The forkhead transcription factor Foxp3 is the only definitive marker of CD4(+)CD25(+) regulatory T cells (Tregs) and has been identified as a key regulator in the development and function of Tregs. Foxp3 expression has been reported in a variety of solid tumors, including melanoma. In this study, we validated Foxp3 expression in both tumor-infiltrating Tregs and melanoma cells by performing immunohistochemical analysis of human melanoma tissue sections. Further, we assessed Foxp3 expression in melanoma cell lines by performing flow cytometry, confocal microscopic analysis, reverse transcription-polymerase chain reaction (RT-PCR), and Western blotting. Inhibition of Foxp3 expression in melanoma cells using small interfering RNA (siRNA) resulted in downregulation of B7-H1 and transforming growth factor (TGF)-β expression; in contrast, Foxp3 overexpression resulted in the upregulation of the expression of these proteins. Coculture of Foxp3-expressing melanoma cells with naive CD4(+)CD25(-) T cells resulted in strong inhibition of T-cell proliferation. This antiproliferative effect was partially abrogated by specific inhibition of Foxp3 expression and was effectively enhanced by overexpression of Foxp3. We observed an attenuated antiproliferative effect even when melanoma cells and T cells in the coculture were separated using Transwell inserts. These findings indicated that melanoma cells could have Foxp3-dependent Treg-like suppressive effects on T cells and suggested that the mimicking of Treg function by melanoma cells may represent a possible mechanism of tumor resistance to immune destruction in the melanoma tumor microenvironment.
MicroRNAs (miRNAs) play key roles in cancer development and progression. In the present study, we investigated the role of miR-145 in the progression of hepatocellular carcinoma (HCC). Ten HCC cell lines and samples from 96 patients with HCC were analyzed for the expression of miR-145 by quantitative real-time polymerase chain reaction (qRT-PCR). Overexpression of miR-145 was established by transfecting mimics into HepG2 and QGY-7703 cells. Cell proliferation and cell migration were assessed by cell viability assay and transwell assay. Western blot was to verify ROCK1 as a novel target gene of miR-145. Our results showed that miR-145 was frequently downregulated in HCC tumors and cell lines. Overexpression of miR-145 in HCC cell lines significantly inhibited cell proliferation, migration, and invasion in vitro. ROCK1 was identified as a target of miR-145, and ectopic expression of miR-145 downregulated ROCK1. Together, these findings indicate that miR-145 acts as a tumor suppressor and its downregulation in tumor tissues may contribute to the progression and metastasis of HCC through a mechanism involving ROCK1, suggesting miR-145 as a potential new diagnostic and therapeutic target for the treatment of HCC.
Human vascular endothelia growth factor receptor 3 (VEGFR-3) is up-regulated in a variety of human cancers. It is a potentially rational target for drug delivery. To identify novel ligands with specific binding capabilities to VEGFR-3, we screened a phage display peptide library and found a consensus motif of the peptides which is displayed by the positive phages CSDxxHxWC (x is any amino acid). The phage displaying peptide CSDSWHYWC (designated as P1) exhibited the highest affinity to VEGFR-3 in phage ELISA and the chemically synthesized P1 could bind to VEGFR-3 specifically in a dose-dependent manner. In addition, the flow cytometry assay and immunofluorescence showed that the FITC labelled P1 could bind to VEGFR-3 positive carcinoma cells with specificity. Our study suggests that P1 may be a homing peptide for treatment of tumours.
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