[show abstract][hide abstract] ABSTRACT: The microRNA 125b is a double-faced gene expression regulator described both as a tumor suppressor gene (in solid tumors) and an oncogene (in hematologic malignancies). In human breast cancer, it is one of the most down-regulated miRNAs and is able to modulate ERBB2/3 expression. Here, we investigated its targets in breast cancer cell lines after miRNA-mimic transfection. We examined the interactions of the validated targets with ERBB2 oncogene and the correlation of miR-125b expression with clinical variables.
MiR-125b possible targets were identified after transfecting a miRNA-mimic in MCF7 cell line and analyzing gene expression modifications with Agilent microarrays and Sylamer bioinformatic tool. Erythropoietin (EPO) and its receptor (EPOR) were validated as targets of miR-125b by luciferase assay and their expression was assessed by RT-qPCR in 42 breast cancers and 13 normal samples. The molecular talk between EPOR and ERBB2 transcripts, through miR-125b, was explored transfecting MDA-MD-453 and MDA-MB-157 with ERBB2 RNA and using RT-qPCR.
We identified a panel of genes down-regulated after miR-125b transfection and putative targets of miR-125b. Among them, we validated erythropoietin (EPO) and its receptor (EPOR) - frequently overexpressed in breast cancer - as true targets of miR-125b. Moreover, we explored possible correlations with clinical variables and we found a down-regulation of miR-125b in metastatic breast cancers and a significant positive correlation between EPOR and ERBB2/HER2 levels, that are both targets of miR-125b and function as competing endogenous RNAs (ceRNAs).
Taken together our results show a mechanism for EPO/EPOR and ERBB2 co-regulation in breast cancer and confirm the importance of miR-125b in controlling clinically-relevant cancer features.
Molecular Cancer 10/2013; 12(1):130. · 5.13 Impact Factor
[show abstract][hide abstract] ABSTRACT: The recently discovered mitochondrial calcium uniporter (MCU) promotes Ca(2+) accumulation into the mitochondrial matrix [1, 2]. We identified in silico miR-25 as a cancer-related MCU-targeting microRNA family and demonstrate that its overexpression in HeLa cells drastically reduces MCU levels and mitochondrial Ca(2+) uptake, while leaving other mitochondrial parameters and cytosolic Ca(2+) signals unaffected. In human colon cancers and cancer-derived cells, miR-25 is overexpressed and MCU accordingly silenced. miR-25-dependent reduction of mitochondrial Ca(2+) uptake correlates with resistance to apoptotic challenges and can be reversed by anti-miR-25 overexpression. Overall, the data demonstrate that microRNA targeting of mitochondrial Ca(2+) signaling favors cancer cell survival, thus providing mechanistic insight into the role of mitochondria in tumorigenesis and identifying a novel therapeutic target in neoplasia.
Current biology: CB 12/2012; · 10.99 Impact Factor
[show abstract][hide abstract] ABSTRACT: Sensory perception can be influenced by cognitive functions like attention and expectation. An emblematic case of this is the placebo effect, where a reduction in pain perception can be obtained by inducing expectation of benefit following a treatment. The current study assessed the behavioural and brain activity correlates of a placebo procedure inducing an enhancement of non-noxious somatic sensation. An experimental group was verbally suggested and surreptitiously conditioned about the effect of an inert cream in enhancing tactile perception, while a control group was informed about the actual inefficacy of the cream. Both groups received non-noxious electric shocks activating A-Beta fibres on the right index finger, before and after application of the cream in the same site. The behavioural and neurophysiological effects of this procedure were measured by a numerical rating scale of subjective perception and by recording cortical and subcortical somatosensory-evoked potentials (SEPs). Although the intensity of stimulation was physically identical in the two sessions, the experimental group reported stronger tactile sensation after cream treatment than before. In parallel, the experimental group showed enhanced somatosensory cortical responses (N140, P200) after treatment, whereas subcortical and early-cortical SEP components did not change. We suggest that these findings reflect top-down modulation on tactile perception probably due to an interplay between expectation and attention and might rely on interactions between prefrontal and parietal brain regions.
[show abstract][hide abstract] ABSTRACT: MicroRNA-221 (miR-221) is one of the most frequently and consistently up-regulated microRNAs (miRNAs) in human cancer. It has been hypothesized that miR-221 may act as a tumor promoter. To demonstrate this, we developed a transgenic (TG) mouse model that exhibits an inappropriate overexpression of miR-221 in the liver. Immunoblotting and immunostaining confirmed a concomitant down-regulation of miR-221 target proteins. This TG model is characterized by the emergence of spontaneous nodular liver lesions in approximately 50% of male mice and by a strong acceleration of tumor development in 100% of mice treated with diethylnitrosamine. Similarly to human hepatocellular carcinoma, tumors are characterized by a further increase in miR-221 expression and a concomitant inhibition of its target protein-coding genes (i.e., cyclin-dependent kinase inhibitor [Cdkn]1b/p27, Cdkn1c/p57, and B-cell lymphoma 2-modifying factor). To validate the tumor-promoting effect of miR-221, we showed that in vivo delivery of anti-miR-221 oligonucleotides leads to a significant reduction of the number and size of tumor nodules. CONCLUSIONS: This study not only establishes that miR-221 can promote liver tumorigenicity, but it also establishes a valuable animal model to perform preclinical investigations for the use of anti-miRNA approaches aimed at liver cancer therapy.