Insulin-like Growth Factor 1 gene polymorphism and breast cancer risk

The Role of Cow's Milk Consumption in Breast Cancer Initiation and Progression

PURPOSE OF REVIEW

This review evaluates cow milk's impact on breast carcinogenesis by linking recent epidemiological evidence and new insights into the molecular signaling of milk and its constituents in breast cancer (BCa) pathogenesis.

RECENT FINDINGS

Recent prospective cohort studies support the association between cow's milk consumption and the risk of estrogen receptor-α-positive (ER⁺) BCa. Milk is a complex biological fluid that increases systemic insulin-like growth factor 1 (IGF-1), insulin and estrogen signaling, and interacting hormonal promoters of BCa. Further potential oncogenic components of commercial milk include exosomal microRNAs (miR-148a-3p, miR-21-5p), bovine meat and milk factors, aflatoxin M1, bisphenol A, pesticides, and micro- and nanoplastics. Individuals with BRCA1 loss-of-function mutations and FTO and IGF1 gain-of-function polymorphisms enhancing IGF-1/mTORC1 signaling may be at increased risk for milk-induced ER⁺ BCa. Recent prospective epidemiological and pathobiochemical studies identify commercial milk consumption as a critical risk factor of ER⁺ BCa. Large meta-analyses gathering individuals of different ethnic origins with milk derived from dairy cows of varying genetic backgrounds and diverse feeding procedures as well as missing data on thermal processing of milk (pasteurization versus ultra-heat treatment) make multi-national meta-analyses unsuitable for BCa risk estimations in susceptible populations. Future studies are required that consider all vulnerable periods of breast carcinogenesis to cow's milk exposure, beginning during the perinatal period and puberty, since these are the most critical periods of mammary gland morphogenesis. Notwithstanding the need for better studies including detailed information on milk processing and vulnerable periods of human breast carcinogenesis, the available evidence suggests that dietary guidelines on milk consumption may have to be reconsidered.

Upregulated miR‑203a‑3p and its potential molecular mechanism in breast cancer: A study based on bioinformatics analyses and a comprehensive meta‑analysis

Breast cancer (BC) has been identified as the leading malignancy in women worldwide. However, the potential molecular mechanism of microRNA (miR)‑203a‑3p in BC remains to be elucidated. The present study evaluated the expression of miR‑203a‑3p in BC and adjacent normal tissue in several publically available datasets. The distinguishability of precursor miR‑203a and miR‑203a‑3p in BC tissue and adjacent breast tissue was assessed using receiver operating characteristic (ROC) and summarized ROC (sROC) approaches. In addition, gene ontology (GO) enrichment, Kyoto Encyclopedia of Genes and Genomes pathway analysis and protein‑protein interaction analysis were performed to determine the potential molecular mechanism of miR‑203a‑3p in BC. It was identified that the expression of precursor miR‑203a was markedly upregulated in 1,077 BC tissue samples compared to 104 adjacent breast tissue samples from The Cancer Genome Atlas. Additionally, an increasing trend in miR‑203a‑3p expression was observed in 756 BC tissue samples compared with 76 adjacent breast tissue samples from the University of California Santa Cruz Xena project. In addition, a comprehensive meta‑analysis suggested that the expression of miR‑203a‑3p was markedly increased in 2,444 BC tissue samples compared with 559 adjacent breast tissue samples. The area under the curve of the ROC and sROC revealed that miR‑203a‑3p expression was able to distinguish between BC tissue and adjacent breast tissue. However, miR‑203a‑3p exhibited no prognostic value in BC. The results of GO enrichment demonstrated that the miR‑203a target genes were associated with 'plasma membrane integrity', 'cell surface receptor linked signal and transduction' and '3',5'‑cyclic nucleotide phosphodiesterase activity'. 'Purine metabolism' was identified as the pathway with the most enrichment of miR‑203a‑3p target genes in BC. The present study also identified insulin‑like growth factor receptor (IGF1) as a hub gene associated with miR‑203a in BC. In summary, miR‑203a‑3p may enhance the development and oncogenesis of BC, and IGF1 was defined as a hub gene of miR‑203a‑3p in BC.