The human E48 antigen, highly homologous to the murine Ly-6 antigen ThB, is a GPI-anchored molecule apparently involved in keratinocyte cell-cell adhesion

Identification of DNA damage and repair gene-related markers in pancreatic ductal adenocarcinoma by single-cell and bulk RNA sequencing

BACKGROUND

The DNA damage response (DDR) has a major impact on the development and progression of pancreatic ductal adenocarcinoma (PDAC). Investigating biomarkers linked to the DDR may facilitate prognostic assessment and prediction of immunological characteristics for patients with PDAC.

METHODS

The single-cell RNA sequencing (scRNA-seq) dataset GSE212966 was obtained from the GEO database, whereas the bulk RNA-seq data were sourced from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases. Least absolute shrinkage and selection operator (LASSO) and univariate Cox regression analyses were used to select genes to construct a prognostic risk model. Finally, the correlations of the model score with drug sensitivity, immunological checkpoints, and immune infiltration were assessed.

RESULTS

We used 16 DDR marker genes to construct a predictive model. Furthermore, we established that the model had strong performance in both the training and validation cohorts. For PDAC, the model risk score served as an independent predictor of prognosis. There were notable differences in the proportions of the immune cells in the tumor microenvironment and drug sensitivity between the high and low risk score groups. The study confirmed that the risk score model is useful for predicting the immunotherapy response. Our experiments verified that knockdown of LY6D inhibits cell proliferation, promotes apoptosis and DNA damage.

CONCLUSION

Our creative integration of bulk RNA sequencing and scRNA-seq data allowed us to construct a DDR-related prognostic model. Our model can be used to predict the immunological features, treatment response and prognosis of PDAC with a relatively high degree of accuracy.

Silencing LY6D Expression Inhibits Colon Cancer in Xenograft Mice and Regulates Colon Cancer Stem Cells' Proliferation, Stemness, Invasion, and Apoptosis via the MAPK Pathway

This study explored the role of lymphocyte antigen 6 family member D (LY6D) in colon cancer stem cells' (CCSCs) proliferation and invasion. LY6D was knocked down using siRNA, and the down-regulation of LY6D was verified using Western blotting. After LY6D knockdown, CCSCs' proliferation, stemness, and invasion were suppressed, whereas apoptosis was increased. Gene Ontology (GO) enrichment analysis revealed that the differentially expressed genes (DEGs) between siLY6D and the negative control groups were significantly enriched in the cell-substrate adherens junction, focal adhesion, and cell-substrate junction terms. Meanwhile, the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that the DEGs were significantly enriched in the MAPK pathway. In addition, Western blotting results showed that pBRAF and pERK1/2, cascade kinases of the MAPK pathway, were significantly down-regulated after LY6D knockdown. In addition, nude mice xenograft experiments showed that the siLY6D treatment decreased tumor sizes and weights and improved tumor-bearing mice survival rates compared with the control group. In conclusion, these findings indicate that LY6D, which is highly expressed in CCSCs, is a key factor involved in tumor growth and development and might be a potential cancer marker and therapeutic target for colon cancer.

Ly-6A-Induced Growth Inhibition and Cell Death in a Transformed CD4+ T Cell Line: Role of Tumor Necrosis Factor-α

Ly-6A, a member of the Ly-6/uPAR supergene family of proteins, is a cell adhesion and cell signaling protein. Signaling through Ly-6A activates the cell-intrinsic apoptotic cell death pathway in CD4⁺ T cell lines, as indicated by the release of cytochrome C, and activation of caspases 9 and 3. In addition, Ly-6A induces cytokine production and growth inhibition. The mechanism underlying the distinct cellular responses that are triggered by engaging Ly-6A protein has remained unknown. To examine the relatedness of these distinct responses, we have quantified the production of pro-apoptotic, growth inhibitory and tumor suppressive cytokines, such as TNF-α, TGF-β and a related protein GDF-10, in response to Ly-6A signaling. Anti-Ly-6A monoclonal antibody-induced activation of YH16.33 CD4⁺ T cell line generated low levels of TGF-β and GDF-10 but elevated levels of TNF-α. Blocking the biological activity of TNF-α resulted in reduced Ly-6A-induced apoptosis in T cells. The Ly-6A-induced response in the T cell line was distinct, as signaling through the antigen receptor complex did not cause growth inhibition and apoptosis despite high levels of TGF-β and GDF-10 that were detected in these cultures. Additionally, in response to antigen receptor complex signaling, lower amount of TNF-α was detected. These results indicate the contribution of TNF-α in the observed Ly-6A-induced growth inhibition and apoptosis and provide a mechanistic explanation for the biologically distinct responses observed in CD4⁺ T cells after engaging Ly-6A protein. Additionally, the findings reported here will aid in the understanding of inhibitory signaling initiated by Ly-6A protein, especially in the context of its potential immune checkpoint inhibitory role in T cells.

Ly-6D of Japanese flounder (Paralichthys olivaceus) functions as a complement regulator and promotes host clearance of pathogen

The Lymphocyte antigen-6 (Ly-6) superfamily has been considered to play an important role in the innate immunity of mammals. The functions of Ly-6 proteins are diverse since their low sequence homology. Currently, the function of Ly-6D, a member of Ly-6 family proteins, is completely unknown in teleost. In the present study, we identified and characterized a Ly-6D homologue (named PoLy-6D) from the teleost fish Paralichthys olivaceus and examined its immune function. PoLy-6D possesses a hydrophobic signal peptide, a LU domain including a conserved "LXCXXC" motif in N-terminus and a "CCXXXXCN" motif in C-terminus. Under normal physiological condition, PoLy-6D expression distributes in all the examined tissues, the highest three tissues are successively spleen, head kidney, and blood. When infected by extracellular and intracellular bacterial pathogens and viral pathogen, PoLy-6D expression was induced and the patterns vary with different types of microbial pathogens infection and different immune tissues. In vitro experiment showed recombinant PoLy-6D (rPoLy-6D) inhibited the lysis of rabbit red blood cells by serum and selectively improved bacterial survival in serum. After serum were treated by antibody of rPoLy-6D, bacteriostatic effect of serum was obviously enhanced. These results indicate the importance of PoLy-6D as a complement regulator. rPoLy-6D possessed the binding activity to multiple bacteria but did not exhibit antimicrobial activities. The interaction between rPoLy-6D and bacteria suggests that PoLy-6D is involved in host clearance of pathogens probably by serving as a receptor for pathogens. Overexpression of PoLy-6D in vivo promoted the host defense against invading E. piscicida. These findings add new insights into the regulation mechanism of the complement system in teleost and emphasize the importance of Ly-6D products for the control of pathogen infection.

AP-1 and TGFß cooperativity drives non-canonical Hedgehog signaling in resistant basal cell carcinoma

Tumor heterogeneity and lack of knowledge about resistant cell states remain a barrier to targeted cancer therapies. Basal cell carcinomas (BCCs) depend on Hedgehog (Hh)/Gli signaling, but can develop mechanisms of Smoothened (SMO) inhibitor resistance. We previously identified a nuclear myocardin-related transcription factor (nMRTF) resistance pathway that amplifies noncanonical Gli1 activity, but characteristics and drivers of the nMRTF cell state remain unknown. Here, we use single cell RNA-sequencing of patient tumors to identify three prognostic surface markers (LYPD3, TACSTD2, and LY6D) which correlate with nMRTF and resistance to SMO inhibitors. The nMRTF cell state resembles transit-amplifying cells of the hair follicle matrix, with AP-1 and TGFß cooperativity driving nMRTF activation. JNK/AP-1 signaling commissions chromatin accessibility and Smad3 DNA binding leading to a transcriptional program of RhoGEFs that facilitate nMRTF activity. Importantly, small molecule AP-1 inhibitors selectively target LYPD3+/TACSTD2+/LY6D+ nMRTF human BCCs ex vivo, opening an avenue for improving combinatorial therapies.

