Upregulation of C4.4A expression during progression of melanoma

Proteomics biomarker discovery for individualized prevention of familial pancreatic cancer using statistical learning

BACKGROUND

The low five-year survival rate of pancreatic ductal adenocarcinoma (PDAC) and the low diagnostic rate of early-stage PDAC via imaging highlight the need to discover novel biomarkers and improve the current screening procedures for early diagnosis. Familial pancreatic cancer (FPC) describes the cases of PDAC that are present in two or more individuals within a circle of first-degree relatives. Using innovative high-throughput proteomics, we were able to quantify the protein profiles of individuals at risk from FPC families in different potential pre-cancer stages. However, the high-dimensional proteomics data structure challenges the use of traditional statistical analysis tools. Hence, we applied advanced statistical learning methods to enhance the analysis and improve the results' interpretability.

METHODS

We applied model-based gradient boosting and adaptive lasso to deal with the small, unbalanced study design via simultaneous variable selection and model fitting. In addition, we used stability selection to identify a stable subset of selected biomarkers and, as a result, obtain even more interpretable results. In each step, we compared the performance of the different analytical pipelines and validated our approaches via simulation scenarios.

RESULTS

In the simulation study, model-based gradient boosting showed a more accurate prediction performance in the small, unbalanced, and high-dimensional datasets than adaptive lasso and could identify more relevant variables. Furthermore, using model-based gradient boosting, we discovered a subset of promising serum biomarkers that may potentially improve the current screening procedure of FPC.

CONCLUSION

Advanced statistical learning methods helped us overcome the shortcomings of an unbalanced study design in a valuable clinical dataset. The discovered serum biomarkers provide us with a clear direction for further investigations and more precise clinical hypotheses regarding the development of FPC and optimal strategies for its early detection.

Arsenic Exposure and Cancer-Related Proteins in Urine of Indigenous Bolivian Women

Indigenous people living in the Bolivian Andes are exposed through their drinking water to inorganic arsenic, a potent carcinogen. However, the health consequences of arsenic exposure in this region are unknown. The aim of this study was to evaluate associations between arsenic exposure and changes in cancer-related proteins in indigenous women (n = 176) from communities around the Andean Lake Poopó, Bolivia. Arsenic exposure was assessed in whole blood (B-As) and urine (as the sum of arsenic metabolites, U-As) by inductively coupled plasma-mass spectrometry (ICP-MS). Cancer-related proteins (N = 92) were measured in urine using the proximity extension assay. The median B-As concentration was 2.1 (range 0.60-9.1) ng/g, and U-As concentration was 67 (12-399) μg/L. Using linear regression models adjusted for age, urinary osmolality, and urinary leukocytes, we identified associations between B-As and four putative cancer-related proteins: FASLG, SEZ6L, LYPD3, and TFPI2. Increasing B-As concentrations were associated with lower protein expression of SEZ6L, LYPD3, and TFPI2, and with higher expression of FASLG in urine (no association was statistically significant after correcting for multiple comparisons). The associations were similar across groups with different arsenic metabolism efficiency, a susceptibility factor for arsenic toxicity. In conclusion, arsenic exposure in this region was associated with changes in the expression of some cancer-related proteins in urine. Future research is warranted to understand if these proteins could serve as valid biomarkers for arsenic-related toxicity.

Elevated Expression of LYPD3 Is Associated with Lung Adenocarcinoma Carcinogenesis and Poor Prognosis

Aberrant expression of LYPD3 plays an oncogenic role in several types of cancer. However, the functions of LYPD3 in lung adenocarcinoma (LUAD) remain unclear. Here, we investigated the regulatory function, clinical value, and prognostic significance of LYPD3 in LUAD patients. The gene expression and DNA methylation data of LUAD tumor and paracancerous tissues were obtained from The Cancer Genome Atlas (TCGA) database. The association between LYPD3 expression and clinicopathological variables was analyzed. The results showed that LYPD3 was highly expressed in LUAD tumor compared with paracancerous tissues, which was positively correlated with the race (p = 0.0448), tumor stage (p = 0.0191), and survival status (p < 0.001). Furthermore, the expression of LYPD3 was able to be regulated by the methylation in LYPD3 promoter region, which was positively associated with the overall survival. Furthermore, we explored the related pathways through which LYPD3 affects the pathogenesis and prognosis of LUAD by gene set enrichment analysis, and found that LYPD3 might affect the clinical manifestations of LUAD by regulating the P53 signaling pathway. In the future, we would focus on exploring the molecular mechanism of LYPD3 in the regulation of the occurrence and development of LUAD to provide a research basis for the screening of methylation markers related to the treatment and prognosis.

