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

Gene expression patterns distinguish breast carcinomas from normal breast tissues: the Malaysian context

Genomic and transcriptomic alterations that affect cellular processes, such as cell proliferation, differentiation, apoptosis and invasion, commonly occur in breast oncogenesis. Epidemiological evidence has proven that the risk of breast cancer predisposition varies among different ethnicities. This study aims to identify the transcriptome changes that commonly occur during the transition of normal breast epithelium to carcinoma in three local ethnic groups (Malays, Chinese and Indians). The gene expression patterns of 43 breast carcinomas with 43 patient-matched normal breast tissues were investigated using Affymetrix U133A GeneChip (containing 22,283 probe sets targeting approximately 18,400 different transcripts) and analyzed with GeneSpring GX10. Our findings revealed a total of 33 significantly differentially expressed genes, which showed>2-fold change at a 99.9% confidence interval level (p<0.001). The significantly differentially expressed genes included CD24, CD36, CD9, TACSTD1, TACSTD2, HBB, LEP, LPL, AKR1C1, AKR1C2 and AKR1C3. Our results indicate that the vast majority of gene expression changes, from normal breast epithelial to carcinoma, found in our three major ethnic populations are similar to those in the Caucasian population. Further study of the differentially expressed genes identified in our present study is needed to search for potential breast tumor biomarkers. This will eventually help to improve the therapeutic and treatment strategies for breast cancer patients in the future.

EpCAM is involved in maintenance of the murine embryonic stem cell phenotype

Epithelial cell adhesion molecule EpCAM is a transmembrane glycoprotein that is expressed on subsets of normal epithelia, numerous stem- and progenitor-type cells, and most carcinomas and highly overexpressed on cancer-initiating cells. The role of EpCAM in early development, particularly in stem-like cells, has remained unclear. Here, we show that the maintenance of self-renewal in murine embryonic stem (ES) cells depends on the high-level expression of EpCAM. Cultivation of ES cells under differentiation conditions in the absence of leukemia inhibitory factor (LIF) caused down-regulation of EpCAM along with decreased expression of cellular myelocytomatosis oncogene (c-Myc), Sex-determining region Y-Box 2, Octamer 3/4 (Oct3/4), and Stat3. As a consequence ES cells were morphologically differentiated and ceased to proliferate. RNA interference-mediated inhibition of EpCAM expression under self-renewal conditions resulted in quantitatively decreased proliferation, decreased Oct3/4, SSEA-1, and c-Myc expression, and diminished alkaline phosphatase activity. Conversely, exogenous expression of EpCAM partially compensated for the requirement of ES cells for LIF to retain a stem cell phenotype. Thus, murine EpCAM is a transmembrane protein, which is essential but by itself is not sufficient for maintenance of the ES cell phenotype.

Initial activation of EpCAM cleavage via cell-to-cell contact

BACKGROUND

Epithelial cell adhesion molecule EpCAM is a transmembrane glycoprotein, which is frequently over-expressed in simple epithelia, progenitors, embryonic and tissue stem cells, carcinoma and cancer-initiating cells. Besides functioning as a homophilic adhesion protein, EpCAM is an oncogenic receptor that requires regulated intramembrane proteolysis for activation of its signal transduction capacity. Upon cleavage, the extracellular domain EpEX is released as a soluble ligand while the intracellular domain EpICD translocates into the cytoplasm and eventually into the nucleus in combination with four-and-a-half LIM domains protein 2 (FHL2) and beta-catenin, and drives cell proliferation.

METHODS

EpCAM cleavage, induction of the target genes, and transmission of proliferation signals were investigated under varying density conditions using confocal laser scanning microscopy, immunoblotting, cell counting, and conditional cell systems.

RESULTS

EpCAM cleavage, induction of the target genes, and transmission of proliferation signals were dependent on adequate cell-to-cell contact. If cell-to-cell contact was prohibited EpCAM did not provide growth advantages. If cells were allowed to undergo contact to each other, EpCAM transmitted proliferation signals based on signal transduction-related cleavage processes. Accordingly, the pre-cleaved version EpICD was not dependent on cell-to-cell contact in order to induce c-myc and cell proliferation, but necessitated nuclear translocation. For the case of contact-inhibited cells, although cleavage of EpCAM occurred, nuclear translocation of EpICD was reduced, as were EpCAM effects.

CONCLUSION

Activation of EpCAM's cleavage and oncogenic capacity is dependent on cellular interaction (juxtacrine) to provide for initial signals of regulated intramembrane proteolysis, which then support signalling via soluble EpEX (paracrine).

