Challenges in Detection of Serum Oncoprotein: Relevance to Breast Cancer Diagnostics

Abstract

Breast cancer is a highly prevalent malignancy that shows improved outcomes with earlier diagnosis. Current screening and monitoring methods have improved survival rates, but the limitations of these approaches have led to the investigation of biomarker evaluation to improve early diagnosis and treatment monitoring. The enzyme-linked immunosorbent assay (ELISA) is a specific and robust technique ideally suited for the quantification of protein biomarkers from blood or its constituents. The continued clinical relevancy of this assay format will require overcoming specific technical challenges, including the ultra-sensitive detection of trace biomarkers and the circumventing of potential assay interference due to the expanding use of monoclonal antibody (mAb) therapeutics. Approaches to increasing the sensitivity of ELISA have been numerous and include employing more sensitive substrates, combining ELISA with the polymerase chain reaction (PCR), and incorporating nanoparticles as shuttles for detection antibodies and enzymes. These modifications have resulted in substantial boosts in the ability to detect extremely low levels of protein biomarkers, with some systems reliably detecting antigen at sub-femtomolar concentrations. Extensive utilization of mAb therapies in oncology has presented an additional contemporary challenge for ELISA, particularly when both therapeutic and assay antibodies target the same protein antigen. Resolution of issues such as epitope overlap and steric hindrance requires a rational approach to the design of diagnostic antibodies that takes advantage of modern antibody generation pipelines, epitope binning techniques and computational methods to strategically target biomarker epitopes. This review discusses technical strategies in ELISA implemented to date and their feasibility to address current constraints on sensitivity and problems with interference in the clinical setting. The impact of these recent advancements will depend upon their transformation from research laboratory protocols into facile, reliable detection systems that can ideally be replicated in point-of-care devices to maximize utilization and transform both the diagnostic and therapeutic monitoring landscape.

Keywords:

• breast cancer
• diagnosis
• ELISA
• detection
• plasmonics
• sensitivity

Author Contributions

All authors contributed to drafting or revising the article, gave final approval of the version to be published, agreed to the submitted journal, and agreed to be accountable for all aspects of the work.

Disclosure

Dr Hongtao Zhang owns stocks in Martell Diagnostic Laboratories, outside the submitted work; In addition, Dr Hongtao Zhang has patents Greene, MI, Eberwine, J, Kacharmina, JE, and Zhang, H-T. Methods, systems and kits for immuno-detection of epitopes expressed on molecules. US 6,743,592); Greene, M. I., Zhang, H. Methods of detecting molecules expressing selected epitopes via fluorescent dyes. US 7,045,286; Greene, MI, Eberwine, J, Kacharmina, JE, and Zhang, H-T. Methods for immuno-detection of epitopes. US 7,341,831 issued May 16, 2006; Greene, MI, Eberwine, J, Kacharmina, JE, and Zhang, H-T. Method, system and kits for immuno-detection of epitopes expressed on molecules. US 7,361,464; M. I., Zhang, H. Methods of detecting molecules expressing selected epitopes via fluorescent dyes. US 7,524,628 issued related to FACTT mentioned in the review. Dr Franklin Pass is an employee of Martell Diagnostic Laboratories. Dr Mark I Greene reports grants from Martell, during the conduct of the study; grants from the NIH and BCRF, outside the submitted work; In addition, Dr Mark I Greene has a patent on erbB2 therapy owned by the University of Pennsylvania licensed to Roche-Genentech. The authors report no other conflicts of interest in this work.