Investigating the Levels of Shed Extracellular Domain of HER۲ Protein in the Sera of Bladder Cancer Patients

Background: Receptor tyrosine-protein kinase ERBB۲, also known as human epidermal growth factor receptor-۲ (HER۲), is heterogeneously expressed in a variety of human cancers, including bladder cancer. Based on previous studies that show its association with bladder cancer progression, HER۲ has been included in novel multiplatform biomarkers for prediction of bladder cancer prognosis. However, the clinical significance of HER۲ status remains underinvestigated and poorly linked to the patients’ clinicopathological features. Here, we aim to scrutinize the levels of the extracellular domain of HER۲ in the sera of bladder cancer patients and correlate these levels with clinicopathological features of the tumor.Methods: In the present analytical cross-sectional study, we enrolled ۶۰ pathologically confirmed bladder cancer patients along with ۲۰ age-sex matched healthy controls, and compared their serum HER۲ levels as measured by enzyme-linked immunosorbent assay.Results:We observed no statistically significant difference when comparing the levels of HER۲ in the sera of cases and controls (P>۰.۰۵). Interestingly, serum HER۲ levels of controls were higher than bladder cancer patients who had lymph node metastasis (P=۰.۰۳۶). Serum levels of HER۲ were also higher in controls than bladder cancer patients with perineural invasion (P=۰.۰۲۸). We observed significantly higher HER۲ serum levels in transitional cell carcinoma patients in comparison to non-transitional cell carcinoma patients (P=۰.۰۱۶).Conclusion: Our observations are suggestive of the absence of any association between bladder cancer prognostic factors and serum HER۲ levels. To draw any definitive conclusion, further studies with larger sample sizes that examine the presence of neutralizing auto-antibodies against serum HER۲, immunohistochemistry examination of HER۲ in bladder tumor and lymph node samples, and urinary HER۲ levels, along with measurement of its serum levels would be helpful.