Microdevice for the isolation and enumeration of cancer cells from blood

Cancer metastasis is the main attribute to cancer-related deaths. Furthermore, clinical reports have shown a strong correlation between the disease development and number of circulating tumor cells (CTCs) in the peripheral blood of cancer patients. Here, we present a label-free microdevice capable of isolating cancer cells from whole blood via their distinctively different physical properties such as deformability and size. The isolation efficiency is at least 80% for tests performed on breast and colon cancer cells. Viable isolated cells are also obtained which may give further insights to the understanding of the metastatic process. Contrasting with conventional biochemical techniques, the uniqueness of this microdevice lies in the mechanistic and efficient means of isolating viable cancer cells in blood. The microdevice has the potential to be used for routine monitoring of cancer development and cancer therapy in a clinical setting.

Trop2: a possible therapeutic target for late stage epithelial carcinomas

Trop2 is a cell-surface glycoprotein overexpressed in a variety of late stage epithelial carcinomas with low to no expression in normal tissues. Some of the important roles that Trop2 plays in epithelial cancers have recently been revealed. Trop2 overexpression is associated with decreased patient survival as well as increased tumor aggressiveness and metastasis. Its overexpression in metastatic tissue makes it a very attractive and potential therapeutic target for late stage disease. This protein can transduce an intracellular calcium signal and contains a conserved phosphatidylinositol 4,5-bisphosphate (PIP(2)) binding motif as well as a serine phosphorylation site which interacts with protein kinase C. This protein has recently being found to be expressed in cells with stem-like properties which allude to a potential role in progenitor cell biology. Further understanding of the signaling pathways involved with this molecule and its important role in metastasis will shed new light on the mechanism of Trop2 overexpression in late stage disease and could result in the development of new therapies targeting this widely overexpressed oncogene.

An open-label, randomized phase II study of adecatumumab, a fully human anti-EpCAM antibody, as monotherapy in patients with metastatic breast cancer

BACKGROUND

High-level expression of epithelial cell adhesion molecule (EpCAM) is associated with unfavorable prognosis in breast cancer. This study was designed to investigate two doses of the fully human IgG1 anti-EpCAM antibody adecatumumab (MT201) in patients with metastatic breast cancer (MBC).

METHODS

A total of 109 patients were stratified into high- and low-level EpCAM expression by immunohistochemical staining of primary tumors and subsequently randomly assigned to receive monotherapy with either high- (6 mg/kg every two weeks (q2w)) or low-dose adecatumumab (2 mg/kg/ q2w) until disease progression.

RESULTS

No complete or partial tumor responses could be confirmed by central RECIST assessment. The probability for tumor progression was significantly lower in patients receiving high-dose adecatumumab and expressing high levels of EpCAM (hazard ratio 0.43; P = 0.0057 versus low dose and low EpCAM). Three of 18 patients with highest EpCAM expression treated with adecatumumab developed new metastases up to week 6, compared with 14 of 29 patients with low EpCAM. Most frequent treatment-related adverse events (high dose/low dose) were chills (59%/20%), nausea (55%/18%), fatigue (39%/23%) and diarrhea (43%/7%).

CONCLUSIONS

Single-agent adecatumumab shows dose- and target-dependent clinical activity in EpCAM-positive MBC, albeit no objective tumor regression. Further investigation of adecatumumab in patients with EpCAM-overexpressing tumors and lower tumor burden is warranted.

Expression of an exogenous human Oct-4 promoter identifies tumor-initiating cells in osteosarcoma

We explored the nature of the tumor-initiating cell in osteosarcoma, a bone malignancy that predominately occurs in children. Previously, we observed expression of Oct-4, an embryonal transcriptional regulator, in osteosarcoma cell cultures and tissues. To examine the relationship between Oct-4 and tumorigenesis, cells from an osteosarcoma biopsy (OS521) were stably transfected with a plasmid containing the human Oct-4 promoter driving a green fluorescent protein (GFP) reporter to generate the transgenic line OS521Oct-4p. In culture, only approximately 24% of the OS521Oct-4p cells were capable of activating the transgenic Oct-4 promoter; yet, xenograft tumors generated in NOD/SCID mice contained approximately 67% GFP(+) cells, which selectively expressed the mesenchymal stem cell-associated surface antigens CD105 and ICAM-1. Comparison of the tumor-forming capacity of GFP-enriched and GFP-depleted cell fractions revealed that the GFP-enriched fractions were at least 100-fold more tumorigenic, capable of forming tumors at doses of <300 cells, and formed metastases in the lung. Clonal populations derived from a single Oct-4/GFP(+) cell were capable of forming tumors heterogeneous for Oct-4/GFP expression. These data are consistent with the cancer stem cell model of tumorigenesis in osteosarcoma and implicate a functional link between the capacity to activate an exogenous Oct-4 promoter and tumor formation. This osteosarcoma tumor-initiating cell appears highly prolific and constitutes a majority of the cell population in a primary xenograft tumor, which may provide a biological basis for the particular virulence of this type of cancer.

