Development of Cancer Biomarker Heat Shock Protein 90α Certified Reference Material Using Two Different Isotope Dilution Mass Spectrometry Techniques

Heat shock protein 90 alpha (HSP90 alpha) has been regarded as an important indicator for judging tumor metastasis and prognosis due to its significant upregulation in various tumors. Therefore, the accurate quantification of HSP90 alpha is of great significance for clinical diagnosis and therapy of cancers. However, the lack of HSP90 alpha certified reference material (CRM) leads to the accuracy and consistency of quantification methods not being effectively evaluated. Besides, quantitative results without traceability make comparisons between different studies difficult. In this study, an HSP90 alpha solution CRM was developed from the recombinant protein raw material. The recombinant protein is a dimer, and the purity of the CRM candidate reached 96.71%. Both amino acid analysis-isotope dilution mass spectrometry (AAA-IDMS) and unique peptide analysis-isotope dilution mass spectrometry (UPA-IDMS) were performed to measure the content of HSP90 alpha in the solution CRM candidate, and the certified value was assessed to be 66.2 +/- 8.8 mu g/g. Good homogeneity of the CRM was identified, and the stability examination suggested that the CRM was stable for at least 4 months at - 80 degree celsius and for 7 days at 4 degree celsius. With traceability to SI unit (kg), this CRM has potential to help establish a metrological traceability chain for quantification of HSP90 alpha, which will make the quantification results standardized and comparable regardless of the quantitative methods.