An association between high Ly-6A/E expression on tumor cells and a highly malignant phenotype

Single-Cell RNA Sequencing Reveals Immuno-Oncology Characteristics of Tumor-Infiltrating T Lymphocytes in Photodynamic Therapy-Treated Colorectal Cancer Mouse Model

Photodynamic therapy (PDT) has shown promise in reducing metastatic colorectal cancer (CRC); however, the underlying mechanisms remain unclear. Modulating tumor-infiltrating immune cells by PDT may be achieved, which requires the characterization of immune cell populations in the tumor microenvironment by single-cell RNA sequencing (scRNA-seq). Here, we determined the effect of Chlorin e6 (Ce6)-mediated PDT on tumor-infiltrating T cells using scRNA-seq analysis. We used a humanized programmed death-1/programmed death ligand 1 (PD-1/PD-L1) MC38 cell allograft mouse model, considering its potential as an immunogenic cancer model and in combination with PD-1/PD-L1 immune checkpoint blockade. PDT treatment significantly reduced tumor growth in mice containing hPD-1/PD-L1 MC38 tumors. scRNA-seq analysis revealed that the PDT group had increased levels of CD8+ activated T cells and CD8+ cytotoxic T cells, but decreased levels of exhausted CD8+ T cells. PDT treatment also enhanced the infiltration of CD8+ T cells into tumors and increased the production of key effector molecules, including granzyme B and perforin 1. These findings provide insight into immune-therapeutic modulation for CRC patients and highlight the potential of PDT in overcoming immune evasion and enhancing antitumor immunity.

A novel role of hematopoietic CCL5 in promoting triple-negative mammary tumor progression by regulating generation of myeloid-derived suppressor cells

CCL5 is a member of the CC chemokine family expressed in a wide array of immune and non-immune cells in response to stress signals. CCL5 expression correlates with advanced human breast cancer. However, its functional significance and mode of action have not been established. Here, we show that CCL5-deficient mice are resistant to highly aggressive, triple-negative mammary tumor growth. Hematopoietic CCL5 is dominant in this phenotype. The absence of hematopoietic CCL5 causes aberrant generation of CD11b(+)/Gr-1(+), myeloid-derived suppressor cells (MDSCs) in the bone marrow in response to tumor growth by accumulating Ly6C(hi) and Ly6G(+) MDSCs with impaired capacity to suppress cytotoxicity of CD8(+) T cells. These properties of CCL5 are observed in both orthotopic and spontaneous mammary tumors. Antibody-mediated systemic blockade of CCL5 inhibits tumor progression and enhances the efficacy of therapeutic vaccination against non-immunogenic tumors. CCL5 also helps maintain the immunosuppressive capacity of human MDSCs. Our study uncovers a novel, chemokine-independent activity of the hematopoietically derived CCL5 that promotes mammary tumor progression via generating MDSCs in the bone marrow in cooperation with tumor-derived colony-stimulating factors. The study sheds considerable light on the interplay between the hematopoietic compartment and tumor niche. Because of the apparent dispensable nature of this molecule in normal physiology, CCL5 may represent an excellent therapeutic target in immunotherapy for breast cancer as well as a broad range of solid tumors that have significant amounts of MDSC infiltration.

Genetic variant as a selection marker for anti-prostate stem cell antigen immunotherapy of bladder cancer

A monoclonal antibody against prostate stem cell antigen (PSCA) has emerged as a novel cancer therapy currently being tested in clinical trials for prostate and pancreatic cancers, but this treatment is likely to be efficient only in patients with PSCA-expressing tumors. The present study demonstrates that a genetic variant (rs2294008) discovered by bladder cancer genome-wide association studies is a strong predictor of PSCA protein expression in bladder tumors, as measured by two-sided multivariable linear regression (P = 6.46×10⁻¹¹; n = 278). The association pattern is similar in non-muscle-invasive tumors, stages Ta (P = 3.10×10⁻⁵; n = 173) and T1 (P = 2.64×10⁻⁵; n = 60), and muscle-invasive tumors, stages T2 (P =.01; n = 23) and T3/4 (P =.03; n = 22). The study suggests that anti-PSCA immunotherapy might be beneficial for bladder cancer patients with high tumor PSCA expression, which is statistically significantly associated with the presence of CT and TT genotypes of a common genetic variant, rs2294008. Future clinical studies will be needed to validate PSCA as a therapeutic target for bladder cancer.

