Of interest, a recent study involving the relationship between obesity-related changes in the extracellular matrix of mammary adipose tissue and breast tumorigenesis has shown that in comparison to lean mice, mammary tissue-derived extracellular matrix from obese mice contained increased levels of fibronectin and increased the proliferation of premalignant mammary epithelial cells [17]. This evidence concerns the gene FN1 and obesity due to melanocortin 4 receptor deficiency.