The Lineage Determining Factor GRHL2 Collaborates with FOXA1 to Establish a Targetable Pathway in Endocrine Therapy-Resistant Breast Cancer

Notwithstanding the positive clinical impact of endocrine therapies in estrogen receptor-alpha (ERα)-positive breast cancer, de novo and acquired resistance limits the therapeutic lifespan of existing drugs. Taking the position that resistance is nearly inevitable, we undertook a study to identify and exploit targetable vulnerabilities that were manifest in endocrine therapy-resistant disease. Using cellular and mouse models of endocrine therapy-sensitive and endocrine therapy-resistant breast cancer, together with contemporary discovery platforms, we identified a targetable pathway that is composed of the transcription factors FOXA1 and GRHL2, a coregulated target gene, the membrane receptor LYPD3, and the LYPD3 ligand, AGR2. Inhibition of the activity of this pathway using blocking antibodies directed against LYPD3 or AGR2 inhibits the growth of endocrine therapy-resistant tumors in mice, providing the rationale for near-term clinical development of humanized antibodies directed against these proteins.

Genome-wide compound heterozygosity analysis highlighted 4 novel susceptibility loci for congenital heart disease in Chinese population

Genome-wide association studies (GWASs) have achieved great success in deciphering the genetic cause of congenital heart disease (CHD). However, the heritability of CHD remains to be clarified, and numerous genetic factors responsible for occurrence of CHD are yet unclear. In this study, we performed a genome-wide search for relaxed forms of compound heterozygosity (CH) in association with CHD using our existing GWAS data including 2265 individuals (957 CHD cases and 1308 controls). CollapsABEL was used to iteratively test the association between the CH genotype and the CHD phenotype in a sliding window manner. We highlighted 17 genetic loci showing suggestive CH-like associations with CHD (P < 5 × 10^-8 ), among which 4 genetic loci had expression quantitative trait loci (eQTL) effects in blood (P_eQTL  < 0.01). After conditional association analysis, each loci had only 1 independently effective signal reaching the significance threshold (rs2071477/rs3129299 at 6p21.32, P = 2.47 × 10^-10 ; rs10773097/rs2880921 at 12q24.31, P = 3.30 × 10^-8 ; rs73032040/rs7259476 at 19q13.11, P = 1.14 × 10^-8 ; rs10416386/rs4239517 at 19q13.31, P = 1.15 × 10^-9 ), together explained 7.83% of the CHD variance. Among these 4 associated loci, outstanding candidates for CHD-associated genes included UBC, CFM2, ZNF302, LYPD3 and CADM4. Although replication studies with larger sample size are warranted, the first CH GWAS of CHD may extend our current knowledge of the genetic contributions to CHD in the Han Chinese population.

Cell-surface marker discovery for lung cancer

Lung cancer is the leading cause of cancer deaths in the United States. Novel lung cancer targeted therapeutic and molecular imaging agents are needed to improve outcomes and enable personalized care. Since these agents typically cannot cross the plasma membrane while carrying cytotoxic payload or imaging contrast, discovery of cell-surface targets is a necessary initial step. Herein, we report the discovery and characterization of lung cancer cell-surface markers for use in development of targeted agents. To identify putative cell-surface markers, existing microarray gene expression data from patient specimens were analyzed to select markers with differential expression in lung cancer compared to normal lung. Greater than 200 putative cell-surface markers were identified as being overexpressed in lung cancers. Ten cell-surface markers (CA9, CA12, CXorf61, DSG3, FAT2, GPR87, KISS1R, LYPD3, SLC7A11 and TMPRSS4) were selected based on differential mRNA expression in lung tumors vs. non-neoplastic lung samples and other normal tissues, and other considerations involving known biology and targeting moieties. Protein expression was confirmed by immunohistochemistry (IHC) staining and scoring of patient tumor and normal tissue samples. As further validation, marker expression was determined in lung cancer cell lines using microarray data and Kaplan–Meier survival analyses were performed for each of the markers using patient clinical data. High expression for six of the markers (CA9, CA12, CXorf61, GPR87, LYPD3, and SLC7A11) was significantly associated with worse survival. These markers should be useful for the development of novel targeted imaging probes or therapeutics for use in personalized care of lung cancer patients.

