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Technical validation of an RT-qPCR in vitro diagnostic test system for the determination of breast cancer molecular subtypes by quantification of ERBB2, ESR1, PGR and MKI67 mRNA levels from formalin-fixed paraffin-embedded breast tumor specimens.

ABSTRACT: MammaTyper is a novel CE-marked in vitro diagnostic RT-qPCR assay which assigns routinely processed breast cancer specimens into the molecular subtypes Luminal A-like, Luminal B-like (HER2 positive or negative), HER2 positive (non-luminal) and Triple negative (ductal) according to the mRNA expression of ERBB2, ESR1, PGR and MKI67 and the St Gallen consensus surrogate clinical definition. Until now and regarding formalin-fixed, paraffin-embedded material (FFPE), this has been a task mostly accomplished by immunohistochemistry (IHC). However the discrepancy rates of IHC for the four breast cancer biomarkers are frequently under debate, especially for Ki-67 which carries the highest degree of inter- and even intra-observer variability. Herein we describe a series of studies in FFPE specimens which aim to fully validate the analytical performance of the MammaTyper assay, including the site to site reproducibility of the individual marker measurements.Tumor RNA was extracted with the novel RNXtract RNA extraction kit. Synthetic RNA was used to assess the sensitivity of the RNXtract kit. DNA and RNA specific qPCR assays were used so as to determine analyte specificity of RNXtract. For the assessment of limit of blank, limit of detection, analytical measurement range and PCR efficiency of the MammaTyper kit serial dilutions of samples were used. Analytical precision studies of MammaTyper were built around two different real time PCR platforms and involved breast tumor samples belonging to different subtypes analyzed across multiple sites and under various stipulated conditions. The MammaTyper assay robustness was tested against RNA input variations, alternative extraction methods and tumor cell content.Individual assays were linear up to at least 32.33 and 33.56 Cqs (quantification cycles) for the two qPCR platforms tested. PCR efficiency ranged from 99 to 109 %. In qPCR platform 1, estimates for assay specific inter-site standard deviations (SD) were between 0.14 and 0.20 Cqs accompanied by >94 % concordant single marker assignments for all four markers. In platform 2, the inter-site SD estimates were between 0.40 and 0.66 Cqs while the concordance for single marker assignments was >94 % for all four markers. The agreement reached between the two qPCR systems located in one site was 100 % for ERBB2, 96.9 % for ESR1, 97.2 % for PGR and 98.6 % for MKI67. RT-qPCR for individual markers was stable up to a 64-fold dilution for a typical clinical sample. There was no change in assay performance detected at the level of individual markers or subtypes after using different RNA isolation methods. The presence of up to 80 % of surrounding non-tumor tissue including in situ carcinoma did not affect the assay output. Sixteen out of 20 RNXtract eluates yielded more than 50 ng/?l of RNA (average RNA output: 233 ng/?l), whereas DNA contamination per sample was restricted to less than 15 ng/?l. Median recovery rate of RNA extraction was 91.0 %.In this study the performance characteristics of MammaTyper were successfully validated. The various sources of analytical perturbations resulted in negligible variations in individual marker assessments. Therefore, MammaTyper may serve as a technical improvement to current standards for decentralized FFPE-based routine assessment of the commonly used breast cancer biomarkers and for molecular subtyping of breast cancer specimens.

SUBMITTER: Laible M

PROVIDER: S-EPMC4936300 | biostudies-other | 2016 Jul

REPOSITORIES: biostudies-other

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Technical validation of an RT-qPCR in vitro diagnostic test system for the determination of breast cancer molecular subtypes by quantification of ERBB2, ESR1, PGR and MKI67 mRNA levels from formalin-fixed paraffin-embedded breast tumor specimens.

Laible Mark M Schlombs Kornelia K Kaiser Katharina K Veltrup Elke E Herlein Stefanie S Lakis Sotiris S Stöhr Robert R Eidt Sebastian S Hartmann Arndt A Wirtz Ralph M RM Sahin Ugur U

BMC cancer 20160707

<h4>Background</h4>MammaTyper is a novel CE-marked in vitro diagnostic RT-qPCR assay which assigns routinely processed breast cancer specimens into the molecular subtypes Luminal A-like, Luminal B-like (HER2 positive or negative), HER2 positive (non-luminal) and Triple negative (ductal) according to the mRNA expression of ERBB2, ESR1, PGR and MKI67 and the St Gallen consensus surrogate clinical definition. Until now and regarding formalin-fixed, paraffin-embedded material (FFPE), this has been a ...[more]