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.

Ras activation contributes to the maintenance and expansion of Sca-1pos cells in a mouse model of breast cancer

The cancer stem cell (CSC) hypothesis proposes that CSCs are the root of cancer and cause cancer metastasis and recurrence. In this study, we examined whether Ras signaling is associated with stemness of the CSCs population characterized by the stem cell antigen (Sca-1) phenotype in a 4T1 syngeneic mouse model of breast cancer. The Sca-1(pos) putative CSCs had high levels of activated Ras and phosphorylated MEK (p-MEK), compared with counterparts. The Ras farnesylation inhibitor (FTI-277) suppressed the maintenance and expansion of CSCs. Therefore, selective inhibition of Ras activation may be useful for stem-specific cancer therapy.

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.

DNA vaccination with CD44 variant isoform reduces mammary tumor local growth and lung metastasis

We have shown recently that cDNA vaccination, using a virtual lymph node, ameliorates experimental allergic encephalomyelitis. Successful cure from mammary tumor requires resolution of local tumor growth and metastases. We have examined whether targeting of CD44 cell surface adhesion molecule by cDNA vaccination plays a role in resolving mammary tumor development. We show here that CD44 cDNA vaccination decreases the tumor mass and metastatic potential in experimental mammary tumor of BALB/c mice. Vaccination of mice, inoculated with the mammary tumors, by cDNA of CD44 variant (CD44v) but not by cDNA of standard CD44, markedly reduced local tumor development and lung metastasis. Concomitantly, transfection of CD44 antisense into a highly metastatic mammary tumor cell line disrupted the CD44 expression of the cells and reduced their ability to establish local tumors as well as metastatic colonies in the lung. Moreover, when CD44v, but not standard CD44 sense cDNA, was transfected into the poorly metastatic cell line, tumor development was markedly enhanced. It is possible therefore that DNA vaccination with a specific CD44v construct could induce an immune resistance to mammary tumor progression.

Concise review: stem cell antigen-1: expression, function, and enigma

Cloned 20 years ago, stem cell antigen-1 (Sca-1) is used extensively to enrich for murine hematopoietic stem cells. The realization that many different stem cell types share conserved biochemical pathways has led to a flood of recent research using Sca-1 as a candidate marker in the search for tissue-resident and cancer stem cells. Although surprisingly little is still known about its biochemical function, the generation and analysis of knockout mice has begun to shed light on the functions of Sca-1 in stem and progenitor cells, demonstrating that it is more than a convenient marker for stem cell biologists. This review summarizes the plethora of recent findings utilizing Sca-1 as a parenchymal stem cell marker and detailing its functional role in stem and progenitor cells and also attempts to explain the lingering mysteries surrounding its biochemical function and human ortholog. Disclosure of potential conflicts of interest is found at the end of this article.

Normal breast stem cells, malignant breast stem cells, and the perinatal origin of breast cancer

Both experimental and epidemiological evidence support the concept that the in utero environment can influence an individual's risk of breast cancer in adult life. Recently identified breast stem cells may be the key to understanding the mechanism underlying this phenomenon. It has been theorized that breast cancers arise from breast stem cells. Our emerging view of the characteristics of normal breast stem cells and their link to malignant breast stem cells is reviewed here. It has also been postulated that factors that expand the normal breast stem cell pool in utero would increase the probability that one such cell might undergo an oncogenic mutation or epigenetic change. We discuss how a number of proposed perinatal determinants of adult breast cancer risk, including (1) in utero estrogen and IGF-1 levels, (2) birthweight, (3) breast density, and (4) early-life mutagen exposure, can be tied together by this "breast stem cell burden" hypothesis.

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.

