The epigenetic role of breastfeeding in the differentiation of breast tissue and the prevention of breast cancer

CAMPO VERDE ARBOCCO, F.; PISTONE CREYDT, V.; BRUNA, F. A.; ZYLA, L.E.; CARON, R.W.; SANTIANO, F.E.; SASSO, C.V.; LÓPEZ-FONTANA, C.M.

San Luis

Congreso; XXXVII Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2019

Sociedad de Biología de Cuyo

Epigenetic processes are essential to determine when and where specific genes are expressed, thus inducing profound changes in the phenotype. Breast milk contains miRNAs responsible for modulating the expression of the infant´s genes. Therefore, breastfeeding can generate an epigenetic imprinting in the infant that modulates the risk of developing diseases such as necrotising enteric colitis, infectious diseases, food allergies, obesity and related disorders, and cancer in adult life. The objective of the present study was to determine if adequate breastfeeding induces changes in the methylation of genes associated with differentiation and / or mammary carcinogenesis in rats. We used Sprague Dawley female in litters of 3 (L3), 8 (L8) or 12 (L12) pups per mother in order to generate a differential consumption of breast milk. At 55 days of age, all animals were sacrificed to study the mammary differentiation. Using real time PCR, we analyzed the expression of mammary PINC, Tbx3, STAT6, GATA3 and PTEN genes. We used a method for MSP (methylation-specific PCR) which can rapidly assess the methylation status of CpG sites within a CpG islands. This assay entails initial modification of DNA by sodium bisulfite, converting all unmethylated cytosines to uracil, and subsequent amplification with primers specific for methylated versus unmethylated DNA. PINC expression has been associated with inhibition of terminal differentiation of mammary alveolar cells. We observed an increased expression of mRNA of PINC in C12 with respect to C3 and C8. The expression of Tbx3, a protein necessary for the normal development of murine mammary epithelium, and GATA3 and STAT6, were significantly diminished in C12 compared to C3. STAT6 stimulates alveolar differentiation and proliferation potentially due to the transcriptional induction of GATA3. The analysis of the methylation profile showed that Stat6 is mainly not methylated in the CpG islands of the promoter analyzed in C12. While in C3, Stat 6 was found mainly methylated. Gata3 is mainly unmethylated in C3, while in C8 and C12 a decrease in nonmethylation was observed. Our results showed that there are differences in the methylation profile of STA6 and GATA3 in the mammary glands of the offspring exposed to different breast milk consumption. These changes could be regulating the activation of gene programs associated with cell differentiation, which may decrease mammary carcinogenesis.