Transcriptional implications of intragenic DNA methylation in the oestrogen receptor alpha gene in breast cancer cells and tissues

ERα prevents tumorigenesis of both liver and breast cancer cells through CCN5

Estrogen receptor alpha (ERα)-mediated estrogen signaling has also shown to prevent hepatic tumorigenesis in mice. Consistent with this, hormone replacement therapy with estrogen supplementation dramatically reduced the risk of hepatocellular carcinoma. Silencing of ERα is also a key event for the transformation of ERα-positive breast cancer cells into malignant triple-negative breast cancer cells. However, the mechanisms underlying ERα-mediated prevention of both hepatic and mammary tumorigenesis in humans are still unclear. Here, we present a functional genomics study of ERα targeting by comparing human liver cancer cells with human breast cancer cells using "loss or gain of function" genetic assays of ERα in vitro and in vivo. We discover that cellular communication network factor 5 (CCN5) is a direct downstream target of ERα; ERα suppresses growth and prevents tumorigenesis and malignant transformation of both liver and breast cancer cells through CCN5 in humans. The ERα-CCN5 regulatory axis functions as suppressors for both hepatic and mammary tumors, which is a common mechanism of preventing tumorigenesis for both liver cancer and breast cancer in humans.

Decitabine-induced DNA methylation-mediated transcriptomic reprogramming in human breast cancer cell lines; the impact of DCK overexpression

Decitabine (DAC), a DNA methyltransferase (DNMT) inhibitor, is tested in combination with conventional anticancer drugs as a treatment option for various solid tumors. Although epigenome modulation provides a promising avenue in treating resistant cancer types, more studies are required to evaluate its safety and ability to normalize the aberrant transcriptional profiles. As deoxycytidine kinase (DCK)-mediated phosphorylation is a rate-limiting step in DAC metabolic activation, we hypothesized that its intracellular overexpression could potentiate DAC’s effect on cell methylome and thus increase its therapeutic efficacy. Therefore, two breast cancer cell lines, JIMT-1 and T-47D, differing in their molecular characteristics, were transfected with a DCK expression vector and exposed to low-dose DAC (approximately IC20). Although transfection resulted in a significant DCK expression increase, further enhanced by DAC exposure, no transfection-induced changes were found at the global DNA methylation level or in cell viability. In parallel, an integrative approach was applied to decipher DAC-induced, methylation-mediated, transcriptomic reprogramming. Besides large-scale hypomethylation, accompanied by up-regulation of gene expression across the entire genome, DAC also induced hypermethylation and down-regulation of numerous genes in both cell lines. Interestingly, TET1 and TET2 expression halved in JIMT-1 cells after DAC exposure, while DNMTs’ changes were not significant. The protein digestion and absorption pathway, containing numerous collagen and solute carrier genes, ranking second among membrane transport proteins, was the top enriched pathway in both cell lines when hypomethylated and up-regulated genes were considered. Moreover, the calcium signaling pathway, playing a significant role in drug resistance, was among the top enriched in JIMT-1 cells. Although low-dose DAC demonstrated its ability to normalize the expression of tumor suppressors, several oncogenes were also up-regulated, a finding, that supports previously raised concerns regarding its broad reprogramming potential. Importantly, our research provides evidence about the involvement of active demethylation in DAC-mediated transcriptional reprogramming.

ESR1 Methylation Measured in Cell-Free DNA to Evaluate Endocrine Resistance in Metastatic Breast Cancer Patients

ESR1 methylation was proposed as mechanism for endocrine resistance in metastatic breast cancer patients. To evaluate its potential as a minimally invasive biomarker, we investigated the feasibility of measuring ESR1 methylation in cell-free DNA (cfDNA) and its association with endocrine resistance. First, we provided evidence that demethylation in vitro restores ER expression. Subsequently, we found that ESR1 methylation in cfDNA was not enriched in endocrine-resistant versus endocrine-sensitive patients. Interestingly, we found a correlation between ESR1 methylation and age. Publicly available data confirm an age-related increase in ESR1 methylation in leukocytes, confounding the determination of the ESR1 methylation status of tumors using cfDNA.