Pregnancy and stem cell behavior

The identification of cancer-initiating epithelial subtypes (i.e. cancer stem cells) is important for gaining a more comprehensive understanding of the process of neoplastic transformation and tumorigenesis. Since reproductive history has a major impact on breast tumorigenesis, it is reasonable to assume that pregnancy and lactation have enduring effects on the cancer susceptibility of multipotent progenitors. Using the Cre-lox technology as a tool to genetically label pregnancy-hormone-responsive cells, we identified a mammary epithelial subtype that is abundant in parous females. These pregnancy-induced mammary epithelial cells (PI-MECs) originate from differentiating cells during the first pregnancy and lactation cycle. They do not undergo apoptosis during postlactational remodeling, and they persist throughout the remainder of a female's life. In this review, we discuss the biological relevance of PI-MECs in multiparous females and their important stem cell-like features, such as self renewal, as well as their ability to produce progeny with diverse cellular fates. Using appropriate animal models, we further demonstrate that PI-MECs are cellular targets for pregnancy-enhanced mammary tumorigenesis.

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.

Characterization of the human Ly-6 antigens, the newly annotated member Ly-6K included, as molecular markers for head-and-neck squamous cell carcinoma

The E48 antigen is a successfully explored molecular marker for the diagnosis and therapy of HNSCC. The applicability of E48 as an HNSCC-associated antigen, however, is restricted due to its heterogeneous expression in 30% of tumors; and identification of additional target antigens is therefore desired. E48 belongs to the Ly-6 antigen family, comprising a group of highly homologous, low m.w., GPI-anchored surface proteins, of which some show tissue-restricted expression patterns. To identify novel human HNSCC-associated Ly-6 members with squamous cell-associated expression patterns, we performed comprehensive gene-screening consisting of BLAST searches within GenBank databases, followed by expression analysis. Using this approach, the Ly-6K gene could be annotated as a novel member of the human Ly-6 family. Expression of the human Ly-6 genes E48, Ly-6K, PSCA, GML, RIG-E, G6C and Ly-6H was prescreened by qualitative RT-PCR and subsequently analyzed by quantitative RT-PCR in normal keratinocytes, HNSCC cell lines, normal mucosa, HNSCC tumors as well as normal peripheral blood and bone marrow cells. PSCA was highly expressed in normal mucosa, but 100-fold decreased expression was seen in HNSCC. For Ly-6H, GML and G6C, no or very low expression was observed in keratinocytes and HNSCC. Expression of RIG-E was high in normal and malignant squamous cells and in peripheral blood and bone marrow cells, thus limiting its applicability as an HNSCC-associated marker. In contrast, besides the E48 gene, the Ly-6K gene also appeared to be selectively expressed in HNSCC and normal squamous cells. Moreover, expression of Ly-6K was shown in HNSCC cell lines, in which no E48 expression could be detected. These data justify further evaluation of Ly-6K as potential target antigen for the diagnosis and therapy of HNSCC.

Expression of Ly-6D on the surface of normal and neoplastic mammary epithelial cells of the mouse

Rat were immunized with mouse mammary epithelial cells and monoclonal antibodies (MAbs) were obtained to identify antigens stably expressed on the surface of both normal and neoplastic mammary epithelial cells of the mouse. Examination of the reactivities of the MAbs by immunofluorescence staining of tissue sections showed that one of the antibodies, MAb 2A2, reacted with luminal epithelium of the mammary gland and spontaneous mammary carcinomas of SHN mice. Further examination of the tissue lysates by western blot analysis revealed that MAb 2A2 reacts with a 17-kDa antigen expressed in normal mammary epithelial cells and mammary carcinoma cells. The antigen recognized by MAb 2A2 was absent in the lysates of liver, lung, salivary gland, kidney, small intestine, ovary and uterus. After immunoaffinity purification of the MAb 2A2-recognized antigen and determination of its N-terminal amino acid sequence, we identified the antigen as Ly-6D, also known as ThB, which belongs to a family of glycosyl-phosphatidylinositol-anchored cell surface proteins. Northern blot analysis further demonstrated that Ly-6D mRNA is expressed in the mammary gland. Based on these observations we concluded that Ly-6D is stably expressed on the surface of both normal and neoplastic mammary epithelial cells of the mouse. Ly-6D will serve as a useful epithelial cell surface marker for the study of mammary gland development, as well as for breast cancer research.

