Figure 7.

Model of a working hypothesis for 5-HT influences on breast cancer progression. 5-HT is a tumor-suppressing signal in non-transformed breast cells and early stage breast cancers, so early tumor growth relies on reductions in TPH1 expression. During tumor progression, cells acquire genetic or epigenetic alterations in 5-HT signaling which then make them resistant to suppressive 5-HT actions and favor tumor-promoting actions (e.g., dynamic cell junctions and cell shedding), as well as acquisition of new receptors and functions (e.g., stimulated proliferation and epithelial-mesenchymal transition). The figure is inspired by the image in [69].