Abstract
Introduction. Epigenetic changes caused by methylation in promoter CpG-islands are a fine and dynamic mechanism of gene expression
regulation in tumors. Increased and decreased expression and alterations in the methylation status of the gene are considered to be primary
criteria for oncogenic or suppressor gene function and prediction of cancer.
The aim of the study. The assessment of the methylation contribution in the regulation of the expression of the functionally important genes
on chromosome 3; the identification of new genes with features of oncogenes or tumor suppressors in breast cancer as prognostic markers.Methods. Samples of tumor and surrounding histologically normal tissues from 69 patients with breast cancer were collected and
clinically characterized. The level of mRNA was determined by semiquantitative RT-PCR. DNA methylation analysis was performed using
two methyl-sensitive restriction endonucleases HpaII and HhaI with following PCR.
Results. For the first time there was studied and shown the dual role of methylation of GPX1, NKIRAS1, RHOA, DAG1 and USP4 with
a prevalence of cases with increased expression, that is characteristic feature of oncogenes. There was established the significant correlation
(p<10-17 according to Spearman’s criteria ) between the alteration of mRNA level and structural modifications (methylation/demethylation
and deletions / amplifications) for GPX1, NKIRAS1 and RHOA, and preliminary for DAG1 and USP4. The methylation contribution in
the deregulation of expression was detected in NKIRAS1 in 69% (18/26), DAG1 – 67% (4/6), USP4 – 83% (5/6), GPX1 – 34% (11/32),
RHOA – 16% (5/32) of breast cancer cases. Oncogenic properties are most pronounced in NKIRAS1, RHOA and DAG1, which have the
increased mRNA level associated with demethylation or amplification.
Conclusion. Firstly the methylation status was shown to be potent to affect on the level of GPX1, NKIRAS1, RHOA, DAG1 and USP4
expression in primary tumors of breast cancer. The features of NKIRAS1, RHOA and DAG1 (mRNA increased level, demethylation or
amplification) can be used for the development of new approaches to the prediction of breast cancer.
Authors and affiliations
V.I. Loginov (1), I.V. Pronina (1), A.M. Burdennyy (1), D.S. Khodyrev (2), T.P. Kazubskaya (3), E.A. Braga (1), A.A. Kubatiev (1), N.E. Kushlinskii (3)
1 -Institute of General Pathology and Pathophysiology, Baltiyskaya str., 8, Moscow, Russian Federation, 125315;
2 -Federal Research Clinical Center of specialized types of medical care and medical technologies, Orekhovyy bul'var, 28, Moscow, Russian Federation, 115682;
3 -N.N. Blokhin Russian Cancer Research Center, Kashirskoe shosse, 24, Moscow, Russian Federation, 115478