Calin, George A.

SummarymiR‐1258 is localised to the first intron of ZNF385B at chromosome 2q31.3. miR‐1258 promoter methylation was studied in 147 samples including 10 normal buffy coat, eight normal bone marrow plasma cells, 16 human myeloma cell lines (HMCLs), 20 MGUS, 63 diagnostic myeloma, and 30 relapsed myeloma samples by methylation‐specific PCR. In myeloma lines, miR‐1258 methylation, verified by pyrosequencing, was detected in 62·5% HMCLs but not normal controls, and expression of miR‐1258 correlated with that of ZNF385B. 5‐Aza‐2′‐deoxycytidine resulted in promoter demethylation and ZNF385B/miR‐1258 re‐expression. Luciferase assay confirmed programmed cell death ligand‐1 (PDL1) as a direct target of miR‐1258. Over‐expression of miR‐1258 in completely methylated myeloma cells led to reduced cellular proliferation and enhanced apoptosis, hence a tumour suppressor role, in addition to repression of PDL1. In primary samples, miR‐1258 methylation, with lower expression of miR‐1258, was detected in 49·2% diagnostic myeloma, imparting an inferior PFS (P = 0·034) in addition to 50·0% relapsed myeloma but not MGUS. Therefore, miR‐1258 is a tumour suppressor miRNA co‐regulated with its host gene, and frequently hypermethylated in active myeloma instead of MGUS, hence acquired during myeloma progression. Methylation‐mediated miR‐1258 silencing led to overexpression of PDL1 and inferior PFS, implicating miR‐1258 in the modulation of myeloma‐specific cytotoxicity.

Key Points miR-155 levels are significantly and increasingly overexpressed as normal B cells progress to MBL and to CLL. Plasma levels of miR-155 before treatment were significantly lower in patients with CLL who experienced complete response than in all others.

Abstract Oncogenic activation of Bmi-1 is found in a wide variety of epithelial malignancies including ovarian cancer, yet a specific mechanism for overexpression of Bmi-1 has not been determined. Thus, realizing the immense pathologic significance of Bmi-1 in cancer, we wanted to investigate if microRNA (miRNA) aberrations played a role in the regulation of Bmi-1 in ovarian cancer. In this report, we identify two miRNAs, miR-15a and miR-16, that are underexpressed in ovarian cell lines and in primary ovarian tissues. We show that these miRNAs directly target the Bmi-1 3′ untranslated region and significantly correlate with Bmi-1 protein levels in ovarian cancer patients and cell lines. Furthermore, Bmi-1 protein levels are downregulated in response to miR-15a or miR-16 expression and lead to significant reduction in ovarian cancer cell proliferation and clonal growth. These findings suggest the development of therapeutic strategies by restoring miR-15a and miR-16 expression in ovarian cancer and in other cancers that involve upregulation of Bmi-1. [Cancer Res 2009;69(23):9090–5]

The molecular mechanism of autocrine regulation of vascular endothelial growth factor (VEGF) in chronic lymphocytic leukemia (CLL) B cells is unknown. Here, we report that CLL B cells express constitutive levels of HIF-1α under normoxia. We have examined the status of the von Hippel-Lindau gene product (pVHL) that is responsible for HIF-1α degradation and found it to be at a notably low level in CLL B cells compared with normal B cells. We demonstrate that the microRNA, miR-92-1, overexpressed in CLL B cells, can target the VHL transcript to repress its expression. We found that the stabilized HIF-1α can form an active complex with the transcriptional coactivator p300 and phosphorylated-STAT3 at the VEGF promoter and recruit RNA polymerase II. This is initial evidence that pVHL, without any genetic alteration, can be regulated by microRNA and explains the aberrant autocrine VEGF secretion in CLL.