Expression of C4.4A is a potential independent prognostic factor for patients with gastric cancer

C4.4A, a metastasis-associated gene, encodes a glycolipid-anchored membrane protein which is overexpressed in several human malignancies. However, there are few data available on C4.4A expression and its relationship with progression in gastric cancer. Our study was designed to explore the expression of C4.4A in gastric cancer and to correlate it with clinical outcome. C4.4A expression was studied by quantitative real-time RT-PCR and immunohistochemistry for assessment of correlations with clinicopathological factors. C4.4A mRNA expression was significantly up-regulated in gastric cancer as compared with noncancerous tissue (p<0.05)., being observed in 107 (88.4%) of the 121 gastric cancer cases by immunohistochemistry. We found that the expression of C4.4A mRNA was correlated with size of the tumor, depth of invasion, lymph node metastasis, distant metastasis and TNM stage. Moreover, patients with overexpression of C4.4A has a significantly worse survival (p<0.05). Further multivariable analysis indicated that the expression of C4.4A was an independent prognostic indicator for gastric cancer (p<0.05). In conclusion, overexpression of C4.4A correlates with metastatic potential of gastric cancer and C4.4A could be a novel independent prognostic marker for predicting outcome.

New Blocking Antibodies against Novel AGR2-C4.4A Pathway Reduce Growth and Metastasis of Pancreatic Tumors and Increase Survival in Mice

Anterior gradient 2 (AGR2) promotes cancer growth, metastasis, and resistance to therapy via unknown mechanisms. We investigated the effects of extracellular AGR2 signaling through the orphan glycosylphosphatidylinositol-linked receptor C4.4A in pancreatic ductal adenocarcinoma (PDAC). Proliferation, migration, invasion, and apoptosis were measured using colorimetric, Boyden chamber, and FACS analyses. We developed blocking mAbs against AGR2 and C4.4A and tested their effects, along with siRNAs, on cancer cell functions and on orthotopic tumors in nude mice. Extracellular AGR2 stimulated proliferation, migration, invasion, and chemoresistance of PDAC cell lines. AGR2 interacted with C4.4A in cell lysates and mixtures of recombinant proteins. Knockdown of C4.4A reduced migration and resistance to gemcitabine. PDAC tissues, but not adjacent healthy pancreatic tissues, expressed high levels of AGR2 and C4.4A. AGR2 signaling through C4.4A required laminins 1 or 5 and integrin β1. Administration of antibodies against AGR2 and C4.4A reduced growth and metastasis and caused regression of aggressive xenograft tumors, leading to increased survival of mice. These data support a model in which AGR2 binds and signals via C4.4A in an autocrine loop and promotes the growth of pancreas tumors in mice. Blocking mAbs against AGR2 and C4.4A may have therapeutic potential against PDAC.

Expression of the Ly6/uPAR-domain proteins C4.4A and Haldisin in non-invasive and invasive skin lesions

C4.4A and Haldisin belong to the Ly6/uPAR/α-neurotoxin protein domain family. They exhibit highly regulated expression profiles in normal epidermis, where they are confined to early (C4.4A) and late (Haldisin) squamous differentiation. We have now explored if dysregulated expressions occur in non-invasive and invasive skin lesions. In non-invasive lesions, their expression signatures were largely maintained as defined by that of normal epidermis. The scenario was, however, markedly different in the progression towards invasive squamous cell carcinomas. In its non-invasive stage (carcinoma in situ), a pronounced attenuation of C4.4A expression was observed, but upon transition to malignant invasive squamous cell carcinomas, the invasive fronts regained high expression of C4.4A. A similar progression was observed for the early stages of benign infiltrating keratoacanthomas. Interestingly, this transition was accompanied by a shift in the predominant association of C4.4A expression with CK1/10 in the normal epidermis to CK5/14 in the invasive lesions. In contrast, Haldisin expression maintained its confinement to the most-differentiated cells and was hardly expressed in the invasive lesions. Because this altered expression of C4.4A was seen in the invasive front of benign (keratoacanthomas) and malignant (squamous cell carcinomas) neoplasms, we propose that this transition of expression is primarily related to the invasive process.

The metastasis-associated molecule C4.4A promotes tissue invasion and anchorage independence by associating with the alpha6beta4 integrin

C4.4A is a metastasis-associated molecule that functions appear to rely on associated alph6beta4 integrin. To corroborate the impact of the C4.4A-alpha6beta4 integrin association on metastasis formation, C4.4A was knocked-down in a highly metastatic rat pancreatic adenocarcinoma (ASML, ASML-C4.4Akd). Metastasis formation by ASML-C4.4Akd cells after intrafootpad application was strongly retarded in draining nodes and lung colonization was rare. Furthermore, cisplatin treatment significantly prolonged the survival time only of ASML-C4.4Akd-bearing rats. ASML-C4.4Akd cells display reduced migratory activity and impaired matrix protein degradation due to inefficient MMP14 activation; loss of drug-resistance is due to mitigated PI3K/Akt pathway activation. These losses of function rely on the laminin receptor C4.4A recruiting activated alpha6beta4 integrin into rafts, where C4.4A cooperates with alpha6beta4 and via alpha6beta4 with MMP14. Within this raft-located complex, MMP14 provokes focalized matrix degradation and mostly alpha6beta4 integrin promotes BAD phosphorylation and upregulated Bcl2 and BclXl expression. Thus, metastasis-promoting activities of C4.4A are not genuine characteristics of C4.4A. Instead, the raft-located laminin receptor C4.4A recruits alpha6beta4 integrin and supports via the alpha6beta4 integrin MMP14 activation. Thereby C4.4A acts as a linker to facilitate several steps in the metastatic cascade. Taking the restricted C4.4A expression in non-transformed tissue, this knowledge should pave the way toward the use of C4.4A as a therapeutic target.