Emerging Role of Novel Biomarkers of Ly6 Gene Family in Pan Cancer

Stem cell antigen-1 (Sca-1) is the first identified member of mouse Ly6 gene family. We discovered that Sca-1 disrupts TGFβ signaling and enhances mammary tumorigenesis in a DMBA-induced mammary tumor model. Sca-1 gene is lost during evolution in humans. Human Ly6 genes Ly6D, LyE, LyH, and LyK on human chromosome 8q24.3 genes are syntenic to the mouse chromosome 15 where Sca-1 is located. We found that Ly6D, E, H, and K are upregulated in human cancer compared to normal tissue and that the increased expression of these genes are associated with poor prognosis of multiple types of human cancer. Several other groups have indicated increased expression of Ly6 genes in human cancer. Here we described the relevance of expression of human Ly6D, LyE, LyH, and LyK in functioning of normal tissues and tumor progression.

Single-Cell Analysis Identifies LY6D as a Marker Linking Castration-Resistant Prostate Luminal Cells to Prostate Progenitors and Cancer

The exact identity of castrate-resistant (CR) cells and their relation to CR prostate cancer (CRPC) is unresolved. We use single-cell gene profiling to analyze the molecular heterogeneity in basal and luminal compartments. Within the luminal compartment, we identify a subset of cells intrinsically resistant to castration with a bi-lineage gene expression pattern. We discover LY6D as a marker of CR prostate progenitors with multipotent differentiation and enriched organoid-forming capacity. Lineage tracing further reveals that LY6D+ CR luminal cells can produce LY6D- luminal cells. In contrast, in luminal cells lacking PTEN, LY6D+ cells predominantly give rise to LY6D+ tumor cells, contributing to high-grade PIN lesions. Gene expression analyses in patients' biopsies indicate that LY6D expression correlates with early disease progression, including progression to CRPC. Our studies thus identify a subpopulation of luminal progenitors characterized by LY6D expression and intrinsic castration resistance. LY6D may serve as a prognostic maker for advanced prostate cancer.

Lipoprotein lipase transporter GPIHBP1 and triglyceride-rich lipoprotein metabolism

Increased plasma triglyceride serves as an independent risk factor for cardiovascular disease (CVD). Lipoprotein lipase (LPL), which hydrolyzes circulating triglyceride, plays a crucial role in normal lipid metabolism and energy balance. Hypertriglyceridemia is possibly caused by gene mutations resulting in LPL dysfunction. There are many factors that both positively and negatively interact with LPL thereby impacting TG lipolysis. Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1), a newly identified factor, appears essential for transporting LPL to the luminal side of the blood vessel and offering a platform for TG hydrolysis. Numerous lines of evidence indicate that GPIHBP1 exerts distinct functions and plays diverse roles in human triglyceride-rich lipoprotein (TRL) metabolism. In this review, we discuss the GPIHBP1 gene, protein, its expression and function and subsequently focus on its regulation and provide critical evidence supporting its role in TRL metabolism. Underlying mechanisms of action are highlighted, additional studies discussed and potential therapeutic targets reviewed.

miRNAs involved in LY6K and estrogen receptor α contribute to tamoxifen-susceptibility in breast cancer

Estrogen receptor-alpha (ERα) is a clinically important therapeutic target for breast cancer. However, tumors that lose ERα are less responsive to anti-estrogens such as tamoxifen. MicroRNAs (miRNAs) are small RNAs that regulate expression of their target gene and dysregulations of miRNA has been identified in many diseases including human cancer. However, only a few miRNAs associated with tamoxifen resistance has been reported. In this study, we found that lymphocyte antigen 6 complex (LY6K), which is a member of the Ly-6/μPAR superfamily and related to breast cancer progression and metastasis, is inversely correlated with ERα expression. We, for the first time, found miRNAs involved in the regulatory molecular mechanism between ERα and LY6K and related to tamoxifen susceptibility in breast cancer. miR-192-5p, induced by LY6K, downregulates ERα directly and induced tamoxifen resistance in ERα-positive breast cancer cells. In addition, re-expression of ERα in ERα-negative breast cancer cells increased miR-500a-3p expression and directly inhibits LY6K expression. Ectopic expression of miR-500a-3p sensitized ERα-negative cells to tamoxifen by increasing apoptosis. Finally, we observed an inverse correlation between LY6K and ERα in primary breast cancer samples. We found that patients with recurrence showed high expression of miR-192-5p after tamoxifen treatments. In addition, expression of miR-500a-3p was significantly correlated to survival outcome. As miRNAs involved in the regulatory mechanism between LY6K and ERα can affect tamoxifen resistance, downregulating miR-192-5p or re-expressing miR-500a-3p could be a potential therapeutic approach for treating tamoxifen resistant patients.

Involvement of Lypge in the formation of eye and pineal gland in zebrafish

The proteins of Ly-6 (lymphocyte antigen-6) family are involved in the regulation of immunoreaction, cell migration and adhesion, and neuronal excitability. However, little is known about the function of Ly-6 proteins in embryogenesis. Herein, we identified a GPI anchored Ly-6 member named ly6 expressed in pineal gland and eye (lypge). Dynamic expression pattern of lypge was revealed by whole mount in situ hybridization. It was strikingly expressed in the pineal gland and cone photoreceptor, and its expression was regulated by orthodenticle homolog 5 (otx5) which has been shown to control the expression of many pineal genes. In addition, we demonstrated that lypge was rhythmically expressed in larvae from 4dpf on. Moreover, knockdown of lypge resulted in small head and small eye formed in zebrafish embryos. These suggest that Lypge is involved in the formation of the eye and pineal gland in early development of zebrafish.

Engaging Ly-6A/Sca-1 triggers lipid raft-dependent and -independent responses in CD4+ T-cell lines

INTRODUCTION

The lymphocyte antigen 6 (Ly-6) supergene family encodes proteins of 12-14 kda in molecular mass that are either secreted or anchored to the plasma membrane through a glycosyl-phosphatidylinisotol (GPI) lipid anchor at the carboxy-terminus. The lipidated GPI-anchor allows localization of Ly-6 proteins to the 10-100 nm cholesterol-rich nano-domains on the membrane, also known as lipid rafts. Ly-6A/Sca-1, a member of Ly-6 gene family is known to transduce signals despite the absence of transmembrane and cytoplasmic domains. It is hypothesized that the localization of Ly-6A/Sca-1 with in lipid rafts allows this protein to transduce signals to the cell interior.

METHODS AND RESULTS

In this study, we found that cross-linking mouse Ly-6A/Sca-1 protein with a monoclonal antibody results in functionally distinct responses that occur simultaneously. Ly-6A/Sca-1 triggered a cell stimulatory response as gauged by cytokine production with a concurrent inhibitory response as indicated by growth inhibition and apoptosis. While production of interleukin 2 (IL-2) cytokine by CD4⁺ T cell line in response to cross-linking Ly-6A/Sca-1 was dependent on the integrity of lipid rafts, the observed cell death occurred independently of it. Growth inhibited CD4⁺ T cells showed up-regulated expression of the inhibitory cell cycle protein p27^kip but not of p53. In addition, Ly-6A/Sca-1 induced translocation of cytochrome C to the cytoplasm along with activated caspase 3 and caspase 9, thereby suggesting an intrinsic apoptotic cell death mechanism.

CONCLUSIONS

We conclude that opposing responses with differential dependence on the integrity of lipid rafts are triggered by engaging Ly-6A/Sca-1 protein on the membrane of transformed CD4⁺ T cells.

