Midkine as a driver of age-related changes and increase in mammary tumorigenesis [scRNA-seq]

Aging is one of the pivotal risk factors for cancer, notably in breast cancer with diagnosis striking at the average age of 62. However, the intricate mechanisms underlying aging and breast cancer susceptibility remain unclear. In this study, we depicted a comprehensive single-cell landscape of gene expression (scRNA-seq) and chromatin accessibility (scATAC-seq) of mammary glands from different aged rats. Mechanically, we revealed midkine, a growth factor secreted by basal epithelial cells, which might mediates the age-related mammary changes, as a validation, we treated young rats with midkine for a month and performed the single-cell transcriptome analysis on those mammary glands. We found midkine could largely mediates the transcriptional shift and hyperproliferation of aged epithelial cell by activating PI3K/AKT-SREBF1 signaling. Furthermore, we find the aging-related accumulation of midkine could largely mediated aging-related changes of mammary gland and promoting the tumorigenesis of breast tumors proved using a well-established Nitroso-N-methylurea (NMU)-induced breast cancer rat model. Our finding identify a promising biomarker and intervention target for both mammary aging and tumorigenesis. Mammary glands were freshly collected from different aged rats (3-, 6-, 12- and 22-month-old) and rats (2-month-old) with one-month midkine treatment. The tissue was digested into single cells, then submitted for single-cell RNA sequencing.