The biology of the 17-1A antigen (Ep-CAM)

The tumour-associated antigen EpCAM upregulates the fatty acid binding protein E-FABP

The epithelial cell adhesion molecule, EpCAM, is a transmembrane glycoprotein associated with both benign and malignant proliferation. In cancer cells, expression levels of this tumour-associated antigen correlate positively with the grade of dysplasia and are also a negative prognostic factor for breast cancer patients. De novo expression of EpCAM resulted in the rapid upregulation of the proto-oncogene c-Myc along with enhanced cell proliferation and metabolism. Here, we analyzed the effects of EpCAM onto the proteome of epithelial cells. The epidermal fatty acid binding protein, E-FABP, was identified as a new EpCAM-regulated protein. E-FABP is a major target of c-Myc and was rapidly upregulated upon induction of EpCAM. Additionally, E-FABP levels correlated with the amount of EpCAM in permanent squamous cell carcinoma lines and in vivo in primary head and neck carcinomas. Taken together, these results provide further evidence for the direct involvement of EpCAM in signalling processes, gene regulation, and cellular metabolism supporting its important role in tumour biology.

Ex vivo evaluation of anti-EpCAM immunocytokine huKS-IL2 in ovarian cancer

Despite encouraging responses to treatment, 70% to 80% of women with ovarian cancer will recur due to subclinical residual disease. One experimental agent that merits testing in this setting is the immunocytokine huKS-IL2. Immunocytokines are fusion proteins consisting of a humanized monoclonal antibody linked to IL-2 (or other cytokines). The humanized monoclonal antibody (mAb) huKS, which recognizes the epithelial cell adhesion molecule (EpCAM), has been used to construct the immunocytokine huKS-IL2. To determine the potential therapeutic use of huKS-IL2 in ovarian cancer, the authors evaluated the expression of EpCAM in these cancers and investigated the effects of huKS-IL2 on peritoneal white blood cells and peripheral blood mononuclear cells from women with ovarian cancer. EpCAM expression was determined by immunohistochemistry using both huKS-IL2 and the parent KS1/4 antibody. Ascites fluid was collected and the cellular fraction cultured with or without huKS-IL2 to evaluate the cellular content and potential anti-tumor effects of the peritoneal effector cells (PECs). Peritoneal cells were incubated with FITC-conjugated KS antibody to determine the relative amount of EpCAM-positive cells. Nonadherent cells were analyzed by flow cytometry for hematopoietic origin with CD45 mAb and for CD69 expression as an indication of immune cell activation. EpCAM-positive NIH:OVCAR-3 cells were radiolabeled as targets in a chromium release assay with either PECs or PBMCs as effector cells in the presence or absence of 0.25 mcg/mL huKS-IL2. Differences between treatments were determined by t test. Thirty-two of thirty-three (97%) ovarian cancers were found to express EpCAM via immunohistochemistry. Eleven cases were stained using both KS1/4 and huKS-IL2, and identical patterns of staining were seen. All ascites samples tested had EpCAM-positive cells by flow cytometry. The mean fluorescence intensity of CD69 expression on peritoneal WBCs was increased from 20.7 to 43.9 as a result of culturing with huKS-IL2, indicating effector cell activation. In chromium release assays, KS-IL2 facilitated cell lysis of NIH:OVCAR-3 by PBMCs from both healthy controls and patients with ovarian cancer. PECs from all cases tested showed significant cell lysis induced by huKS-IL2 compared with untreated control cultures. Based on these findings, huKS-IL2 warrants further investigation as a potential immunotherapy for patients with epithelial ovarian cancer, preferably in a minimal disease setting as seen after complete cytoreductive surgery, after a complete clinical response to primary therapy, or when elevated CA-125 levels predict recurrent disease prior to clinical relapse.

Biological role of Ep-CAM in the physical interaction between epithelial cells and lymphocytes in intestinal epithelium

The mucosal epithelium including intestinal epithelial cells (IECs) and intraepithelial lymphocytes (IELs) provide a first line of defense in the gastrointestinal tract. However, limited information is currently available concerning the nature of the physical interaction molecule that interconnects IECs and IELs. Among the several monoclonal antibodies (mAbs) generated by immunizing porcine IECs, mAb (5-15-1) was shown to strongly react with IELs in addition to IECs. MALDI-TOF-MS and tandem MS analysis suggested that the antigen belongs to a family of human homophilic epithelial cell adhesion molecule (Ep-CAM). The amino acid sequence of porcine Ep-CAM showed 82.8%, 78.1%, and 76.8% homology compared to human, mouse, and rat Ep-CAM. Moreover, 5-15-1 specifically reacted with transfectant of porcine Ep-CAM. These data suggest that the Ep-CAM may act as a physical homophilic interaction molecule between IELs and IECs at the mucosal epithelium for providing immunological barrier as a first line of defense against mucosal infection.

Epithelial cell adhesion molecule (KSA) expression: pathobiology and its role as an independent predictor of survival in renal cell carcinoma

PURPOSE

Epithelial cell adhesion molecule (EpCAM) is a widely expressed adhesion molecule in epithelial cancers. The purpose of this study is to determine the protein expression patterns of EpCAM in renal cell carcinoma (RCC) using tissue arrays linked to a clinicopathological database to evaluate both its predictive power in patient stratification and its suitability as a potential target for immunotherapeutic treatment strategies.

EXPERIMENTAL DESIGN

The University of California, Los Angeles kidney cancer tissue microarray contains specimens from 417 patients treated with nephrectomy. EpCAM protein expression in tumors and matched morphologically normal renal tissues was evaluated using anti-EpCAM immunohistochemistry. The resultant expression reactivity was correlated with clinicopathological variables.

RESULTS

EpCAM is consistently expressed in the distal nephron on normal renal epithelium. Clear cell RCCs show minimal and infrequent EpCAM expression, whereas chromophobe and collecting duct RCCs both demonstrate intense and frequent expression. Of 318 clear cell carcinomas used in the analysis, 10% were EpCAM positive in > or = 50% of cells, and 8% of patients would be considered candidates for EpCAM-based therapy, based on high expression [> or = moderate intensity and frequent (> or = 50%) expression] and the need for systemic treatment. EpCAM expression was an independent prognostic factor for improved disease-specific survival, with a multivariate hazard ratio of 0.63 (P = 0.017; 95% confidence interval, 0.43-0.92).

CONCLUSIONS

EpCAM is a novel prognostic molecular marker in RCC patients, and its positive expression is an independent predictor associated with improved survival. However, high expression in morphologically normal renal tissues and minimal or absent expression in clear cell carcinomas will likely limit the utility of this epithelial marker in targeted treatments of this most common RCC type.

ING-1, a Monoclonal Antibody Targeting Ep-CAM in Patients with Advanced Adenocarcinomas

PURPOSE

To determine the feasibility of administration, safety, toxicity, immunogenicity, pharmacokinetics, maximum tolerated dose, and biodistribution of ING-1, a high-affinity, Human-Engineered monoclonal antibody (heMAb) to the Mr 40,000 epithelial cell adhesion molecule Ep-CAM, in patients with advanced adenocarcinomas.

EXPERIMENTAL DESIGN

ING-1 was initially administered to patients as a 1-hour intravenous infusion every 3 weeks. Toxicity and pharmacokinetic data led to the evaluation of a weekly schedule. The distribution of iodine-131 (131I)-labeled ING-1 was studied.

RESULTS

Twenty-five patients received 82 courses of ING-1. Minimal toxicity was initially observed at the 0.03-, 0.10-, and 0.30-mg/kg dose levels. A patient dosed at 1.0 mg/kg developed acute pancreatitis with severe abdominal pain, nausea, and vomiting. A patient dosed at 0.3 mg/kg had an asymptomatic amylase and lipase elevation to 502 units/L and 1,627 units/L, respectively. Both patients made uncomplicated recoveries. No other dose-limiting toxicities were observed. Regardless of dose, the volume of distribution (mean +/- SEM) was 46.6 +/- 1.6 mL/kg. ING-1 clearance decreased with increasing dose. To minimize toxicity and increase dose intensity, we then administered ING-1 weekly. No significant toxicity was observed in 7 patients dosed at 0.1 mg/kg. Studies of 131I-labeled ING-1 biodistribution showed radiolocalization to colorectal and prostate cancers. A patient with colorectal cancer had an 80% decrement in the levels of carcinoembryonic antigen.

CONCLUSION

The recommended dose for ING-1 is 0.10 mg/kg by intravenous infusion weekly. The absence of severe toxicity at this dose, low immunogenicity, and preliminary evidence of ING-1 tumor localization and antitumor efficacy support the further clinical development of this antibody to treat Ep-CAM-positive malignant diseases.