Coexpression Analysis of Transcriptome on AIDS and Other Human Disease Pathways by Canonical Correlation Analysis

Acquired immune deficiency syndrome is a severe disease in humans caused by human immunodeficiency virus. Several human genes were characterized as host genetic factors that impact the processes of AIDS disease. Recent studies on AIDS patients revealed a series disease is complicating with AIDS. To resolve gene interaction between AIDS and complicating diseases, a canonical correlation analysis was used to identify the global correlation between AIDS and other disease pathway genes expression. The results showed that HLA-B, HLA-A, MH9, ZNED1, IRF1, TLR8, TSG101, NCOR2, and GML are the key AIDS-restricted genes highly correlated with other disease pathway genes. Furthermore, pathway genes in several diseases such as asthma, autoimmune thyroid disease, and malaria were globally correlated with ARGs. It suggests that these diseases are a high risk in AIDS patients as complicating diseases.

Identification of Ly2 members as antimicrobial peptides from zebrafish Danio rerio

The emergence of multidrug-resistant (MDR) microbes caused by overuse of antibiotics leads to urgent demands for novel antibiotics exploration. Our recent data showed that Ly2.1–3 (a novel lymphocyte antigen 6 (Ly6) gene cluster) were proteins with cationic nature and rich in cysteine content, that are characteristic of antimicrobial peptides (AMPs) and their expression were all significantly up-regulated after challenge with lipopolysaccharide (LPS). These strongly suggested that Ly2.1–3 are potential AMPs, but firm evidence are lacking. Here, we clearly showed that the recombinant proteins of Ly2.1–3 were capable of killing Gram-negative bacteria Aeromonas hydrophila and Escherichia coli, while they had little bactericidal activity against the Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis. We also showed that recombinant proteins Ly2.1–3 (rLy2.1–3) were able to bind to the Gram-negative bacteria A. hydrophila, E. coli and the microbial signature molecule LPS, but not to the Gram-positive bacteria S. aureus and B. subtilis as well as the microbial signature molecule LTA. Moreover, the Scatchard analysis revealed that rLy2.1–3 could specifically bind to LPS. Finally, we found that Ly2.1–3 were not cytotoxic to mammalian cells. All these together indicate that Ly2.1–3 can function as AMPs.

A Canonical Correlation Analysis of AIDS Restriction Genes and Metabolic Pathways Identifies Purine Metabolism as a Key Cooperator

Human immunodeficiency virus causes a severe disease in humans, referred to as immune deficiency syndrome. Studies on the interaction between host genetic factors and the virus have revealed dozens of genes that impact diverse processes in the AIDS disease. To resolve more genetic factors related to AIDS, a canonical correlation analysis was used to determine the correlation between AIDS restriction and metabolic pathway gene expression. The results show that HIV-1 postentry cellular viral cofactors from AIDS restriction genes are coexpressed in human transcriptome microarray datasets. Further, the purine metabolism pathway comprises novel host factors that are coexpressed with AIDS restriction genes. Using a canonical correlation analysis for expression is a reliable approach to exploring the mechanism underlying AIDS.

Identification and expression of a new Ly6 gene cluster in zebrafish Danio rerio, with implications of being involved in embryonic immunity

Lymphocyte antigen-6 (Ly6) superfamily is a large family of proteins and characterized by precisely spaced cysteine motifs, termed the three-finger fold. To date, a large number of members of the Ly6/uPAR family were identified among many species. In this study, we first report the identification and characterization of the secreted Ly2.1-3 proteins on the chromosome 2 in zebrafish and determine the expression pattern. Ly2.1-3 all possess a conserved LU domain and adopt similar three-finger structure with human CD59, SLURP1 and other Ly6 family members. Ly2.1-3 cluster on chromosome 2 and share high homology, possibly originated from chromosomal gene duplication. Ly2.1-3 exhibit distinct expression pattern in the endoderm, they were found abundantly and specifically in the digestive tract, liver and pancreas respectively. The differential expression pattern may suggest Ly2.1-3 acquire new function during gene duplication. The expression level of Ly2.1-3 were up-regulating challenged with LPS indicated that they have a role in innate immune responses of the digestive system during endotoxin challenge in early stage.

Organization, evolution and functions of the human and mouse Ly6/uPAR family genes

Members of the lymphocyte antigen-6 (Ly6)/urokinase-type plasminogen activator receptor (uPAR) superfamily of proteins are cysteine-rich proteins characterized by a distinct disulfide bridge pattern that creates the three-finger Ly6/uPAR (LU) domain. Although the Ly6/uPAR family proteins share a common structure, their expression patterns and functions vary. To date, 35 human and 61 mouse Ly6/uPAR family members have been identified. Based on their subcellular localization, these proteins are further classified as GPI-anchored on the cell membrane, or secreted. The genes encoding Ly6/uPAR family proteins are conserved across different species and are clustered in syntenic regions on human chromosomes 8, 19, 6 and 11, and mouse Chromosomes 15, 7, 17, and 9, respectively. Here, we review the human and mouse Ly6/uPAR family gene and protein structure and genomic organization, expression, functions, and evolution, and introduce new names for novel family members.

Identification and expression of an uncharacterized Ly-6 gene cluster in zebrafish Danio rerio

The Ly-6/uPAR/CD59/neurotoxin superfamily (Ly-6SF) identified in most metazoan has been shown to play important roles in different biological processes including immunity, cellular adhesion, and cell signaling. Members of this superfamily contain one or more conserved domains known as Ly-6/uPAR (LU) domain, which harbors 8 or 10 conserved cysteine residues forming 4-5 disulfide bonds. In this study, we reported the identification of a novel zebrafish Ly-6 gene cluster on chromosome 21, which consists of seven genes ly21.1, ly21.2, ly21.3, ly21.4, ly21.5, ly21.6, and ly21.7 and their spatiotemporal expression pattern during development. All the seven genes possess features typical of the Ly-6/neurotoxin superfamily, and phylogenetic analysis shows that these genes form a single cluster branching form other members of Ly-6 family, suggesting that the seven genes evolved by an event of intra-chromosome gene duplication. However, deduced Ly21.1-7 proteins share little homology with Ly-6 family proteins from other species, no orthologs are identified in vertebrates, including teleosts, hinting that ly21.1-7 genes are evolutionarily a novel addition to zebrafish. Expression analyses show that maternal mRNAs of ly21.1-7 genes are detected during early developmental stages, but later in development, they exhibit tissue-specific expression. Except for ly21.2 which is expressed in the skin ionocytes, all the remaining six genes are mainly expressed in the developing brain.

Identification of a Ly-6 superfamily gene expressed in lateral line neuromasts in zebrafish

Lymphocyte antigen-6 (Ly-6) superfamily members have been identified in zebrafish, but the expression and function of these Ly-6 genes remain largely unknown. Posterior lateral line (pLL) system is produced by migrating pLL primordium (pLLp). Chemokine signaling, Notch, Wnt, and fibroblast growth factor (FGF) signaling regulate migration of pLLp cells and formation of neuromasts. However, the mechanism of neuromast deposition remains to be explored. Identification of novel genes expressed in pLLp will certainly help the study of such a process. Here we identified a Ly-6 gene called neuromast-expressed gpi-anchored lymphocyte antigen-6 (negaly6), which was specifically expressed in neuromast. Quantitative real-time PCR (qRT-PCR) analysis showed that negaly6 started to be expressed at 24 hpf, and whole-mount in situ hybridization analysis indicated that negaly6 was highly expressed in the trailing zone of pLLp and mature neuromast. Furthermore, negaly6 expression was inhibited by FGF signaling antagonist but not by Wnt signaling agonist or antagonist. Collectively, these data indicate that negaly6 may be associated with the regulation of neuromast deposition via FGF signaling pathway.

