Defining NECTIN4 Amplification and Protein Expression in Urothelial Carcinoma and Histologic Subtypes

Area of Science:

• Oncology
• Genetics
• Molecular Biology

Background:

• Chromosome 1q23.3 amplification is frequent in metastatic urothelial carcinoma (UC).
• This region includes NECTIN4, a target for enfortumab vedotin, an antibody-drug conjugate.
• Increased NECTIN4 expression due to amplification may influence treatment response.

Purpose of the Study:

• To determine the frequency of NECTIN4 amplification in primary UC and subtypes using fluorescence in situ hybridization (FISH).
• To assess NECTIN4 protein expression via immunohistochemistry (IHC).
• To evaluate NECTIN4 amplification and expression in primary tumors and corresponding lymph node metastases.

Main Methods:

• Tissue microarrays (TMA) from 841 primary UC patients and 218 with lymph node metastases were analyzed.
• FISH was used to detect NECTIN4 amplification.
• IHC was performed to quantify NECTIN4 protein expression (H scores).

Main Results:

• NECTIN4 amplification occurred in 18% of primary UCs, with varying frequencies across subtypes (e.g., 25% in micropapillary carcinoma).
• Amplified tumors showed significantly higher NECTIN4 protein expression (H scores) (P < .0001).
• NECTIN4 amplification was found in 17% of lymph node metastases, with good concordance between primary and metastatic sites.

Conclusions:

• NECTIN4 amplification frequency and resulting protein expression levels vary among UC subtypes.
• Amplification generally correlates with increased NECTIN4 protein expression, but discordance exists.
• Understanding NECTIN4 status in primary tumors and metastases is crucial for targeted therapy selection.