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The myelodysplastic syndromes (MDS) comprise a heterogeneous group of malignant neoplasms with distinctive clinicopathological features. Currently, there is no specific approach for the treatment of MDS. Here, we report that bortezomib (BTZ), a proteasome inhibitor that has been used to treat plasma cell myeloma, induced G2/M phase cycle arrest in the MDS cell line SKM-1 through upregulation of Wee1, a negative regulator of G2/M phase transition. Treatment by BTZ led to reduced SKM-1 cell viability as well as increased apoptosis and autophagy. The BTZ-induced cell death was associated with reduced expression of p-ERK. To elucidate the implications of downregulation of p-ERK, we established the BTZ resistant cell line SKM-1R. Our data show that resistance to BTZ-induced apoptosis could be reversed by the MEK inhibitors U0126 or PD98059. Our results suggest that MAPK pathway may play an important role in mediating BTZ resistance. [ABSTRACT FROM AUTHOR]

Long non-coding RNAs (lncRNAs) are important in cancer biology. In this study, we analyzed differentially expressed genes in CD34 + hematopoietic cells and identified a novel lncRNA, H22954, which was down-regulated in acute myeloid leukemia (AML) patients. In cultured AML cells and mouse xenograft models, H22954 expression inhibited cell proliferation and tumor growth, respectively. Bioinformatic analysis and RNA antisense purification assay indicated that H22954 targeted the 3' untranslated region of the BCL2 gene. In luciferase assays, H22954 expression inhibited BCL2 expression. In transfected K562 cells and mouse xenograft tumors, H22954 overexpression reduced BCL-2 protein levels and promoted cell death. In AML patients, H22954 expression inversely correlated with BCL-2 protein levels in bone marrow cells, blast cell numbers and disease prognosis. These results indicate that H22954 is a novel regulator of BCL-2 and that reduced H22954 expression may play an important role in the pathogenesis of AML. [ABSTRACT FROM AUTHOR]