Evaluation of the influence of trastuzumab therapy on serum levels of HER-2 protein and breast cancer cell lines

Introduction
Breast cancer is a complex disease characterised by abnormal cell growth in breast tissue. Trastuzumab is a targeted therapy that inhibits the HER-2 receptor and suppresses tumour growth. We aimed to determine if the clinical course of the disease could be predicted by early changes in serum levels of human epidermal growth factor receptor 2 (HER-2/neu) following trastuzumab-based therapy.

Material and methods
The study enrolled 120 women, divided into an experimental group (60 breast cancer patients receiving trastuzumab) and a control group (60 healthy women). Serum samples were collected before each weekly trastuzumab treatment. In addition, human breast cancer cell lines MCF-7 and AMJ13 were cultured in vitro and treated with trastuzumab. The study assessed cell viability using a cytotoxicity assay (methyl thiazolyl tetrazolium) and measured HER-2 protein levels. The half maximal inhibitory concentration (IC50) was determined to evaluate the effect of trastuzumab on breast cancer.

Results
The results showed that breast cancer patients had significantly lower serum levels of HER-2 compared to the control group. The cytotoxicity assay demonstrated that increasing trastuzumab concentration enhanced growth inhibition and cytotoxicity in the cell lines. There was a significant difference in IC50 between the MCF-7 and AMJ13 cell lines.

Conclusions
The study provides valuable insights into the effects of trastuzumab on serum HER-2 levels and breast cancer cell lines. These findings have implications for resource allocation and treatment decisions in breast cancer management. By understanding the impact of trastuzumab on HER-2 levels and tumour cells, healthcare professionals can make more informed decisions regarding therapy options for patients.