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Published on: January 5, 2017
ERBB2 copy number alterations and protein expression in bladder cancer treated by cystectomy
John C Cheville1, Burak Tekin1, Jacob J Orme2
1Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.
Abstract:
The introduction of antibody-drug-conjugates (ADC) that target HER2 has renewed interest in ERBB2 alterations in bladder cancer. Little is known about the frequency of ERBB2 copy number alterations in primary bladder cancer subtypes and regional nodal metastases, and the effect of amplification on protein expression. The objective of this study was to determine the frequency of ERBB2 copy number alterations and protein expression in a cohort of primary bladder cancer subtypes treated by cystectomy. Tissue microarrays (TMA) were constructed from 820 patients who underwent cystectomy at the Mayo Clinic between 2000 and 2020. In 209 patients, TMAs were constructed from a concurrent pelvic lymph node metastasis. ERBB2 copy numbers were assessed by fluorescence in situ hybridization (FISH) and protein expression by immunohistochemistry (IHC). In a subset of 756 patients, ERBB2 ploidy was compared to previously assessed NECTIN4 ploidy. ERBB2 amplification was present in 59 (7.4%) of 820 bladder cancers and amplification varied by subtype with amplification most frequently identified in micropapillary carcinoma (19%), conventional urothelial carcinoma (8%), urothelial carcinoma with squamous differentiation (7%) and pure squamous cell carcinoma (5%), and less frequently in nested (3%), plasmacytoid (3%), high-grade neuroendocrine (2%) carcinoma, and sarcomatoid carcinoma (0%). There was a significant association between ERBB2 amplification and protein expression in primary and nodal metastases (p < 0.0001). ERBB2 amplification occurred in 26 (12.4%) of 209 nodal metastases and there was concordance in amplification between primary and nodal metastases (kappa = 0.61). Discordance occurred in 15 cases (7.2%) most commonly due to gain of amplification in the nodal metastasis. There was agreement in protein expression between primary and lymph node metastases (kapp = 0.52), and the nodal metastases had a significantly higher expression (p < 0.001). In a subset of five patients with amplified primary tumors and distant metastases, the metastatic tumor was amplified in all cases. Co-amplification of NECTIN4 and ERBB2 occurred in 18 (2.4%) cases. The frequency of ERBB2 amplifications varied by bladder cancer subtype, and amplification resulted in increased protein expression. Nodal metastases had a higher frequency of amplification and protein expression than the primary tumors. A small subset of tumors exhibited co-amplification of ERBB2 and NECTIN4.
Insights
ERBB2 amplification in bladder cancer varies by subtype and increases protein expression. Nodal metastases show higher ERBB2 amplification and expression than primary tumors, impacting treatment strategies for HER2-targeted therapies.
Area of Science:
- Oncology
- Genetics
- Pathology
Background:
- Antibody-drug-conjugates (ADCs) targeting HER2 have increased interest in ERBB2 alterations in bladder cancer.
- Limited data exists on ERBB2 copy number alterations (CNAs) frequency across bladder cancer subtypes and nodal metastases.
- The impact of ERBB2 amplification on protein expression requires further investigation.
Purpose of the Study:
- To determine the frequency of ERBB2 CNAs and protein expression in primary bladder cancer subtypes.
- To analyze ERBB2 amplification in regional nodal metastases and its concordance with primary tumors.
- To assess the relationship between ERBB2 amplification and protein expression.
Main Methods:
- Tissue microarrays (TMAs) from 820 primary bladder cancers and 209 nodal metastases were analyzed.
- ERBB2 copy numbers were assessed using fluorescence in situ hybridization (FISH).
- Protein expression was evaluated by immunohistochemistry (IHC); ERBB2 ploidy was compared to NECTIN4 ploidy in a subset.
Main Results:
- ERBB2 amplification was found in 7.4% of primary bladder cancers, with varying frequencies across subtypes (e.g., 19% in micropapillary carcinoma).
- Amplification was present in 12.4% of nodal metastases, showing concordance with primary tumors (kappa=0.61).
- ERBB2 amplification significantly correlated with increased protein expression in both primary and nodal tumors (p<0.0001), with higher expression in metastases.
Conclusions:
- ERBB2 amplification frequency differs by bladder cancer subtype and leads to elevated protein expression.
- Nodal metastases exhibit a higher prevalence of ERBB2 amplification and protein expression compared to primary tumors.
- Co-amplification of ERBB2 and NECTIN4 was observed in a small subset of cases, suggesting potential therapeutic targets.