Possible co-regulation of genes associated with enhanced progression of mammary adenocarcinomas

Tumor progression is a multistep process in which alterations in the expression of numerous gene products may give rise to highly malignant cellular variants. In the present study, we analyzed the differential expression of several genes in cellular variants of mammary adenocarcinomas with high or low malignancy potential, which originated in a common ancestor. To assess the generality of our findings, high and low malignancy variants were derived from two different mammary adenocarcinoma cell lines, namely DA3 and CSML cells. Of major importance is the fact that the differences between high- and low-malignancy variants observed in one system of mammary adenocarcinoma cells (DA3 cells) were identically reproduced in the other system of mammary adenocarcinoma cells (CSML cells). The high malignancy variants of tumors both DA3-high and CSML-high (previously called CSML-100), expressed higher levels of factors that induce monocyte migration than the low malignancy DA3-low and CSML-low (previously called CSML-0) variants. In addition, it was found that DA3-high and CSML-high cell variants expressed higher levels of monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6) and matrix metalloproteinases (MMPs) than the low malignancy variants (DA3-low and CSML-low). These results suggest that MCP-1, IL-6 and MMPs potentially contribute to mammary adenocarcinoma progression and that their expression is regulated by a common pathway. The expression of MCP-1, IL-6 and MMPs in both DA3-high and CSML-high cells was up-regulated by tumor necrosis factor alpha (TNFalpha). The fact that TNFalpha exerted similar effects on the expression of these three factors in both cell systems raises the possibility of a coordinated co-regulation of tumor-promoting factors.

Sca-1(pos) cells in the mouse mammary gland represent an enriched progenitor cell population

Mammary epithelium can functionally regenerate upon transplantation. This renewal capacity has been classically ascribed to the function of a multipotent mammary gland stem cell population, which has been hypothesized to be a primary target in the etiology of breast cancer. Several complementary approaches were employed in this study to identify and enrich mammary epithelial cells that retain stem cell characteristics. Using long-term BrdU labeling, a population of label retaining cells (LRCs) that lack expression of differentiation markers has been identified. LRCs isolated from mammary primary cultures were enriched for stem cell antigen-1 (Sca-1) and Hoechst dye-effluxing "side population" properties. Sca-1(pos) cells in the mammary gland were localized to the luminal epithelia by using Sca-1(+/GFP) mice, were progesterone receptor-negative, and did not bind peanut lectin. Finally, the Sca-1(pos) population is enriched for functional stem/progenitor cells, as demonstrated by its increased regenerative potential compared with Sca-1(neg) cells when transplanted into the cleared mammary fat pads of host mice.

Human Ly-6 antigen E48 (Ly-6D) regulates important interaction parameters between endothelial cells and head-and-neck squamous carcinoma cells

Selectin ligands are crucial components in the interaction between endothelial cells and extravasating cancer cells and, thus, play an important role in metastasis formation. Head-and-neck squamous cell carcinoma (HNSCC) variants expressing high levels of E48, a human Ly-6 protein (E48(hi)), expressed higher levels of the fucose-generating FX enzyme and of the fucosylated E-selectin ligand sLe(a) than cells expressing low levels of E48 (E48(lo)). Signaling through E48 upregulated expression levels of these molecules in HNSCC. In this work, we provide further evidence supporting the E48-FX-sLe(a) link by showing that FX antisense oligonucleotides reduced sLe(a) expression levels in HNSCC. We also show that E48 may be causally involved in regulating expression levels in HNSCC of 2 additional enzymes involved in the biosynthesis of sLe(a), namely, ST-30 and FucTIII. Also, selectin-mediated adhesion of E48(hi) variants to activated HUVECs was significantly higher than that of E48(lo) variants. Transfection experiments utilizing sense or antisense E48 cDNA indicated that E48 may be causally involved in this adhesion. Chemokines are involved in the extravasation process of tumor cells. The release of chemoattractants from HNSCC variants differing in E48 expression was therefore analyzed. HNSCC did not release any chemoattractants but induced the release of such factors from HUVECs. Supernatants from E48(hi) variants were significantly more efficient than E48(lo) cells at inducing the release of chemoattractants from HUVECs. Transfection experiments indicated that E48 may be causally involved in the induction of chemoattractant release from HUVECs. Angiogenesis is an important manifestation of cancer-endothelium interactions. We therefore assayed for the presence of angiogenic factors in culture supernatants of HNSCC. Supernatants from E48(lo) variants contained significantly higher amounts of PDGF than E48(hi) cells. Transfection experiments indicated that E48 may be causally involved. Taken together, our results suggest that E48 controls important interaction parameters between HNSCC and endothelial cells.