The epithelial cell adhesion molecule EpCAM is required for epithelial morphogenesis and integrity during zebrafish epiboly and skin development

The aberrant expression of the transmembrane protein EpCAM is associated with tumor progression, affecting different cellular processes such as cell-cell adhesion, migration, proliferation, differentiation, signaling, and invasion. However, the in vivo function of EpCAM still remains elusive due to the lack of genetic loss-of-function studies. Here, we describe epcam (tacstd) null mutants in zebrafish. Maternal-zygotic mutants display compromised basal protrusive activity and epithelial morphogenesis in cells of the enveloping layer (EVL) during epiboly. In partial redundancy with E-cadherin (Ecad), EpCAM made by EVL cells is further required for cell-cell adhesion within the EVL and, possibly, for proper attachment of underlying deep cells to the inner surface of the EVL, thereby also affecting deep cell epiboly movements. During later development, EpCAM per se becomes indispensable for epithelial integrity within the periderm of the skin, secondarily leading to disrupted morphology of the underlying basal epidermis and moderate hyper-proliferation of skin cells. On the molecular level, EVL cells of epcam mutant embryos display reduced levels of membranous Ecad, accompanied by an enrichment of tight junction proteins and a basal extension of apical junction complexes (AJCs). Our data suggest that EpCAM acts as a partner of E-cadherin to control adhesiveness and integrity as well as plasticity and morphogenesis within simple epithelia. In addition, EpCAM is required for the interaction of the epithelia with underlying cell layers.

Identifying tumor antigens in endocrine malignancies

Tumor antigens are surface molecules that are mostly cancer specific, often overexpressed and recognized by the immune system. Therefore, identifying tumor antigens is of key importance for developing new immunotherapies for incurable cancers. For endocrine malignancies, several different tumor-associated antigens have been described, including polypeptide hormones and/or vesicle-associated antigens in Th1-mediated autoimmune diseases. Other antigens have been identified by screening tumor DNA libraries. Furthermore, vaccination studies in humans and animal models have revealed a tumor-antigen-specific immunity and clinical responses with reduced tumor size. Here, we provide an overview of the recent progress achieved in identifying tumor antigens and predict how this knowledge can be used in the future for developing anti-tumor vaccinations.

EpCAM is overexpressed in gastric cancer and its downregulation suppresses proliferation of gastric cancer

PURPOSE

To identify the role of epithelial cellular adhesion molecule (EpCAM) in gastric cancer growth and explore the potential value of EpCAM monoclonal antibody as new therapeutic strategy for gastric cancer.

METHODS

The expression of EpCAM was determined by immunohistochemistry staining in gastric cancer tissues, RT-PCR and Western blot in cell lines. EpCAM expression in cell lines was downregulated by small interfering RNA. Then the effects of EpCAM on gastric cancer cell growth in vivo and in vitro were determined by MTT, FCM analysis, clone formation assay and tumor formation assay. Additionally, western blot was used to detect the effect of EpCAM on cell cycle-relevant factor cyclin D1.

RESULTS

EpCAM was found to be overexpressed in gastric cancer tissues and cell lines. Downregulation of EpCAM resulted in a decrease of cell proliferation and cell cycle arrest in AGS and SGC7901 cells, which had high endogenous EpCAM expression. EpCAM downregulation also suppressed tumor formation in nude mice. Moreover, EpCAM repression in gastric cancer cells could downregulate cyclin D1.

CONCLUSIONS

EpCAM was a potential oncogene and contributed to the growth of gastric cancer. Our data first provided compelling evidence of potential value of EpCAM in the therapy of gastric cancer in clinic.

Claudin-7 regulates EpCAM-mediated functions in tumor progression

EpCAM has been described as a therapeutically relevant tumor marker. We noted an interaction between EpCAM and the tight junction protein claudin-7 and here explored the nature of this interaction and its effect on EpCAM-mediated functions. The interaction between EpCAM and claudin-7 was defined in HEK293 cells transfected with rat claudin-7 and EpCAM cDNA. Deletions of the epidermal growth factor-like and the thyroglobin repeat domains of EpCAM or the cytoplasmic domain of EpCAM or claudin-7 did not prevent the EpCAM-claudin-7 association. A chimeric EpCAM molecule with an exchange of the cytoplasmic and transmembrane domains and an EpCAM molecule with point mutations in an AxxxG motif in the transmembrane region do not associate with claudin-7. HEK cells and the rat pancreatic tumor line BSp73AS, transfected with (mutated) EpCAM and claudin-7 cDNA, revealed that the association of both molecules severely alters the functional activity of EpCAM. Claudin-7-associated EpCAM is recruited into tetraspanin-enriched membrane microdomains (TEM). The TEM-located claudin-7-EpCAM complex supports proliferation accompanied by sustained extracellular signal-regulated kinase-1/2 phosphorylation, up-regulation of antiapoptotic proteins, and drug resistance, but not EpCAM-mediated cell-cell adhesion. Enhanced motility may be supported by colocalization of claudin-7 with actin bundles, which is only seen in EpCAM-claudin-7-expressing cells. The EpCAM-claudin-7 complex strongly promotes tumorigenicity, accelerates tumor growth, and supports ascites production and thymic metastasis formation. High expression of the tumor marker EpCAM is frequently associated with poor prognosis, which could well rely on the EpCAM-claudin-7 association that prohibits EpCAM-mediated cell-cell adhesion but promotes migration, proliferation, apoptosis resistance, and tumorigenicity.

