Abstract 5538: Development of RNA quality control methods to improve BCR-ABL measurement in whole blood samples

Abstract Measurement of BCR-ABL fusion transcripts in whole blood by quantitative, reverse-transcriptase PCR is a clinically validated method to monitor treatment response in patients with chronic myelogenous leukemia. For example, achieving a three-log or greater reduction in BCR-ABL expression from baseline is considered a Maximum Molecular Response (MMR). A 0.5-log increase from MMR signifies treatment failure sufficient to motivate change in treatment. The purpose of this study was to develop a BCR-ABL test with improved analytical performance characteristics including adequate quality control for RNA degradation or reverse transcription interference and reliable comparison of results across testing sites. To test whether RNA degradation could mask a 0.5-log increase in expression, an RNA degradation model was established by incubating whole blood from each of six individuals with K562 cells at room temperature for various times post-venipuncture. When data from six subjects were combined, the BCR-ABL/103 GUSB value trended down at 24h but was not significantly decreased until 48h (51% decrease, p = 0.004). To quantify the amount of whole blood RNA that can be loaded into an RT reaction without reducing RT efficiency, six different amounts of total RNA extracted from whole blood mixed with K562 cells were added into RT reactions. To measure RT efficiency, an RT Standards Mixture (RTSM) containing known copy numbers of External RNA Control Consortium (ERCC) 171 RNA and ERCC 113 cDNA was added to each RT reaction. RT efficiency was measured as the yield of PCR product from ERCC 171 RNA relative to ERCC 113 cDNA. Based on data from three subjects, compared to RT efficiency at reference concentration of 30 ng/µl RNA in RT, there was a 35% decrease (p = 0.043) at 167 ng/μl RNA and 82% reduction at 1000 ng/μl RNA. The maximum yield of BCR-ABL (molecules/μL cDNA) was observed at 300 ng/µl RNA/RT with a 3-fold increase (p=0.003) compared to 30 ng/µl RNA. Greater than 300 ng/µl RNA/RT did not further increase yield of BCR-ABL molecules/μL cDNA, likely due to reduced RT efficiency. We conclude that BCR-ABL/103 GUSB should be measured within 24 hours following blood collection. Because decreasing RT efficiency is associated with increasing RNA input into RT reactions, including 300 ng/µl RNA in RT reactions provides the maximum sensitivity in measuring BCR-ABL expression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5538. doi:1538-7445.AM2012-5538