Novel markers to detect HER2 amplification in Breast cancer

Overexpression of HER2 in breast cancer is an important prognostic and predictive biomarker, assessed using immunohistochemistry (IHC) and in situ hybridization (ISH). More than 20% of tumours are graded equivocal on IHC and is send for reflex testing via ISH. In situ hybridization (ISH) is an expensive assay and is not available widely in resource limiting areas. Therefore, we propose that genes found significantly co-expressed with HER2 in breast cancer can be used as surrogate markers for HER2 in breast cancer which can detect HER2 positivity on IHC itself. This hypothesis is based on analysis of publicly available datasets from the Gene Expression Omnibus (GEO) database. The genes found most significantly correlated with HER2 expression were PGAP3 (r = 0.85), GRB7 (r = 0.82), STARD3 (r = 0.78), CDK12 (r= 0.68), PSMD3 (r= 0.67) and GSDMB (r = 0.63). We hypothesize that these identified surrogate markers for HER2 amplification which can be detected on IHC can detect HER2 amplification status in HER2 equivocal tumors based on IHC staining alone and will reduce the number of HER2 2+ (equivocal) category tumours.

Other Solid Cancers: 2021 ASCO Annual Meeting Highlights for the Advanced Practitioner

Abby Fuoto, DNP, ANP-BC, AOCNP®, ACHPN, of University of Arizona Cancer Center, considers the implications of a novel monoclonal antibody for nasopharyngeal cancer, and Mee-young Lee, MSN, ANP-BC, of Monter Cancer Center, Northwell, discusses the design of a basket trial for tumors with HER2 amplification or overexpression. Meeting coverage is provided by The ASCO Post.

Transcriptome and genome evolution during HER2-amplified breast neoplasia

Background The acquisition of oncogenic drivers is a critical feature of cancer progression. For some carcinomas, it is clear that certain genetic drivers occur early in neoplasia and others late. Why these drivers are selected and how these changes alter the neoplasia’s fitness is less understood. Methods Here we use spatially oriented genomic approaches to identify transcriptomic and genetic changes at the single-duct level within precursor neoplasia associated with invasive breast cancer. We study HER2 amplification in ductal carcinoma in situ (DCIS) as an event that can be both quantified and spatially located via fluorescence in situ hybridization (FISH) and immunohistochemistry on fixed paraffin-embedded tissue. Results By combining the HER2-FISH with the laser capture microdissection (LCM) Smart-3SEQ method, we found that HER2 amplification in DCIS alters the transcriptomic profiles and increases diversity of copy number variations (CNVs). Particularly, interferon signaling pathway is activated by HER2 amplification in DCIS, which may provide a prolonged interferon signaling activation in HER2-positive breast cancer. Multiple subclones of HER2-amplified DCIS with distinct CNV profiles are observed, suggesting that multiple events occurred for the acquisition of HER2 amplification. Notably, DCIS acquires key transcriptomic changes and CNV events prior to HER2 amplification, suggesting that pre-amplified DCIS may create a cellular state primed to gain HER2 amplification for growth advantage. Conclusion By using genomic methods that are spatially oriented, this study identifies several features that appear to generate insights into neoplastic progression in precancer lesions at a single-duct level.

A Reliable and Standardizable Differential PCR and qPCR Methodology Assesses HER2 Gene Amplification in Gastric Cancer

We have applied two PCR techniques, differential PCR (diffPCR) and qPCR for the identification of HER2 gene amplifications in genomic DNA of tumor and distal gastric samples from patients with gastric cancer. The diffPCR technique consists of the simultaneous amplification of the HER2 gene and a housekeeping gene by conventional PCR and the densitometric analysis of the bands obtained. We established a cut-off point based on the mean and standard deviation analyzing the DNA of 30 gastric tissues from patients undergoing non-cancer gastrectomy. diffPCR and qPCR yielded consistent results. HER2-overexpression was detected in 25% of patients and was further confirmed by immunohistochemistry and immunofluorescence. The approaches herein described may serve as complementary and reliable methods to assess HER2 amplification.