Novel method for differentiation between Trastuzumab and host adaptive response.

Area of Science:

• Oncology
• Immunology
• Biochemistry

Background:

• Humoral immune responses to human epidermal growth factor receptor 2 (HER-2) are prognostic markers in breast cancer.
• The therapeutic antibody Trastuzumab (Herceptin) targets HER-2, complicating the detection of host-generated antibodies.
• A method is needed to differentiate host anti-HER-2 antibodies from Herceptin interference.

Purpose of the Study:

• To develop a screening method to detect host antibodies against HER-2 without interference from Herceptin.
• To create a modified HER-2 protein that does not bind Herceptin but retains its structure for antibody detection.

Main Methods:

• Generated truncation mutants of HER-2 within the Herceptin epitope to inhibit binding.
• Introduced a three-amino acid substitution (PPF→SSS) to abrogate Herceptin binding while preserving the HER-2 extracellular domain (ECD).
• Established a stable cell line expressing the mutated HER-2 ECD for use in patient sera screening.

Main Results:

• The developed method successfully differentiates between host antibodies and Herceptin.
• The mutated HER-2 ECD effectively inhibits Herceptin binding.
• A stable cell line expressing the mutated HER-2 ECD provides a reliable source for detecting host immune responses.

Conclusions:

• The constructed mutated HER-2 protein serves as a tool to distinguish host anti-HER-2 immune responses from therapeutic antibody effects.
• This method offers a proof of principle for accurately assessing humoral immunity against HER-2 in cancer patients undergoing Herceptin therapy.