Epstein-Barr virus infection in ex vivo tonsil epithelial cell cultures of asymptomatic carriers

Epstein-Barr virus (EBV) is found frequently in certain epithelial pathologies, such as nasopharyngeal carcinoma and oral hairy leukoplakia, indicating that the virus can infect epithelial cells in vivo. Recent studies of cell lines imply that epithelial cells may also play a role in persistent EBV infection in vivo. In this report, we show the establishment and characterization of an ex vivo culture model of tonsil epithelial cells, a likely site for EBV infection in vivo. Primary epithelial-cell cultures, generated from tonsil explants, contained a heterogeneous mixture of cells with an ongoing process of differentiation. Keratin expression profiles were consistent with the presence of cells from both surface and crypt epithelia. A small subset of cells could be latently infected by coculture with EBV-releasing cell lines, but not with cell-free virus. We also detected viral-DNA, -mRNA, and -protein expression in cultures from EBV-positive tonsil donors prior to in vitro infection. We conclude that these cells were either already infected at the time of explantation or soon after through cell-to-cell contact with B cells replicating EBV in the explant. Taken together, these findings suggest that the tonsil epithelium of asymptomatic virus carriers is able to sustain EBV infection in vivo. This provides an explanation for the presence of EBV in naso- and oropharyngeal pathologies and is consistent with epithelial cells playing a role in the egress of EBV during persistent infection.

EpCAM is overexpressed in breast cancer and is a potential target for breast cancer gene therapy

EpCAM (epithelial cell adhesion molecule) is a cell surface molecule that is known to be highly expressed in colon and other epithelial carcinomas. EpCAM is involved in cell-to-cell adhesion and has been the target of antibody therapy in several clinical trials. To assess the value of EpCAM as a novel target for breast cancer gene therapy, we performed real-time reverse transcription-PCR to quantify the level of EpCAM mRNA expression in normal breast tissue and primary and metastatic breast cancers. We found that EpCAM is overexpressed 100- to 1000-fold in primary and metastatic breast cancer. Silencing EpCAM gene expression with EpCAM short interfering RNA (siRNA) resulted in a 35-80% decrease in the rate of cell proliferation in four different breast cancer cell lines. EpCAM siRNA treatment decreased cell migration by 91.8% and cell invasion by 96.4% in the breast cancer cell line MDA-MB-231 in vitro. EpCAM siRNA treatment was also associated with an increase in the detergent-insoluble protein fraction of E-cadherin, alpha-catenin, and beta-catenin, consistent with the known biology of EpCAM as a regulator of cell adhesion. Our hypothesis is that modulation of EpCAM expression can affect cell migration, invasion, and proliferation by enhancing E-cadherin-mediated cell-to-cell adhesion. These data provide compelling evidence that EpCAM is a potential novel target for breast cancer gene therapy and offer insights into the mechanisms associated with EpCAM gene silencing.

The carcinoma-associated antigen EpCAM upregulates c-myc and induces cell proliferation

Epithelial cell adhesion molecule (EpCAM) is a membrane glycoprotein expressed on adenomatous and simple epithelia, where it is involved in homophilic adhesion at the basolateral membrane. Carcinomas strongly overexpress EpCAM through an, as yet, unknown mechanism. Interestingly, otherwise EpCAM-negative squamous epithelia are seen to express EpCAM concomitant with their transformation and de-differentiation. The amount of EpCAM and the number of expressing cells both increase with the grade of dysplasia. Despite an important amount of data correlating the expression of EpCAM with cellular proliferation and de-differentiation, such as the coexpression with Ki-67, a marker for proliferation, it is unknown whether EpCAM may directly contribute to carcinogenesis. Here, we show that EpCAM has a direct impact on cell cycle and proliferation, and the ability to rapidly upregulate the proto-oncogene c-myc and cyclin A/E. Human epithelial 293 cells as well as murine NIH3T3 fibroblasts expressing EpCAM had a decreased requirement for growth factors, enhanced metabolic activity and colony formation capacity. Importantly, the inhibition of EpCAM expression with antisense mRNA led to a strong decrease in proliferation and metabolism in human carcinoma cells. Moreover, domain swapping experiments demonstrated that the intracellular part of EpCAM is necessary and sufficient to transduce the effects described. Thus, the data presented here highlight the role of EpCAM, demonstrating for the first time a direct link to cell cycle and proliferation.

A relevant immunomagnetic assay to detect and characterize epithelial cell adhesion molecule-positive cells in bone marrow from patients with breast carcinoma: immunomagnetic purification of micrometastases

BACKGROUND

The efficient detection and characterization of micrometastatic cells in the bone marrow of patients with breast carcinoma are of prognostic and therapeutic importance. The technique used must overcome the challenges that result from the small number of target cells (1 per 1 million hematopoietic cells) and the heterogeneous expression of micrometastatic cell markers. In this study, the authors assessed and improved the current methods for purifying and characterizing rare disseminated carcinoma cells.

METHODS

The authors developed a single-step assay that does not require density-gradient separation. This assay can be performed directly on crude human bone marrow aspirates and is based on the use of immunomagnetic beads coated with an antibody that recognizes an epithelial cell-surface epitope, the epithelial cell adhesion molecule (EpCAM). To determine the specificity of the assay, the authors evaluated bone marrow specimens from 46 control patients.

RESULTS

The novel method was highly reproducible and was capable of detecting as few as 10 carcinoma cells among 50 million hematopoietic cells. The yield was nearly 100%, with only 0.01% nonspecific cell draining. The authors found that 68 +/- 51 cells were trapped per 50 million cells in control crude aspirates and that density-gradient separation increased this number by 2-fold to 29-fold. These trapped cells expressed EpCAM, represented 1.4 x 10(-4) % of the sample, and were characterized as of hematopoietic cell origin (CD45 positive) or progenitor cell origin (CD34 positive).

CONCLUSIONS

The authors developed a highly efficient and reproducible, single-step immunomagnetic assay that may be performed directly on crude human bone marrow aspirates. The authors believe the current study is the first to demonstrate that some rare bone marrow cells (CD45-positive or CD34-positive cells) may express EpCAM and, to some extent, may contaminate the purified micrometastatic cell fraction. Thus, a universal marker for micrometastatic cells remains to be discovered.

Monoclonal antibodies in the treatment of colorectal cancer

Monoclonal antibodies have been developed to target specific proteins involved in the development and progression of cancer. These reagents have the advantage of exquiste specificity, and as currently engineered, low toxicity. The impact monoclonal antibody therapy has recently been demonstrated in colorectal cancer, in which two pathways critical to carcinogenesis have been targeted. The targets are the epidermal growth factor receptor signaling pathway and angiogenesis. Antibodies directed to proteins in both pathways have shown significant activity especially in combination with chemotherapy, and studies in the adjuvant setting are in progress. We review the use of monoclonal antibodies in the treatment of colorectal cancer with particular attention to edrecolomab (Mab 17-1A), bevacizumab (Avastin), cetuximab (IMC-C225), ABX-EGF and EMD 72000. Additional compounds are in earlier stages of development, and the future of this approach in solid tumours is promising.

CD44 variant isoforms associate with tetraspanins and EpCAM

The metastasizing subline of the rat pancreatic adenocarcinoma BSp73 expresses a set of membrane molecules, the combination of which has not been detected on non-metastasizing tumor lines. Hence, it became of interest whether these molecules function independently or may associate and exert specialized functions as membrane complexes. Separation of CD44v4-v7 containing membrane complexes in mild detergent revealed an association with the alpha3 integrin, annexin I, EpCAM, and the tetraspanins D6.1A and CD9. EpCAM and the tetraspanins associate selectively with CD44 variant (CD44v), but not with the CD44 standard (CD44s) isoform. The complexes are found in glycolipid-enriched membrane (GEM) microdomains, which are dissolved by stringent detergents, but the complexes are not destroyed by methyl-beta-cyclodextrin (MbetaCD) treatment, which implies that complex formation does not depend on a lipid-rich microenvironment. However, a complex-associated impact on cell-matrix and cell-cell adhesion as well as on resistance towards apoptosis essentially depended on the location in GEMs. Thus, CD44v-specific functions may well be brought about by complex formation of CD44v with EpCAM, the tetraspanins, and the alpha3 integrin. Because CD44v4-v7-EpCAM complex-specific functions strictly depended on the GEM localization, linker or signal-transducing molecules associating with the complex are likely located in GEMs.

