The cover for issue 30 of Oncotarget features Figure 4, "RNAseq results demonstrating differences between normal, cancer, and redirected cells," by Frank-Kamenetskii, et al. which reported that the influence of breast cancer cells on normal cells of the microenvironment, such as fibroblasts and macrophages, has been heavily studied but the influence of normal epithelial cells on breast cancer cells has not.
Here using in vivo and in vitro models the Oncotarget authors demonstrate the impact epithelial cells and the mammary microenvironment can exert on breast cancer cells.
Under specific conditions, signals that originate in epithelial cells can induce phenotypic and genotypic changes in cancer cells.
The authors have termed this phenomenon "cancer cell redirection." Once breast cancer cells are redirected, either in vivo or in vitro, they lose their tumor forming capacity and undergo a genetic expression profile shift away from one that supports a cancer profile towards one that supports a non-tumorigenic epithelial profile.
These findings indicate that epithelial cells and the normal microenvironment influence breast cancer cells and that under certain circumstances restrict proliferation of tumorigenic cells.
Tissue microenvironments are complex regions that consist of multiple cell types such as epithelial cells, adipocytes, fibroblasts, vascular endothelial cells, resident and transient immune cells, and somatic stem cells."
Dr. Brian W. Booth, Clemson University
Using rodent models, it was discovered that when mammary epithelial cells were transplanted into a mammary fat pads of pre-pubescent female mice devoid of endogenous epithelium an entire functional mammary outgrowth could be recapitulated regardless of age or parity status of the transplanted cells.
When dispersed cell suspensions of mammary epithelial cells are used in these models the cells participate in the formation of new microenvironments allowing for the normal development of mammary outgrowths.
Stem cells isolated from the central nervous system, bone marrow, testes, and embryonic stem cells have been introduced into reforming mammary microenvironments and adopted mammary epithelial phenotypes.
Lineage-traced daughter cells of the non-mammary stem cells participated in the normal development of mammary ductal trees and differentiated into luminal epithelial cells, myoepithelial cells, and milk protein-producing secretory epithelial cells during lactation.
Frank-Kamenetskii, A., et al. (2020) Induction of phenotypic changes in HER2-postive breast cancer cells in vivo and in vitro. Oncotarget. doi.org/10.18632/oncotarget.27679.