Acute lymphoid leukemia cells with greater stem cell antigen-1 (Ly6a/Sca-1) expression exhibit higher levels of metalloproteinase activity and are more aggressive in vivo

Stem cell antigen-1 (Ly6a/Sca-1) is a gene that is expressed in activated lymphocytes, hematopoietic stem cells and stem cells of a variety of tissues in mice. Despite decades of study its functions remain poorly defined. These studies explored the impact of expression of this stem cell associated gene in acute lymphoid leukemia. Higher levels of Ly6a/Sca-1 expression led to more aggressive leukemia growth in vivo and earlier death of hosts. Leukemias expressing higher levels of Ly6a/Sca-1 exhibited higher levels of matrix metalloproteinases. The results suggest the hypothesis that the more aggressive behavior of Ly6a/Sca-1 expressing leukemias is due at least in part to greater capacity to degrade microenvironmental stroma and invade tissues.

Palmoplantar keratoderma along with neuromuscular and metabolic phenotypes in Slurp1-deficient mice

Mutations in SLURP1 cause mal de Meleda, a rare palmoplantar keratoderma (PPK). SLURP1 is a secreted protein that is expressed highly in keratinocytes but has also been identified elsewhere (e.g., spinal cord neurons). Here, we examined Slurp1-deficient mice (Slurp1^−/−) created by replacing exon 2 with β-gal and neo cassettes. Slurp1^−/− mice developed severe PPK characterized by increased keratinocyte proliferation, an accumulation of lipid droplets in the stratum corneum, and a water barrier defect. In addition, Slurp1^−/− mice exhibited reduced adiposity, protection from obesity on a high-fat diet, low plasma lipid levels, and a neuromuscular abnormality (hind limb clasping). Initially, it was unclear whether the metabolic and neuromuscular phenotypes were due to Slurp1 deficiency because we found that the targeted Slurp1 mutation reduced the expression of several neighboring genes (e.g., Slurp2, Lypd2). We therefore created a new line of knockout mice (Slurp1X^−/− mice) with a simple nonsense mutation in exon 2. The Slurp1X mutation did not reduce the expression of adjacent genes, but Slurp1X^−/− mice exhibited all of the phenotypes observed in the original line of knockout mice. Thus, Slurp1 deficiency in mice elicits metabolic and neuromuscular abnormalities in addition to PPK.

Optimizing cholinergic tone through lynx modulators of nicotinic receptors: implications for plasticity and nicotine addiction

The cholinergic system underlies both adaptive (learning and memory) and nonadaptive (addiction and dependency) behavioral changes through its ability to shape and regulate plasticity. Protein modulators such as lynx family members can fine tune the activity of the cholinergic system and contribute to the graded response of the cholinergic system, stabilizing neural circuitry through direct interaction with nicotinic receptors. Release of this molecular brake can unmask cholinergic-dependent mechanisms in the brain. Lynx proteins have the potential to provide top-down control over plasticity mechanisms, including addictive propensity. If this is indeed the case, then, what regulates the regulator? Transcriptional changes of lynx genes in response to pharmacological, physiological, and pathological alterations are explored in this review.

Expression of LY6D is induced at the surface of MCF10A cells by X-ray irradiation

In order to identify membrane proteins whose expression is induced by X-ray irradiation, we developed an antibody (Ab)-directed strategy using a phage Ab library. X-Ray-irradiated cells were screened with a phage Ab library in the presence of a large excess of polyclonal Abs prepared against membrane proteins that are commonly present at the surface of both X-ray-irradiated and nonirradiated cells. After isolation of Ab that bound only to X-ray-irradiated cells, the antigen was identified using MS. Using this approach, we found that expression of LY6D is induced in MCF10A cells by X-ray irradiation. The induction of LY6D expression is triggered through a pathway regulated by ATM, CHK2 and p53. This method is a new Ab-directed proteomic strategy for analysis of membrane proteins, and is applicable to various biological phenomena in situations in which both target molecule-expressing cells and nonexpressing cells are available.

Low expression of stem cell antigen-1 on mouse haematopoietic precursors is associated with erythroid differentiation

Sca1 is a surface marker of haematopoietic stem cell but its role in erythropoiesis is still largely unknown. In this work we evaluated the ability of Sca1⁺ cells to differentiate into cells of the erythrocytic lineage. We performed FACS analysis of complete and purified Sca1⁺ bone marrow cells from C3H/HeNHsd mice and measured the expression of CD71 and Terr119 to evaluate the stages in erythroid development. Definitive erythropoiesis was evident within the complete bone marrow, while only proerythroblasts were found in Sca1⁺ cells, suggesting that Sca1 is a negative regulator of erythropoiesis. We also used FDCP-mix cells and their PU.1 and SCL transfectants. The PU.1 transfectant showed significantly increased expression of Sca1 and was not induced to differentiate into red blood cells, while the SCL transfectant showed significantly lower expression of Sca1 and produced red blood cells. The results of this study suggest that increased Sca1 expression on erythropoietic precursors inhibits erythroid differentiation.

The regulatory mechanism of the LY6K gene expression in human breast cancer cells

LY6K is a cancer biomarker and a therapeutic target that induces invasion and metastasis. However, the molecular mechanisms that determine human LY6K transcription are completely unknown. To elucidate the mechanisms involved in human LY6K gene regulation and expression, multiple cis-elements were predicted using TRANSFAC software, and the LY6K regulatory region was identified using the luciferase assay in the human LY6K gene promoter. We performed ChIP, EMSA, and supershift assays to investigate the transcription factor activity on the LY6K promoter, and the effect of a SNP and CpG site methylation on AP-1 transcription factor binding affinity. AP-1 and the CREB transcription factor bound to LY6K promoter within -550/-1, which was essential for LY6K expression, but only the AP-1 heterodimer, JunD, and Fra-1, modulates LY6K gene transcriptional level. A decrease in LY6K was associated with the SNP242 C allele, a polymorphic G/C-SNP at the 242 nucleotide in the LY6K promoter region (rs2585175), or methylation of the CpG site, which was closely located with the AP-1 site by interfering with binding of the AP-1 transcription factor to the LY6K promoter. Our findings reveal an important role for AP-1 activation in promoting LY6K gene expression that regulates cell mobility of breast cancer cells, whereas the SNP242 C allele or methylation of the CpG site may reduce the risk of invasion or metastasis by interfering AP-1 activation.

Molecular diagnosis of minimal residual disease in head and neck cancer patients

AIM

Locoregional recurrences and distant metastases in adequately treated head and neck squamous cell carcinoma (HNSCC) patients have a dismal effect on survival. Tumor cells that escape histopathological detection might be the prime cause of this effect. We evaluated whether minimal residual cancer (MRC) in deep surgical margins and disseminated tumor cells (DTCs) in bone marrow aspirates are associated with clinicohistopathological parameters and outcome.

METHODS

Submucosal samples of deep resection margins of 105 HNSCC patients with histopathologically tumor-free surgical margins were analysed for the presence of MRC using hLy-6D qRT-PCR. Bone-marrow aspirates of 76 of these patients were analysed for DTCs by immunocytochemical staining. Presence of molecular-positive deep surgical margins, presence of DTC in bone marrow aspirates, and clinicohistopathological parameters were tested for associations with survival parameters by univariate and multivariate analyses.

RESULTS

In addition to lymph node stage, it appeared that vasoinvasive growth and particularly infiltrative growth pattern are significant predictors for locoregional recurrence (p = 0.041 and p = 0.006, respectively) and disease-free survival (p = 0.014 and p = 0.008, respectively). Remarkably, neither the presence of molecular-positive deep surgical margins nor that of DTC in bone marrow aspirates were significantly related to outcome.

CONCLUSIONS

The presence of vasoinvasive and infiltrative growth in HNSCC tumor specimens are significant risk-factors for locoregional recurrence and disease-free survival. At present there seems no role for molecular analysis of deep surgical margins and bone marrow aspirates in predicting outcome with the methods used.