A small-molecule activator of the unfolded protein response eradicates human breast tumors in mice

Metastatic estrogen receptor α (ERα)-positive breast cancer is presently incurable. Seeking to target these drug-resistant cancers, we report the discovery of a compound, called ErSO, that activates the anticipatory unfolded protein response (a-UPR) and induces rapid and selective necrosis of ERα-positive breast cancer cell lines in vitro. We then tested ErSO in vivo in several preclinical orthotopic and metastasis mouse models carrying different xenografts of human breast cancer lines or patient-derived breast tumors. In multiple orthotopic models, ErSO treatment given either orally or intraperitoneally for 14 to 21 days induced tumor regression without recurrence. In a cell line tail vein metastasis model, ErSO was also effective at inducing regression of most lung, bone, and liver metastases. ErSO treatment induced almost complete regression of brain metastases in mice carrying intracranial human breast cancer cell line xenografts. Tumors that did not undergo complete regression and regrew remained sensitive to retreatment with ErSO. ErSO was well tolerated in mice, rats, and dogs at doses above those needed for therapeutic responses and had little or no effect on normal ERα-expressing murine tissues. ErSO mediated its anticancer effects through activation of the a-UPR, suggesting that activation of a tumor protective pathway could induce tumor regression.

Methylation of ERβ 5'-untranslated region attenuates its inhibitory effect on ERα gene transcription and promotes the initiation and progression of papillary thyroid cancer

Normal thyroid tissue displays a prevalent expression of ERβ than ERα, which drastically turns upside down in the initiation and progression of papillary thyroid cancer (PTC). The underlying molecular mechanism of this phenomenon remains unclear. Here, we demonstrated that ERα and ERβ were coexpressed in human thyroid tissues and cells. ERα mRNA (A-1) and ERβ mRNA (0N-1), transcribed from Promoter A of ERα gene and Promoter 0N of ERβ gene, respectively, were the major mRNA isoforms which mainly contributed to total ERα mRNA and total ERβ mRNA in human thyroid-derived cell lines and tissues. The expression levels of ERα mRNA (A-1) and total ERα mRNA were gradually increased, and those of ERβ mRNA (0N-1) and total ERβ mRNA were decreased by degree in the initiation and progression of PTC. No aberrant DNA methylation of ERα 5'-untranslated region was involved in its up-regulation; however, aberrant DNA methylation in Promoter 0N and Exon 0N of ERβ gene was found to be involved in its down-regulation in the initiation and progression of PTC. ERβ can repress ERα gene transcription via recruitment of NCoR and displacement of RNA polymerase II at the Sp1 site in ERα Promoter A-specific region in thyroid-derived cells. It is suggested that DNA methylation of CpG islands in Promoter 0N and Exon 0N of ERβ gene leads to a decreased ERβ gene expression, which attenuates its inhibitory effect on ERα gene transcription and results in an increased ERα gene expression, cell proliferation, initiation, and progression of PTC.

Comprehensive analysis based on DNA methylation and RNA-seq reveals hypermethylation of the up-regulated WT1 gene with potential mechanisms in PAM50 subtypes of breast cancer

Background

Breast cancer (BC), one of the most widespread cancers worldwide, caused the deaths of more than 600,000 women in 2018, accounting for about 15% of all cancer-associated deaths in women that year. In this study, we aimed to discover potential prognostic biomarkers and explore their molecular mechanisms in different BC subtypes using DNA methylation and RNA-seq.

Methods

We downloaded the DNA methylation datasets and the RNA expression profiles of primary tissues of the four BC molecular subtypes (luminal A, luminal B, basal-like, and HER2-enriched), as well as the survival information from The Cancer Genome Atlas (TCGA). The highly expressed and hypermethylated genes across all the four subtypes were screened. We examined the methylation sites and the downstream co-expressed genes of the selected genes and validated their prognostic value using a different dataset (GSE20685). For selected transcription factors, the downstream genes were predicted based on the Gene Transcription Regulation Database (GTRD). The tumor microenvironment was also evaluated based on the TCGA dataset.

Results

We found that Wilms tumor gene 1 (WT1), a transcription factor, was highly expressed and hypermethylated in all the four BC subtypes. All the WT1 methylation sites exhibited hypermethylation. The methylation levels of the TSS200 and 1stExon regions were negatively correlated with WT1 expression in two BC subtypes, while that of the gene body region was positively associated with WT1 expression in three BC subtypes. Patients with low WT1 expression had better overall survival (OS). Five genes including COL11A1, GFAP, FGF5, CD300LG, and IGFL2 were predicted as the downstream genes of WT1. Those five genes were dysregulated in the four BC subtypes. Patients with a favorable 6-gene signature (low expression of WT1 and its five predicted downstream genes) exhibited better OS than that with an unfavorable 6-gene signature. We also found a correlation between WT1 and tamoxifen using STITCH. Higher infiltration rates of CD8 T cells, plasma cells, and monocytes were found in the lower quartile WT1 group and the favorable 6-gene signature group. In conclusion, we demonstrated that WT1 is hypermethylated and up-regulated in the four BC molecular subtypes and a 6-gene signature may predict BC prognosis.

