Ultra Rapid, One Step Molecular Detection of BCR-ABL Major and Minor Transcripts by Isothermal RT-Loop Mediated Amplification Reaction.

Abstract

2515 Background: The molecular identification of the BCRABL transcripts in clinical samples is actually based on a conventional Reverse Transcription Polymerase Chain reaction (RT-PCR). Here we present a novel molecular method, based on Loop Mediated Amplification assay that, starting from RNA (RT-LAMP) in one single tube reaction ensures a rapid and simultaneous detection of either the BCR-ABL p190 or p210 fusion transcript as well as the housekeeping gene used as internal quality control. Methods: The BCR-ABL RT-LAMP is a multiplex, isothermal method for retro-transcription, amplification and detection of the Minor (p190) and Major (p210) t(9;22) transcripts and the endogenous Gusb RNA, as internal control for validation of negative results. The employment of fluorescent specific probes allows real-time monitoring of the reaction, so that the test result is obtained in a single, homogeneous step. RT-LAMP is carried out on the Liaison IAM, a 8-wells manageable instrument suitable for isothermal reactions. Liaison IAM incubates at constant temperature, monitors the fluorescent signals and the data produced can be analyzed, upon connection to up to 6 other instruments, for a throughput of 8 to 48 samples. Thanks to the three channels of fluorescence, it can monitor multiplex assays, providing elaborated final objective results with no need of further data analysis by the operator. Results: The level of sensitivity of the triplex BCR-ABL RT-LAMP has been analytically evaluated directly on serial dilutions of RNA extracted respectively from t(9;22) positive cell lines (TOM-1 for p190 or K-562 for p210) into wild type RNA from HL-60 cell line (30 replicates). The p190 and p210 transcripts have been detected and distinguished down to 10−4 and 10−5respectively within 50 minutes. The assay demonstrated 100% specificity since 70 replicates of wild type RNA from 7 cell lines resulted BCR-ABL negative and GUSb positive (internal amplification control). This assay was validated on 60 clinical samples (30 white blood cells RNA from Chronic Myeloid Leukemia, 30 mononuclear cells RNA from B-lineage Acute Lymphoblastic Leukemia). All these samples were obtained at diagnosis and were previously analyzed by conventional RT-PCR. RT-LAMP detected and identified the BCR-ABL fusion transcripts correctly in all cases with a 100% concordance with the reference method. Fully concordant results were obtained also on 30 RNA samples from patients affected by t(9;22) negative hematologic malignancies and on 30 RNA samples obtained from healthy donors in which the RT-LAMP amplified exclusively the housekeeping GUSb transcript. Conclusions: The triplex p190-p210-GUSb RT-LAMP is a one-step procedure for specific, highly sensitive and rapid molecular detection of the BCR-ABL fusion transcripts. The semi-automatic instrument Liaison IAM, simplifies the entire procedure, reduces the contamination risks deriving from the conventional, multi step RT-PCR and significantly improve the diagnostic lab routine. Disclosures: D'agostini: DIASORIN S.p.A: Employment. Minnucci:Diasorin S.p.A.: Employment. Amicarelli:DIASPRIN S.p.A.: Employment. Pultrone:DIASORIN S.p.A.: Employment. Tettamanzi:DIASORIN S.p.A.: Employment. Salmoiraghi:DIASORIN S.p.A.: Consultancy. Spinelli:DIASORIN S.p.A: Consultancy. Colotta:DIASORIN S.p.A: Employment. Rambaldi:DIASORIN S.p.A: Consultancy.