Identification and expression of a novel member of Ly-6 superfamily in zebrafish Denio rerio

Ly-6 superfamily members are present in many metazoans and are divided into two groups: secreted proteins and glycosylphosphatidyl inositol (GPI)-anchored membrane proteins. They both contain one or more conserved domain identified as Ly-6/uPAR (LU) domain and play key roles in cellular adhesion and signaling. Here, we identify a novel member, lymphocyte antigen-6 epidermis (lye), of Ly-6 superfamily in zebrafish. In silico analyses revealed that lye codes for a predicted GPI-anchored membrane protein containing a conserved LU domain and 10 position-specific conserved cysteines typical of known Ly-6 proteins. Whole mount in situ hybridization showed that lye is predominantly expressed in epidermis. We thus named the gene lye, highlighting it is expressed in epidermis. Lye exhibits a dynamic expression pattern during development, which is initially expressed in enveloping layer at gastrula stage, then expressed in epidermis at later stages. It is also expressed in olfactory placode at 24 h post-fertilization. Subsequently, epidermal expression of lye becomes weaker gradually, whereas the expression in pharyngeal arch and pectoral fin increases at 2 and 3 days post-fertilization. Our study lays a foundation for further investigation of lye roles in early developmental stages.

Comparative studies of glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1: evidence for a eutherian mammalian origin for the GPIHBP1 gene from an LY6-like gene

Glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) functions as a platform and transport agent for lipoprotein lipase (LPL) which functions in the hydrolysis of chylomicrons, principally in heart, skeletal muscle and adipose tissue capillary endothelial cells. Previous reports of genetic deficiency for this protein have described severe chylomicronemia. Comparative GPIHBP1 amino acid sequences and structures and GPIHBP1 gene locations were examined using data from several mammalian genome projects. Mammalian GPIHBP1 genes usually contain four coding exons on the positive strand. Mammalian GPIHBP1 sequences shared 41–96% identities as compared with 9–32% sequence identities with other LY6-domain-containing human proteins (LY6-like). The human N-glycosylation site was predominantly conserved among other mammalian GPIHBP1 proteins except cow, dog and pig. Sequence alignments, key amino acid residues and conserved predicted secondary structures were also examined, including the N-terminal signal peptide, the acidic amino acid sequence region which binds LPL, the glycosylphosphatidylinositol linkage group, the Ly6 domain and the C-terminal α-helix. Comparative and phylogenetic studies of mammalian GPIHBP1 suggested that it originated in eutherian mammals from a gene duplication event of an ancestral LY6-like gene and subsequent integration of exon 2, which may have been derived from BCL11A (B-cell CLL/lymphoma 11A gene) encoding an extended acidic amino acid sequence.

The CD59 family member Leaky/Coiled is required for the establishment of the blood-brain barrier in Drosophila

The blood-brain barrier of Drosophila is established by the subperineurial glial cells that encase the CNS and PNS. The subperineurial glial cells are thin, highly interdigitated cells with epithelial character. The establishment of extensive septate junctions between these cells is crucial for the prevention of uncontrolled paracellular leakage of ions and solutes from the hemolymph into the nervous system. In the absence of septate junctions, macromolecules such as fluorescently labeled dextran can easily cross the blood-brain barrier. To identify additional components of the blood-brain barrier, we followed a genetic approach and injected Texas-Red-conjugated dextran into the hemolymph of embryos homozygous for chromosomal deficiencies. In this way, we identified the 153-aa-large protein Coiled, a new member of the Ly6 (leukocyte antigen 6) family, as being crucially required for septate junction formation and blood-brain barrier integrity. In coiled mutants, the normal distribution of septate junction markers such as NeurexinIV, Coracle, or Discs large is disturbed. EM analyses demonstrated that Coiled is required for the formation of septate junctions. We further show that Coiled is expressed by the subsperineurial glial cells in which it is anchored to the cell membrane via a glycosylphosphatidylinositol anchor and mediates adhesive properties. Clonal rescue studies indicate that the presence of Coiled is required symmetrically on both cells engaged in septate junction formation.

Adenovirus retargeting to surface expressed antigens on oral mucosa

BACKGROUND

Head and neck squamous cell carcinomas develop in preneoplastic mucosal fields that can extend over several centimeters in diameter. Most of these fields are microscopically recognized as dysplasias. These fields are often not adequately treated and might cause local relapse. Previous investigations demonstrated that mouthwash therapy with oncolytic adenoviruses appears to be a good option for the treatment of these fields, although, at present, with limited efficacy.

METHODS

Immunohistochemistry on normal and preneoplastic mucosa was applied to determine the expression levels of the coxsackie adenoviral receptor (CAR) and a few surface antigens that might allow retargeting: Ly-6D, CD44v6 and K928. Monoclonal antibodies directed against these surface antigens were used for retargeting of adenoviruses in model experiments with organotypic cultures of mucosal epithelium. A bispecific single chain antibody was constructed against both the adenoviral knob and Ly-6D.

RESULTS

Immunohistochemical staining revealed that CAR is present only at a low level in the basal layers of the oral mucosa of both normal and dysplastic lesions. By contrast, Ly-6D, CD44v6 and K928 were abundantly expressed and Ly-6D even on the most superficial layers. Monoclonal antibodies against Ly-6D and CD44v6 were shown to enhance infection in an organotypic cell culture by one log. Based on these observations, we constructed a bispecific single chain antibody against Ly-6D and adenovirus fiber knob, and showed that this engineered molecule allows efficient CAR-independent infection.

CONCLUSIONS

Retargeting of oncolytic adenovirus to other surface molecules might improve the efficacy of virotherapy of preneoplastic fields in the oral mucosa.

Targeted radionuclide therapy in head and neck cancer

There is great potential for targeted radionuclide therapy (TRT) in the treatment of head and neck cancer. In recent years, developments in fields such as antigen screening, protein engineering, and cancer biology have facilitated the rational design of targeted pharmaceuticals, with monoclonal antibodies forming the most rapidly expanding category. TRT may be a promising way to improve targeted treatment, especially in head and neck cancer, because of the intrinsic radiosensitivity of this tumor type. TRT may also provide a good foundation on which to build rational biologic combination therapies. In the next few years the use of TRT may offer new opportunities for further improvement of the therapeutic ratio that potentially may obviate or reduce the need for conventional cytotoxics.

Association and haplotype analysis of prostate stem cell antigen with gastric cancer in Tibetans

Genetic factors are known to be important in the development of gastric cancer (GC). Prostate stem cell antigen (PSCA) has been shown to be expressed in diffuse-type GC, and PSCA variation is associated with susceptibility to diffuse-type GC in Japanese and Korean populations. The aim of this study was to investigate the association between PSCA gene polymorphisms and GC in a Tibetan population. We analyzed single-nucleotide polymorphisms of the PSCA gene in 196 patients with GC and 246 controls in a Tibetan population, using a polymerase chain reaction/ligase detection reaction test. The rs2294008 C/T polymorphism of the PSCA gene was significantly associated with the susceptibility to GC. The CT genotype was associated with a significantly higher risk of GC when compared with the CC genotype (odds ratio [OR] = 1.50; 95% confidence interval [CI], 1.01-2.23). Patients carrying the T allele had a significantly higher risk for developing GC compared with individuals carrying the C allele (OR = 1.34; 95% CI, 1.00-1.79). Haplotype analyses showed that CA haplotype was associated with a significantly decreased risk of GC when compared with the CG haplotype (OR = 0.47; 95% CI, 0.24-0.93). Our data indicate that PSCA gene polymorphisms may be associated with GC in Tibetans.