DNA methylation and expression of estrogen receptor alpha in fathead minnows exposed to 17α-ethynylestradiol

The gene expression response thought to underlie the negative apical effects resulting from estrogen exposure have been thoroughly described in fish. Although epigenetics are believed to play a critical role translating environmental exposures into the development of adverse apical effects, they remain poorly characterized in fish species. This study investigated alterations of DNA methylation of estrogen receptor alpha (esr1) in brain and liver tissues from 8 to 10 month old male fathead minnows (Pimephales promelas) after a 2d exposure to either 2.5 ng/L or 10 ng/L 17α-ethynylestradiol (EE2). Changes in the patterns of methylation were evaluated using targeted deep sequencing of bisulfite treated DNA in the 5' region of esr1. Methylation and gene expression were assessed at 2d of exposure and after a 7 and 14d depuration period. After 2d EE2 exposure, males exhibited significant demethylation in the 5' upstream region of esr1 in liver tissue, which was inversely correlated to gene expression. This methylation pattern reflected what was seen in females. No gene body methylation (GBM) was observed for liver of exposed males. Differential methylation was observed for a single upstream CpG site in the liver after the 14d depuration. A less pronounced methylation response was observed in the upstream region in brain tissue, however, several CpGs were necessarily excluded from the analysis. In contrast to the liver, a significant GBM response was observed across the entire gene body, which was sustained until at least 7d post-exposure. No differential expression was observed in the brain, limiting functional interpretation of methylation changes. The identification of EE2-dependent changes in methylation levels strongly suggests the importance of epigenetic mechanisms as a mediator of the organismal response to environmental exposures and the need for further characterization of the epigenome. Further, differential methylation following depuration indicates estrogenic effects persist well after the active exposure, which has implications for the risk posed by repeated exposures..

Differences in Genome-wide DNA Methylation Profiles in Breast Milk by Race and Lactation Duration

Black women in the United States are disproportionately affected by early-onset, triple-negative breast cancer. DNA methylation has shown differences by race in healthy and tumor breast tissues. We examined associations between genome-wide DNA methylation levels in breast milk and breast cancer risk factors, including race, to explain how this reproductive stage influences a woman's risk for, and potentially contributes to racial disparities in, breast cancer. Breast milk samples and demographic, behavioral, and reproductive data, were obtained from cancer-free, uniparous, and lactating U.S. black (n = 57) and white (n = 82) women, ages 19-44. Genome-wide DNA methylation analysis was performed on extracted breast milk DNA using the Infinium HumanMethylation450 BeadChip. Statistically significant associations between breast cancer risk factors and DNA methylation beta values, adjusting for potential confounders, were determined using linear regression followed by Bonferroni Correction (P < 1.63 × 10-7). Epigenetic analysis in breast milk revealed statistically significant associations with race and lactation duration. Of the 284 CpG sites associated with race, 242 were hypermethylated in black women. All 227 CpG sites associated with lactation duration were hypomethylated in women who lactated longer. Ingenuity Pathway Analysis of differentially methylated promoter region CpGs by race and lactation duration revealed enrichment for networks implicated in carcinogenesis. Associations between DNA methylation and lactation duration may offer insight on its role in lowering breast cancer risk. Epigenetic associations with race may mediate social, behavioral, or other factors related to breast cancer and may provide insight into potential mechanisms underlying racial disparities in breast cancer incidence.

Blood DNA methylation and breast cancer risk: a meta-analysis of four prospective cohort studies

BACKGROUND

Environmental and genetic factors play an important role in the etiology of breast cancer. Several small blood-based DNA methylation studies have reported risk associations with methylation at individual CpGs and average methylation levels; however, these findings require validation in larger prospective cohort studies. To investigate the role of blood DNA methylation on breast cancer risk, we conducted a meta-analysis of four prospective cohort studies, including a total of 1663 incident cases and 1885 controls, the largest study of blood DNA methylation and breast cancer risk to date.