Dual expression lentiviral vectors for concurrent RNA interference and rescue

RNA interference (RNAi) is a powerful new tool for the selective ablation of gene expression, facilitating loss-of-function studies. However, appropriate controls are considered essential to confirm the specificity of RNAi experiments. The most stringent control is rescue of the target gene in a form that is refractory to RNAi. To facilitate rescue of the target gene, we have created improved dual expression lentiviral vectors with the ability to simultaneously drive expression of a shRNA for RNA interference and a rescue transgene in a single vector system. In proof-of-principle experiments, we ablated more than 90% of target gene expression by targeting either the open reading frame, or the 3' UTR region. Target gene expression was successfully rescued with a cDNA containing silent third-codon point mutations in the targeted region or with native cDNA when the 3' UTR was targeted. Finally, expression of the rescue transgene can be manipulated by positional cloning and appropriate promoter selection. The dual expression lentiviral vectors described here represent a versatile strategy for confirming the integrity of RNAi experiments and may facilitate functional analyses even in the absence of an established gain-of-function model system.

EpCAM: another surface-to-nucleus missile

The epithelial-specific cell adhesion molecule (EpCAM) modulates cell adhesion and proliferation. Its overexpression correlates with tumor cell proliferation, and EpCAM is a therapeutic target. In the February issue of Nature Cell Biology, Maetzel et al. demonstrate that proliferative responses to EpCAM require regulated intramembrane proteolysis and a nucleocytoplasmic intracellular domain fragment.

Transcriptional repression of epithelial cell adhesion molecule contributes to p53 control of breast cancer invasion

p53 is a tumor suppressor gene with well-characterized roles in cell cycle regulation, apoptosis, and maintenance of genome stability. Recent evidence suggests that p53 may also contribute to the regulation of migration and invasion. Epithelial cell adhesion molecule (EpCAM) is a transmembrane glycoprotein that is overexpressed in the majority of human epithelial carcinomas, including breast and colorectal carcinomas. We show by chromatin immunoprecipitation assays that p53 interacts with a candidate p53 binding site within the EpCAM gene. p53-mediated transcriptional repression of EpCAM was confirmed in gain-of-function and loss-of-function experimental systems. Induction of wild-type p53 was associated with a significant dose-dependent decrease in EpCAM expression; conversely, specific ablation of p53 was associated with a significant increase in EpCAM expression. At the functional level, specific ablation of p53 expression is associated with increased breast cancer invasion, and this effect is abrogated by concomitant specific ablation of EpCAM expression. Taken together, these biochemical and functional data are the first demonstration that (a) wild-type p53 protein binds to a response element within the EpCAM gene and negatively regulates EpCAM expression, and (b) transcriptional repression of EpCAM contributes to p53 control of breast cancer invasion.

A genome-wide expression analysis identifies a network of EpCAM-induced cell cycle regulators

Expression of the epithelial cell adhesion molecule EpCAM is upregulated in a variety of carcinomas. This antigen is therefore explored in tumour diagnosis, and clinical trials have been initiated to examine EpCAM-based therapies. Notably, the possible intracellular effects and signalling pathways triggered by EpCAM-specific antibodies are unknown. Here, we show treatment of the mouse lung carcinoma cell line A2C12, of the human lung carcinoma cell line A549 and the human colorectal cell line Caco-2 with the monoclonal EpCAM antibody G8.8 to cause dose dependently an increase in cell proliferation, as determined by the MTS and the 5′-bromo-2′-deoxyuridine (BrdU) labelling assay. Furthermore, a genome-wide approach identified networks of regulated genes, most notably cell cycle regulators, upon treatment with an EpCAM-specific antibody. Indeed, changes in the expression of cell cycle regulators agreed well with the BrdU labelling data, and an analysis of differentially expressed genes revealed the processes with the strongest over-representation of modulated genes, for example, cell cycle, cell death, cellular growth and proliferation, and cancer. These data suggest that EpCAM is involved in signal transduction triggering several intracellular signalling pathways. Knowing EpCAM signalling pathways might lead to a reassessment of EpCAM-based therapies.

