Breast Cancer Research: HER2, ER/PR, BRCA & Triple-Negative Reagents

Breast cancer is classified into molecular subtypes defined by receptor expression: luminal A/B (ER+/PR+), HER2-positive, and triple-negative (TNBC). Each subtype requires different therapeutic approaches and corresponding research reagents for biomarker detection, target validation, and drug development. For a broader view of all oncology reagent categories, see our Cancer Research Reagents hub.

Key Targets and Biomarkers

HER2 (ERBB2) overexpression/amplification defines ~15–20% of breast cancers. HER2 IHC scoring (0, 1+, 2+, 3+) determines eligibility for HER2-targeted therapies. The recent expansion of HER2-low (IHC 1+ or 2+/FISH-negative) as a therapeutic category with T-DXd has increased demand for sensitive HER2 detection reagents. For IHC scoring guidance by tumor type, see our IHC Panel Design guide.

ER (ESR1) and PR (PGR) IHC is the standard for hormone receptor classification. Anti-ER and anti-PR antibodies for research-use IHC enable expression studies, treatment response prediction, and resistance mechanism investigation.

BRCA1/2 mutations confer sensitivity to PARP inhibitors and platinum chemotherapy. Anti-BRCA1 and anti-BRCA2 antibodies detect nuclear protein expression by IHC and WB, complementing genetic testing.

TNBC (ER-/PR-/HER2-) has the fewest targeted options but is responding to: PD-L1 checkpoint inhibitors (atezolizumab + nab-paclitaxel), TROP2 ADCs (sacituzumab govitecan), and emerging targets (Nectin-4, CD276/B7-H3). Research reagents for all these targets are available.

Ki-67 (MKI67) IHC is used to assess tumor proliferation rate, distinguishing luminal A (Ki-67 low) from luminal B (Ki-67 high) subtypes.

References

1. Waks AG, Winer EP. Breast cancer treatment: a review. JAMA. 2019;321(3):288-300. doi: 10.1001/jama.2018.19323

2. Slamon DJ, Clark GM, Wong SG, Levin WJ, Ullrich A, McGuire WL. Human breast cancer: correlation of relapse and survival with amplification of the HER-2/neu oncogene. Science. 1987;235(4785):177-182. doi: 10.1126/science.3798106

3. Drago JZ, Modi S, Chandarlapaty S. Unlocking the potential of antibody-drug conjugates for cancer therapy. Nat Rev Clin Oncol. 2021;18(6):327-344. doi: 10.1038/s41571-021-00470-8

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