Receptors involved in microenvironment-driven molecular evolution of cancer cells

Cells, including cancer cells, communicate with their microenvironment via various types of membrane receptors. An important down-stream effect of such interactions is a change in the molecular phenotype of the cells. The microenvironment-driven molecular evolution of cancer cells may induce either growth arrest or death of the cells or alternatively, boost their malignancy phenotype. In this paper we summarize studies from our own laboratory on interactions of cancer cells with microenvironmental ligands via two types of receptors that are not commonly associated with tumour progression i.e. the receptor for the Fc portion of IgG, and Ly-6 proteins of mouse and human origin. We also review information on interactions of tumour-associated chemokines and chemokine receptors with the corresponding microenvironmental factors. We demonstrate how these interactions may drive the molecular evolution of tumour cells and discuss the possible impact of this evolution on tumour progression.

Tumour cell-dendritic cell fusion for cancer immunotherapy: comparison of therapeutic efficiency of polyethylen-glycol versus electro-fusion protocols

BACKGROUND

Fusion of tumour cells with dendritic cells (DC) is a powerful new technology to increase tumour vaccine immunogenicity. The aim of this study was to compare fusion protocols with syngenic DCs with respect to the efficiency of polyethylen-glycol-(PEG) and electric pulse-mediated fusions for induction of protective anti-tumour immune responses. As a model we chose a low immunogenic and metastatic murine mammary carcinoma cell line, which mimics clinically relevant tumour features.

METHODS

FACS-staining, chromium release assay, therapeutic immunization, adoptive transfer.

RESULTS

We show that the parental line with low cell surface expression of MHC molecules as well as a lacZ transfectant becomes highly immunogenic upon fusion with DCs. This was true for PEG- as well as for electro-fused cells. Immunization with products of DCs and tumour cells cocultivated for 16 h without the fusing agent PEG also caused induction of profound anti-tumour immunity, while this was not the case when using parental tumour cells or their lacZ transfectants as vaccines. Immune protection against the parental tumour cells after vaccination with fused cells was long-lasting and could be transferred via immune spleen cells into immuno-incompetent nude (nu/nu) mice.

CONCLUSION

Fusion products of DA3(hi) mammary carcinoma cells and DCs produced by an electric pulse were similar to those produced by PEG fusion with regard to vaccine potency in prophylactic antitumour immunization assays in vivo. Therefore, both techniques seem to be promising for clinical application.

Uniquely conserved non-translated regions are involved in generation of the two major transcripts of protein phosphatase 2Cbeta

