The HER3 pathway as a potential target for inhibition in patients with biliary tract cancers

Area of Science:

• Oncology
• Molecular Biology
• Cancer Research

Background:

• Biliary tract cancers (BTC) are a heterogeneous group of malignancies with limited treatment options.
• Expression of human epidermal growth factor receptor (HER) family members, specifically HER2 and HER3, has been explored in small BTC studies with varying results.
• Standardized scoring systems and methodologies are crucial for accurate assessment of HER2 and HER3 expression.

Purpose of the Study:

• To investigate the expression and amplification of HER2 and HER3 in a cohort of biliary tract cancer patients.
• To correlate HER2 and HER3 expression with clinicopathological features and patient outcomes.
• To identify potential therapeutic targets and biomarkers for BTC treatment.

Main Methods:

• Immunohistochemistry (IHC) was used to assess HER2 and HER3 protein overexpression.
• Fluorescent in-situ hybridisation (FISH) was employed to evaluate HER2 and HER3 gene amplification.
• Logistic regression and survival analyses (Kaplan-Meier, Log-rank test, Cox regression) were utilized for statistical evaluation.

Main Results:

• HER2 overexpression/amplification was rare, identified in only 1 patient (1%).
• HER3 overexpression was predominantly cytoplasmic, with membrane and cytoplasmic rates of 16% and 24%, respectively.
• HER3 overexpression varied across subtypes: ampullary cancer (8%), gallbladder cancer (8-10%), intrahepatic cholangiocarcinoma (23-38%), and extrahepatic cholangiocarcinoma (17-22%).

Conclusions:

• A significant subset of biliary tract cancer patients exhibit HER3 expression, particularly in the cytoplasm.
• Targeting HER3 warrants further investigation as a potential therapeutic strategy for BTC.
• Mechanistic studies are needed to elucidate downstream HER3 effects, identify new biomarkers, and optimize patient selection for future clinical trials.