Expression of EpCAM is up-regulated during regeneration of renal epithelia

The human epithelial cell adhesion molecule (hEpCAM) is involved in epithelial morphogenesis and repair of epithelial tissues. We hypothesized that changes in hEpCAM expression in vivo correlate with regeneration of renal epithelia after ischaemia/reperfusion injury (IRi). Unilateral IRi was performed on kidneys of hEpCAM transgenic mice. Changes in hEpCAM expression were investigated by quantitative RT-PCR in renal cortex and medulla dissected by laser dissection microscopy and expression patterns of hEpCAM in regenerating kidneys were assessed by immunohistochemistry. The mechanism of hEpCAM promoter activation was investigated in vitro, by real-time bioluminescent imaging in HK-2 cells and in primary tubular epithelial cells (PTECs) subjected to hypoxia and reoxygenation. In vivo, the transcription of the human epcam gene significantly increased in the renal cortex during tubular re-epithelialization (p < 0.01). Moreover, the number of tubuli that expressed hEpCAM protein more than doubled in the renal cortex during regeneration. De novo expression of hEpCAM was detected in the S1 segments of proximal tubuli. Under hypoxic conditions in vitro, activity of the hEpCAM promoter was up-regulated two-fold in the HK-2 proximal epithelial cell line. Moreover, both in primary proximal epithelial cells and in HK-2 cells, hEpCAM protein expression was increased after hypoxia and reoxygenation. The significant up-regulation of hEpCAM during post-ischaemic renal regeneration in vivo and during in vitro hypoxia indicates that hEpCAM expression is associated with renal regeneration.

Prognostic effect of epithelial cell adhesion molecule overexpression in untreated node-negative breast cancer

PURPOSE

Epithelial cell adhesion molecule (Ep-CAM) recently received increased attention not only as a prognostic factor in breast cancer but also as a potential target for immunotherapy. We examined Ep-CAM expression in 402 consecutive node-negative breast cancer patients with long-term follow-up not treated in the adjuvant setting.

EXPERIMENTAL DESIGN

Ep-CAM expression was evaluated by immunostaining. Its prognostic effect was estimated relative to overexpression/amplification of HER-2, histologic grade, tumor size, age, and hormone receptor expression.

RESULTS

Ep-CAM status was positive in 106 (26.4%) patients. In multivariate analysis, Ep-CAM status was associated with disease-free survival independent of age, pT stage, histologic grade, estrogen receptor (ER), progesterone receptor (PR), as well as HER2 status (P = 0.028; hazard ratio, 1.60; 95% confidence interval, 1.05-2.44). Recently, so-called triple-negative (HER-2, ER, and PR) breast cancer has received increased attention. We noticed a similar association of Ep-CAM with disease-free survival in the triple-negative group as for the entire cohort.

CONCLUSION

In this study of untreated breast cancer patients, Ep-CAM overexpression was associated with poor survival in the entire cohort and in the subgroup of triple-negative breast cancer. This suggests that Ep-CAM may be a well-suited target for specific therapies particularly in HER-2-, ER-, and PR-negative tumors.

AKT alters genome-wide estrogen receptor alpha binding and impacts estrogen signaling in breast cancer

Estrogen regulates several biological processes through estrogen receptor alpha (ERalpha) and ERbeta. ERalpha-estrogen signaling is additionally controlled by extracellular signal activated kinases such as AKT. In this study, we analyzed the effect of AKT on genome-wide ERalpha binding in MCF-7 breast cancer cells. Parental and AKT-overexpressing cells displayed 4,349 and 4,359 ERalpha binding sites, respectively, with approximately 60% overlap. In both cell types, approximately 40% of estrogen-regulated genes associate with ERalpha binding sites; a similar percentage of estrogen-regulated genes are differentially expressed in two cell types. Based on pathway analysis, these differentially estrogen-regulated genes are linked to transforming growth factor beta (TGF-beta), NF-kappaB, and E2F pathways. Consistent with this, the two cell types responded differently to TGF-beta treatment: parental cells, but not AKT-overexpressing cells, required estrogen to overcome growth inhibition. Combining the ERalpha DNA-binding pattern with gene expression data from primary tumors revealed specific effects of AKT on ERalpha binding and estrogen-regulated expression of genes that define prognostic subgroups and tamoxifen sensitivity of ERalpha-positive breast cancer. These results suggest a unique role of AKT in modulating estrogen signaling in ERalpha-positive breast cancers and highlights how extracellular signal activated kinases can change the landscape of transcription factor binding to the genome.

