Molecular Basis of Triple Negative Breast Cancer and Implications for Therapy

Table 1

Intrinsic subtypes of breast cancer.

Intrinsic subtypes of breast cancer	Characteristics
Luminal A	High level expression of ER and ER-associated genes, associated with a favorable clinical outcome.
Luminal B	Low level expression of ER and ER-associated genes, associated with a higher tumor cell proliferation rate and a worse clinical outcome compared to the luminal A subtype.
HER-2 Enriched	High level expression of HER2 and GRB7, associated with a poor outcome before the era of HER2-targeted agents.
Basal-like	Positive for the expression of basal cytokeratin but negative for the expression of luminal- and HER2-related genes, associated with a high tumor cell proliferation rate and a poor clinical outcome.
Normal-like	Similar expression compared to normal breast, suspicious for normal cell contamination.
Claudin-low	Lack the expression of claudin proteins that are implicated in cell-cell adhesion, but high expression of EMT and putative stem cell markers, associated with ER and HER2 negativity but low in basal cytokeratin expression.