Degradation of p47 by autophagy contributes to CADM1 overexpression in ATLL cells through the activation of NF-κB.

Cell adhesion molecule 1 (CADM1), a member of the immunoglobulin superfamily, is identified as a novel cell surface marker for human T-cell leukemia virus (HTLV-1)-infected T cells. Adult T-cell leukemia/lymphoma (ATLL) is developed in HTLV-1-infected T-cells after a long infection period. To examine the mechanism of CADM1 overexpression in ATLL, we first identified that CADM1 is transcriptionally up-regulated by a transcriptional enhancer element through NF-κB signaling pathway. In HTLV-1-infected T-cells, CADM1 expression is dependent on HTLV-1/Tax through activation of canonical and non-canonical NF-κB; however, in ATLL cells with frequent loss of Tax expression, the activation of canonical NF-κB only enhances the CADM1 expression. Along with active mutations in signaling molecules under T-cell recepor (TCR) signaling, degradation of p47, a negative regulator of NF-κB, was essential for activation of canonical NF-κB through stabilization of NEMO (NF-κB essential modulator). The mechanism of p47 degradation is primarily dependent on activation of lysosomal-autophagy and the autophagy is activated in most of the HTLV-infected and ATLL cells, suggesting that the p47 degradation may be a first key molecular event during HTLV-1 infection to T-cells as a connector of two important signaling pathways, NF-κB and autophagy.

MZF-1 and DbpA interact with DNase I hypersensitive sites that correlate with expression of the human MUC1 mucin gene.

The MUC1 mucin is a large membrane-tethered glycoprotein that shows differential expression in many adenocarcinomas, where it contributes to their invasive and metastatic properties. We previously identified DNase I hypersensitive sites at -750 and -250 bp in the human MUC1 gene promoter and showed concordance between the -250 site and MUC1 mRNA levels in vivo. Transient expression assays using promoter constructs, in which the core DHS was deleted, to drive reporter gene expression revealed in vivo evidence for their activity. DNase I footprinting using nuclear extracts from HPAF human pancreatic carcinoma cells and MCF7 breast carcinoma cells identified three protein-binding elements in these regions (-250FP1, FP2 and -750FP). Electrophoretic mobility shift assays detected several complexes between HPAF nuclear proteins and labeled FP DNA probes. Southwestern blots and UV cross-linking experiments identified myeloid zinc finger-1 (MZF-1) as a candidate transcription factor among proteins binding to the -250FP1 and FP2 sequences. Another candidate that was identified by screening an HPAF cDNA expression library with the -250FP1 probe is DNA binding protein A (DbpA). Exogenous DbpA expression in COS-7 cells was accompanied by upregulation of MUC1 promoter activity via the -250 DHS, suggesting that DbpA binding to the -250 DHS can influence human MUC1 gene expression.

Overexpression of a cell adhesion molecule, TSLC1, as a possible molecular marker for acute-type adult T-cell leukemia.

Adult T-cell leukemia (ATL) caused by human T-cell leukemia virus type 1 (HTLV-1) infection, occurs in 2% to 4% of the HTLV-1 carriers with a long latent period, suggesting that additional alterations participate in the development of ATL. To characterize and identify novel markers of ATL, we examined the expression profiles of more than 12 000 genes in 8 cases of acute-type ATL using microarray. One hundred ninety-two genes containing interleukin 2 (IL-2) receptor alpha were up-regulated more than 2-fold compared with CD4(+) and CD4(+)CD45RO(+) T cells, and tumor suppressor in lung cancer 1 (TSLC1), caveolin 1, and prostaglandin D2 synthase showed increased expression of more than 30-fold. TSLC1 is a cell adhesion molecule originally identified as a tumor suppressor in the lung but lacks its expression in normal or activated T cells. We confirmed ectopic expression of the TSLC1 in all acute-type ATL cells and in 7 of 10 ATL- or HTLV-1-infected T-cell lines. Introduction of TSLC1 into a human ATL cell line ED enhanced both self-aggregation and adhesion ability to vascular endothelial cells. These results suggested that the ectopic expression of TSLC1 could provide a novel marker for acute-type ATL and may participate in tissue invasion, a characteristic feature of the malignant ATL cells.

Identification of two novel elements involved in human MUCI gene expression in vivo.

BACKGROUND: MUC1, a membrane-tethered glycoprotein that is expressed on a number of epithelial cell types in vivo, is over-expressed in adenocarcinomas and thought to play a significant role in tumour progression and metastasis. Hence, elucidation of the mechanisms of regulation of MUC1 gene expression is of considerable biological importance. Our aim was to evaluate regulation of MUC1 expression in vivo. MATERIALS AND METHODS: DNase I hypersensitive sites (DHS) were mapped in chromatin from human cell lines and human MUC1 transgenic mice. MUC1 expression was evaluated by RT-PCR and Northern blots. RESULTS: We identified two novel DHS in the MUC1 promoter at -750 bp and -250 bp from the transcriptional start site. These DHS were detected in human cell lines and in a human MUC1 transgene in mice. The -750 DHS was apparent in many cell types irrespective of the level of MUC1 expression but the -250 DHS was only evident in cells that express MUC1 and its intensity correlated with the abundance of MUC1 transcripts. The -250 DHS became undetectable in cell lines representing a transition from colon adenoma to carcinoma, commensurate with a significant reduction in MUC1 expression. CONCLUSIONS: The -750 and -250 regions are conserved between the human MUC1 and mouse Muc1 genes and may be associated with functionally important genetic elements. The DHS at -250 is in the vicinity of previously defined purine/pyrimidine mirror repeat elements that may form intramolecular H-DNA structures, which can alter the accessibility of chromatin to regulatory proteins.