Molecular imaging with nanoparticles: giant roles for dwarf actors

Molecular imaging, first developed to localise antigens in light microscopy, now encompasses all imaging modalities including those used in clinical care: optical imaging, nuclear medical imaging, ultrasound imaging, CT, MRI, and photoacoustic imaging. Molecular imaging always requires accumulation of contrast agent in the target site, often achieved most efficiently by steering nanoparticles containing contrast agent into the target. This entails accessing target molecules hidden behind tissue barriers, necessitating the use of targeting groups. For imaging modalities with low sensitivity, nanoparticles bearing multiple contrast groups provide signal amplification. The same nanoparticles can in principle deliver both contrast medium and drug, allowing monitoring of biodistribution and therapeutic activity simultaneously (theranostics). Nanoparticles with multiple bioadhesive sites for target recognition and binding will be larger than 20 nm diameter. They share functionalities with many subcellular organelles (ribosomes, proteasomes, ion channels, and transport vesicles) and are of similar sizes. The materials used to synthesise nanoparticles include natural proteins and polymers, artificial polymers, dendrimers, fullerenes and other carbon-based structures, lipid-water micelles, viral capsids, metals, metal oxides, and ceramics. Signal generators incorporated into nanoparticles include iron oxide, gadolinium, fluorine, iodine, bismuth, radionuclides, quantum dots, and metal nanoclusters. Diagnostic imaging applications, now appearing, include sentinal node localisation and stem cell tracking.

Lysis of cancer cells by autologous T cells in breast cancer pleural effusates treated with anti-EpCAM BiTE antibody MT110

In the present study, the efficacy of a new drug, i.e. the bispecific single-chain antibody MT110 targeting the epithelial antigen EpCAM and the T-cell antigen CD3 was tested ex vivo in malignant pleural effusions (MPEs). EpCAM+ epithelial cells were found in 78% of the MPEs (n = 18). Ex vivo treatment of seven MPEs resulted in a dose-dependent specific lysis of 37 +/- 27% (+/- SD) EpCAM+ cells with 10 ng/ml (P = 0.03) and 57 +/- 29.5% EpCAM+ cells with 1,000 ng/ml MT110 (P = 0.016) after 72 h. As a prerequisite for redirected lysis, stimulation of the autologous CD4+ and CD8+ cells in MPE by 1,000 ng/ml MT110 resulted in 21 +/- 17% CD4+/CD25+ and 29.4 +/- 22% CD8+/CD25+ cells (P = 0.016, respectively) after 72 h. This was confirmed by a 22-fold release of TNF-alpha and 230-fold release of IFN-gamma (1,000 ng/ml, 48 h, P = 0.03, respectively). Thus, relapsed breast cancer patients resistant to standard treatment might benefit from targeted therapy using MT110.

Antibody-cytokine fusion proteins: applications in cancer therapy

BACKGROUND

Antibody-cytokine fusion proteins consist of cytokines fused to an antibody to improve antibody-targeted cancer immunotherapy. These molecules have the capacity to enhance the tumoricidal activity of the antibodies and/or activate a secondary antitumor immune response.

OBJECTIVE

To review the strategies used to develop antibody-cytokine fusion proteins and their in vitro and in vivo properties, including preclinical and clinical studies focusing on IL-2, IL-12 and GM-CSF.

METHODS

Articles were found by searching databases such as PubMed and Clinical Trials of the US National Institutes of Health.

RESULTS/CONCLUSION

Multiple antibody-cytokine fusion proteins have demonstrated significant antitumor activity as direct therapeutics or as adjuvants of cancer vaccines in preclinical studies, paving the way for their clinical evaluation.

Decreased expression of Ep-CAM protein is significantly associated with the progression and prognosis of oral squamous cell carcinomas in Taiwan

BACKGROUND

The epithelial cell adhesion molecule (Ep-CAM) is involved in cell signaling, migration, proliferation, cell-cycle regulation, and cancer metastasis.

METHODS

This study used an immunohistochemical technique to examine the expression of Ep-CAM protein in 84 specimens of oral squamous cell carcinoma (OSCC), 98 specimens of oral epithelial dysplasia (OED, 31 mild, 41 moderate, and 26 severe OED cases), and 15 specimens of normal oral mucosa (NOM).

RESULTS

We found that the mean Ep-CAM labeling indices (LIs) decreased significantly from NOM (80 +/- 18%) and mild OED (76 +/- 14%) through moderate OED (66 +/- 22%) and severe OED (55 +/- 20%) to OSCC samples (46 +/- 16%, P < 0.001). A significant correlation was found between the lower mean Ep-CAM LI and OSCCs with larger tumor size (P = 0.003), positive lymph node metastasis (P = 0.022), more advanced clinical stages (P < 0.001), cancer recurrence (P = 0.021), or extracapsular spread of lymph node (P = 0.015). However, only Ep-CAM LI < 50% (P < 0.0001) was identified as an independent unfavorable prognosis factor by multivariate analyses with Cox proportional hazard regression model. Kaplan-Meier curve showed that OSCC patients with an Ep-CAM LI < 50% had a significantly poorer cumulative survival than those with an Ep-CAM LI > or = 50% (P < 0.00001, log-rank test).