C4.4A highly expressed in HER2-positive human breast cancers may indicate a good prognosis

BACKGROUND

The aim of our study was to investigate the association of C4.4A expression in breast tumors with both patients' clinicopathological characteristics and outcomes in order to clarify the significance of C4.4A in breast cancer.

METHODS

Primary breast cancer patients (n = 125, stage I-III) who had undergone breast mastectomy or breast-conserving surgery at our hospital between 2005 and 2011 were recruited for this study. Tumor samples were obtained from surgical specimens and expression status of C4.4A, estrogen receptors, progesterone receptors, human epidermal growth factor receptor 2 (HER2) and Ki67 was analyzed immunohistochemically, while HER2 amplification was examined using fluorescence in situ hybridization.

RESULTS

Multivariate analysis showed that HER2 positivity was the only independent predictive factor for C4.4A expression (odds ratio 5.31, 95 % confidence interval 2.04-15.72; P < 0.001). Univariate prognostic analysis of the relationship between C4.4A and disease-free survival showed that survival of patients with C4.4A-positive tumors was longer than that of patients with C4.4A-negative tumors in the HER2-positive subset (P = 0.004) while there was no significant difference in patient outcome according to C4.4A status for total patients (median observation period 37 months, range 1-92 months; P = 0.223).

CONCLUSIONS

We established a positive relationship between C4.4A and HER2 status, suggesting that C4.4A expression may be a prognostic factor for HER2-positive breast cancer patients.

Characterization and function of human Ly-6/uPAR molecules

Human Ly-6/uPAR molecules are a superfamily composed of two subfamilies; one is the membrane bound proteins with a GPI-anchor and the other are secreted proteins without the GPI-anchor. Ly-6/uPAR molecules have remarkable amino acid homology through a distinctive 8-10 cysteine-rich domain that is associated predominantly with O-linked glycans. These molecules are encoded by multiple tightly linked genes located on Chr. 8q23, and have a conserved genomic organization. Ly-6/uPAR molecules have an interesting expression pattern during hematopoiesis and on specific tumors indicating that Ly-6/uPAR molecules are associated with development of the immune system and carcinogenesis. Thus, Ly-6/uPAR molecules are useful antigens for diagnostic and therapeutic targets. This review summarizes our understanding of human Ly-6/ uPAR molecules with regard to molecular structure as well as what is known about their function in normal and malignant tissues and suggest Ly-6/uPAR molecules as target antigens for cancer immunotherapy.

C4.4A expression is associated with a poor prognosis of esophageal squamous cell carcinoma

BACKGROUND

C4.4A is a glycolipid-anchored membrane protein expressed in several human malignancies. We examined clinical relevance of C4.4A expression in 111 esophageal squamous cell carcinoma (ESCC) tissue samples.

METHODS

Anti-human C4.4A antibody that recognizes the glycosylphosphatidyl inositol (GPI) anchor signaling sequence (C4.4A-GPI Ab) and anti-human C4.4A-119 polyclonal antibody (C4.4A-119 Ab) were used for immunohistochemistry and Western blot testing.

RESULTS

Both antibodies detected the C4.4A protein expression at the parabasal layer of normal epithelium of the esophagus. In tumor tissues, the C4.4A protein was detected in 66 (59.5 %) and 95 (85.6 %) of 111 ESCCs by the C4.4A-GPI Ab and the C4.4A-119 Ab, respectively. The C4.4A-GPI Ab mainly detected membranous C4.4A expression (83.3 %, 55 of 66 positive cases), while the C4.4A-119 Ab exclusively detected cytoplasmic C4.4A expression (100 %, 73 cytoplasm alone and 22 cytoplasm plus membrane in 95 positive cases). Western blot analysis indicated that normal epithelium expressed the band of C4.4A at 70 kDa, whereas the tumor tissues displayed the band at the lower molecular weight. Survival analysis indicated that the C4.4A-positive ESCCs had significantly worse 5-year overall survival than the C4.4A-negative ESCC samples (P = 0.021) when using the C4.4A-GPI Ab, but not when using the C4.4A-119 Ab. This difference was most evident with membranous expression of C4.4A (P = 0.005).

