Table 1.

TNBC classification systems based on different signaling pathways [18,20,22,23].

Lehman’s Subtypes
BL1	↑ Ki67 ↑ cell cycle and DNA damage response gene expression
BL2	↑ growth factor signaling ↑ myoepithelial markers
M	deregulation of EGFR, MAPK, and PI3K signaling
MSL	deregulation of EGFR, calcium signaling, MAPK ↓ genes associated with cellular proliferation ↑ genes related to mesenchymal stem cells
IM	↑ IFNα and IFNγ signaling ↑ cytotoxic T-lymphocyte-associated protein 4
LAR	↑ androgen receptor (AR) expression
Burstein’s Subtypes
MES	↑ cell cycle, mismatch repair and DNA damage networks ↑ hereditary breast cancer signaling pathways
BLIA	↑ genes controlling B cell, T cell and natural killer cell functions
BLIS	↓ B cell, T cell, and natural killer cell immune-regulating pathways ↓ cytokine pathways
LAR	↑ AR, ER, prolactin, and ErbB4 signaling
FUSCC Subtypes
MES	↑ ECM-receptor interaction, focal adhesion, TGF-beta signaling ↑ ABC transporter ↑ Adipocytokine signaling
IM	↑ Cytokine–cytokine receptor interaction ↑ T and B cell receptor signaling ↑ Chemokine signaling, NF-kappa-B signaling
BLIS	↑ Mitotic cell cycle, mitotic prometaphase, M phase of mitotic cell cycle ↑ DNA replication, DNA repair ↓ Innate immune response ↓ T cell receptor signaling
LAR	↑ Steroid hormone biosynthesis ↑ Porphyrin and chlorophyll metabolism ↑ PPAR signaling pathway ↑ Androgen and estrogen metabolism

(BL, basal-like; M, mesenchymal; MSL, mesenchymal stem-like; IM, immunomodulatory; LAR, luminal androgen receptor; MES, mesenchymal; BLIA, basal-like immune-activated; BLIS, basal-like immunosuppressed; ECM, extracellular matrix; PPAR, peroxisome proliferator-activated receptor; TGF, transforming growth factor; IFN, interferone; EFGR, epidermal growth factor receptor; MAPK, mitogen-activated protein kinase; PI3K, phosphatidylinositol 3-kinase).