PMID: 27389414

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Project description:BACKGROUND: The ability of gene profiling to predict treatment response and prognosis in breast cancers has been demonstrated in many studies using DNA microarray analyses on RNA from fresh frozen tumor specimens. In certain clinical and research situations, performing such analyses on archival formalin fixed paraffin-embedded (FFPE) surgical specimens would be advantageous as large libraries of such specimens with long-term follow-up data are widely available. However, FFPE tissue processing can cause fragmentation and chemical modifications of the RNA. A number of recent technical advances have been reported to overcome these issues. Our current study evaluates whether or not the technology is ready for clinical applications. METHODS: A modified RNA extraction method and a recent DNA microarray technique, cDNA-mediated annealing, selection, extension and ligation (DASL, Illumina Inc) were evaluated. The gene profiles generated from FFPE specimens were compared to those obtained from paired fresh fine needle aspiration biopsies (FNAB) of 25 breast cancers of different clinical subtypes (based on ER and Her2/neu status). Selected RNA levels were validated using RT-qPCR, and two public databases were used to demonstrate the prognostic significance of the gene profiles generated from FFPE specimens. RESULTS: Compared to FNAB, RNA isolated from FFPE samples was relatively more degraded, nonetheless, over 80% of the RNA samples were deemed suitable for subsequent DASL assay. Despite a higher noise level, a set of genes from FFPE specimens correlated very well with the gene profiles obtained from FNAB, and could differentiate breast cancer subtypes. Expression levels of these genes were validated using RT-qPCR. Finally, for the first time we correlated gene expression profiles from FFPE samples to survival using two independent microarray databases. Specifically, over-expression of ANLN and KIF2C, and under-expression of MAPT strongly correlated with poor outcomes in breast cancer patients. CONCLUSION: We demonstrated that FFPE specimens retained important prognostic information that could be identified using a recent gene profiling technology. Our study supports the use of FFPE specimens for the development and refinement of prognostic gene signatures for breast cancer. Clinical applications of such prognostic gene profiles await future large-scale validation studies.

Project description:BackgroundThe purpose of this study was to assess the concordance of real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) detection of ESR1, PGR, ERBB2, and MKi67 messenger RNA (mRNA) in breast cancer tissues with central immunohistochemistry (IHC) in women treated within the prospective, randomized Austrian Breast and Colorectal Cancer Study Group (ABCSG) Trial 6.Patients and methodsWe evaluated ESR1, PGR, ERBB2, and MKi67 mRNA expression by Xpert® Breast Cancer STRAT4 (enables cartridge-based RT-qPCR detection of mRNA in formalin-fixed paraffin-embedded tissues) and estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and Ki67 protein expression by IHC [in situ hybridization (ISH) for HER2 IHC 2+] in 1115 surgical formalin-fixed paraffin-embedded specimens from patients of ABCSG Trial 6. Overall percent agreement (concordance), positive percent agreement (sensitivity), and negative percent agreement (specificity) between STRAT4 and IHC were determined for each marker. The primary objective of the study was concordance between STRAT4 mRNA measurements of ESR1, PGR, ERBB2, and MKi67 with central reference laboratory IHC (and ISH for HER2 IHC 2+ cases). Time to distant recurrence was analyzed by Cox models.ResultsAll performance targets for ER, PR, and Ki67 were met. For HER2, the negative percent agreement target but not the positive percent agreement target was met. Concordance between STRAT4 and IHC was 98.9% for ER, 89.9% for PR, 98.2% for HER2, and 84.8% for Ki67 (excluding intermediate IHC 10%-20% staining). In univariable and multivariable Cox regression analyses, all four biomarkers tested by either STRAT4 RT-qPCR or by central IHC (ISH) had a comparable time to distant recurrence indicating similar prognostic value.ConclusionsWith the exception of HER2, we demonstrate high concordance between centrally assessed IHC and mRNA measurements of ER, PR, and Ki67 as well as a high correlation of the two methods with clinical outcome. Thus, mRNA-based assessment by STRAT4 is a promising new tool for diagnostic and therapeutic decisions in breast cancer.

Dataset Information

Technical validation of an RT-qPCR in vitro diagnostic test system for the determination of breast cancer molecular subtypes by quantification of ERBB2, ESR1, PGR and MKI67 mRNA levels from formalin-fixed paraffin-embedded breast tumor specimens.

Publications

Technical validation of an RT-qPCR in vitro diagnostic test system for the determination of breast cancer molecular subtypes by quantification of ERBB2, ESR1, PGR and MKI67 mRNA levels from formalin-fixed paraffin-embedded breast tumor specimens.

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