METHODS

We assessed associations with methylation at 365,145 CpGs present in the HumanMethylation450 (HM450K) Beadchip, after excluding CpGs that did not pass quality controls in all studies. Each of the four cohorts estimated odds ratios (ORs) and 95% confidence intervals (CI) for the association between each individual CpG and breast cancer risk. In addition, each study assessed the association between average methylation measures and breast cancer risk, adjusted and unadjusted for cell-type composition. Study-specific ORs were combined using fixed-effect meta-analysis with inverse variance weights. Stratified analyses were conducted by age at diagnosis (< 50, ≥ 50), estrogen receptor (ER) status (+/-), and time since blood collection (< 5, 5-10, > 10 years). The false discovery rate (q value) was used to account for multiple testing.

RESULTS

The average age at blood draw ranged from 52.2 to 62.2 years across the four cohorts. Median follow-up time ranged from 6.6 to 8.4 years. The methylation measured at individual CpGs was not associated with breast cancer risk (q value > 0.59). In addition, higher average methylation level was not associated with risk of breast cancer (OR = 0.94, 95% CI = 0.85, 1.05; P = 0.26; P for study heterogeneity = 0.86). We found no evidence of modification of this association by age at diagnosis (P = 0.17), ER status (P = 0.88), time since blood collection (P = 0.98), or CpG location (P = 0.98).

CONCLUSIONS

Our data indicate that DNA methylation measured in the blood prior to breast cancer diagnosis in predominantly postmenopausal women is unlikely to be associated with substantial breast cancer risk on the HM450K array. Larger studies or with greater methylation coverage are needed to determine if associations exist between blood DNA methylation and breast cancer risk.

Paternal hyperglycemia induces transgenerational inheritance of susceptibility to hepatic steatosis in rats involving altered methylation on Pparα promoter

OBJECTIVE

Diabetes exerts adverse effects on the initiation or progression of diabetes and metabolic syndrome in the next generation. In past studies, limited attention has been given to the fathers' role in shaping the metabolic landscape of offspring. Our study was designed to investigate how paternal hyperglycemia exerts an intergenerational effect in mammals as well as the underlying mechanisms.

METHODS

Hyperglycemia was introduced in male rats by intraperitoneally injected streptozotocin and these males were bred with healthy females to generate offspring. The metabolic profiles of the progeny were assessed; DNA methylation profiles and gene expression were investigated. Mutagenesis constructs of the Ppara promoter region, and a luciferase reporter assay were used to determine transcription factor binding sites (TFBSs) and the effects of hypermethylation on Ppara transcription.

RESULTS

Paternal hyperglycemia induced increased liver weight, and plasma TC, TG, LDL, accumulation of triglycerides in the liver. We discovered that CpG 13 in the amplified promoter region (-852 to -601) of Ppara was hypermethylated in adult offspring liver and expression of Ppara, Acox1, Cpt-1α, and Cd36 was down regulated. Hypermethylation of CpG site 13 in the Ppara promoter inhibited the gene transcription, probably through abrogation of SP1 binding. The same epigenetic alteration was discovered in the fetus (E16.5) liver of hyperglycemic father's progeny.

CONCLUSIONS

Paternal hyperglycemia may induce epigenetic modification of Ppara in offspring's liver, probably through interaction with SP1 binding, causing impaired lipid metabolism. Our investigation may have implications for the understanding of father-offspring interactions with the potential to account for metabolic syndromes.

Effects of 5-Aza-2'-deoxycytidine (decitabine) on gene expression

5-Aza-2'-deoxycytidine (AzaD), also known as Decitabine, is a deoxycytidine analog that is typically used to activate methylated and silenced genes by promoter demethylation. However, a survey of the scientific literature indicates that promoter demethylation may not be the only (or, indeed, the major) mechanism by which AzaD affects gene expression. Regulation of gene expression by AzaD can occur in several ways, including some that are independent of DNA demethylation. Results from several studies indicate that the effect of AzaD on gene expression is highly context-dependent and can differ for the same gene under different environmental settings. This may, in part, be due to the nature of the silencing mechanism(s) involved - DNA methylation, repressive histone modifications, or a combination of both. The varied effects of AzaD on such context-dependent regulation of gene expression may underlie some of the diverse responses exhibited by patients undergoing AzaD therapy. In this review, we describe the salient properties of AzaD with particular emphasis on its diverse effects on gene expression, aspects that have barely been discussed in most reviews of this interesting drug.

