Table 1.

Reported biomarkers data sources.

Biomarker	Information in Breast Cancer	Reference
Ki-67	Protein expression is related to cell proliferation and higher protein levels to biological aggressiveness.	Menon et al. [30] and Rakha [31]
ER	Nuclear receptor that acts as a ligand-activated transcription factor. The main isoform is ERα that is associated with cell survival and proliferation.	Fuentes and Silveyra [37] and Mills et al. [39]
PR	Nuclear receptor that acts as a ligand-activated transcription factor. It is associated with the expression of genes related to the cell cycle, cell differentiation, and proliferation.	Hilton et al. [33] and Cenciarini and Proietti [44]
HER2	Receptor signaling leads to tumor growth and proliferation, adhesion, cell survival, and metastasis.	Harbeck et al. [3] and Nicolini et al. [40]
p53	Tumor suppressor protein involved in cell cycle arrest, differentiation, senescence, apoptosis, cell growth, and DNA repair. Its degradation is linked to tumor formation, progression, and metastasis.	Shahbandi et al. [55] and Xu et al. [56]
BRCA1/ BRCA2	Tumor suppressor genes fundamental to DNA repair. Loss of function generates inefficient DNA repair, increasing mutation rates, and contributing to tumor development.	Ayed-Guerfali et al. [61]
PTEN	Tumor suppressor gene related to cell cycle progression, cell growth, and survival. Deletions or mutations are related to proliferation, invasion, and metastasis.	Carbognin et al. [66] and Chen et al. [67]
CHEK2	Tumor suppressor gene related to cell cycle regulation, inhibition of cell proliferation, activation of DNA repair, and apoptosis. It encodes the protein serine/threonine CHK2 kinase, which is involved in DNA damage repair.	Kleiblova et al. [70], Boonen et al. [71], and Greville-Heygate et al. [72]
ATM	Gene associated with the DNA double-strand break repair mechanism. It encodes proteins that participate in DNA repair and cell cycle regulation.	Toss et al. [74], Cunha et al. [79], and Moslemi et al. [80]
PALB2	Tumor suppressor gene that encodes PALB2, responsible for BRCA2 nuclear localization and DNA damage repair.	Nepomuceno et al. [84]
BRIP1	Tumor suppressor gene that encodes a protein belonging to the RecQ DEAH helicase family that helps repair damaged DNA by interacting with BRCA1.	Khan et al. [91] and Moyer et al. [92]
CDH1	Tumor suppressor gene that encodes the E-cadherin cell–cell adhesion protein, that prevents migration of tumor cells, avoiding cancer progression and metastases.	Bücker and Lehmann [98]
BARD1	BRCA1-binding partner protein that is related to DNA damage repair. Higher expression is associated with worse prognosis.	Zheng et al. [103] and Zhu et al. [105]
PIK3CA	Gene involved in regulation of proliferation and apoptosis. PI3K protein is involved in several cellular processes, such as protein synthesis, cell proliferation, survival, glucose homeostasis, and DNA repair.	Reinhardt et al. [107], Thorpe et al. [108], and Venetis et al. [109]

ER: estrogen receptor; PR: progesterone receptor.