CONCLUSIONS

We conclude that the decreased expression of Ep-CAM protein is an early event in oral carcinogenesis. The Ep-CAM LI in OSCC samples can predict the progression of OSCCs and the survival of OSCC patients.

Detection of mammaglobin mRNA in peripheral blood is associated with high grade breast cancer: interim results of a prospective cohort study

BACKGROUND

We sought to examine the detection rate of cancer cells in peripheral blood (PBL) and in bone marrow (BM) using an established 7-gene marker panel and evaluated whether there were any definable associations of any individual gene with traditional predictors of prognosis.

METHODS

Patients with T1-T3 primary breast cancer were enrolled into a prospective, multi-institutional cohort study. In this interim analysis 215 PBL and 177 BM samples were analyzed by multimarker, real-time RT-PCR analysis designed to detect circulating and disseminated breast cancer cells.

RESULTS

At a threshold of three standard deviations from the mean expression level of normal controls, 63% (136/215) of PBL and 11% (19/177) of BM samples were positive for at least one cancer-associated marker. Marker positivity in PBL demonstrated a statistically significant association with grade II-III (vs. grade I; p = 0.0083). Overexpression of the mammaglobin (mam) gene alone had a statistically significant association with high tumor grade (p = 0.0315), and showed a trend towards ER-negative tumors and a high risk category. There was no association between marker positivity in PBL and the pathologic (H&E) and/or molecular (RT-PCR) status of the axillary lymph nodes (ALN).

CONCLUSION

This study suggests that molecular detection of circulating cancer cells in PBL detected by RT-PCR is associated with high tumor grade and specifically that overexpression of the mam gene in PBL may be a poor prognostic indicator. There was no statistically significant association between overexpression of cancer-associated genes in PBL and ALN status, supporting the concept of two potentially separate metastatic pathways.

Therapeutic window of MuS110, a single-chain antibody construct bispecific for murine EpCAM and murine CD3

EpCAM (CD326) is one of the most frequently and highly expressed tumor-associated antigens known and recently has also been found on cancer stem cells derived from human breast, colon, prostate, and pancreas tumors. However, like many other tumor-associated antigens used for antibody-based immunotherapeutic approaches, EpCAM is expressed on normal tissues including epithelia of pancreas, colon, lung, bile ducts, and breast. To assess the therapeutic window of an EpCAM/CD3-bispecific single-chain antibody construct of the bispecific T-cell engager (BiTE) class, we constructed murine surrogate of MT110 (muS110) from single-chain antibodies specific for murine EpCAM and CD3 antigens. Immunhistochemical analysis showed that, with minor differences, the expression of EpCAM protein on a large variety of tissues from man and mouse was similar with respect to distribution and level. MuS110 exhibited significant antitumor activity at as low as 5 microg/kg in both syngeneic 4T1 orthotopic breast cancer and CT-26 lung cancer mouse models. Dosing of muS110 for several weeks up to 400 microg/kg by intraanimal dose escalation was still tolerated, indicating existence of a significant therapeutic window for an EpCAM-specific BiTE antibody in mice. MuS110 was found to have similar in vitro characteristics and in vivo antitumor activity as MT110, a human EpCAM/human CD3-bispecific BiTE antibody that currently is in formal preclinical development.

Activation of hepatic stem cell marker EpCAM by Wnt-beta-catenin signaling in hepatocellular carcinoma

The heterogeneous nature of hepatocellular carcinoma (HCC) and the lack of appropriate biomarkers have hampered patient prognosis and treatment stratification. Using a gene expression profiling approach, we recently identified a novel prognostic HCC subtype that resembles hepatic progenitor cells with the activation of stem cell markers and Wnt-beta-catenin signaling, based on EpCAM (epithelial cell adhesion molecule, a hepatic stem cell marker) expression. In this study, we investigated whether the activation of the Wnt-beta-catenin pathway regulates EpCAM expression. We found that nuclear accumulation of beta-catenin induced, whereas the degradation of beta-catenin or inhibition of Tcf/beta-catenin complex formation reduced EpCAM gene expression in cultured normal human hepatocytes and HCC cell lines. We identified two Tcf binding elements in the EpCAM promoter that specifically bound to Tcf-4 in an electrophoretic mobility shift assay. EpCAM promoter luciferase activity was down-regulated by the degradation of beta-catenin or inhibition of Tcf/beta-catenin complex formation. Furthermore, we found that EpCAM-positive HCC is much more sensitive to Tcf/beta-catenin binding inhibitors than EpCAM-negative HCC in vitro. Taken together, our data indicate that EpCAM is a Wnt-beta-catenin signaling target gene and may be used to facilitate HCC prognosis by enabling effective stratification of patients with predicted pharmacologic responses to Wnt-beta-catenin signaling antagonists.