Enrichment methods to detect bone marrow micrometastases in breast carcinoma patients: clinical relevance

Introduction

Improving technologies for the detection and purification of bone marrow (BM) micrometastatic cells in breast cancer patients should lead to earlier prognosis of the risk of relapse and should make it possible to design more appropriate therapies. The technique used has to overcome the challenges resulting from the small number of target cells (one per million hematopoietic cells) and the heterogeneous expression of micrometastatic cell markers. In the present study, we have assessed the clinical relevance of current methods aimed at detecting rare disseminated carcinoma cells.

Methods

BM aspirates from 32 carcinoma patients were screened for the presence of micrometastatic cells positive for epithelial cell adhesion molecule and positive for cytokeratins, using optimized immunodetection methods. A comparison with data obtained for 46 control BM aspirates and a correlation with the clinical status of patients were performed.

Results

We developed a sensitive and efficient immunomagnetic protocol for the enrichment of BM micrometastases. This method was used to divide 32 breast carcinoma patients into three categories according to their epithelial cell adhesion molecule status. These categories were highly correlated with the recently revised American Joint Committee on Cancer staging system for breast cancer, demonstrating the clinical relevance of this simple and reliable immunomagnetic technique. We also evaluated immunocytochemical detection of cytokeratin-positive cells and cytomorphological parameters. Immunocytochemistry-based methods for the detection of BM micrometastases did not provide any information about the clinical status of patients, but helped to refine the immunomagnetic data by confirming the presence of micrometastases in some cases. We also tested a new density gradient centrifugation system, able to enrich the tumor fraction of BM specimens by twofold to threefold as compared with standard Ficoll methods.

Conclusion

These improved methods for the detection of micrometastatic cells in patient BM should help clinicians to predict the clinical status of breast cancer patients at the time of surgery or treatment.

Use of the EGP-2/Ep-CAM promoter for targeted expression of heterologous genes in carcinoma derived cell lines

EGP-2, also known as Ep-CAM, is expressed at high levels on the surface of most carcinomas and is therefore considered an attractive target for anticancer strategies. To explore the mechanisms regulating the expression of EGP-2, sequences 3.4 kb upstream of the transcription start site were isolated and assayed for their ability to control the expression of the EGP-2 cDNA, the green fluorescent protein, the luciferase reporter gene and the thymidine kinase and cytosine deaminase suicide genes. Expression of these chimeric constructs as assessed in a range of different cell lines was restricted to cell lines expressing EGP-2. In addition, only cells expressing EGP-2 were sensitive for gancyclovir after being transiently transfected with EGP-2 promoter-driven thymidine kinase. Deletion analyses defined 687 bp upstream as the basic proximal promoter region, which could confer epithelial-specific expression to the GFP reporter gene in vitro. As these EGP-2 sequences can confer promoter activity to reporter and suicide genes in an EGP-2 restricted manner, they may be useful for gene therapy of EGP-2 expressing carcinomas.

Overexpression of the cell adhesion molecules DDR1, Claudin 3, and Ep-CAM in metaplastic ovarian epithelium and ovarian cancer

PURPOSE

A better understanding of the molecular pathways underlying the development of epithelial ovarian cancer (EOC) is critical to identify ovarian tumor markers for use in diagnostic or therapeutic applications. The aims of this study were to integrate the results from 14 transcript profiling studies of EOC to identify novel biomarkers and to examine their expression in early and late stages of the disease.

EXPERIMENTAL DESIGN

A database incorporating genes identified as being highly up-regulated in each study was constructed. Candidate tumor markers were selected from genes that overlapped between studies and by evidence of surface membrane or secreted expression. The expression patterns of three integral membrane proteins, discoidin domain receptor 1 (DDR1), claudin 3 (CLDN3), and epithelial cell adhesion molecule, all of which are involved in cell adhesion, were evaluated in a cohort of 158 primary EOC using immunohistochemistry.

RESULTS

We confirmed that these genes are highly overexpressed in all histological subtypes of EOC compared with normal ovarian surface epithelium, identifying DDR1 and CLDN3 as new biomarkers of EOC. Furthermore, we determined that these genes are also expressed in ovarian epithelial inclusion cysts, a site of metaplastic changes within the normal ovary, in borderline tumors and in low-grade and stage cancer. A trend toward an association between low CLDN3 expression and poor patient outcome was also observed.

CONCLUSIONS

These results suggest that up-regulation of DDR1, CLDN3, and epithelial cell adhesion molecule are early events in the development of EOC and have potential application in the early detection of disease.

ING-1(heMAb), a monoclonal antibody to epithelial cell adhesion molecule, inhibits tumor metastases in a murine cancer model

ING-1(heMAb), a human-engineered monoclonal antibody (MAb) that specifically targets the epithelial cell adhesion molecule (Ep-CAM), kills adenocarcinoma cells in vitro and inhibits tumor growth in vivo. In the current study, we evaluated the efficacy of ING-1(heMAb) in a murine model of cancer metastases. Mice received intravenous dosing of 1 mg/kg ING-1(heMAb), twice a week, starting on day 2 or day 5. A negative control group received 1 mg/kg human immunoglobulin G with the same dose frequency starting on day 2. A positive control group received weekly 100 mg/kg 5-flurouracil/leucovorin starting on day 2. ING-1(heMAb)/day 2 treatment significantly reduced both the number of visible tumor nodules in body cavities (P <.01) and the number of metastases on lung surfaces (P <.005). The treatment also resulted in a 91% reduction of micrometastases in lung tissues (P <.0001). Delaying ING-1(heMAb) treatment until day 5 caused 54% reduction in micrometastases (P <.005). Our results indicate that a number of parameters, including treatment starting day, dose level, and dose frequency, are critical in achieving the optimal efficacy of ING-1(heMAb). We conclude that ING-1(heMAb) effectively reduced tumor metastases in a murine cancer model. Immunotherapy with ING-1(heMAb) may be beneficial in treating human metastatic diseases.

Redirected T-cell cytotoxicity to epithelial cell adhesion molecule-overexpressing adenocarcinomas by a novel recombinant antibody, E3Bi, in vitro and in an animal model

BACKGROUND

To redirect cytotoxic T cells to target a broad range of adenocarcinomas, the authors constructed a novel, recombinant, bispecific antibody, E3Bi, directed at the tumor-associated antigen, epithelial cell adhesion molecule (EpCAM), and the CD3 receptor on T cells.

METHODS

T cells were prepared from healthy blood donors. The cytotoxicity of activated T cells (ATC) redirected to tumor cells by E3Bi was measured with in vitro (51)Cr release assays. In vivo studies were performed in a severe combined immunodeficient (SCID)/Beige mouse xenograft model. Tumor-bearing mice were treated with low doses (1 mg/kg) or high doses (10 mg/kg) of E3Bi along with ATC (2 x 10(9) cells/kg), and treatment efficacy was evaluated both by ex vivo tumor cell survival assay after in vivo treatments and by in vivo tumor growth delay studies.

RESULTS

In vitro, targeting the EpCAM-overexpressing human tumor cell lines with E3Bi increased specific cytotoxicity of ATC by > 70% at an effector-to-target ratio of 2.5 (P < 0.001); this cytotoxicity was abolished competitively in the presence of an anti-EpCAM monoclonal antibody. In contrast, E3Bi did not enhance ATC cytotoxicity toward the low EpCAM-expressing tumor cell line. In ex vivo tumor cytotoxicity assays, a significant reduction in tumor cell survival (40% with low-dose E3Bi; 90% with high-dose E3Bi) was observed in E3Bi/ATC-treated mice compared with control mice that were treated with ATC only. In addition, SCID/Beige mice xenografted with LS174T tumors demonstrated a significant tumor growth delay (P = 0.0139) after receiving E3Bi/ATC/interleukin 2 (IL-2) compared with mice that received ATC/IL-2 alone.

CONCLUSIONS

E3Bi specifically and very efficiently redirected T cells to destroy EpCAM-overexpressing tumors both in vitro and in an animal model. These results suggest a therapeutic utility for E3Bi in the treatment of adenocarcinomas.