MMP9 gene expression regulation by intragenic epigenetic modifications in breast cancer

Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death among women worldwide. Metastasis remains a major challenge for the clinical management and prognosis of patients with cancer. The metalloprotease MMP-9 plays a critical role in the first step of metastasis through extracellular matrix degradation. In this study, our goal was to determine the effect of epigenetic mechanisms in the promoter and intragenic region of this gene and to correlate it to the levels of expression of MMP9 in breast cancer cell lines. We have identified that MMP9 was highly expressed in the breast cancer cell lines MCF7 and MDA-MB-436 after 5-aza-2'-deoxycytidine (5-azadC) treatment. Sequencing of the promoter region as well as the CGI intronic CpG islands showed a specific sequence in CGI2, between CpGs 12-30 that was demethylated after 5-azadC treatment. This specific region was studied in breast cancer samples that revealed similar results with demethylation in positive MMP-9 breast cancer samples. Furthermore, the histone methylation marker of open chromatin (H3K4me3) was found in the promoter and intronic regions of MMP9 after 5-azadC treatment. Taken together these results showed a mechanism of DNA methylation and gene expression regulation by epigenetic marks present in the intronic DNA region of MMP9.

Platinum-Based Chemotherapy Induces Methylation Changes in Blood DNA Associated with Overall Survival in Patients with Ovarian Cancer

Purpose: DNA damage repair can lead to epigenetic changes. DNA mismatch repair proteins bind to platinum DNA adducts and at sites of DNA damage can recruit the DNA methylating enzyme DNMT1, resulting in aberrant methylation. We hypothesised that DNA damage repair during platinum-based chemotherapy may cause aberrant DNA methylation in normal tissues of patients such as blood.Experimental Design: We used Illumina 450k methylation arrays and bisulphite pyrosequencing to investigate methylation at presentation and relapse in blood DNA from patients with ovarian cancer enrolled in the SCOTROC1 trial (n = 247) and in a cohort of ovarian tumor DNA samples collected at first relapse (n = 46). We used an ovarian cancer cell line model to investigate the role of the DNA mismatch repair gene MLH1 in platinum-induced methylation changes.Results: Specific CpG methylation changes in blood at relapse are observed following platinum-based chemotherapy and are associated with patient survival, independent of other clinical factors [hazard ratio, 3.7; 95% confidence interval, 1.8-7.6, P = 2.8 × 10-4]. Similar changes occur in ovarian tumors at relapse, also associated with patient survival (hazard ratio, 2.6; 95% confidence interval, 1.0-6.8, P = 0.048). Using an ovarian cancer cell line model, we demonstrate that functional mismatch repair increases the frequency of platinum-induced methylation.Conclusions: DNA methylation in blood at relapse following chemotherapy, and not at presentation, is informative regarding survival of patients with ovarian cancer. Functional DNA mismatch repair increases the frequency of DNA methylation changes induced by platinum. DNA methylation in blood following chemotherapy could provide a noninvasive means of monitoring patients' epigenetic responses to treatment without requiring a tumor biopsy. Clin Cancer Res; 23(9); 2213-22. ©2016 AACR.

Inbreeding effects on gene-specific DNA methylation among tissues of Chinook salmon

Inbreeding depression is the loss of fitness resulting from the mating of genetically related individuals. Traditionally, the study of inbreeding depression focused on genetic effects, although recent research has identified DNA methylation as also having a role in inbreeding effects. Since inbreeding depression and DNA methylation change with age and environmental stress, DNA methylation is a likely candidate for the regulation of genes associated with inbreeding depression. Here, we use a targeted, multigene approach to assess methylation at 22 growth-, metabolic-, immune- and stress-related genes. We developed PCR-based DNA methylation assays to test the effects of intense inbreeding on intragenic gene-specific methylation in inbred and outbred Chinook salmon. Inbred fish had altered methylation at three genes, CK-1, GTIIBS and hsp70, suggesting that methylation changes associated with inbreeding depression are targeted to specific genes and are not whole-genome effects. While we did not find a significant inbreeding by age interaction, we found that DNA methylation generally increases with age, although methylation decreased with age in five genes, CK-1, IFN-ɣ, HNRNPL, hsc71 and FSHb, potentially due to environmental context and sexual maturation. As expected, we found methylation patterns differed among tissue types, highlighting the need for careful selection of target tissue for methylation studies. This study provides insight into the role of epigenetic effects on ageing, environmental response and tissue function in Chinook salmon and shows that methylation is a targeted and regulated cellular process. We provide the first evidence of epigenetically based inbreeding depression in vertebrates.

