Background: There is emerging molecular evidence concerning the modification of miR expression pattern after the treatment with chemopreventive agents. We investigated whether a potential chemopreventive agent called "Procont" deriving from a biological system has a positive effect on the DMBA induced dysregulation of let7 a, miR21 and miR146a miRNAs. Materials and Methods: CBA/CA H2k inbred mice were fed by Procont for 7 days before the intraperitoneal injection of DMBA. After one week of the beginning of Procont diet we analized the let7a, miR21, miR146a gene expression in vital organs of mice. Results: The Procont feeding significantly decreased all of the investigated miRNA expression compared with either the mice on a normal diet in the control group or mice were exposed to DMBA alone. Conclusion: The results indicate that "Procont" diet has a potential chemopreventive effect in mice exposed to DMBA., Mónika Szirmai, Krisztina Juhász, András Bertha, Katalin Gombos, Katalin Gőcze, Ingrid Magda, Péter Révész, István Ember, and Literatura