The existence of tumor-suppressor genes was originally demonstrated by functional complementation through whole-cell and microcell fusion. Transfer of chromosome 11 into a human non-small-cell lung cancer (NSCLC) cell line, A549, suppresses tumorigenicity. Loss of heterozygosity (LOH) on the long arm of chromosome 11 has been reported in NSCLC and other cancers. Several independent studies indicate that multiple tumor-suppressor genes are found in this region, including the gene PPP2R1B at 11q23-24 (ref. 7). Linkage studies of NSCLC are precluded because no hereditary forms are known. We previously identified a region of 700 kb on 11q23.2 that completely suppresses tumorigenicity of A549 human NSCLC cells. Most of this tumor-suppressor activity localizes to a 100-kb segment by functional complementation. Here we report that this region contains a single confirmed gene, TSLC1, whose expression is reduced or absent in A549 and several other NSCLC, hepatocellular carcinoma (HCC) and pancreatic cancer (PaC) cell lines. TSLC1 expression or suppression is correlated with promoter methylation state in these cell lines. Restoration of TSLC1 expression to normal or higher levels suppresses tumor formation by A549 cells in nude mice. Only 2 inactivating mutations of TSLC1 were discovered in 161 tumors and tumor cell lines, both among the 20 primary tumors with LOH for 11q23.2. Promoter methylation was observed in 15 of the other 18 primary NSCLC, HCC and PaC tumors with LOH for 11q23.2. Thus, attenuation of TSLC1 expression occurred in 85% of primary tumors with LOH. Hypermethylation of the TSLC1 promoter would seem to represent the 'second hit' in NSCLC with LOH.

We have recently identified a tumor suppressor gene TSLC1 on chromosome 11q23.2 by functional complementation of a human lung cancer cell line, A549, through suppression of tumorigenicity in nude mice (1). Furthermore, we have demonstrated the two-hit inactivation of TSLC1 in primary non-small cell lung cancer, hepatocellular carcinoma, and pancreatic cancer, implying its involvement in various human cancers (1). TSLC1 encodes a member of the immunoglobulin superfamily proteins comprising three Ig-like C2-type domains, a single hydrophobic membrane-spanning ␣-helix, and a cytoplasmic domain containing a putative signaling motif (1). From the significant homology of its extracellular domain with those of NCAM1 and NCAM2, 1 we have inferred that TSLC1 is capable of mediating cell-cell interaction.Cell adhesion molecules generally fall into four major classes: the cadherins, the integrins, the selectins, and the Ig superfamily. Among them, Ig superfamily cell adhesion molecules (IgCAMs) are the largest, numbering well over 100 members in vertebrates (2). These well-characterized molecules include NCAMs (3), L1 family CAMs (4), and nectins (5-8). Whereas cadherins and integrins require divalent cations such as Ca 2ϩ or Mg 2ϩ for their adhesive activities (9), IgCAMs are usually Ca 2ϩ -or Mg 2ϩ -independent (10). Moreover, most IgCAMs have preferences for homophilic and/or heterophilic interactions (10). In combination with these interactions, IgCAMs promote a variety of cell-cell associations through cis interaction within the plane of the membranes and/or trans interaction across the membranes (2, 11). For instance, the heterophilic cis interaction between L1 and NCAM appears to enhance the homophilic trans-binding activity of L1 (12, 13). Nectins form cis-homodimers that undergo homophilic and heterophilic trans interactions with each other to mediate cell-cell adhesion (6,11).In this study, the biochemical properties and subcellular localization of TSLC1 were investigated in the cells expressing TSLC1 tagged with GFP or endogenous TSLC1. We report the physiological properties of TSLC1 along with several lines of evidence that TSLC1 is a single transmembrane glycoprotein involved in cell-cell aggregation through homophilic trans interaction.

A bacterium capable of degrading microcystins-RR, -YR, and -LR was isolated from a hypertrophic lake. The bacterium, designated Y2 and classified phenotypically as a member of the genus Sphingomonas, was shown to be distinct phylogenetically from any established species of Sphingomonas on the basis of 16S rDNA sequencing. The bacterium was tentatively identified as Sphingomonas by manual chemotaxonomy, but 16S rRNA sequencing analysis suggests that it is in fact a new species or even a new genus. When the Y2 bacterium was added to microcystins present in culture medium, the microcystins were degraded thoroughly in 4 days. The highest degradation rates of microcystins-RR and -LR were 13 and 5.4 mg L-1 day-1, respectively. The degradation rates were strongly dependent on temperature and the maximum rate was at 30 degrees C.

Three strains of bacteria that degrade the cyanobacterial hepatotoxin microcystin, Y2 T , MDB2 and MDB3, were isolated from a eutrophic lake, Lake Suwa, and the Tenryu River, Japan, and characterized. These strains were aerobic and chemo-organotrophic and their cells were Gram-negative, non-spore-forming rods, motile by means of single polar flagella. Yellow-pigmented colonies were formed on nutrient agar media. The strains assimilated only citrate among the organic compounds tested as carbon sources. The G+C content of genomic DNA ranged from 63?6 to 63?7 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the new isolates formed a tight cluster within the family Sphingomonadaceae but were clearly separate from established genera of this family, e.g. Sphingomonas, Sphingobium, Novosphingobium and Sphingopyxis; sequence similarities between the new isolates and type strains from established genera ranged from 90?9 to 94?9 %. Chemotaxonomic and phenotypic data supported the conclusion that these strains were members of the family Sphingomonadaceae. The major components of the cellular fatty acids were 18 : 1v7c (36-41 %) and 16 : 1v7c (33-36 %). Hydroxy fatty acids were mainly 2-OH 14 : 0 (11-13 %), and 3-OH fatty acids were absent. Glycosphingolipids were detected. Ubiquinone-10 and homospermidine were present as the major quinine and polyamine, respectively. Thus, it is proposed that the three strains represent a new genus and species of the family Sphingomonadaceae with the name Sphingosinicella microcystinivorans gen. nov., sp. nov. The type strain is Y2 T (=KCTC 12019 T =JCM 13185 T ).

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