Immunohistochemical Expression of Prostate Stem Cell Antigen in Cystoprostatectomies with Incidental Prostate Cancer

High expression of Prostate Stem Cell Antigen (PSCA) has been shown to be associated with adverse prognostic features in clinically-diagnosed prostate cancer. The aim of this study is to analyze PSCA expression in cystoprostatectomies with incidental prostate carcinoma (PCa). PSCA expression was evaluated immunohistochemically in normal-looking epithelium (NEp), high-grade prostatic intraepithelial neoplasia (HGPIN) and pT2a Gleason score 6 acinar adenocarcinoma. The evaluation was carried out on 20 cystoprostatectomies (CyPs) with incidental PCa from men with bladder urothelial carcinoma (UC), and 20 radical prostatectomies (RPs) with hormonally untreated PCa from men with clinically detected PCa. Ki-67 was also investigated. The percentages of PSCA positive cells in HGPIN were significantly higher than in NEp (NEp: CyP, mean 2.92% ± standard deviation 6.26%; RP, 3.5% ± 6.46%. HGPIN: CyP, 13.67% ± 12.78%; RP, 14.67% ± 11.34%) (p<0.001). The proportions of positive cells in PCa were greater than in HGPIN (CyP, 20.25% ± 15.96%; RP, 22.58% ± 13.67%) (p0.001). For Ki-67 labeling, the proportions of positive nuclei in the CyPs significantly increased from NEp through HGPIN to PCa. A similar trend was seen in the RPs. In the CyPs the percentages of PSCA and Ki67 positive cells were lower than in the RPs, the differences between the CyP and RP compartments being not statistically significant. Our findings suggest that PSCA is a marker associated with neoplastic transformation of prostate cells, both in CyPs and RPs. However, there are no significant differences between CyPs with incidental prostate carcinoma and RPs with clinically diagnosed cancer.

Characterization and expression analysis of SOLD1, a novel member of the retrotransposon-derived Ly-6 superfamily, in bovine placental villi

Background

Ly-6 superfamily members have a conserved Ly-6 domain that is defined by a distinct disulfide bonding pattern between eight or ten cysteine residues. These members are divided into membrane-type and secretory-type proteins. In the present study, we report the identification of a novel Ly-6 domain protein, secreted protein of Ly-6 domain 1 (SOLD1), from bovine placenta.

Principal Findings

SOLD1 mRNA was expressed in trophoblast mononucleate cells and the protein was secreted into and localized in the extracellular matrix of the mesenchyme in cotyledonary villi. SOLD1 bound mainly with type I collagen telopeptide. We confirmed secretion of SOLD1 from the basolateral surface of a bovine trophoblast cell line (BT-1). It may be related to the organization of the extra-cellular matrix in the mesenchyme of fetal villi. Since trophoblast mononucleate cells are epithelial cells, their polar organization is expected to have a crucial role in the SOLD1 secretion system. We established that SOLD1 is an intronless bovine gene containing the Alu retrotransposon, which was integrated via cytoplasmic reverse transcription.

Conclusion

We identified a novel retrotransposon-like Ly-6 domain protein in bovine placenta. SOLD1 is a crucial secreted protein that is involved in the organization of the mesenchyme of the cotyledonary villi. Furthermore, the gene encoding SOLD1 has an interesting genomic structure.

Cloning and characterization of a human LYPD7, a new member of the Ly-6 superfamily

Members of the Ly-6 (Lymphocyte Antigen 6) protein family share one or several repeat units of the LU domain that is defined by a distinct disulfide bonding pattern between 8 or 10 cysteine residues. Here we report the cloning and characterization of a novel human LU domain-containing gene, LYPD7 (LY6/PLAUR domain containing 7), isolated from human testis cDNA library, and mapped to 2q22.3-23.3 by searching the UCSC genomic database. The LYPD7 cDNA sequence consists of 1,600 nucleotides and contains an open reading frame of 624 bp, encoding a putative protein of 207 amino acid residues. RT-PCR analysis showed that LYPD7 was especially highly expressed in testis, lung, stomach, and prostate. Subcellular localization of LYPD7 demonstrated that the protein was localized in the cytoplasm when overexpressed in Hela cells. Furthermore, the subsequent analysis based on reporter gene assays suggested that overexpression of LYPD7 in HEK 293T cells was able to activate the transcriptional activities of AP1 (PMA).

Gene expression profiling reveals unique pathways associated with differential severity of lyme arthritis

The murine model of Lyme disease provides a unique opportunity to study the localized host response to similar stimulus, Borrelia burgdorferi, in the joints of mice destined to develop severe arthritis (C3H) or mild disease (C57BL/6). Pathways associated with the response to infection and the development of Lyme arthritis were identified by global gene expression patterns using oligonucleotide microarrays. A robust induction of IFN-responsive genes was observed in severely arthritic C3H mice at 1 wk of infection, which was absent from mildly arthritic C57BL/6 mice. In contrast, infected C57BL/6 mice displayed a novel expression profile characterized by genes involved in epidermal differentiation and wound repair, which were decreased in the joints of C3H mice. These expression patterns were associated with disease state rather than inherent differences between C3H and C57BL/6 mice, because C57BL/6-IL-10(-/-) mice infected with B. burgdorferi develop more severe arthritis than C57BL/6 mice and displayed an early gene expression profile similar to C3H mice. Gene expression profiles at 2 and 4 wk postinfection revealed a common response of all strains that was likely to be important for the host defense to B. burgdorferi and mediated by NF-kappaB-dependent signaling. The gene expression profiles identified in this study add to the current understanding of the host response to B. burgdorferi and identify two novel pathways that may be involved in regulating the severity of Lyme arthritis.

Characterization of the five novel Ly-6 superfamily members encoded in the MHC, and detection of cells expressing their potential ligands

Lymphocyte Antigen 6 (Ly-6) superfamily members are cysteine-rich, generally GPI-anchored cell surface proteins, which have definite or putative immune related roles. There are 27 members of this family described so far in the human genome and 37 in the mouse. Five of them are clustered in the class III region of the human and mouse MHCs. Following computational analyses, we functionally characterized the encoded proteins by creating epitope-tagged fusion constructs to determine molecular weight, complex formation, subcellular localization, post-translational modifications and ligand binding. We found that all human and mouse proteins were glycosylated, and most could form part of larger complexes. Human and mouse Ly6G6c and Ly6G6d, and mouse Ly6g6e were found to be GPI-anchored cell surface proteins, highly expressed at the leading edges of cells, on filopodia, which are normally involved in cell adhesion and migration. However, analysis of Ly6G5c and Ly6G5b indicated that they are potentially secreted proteins. Our results indicate that there are two subclusters of related Ly-6 proteins in this region of the MHC, with Ly6G6c, Ly6G6d, and Ly6G6e forming one and Ly6G5c and Ly6G5b forming another. In addition, by FACS analysis we have found that the potential ligands for human LY6G6C, LY6G6D, and LY6G5C are expressed on K562 cells, an undifferentiated megakaryocyte cell line, indicating a potential role in hematopoietic cell differentiation. This characterization of the five MHC class III region Ly-6 family members is of great relevance, as they represent 18% of the human Ly-6 protein family and 50% of the secreted ones.

A phase I dose escalation study with anti-CD44v6 bivatuzumab mertansine in patients with incurable squamous cell carcinoma of the head and neck or esophagus

PURPOSE

To assess safety, pharmacokinetics, maximum tolerated dose, and preliminary efficacy of bivatuzumab mertansine. Bivatuzumab is a humanized monoclonal antibody directed against CD44v6, which previously seemed to be safe in phase I radioimmunotherapy trials, whereas the conjugated mertansine is a potent maytansine derivative.

EXPERIMENTAL DESIGN

Patients with incurable squamous cell carcinoma of the head and neck or esophagus were eligible. Bivatuzumab was given weekly for 3 consecutive weeks by i.v. infusion. One patient was planned to be treated at each dose tier as long as toxicity did not reach grade 2; otherwise, three patients had to be treated until dose-limiting toxicity occurred. Starting dose was 20 mg/m2 and dose was subsequently escalated in steps of 20 mg/m2. Patients without disease progression and not experiencing dose-limiting toxicity were eligible for repeated courses. Blood serum samples were taken throughout the treatment period to determine the pharmacokinetic properties of bivatuzumab mertansine and to assess the human anti-bivatuzumab mertansine antibody response.