Partial cDNAs of different isoforms of protein phosphatase 2Cbeta (PP2Cbeta or PPM1B) have been characterized in mammals. We disclose here the full cDNAs of two major PP2Cbeta isoforms from human, rat and mouse. These cDNAs (2.6 and 3.3 kb) are able to encode 53 kDa (PP2Cbetal) and 43 kDa (PP2Cbetas) polypeptides, respectively. The isoforms are co-expressed ubiquitously with the highest level in skeletal muscle, as assessed by Northern-blot analysis. Western and in situ analyses using monoclonal antibodies against PP2Cbeta confirmed the existence of two isoforms in the cytoplasm. Comparative sequence analysis revealed that both cDNAs consist of six exons with an alternate usage of the 3' exons that underlies the differences between them. The genomic structure of PP2Cbeta is similar to that of other PP2C paralogs and includes a non-coding first exon followed by a large intron and a large second exon that encoded most of the catalytic domain. Both variants of the ending exon include large non-coding regions. All non-translated regions (NTRs) are highly conserved between the orthologous genes, indicating their regulatory function. The 5'-NTR is long (379 bp), includes upstream start codons and is predicted to contain stable secondary structures. Such features inhibit translation initiation by the scanning mechanism. Introduction of this NTR element into a bi-luciferase expression-cassette enabled expression of the second cistron, suggesting that it might serve as an internal ribosome entry site, or it contains a cryptic promoter. Overexpression of PP2Cbeta under CMV-promoter in 293 cells led to cell-growth arrest or cell death.

Expression of Ly-6A/E in the mouse uterus during implantation period

To investigate the molecular mechanisms of implantation, we constructed a complementary DNA library of mouse uterus enriched with pregnancy-induced genes by subtractive hybridization and polymerase chain reaction. One of the isolated clones was a part of complementary DNA for the Ly-6A/E. Ly-6A/E is reported to be differentially expressed on hematopoietic stem cells and some lymphoid and nonlymphoid tissues, mediate cell-cell adhesion on lymphoid cells, and associate with cell proliferation and angiogenesis of tumor cells. Northern blot, in situ hybridization, and immunohistochemical analyses demonstrated that the Ly-6A/E mRNA and protein were expressed in the endometrial epithelial cells as well as myometrial cells and vascular endothelial cells in the uterus of nonpregnant mouse. The expression was downregulated in luminal epithelial cells during pregnancy days 1-5, while it was upregulated in decidualized stromal cells around the implanted embryo at the time of implantation. The signals were primarily localized in stromal cells at the mesometrial pole on day 9. The increased expression was also observed in stromal cells of the embryo-transferred uterus and artificially-induced deciduoma, indicating that the expression of Ly-6A/E in the endometrial cells is concurrent with decidualization. These findings suggest that Ly-6A/E plays a role in embryo implantation.

Peroxisome proliferator-activated receptor alpha-dependent induction of cell surface antigen Ly-6D gene in the mouse liver

Spontaneous peroxisome proliferation-related pleiotropic responses occurring in the liver of mice lacking peroxisomal fatty acyl-CoA oxidase (AOX-/-) are attributed to sustained activation of peroxisome proliferator-activated receptor alpha (PPARalpha) by its putative natural ligands that require AOX for their metabolism. In this study, using a gene expression screen, we show that Ly-6 (lymphocyte antigen 6 complex, locus D; mouse ThB), which belongs to a distinctive family of low molecular weight phosphatidyl inositol anchored cell surface glycoproteins, is upregulated in mouse liver with peroxisome proliferation. Increases in Ly-6D mRNA levels are observed in AOX-/- mouse liver with spontaneous peroxisome proliferation and also in the liver of wild-type mice treated with synthetic peroxisome proliferators. Peroxisome proliferators failed to increase hepatic Ly-6D mRNA levels in mice lacking PPARalpha (PPARalpha-/-), suggesting a regulatory role for PPARalpha in the induction of Ly-6D. These observations suggest that changes in certain cell surface proteins also form part of the pleiotropic responses associated with peroxisome proliferation.

