Abstracts

Maternal high fat (HF) intake before and/or during pregnancy increases female offsprings mammary cancer risk in several preclinical models. Here I studied if maternal HF intake during pregnancy cause transgenerational increase in mammary cancer risk, and if the increase is reversible by treating adult offspring with inhibitors of histone deacetylases (HDAC) or DNA methyltransferases (DNMT). Pregnant C57BL/6NTac mice were fed either a diet high in n-6 polyunsaturated fatty acids (HF) or control diet (CON). HF diet was given from gestational day (GD) 10 20 to target fetal primordial germ cell formation and differentiation to germ cells. Offspring in subsequent F1-F3 generations were only fed CON diet. Mammary tumor incidence, induced by 7,12-dimethylbenz[a]anthracene (DMBA), was significantly higher in F1 and F3 HF offspring, than in the controls. Tumor latency was shorter and burden higher in F1 HF, with similar trends, though not statistically significant, in F3 HF. RNA-sequencing of normal mammary glands revealed 1587 and 4423 differentially expressed genes between HF and CON offspring in F1 and F3, respectively, of which 48 genes were similarly altered in both generations. Ingenuity Pathway Analysis identified genes associated with Notch signaling as key alterations in HF mammary glands. Knowledge-fused Differential Dependency Network analysis identified 10 node genes in HF offspring uniquely connected to genes linked to increased cancer risk, therapy resistance, poor prognosis, and impaired anti-cancer immunity. Next, I studied whether HDAC and DNMT inhibitor treatment in adulthood of the offspring, prior to tumor formation, could reverse the increased mammary cancer risk caused by in utero HF exposure. CON and HF offspring were given valproic acid and hydralazine in drinking water (epi-treatment), starting one week after tumor initiation by DMBA. Epi-treatment significantly decreased tumor burden in HF offspring, potentially through reactivation of silenced tumor suppressors CLCA1 and CDKN2A, but adversely affected CON offspring. These adverse effects were linked to upregulation of PERK, p62 and HIF-1 in CON. In summary, maternal HF intake during pregnancy induced transgenerational increase in offsprings mammary cancer risk, causes persistent changes in the expression of genes linked to increased breast cancer risk, and epi-treatment in adulthood may reduce this risk.