Target cell-restricted and -enhanced apoptosis induction by a scFv:sTRAIL fusion protein with specificity for the pancarcinoma-associated antigen EGP2

The apparent tumor selective apoptosis-inducing activity of recombinant soluble TNF-related apoptosis-inducing ligand (TRAIL) has aroused much interest for use in clinical application. However, to exploit fully its therapeutic potential, the characteristics of both the TRAIL receptor system and soluble TRAIL (sTRAIL) should be taken into account: first, the widespread expression of the various TRAIL receptors throughout the human body; second, the differential binding affinities and crosslinking requirements of the agonistic receptors TRAIL-R1 and TRAIL-R2; and third, the solution behavior of particular sTRAIL preparations. Therefore, we constructed a novel TRAIL fusion protein, designated scFvC54:sTRAIL, comprising the human scFv antibody fragment C54 genetically linked to the N-terminus of human sTRAIL. The scFvC54:sTRAIL fusion protein was designed to induce apoptosis by crosslinking of agonistic TRAIL receptors only after specific binding of scFvC54:sTRAIL to the abundantly expressed carcinoma-associated cell surface antigen EGP2 (alias EpCAM). Target antigen-restricted apoptosis induction was demonstrated for various EGP2-positive tumor cells and could be inhibited by an EGP2 competing antibody. Target antigen binding converted soluble scFvC54:sTRAIL into a membrane-bound form of TRAIL that was capable of signaling apoptosis not only through TRAIL-R1 but also through TRAIL-R2. Size-exclusion fast protein liquid chromatography (FPLC) indicated that scFvC54:sTRAIL was produced as stable and homogeneous trimers in the absence of detectable TRAIL aggregates. The favorable characteristics of the scFvC54:sTRAIL fusion protein potentially reduce the amount of sTRAIL required for antitumor activity and may be of value for the treatment of various human carcinomas.

Frequent EpCam protein expression in human carcinomas

Expression of the transmembrane glycoprotein EpCam (epithelial cellular adhesion molecule) occurs in normal epithelium of different organs and was described in carcinomas of various sites. Specific anti-EpCam therapies are now being used in clinical trials. Thus, it is of interest to know which tumor types express or overexpress this protein, and in what frequency. We therefore analyzed EpCam expression by immunohistochemistry on a tissue microarray containing 3900 tissue samples of 134 different histological tumor types and subtypes. EpCam expression was detected in 98 of 131 tumor categories. At least a weak EpCam expression in >10% of tumors was observed in 87 of 131 different tumor categories. Adenocarcinomas of the colon (81%) and pancreas (78%), as well as hormone-refractory adenocarcinomas of the prostate (71%), were identified as particularly promising therapy targets with a high fraction of strongly positive tumors. Most soft-tissue tumors and all lymphomas were EpCam negative. It is concluded that anti-EpCam therapies, if proven to be successful, will have broad applications in a wide variety of carcinomas.

Immunization with a plant-produced colorectal cancer antigen

Cancer vaccination has become an important focus of oncology in recent years. Active immunization with tumor-associated antigens such as colorectal cancer antigen GA733-2 is thought to potentially overcome the reoccurrence of metastasis. As recombinant protein production in bioreactors is costly and subject to growing safety concerns, we tested plants as an alternative for the expression of a potential colorectal cancer vaccine. Comparing colorectal cancer antigen GA733-2 produced in tobacco plants with the same antigen produced in insect cell culture, we found a similar humoral immune response to injection of either of the two antigen preparations into mice. Some minor differences were observed in the cellular response that might be due to impurities. Our studies compare for the first time, immunization with the same antigen expressed in either plants or insect cell culture. This will provide important data for use of plants as production systems of therapeutics.

Cancer-associated molecular signature in the tissue samples of patients with cirrhosis

Several types of aggressive cancers, including hepatocellular carcinoma (HCC), often arise as a multifocal primary tumor. This suggests a high rate of premalignant changes in noncancerous tissue before the formation of a solitary tumor. Examination of the messenger RNA expression profiles of tissue samples derived from patients with cirrhosis of various etiologies by complementary DNA (cDNA) microarray indicated that they can be grossly separated into two main groups. One group included hepatitis B and C virus infections, hemochromatosis, and Wilson's disease. The other group contained mainly alcoholic liver disease, autoimmune hepatitis, and primary biliary cirrhosis. Analysis of these two groups by the cross-validated leave-one-out machine-learning algorithms revealed a molecular signature containing 556 discriminative genes (P <.001). It is noteworthy that 273 genes in this signature (49%) were also significantly altered in HCC (P <.001). Many genes were previously known to be related to HCC. The 273-gene signature was validated as cancer-associated genes by matching this set to additional independent tumor tissue samples from 163 patients with HCC, 56 patients with lung carcinoma, and 38 patients with breast carcinoma. From this signature, 30 genes were altered most significantly in tissue samples from high-risk individuals with cirrhosis and from patients with HCC. Among them, 12 genes encoded secretory proteins found in sera. In conclusion, we identified a unique gene signature in the tissue samples of patients with cirrhosis, which may be used as candidate markers for diagnosing the early onset of HCC in high-risk populations and may guide new strategies for chemoprevention. Supplementary material for this article can be found on the HEPATOLOGY website (http://interscience.wiley.com/jpages/0270-9139/suppmat/index.html).

A nonviral carrier for targeted gene delivery to tumor cells

In this study, we developed a nonviral, cationic, targeted DNA-carrier system by coupling SAINT/DOPE lipids to monoclonal antibodies. The two monoclonal antibodies used were both tumor specific, that is, MOC31 recognizes the epithelial glycoprotein EGP-2 present in carcinomas and Herceptin recognizes the HER-2/neu protein in breast and ovarian cancers. Coupling was performed under nonreducing conditions by covalent attachment. The coupling procedure appeared to be reproducible and the binding capacity of the antibody was not affected by linking them to the cationic lipid. Binding and transfection efficiency was assayed with target cells and nontarget cells. SAINT/DOPE lipoplexes as such appeared to be an effective transfection reagent for various cell lines. After coupling SAINT/DOPE to the monoclonal antibodies or F(ab)2 fragments, it was shown that the targeted MoAb-SAINT/DOPE lipoplexes preferably bound to target cells, compared to binding to the nontarget cells, especially for the Herceptin-SAINT/DOPE lipoplexes. More importantly, transfection of the target cells could also be improved with these targeted lipoplexes. In conclusion, we have shown that by using monoclonal antibody-coupled SAINT/DOPE lipoplexes cells targeted gene delivery can be achieved, and also a higher number of transfected target cells was seen.

Addition of interleukin-12 to GA733 tumor protein vaccine leads to development of tumor protective immunity despite surgical stress

BACKGROUND

We have previously shown that preoperative vaccination with the GA733 protein does not inhibit tumor growth in mice undergoing open surgery or carbon dioxide insufflation. In this study we assessed the antitumor effect of a combined GA733 and interleukin-12 (IL-12) vaccine.

METHODS

For this study, BALB/c mice were immunized with GA733, IL-12, or GA733 and IL-12, or they received no vaccine. Immediately after surgery (laparotomy or insufflation), GA733-transfected CT26 cells (C26-GA733) were injected subcutaneously into all mice. After 5 weeks, the mice were sacrificed, their tumors measured, GA733-specific antibodies determined by enzyme-linked immunoassay, and GA-733-specific cytotoxicity tested by flow cytometry using labeled C26-GA733 cells.

RESULTS

Tumors were significantly (p < 0.05) smaller in both the insufflation and open groups that received combined GA733 and IL-12 than in their respective control subjects. Vaccination also induced a significant increase in the antibody and cell-mediated tumor-specific immunity.

CONCLUSION

A preoperative vaccine consisting of GA733 and IL-12 inhibited postoperative tumor growth after open and closed surgery and allowed the mice to overcome the immunosuppressive effects of surgery.

Differences in T-cell immunity toward tumor-associated antigens in colorectal cancer and breast cancer patients

There is increasing evidence that tumors elicit specific T-cell responses in a substantial proportion of patients. Recently, we have shown that in patients with colorectal cancer specific T cells against the tumor-associated antigens (TAA) Ep-CAM, her-2/neu or CEA can be detected in peripheral blood using IFNgamma-ELISPOT assay. In our study, we have analyzed T-cell responses against HLA-A*0201-restricted epitopes of these TAA in peripheral blood of patients with breast cancer and colorectal cancer. Surprisingly, a complete absence of ex vivo T-cell responses against these TAA was found in 20 patients with breast cancer. In contrast, specific T cells were detectable in 12 of 49 patients with colorectal cancer against at least 1 of these TAA, confirming our previous results. T-cell responses against influenza-derived peptides were similar in both malignancies. The results of our study indicate a difference either of tumor immunogenicity or of the migratory pattern of tumor-specific T cells between breast cancer and colorectal cancer patients. The findings reported here have implications for the development of antigen-specific T-cell therapies.

