Cancer-associated fibroblasts (CAFs) play crucial roles in tumor progression, given the dependence of cancer cells on stromal support. Therefore, understanding how CAFs communicate with endometrial cancer cell in tumor environment is important for endometrial cancer therapy. Exosomes, which contain proteins and noncoding RNA, are identified as an important mediator of cell-cell communication. However, the function of exosomes in endometrial cancer metastasis remains poorly understood. In the current study we found that CAF-derived exosomes significantly promoted endometrial cancer cell invasion comparing to those from normal fibroblasts (NFs). We identified a significant decrease of miR-148b in CAFs and CAFs-derived exosomes. By exogenously transfect microRNAs, we demonstrated that miR-148b could be transferred from CAFs to endometrial cancer cell through exosomes. In vitro and in vivo studies further revealed that miR-148b functioned as a tumor suppressor by directly binding to its downstream target gene, DNMT1 to suppress endometrial cancer metastasis. In endometrial cancer DNMT1 presented a potential role in enhancing cancer cell metastasis by inducing epithelial-mesenchymal transition (EMT). Therefore, downregulated miR-148b induced EMT of endometrial cancer cell as a result of relieving the suppression of DNMT1. Taken together, these results suggest that CAFs-mediated endometrial cancer progression is partially related to the loss of miR-148b in the exosomes of CAFs and promoting the transfer of stromal cell-derived miR-148b might be a potential treatment to prevent endometrial cancer progression.

ObjectiveEFEMP1, the epidermal growth factor–containing fibulin-like extracellular matrix protein 1, functions as an oncogene or a tumor suppressor depending on the cancer types. In this study, we aim to determine whether EFEMP1 affects the tumorigenesis and progression of endometrial carcinoma.MethodsThe expression of EFEMP1 was investigated using immunohistochemistry in a panel of normal endometrium (n = 40), atypical hyperplasia (n = 10) and endometrial carcinoma tissues (n = 84). Methylation status of the EFEMP1 promoter was detected by methylation-specific PCR (MSP) and bisulphite genomic sequencing. Up- or down-regulation of EFEMP1 were achieved by stable or transient transfection with pCMV6/GFP/Neo-EFEMP1 or pGPU6/GFP/Neo-shEFEMP1 respectively. Effects of EFEMP1 on tumor proliferation, invasion and migration were evaluated by MTT, plate colony formation, Transwell and wound healing assay. The nude mouse tumor xenograft assay was used to investigate function of EFEMP1 in vivo.ResultsCompared with normal endometrium (32/40) and atypical hyperplasia (7/10), EFEMP1 expression was much lower in endometrial carcinoma tissues (16/84) (P<0.001 and P = 0.02). EFEMP1 promoter was hypermethylated in endometrial carcinoma tissues (67%) as compared to normal tissue (10%) and down-regulation of EFEMP1 was associated with promoter hypermethylation. Treatment with 5-aza-2′-deoxycytidine (5-aza-dC) and/or trichostatin A (TSA) altered EFEMP1 methylation status, and restored EFEMP1 expression. Moreover, EFEMP1 decreased secretion of MMPs and inhibited tumor cell proliferation, metastasis and invasion in vitro and suppressed tumorigenesis in nude mice. Besides, EFEMP1 increased expression of E-cadherin and suppressed expression of vimentin in endometrial carcinoma.ConclusionEFEMP1 is a new candidate tumor suppressor gene in endometrial carcinoma, and is frequently silenced by promoter hypermethylation. It could inhibit tumor growth and invasion both in vitro and in vivo. Our findings propose that targeting EFEMP1 might offer future clinical utility in endometrial carcinoma.

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