CONCLUSIONS

C4.4A expression was associated with a poor prognosis of ESCC when the GPI-related antibody was used. On the other hand, the C4.4A-119 Ab may be a useful diagnostic tool for ESCC because of its high detection rate.

C4.4A is associated with tumor budding and epithelial-mesenchymal transition of colorectal cancer

C4.4A is a glycolipid-anchored membrane protein expressed in several human malignancies. The aim of this study was to explore the association between C4.4A expression at the invasion front of colorectal cancer (CRC) and tumor budding, a putative hallmark of cell invasion of CRC. Advanced CRCs (T2-4, n = 126) had a budding count of 3.66 ± 5.66, which was significantly higher than that of T1 early CRCs (1.75 ± 2.78, n = 87). C4.4A-positive CRC specimens showed a larger budding cell number than C4.4A-negative CRC specimens in T1 CRCs, and especially advanced CRCs (9.45 ± 5.83 vs 1.60 ± 3.93). Furthermore, we found a correlation between the percentage of C4.4A-positive cases and budding count in advanced CRC. Multivariate analysis for patients' survival showed that C4.4A was superior to tumor budding as a prognostic factor. With siRNA treatment, C4.4A levels were associated with cell invasion, but not with proliferation, in HCT116 and DLD1 cell lines. An immunohistochemical study in a subset of CRCs showed no relationship between C4.4A and Ki-67 proliferation marker. In vitro assays using HCT116 indicated that C4.4A levels correlated well with epithelial-mesenchymal transition (EMT) with regard to cell morphology and alterations of EMT markers including E-cadherin, vimentin, and partially N-cadherin. We also found that C4.4A expression was significantly associated with loss of E-cadherin and gain of β-catenin in clinical CRC tissue samples. These findings suggest that a tight association between C4.4A and tumor budding may, in part, be due to C4.4A promoting EMT at the invasive front of CRC.

Membrane-bound and exosomal metastasis-associated C4.4A promotes migration by associating with the α(6)β(4) integrin and MT1-MMP

Metastasis-associated C4.4A, which becomes upregulated during wound healing and, in some tumors, during tumor progression, is known to be frequently associated with hypoxia. With the function of C4.4A still unknown, we explored the impact of hypoxia on C4.4A expression and functional activity. Metastatic rat and human tumor lines upregulate C4.4A expression when cultured in the presence of CoCl(2). Although hypoxia-inducible factor 1α (HIF-1α) becomes upregulated concomitantly, HIF-1α did not induce C4.4A transcription. Instead, hypoxia-induced C4.4A up-regulation promoted in vivo and in vitro wound healing, where increased migration on the C4.4A ligands laminin-111 and -332 was observed after a transient period of pronounced binding. Increased migration was accompanied by C4.4A associating with α(6)β(4), MT1-MMP1, and TACE and by laminin fragmentation. Hypoxia also promoted the release of C4.4A in exosomes and TACE-mediated C4.4A shedding. The association of C4.4A with α(6)β(4) and MT1-MMP1 was maintained in exosomes and exosomal α(6)β(4)- and MT1-MMP1-associated C4.4A but not shed C4.4A sufficient for laminin degradation. Hypoxia-induced recruitment of α(6)β(4) toward raft-located C4.4A, MT1-MMP, and TACE allows for a shift from adhesion to motility, which is supported by laminin degradation. These findings provide the first explanation for the C4.4A contribution to wound healing and metastasis.

Altered LKB1/CREB-regulated transcription co-activator (CRTC) signaling axis promotes esophageal cancer cell migration and invasion

LKB1 is a tumor susceptibility gene for the Peutz-Jeghers cancer syndrome and is a target for mutational inactivation in sporadic human malignancies. LKB1 encodes a serine/threonine kinase that has critical roles in cell growth, polarity and metabolism. A novel and important function of LKB1 is its ability to regulate the phosphorylation of CREB-regulated transcription co-activators (CRTCs) whose aberrant activation is linked with oncogenic activities. However, the roles and mechanisms of LKB1 and CRTC in the pathogenesis of esophageal cancer have not been previously investigated. In this study, we observed altered LKB1-CRTC signaling in a subset of human esophageal cancer cell lines and patient samples. LKB1 negatively regulates esophageal cancer cell migration and invasion in vitro. Mechanistically, we determined that CRTC signaling becomes activated because of LKB1 loss, which results in the transcriptional activation of specific downstream targets including LYPD3, a critical mediator for LKB1 loss-of-function. Our data indicate that de-regulated LKB1-CRTC signaling might represent a crucial mechanism for esophageal cancer progression.

