Quantifying insulin receptor isoform expression in FFPE breast tumors

Area of Science:

• Oncology
• Molecular Biology
• Biomarker Discovery

Background:

• Predictive biomarkers for IGF-targeted cancer therapies are needed.
• Insulin receptor A isoform (InsR-A) is a candidate, but difficult to quantify in FFPE tissues due to similarity with InsR-B.
• Developed qPCR assays for InsR-A, InsR-B, and IGF-1R in FFPE tissues.

Purpose of the Study:

• To develop and validate qPCR assays for quantifying InsR-A and InsR-B in FFPE breast cancer tissues.
• To assess the feasibility of using these assays in clinical archived FFPE breast cancer tumors.
• To investigate the expression levels of InsR-A and InsR-B in different breast cancer subtypes.

Main Methods:

• Designed FFPE-compatible primer sets with small amplicon sizes (<60 bp).
• Validated primer sets for specificity, repeatability, and amplification efficiency.
• Tested qPCR assays on FFPE tumors from ER+, ER-, and hormone-refractory ER+ (HR ER+) breast cancers.

Main Results:

• qPCR assays demonstrated high reproducibility (96-104% efficiency) and sensitivity (4-5 copies/reaction).
• Over 90% of FFPE samples successfully amplified for InsR-A, InsR-B, or IGF-1R.
• InsR-A was the predominant isoform in 82% of ER+, 68% of ER-, and 100% of HR ER+ breast cancers.
• InsR-A expression was significantly higher than InsR-B in ER+ and HR ER+ tumors compared to ER- tumors.
• HR ER+ tumors showed significantly reduced InsR-B expression, leading to elevated InsR-A:InsR-B ratios.

Conclusions:

• Validated, sensitive qPCR assays enable feasible amplification of InsR isoforms in FFPE tissues.
• Data indicate InsR-A predominance in breast cancer, supporting its investigation as a predictive biomarker.
• These assays are crucial for advancing the use of InsR-A and InsR-B in guiding IGF-targeted therapeutic strategies.