title: Let-7d suppresses growth, metastasis, and tumor macrophage infiltration in renal cell carcinoma by targeting COL3A1 and CCL7.
abstract: BACKGROUND
  MicroRNAs are endogenous small noncoding RNAs that are functionally involved in numerous critical cellular processes including tumorigenesis. Data mining using a microRNA array database suggested that let-7d microRNA may be associated with renal cell carcinoma (RCC) malignant progression. Here, we performed further analyses to determine whether let-7d is functionally linked to RCC malignancy.
  
  
  METHODS
  Quantitative real-time PCR was used to determine the level of mature let-7d in RCC clinical specimens and its correlation with clinicopathological data. Immunohistochemical staining was conducted to characterize the stroma of RCC. Let-7d overexpressing RCC cell lines combined with mouse models bearing cell-derived xenografts and patient-derived xenografts were used to assess the functional role of let-7d in vitro and in vivo.
  
  
  RESULTS
  Downregulation of let-7d in clinical RCC samples was associated with advanced tumor grade and T stage and increased vascular invasion. An inverse relationship between let-7d expression and macrophage infiltration was found in clinical RCC samples. Functional studies indicated that ectopic expression of let-7d significantly inhibited RCC cell proliferation, migration, and peripheral blood monocyte (PBMC) recruitment in vitro, as well as tumor growth, metastasis, and tumor macrophage infiltration in vivo. In silico analysis and subsequent experimental validation confirmed collagen, type III, alpha 1 (COL3A1) and C-C subfamily chemokine member CCL7 as direct let-7d target genes. The addition of COL3A1 and CCL7 counteracted the inhibitory effects of let-7d on RCC cell proliferation, migration, and PBMC recruitment. The inhibition of let-7d increased cell proliferation, migration, and PBMC recruitment by the enhanced expression of COL3A1 and CCL7 genes in vitro. The mRNA levels of COL3A1 and CCL7 were inversely correlated with let-7d level in RCC clinical specimens.
  
  
  CONCLUSIONS
  These results suggest that let-7d may suppress RCC growth, metastasis, and tumor macrophage infiltration at least partially through targeting COL3A1 and CCL7.
authors.forename: Boxing
authors.initials: B
authors.lastname: Su
authors.forename: Wei
authors.initials: W
authors.lastname: Zhao
authors.forename: Bentao
authors.initials: B
authors.lastname: Shi
authors.forename: Zhongyuan
authors.initials: Z
authors.lastname: Zhang
authors.forename: Xi
authors.initials: X
authors.lastname: Yu
authors.forename: Feng
authors.initials: F
authors.lastname: Xie
authors.forename: Zhongqiang
authors.initials: Z
authors.lastname: Guo
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Zhang
authors.forename: Jin
authors.initials: J
authors.lastname: Liu
authors.forename: Qi
authors.initials: Q
authors.lastname: Shen
authors.forename: Jinghua
authors.initials: J
authors.lastname: Wang
authors.forename: Xuesong
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Urology, Peking University First Hospital & the Institute of Urology, Peking University, Beijing 100034, China. zlzqzhang@bjmu.edu.cn.
authors.forename: Zhiqian
authors.initials: Z
authors.lastname: Zhang
authors.forename: Liqun
authors.initials: L
authors.lastname: Zhou
mesh_terms: D000368:Aged; D000818:Animals; D002292:Carcinoma, Renal Cell / Q000235:genetics / Q000473:pathology*; D045744:Cell Line, Tumor; D054410:Chemokine CCL7 / Q000235:genetics*; D024061:Collagen Type III / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007680:Kidney Neoplasms / Q000235:genetics / Q000473:pathology*; D008264:Macrophages / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D016513:Mice, SCID; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism*; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000235:genetics / Q000473:pathology; D009374:Neoplasms, Experimental
chemical_list: C515450:CCL7 protein, human; C439971:COL3A1 protein, human; D054410:Chemokine CCL7; D024061:Collagen Type III; D035683:MicroRNAs; C487931:mirnlet7 microRNA, human