Expression of C4.4A, a structural uPAR homolog, reflects squamous epithelial differentiation in the adult mouse and during embryogenesis

The glycosylphosphatidylinositol (GPI)-anchored C4.4A was originally identified as a metastasis-associated protein by differential screening of rat pancreatic carcinoma cell lines. C4.4A is accordingly expressed in various human carcinoma lesions. Although C4.4A is a structural homolog of the urokinase receptor (uPAR), which is implicated in cancer invasion and metastasis, no function has so far been assigned to C4.4A. To assist future studies on its function in both physiological and pathophysiological conditions, the present study provide a global survey on C4.4A expression in the normal mouse by a comprehensive immunohistochemical mapping. This task was accomplished by staining paraffin-embedded tissues with a specific rabbit polyclonal anti-C4.4A antibody. In the adult mouse, C4.4A was predominantly expressed in the suprabasal layers of the squamous epithelia of the oral cavity, esophagus, non-glandular portion of the rodent stomach, anus, vagina, cornea, and skin. This epithelial confinement was particularly evident from the abrupt termination of C4.4A expression at the squamo-columnar transition zones found at the ano-rectal and utero-vaginal junctions, for example. During mouse embryogenesis, C4.4A expression first appears in the developing squamous epithelium at embryonic day 13.5. This anatomical location of C4.4A is thus concordant with a possible functional role in early differentiation of stratified squamous epithelia.

Expression of C4.4A at the invasive front is a novel prognostic marker for disease recurrence of colorectal cancer

Metastasis-associated gene C4.4A is a glycolipid-anchored membrane protein expressed in several human malignancies. The aim of this study was to explore the expression and clinical relevance of C4.4A in colorectal cancer. By quantitative RT-PCR, 154 colorectal cancer tissues were examined for C4.4A mRNA. We examined 132 colorectal cancer tissues by immunohistochemistry using a new polyclonal antibody that recognizes the C4.4A protein C-terminus containing the glycosylphosphatidyl-inositol anchor signaling sequence. A significant difference in 5-year overall survival was found between samples with high and low expression of C4.4A mRNA (P = 0.0005). Immunohistochemistry showed strong membranous staining of C4.4A at the invasive front of colorectal cancer tumors and at the frontier of metastatic lesions to lymph node and lung. The membranous staining with enhanced intensity at the invasive front of the primary colorectal cancer (Type A: 34/132, 25.6%) was associated with depth of invasion (P = 0.033) and venous invasion (P = 0.003), and was a significant independent prognostic factor (5-year overall survival in the entire series [n = 132; P = 0.004] and disease-free survival in stage II and III colorectal cancers [n = 82; P = 0.003]). Moreover, Type A C4.4A expression was linked to shorter liver metastasis-free survival rate, lung metastasis-free survival rate, or hematogenous metastasis-free survival (P = 0.0279, P = 0.0061, and P = 0.0006, respectively). Our data indicate that expression of the C4.4A protein at the invasive front acts as a novel prognostic marker in colorectal cancer, possibly through invasion-related mechanisms.

Metastasis-associated C4.4A, a GPI-anchored protein cleaved by ADAM10 and ADAM17

Metalloproteases play a complex role in tumor progression. While the activity of some ADAM, ADAMTS and matrix metalloproteases (MMPs) seems to be protumorigenic, the activity of others seems to prevent tumor progression. The identification of the array of substrates of a given metalloprotease (degradome) seems an adequate approach to predict the effect of the inhibition of a metalloprotease in tumors. Here, we present the proteomic identification of a novel substrate for ADAM10 and -17. We used SILAC (Stable Isotope Labeling by Amino acids in Cell culture), a proteomic technique based on the differential metabolic labeling of cells in different conditions. This was applied to MCF7 cells derived from an invasive mammary tumor, and the same cells expressing shRNAs that knock down ADAM10 or -17. Following this approach, we have identified C4.4A as a substrate to both metalloproteases. Since C4.4A is likely involved in tumor invasion, these results indicate that the cleavage of C4.4A by ADAM10 and ADAM17 contributes to tumor progression.