Efficient tumor cell lysis by autologous, tumor-resident T lymphocytes in primary ovarian cancer samples by an EP-CAM-/CD3-bispecific antibody

The epithelial cell adhesion molecule (Ep-CAM) is expressed on the surface of most human carcinomas, including ovarian, breast, lung, prostate and colorectal carcinoma. Ep-CAM was shown to be a valid target for monoclonal antibody-based therapies. We have investigated whether an Ep-CAM-/CD3-bispecific single-chain antibody called bscEp-CAM x CD3 is effective in tumor cell elimination within the cellular microenvironment of primary ovarian cancer tissue. The ex vivo elimination of ovarian cancer cells in tumor preparations from 21 patients was monitored by flow cytometry using Ep-CAM/CA-125 double-labeling or Ep-CAM single-labeling combined with propidium iodide uptake of cells. Methodology was established by the ovarian cancer cell line OvCAR. A total of 17 (81%) patient samples showed a dose-dependent tumor cell elimination by bscEp-CAM x CD3. High and specific tumor cell lysis was seen at bscEp-CAM x CD3 concentrations as low as 1 ng/ml, at very low effector:target ratios and in the absence of T cell costimulation. The high efficacy of the bispecific antibody may be due to the non-restricted activation of tumor-resident cytotoxic T lymphocytes. In clinical trials, the ex vivo data with the T cell-recruiting bispecific antibody bscEp-CAM x CD3 may translate into a high response rate and efficacy of tumor cell elimination.

Redirecting T lymphocyte specificity using T cell receptor genes

Redirecting T cells by transferring T cell receptor (TCR) genes from tumor-associated antigen (TAA)-reactive T cell clones into human peripheral blood lymphocytes (PBL) has therapeutic potential for the treatment of diseases, including cancer. T cell specificity can be altered using retroviruses encoding TCRalpha and TCRbeta chain genes, or chimeric immunoglobulin (cIg) genes containing signaling domains of CD3 zeta or Fc epsilon RI-gamma. This review evaluates recent studies using TCRs and cIgs to redirect T cell specificity and discusses some of the technical and biological hurdles that need to be addressed before these approaches can be successfully used to treat patients.

Expression of Ep-CAM shifts the state of cadherin-mediated adhesions from strong to weak

Various adhesion molecules play an important role in defining cell fate and maintaining tissue integrity. Therefore, cross-signaling between adhesion receptors should be a common phenomenon to support the orchestrated changes of cells' connections to the substrate and to the neighboring cells during tissue remodeling. Recently, we have demonstrated that the epithelial cell adhesion molecule Ep-CAM negatively modulates cadherin-mediated adhesions in direct relation to its expression levels. Here, we used E-cadherin/alpha-catenin chimera constructs to define the site of Ep-CAM's negative effect on cadherin-mediated adhesions. Murine L-cells transfected with either E-cadherin/alpha-catenin fusion protein, or E-cadherin fused to the carboxy-terminal half of alpha-catenin, were subsequently supertransfected with an inducible Ep-CAM construct. Introduction of Ep-CAM altered the cell's morphology, weakened the strength of cell-cell interactions, and decreased the cytoskeleton-bound fraction of the cadherin/catenin chimeras in both cell models. Furthermore, expression of Ep-CAM induced restructuring of F-actin, with changes in thickness and orientation of the actin filaments. The results showed that Ep-CAM affects E-cadherin-mediated adhesions without involvement of beta-catenin by disrupting the link between alpha-catenin and F-actin. The latter is likely achieved through remodeling of the actin cytoskeleton by Ep-CAM, possibly through pp120.

Tumor-specific glycosylation of the carcinoma-associated epithelial cell adhesion molecule EpCAM in head and neck carcinomas

The tissue-specific glycosylation of the carcinoma (CA)-associated antigen epithelial cell adhesion molecule (EpCAM) was studied in 60 patients suffering from head and neck CAs, and 26 pairs of autologous healthy thyroid and CA biopsies. EpCAM was glycosylated in all tumor samples in which its expression was detectable (73%). Additionally, in 80.7% of patients, tumor-derived EpCAM was heavily glycosylated while EpCAM derived from autologous thyroid was not (76.2%) or weakly (23.8%). Four cases showed a similar glycosylation pattern (15.3%) and one case displayed a reverse pattern (3.8%). Additionally, the expression and glycosylation of EpCAM were assessed in tumor adjacent and distant tissue. EpCAM was glycosylated in tumor-adjacent while it was not or only weakly expressed in tumor distant tissue where it was unglycosylated. Thus, EpCAM is differentially glycosylated in healthy tissue and tumor cells of the head and neck area.

In vitro and in vivo pharmacology and pharmacokinetics of a human engineered monoclonal antibody to epithelial cell adhesion molecule

ING-1(heMAb), a Human Engineered monoclonal antibody to epithelial cell adhesion molecule (Ep-CAM), was evaluated for its in vitro and in vivo activity. The dissociation constant of ING-1(heMAb) for binding to Ep-CAM on HT-29 human colon tumor cells was 2 to 5 nM, similar to chimeric ING-1. In antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity assays, ING-1(heMAb) caused a concentration-dependent lysis of BT-20 breast, MCF-7 breast, HT-29 colon, and CACO-2 colon tumor cells, with maximum cytolysis at approximately 1 microg/ml. After an intravenous injection in rats, plasma ING-1(heMAb) levels declined with an alpha half-life of 8 to 11 hours, and a beta half-life of 20 days, typical of an IgG in a species without the target for ING-1. In nude mice with human HT-29 colon tumors, plasma ING-1(heMAb) levels declined more rapidly than in non-tumor-bearing mice, suggesting an enhanced clearance via the tumor-associated human Ep-CAM. In nude mice, intravenous treatments with ING-1(heMAb) twice a week for 3 weeks significantly suppressed the growth of human HT-29 colon and PC-3 prostate tumors in a dose-dependent manner, with 1.0 mg/kg providing the greatest benefit. These results indicate that Human Engineered ING-1(heMAb) is a high-affinity antibody with potent in vitro activity that targets and suppresses the growth of human tumors in vivo.

Preparation of recombinant MK-1/Ep-CAM and establishment of an ELISA system for determining soluble MK-1/Ep-CAM levels in sera of cancer patients

The MK-1 antigen, also termed as Ep-CAM, is a membrane glycoprotein that is overexpressed on the majority of tumor cells of epithelial origin and thereby can be used as a target of immunodetection and immunotherapy of cancer. It has previously been shown that several type-I transmembrane proteins, including E-cadherin, ErbB-2 and intercellular adhesion molecule-1 (ICAM-1), may be useful as tumor markers because they are released into the circulation of many cancer patients. To address the question of whether MK-1, the same type-I membrane protein, is also released into the sera, we developed a sandwich-type enzyme-linked immunosorbent assay (ELISA) system by preparing a recombinant MK-1 protein and two anti-MK-1 monoclonal antibodies with different epitope specificities. Using this ELISA, we found that the MK-1 levels in serum samples from healthy volunteers were all less than 2 ng/ml, whereas the Mk-1 levels in sera of about 10% of patients with malignant tumors of various tissue origins were increased to 2-78 ng/ml, indicating that MK-1 is released from tumor cells into the circulation under certain conditions. These findings should be borne in mind when trying to perform passive antibody therapy for cancer using anti-MK-1 antibody.

Flow cytometry correlates with RT-PCR for detection of spiked but not circulating colorectal cancer cells

The aim of this study was to determine whether flow cytometry (FACS) could detect spiked or circulating colorectal cancer cells. A flow cytometric assay was developed and its sensitivity compared with the reverse transcription polymerase-chain reaction (RT-PCR), using carcinoembryonic antigen (CEA) and cytokeratin (CK) 20 mRNA as target markers. Sensitivity limits for RT-PCR and flow cytometry (FACS) were established using spiked blood, and pre-operative blood samples from 20 colorectal cancer patients and 16 healthy no-cancer controls were analysed for circulating tumour cells (CTC) using both methods. Blood samples for FACS analysis were immuno-magnetically enriched using ferrofluid particles. CTC were defined as positive for pan-cytokeratin and negative for CD45 pan-leucocyte antigen (CK+/CD45- events). There was a significant (P < 0.0001) correlation between the number of spiked cancer cells and their recovery using FACS. The lowest detectable concentration was 20 spiked cancer cells in 14 ml blood for both RT-PCR and FACS. A positive FACS result significantly (P < 0.05) concurred with a positive RT-PCR result in spiked blood. The number of CK+/CD45- events detected in the blood of colorectal cancer patients was not significantly greater (P = 0.07) than in blood taken from 'no cancer' controls and furthermore there was no concordance (P = 1) between RT-PCR and FACS positivity in cancer patients' blood. FACS detection of tumour cells was feasible in vitro, and correlated with RT-PCR. However, its sensitivity in vivo was poor and did not correlate with RT-PCR detection of CTC. Uncertainties about antigen expression on normal circulating cells and about CTC phenotype need to be resolved, before FACS can be developed for detection of tumour cells within the circulation.

