Table 1
Regulators of mammary morphogenesis and their agonists, antagonists, downstream targets and realm of influence
| Regulator | Agonists | Antagonists | Targets | Effects |
| GH-R (st) | GH (pit) | IGF-1 (st) | General | |
| IGF-1R (ep) | IGF-1 (st) | IGFBPs (st) | Unknown | General |
| ER-α (st/ep) | E1/E2 (ov) | Amphiregulin et al. | General | |
| PR-B (st?) | ER, P (ov) | Wnt4, RANKL | Tertiary branching | |
| EGFR (st) | Amphiregulin (ep) | Sprouty? | MMPs, FGFs et al. | General |
| Amphiregulin (ep) | ER, ADAM17 (ep) | HSPGs | EGFR (st) | General |
| ADAM17 (ep) | PPCs et al. | TIMP3 (ep) | Amphiregulin (ep) | General |
| MMP-14 (st) | EGFR, PPCs et al. | TIMPs 2–4 | MMP-2, Coll I | General |
| MMP-2 (st?) | TGF-β, ER, MMP-14 | TIMPs 1–4 | Coll I et al.? | Elongation |
| MMP-3 (st) | Epimorphin et al. | TGF-β, TIMPs | Unknown | Secondary branching |
| FGFR2 (ep) | FGFs (st) | Sprouty2 (ep) | Unknown | TEBs |
| ErbB2 (ep) | Unknown | Unknown | Unknown | TEBs |
| Epimorphin (st/me) | Metalloenzymes | Unknown | C/EPBβ, MMPs | Branching |
| TGF-β1 (ep) | ER, MMPs, plasmin | LAP | TGF-βRI/II, MMPs | Spacing |
| CSF-1R (mφ) | CSF-1 (ep) | Mφ recruitment | TEBs | |
| CCR3 (eos) | Eotaxin | Eos recruitment | Branching | |
| Integrin α2β1 (ep) | Laminins, collagens | TEBs, ducts | ||
| DDR1 (ep) | Collagens | TEBs, ducts |
ADAM, a disintegrin and metalloproteinase; CCR, CC chemokine receptor; Coll, collagen; CSF, colony-stimulating factor; DDR, discoidin domain receptor; EGFR, epidermal growth factor receptor; eos, eosinophil; ep, epithelial; E1/E2, estrone/estradiol; ER, estrogen receptor; FGF, fibroblast growth factor; FGFR, FGF receptor; GH, growth hormone; GH-R, growth hormone receptor; HSPG, heparan sulfate proteoglycan; IGF-1, insulin-like growth factor-1; IGF-1R, IGF-1 receptor; IGFBPs, IGF-binding proteins; LAP, latency-associated peptide; me, myoepithelial; MMP, matrix metalloproteinase; mφ, macrophage; ov, ovarian; pit, pituitary; PPC, proprotein convertase; P, progesterone; PR, progesterone receptor; RANKL, receptor activator of nuclear factor κB (RANK) ligand; st, stromal; TEB, terminal end bud; TGF, transforming growth factor; TIMP, tissue inhibitor of metalloproteinases. Required sources are provided in parentheses.