miR-335 promotes cell proliferation by directly targeting Rb1 in meningiomas

Reversible, interrelated mRNA and miRNA expression patterns in the transcriptome of Rasless fibroblasts: functional and mechanistic implications

Background

4-Hydroxy-tamoxifen (4OHT) triggers Cre-mediated K-Ras removal in [H-Ras^-/-;N-Ras^-/-;K-Ras^lox/lox;RERT^ert/ert] fibroblasts, generating growth-arrested “Rasless” MEFs which are able to recover their proliferative ability after ectopic expression of Ras oncoproteins or constitutively active BRAF or MEK1.

Results

Comparison of the transcriptional profiles of Rasless fibroblasts with those of MEFs lacking only H-Ras and N-Ras identified a series of differentially expressed mRNAs and microRNAs specifically linked to the disappearance of K-Ras from these cells. The rescue of cell cycle progression in Rasless cells by activated BRAF or MEK1 resulted in the reversal of most such transcriptional mRNA and microRNA alterations.

Functional analysis of the differentially expressed mRNAs uncovered a significant enrichment in the components of pathways regulating cell division, DNA/RNA processing and response to DNA damage. Consistent with G1/S blockade, Rasless cells displayed repression of a series of cell cycle-related genes, including Cyclins, Cyclin-dependent kinases, Myc and E2F transcription targets, and upregulation of Cyclin-dependent kinase inhibitors. The profile of differentially expressed microRNAs included a specific set of oncomiR families and clusters (repressed miR-17 ~ 92, miR-106a ~ 363, miR-106b ~ 25, miR-212 ~ 132, miR-183 ~ 182, and upregulated miR-335) known for their ability to target a specific set of cellular regulators and checkpoint sensors (including Rb, E2F and Cdkns) able to modulate the interplay between the pro- and anti-proliferative or stress-response pathways that are reversibly altered in Rasless cells.

Conclusions

Our data suggest that the reversible proliferation phenotype of Rasless cells is the pleiotropic result of interplay among distinct pro- and anti-proliferative, and stress-response pathways modulated by a regulatory circuitry constituted by a specific set of differentially expressed mRNAs and microRNAs and preferentially targeting two cross-talking signalling axes: Myc-Rb-E2F-dependent and Cdkns-p53-dependent pathways.

miR-335 suppresses migration and invasion by targeting ROCK1 in osteosarcoma cells

Accumulating evidence has shown that microRNAs are involved in multiple processes in cancer development and progression. Recently, miR-335 has been identified as a tumor-suppressing microRNA in many human cancers. However, the specific function of miR-335 in osteosarcoma is unclear at this point. In this study, we found that the expression of miR-335 in osteosarcoma tissues and cell lines was much lower than that in normal control, respectively, and the downregulated miR-335 was significantly associated with lymph-node metastasis. Transfection of miR-335 mimics could significantly inhibit the cell migration and invasion in MG-63 and U2OS osteosarcoma cell lines. Moreover, we also showed that ROCK1 was negatively regulated by miR-335 at the posttranscriptional level, via a specific target site within the 3'UTR by luciferase reporter assay. The expression of ROCK1 was inversely correlated with miR-335 expression in osteosarcoma tissues, and knockdown of ROCK1 by siRNA-inhibited osteosarcoma cells migration and invasion resembling that of miR-335 overexpression. Thus, our findings suggest that miR-335 acts as tumor suppressor by targeting the ROCK1 gene and inhibiting osteosarcoma cells migration and invasion. The findings of this study contribute to current understanding of the functions of miR-335 in osteosarcoma.

Effect of miR-335 upregulation on the apoptosis and invasion of lung cancer cell A549 and H1299

MicroRNAs are small non-coding RNAs that may also function as oncogenes and tumor-suppressor genes, as the abnormal expression of microRNAs is associated with various human tumors. However, the effect of miR-335 on the lung cancer cells remains unclear. The aim of the paper was to study the expression of miR335 in non-small cell lung cancer (NSCLC) and miR335's relation to the metastasis, invasion, and apoptosis in lung cancer cells A549 and H1299. qRT-PCR was used to identify the miR-335 expression. The effects of miR-335 on cell proliferation, apoptosis, and invasion were further analyzed. Luciferase reporter assay and Western blot were to verify Bcl-w and SP1 as potential major target genes of miR-335. Finally, the effect of Bcl-w on miR-335-induced cell survival was determined. Our results showed that miR-335 expression was significantly lower in NSCLC tissue, which was significantly associated with lymph node metastasis. In contrast to cells in blank and negative control groups, incidence of apoptosis was significantly higher (P < 0.05) and the number of cells migrating through matrigel was significantly lower (P < 0.05) in miR-335 mimics transfected group. Western blot and luciferase reporter assay demonstrated that miR-335 could bind to the putative binding sites in Bcl-w (or SP1) mRNA 3'-untranslated region to visibly lower the expression of Bcl-w (or SP1). The introduction of Bcl-w cDNA without 3'-untranslated region abrogated miR-335-induced cell survival. These results indicated that upregulation of miR-335 can simultaneously suppress the invasiveness and promote apoptosis of lung cancer cell A549 and H1299 by targeting Bcl-w and SP1. Therefore, miR-335 may be a potential therapeutic target in NSCLC treatment.