FOXC1 is involved in ERα silencing by counteracting GATA3 binding and is implicated in endocrine resistance

Estrogen receptor-α (ERα) mediates the essential biological function of estrogen in breast development and tumorigenesis. Multiple mechanisms, including pioneer factors, coregulators, and epigenetic modifications have been identified as regulators of ERα signaling in breast cancer. However, previous studies of ERα regulation have focused on luminal and HER2-positive subtypes rather than basal-like breast cancer (BLBC), in which ERα is underexpressed. In addition, mechanisms that account for the decrease or loss of ER expression in recurrent tumors after endocrine therapy remain elusive. Here, we demonstrate a novel FOXC1-driven mechanism that suppresses ERα expression in breast cancer. We find that FOXC1 competes with GATA3 for the same binding regions in the cis-regulatory elements (CREs) upstream of the ERα gene and thereby downregulates ERα expression and consequently its transcriptional activity. The forkhead domain of FOXC1 is essential for the competition with GATA3 for DNA binding. Counteracting the action of GATA3 at the ERα promoter region, overexpression of FOXC1 hinders recruitment of RNA polymerase II and increases histone H3K9 trimethylation at ERα promoters. Importantly, ectopic FOXC1 expression in luminal breast cancer cells reduces sensitivity to estrogen and tamoxifen. Furthermore, in breast cancer patients with ER-positive primary tumors who received adjuvant tamoxifen treatment, FOXC1 expression is associated with decreased or undetectable ER expression in recurrent tumors. Our findings highlight a clinically relevant mechanism that contributes to the low or absent ERα expression in BLBC. This study suggests a new paradigm to study ERα regulation during breast cancer progression and indicates a role of FOXC1 in the modulation of cellular response to endocrine treatment.

Milk: an epigenetic amplifier of FTO-mediated transcription? Implications for Western diseases

Single-nucleotide polymorphisms within intron 1 of the FTO (fat mass and obesity-associated) gene are associated with enhanced FTO expression, increased body weight, obesity and type 2 diabetes mellitus (T2DM). The N⁶-methyladenosine (m⁶A) demethylase FTO plays a pivotal regulatory role for postnatal growth and energy expenditure. The purpose of this review is to provide translational evidence that links milk signaling with FTO-activated transcription of the milk recipient. FTO-dependent demethylation of m⁶A regulates mRNA splicing required for adipogenesis, increases the stability of mRNAs, and affects microRNA (miRNA) expression and miRNA biosynthesis. FTO senses branched-chain amino acids (BCAAs) and activates the nutrient sensitive kinase mechanistic target of rapamycin complex 1 (mTORC1), which plays a key role in translation. Milk provides abundant BCAAs and glutamine, critical components increasing FTO expression. CpG hypomethylation in the first intron of FTO has recently been associated with T2DM. CpG methylation is generally associated with gene silencing. In contrast, CpG demethylation generally increases transcription. DNA de novo methylation of CpG sites is facilitated by DNA methyltransferases (DNMT) 3A and 3B, whereas DNA maintenance methylation is controlled by DNMT1. MiRNA-29s target all DNMTs and thus reduce DNA CpG methylation. Cow´s milk provides substantial amounts of exosomal miRNA-29s that reach the systemic circulation and target mRNAs of the milk recipient. Via DNMT suppression, milk exosomal miRNA-29s may reduce the magnitude of FTO methylation, thereby epigenetically increasing FTO expression in the milk consumer. High lactation performance with increased milk yield has recently been associated with excessive miRNA-29 expression of dairy cow mammary epithelial cells (DCMECs). Notably, the galactopoietic hormone prolactin upregulates the transcription factor STAT3, which induces miRNA-29 expression. In a retrovirus-like manner milk exosomes may transfer DCMEC-derived miRNA-29s and bovine FTO mRNA to the milk consumer amplifying FTO expression. There is compelling evidence that obesity, T2DM, prostate and breast cancer, and neurodegenerative diseases are all associated with increased FTO expression. Maximization of lactation performance by veterinary medicine with enhanced miRNA-29s and FTO expression associated with increased exosomal miRNA-29 and FTO mRNA transfer to the milk consumer may represent key epigenetic mechanisms promoting FTO/mTORC1-mediated diseases of civilization.