A monoclonal antibody against the 66-kDa protein expressed in mouse spleen and thymus inhibits Ly-6A.2-dependent cell-cell adhesion

The Ly-6 locus encodes several cell surface proteins of 10-12 kDa. Some members of this multigene family may function in cell signaling and/or cell adhesion processes. T lymphocytes overexpressing Ly-6A.2 (one member of the Ly-6 gene family) protein homotypically aggregate when cultured in vitro. Further analysis of this homotypic aggregation suggests that Ly-6A.2 participates in cell-cell adhesion. These observations indicated the presence of a Ly-6 ligand(s) on the surface of lymphoid cells. In this study we report generation of a hamster mAb, 9AB2, that blocks Ly-6A.2-dependent cell-cell adhesion. The 9AB2 Ab recognizes a 66-kDa glycoprotein with unique tissue expression. The 9AB2 mAb does not bind Ly-6A.2, but coimmunoprecipitates Ly-6A.2 molecule. Moreover, 9AB2 Ag-expressing thymocytes specifically bind to Chinese hamster ovary cells overexpressing Ly-6A.2 protein, and this binding is specifically blocked by 9AB2 and anti-Ly-6A.2 Abs. These results suggest that the 66-kDa protein recognized by 9AB2 mAb is the putative ligand for Ly-6A.2.

Perforin Is a Major Contributor to NK Cell Control of Tumor Metastasis

We provide the first demonstration, using experimental and spontaneous models of metastasis in C57BL/6 (B6) (RM-1 prostate carcinoma) and BALB/c (DA3 mammary carcinoma) mice, that tumor metastasis is primarily controlled by perforin-dependent cytotoxicity mediated by NK1.1+ cells. MHC class Ilow RM-1 and DA3 tumor cells were sensitive in vitro to Fas-mediated lysis or spleen NK cells in a perforin-dependent fashion. Perforin-deficient NK cells did not lyse these tumors, and perforin-deficient mice were 10–100-fold less proficient than wild-type mice in rejecting the metastasis of tumor cells to the lung. Fas ligand mutant gld mice displayed uncompromised protection against tumor metastasis. Depletion of NK subsets resulted in greater numbers of metastases than observed in perforin-deficient mice, suggesting that perforin-independent effector functions of NK cells may also contribute to protection from tumor metastasis.

MCP-1 expression as a potential contributor to the high malignancy phenotype of murine mammary adenocarcinoma cells

The search for mechanisms that regulate tumor progression has motivated the authors' laboratory to establish a unique murine model system, consisting of two lines of DA3 mammary adenocarcinoma cells that were derived originally from a common ancestor but differed in their malignant potential. Studies indicated that the highly malignant phenotype manifested by one of the cell lines (termed Ly-6hi DA3 cells) was associated with high expression of the Ly-6E.1 antigen. To characterize the mechanisms controlling the high malignancy phenotype expressed by Ly-6hi DA3 cells, the study was focussed on the potential contribution of tumor-derived factors to the high malignancy phenotype expressed by these cells. To this end, the expression of CC chemokines, major chemoattractants of monocytes and T cells, by the highly malignant Ly-6hi DA3 cells as compared to the low malignancy Ly-6lo DA3 cells was evaluated. The results indicate that the highly malignant cells express higher levels of factors that induce monocyte migration than the low malignancy cells. Two CC chemokines were shown to be highly produced by Ly-6hi DA3 cells, MIP-1alpha and MCP-1, of which only the latter was shown to contribute to the high migratory activity expressed by the high malignancy Ly-6hi DA3 cells. Since MCP-1 may attract monocytes to tumor sites, these findings suggest that monocyte-derived mediators, such as growth factors or angiogenic cytokines, have pro-malignancy effects that contribute to the high malignancy phenotype expressed by Ly-6hi DA3 cells.

Expression of Ly-6, a marker for highly malignant murine tumor cells, is regulated by growth conditions and stress