Intraperitoneal bispecific antibody (HEA125xOKT3) therapy inhibits malignant ascites production in advanced ovarian carcinoma

Bispecific antibody HEA125 x OKT3 was shown to redirect T lymphocytes toward carcinoma cells and to induce tumor cell lysis in vitro. Preclinical studies have demonstrated that tumor-associated lymphocytes (TAL) derived from malignant ascites can be used as effector cells with a high efficacy and without prior stimulation. These data provided the rationale for a clinical trial to investigate whether bsAb HEA125 x OKT3 is also able to induce tumor cell lysis in vivo and can be used for local treatment of malignant ascites arising from ovarian carcinoma. Ten ovarian carcinoma patients presenting with malignant ascites resistant to chemotherapy were enrolled in the study. They received weekly intraperitoneal injections of 1 mg bsAb diluted in 500 ml NaCl solution to allow homogeneous antibody distribution within the peritoneal cavity. All patients responded clinically well to the therapy. Eight patients experienced a complete and 2 patients a partial reduction of ascites production. A decrease or stabilization of tumor marker CA125 was detected in the sera of 8 patients. Only WHO Grade I and II toxicity was observed including mild fever, chills and allergic eczema. Thus, intraperitoneal application of bsAb HEA125 x OKT3 appears to be an easy and cost effective palliative treatment for ovarian carcinoma with recurrent ascites that leads to a substantially increased quality of life for the patients. During therapy TNF-alpha concentrations raised markedly in the ascites fluid whereas VEGF and sFLT-1 ascites levels declined. This indicates that not only T cell-mediated tumor cell lysis but also changes in vascular permeability due to downregulation of VEGF and its receptors might be responsible for the beneficial therapeutic effect.

Development of a frozen cell array as a high-throughput approach for cell-based analysis

Recent advances in molecular biology, human genetics, and functional genomics tremendously increase the number of molecular targets available for potential therapeutic and diagnostic use. To complement DNA array data, cost-efficient high-throughput technologies providing reliable information at the protein level need to be developed. Here we describe the generation of a frozen cell array that required the use of single cell suspensions and could serve various applications such as the analysis of specific antibody or ligand binding to a large panel of different cell types. As an example, binding of an anti-human epithelial cell adhesion molecule monoclonal antibody to 24 different cell lines has been analyzed using the cell array and compared to the data generated by fluorescence-activated cell sorting. The reliability and flexibility of our frozen cell array technology is compatible with the needs of high-throughput screening for drug discovery and target validation.

Chemotherapy for colorectal cancer

With effective chemotherapy as adjuvant treatment, the survival benefit is clearly achieved for certain (stage III) colorectal cancer patients, though there still exist many unsettled issues including the controversies in the treatment of stage II disease. Advances in the development of a new generation of cytotoxic agents in the past several years have allowed us to move forward from the "fluorouracil-only era" in the treatment of advanced/metastatic colorectal cancer. It is still not very clear how best to minimize toxicity without compromising efficacy of the combination therapy with newer agents, or how to maximize the benefit of chemotherapy (concurrent versus sequential). There are many current ongoing clinical trials designed to address these issues. With better understanding of the signal transduction and molecular biology characteristics of colorectal cancer, and the development of biologic and molecular target agents, the outcomes of patients with colorectal cancer will be improved further. Future clinical trials should be focused on optimizing and individualizing therapy for patients based on their molecular profiles to achieve maximal clinical benefit.

In silico data filtering to identify new angiogenesis targets from a large in vitro gene profiling data set

The objective of this study was to use gene expression data from well-defined cell culture models, in combination with expression data from diagnostic samples of human diseased tissues, to identify potential therapeutic targets and markers of disease. Using Affymetrix oligonucleotide array technology, we identified a common profile of genes upregulated during endothelial morphogenesis into tubelike structures in three in vitro models of angiogenesis. Rigorous data selection criteria were used to identify a list of over 1,000 genes whose expression was increased more than twofold over baseline at either 4, 8, 24, 40 or 50 h. To further refine and prioritize this list, we used standard bioinformatic algorithms to identify potential transmembrane and secreted proteins. We then overlapped this gene set with genes upregulated in colon tumors vs. normal colon, resulting in a subset of 128 genes in common with our endothelial list. We removed from this list those genes expressed in 6 different colon tumor lines, resulting in a list of 24 putative, vascular-specific angiogenesis-associated genes. Three genes, gp34, stanniocalcin-1 (STC-1), and GA733-1, were expressed at levels 10-fold or more in colon tumors compared with normal mucosa. We validated the vascular-specific expression of one of these genes, STC-1, by in situ hybridization. The ability to combine in vitro and in vivo data sets should permit one to identify putative angiogenesis target genes in various tumors, chronic inflammation, and other disorders where therapeutic manipulation of angiogenesis is a desirable treatment modality.

Epidermal growth factor receptor targeting of replication competent adenovirus enhances cytotoxicity in bladder cancer

PURPOSE

We evaluated the delivery and oncolytic potential of targeted replication competent adenoviruses in bladder cancer lines.

MATERIALS AND METHODS

Seven established human bladder cancer tumor lines (5637, SW800, TCCsup, J82, Scaber, T24 and 253J) were studied for the expression of integrins alpha(v)beta3, alpha(v)beta5, Coxsackievirus and adenovirus receptor, epidermal growth factor receptor (EGF-R) and epithelial cell adhesion molecule antigens using flow cytometry analysis. Bispecific single chain Fv fragments were used to target replication deficient luciferase reporter adenovirus to EGF-R (425-s11) or to epithelial cell adhesion molecule (C28-s11) antigens. Moreover, a fiber modified adenovirus targeting alpha(v)-integrins was studied. Replication competent serotype-5 adenoviruses attenuated to replicate specifically in retinoblastoma pRb (Ad5-d24) or p53 deficient (Ad5-d55K) cells were tested in vitro for oncolytic properties.

RESULTS

Low to absent Coxsackievirus and adenovirus receptor expression was found in 5 of the 7 tumor lines (SW800, J82, T24, 5637 and Scaber). EGF-R expression was found in all cell lines, whereas elevated epithelial cell adhesion molecule expression was seen in 3 (5637, Scaber and TCCsup), alpha(v)beta3-integrin was found in 1 (Scaber) and alpha(v)beta5-integrin was found in 3 (TCCsup, 253J and T24). EGF-R targeting using 425-s11 improved transgene expression in all cell lines from 2.1 to 12.5 times over nontargeted viruses. Epithelial cell adhesion molecule and integrin targeting was inferior to EGF-R targeting with a maximal increase in transgene expression of 2 times for epithelial cell adhesion molecule in 5637cells and 1.6 times for integrin targeting in T24 cells. Comparison of the wild-type replication competent virus with conditionally replicating adenoviruses (Ad5-d55K and Ad5-d24) showed superior oncolytic activity for the latter 2 in all lines. Furthermore, improved cytotoxicity (29% to 33%) was obtained in 4 of the 7 lines after pre-incubation of Ad5-d24 with 425-s11.

CONCLUSIONS

EGF-R directed bispecific single chain antibodies enhance adenovirus mediated transgene expression and oncolysis in bladder cancer lines.

Epidermal growth factor receptor targeting of replication competent adenovirus enhances cytotoxicity in bladder cancer

PURPOSE

We evaluated the delivery and oncolytic potential of targeted replication competent adenoviruses in bladder cancer lines.

MATERIALS AND METHODS

Seven established human bladder cancer tumor lines (5637, SW800, TCCsup, J82, Scaber, T24 and 253J) were studied for the expression of integrins alpha(v)beta3, alpha(v)beta5, Coxsackievirus and adenovirus receptor, epidermal growth factor receptor (EGF-R) and epithelial cell adhesion molecule antigens using flow cytometry analysis. Bispecific single chain Fv fragments were used to target replication deficient luciferase reporter adenovirus to EGF-R (425-s11) or to epithelial cell adhesion molecule (C28-s11) antigens. Moreover, a fiber modified adenovirus targeting alpha(v)-integrins was studied. Replication competent serotype-5 adenoviruses attenuated to replicate specifically in retinoblastoma pRb (Ad5-d24) or p53 deficient (Ad5-d55K) cells were tested in vitro for oncolytic properties.

RESULTS

Low to absent Coxsackievirus and adenovirus receptor expression was found in 5 of the 7 tumor lines (SW800, J82, T24, 5637 and Scaber). EGF-R expression was found in all cell lines, whereas elevated epithelial cell adhesion molecule expression was seen in 3 (5637, Scaber and TCCsup), alpha(v)beta3-integrin was found in 1 (Scaber) and alpha(v)beta5-integrin was found in 3 (TCCsup, 253J and T24). EGF-R targeting using 425-s11 improved transgene expression in all cell lines from 2.1 to 12.5 times over nontargeted viruses. Epithelial cell adhesion molecule and integrin targeting was inferior to EGF-R targeting with a maximal increase in transgene expression of 2 times for epithelial cell adhesion molecule in 5637cells and 1.6 times for integrin targeting in T24 cells. Comparison of the wild-type replication competent virus with conditionally replicating adenoviruses (Ad5-d55K and Ad5-d24) showed superior oncolytic activity for the latter 2 in all lines. Furthermore, improved cytotoxicity (29% to 33%) was obtained in 4 of the 7 lines after pre-incubation of Ad5-d24 with 425-s11.

