Hypoxia-inducible factor 1 (HIF-1) is a crucial transcription factor for the cellular adaptive response to hypoxia, which contributes to multiple events in cancer biology. MicroRNAs (miRNAs) are involved in almost all cellular activities such as differentiation, proliferation, and apoptosis. In this work, we use miRNA microarrays to profile miRNA expression in acute myeloid leukemia (AML) cells with inducible HIF-1a expression, and identify 19 differentially expressed miRNAs. Our study shows that HIF-1a represses the expression of miR-17 and miR-20a by downregulating c-Myc expression. These two miRNAs alleviate hypoxia and HIF-1a-induced differentiation of AML cells. More intriguingly, miR-17 and miR-20a directly inhibit the p21 and STAT3 (signal transducer and activator of transcription 3) expression, both of which can reverse miR-17/miR-20a-mediated abrogation of HIF-1a-induced differentiation. Moreover, we show in vivo that miR-20a contributes to HIF-1a-induced differentiation of leukemic cells. Taken together, our results suggest that HIF-1a regulates the miRNA network to interfere with AML cell differentiation, representing a novel molecular mechanism for HIF-1-mediated anti-leukemic action. Hypoxia-inducible factor-1 (HIF-1), a heterodimeric transcriptional factor that consists of the oxygen-sensitive alpha subunit (HIF-1a) and the constitutively expressed beta subunit (HIF-1b), is a master regulator for the cellular adaptive response to oxygen concentration. 1 Under normoxic conditions, proline residues 402 and 564 of the HIF-1a protein are hydroxylated by specific prolyl hydroxylases (PHDs) that utilize O 2 and a-ketoglutarate as co-factors. The hydroxylated HIF-1a protein is subject to ubiquitination by the E3 ubiquitin ligase von Hippel-Lindau (VHL), which leads to its degradation. In contrast, hypoxic conditions cause the accumulation of HIF-1a protein by inhibiting its hydroxylation, and subsequent ubiquitination and degradation. 2 The stabilized HIF-1a protein translocates into the nucleus, where it forms a heterodimer with HIF-1b and modulates the expression of hundreds of genes through binding to hypoxia-responsive elements (HREs; 5 0 -RCGTG-3 0 ) on their promoters. These HIF-1-targeted genes help the cell adapt to hypoxia by influencing processes such as erythropoiesis, angiogenesis, cell metabolism, growth, apoptosis, and differentiation.Intriguingly, HIF-1a has been shown to contribute to the pathogenesis and progression of multiple kinds of diseases, including cancer. 1,3 Although a hypoxic microenvironment is regarded as a hallmark of solid tumors, and hypoxia-stabilized HIF-1a protein contributes to tumor growth, angiogenesis, and metastasis, 4 several groups, including our own, have reported that HIF-1a protein can trigger acute myeloid leukemia (AML) cells to undergo differentiation through a transcription-independent mechanism, inhibiting the progression of AML. [5][6][7][8][9] MicroRNAs (miRNAs) are a distinct class of small noncoding RNAs of around 22 nucleotides in length that posttra...

Leukemia-associated fusion protein AML1-ETO is a product of the chromosome translocation (8;21) frequently occurred in acute myeloid leukemia (AML). The fusion oncoprotein blocks leukemic cell differentiation, and it also induces growth arrest with increased sensitivity to apoptosis induction. Such dichotomous functions make it difficult to clarify the role of AML1-ETO in leukemogenesis. Here, we systematically showed that constitutively and overexpressed AML1-ETO protein was cleaved to four fragments of 70, 49, 40 and 25 kDa by activated caspase-3 during apoptosis induction by extrinsic mitochondrial and death receptor signaling pathways. The in vitro proteolytic system combined with MALDI-TOF/TOF mass spectrometer confirmed that AML1-ETO and wild-type ETO but not RUNX1 (AML1) proteins were direct substrates of apoptosis executioner caspase-3. Site-directed mutagenesis analyses identified two nonclassical aspartates (TMPD 188 and LLLD 368 ) as caspase-3-targeted sites in the AML1-ETO sequence. When these two aspartates were mutated into alanines, more intriguingly, the apoptosis-amplified action of AML1-ETO induction completely disappeared, while inducible expression of the caspase-3-cleaved 70 kDa fragment of AML1-ETO after tetracycline removal is sufficient to enhance apoptotic sensitivity. Further investigations on the potential in vivo effects of such a cleavage and its possible role in leukemogenesis would provide new insights for understanding the biology and treatment of AML1-ETO-associated leukemia.

Aberrant activation of nuclear factor-κB (NF-κB) has been observed in a wide range of human cancers and is thought to promote tumorigenesis and metastasis. As a central component of NF-κB pathway, p65 protein level is tightly regulated and could be subjected to proteasome degradation. Here we demonstrated that p65 can bind to HSC70 with four consensus recognition motif in its RHD domain and be constitutively transported to the lysosome membrane to bind with lysosome-associated membrane protein type 2A and degraded within the lysosome in two epithelial cell lines, proposing that p65 can be degraded by chaperone-mediated autophagy (CMA). Of great importance, there is a decreased CMA activity together with impaired degradation of p65 in a process of epithelial–mesenchymal transition (EMT). The resulted accumulation of p65 leads to higher NF-κB activity and contributes to the progression and maintenance of the EMT program. Taken together, our results define a novel regulatory mechanism for the important transcription factor p65, and these findings would shed new light on the inhibition of EMT, as well as metastasis of cancer cells.

Background:Primary bone lymphoma (PBL) is an uncommon extranodal disease that represents approximately 1-3% of lymphomas. ALK positive anaplastic large-cell lymphoma (ALCL) is an extremely rare type of PBL. The aim of this report is describe the symptoms, diagnosis and treatment of primary bone ALK-positive ALCL.Case presentation:A 66-year-old man presented with neck and shoulder pain and intermittent fever that lasted for one month to our hospital.After extensive evaluation, positron emission tomography (PET)-CT examination showed multiple osteolytic bone lesions without other sites lesions. CT-guided biopsy of the T10 vertebral body was performed, and the pathology results showed neoplastic cells were positive for ALK-1, CD30 and CD3. A diagnosis of primary bone ALK positive ALCL was ultimately made. The patient received four cycles of CHOP chemotherapy , and we planned to repeat the biopsy and radiological examination after completion of the fifth cycle of therapy.Conclusions:Primary bone ALK positive anaplastic large cell lymphoma is a rare disease and physicians should keep in mind that ALCL can present with isolated osseous involvement without nodal involvement, and lymphoma should be considered in the differential diagnosis of primary bone lesions.