Down-Regulation of MicroRNA-143 and -145 in Childhood B-Lineage Acute Lymphoblastic Leukemia at Initial Diagnosis and in Relapse but up-Regulated When in Remission

Inappropriate expression of microRNAs (miRNAs) is strongly associated with leukemogenesis. miRNAs (miRs)-143 and -145, previously shown to be reduced in colon cancers, have been demonstrated recently to be down-regulated in B-cell malignancies including chronic lymphoblastic leukemia, B-cell lymphoma, Burkitt’s lymphoma. In this study, we determined the role of miR-143 and miR-145 in childhood leukemia treated by the standard TPOG (Taiwan Pediatric Oncology Group)-2002 protocols approved for treatment of patients in Taiwan. Ten patients with childhood B-lineage ALL and four ALL leukemia cells lines including REH (CRL-8286TM), CCRF-SB (CCL-120TM), RS4 (CRL-1873TM), and SUP-B15 (CRL-1929) were measured for the miRNA expression using a TagMan quantitative RT-PCR method. Our results showed that miR-143 and miR-145 were both down-regulated 0.09 and 0.19 times individually (n= 13, p <0.001 and p = 0.011) in mononuclear cells in bone marrow of newly-diagnosed and relapsed samples in comparison with the same cell types of remission samples (n=16). To examine possible suppressive functions of miR-143 and miR-145 with respect to cell growth, the REH cells were used for expression with precursor form and mature form miR-143 and miR-145, and subsequently measured for cell growth rate. Preliminary results showed that the two miRNAs did not alter the growth rate of the REH over-expressing either miRNA. Taken together, we have identified miR-143 and miR-145 as biomarkers that may differentiate malignant and normal B cells. miR-143 and miR-145 may contribute to leukemogenesis in childhood B-lineage ALL by new yet to be defined mechanisms.