RESULTS

Seven patients received a total of 23 weekly doses of bivatuzumab mertansine. One patient at the 100 mg/m2 and one at the 120 mg/m2 level experienced stable disease during treatment phase but also developed grade 1 skin toxicity (desquamation). One of them received a second treatment course. At the highest dose level achieved in this study (140 mg/m2), one patient developed toxic epidermal necrolysis after two infusions and died. Massive apoptosis of skin keratinocytes had occurred, whereas only symptomatic therapy for skin toxicity was available. The risk-benefit assessment of all patients treated in the total phase I program (4 clinical trials, 70 patients) turned out to be negative after consideration of this case of a toxic epidermal necrolysis and the skin-related adverse events observed in the other trials. Therefore, development of the conjugate was discontinued. Interindividual variability in pharmacokinetic variables was low and exposure to BIWI 1 increased proportionally with dose. No anti-bivatuzumab mertansine reactions were observed.

CONCLUSION

The main toxicity of bivatuzumab mertansine was directed against the skin, most probably due to CD44v6 expression in this tissue. The majority of skin reactions was reversible; however, one fatal drug-related adverse event had occurred. Clinical development was discontinued before reaching maximum tolerated dose.

The expression of prostate stem cell antigen in human clear cell renal cell carcinoma: a quantitative reverse transcriptase-polymerase chain reaction analysis

OBJECTIVES

To analyse the gene expression level of prostate stem cell antigen (PSCA) in human clear cell renal cell carcinoma (CC-RCC) and its relationship with conventional clinicopathological manifestations, to evaluate its prognostic value for patient outcome, and to determine the effect of PSCA on the progression of CC-RCC.

PATIENTS AND METHODS

We quantified PSCA mRNA level in human RCC cell lines (ACHN, A704, KPK-1, Caki-1, and Caki-2) and in 154 surgical tissue samples (81 from CC-RCC, 73 from normal kidney) using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). The findings were analysed in relation to clinicopathological factors. Immunohistochemical expression was examined using confocal laser scanning light-microscopy.

RESULTS

PSCA was overexpressed in all RCC cell lines. PSCA mRNA levels were significantly higher in CC-RCC than in normal kidney tissue samples (P < 0.001), in G2-G3 than in G1 tumours (P = 0.028), and in advanced disease (T3-T4) than in organ-confined (T1-T2) tumours (P = 0.016). There was significantly higher PSCA mRNA expression in patients with M1 than in those with M0 disease (P = 0.029). Patients in whom the lesions had high PSCA expression levels had a significantly worse prognosis than those with low PSCA expression levels (P = 0.044). Using immunohistochemical analysis there was markedly greater PSCA expression in CC-RCC than in normal kidney, and in advanced-disease high-grade tumours than in organ-confined low-grade tumours.

CONCLUSIONS

A significant correlation was detected in the gene expression level of PSCA with histological grade, clinicopathological stage and prognosis in CC-RCC. Our data indicate that PSCA is associated with carcinogenesis and progression of CC-RCC.

Identification and immunotherapeutic targeting of antigens induced by chemotherapy

Cancer cells differ from normal cells in their response to chemotherapy. We exploited this dissimilarity by identifying and targeting tumor-specific, cell-surface proteins whose expression is induced by the chemotherapeutic irinotecan (CPT-11; Camptosar). A cytotoxin-armed antibody reactive with one of these drug-induced surface proteins, the LY6D/E48 antigen, originally identified as the target of a monoclonal antibody reactive with squamous cell carcinomas, caused complete regression of colorectal tumor xenografts in mice treated with CPT-11, whereas either agent alone was less effective. These results suggest that a positive therapeutic index may be generated for other drug combinations by immunotherapeutic targeting of chemotherapy-induced antigens.

Co-regulation of p16INK4A and migratory genes in culture conditions that lead to premature senescence in human keratinocytes

Cellular stasis, also known as telomere-independent senescence, prevents many epithelial cells from becoming immortalized by telomerase alone. As human keratinocytes age in culture, protein levels of the tumor suppressor p16INK4a continue to increase, resulting in growth arrest independent of telomere length. Differences in culture conditions have been shown to modulate both p16INK4a expression and replicative capacity of human keratinocytes; however, the mechanism of p16INK4a induction under these conditions is unknown. Using multiple primary keratinocyte cell strains, we verified a delay in p16INK4a induction and an extended lifespan of human keratinocytes when grown in co-culture with post-mitotic fibroblast feeder cells as compared with keratinocytes grown on tissue culture plastic alone. Evaluation of gene expression levels in the two culture conditions by microarray analysis, and subsequent validation, demonstrated that keratinocytes cultured on plastic alone had significantly increased expression of many genes involved in keratinocyte migration and reduced expression levels of genes involved in keratinocyte differentiation. Higher levels of p16INK4a expression were present in cells that also displayed increased amounts of autophosphorylated focal adhesion kinase and urokinase plaminogen activator receptor (uPAR), both markers of keratinocyte migration. Furthermore, when tyrosine phosphorylation or urokinase-type plasminogen activator (uPA)/uPAR function was inhibited, both keratinocyte migration and p16INK4a expression were reduced. Our results indicate that keratinocytes cultured in the absence of feeder cells exhibit a migratory phenotype and suggest that p16INK4a is selectively induced under these conditions by a mechanism involving tyrosine kinase activity and the urokinase plasminogen activation system.

Genetic reprogramming of tumor cells by zinc finger transcription factors

Cancer arises by the accumulation of genetic alterations in DNA leading to aberrant gene transcription. Expression-profiling studies have correlated genomewide expression signatures with malignancy. However, functional analysis elucidating the contribution and synergy of genes in specific cancer cell phenotypes remains a formidable obstacle. Herein, we describe an alternative genetic approach for identification of genes involved in tumor progression by using a library of zinc finger artificial transcription factors (ATFs) and functional screening of tumor cells as a source of genetic plasticity and clonal selection. We isolated a six-zinc finger transcriptional activator (TF 20-VP, TF 20 containing the VP64 activator domain) that acts to reprogram a drug-sensitive, poorly invasive, and nonmetastatic cell line into a cell line with a drug-resistant, highly invasive, and metastatic phenotype. Differential expression profiles of cells expressing TF 20-VP followed by functional studies, both in vitro and in animal models, revealed that invasion and metastasis requires co-regulation of multiple target genes. Significantly, the E48 antigen, associated with poor metastasis-free survival in head and neck cancer, was identified as one specific target of TF 20-VP. We have shown phenotypic modulation of tumor cell behavior by E48 expression, including enhanced cell migration in vitro and tumor cell dissemination in vivo. This study demonstrates the use of ATFs to identify the group of genes that cooperate during tumor progression. By co-regulating multiple targets, ATFs can be used as master genetic switches to reprogram and modulate complex neoplastic phenotypes.

Radioimmunodetection and radioimmunotherapy of head and neck cancer

Radiolabeled monoclonal antibodies (MAbs) can add a dimension to diagnostic imaging and staging of metastatic head and neck cancer, as well as in eradication of this disease. The vast majority of malignancies arising in the oral cavity, pharynx and larynx are squamous cell carcinomas. This common cellular origin makes it attractive to search for appropriate tumor-associated antigens, which are preferentially expressed in these neoplasms. Radiolabeled MAbs directed against these antigens can be used for tumor detection and selective therapy, known as radioimmunoscintigraphy and radioimmunotherapy, respectively. The combination of MAbs with positron emission tomography (PET) is an attractive novel option to improve tumor detection and to facilitate MAb quantification in a therapeutic setting. Basic aspects of tumor targeting with MAbs, as well as a review of the clinical trials reported in the literature, including own results, are presented.

