miR-342 regulates BRCA1 expression through modulation of ID4 in breast cancer.
A miRNAs profiling on a group of familial and sporadic breast cancers showed that miRNA-342 was significantly associated with estrogen receptor (ER) levels. To investigate at functional level the role of miR-342 in the pathogenesis of breast cancer, we focused our attention on its "in silico" predicted putative target gene ID4, a transcription factor of the helix-loop-helix protein family whose expression is inversely correlated with that of ER. ID4 is expressed in breast cancer and can negatively regulate BRCA1 expression. Our results showed an inverse correlation between ID4 and miR-342 as well as between ID4 and BRCA1 expression. We functionally validated the interaction between ID4 and miR-342 in a reporter Luciferase system. Based on these findings, we hypothesized that regulation of ID4 mediated by miR-342 could be involved in the pathogenesis of breast cancer by downregulating BRCA1 expression. We functionally demonstrated the interactions between miR-342, ID4 and BRCA1 in a model provided by ER-negative MDA-MB-231 breast cancer cell line that presented high levels of ID4. Overexpression of miR-342 in these cells reduced ID4 and increased BRCA1 expression, supporting a possible role of this mechanism in breast cancer. In the ER-positive MCF7 and in the BRCA1-mutant HCC1937 cell lines miR-342 over-expression only reduced ID4. In the cohort of patients we studied, a correlation between miR-342 and BRCA1 expression was found in the ER-negative cases. As ER-negative cases were mainly BRCA1-mutant, we speculate that the mechanism we demonstrated could be involved in the decreased expression of BRCA1 frequently observed in non BRCA1-mutant breast cancers and could be implicated as a causal factor in part of the familial cases grouped in the heterogeneous class of non BRCA1 or BRCA2-mutant cases (BRCAx). To validate this hypothesis, the study should be extended to a larger cohort of ER-negative cases, including those belonging to the BRCAx class.
Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy ; Molecular Genetics of Cancer, Fondazione Istituto FIRC di Oncologia Molecolare, Milano, Italy.
Elisabetta
E
Crippa
Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy ; Molecular Genetics of Cancer, Fondazione Istituto FIRC di Oncologia Molecolare, Milano, Italy ; Institute for Biostatistics and Medical Informatics, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
Lara
L
Lusa
Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy ; Molecular Genetics of Cancer, Fondazione Istituto FIRC di Oncologia Molecolare, Milano, Italy.
Loris
L
De Cecco
Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy ; Molecular Genetics of Cancer, Fondazione Istituto FIRC di Oncologia Molecolare, Milano, Italy.
Edoardo
E
Marchesi
Department of Experimental Therapeutics and The Center for RNA Interference and Non-Coding RNAs, The University of Texas, M. D. Anderson Cancer Center, Houston, Texas, United States of America.
George Adrian
GA
Calin
Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy ; Molecular Genetics of Cancer, Fondazione Istituto FIRC di Oncologia Molecolare, Milano, Italy.
Paolo
P
Radice
Unit of Medical Genetics, Department of Preventive and Predictive Medicine, Fondazione IRCCS Istituto Nazionale Tumori, Milano, Italy.
Siranoush
S
Manoukian
Unit of Medical Genetics, Department of Preventive and Predictive Medicine, Fondazione IRCCS Istituto Nazionale Tumori, Milano, Italy.
Bernard
B
Peissel
Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
Maria Grazia
MG
Daidone
Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy ; Molecular Genetics of Cancer, Fondazione Istituto FIRC di Oncologia Molecolare, Milano, Italy.
Manuela
M
Gariboldi
Scientific Directorate, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
Marco Alessandro
MA
Pierotti
D019313:BRCA1 Protein / Q000378:metabolism*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics / Q000502:physiology*; D020868:Gene Silencing; D006801:Humans; D051796:Inhibitor of Differentiation Proteins / Q000235:genetics / Q000378:metabolism*; D008156:Luciferases; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D046228:Microarray Analysis; D010957:Plasmids / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism
D019313:BRCA1 Protein; D051796:Inhibitor of Differentiation Proteins; D008156:Luciferases; D035683:MicroRNAs; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; C492913:BRCA1 protein, human; C490128:ID4 protein, human; C581863:Mirn342 microRNA, mouse; C508053:ERBB2 protein, human