UCLA

Non-coding RNAs play pivotal roles in a wide variety of molecular processes. The functions of long non-coding RNAs (lncRNAs), in particular, have deep implications for both development and oncogenesis. Dysregulated expression of lncRNAs has been found in various cancers, but had not been comprehensively described in B lymphoblastic leukemia (B acute lymphoblastic leukemia; B-ALL). We completed a gene expression profiling study in human B-ALL samples and found differential lncRNA expression in samples with particular cytogenetic abnormalities. We determined that lncRNA expression could discriminate between B-ALL with specific karyotype abnormalities as well as, predict patient survival. Two promising lncRNAs from our study, designated B-ALL associated long RNAs (BALRs), have the highest expression in B-ALL samples carrying the MLL rearrangement when compared non-MLL rearranged and normal CD19+ cells. MLL rearranged B-ALL cases have a very poor prognosis and occur frequently in infants, making them particularly difficult to treat. This thesis investigates the role of lncRNAs BALR-2 and BALR-6 in MLL translocated B-ALL.

In the first part of this thesis work, we found that high expression of BALR-2 was correlated with diminished response to prednisone treatment. Knockdown led to a reduction in proliferation, increased apoptosis, and increased sensitivity to prednisolone treatment. Conversely, overexpression of the lncRNA caused increased cell growth and resistance to prednisone treatment. Remarkably, BALR-2 expression was repressed by prednisolone treatment and its dysregulation led to changes in the glucocorticoid response pathway in human and mouse B-cells. These findings indicate an important role for BALR-2 in the pathogenesis of B-ALL.

Much like BALR-2, siRNA mediated knockdown of BALR-6 in human B-ALL cell lines caused decreased proliferation and increased apoptosis. Additionally, overexpression of BALR-6 isoforms caused a significant increase in progenitor populations in mice and increased proliferation in mammalian cell lines. To understand the functional role of BALR-6, differential expression analysis from cell lines with knockdown was carried out. The analysis indicated an enrichment of genes involved in leukemia. Among these genes were SP1 and its known target genes. Luciferase reporter assays uncovered a positive regulatory role for BALR-6 in SP1 mediated transcription. Together, these data elucidate a role for BALR-6 in transcriptional regulation.

Thus, this thesis identifies novel non-coding RNA transcripts that regulate gene expression, and thereby pathogenesis in B-ALL with MLL rearrangement. This work suggests novel diagnostic, prognostic, and therapeutic utility for lncRNAs in B-ALL.