 0.00005), advanced tumor staging (P ¼ 0.005), and lymph node metastasis (P ¼ 0.000009). Enforced expression of PROX1 in DLD-1 cells caused downregulation of Ecadherin and integrins and attenuated cell adhesion. These cells showed increase of matrix metalloproteinase activity and invasive ability. Conversely, knockdown of PROX1 in SW620 cells restored E-cadherin protein expression and reduced invasiveness. Unexpectedly, repression of E-cadherin by PROX1 was not mediated by transcriptional inhibition. We found that PROX1 bound to miR-9-2 promoter and triggered its expression to suppress E-cadherin 3 0 UTR reporter activity and protein expression. Anti-miR-9 restored Ecadherin in SW620 cells, whereas precursor miR-9 inhibited E-cadherin in PROX1-knockdown cells. The miR-9 level was higher in tumor tissues with high PROX1/low E-cadherin than that of tumor tissues with low PROX1/high E-cadherin. Conclusions: Our results provide mechanistic insights by which PROX1 promotes EMT and colon cancer progression. Targeting of PROX1-mediated oncogenic activity may be helpful for the treatment of colon cancer. Clin Cancer Res; 18(23); 6416-25. Ó2012 AACR.

Prospero homeobox 1 mediates the progression of gastric cancer by inducing tumor cell proliferation and lymphangiogenesis

“…There is increasing evidence that EMT is a major contributor to tumor progression and metastasis and is associated with poor clinical outcomes of various cancers [29,30]. A study [31]. Our study showed that PROX1 knockdown increased the adhesion of gastric cancer cells to ECM proteins and decreased their migration.…”

The homeobox transcription factor Prox1 inhibits proliferation of hepatocellular carcinoma cells by inducing p53-dependent senescence-like phenotype

“…We found that Prox1 increased miR-9 expression to inhibit E-cadherin and subsequently enhanced cell invasiveness. 16 Importantly, we also found that Prox1 only controlled the expression of miR-9 in colon cancer cells but not HCC cells. One possible explanation is that Prox1 needs to work with other transcription activators or repressors to exert its function.…”

“…Our recent study showed that Prox1 promotes EMT by downregulating E-cadherin expression in colon cancer cells. 16 We also find that Prox1 increases cell invasiveness by regulating integrins and matrix metalloproteinases. Conversely, defective Prox1 function caused by genomic deletion, mutation, and promoter methylation is generally found in breast cancer, hematological these cells (Fig.…”

MicroRNA signature of inflamed lymphatic endothelium and role of miR-9 in lymphangiogenesis and inflammation

“…The prosurvival protein ZEB1 has been identified as a direct target of miR-200c and miR-141, and ZEB1 is a key molecule involved in the processes of EMT and EndMT that directly suppress E-cadherin (34,40). Downregulation of miR-141 and miR-205 has been implicated in EMT progression, whereas upregulation of miR-21 and miR-9 has been linked to EndMT and EMT, respectively (30,37). Similar expression patterns for these miRNAs (Table 1, Fig.…”