CONCLUSIONS

EGF-R directed bispecific single chain antibodies enhance adenovirus mediated transgene expression and oncolysis in bladder cancer lines.

In vitro and in vivo activity of MT201, a fully human monoclonal antibody for pancarcinoma treatment

In our study, a novel, fully human, recombinant monoclonal antibody of the IgG1 isotype, called MT201, was characterized for its binding properties, complement-dependent (CDC) and antibody-dependent cellular cytotoxicity (ADCC), as well as for its in vivo antitumor activity in a nude mouse model. MT201 was found to bind its target, the epithelial cell adhesion molecule (Ep-CAM; also called 17-1A antigen, KSA, EGP-2, GA733-2), with low affinity in a range similar to that of the clinically validated, murine monoclonal IgG2a antibody edrecolomab (Panorex(R)). MT201 exhibited Ep-CAM-specific CDC with a potency similar to that of edrecolomab. However, the efficacy of ADCC of MT201, as mediated by human immune effector cells, was by 2 orders of magnitude higher than that of edrecolomab. Addition of human serum reduced the ADCC of MT201 while it essentially abolished ADCC of edrecolomab within the concentration range tested. In a nude mouse xenograft model, growth of tumors derived from the human colon carcinoma line HT-29 was significantly and comparably suppressed by MT201 and edrecolomab. The fully human nature and the improved ADCC of MT201 with human effector cells will make MT201 a promising candidate for the clinical development of a novel pan-carcinoma antibody that is superior to edrecolomab.

Monoclonal antibody 9C4 recognizes epithelial cellular adhesion molecule, a cell surface antigen expressed in early steps of erythropoiesis

OBJECTIVE

Monoclonal antibody (mAb) 9C4 detects a surface antigen expressed on immature erythroid progenitor cells and epithelial tumor cell lines. The aim of this study was to identify the recognized surface antigen and to analyze a potential role of this molecule in early steps of erythropoiesis.

MATERIALS AND METHODS

A pituitary-derived retroviral cDNA library was used to generate viruses and infect NIH-3T3 fibroblasts. The transfected cells were stained with mAb 9C4; positive cells were sorted by FACS; and a clonal cell line binding mAb 9C4 was established. cDNA encoding the 9C4-binding protein was amplified by polymerase chain reaction and cloned. Reactivity of mAb 9C4 with human bone marrow (BM) cells was analyzed by flow cytometry.

RESULTS

Sequence analysis of the isolated cDNA uncovered a 100% identity with the epithelial cellular adhesion molecule (Ep-CAM). Two-color flow cytometric analysis revealed that almost 100% of Ep-CAM(+) BM cells coexpressed CD105, E-cadherin, and high levels of CD71. Fractions of Ep-CAM(+) BM cells also were CD34(+) but lacked glycophorin A expression, suggesting that Ep-CAM(+) cells represent immature erythroid cells. Reverse transcriptase polymerase chain reaction analysis of BM mononuclear cells revealed that the 9C4(+) erythroblast population but not the 9C4(-) fraction expressed Ep-CAM mRNA. Peripheral blood CD34(+) cells induced in vitro to differentiate into the erythroid lineage showed strong Ep-CAM expression on days 3 to 7 of culture. The addition of Ep-CAM-specific mAbs 9C4 or KS1/4 to the culture resulted in two- to three-fold up-regulation of Ep-CAM protein expression.

CONCLUSION

mAb 9C4 recognizes Ep-CAM, a molecule expressed in the early steps of erythropoiesis.

Real-time polymerase chain reaction monitoring of epithelial cell adhesion molecule-induced T-cell stimulation in patients with lung cancer and healthy individuals using LightCycler technology

The epithelial cell adhesion molecule is strongly expressed in carcinomas of diverse histologic origin and has attracted attention as a target for immunotherapy. We have previously demonstrated that the epithelial cell adhesion molecule-derived human leukocyte antigen-A*0201-restricted nonamer peptide ILYENNVIT(184-192) can be efficiently recognized by peptide-specific cytotoxic T lymphocytes (CTL). Using this peptide (Ep-2) we could readily expand precursor CTL and demonstrate their cytotoxicity by standard chromium-release assay. We now sought to evaluate the immune reactivity of Ep-2-specific CTL expanded from the peripheral blood mononuclear cells by real-time quantitative polymerase chain reaction assay (LightCycler system) measuring the change in interferon-gamma mRNA levels upon stimulation. Cytotoxic T lymphocyte response against the Ep-2 peptide in two patients with epithelial cell adhesion molecule-expressing lung cancer and three healthy donors was compared with the chromium-release assay. In vitro expanded epithelial cell adhesion molecule-specific CTL precursors that exhibited significantly elevated interferon-gamma mRNA levels also lysed Ep-2 peptide-pulsed target cells. Our study indicates that quantitative polymerase chain reaction may be a supplement to chromium-release assay for monitoring in vitro expanded CTL precursor reactivity.

Functional detection of epithelial cell adhesion molecule specific cytotoxic T lymphocytes in patients with lung cancer, colorectal cancer and in healthy donors

Epithelial cell adhesion molecule (Ep-CAM) derived antigenic peptides have been identified that can be recognized by cytotoxic T lymphocytes (CTL) in a major histocompatibility complex (MHC) class I restricted fashion. Thus, altered expression of Ep-CAM in a variety of human tumors might render a potential target for T cell mediated therapy. We have examined, whether the novel HLA-A*0201 restricted peptide ILYENNVIT (184-192) corresponding to Ep-CAM and one heteroclitic modified variant peptide previously demonstrated to be immunogenic in the human system can elicit antigen specific CTL responses in HLA-A2 positive patients with history of Ep-CAM expressing cancer of lung and colon. Specific CTL recognition of T2 target cells pulsed with the native peptide as well as of the lung cancer cell line A549 indicates that an appropriate T cell repertoire can be expanded from peripheral blood from patients in clinical remission and with advanced cancer. Despite an overall low frequency, peptide specific precursor CTLs could be readily expanded from peripheral blood from 6/8 patients that were diagnosed previously with Ep-CAM expressing lung cancer and 4/8 control individuals (2/5 healthy donors and 2/3 colon cancer patients). CTLs from three of five lung cancer patients tested also lyzed the HLA-A2(+) and Ep-CAM expressing lung cancer cell line A549. We did not detect an increased frequency of pCTLs after peripheral blood monocytes (PBMCs) were stimulated with the heteroclitic compound peptide. The results of our study indicate that Ep-CAM specific precursor CTL can be expanded in vitro and a specific T cell response against this epitope can be elicited in patients at various stages of lung cancer.

Prognostic significance of Ep-CAM AND Her-2/neu overexpression in invasive breast cancer

To assess the frequency and prognostic impact of Ep-CAM and Her-2/neu overexpression in patients with breast cancer and to determine its relationship with other prognostic markers, 205 breast cancer patients with a median follow-up of 10.8 years were enrolled in this retrospective study. Overexpression of Ep-CAM and Her-2/neu in tumor tissue samples was assessed by immunohistochemistry. Tumors presenting a Her-2/neu 2+ staining were additionally analyzed by FISH to exclude false positive results. Ep-CAM and Her-2/neu overexpression was found in 35.6% and 19.5% of the tumor samples, respectively. Both Ep-CAM and Her-2/neu overexpression were predictive for poor disease-free (DFS) and disease-related overall survival (DROS). Concurrent Ep-CAM and Her-2/neu overexpression was present in 13.2% of tumor specimens and had an additive negative impact on DFS and DROS. This minority of patients had a median time to relapse of only 34 months, whereas the median time to relapse was not reached in the patient population without Her-2/neu and Ep-CAM overexpression. By multivariate analysis Ep-CAM overexpression proved to be an indicator of poor prognosis, independent of tumor size, histologic grade, hormone receptor expression and Her-2/neu overexpression. In conclusion, overexpression of Ep-CAM and Her-2/neu complement each other as predictors for poor prognosis in patients with invasive breast cancer. Determination of these tumor markers should help in assigning breast cancer patients to 1 of 3 distinct risk categories.

