miR-638 in circulating leukaemia cells as a non-invasive biomarker in diagnosis, treatment response and MRD surveillance of acute promyelocytic leukaemia.

Background MicroRNA (miRNA) expression has been implicated in leukaemia. In recent years, miRNAs have been under investigation for their potential as non-invasive biomarkers in acute promyelocytic leukaemia (APL). We investigated whether miR-638 in circulating leukaemia cells is a non-invasive biomarker in diagnosis, assessment of the treatment response and minimal residual disease (MRD) surveillance of APL. Methods Sixty cases of acute myeloid leukaemia (AML), including 30 cases of APL and 30 cases of non-APL AML, were selected. Thirty healthy controls were also selected. Bone marrow (BM) and peripheral blood (PB) samples were collected from APL patients at diagnosis and post-induction. Microarray analysis and quantitative real-time PCR (qRT-PCR) were performed for miRNA profiling and miR-638 expression analysis, respectively. For statistical analysis, Mann-Whitney U test, Wilcoxon Signed Rank test, receiver operating characteristic (ROC) curve analysis and Spearman's rho correlation test were used. Results Both microarray and qRT-PCR data showed that miR-638 was significantly upregulated in BM after APL patients received induction therapy. Moreover, miR-638, which is specifically downregulated in APL cell lines, was upregulated after all-trans retinoic acid (ATRA)-induced myeloid differentiation. Receiver operating characteristic (ROC) curve analyses revealed that miR-638 could serve as a valuable biomarker for differentiating APL from controls or non-APL AML. Furthermore, miR-638 expression was sharply increased after induction therapy and complete remission (CR). An inverse correlation was observed between miR-638 and PML-RARα transcripts levels in BM samples, while a positive correlation was revealed between PB miR-638 and BM miR-638 levels in APL patients after induction therapy. Conclusions Our study suggested that miR-638 may serve as a potential APL biomarker for diagnosis and assessment of the response to targeted therapy, and PB miR-638 could be used for non-invasive MRD surveillance in APL.