Ly-6E.1 is highly expressed in murine tumor cells with a high malignancy phenotype and may serve as a marker for such a phenotype. In this study, we examined the effects of various growth conditions and stress on the expression levels of Ly-6E.1 by tumor cells. Previous preliminary results have shown that murine DA3 mammary tumor cells expressing high levels of Ly-6E.1 (Ly-6(hi)) are more highly tumorigenic than the same tumor cells expressing low levels of this membrane protein (Ly-6(lo)). In this study, we demonstrate that mice bearing Ly-6(hi) DA3 tumors have a significantly higher burden of spontaneous pulmonary metastasis than mice bearing Ly-6(lo) DA3 tumors. Furthermore, the survival time of the former mice was significantly shorter than that of the latter ones. We further show that certain other members of the Ly-6 gene family such as Ly-6C.1 and Ly-6G.1 are coregulated with Ly-6E.1. This was shown to occur with respect to both DA3 cells as well as A3 tumor cells which are of fibroblast origin. However, these 2 cells differ with respect to regulation of Sca-2 (TSA1, another member of the Ly-6 family) expression on these cells. Levels of Sca-2 on A3 cells appear to be coregulated with Ly-6E.1 (i.e., Ly-6(hi) A3 cells express high levels of Sca-2 and Ly-6(lo) A3 cells express low levels of Sca-2). These 2 Ly-6 proteins were, however, not coregulated on DA3 cells. Both Ly-6(hi) as well as Ly-6(lo) DA3 cells express equal levels of Sca-2. Levels of Thy-1, another glycosylphosphatidylinositol (GPI)-anchored protein expressed by A3 tumor cells, were equally expressed by both Ly-6(hi) and Ly-6(lo) A3 tumor cells. Levels of Ly-6 (but not those of CD44) on A3 tumor cells were upregulated on cells from dense cultures but were not influenced by the position of the cells in the cell cycle. Stress conditions such as serum starvation or heat shock upregulated the expression of Ly-6 by the 2 types of tumor cells but did not induce apoptosis in these cells. The kinetics of the stress-dependent upregulation of Ly-6 expression differed, however, between the epithelial and fibroblastic tumor cells.

Prostate stem cell antigen: a cell surface marker overexpressed in prostate cancer

The identification of cell surface antigens is critical to the development of new diagnostic and therapeutic modalities for the management of prostate cancer. Prostate stem cell antigen (PSCA) is a prostate-specific gene with 30% homology to stem cell antigen 2, a member of the Thy-1/Ly-6 family of glycosylphosphatidylinositol (GPI)-anchored cell surface antigens. PSCA encodes a 123-aa protein with an amino-terminal signal sequence, a carboxyl-terminal GPI-anchoring sequence, and multiple N-glycosylation sites. PSCA mRNA expression is prostate-specific in normal male tissues and is highly up-regulated in both androgen-dependent and -independent prostate cancer xenografts. In situ mRNA analysis localizes PSCA expression in normal prostate to the basal cell epithelium, the putative stem cell compartment of the prostate. There is moderate to strong PSCA expression in 111 of 126 (88%) prostate cancer specimens examined by in situ analysis, including high-grade prostatic intraepithelial neoplasia and androgen-dependent and androgen-independent tumors. Flow cytometric analysis demonstrates that PSCA is expressed predominantly on the cell surface and is anchored by a GPI linkage. Fluorescent in situ hybridization analysis localizes the PSCA gene to chromosome 8q24.2, a region of allelic gain in more than 80% of prostate cancers. A mouse homologue with 70% amino acid identity and similar genomic organization to human PSCA has also been identified. These results support PSCA as a target for prostate cancer diagnosis and therapy.

TNFalpha and anti-Fas antibodies regulate Ly-6E.1 expression by tumor cells: a possible link between angiogenesis and Ly-6E.1

Angiogenic and poorly angiogenic tumor variants were obtained by an intraperitoneal inoculation of cells from clones of polyoma-virus transformed BALB/c 3T3 cells into syngeneic mice. The angiogenic tumor cells expressed a higher tumorigenicity phenotype and a higher capacity to produce artificial pulmonary metastases than cells from the poorly angiogenic tumors. The former cells expressed also significantly higher levels of the lymphocyte activation protein Ly-6E.1 than the former cells. The two types of cells did not differ in expression levels of CD44 and of a polyoma-virus specific membrane antigen. These results raise the possibility that the angiogenic phenotype is coregulated with Ly-6. The effect on Ly-6 expression of signal transduction through TNF receptors, functioning as pivotal regulators of angiogenesis was therefore studied. It was found that TNFalpha and more so antibodies against Fas down-regulate expression levels of Ly-6. This down-regulation seemed to be selective as expression levels of CD44 were not affected by this treatment.