Altered expression of the urokinase receptor homologue, C4.4A, in invasive areas of human esophageal squamous cell carcinoma

C4.4A is a glycolipid-anchored membrane protein with structural homology to the urokinase-type plasminogen activator receptor (uPAR). Although C4.4A was identified as a metastasis-associated protein little is known about its actual expression and possible function in malignant disease. In the present study, we have therefore analyzed the expression of C4.4A in 14 esophageal squamous cell carcinomas (ESCC). Normal squamous esophageal epithelium shows a strong cell surface associated C4.4A expression in the suprabasal layers, whereas basal cells are negative. Upon transition to dysplasia and carcinoma in situ the expression of C4.4A is abruptly and coordinately weakened. Double immunofluorescence staining of normal and dysplastic tissue showed that C4.4A colocalizes with the epithelial cell surface marker E-cadherin in the suprabasal cells and has a complementary expression pattern compared to the proliferation marker Ki-67. A prominent, but frequently intracellular, C4.4A expression reappeared in tumor cells located at the invasive front and local lymph node metastases. Because C4.4A was reported previously to be a putative laminin-5 (LN5) ligand, and both proteins are expressed by invasive tumor cells, we analyzed the possible coexpression of C4.4A and the gamma 2-chain of LN5 (LN5-gamma 2). Although these proteins are indeed expressed by either neighboring cancer cells or in a few cases even coexpressed by the same cells in the tumor front and metastases, we found no evidence for a general colocalization in the extracellular compartment by confocal microscopy. In conclusion, C4.4A is expressed during invasion and metastasis of human ESCC and may thus provide a new histological marker in this disease.

C4.4A as a candidate marker in the diagnosis of colorectal cancer

C4.4A is a member of the Ly-6 family with restricted expression in non-transformed tissues. C4.4A expression in human cancer has rarely been evaluated. Thus, it became important to explore C4.4A protein expression in human tumour tissue to obtain an estimate on the frequency of expression and the correlation with tumour progression, the study focusing on colorectal cancer. The analysis of C4.4A in human tumour lines by western blot and immunoprecipitation using polyclonal rabbit antibodies that recognize different C4.4A epitopes revealed C4.4A oligomer and heavily glycosylated C4.4A isoform expression that, in some instances, inhibited antibody binding and interaction with the C4.4A ligand galectin-3. In addition, tumour cell lines released C4.4A by vesicle shedding and proteolytic cleavage. C4.4A was expressed in over 80% of primary colorectal cancer and liver metastasis with negligible expression in adjacent colonic mucosa, inflamed colonic tissue and liver. This compares well with EpCAM and CO-029 expression in over 90% of colorectal cancer. C4.4A expression was only observed in about 50% of pancreatic cancer and renal cell carcinoma. By de novo expression in colonic cancer tissue, we consider C4.4A as a candidate diagnostic marker in colorectal cancer, which possibly can be detected in body fluids.

Tumour cell expression of C4.4A, a structural homologue of the urokinase receptor, correlates with poor prognosis in non-small cell lung cancer

PURPOSE

C4.4A expression has been implicated in human cancer progression. This protein is a structural homologue of the urokinase receptor, uPAR, which constitutes a well-established prognostic marker in various human cancers. Nonetheless, little is known about the prognostic significance of C4.4A expression. In the present study, we therefore explored the possible association between C4.4A expression and prognosis in patients with non-small cell lung cancer (NSCLC).

EXPERIMENTAL DESIGN

Tissue sections from 108 NSCLC patients were subjected to immunohistochemical staining using a polyclonal antibody that specifically recognises human C4.4A. Staining frequency and intensity was scored semiquantitatively and grouped into cancers with high and low expression of C4.4A. Kaplan-Meier survival curves were generated to evaluate the significance of C4.4A expression in prognosis of NSCLC patients.

RESULTS

High C4.4A expression was observed in 42% of the NSCLC specimens analysed, and this correlates with overall survival (p = 0.012). A remarkably strong correlation was noted between high expression of C4.4A in pulmonary adenocarcinoma and survival (p < 0.0001). Multivariate Cox regression analysis shows that high C4.4A expression is an independent predictor of poor disease outcome in NSCLC (risk ratio, 1.42; 95% confidence interval, 1.09-1.86; p = 0.009). Although histological type is not a predictor of outcome in NSCLC, high C4.4A expression in adenocarcinoma is nevertheless a very strong predictor of poor disease outcome (risk ratio, 1.62; 95% confidence interval, 1.24-2.09; p = 0.001).

CONCLUSIONS

High tumour cell C4.4A expression is associated with shorter survival for NSCLC patients. Patients with pulmonary adenocarcinoma have a particularly poor prognosis if this histological type is combined with high tumour cell C4.4A expression.