Isolation, immortalization, and characterization of a human breast epithelial cell line with stem cell properties

The epithelial compartment of the human breast comprises two distinct lineages: the luminal epithelial and the myoepithelial lineage. We have shown previously that a subset of the luminal epithelial cells could convert to myoepithelial cells in culture signifying the possible existence of a progenitor cell. We therefore set out to identify and isolate the putative precursor in the luminal epithelial compartment. Using cell surface markers and immunomagnetic sorting, we isolated two luminal epithelial cell populations from primary cultures of reduction mammoplasties. The major population coexpresses sialomucin (MUC(+)) and epithelial-specific antigen (ESA(+)) whereas the minor population has a suprabasal position and expresses epithelial specific antigen but no sialomucin (MUC(-)/ESA(+)). Two cell lines were further established by transduction of the E6/E7 genes from human papilloma virus type 16. Both cell lines maintained a luminal epithelial phenotype as evidenced by expression of the tight junction proteins, claudin-1 and occludin, and by generation of a high transepithelial electrical resistance on semipermeable filters. Whereas in clonal cultures, the MUC(+)/ESA(+) epithelial cell line was luminal epithelial restricted in its differentiation repertoire, the suprabasal-derived MUC(-)/ESA(+) epithelial cell line was able to generate itself as well as MUC(+)/ESA(+) epithelial cells and Thy-1(+)/alpha-smooth muscle actin(+) (ASMA(+)) myoepithelial cells. The MUC(-)/ESA(+) epithelial cell line further differed from the MUC(+)/ESA(+) epithelial cell line by the expression of keratin K19, a feature of a subpopulation of epithelial cells in terminal duct lobular units in vivo. Within a reconstituted basement membrane, the MUC(+)/ESA(+) epithelial cell line formed acinus-like spheres. In contrast, the MUC(-)/ESA(+) epithelial cell line formed elaborate branching structures resembling uncultured terminal duct lobular units both by morphology and marker expression. Similar structures were obtained by inoculating the extracellular matrix-embedded cells subcutaneously in nude mice. Thus, MUC(-)/ESA(+) epithelial cells within the luminal epithelial lineage may function as precursor cells of terminal duct lobular units in the human breast.

A mixed hemadsorption assay for detection of cell surface binding anti-tumor antibodies in human sera

A practical mixed hemadsorption assay (MHA) was developed for the detection of cell surface binding anti-tumor antigen antibodies (anti-TA Ab) in the human sera. The assay was compared to enzyme-linked immunosorbent assay (ELISA) and dot ELISA in the detection of the antibodies developed against GA733-2 antigen. SW1116 cell line and recombinant GA733-2E protein were used as targets in the MHA and solid phase immunoassays (SPIA), respectively. Sera were obtained from healthy donors and vaccinated-colon carcinoma patients. The sensitivity level of the MHA was very high for detection of anti-TA Ab in sera.

Autologous dendritic cells transfected with prostate-specific antigen RNA stimulate CTL responses against metastatic prostate tumors

Autologous dendritic cells (DCs) transfected with mRNA encoding prostate-specific antigen (PSA) are able to stimulate potent, T cell-mediated antitumor immune responses in vitro. A phase I trial was performed to evaluate this strategy for safety, feasibility, and efficacy to induce T cell responses against the self-protein PSA in patients with metastatic prostate cancer. In 13 study subjects, escalating doses of PSA mRNA-transfected DCs were administered with no evidence of dose-limiting toxicity or adverse effects, including autoimmunity. Induction of PSA-specific T cell responses was consistently detected in all patients, suggesting in vivo bioactivity of the vaccine. Vaccination was further associated with a significant decrease in the log slope PSA in six of seven subjects; three patients that could be analyzed exhibited a transient molecular clearance of circulating tumor cells. The demonstration of vaccine safety, successful in vivo induction of PSA-specific immunity, and impact on surrogate clinical endpoints provides a scientific rationale for further clinical investigation of RNA-transfected DCs in the treatment of human cancer.

Enhancement of the complement activating capacity of 17-1A mAb to overcome the effect of membrane-bound complement regulatory proteins on colorectal carcinoma

Adjuvant immunotherapy with 17-1A mAb directed against colorectal carcinoma is found to be effective in patients. However, 52 % of the patients treated with mAb 17-1A showed recurrence within 7 years. This high recurrence rate might be due to inhibition of complement activation by membrane-bound complement regulatory proteins (mCRP). The effect of these complement regulatory proteins might be reduced by blocking mCRP, or be overcome by activating more complement at the tumor cell membrane. In this study the complement-activating capacity of the 17-1A mAb was enlarged by conjugating it to cobra venom factor (CVF) or C3b. The most important C3 regulatory protein, CD55, was blocked using a bispecific mAb directed against the 17-1A / Ep-CAM antigen and CD55. Up to a 13-fold increase in C3 deposition was observed due to 17-1A-CVF and 17-1A-C3b, as compared to 17-1A. CD55 was shown to partly inhibit complement activation by these conjugates. The effect of the bispecific anti-17-1A / Ep-CAM*anti-CD55 mAb was compared with 17-1A conjugates with CVF or C3, and bispecific mAb were shown to be equally or more efficient in complement activation than the 17-1A-CVF or 17-1A-C3b conjugates. Therefore, 17-1A conjugates and anti-17-1A / EpCAM*anti-CD55 bispecific mAb may be promising immunotherapeutic agents for patients with colorectal cancer.

Inhibition of tumour growth and metastasis of human fibrosarcoma cells HT-1080 by monoclonal antibody BCD-F9

BCD-F9 is a murine IgG(2a) monoclonal antibody (mAb) that recognises a conformational epitope found on the surface of many human tumour cells. The aim of this study was to investigate the ability of BCD-F9 to recognise a variety of neoplastic cell lines and to test BCD-F9 in vivo for anticancer activity in subcutaneous (s.c.) and metastatic tumour models. Intravenous (i.v.) administration of BCD-F9 in CD-1 nude mice xenografted s.c. with human HT-1080 cells led to a significant inhibition of tumour growth. We demonstrated that BCD-F9 administrated i.v. significantly prolonged the life-span of CD-1 nude mice inoculated i.v. with the same tumour cell line that induces aggressive lung metastases in the untreated mice. We also investigated the antitumour activity of BCD-F9 in vitro in antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent complement-mediated cytotoxicity (ADCMC) assays. The effector cell subpopulations were obtained by macrophage stimulation (thioglycollate) or natural killer (NK) cell enrichment (negative selection). BCD-F9 was found to be effective in mediating tumour cell killing in vitro by ADCC and ADCMC mechanisms. These results suggest that the mAb BCD-F9 can have a potential use in immunotherapy for treatment of tumours of different origin.

Cancer immunotherapy: insights from transgenic animal models

A wide range of strategies in cancer immunotherapy has been developed in the last decade, some of which are currently being used in clinical settings. The development of these immunotherapeutical strategies has been facilitated by the generation of relevant transgenic animal models. Since the different strategies in experimental immunotherapy of cancer each aim to activate different immune system components, a variety of transgenic animals have been generated either expressing tumor associated, HLA, oncogenic or immune effector cell molecule proteins. This review aims to discuss the existing transgenic mouse models generated to study and develop cancer immunotherapy strategies and the variable results obtained. The potential of the various transgenic animal models regarding the development of anti-cancer immunotherapeutical strategies is evaluated.

Clinical experience with edrecolomab: a monoclonal antibody therapy for colorectal carcinoma

Edrecolomab (monoclonal antibody 17-1A) is a murine monoclonal antibody that recognizes the human tumor-associated antigen Ep-CAM (otherwise known as 17-1A). It is being developed for the adjuvant treatment of colorectal cancer. In a study of 189 patients with resected stage III colorectal cancer, treatment with edrecolomab resulted in a 32% increase in overall survival compared with no treatment (P<0.01) and decreased the tumor recurrence rate by 23% (P<0.04). In terms of safety, edrecolomab was well tolerated. Based on these study results, edrecolomab is currently under investigation in large multicenter phase III studies both as monotherapy and in combination with 5-fluorouracil-based chemotherapy versus chemotherapy alone for the treatment of stage III colon cancer. Although these studies are still ongoing, an interim analysis of safety data indicated that the combination of edrecolomab with chemotherapy is well tolerated. In addition, edrecolomab monotherapy demonstrated a favorable safety profile compared with chemotherapy. Edrecolomab is also currently being tested in large multicenter adjuvant phase III studies in stage II/III rectal cancer and stage II colon cancer. Edrecolomab represents a novel therapeutic approach and has the potential to become a treatment of choice as monotherapy in stage II colon cancer and in combination with chemotherapy in stage II/III rectal and stage III colon cancer.