Background: Extensive amounts of archived
formalin fixed
paraffin embedded (FFPE) human
tumor tissues are the ultimate resource to investigate signaling network underlying
tumorigenesis in human. Yet, their usage is severely limited for lacking of suitable
protein techniques. In this study, a quantitative, objective, absolute, and high throughput immunoblot method, quantitative dot blot (
QDB), was explored to address this issue by investigating the putative relationship between
estrogen receptor (ER)/
progesterone receptor (PR) and
human epidermal growth factor receptor 2 (Her2) pathways in
breast cancer tumorigenesis. Methods: In this descriptive observational retrospective study, ER, PR, Her2, and Ki67
protein levels were measured absolutely and quantitatively in 852 FFPE
breast cancer tissues using the
QDB method. ER, PR, and Her2 levels were charted on the X, Y, and Z-axes to observe samples distribution in a 3D scatterplot. Results: A "seesaw" relationship between ER/PR and Her2 pathways was observed in ER-PR-Her2 space, characterized by the expression levels of these 3
proteins. Specimens with strong expressions of ER/PR
proteins were found spreading along the ER/PR floor while those with strong Her2 expression were found wrapping around the Her2 axis. Those lacking strong expressions of all 3
proteins were found accumulating at the intersection of the ER, PR, and Her2 axes. Few specimens floated in the ER-PR-Her2 space to suggest the lack of co-expression of all 3
proteins simultaneously. Ki67 levels were found to be significantly reduced in specimens spreading in the ER-PR space. Conclusions: The unique distribution of specimens in ER-PR-Her2 space prior to any clinical intervention provided visual support of bidirectional talk between ER/PR and Her2 pathways in
breast cancer specimens. Clinical interventions to suppress these 2 pathways alternatively warrant further exploration for
breast cancer patients accordingly. Our study also demonstrated that the
QDB method is an effective tool to analyze archived FFPE
cancer specimens in biomedical research.