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Quantifying insulin receptor isoform expression in FFPE breast tumors.

ABSTRACT: The development of predictive biomarkers for IGF targeted anti-cancer therapeutics remains a critical unmet need. The insulin receptor A isoform (InsR-A) has been identified as a possible biomarker candidate but quantification of InsR-A in widely available formalin fixed paraffin embedded (FFPE) tissues is complicated by its similarities with the metabolic signaling insulin receptor isoform B (InsR-B). In the present study, qPCR based assays specific for InsR-A, InsR-B and IGF-1R were developed for use in FFPE tissues and tested for feasible use in clinical archived FFPE estrogen receptor (ER)+and ER- breast cancer tumors.FFPE compatible primer sets were designed with amplicon sizes of less than 60 base pairs and validated for target specificity, assay repeatability and amplification efficiency. FFPE tumors from ER+ (n=83) and ER-(n=64) primary untreated breast cancers, and ER+ hormone refractory (HR ER+) (n=61) breast cancers were identified for feasibility testing. The feasible use of InsR-A and InsR-B qPCRs were tested using all tumor groups and the feasibility of IGF-1R qPCR was determined using HR ER+ tumors.All qPCR assays were highly reproducible with amplification efficiencies between 96-104% over a 6 log range with limits of detection of 4 or 5 copies per reaction. Greater than 90% of samples were successfully amplified using InsR-A, InsR-B or IGF-1R qPCR primer sets and greater than 88% of samples tested amplified both InsR isoforms or both isoforms and IGF-1R. InsR-A was the predominant isoform in 82% ER+, 68% ER- and 100% HR ER+ breast cancer. Exploratory analyses demonstrated significantly more InsR-A expression in ER+ and HR ER+ groups compared to InsR-B (ER+ p<0.05, HR ER+ p<0.0005) and both groups had greater InsR-A expression when compared to ER- tumors (ER+ p<0.0005, HR ER+ p<0.05). IGF-1R expression of HR ER+ tumors was lower than InsR-A (p<0.0005) but higher than InsR-B (p<0.0005). The InsR-B expression of HR ER+ tumors was significantly reduced compared other tumor subgroups (ER+ and ER-, p<0.0005) and lead to a significant elevation of HR ER+ InsR-A: InsR-B ratios (ER+ and ER-, p<0.0005).The validated, highly sensitive InsR-A and InsR-B qPCR based assays presented here are the first to demonstrate the feasible amplification of InsR isoforms in FFPE tissues. Quantification data generated from this feasibility study indicating InsR-A is more predominant than InsR-B in breast cancer support the use of these assays for further investigation of InsR-A and InsR-B as predictive biomarkers for IGF targeted therapeutics.

SUBMITTER: Harrington SC

PROVIDER: S-EPMC3392524 | biostudies-literature | 2012 Jun-Aug

REPOSITORIES: biostudies-literature

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Quantifying insulin receptor isoform expression in FFPE breast tumors.

Harrington Sean C SC Weroha S John SJ Reynolds Carol C Suman Vera J VJ Lingle Wilma L WL Haluska Paul P

Growth hormone & IGF research : official journal of the Growth Hormone Research Society and the International IGF Research Society 20120430 3-4

<h4>Background</h4>The development of predictive biomarkers for IGF targeted anti-cancer therapeutics remains a critical unmet need. The insulin receptor A isoform (InsR-A) has been identified as a possible biomarker candidate but quantification of InsR-A in widely available formalin fixed paraffin embedded (FFPE) tissues is complicated by its similarities with the metabolic signaling insulin receptor isoform B (InsR-B). In the present study, qPCR based assays specific for InsR-A, InsR-B and IGF ...[more]

PMID: 22551578

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Project description:BackgroundThe insulin receptor (INSR) and the insulin growth factor 1 receptor (IGF1R) play important roles in the etiology of both diabetes mellitus and breast cancer. We aimed to evaluate the expression of hormone and insulin-related proteins within or related to the PI3K and MAPK pathway in breast tumors of women with or without diabetes mellitus, treated with or without insulin (analogues).MethodsImmunohistochemistry was performed on tumor tissue of 312 women with invasive breast cancer, with or without pre-existing diabetes mellitus, diagnosed in 2000-2010, who were randomly selected from a Danish breast cancer cohort. Women with diabetes were 2:1 frequency matched by year of birth and age at breast cancer diagnosis to those without diabetes. Tumor Microarrays were successfully stained for p-ER, EGFR, p-ERK1/2, p-mTOR, and IGF1R, and scored by a breast pathologist. Associations of expression of these proteins with diabetes, insulin treatment (human insulin and insulin analogues) and other diabetes medication were evaluated by multivariable logistic regression adjusting for menopause and BMI; effect modification by menopausal status, BMI, and ER status was assessed using interactions terms.ResultsWe found no significant differences in expression of any of the proteins in breast tumors of women with (n?=?211) and without diabetes (n?=?101). Among women with diabetes, insulin use (n?=?53) was significantly associated with higher tumor protein expression of IGF1R (OR?=?2.36; 95%CI:1.02-5.52; p?=?0.04) and p-mTOR (OR?=?2.35; 95%CI:1.13-4.88; p?=?0.02), especially among women treated with insulin analogues. Menopause seemed to modified the association between insulin and IGF1R expression (p?=?0.07); the difference in IGF1R expression was only observed in tumors of premenopausal women (OR?=?5.10; 95%CI:1.36-19.14; p?=?0.02). We found no associations between other types of diabetes medication, such as metformin, and protein expression of the five proteins evaluated.ConclusionsIn our study, breast tumors of women with pre-existing diabetes did not show an altered expression of selected PI3K/MAPK pathway-related proteins. We observed an association between insulin treatment and increased p-mTOR and IGF1R expression of breast tumors, especially in premenopausal women. This observation, if confirmed, might be clinically relevant since the use of IGF1R and mTOR inhibitors are currently investigated in clinical trials.

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Quantifying insulin receptor isoform expression in FFPE breast tumors.

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Quantifying insulin receptor isoform expression in FFPE breast tumors.

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