CEBPbeta, JunD and c-Jun contribute to the transcriptional activation of the metastasis-associated C4.4A gene

The glycosylphosphatidylinositol-anchored molecule C4.4A, which shares structural features with uPAR, is frequently expressed on carcinomas with upregulated expression during tumor progression. Moreover, rare expression on nontransformed epithelial cells is strongly increased during tissue remodeling, e.g., during wound healing. This strictly regulated expression prompted us to define transcriptional activation of the C4.4A gene. C4.4A transcription was analyzed in 2 syngenic rat tumor cell lines with low or high metastatic potential, respectively. Though genomic C4.4A DNA was present in both lines, C4.4A mRNA and transcription of a reporter construct containing the C4.4A promoter was only observed in the metastasizing subline. Deletions and point mutations in the C4.4A promoter-driven reporter construct revealed that activation of the TATA-less, GC-rich core promoter (-1 to -50 bp) does not suffice to initiate transcription that requires coactivation of a proximal response element (-71 to -88 bp) and can be further increased by more distal response elements (-89 to -133 bp). Mobility-shift and cotransfection studies showed that Sp3 binding enhances C4.4A transcription, whereas potential Sp1 binding sites were ineffective. C4.4A transcription essentially requires C/EBPbeta binding to a TRE/CCAAT composite element (-71 to -88 bp) as measured by ChIP assay. C4.4A transcription is strikingly enhanced by cotransfection with JunD or c-Jun, such that C4.4A is most strongly transcribed even in the C4.4A-negative tumor cell line after cotransfection with C/EBPbeta plus JunD or c-Jun. Thus, upregulation of C/EBPbeta during tumor progression and wound repair may well provide a sufficient trigger for transcription of the C4.4A gene.

Ly6 family member C4.4A binds laminins 1 and 5, associates with galectin-3 and supports cell migration

C4.4A is a member of the Ly6 family, with low homology to uPAR. It has been detected mainly on metastasizing carcinoma cells and proposed to be involved in wound healing. So far, C4.4A has been observed as an orphan receptor, and its functional activity has not been explored. Using recombinant rat C4.4A (rrC4.4A) made in a eukaryotic expression system, we demonstrate by immunohistology that C4.4A ligands are strongly expressed in tissues adjacent to squamous epithelia of, e.g., tongue and esophagus, the expression pattern partly overlapping with laminin (LN) and complementing the C4.4A expression that is found predominantly on the basal layers of squamous epithelium. ELISA screening of several components of the extracellular matrix revealed selective binding of rrC4.4A to LN1 and LN5 and that transfection of the BSp73AS tumor line with C4.4A cDNA (BSp73AS-1B1) promoted LN1 and LN5 binding. Binding of BSp73AS-1B1 to LN5 and, less markedly, LN1 induced spreading, lamellipodia formation and migration. C4.4A also associates with galectin-3 in nontransformed tissues and tumor lines. There is evidence that the association of C4.4A with galectin-3 influences LN adhesion. C4.4A was described originally as a metastasis-associated molecule. Our findings that LN1 and LN5 are C4.4A ligands, that galectin-3 associates with C4.4A and that C4.4A ligand binding confers a migratory phenotype are well in line with the supposed metastasis association.

Structural analysis and tissue localization of human C4.4A: a protein homologue of the urokinase receptor

C4.4A, a structural homologue of the urokinase-type plasminogen activator receptor (uPAR), was originally identified as a metastasis-associated membrane protein, but little is known about its structural and functional properties. Therefore, we expressed, purified and characterized a soluble truncated form of human C4.4A, and used this protein to produce specific polyclonal anti-C4.4A antibodies. By immunohistochemistry we observed a pronounced surface staining for C4.4A in suprabasal keratinocytes of chronic human wounds and found C4.4A expression markedly upregulated in migrating keratinocytes during re-epithelisation of incisional skin wounds. Phorbol-ester-induced hyperplasia of mouse skin is also accompanied by a significant induction of C4.4A expression in the multilayered, suprabasal keratinocytes. C4.4A contains two Ly-6 (leucocyte antigen 6)/uPAR/alpha-neurotoxin modules. Our recombinant human C4.4A is extensively modified by post-translational glycosylation, which include 5-6 N-linked carbohydrates primarily located in or close to its second Ly-6/uPAR/alpha-neurotoxin module and approximately 15 O-linked carbohydrates clustered in a Ser/Thr/Pro-rich region at the C-terminus. A highly protease-sensitive region (Tyr200-Arg204) is located between these two clusters of N- and O-linked carbohydrates. The natural, glycolipid-anchored C4.4A from amnion membranes of human term placenta exhibits similar properties. Using recombinant, soluble C4.4A or MCF 7 cells, which express significant amounts of GPI-anchored C4.4A, we find no evidence for an interaction between C4.4A and uPA, a property suggested previously for rat C4.4A. Collectively these data indicate that C4.4A, although being a structural homologue of uPAR, is unlikely to have a functional overlap with uPAR.