Prostate stem cell antigen (PSCA) expression in human prostate cancer tissues: implications for prostate carcinogenesis and progression of prostate cancer

OBJECTIVE

Prostate stem cell antigen (PSCA) is a recently defined homolog of the Thy-1/Ly-6 family of glycosylphosphatidylinositol (GPI)-anchored cell surface antigens. The objective of the present study was to examine the expression status of PSCA protein and mRNA in clinical specimens of human prostate cancer (PCa) and to validate it as a potential molecular target for diagnosis and treatment of PCa.

METHODS

Immunohistochemical (IHC) and in situ hybridization (ISH) analyses of PSCA expression were simultaneously performed on paraffin-embedded sections of 20 benign prostatic hyperplasia (BPH), 20 prostatic intraepithelial neoplasm (PIN) and 48 prostate cancer (PCa) tissues, including 9 androgen-independent prostate cancers. The level of PSCA expression was semiquantitatively scored by assessing both the percentage and intensity of PSCA-positive staining cells in the specimens. We then compared the PSCA expression between BPH, PIN and PCa tissues and analyzed the correlations of PSCA expression level with pathological grade, clinical stage and progression to androgen-independence in PCa.

RESULTS

In BPH and low grade PIN, PSCA protein and mRNA staining were weak or negative and less intense and uniform than that observed in high grade PIN (HGPIN) and PCa. Moderate to strong PSCA protein and mRNA expression were noted in 8 of 11 (72.7%) HGPIN and in 40 of 48 (83.4%) PCa specimens examined by IHC and ISH analyses, and their statistical significance was compared with BPH (20%) and low-grade PIN (22.2%) specimens (P < 0.05). The expression level of PSCA increased with a higher Gleason grade, advanced stage and progression to androgen-independence (P < 0.05). In addition, IHC and ISH staining revealed a high degree of correlation between PSCA protein and mRNA overexpression.

CONCLUSIONS

Our data demonstrate that PSCA as a new cell surface marker is overexpressed in a majority of cases of human PCa. PSCA expression correlates positively with adverse tumor characteristics, such as increasing pathological grade (poor cell differentiation), worsening clinical stage and androgen-independence and speculatively with prostate carcinogenesis. PSCA may possess prognostic utility and may be a promising molecular target for diagnosis and treatment of PCa.

Prostate stem cell antigen (PSCA) expression in human prostate cancer tissues and its potential role in prostate carcinogenesis and progression of prostate cancer

BACKGROUND

Prostate stem cell antigen (PSCA) is a recently defined homologue of the Thy-1/Ly-6 family of glycosylphosphatidylinositol (GPI)-anchored cell surface antigens. The purpose of the present study was to examine the expression status of PSCA protein and mRNA in clinical specimens of human prostate cancer (Pca) and to validate it as a potential molecular target for diagnosis and treatment of Pca.

MATERIALS AND METHODS

Immunohistochemical (IHC) and in situ hybridization (ISH) analyses of PSCA expression were simultaneously performed on paraffin-embedded sections from 20 benign prostatic hyperplasia (BPH), 20 prostatic intraepithelial neoplasm (PIN) and 48 prostate cancer (Pca) tissues, including 9 androgen-independent prostate cancers. The level of PSCA expression was semiquantitatively scored by assessing both the percentage and intensity of PSCA-positive staining cells in the specimens. Then compared PSCA expression between BPH, PIN and Pca tissues and analysed the correlations of PSCA expression level with pathological grade, clinical stage and progression to androgen-independence in Pca.

RESULTS

In BPH and low grade PIN, PSCA protein and mRNA staining were weak or negative and less intense and uniform than that seen in HGPIN and Pca. There were moderate to strong PSCA protein and mRNA expression in 8 of 11 (72.7%) HGPIN and in 40 of 48 (83.4%) Pca specimens examined by IHC and ISH analyses, with statistical significance compared with BPH (20%) and low grade PIN (22.2%) samples (p < 0.05, respectively). The expression level of PSCA increased with high Gleason grade, advanced stage and progression to androgen-independence (p < 0.05, respectively). In addition, IHC and ISH staining showed a high degree of correlation between PSCA protein and mRNA overexpression.

CONCLUSIONS

Our data demonstrate that PSCA as a new cell surface marker is overexpressed by a majority of human Pca. PSCA expression correlates positively with adverse tumor characteristics, such as increasing pathological grade (poor cell differentiation), worsening clinical stage and androgen-independence, and speculatively with prostate carcinogenesis. PSCA protein overexpression results from upregulated transcription of PSCA mRNA. PSCA may have prognostic utility and may be a promising molecular target for diagnosis and treatment of Pca.

CD177: A member of the Ly-6 gene superfamily involved with neutrophil proliferation and polycythemia vera

Genes in the Leukocyte Antigen 6 (Ly-6) superfamily encode glycosyl-phosphatidylinositol (GPI) anchored glycoproteins (gp) with conserved domains of 70 to 100 amino acids and 8 to 10 cysteine residues. Murine Ly-6 genes encode important lymphocyte and hematopoietic stem cell antigens. Recently, a new member of the human Ly-6 gene superfamily has been described, CD177. CD177 is polymorphic and has at least two alleles, PRV-1 and NB1. CD177 was first described as PRV-1, a gene that is overexpressed in neutrophils from approximately 95% of patients with polycythemia vera and from about half of patients with essential thrombocythemia. CD177 encodes NB1 gp, a 58–64 kD GPI gp that is expressed by neutrophils and neutrophil precursors. NB1 gp carries Human Neutrophil Antigen (HNA)-2a. Investigators working to identify the gene encoding NB1 gp called the CD177 allele they described NB1. NB1 gp is unusual in that neutrophils from some healthy people lack the NB1 gp completely and in most people NB1 gp is expressed by a subpopulation of neutrophils. The function of NB1 gp and the role of CD177 in the pathogenesis and clinical course of polycythemia vera and essential thrombocythemia are not yet known. However, measuring neutrophil CD177 mRNA levels has become an important marker for diagnosing the myeloproliferative disorders polycythemia vera and essential thrombocythemia.

SAMP14, a novel, acrosomal membrane-associated, glycosylphosphatidylinositol-anchored member of the Ly-6/urokinase-type plasminogen activator receptor superfamily with a role in sperm-egg interaction

We report a new member of the Ly-6/urokinase-type plasminogen activator receptor (uPAR) superfamily of receptors, SAMP14, which is retained on the inner acrosomal membrane of the human spermatozoan following the acrosome reaction and may play a role in fertilization. The SAMP14 sequence predicted a glycosylphosphatidylinositol (GPI)-anchored protein with a signal peptide, a transmembrane domain near the carboxyl terminus, and a putative transamidase cleavage site in the proprotein. Attachment of SAMP14 to the membrane by a lipid anchor was confirmed by its sensitivity to phosphatidylinositol phospholipase C. SAMP14 has a single functional domain similar to the Ly-6 and urokinase plasminogen activator receptor superfamily of proteins, and the gene mapped to 19q13.33, near the PLAUR locus for uPAR at 19q13.2. Northern and dot blotting showed that SAMP14 expression was testis-specific. Indirect immunofluorescence and immunoelectron microscopy with antisera to purified recombinant SAMP14 localized the protein to outer and inner acrosomal membranes as well as the acrosomal matrix of ejaculated human sperm. Acrosome-reacted sperm demonstrated SAMP14 immunofluorescence, indicating its retention on the inner acrosomal membrane following the acrosome reaction. However, SAMP14 localized to the entire sperm when unwashed swim-up sperm from the ejaculate were stained, indicating that some SAMP14 is loosely associated with the plasma membrane. Antibodies against recombinant SAMP14 inhibited both the binding and the fusion of human sperm to zona free hamster eggs, suggesting that SAMP14 may have a role in sperm-egg interaction. SAMP14 represents a GPI-anchored putative receptor in the Ly-6/uPAR family that is exposed on the inner acrosomal membrane after the acrosome reaction.