Lacking access to an affordable method of high throughput immunoblot analysis for daily use remains a big challenge for scientists worldwide. We proposed here Quantitative Dot Blot analysis (QDB) to meet this demand. With the defined linear range, QDB analysis fundamentally transforms traditional immunoblot method into a true quantitative assay. Its convenience in analyzing large number of samples also enables bench scientists to examine protein expression levels from multiple parameters. In addition, the small amount of sample lysates needed for analysis means significant saving in research sources and efforts. This method was evaluated at both cellular and tissue levels with unexpected observations otherwise would be hard to achieve using conventional immunoblot methods like Western blot analysis. Using QDB technique, we were able to observed an age-dependent significant alteration of CAPG protein expression level in TRAMP mice. We believe that the adoption of QDB analysis would have immediate impact on biological and biomedical research to provide much needed high-throughput information at protein level in this “Big Data” era.

Developing immunoassay for absolute quantitation of protein biomarkers in Formalin Fixed Paraffin Embedded (FFPE) samples promises improved objectivity, consistency and accuracy in daily clinical practice. The feasibility of Quantitative Dot Blot (QDB) method for this purpose was explored in this study. We were able to measure HER2 protein levels using 0.5 µg/sample total protein lysate extracted from 2 × 5 µm FFPE slices absolutely and quantitatively using QDB method in 332 breast cancer FFPE samples. HER2 levels measured using two clinically validated antibodies for immunohistochemistry respectively were highly correlated (r = 0.963). We also achieved area under the curve (AUC) at 0.9998 ± 0.0002 (p < 0.0001, n = 224) with IHC analysis, and 0.9942 ± 0.0031 (p < 0.0001, n = 319) with combined results from IHC and Fluorescence in situ hybridization (FISH) analyses when analyzed with Receiver Operative Characteristics analysis (ROC) respectively. When the results were converted dichotomously with optimized cutoffs from ROC analyses, we achieved 99.5% concordance with IHC; and 96.9% with combined results from both IHC and FISH analyses. Therefore, we were able to demonstrate QDB method as the first immunoassay platform for absolute quantitation of protein biomarkers in FFPE samples to meet the need of daily clinical practice, especially for local laboratories or laboratories in developing countries.

Purpose: The separation of Luminal A-like from Luminal B-like breast cancer subtypes in surrogate assay relies on Ki67 scores assessed by immunohistochemistry (IHC), a method known to be associated with subjectivity and inconsistency. We attempted to measure Ki67 levels absolutely, quantitatively and objectively in Formalin Fixed Paraffin Embedded (FFPE) specimens, and evaluate its influence on the performance of surrogate assay for breast cancer patients. Methods: The Ki67 protein levels were assessed using both IHC and Quantitative Dot Blot (QDB) methods respectively in 253 specimens. These patients were assigned into Luminal A-like and Luminal B-like subtypes using either Ki67 score of 14% as cutoff in surrogate assay, or 2.31 nmole/g from QDB method as cutoff in adjusted surrogate assay. These two subtyping methods were compared with the Kaplan-Meier, univariate and multivariate survival analyses of the overall survival (OS) of Luminal-like patients. Results: Ki67 levels measured using QDB method was highly correlated with those by IHC analysis (r=0.7, p<0.0001). The survival prediction for Luminal A-like patients was improved significantly in adjusted surrogate assay than surrogate assay (p=0.03 vs p<0.00052). The prediction of Hazard Ratio (HR) was also improve from 2.14 (95%CI: 0.89-5.11, p=0.087) to 6.89 (95%CI: 2.66-17.84, p<0.00001) in multivariate survival analysis. Conclusion: Our study demonstrated that the inherent subjectivity and inconsistency associated with IHC analysis has adverse effect on the performance of surrogate assay. This issue can be improved by objective and quantitative measurement of Ki67 levels with QDB method in daily clinical practice.

No abstract

BackgroundImmunohistochemistry (IHC)-based surrogate assay is the prevailing method in daily clinical practice to determine the necessity of chemotherapy for Luminal-like breast cancer patients worldwide. It relies on Ki67 scores to separate Luminal A-like from Luminal B-like breast cancer subtypes. Yet, IHC-based Ki67 assessment is known to be plagued with subjectivity and inconsistency to undermine the performance of the surrogate assay. A novel method needs to be explored to improve the clinical utility of Ki67 in daily clinical practice.Materials and MethodsThe Ki67 protein levels in a cohort of 253 specimens were assessed with IHC and quantitative dot blot (QDB) methods, respectively, and used to assign these specimens into Luminal A-like and Luminal B-like subtypes accordingly. Their performances were compared with the Kaplan–Meier, univariate, and multivariate survival analyses of the overall survival (OS) of Luminal-like patients.ResultsThe surrogate assay based on absolutely quantitated Ki67 levels (cutoff at 2.31 nmol/g) subtyped the Luminal-like patients more effectively than that based on Ki67 scores (cutoff at 14%) (Log rank test, p = 0.00052 vs. p = 0.031). It is also correlated better with OS in multivariate survival analysis [hazard ratio (HR) at 6.89 (95% CI: 2.66–17.84, p = 0.0001) vs. 2.14 (95% CI: 0.89–5.11, p = 0.087)].ConclusionsOur study showed that the performance of the surrogate assay may be improved significantly by measuring Ki67 levels absolutely, quantitatively, and objectively using the QDB method.