Spatial and temporal expression patterns of the epithelial cell adhesion molecule (EpCAM/EGP-2) in developing and adult kidneys

BACKGROUND

The epithelial cell adhesion molecule (EpCAM) is expressed by most epithelia and is involved in processes fundamental for morphogenesis, including cell-cell adhesion, proliferation, differentiation, and migration. Previously, a role for EpCAM in pancreatic morphogenesis was confirmed in vitro. Furthermore, changes in the EpCAM expression pattern were found in developing lung and thymus and in the regenerating liver. Therefore, EpCAM was proposed to be a morphoregulatory molecule.

METHODS

Using immunohistochemistry, the expression pattern of human and murine homologues of EpCAM was characterized in adult and embryonic kidneys from humans and human-EpCAM (hEpCAM)-transgenic mice.

RESULTS

EpCAM expression was found in the ureteric bud throughout nephrogenesis. EpCAM was not expressed in the metanephric mesenchyme. In comma- and S-shaped bodies, both metanephric mesenchyme derived structures, EpCAM expression appeared by E13.5. In adult kidneys, most epithelia expressed varying levels of EpCAM, as confirmed by double staining for human EpCAM and segment-specific nephron markers. Podocytes were EpCAM negative. At the cellular level, the EpCAM expression shifted from apical in embryonic to basolateral in adult kidneys.

CONCLUSIONS

The spatiotemporal expression pattern of EpCAM changes during nephrogenesis. In the adult kidney, the expression varies markedly along the nephron. These data provide a basis for further studies on EpCAM in developing and adult kidneys.

EpCAM homologues exhibit epithelial-specific but different expression patterns in the kidney

The Epithelial Cell Adhesion Molecule (EpCAM) is expressed virtually on normal epithelia in vertebrates. Among different species, the amino acid sequence of EpCAM is highly homologous, indicating that EpCAM is an evolutionary conserved protein. However, differences in the expression pattern of EpCAM homologues have been reported. We hypothesized that differences in expression pattern might be related to the promoter organization of the respective EpCAM homologues. Therefore, we here compared the promoter region of the mouse and human EpCAM homologues. In addition, we compared the expression pattern of the human and murine EpCAM homologues in the hEpCAM transgenic mouse. In silico analysis of EpCAM homologues revealed that the amino acid sequence as well as the domain structure is highly conserved throughout different vertebrates. In silico analysis of the promoter region identified that the human and mouse EpCAM promoters share a low homology. In agreement with this low homology, the murine and human EpCAM promoter contains only a few common transcription factor binding sites. Nevertheless, immunohistochemcial analysis of the expression of human and murine EpCAM in lung, colon, and kidney of the hEpCAM transgenic mouse identified that expression of both homologues is restricted to epithelial cells in these organs. Moreover, in lung and colon the human and murine homologues of EpCAM were co-expressed. In contrast, the EpCAM homologues were only sporadically co-expressed in renal epithelia, although they were distributed similarly along the nephronic segments. Together, these findings indicate an overall conserved regulatory mechanism that ensures epithelial expression of EpCAM homologues, despite the low promoter homology. Furthermore, the fact that murine epithelia express the human homologue of EpCAM indicates that the mouse has transcription factors required for human EpCAM expression.

Clinicopathologic significance of EpCAM expression in squamous cell carcinoma of the tongue and its possibility as a potential target for tongue cancer gene therapy

Epithelial adhesion molecule (EpCAM) is a transmembrane glycoprotein involved in intercellular adhesion. In particular, EpCAM appears to be overexpressed by the majority of human epithelial carcinomas, including colorectal, breast, head and neck, and hepatic carcinomas. We therefore hypothesized that EpCAM would be a good molecular target for cancer gene therapy. EpCAM protein expression in 48 primary tongue cancers and 10 normal oral mucosa was evaluated using anti-EpCAM immunohistochemistry, and correlation was examined with the clinicopathologic factors. In four human tongue cancer cell lines (SAS, HSC-2, OSC19 and OSC20), we investigated EpCAM expression by reverse transcription-polymerase chain reaction (RT-PCR). The invasive potential of cancer cells was evaluated using Matrigel invasion assay. Moreover, the effect of EpCAM inhibition was analyzed using RNA interference (RNAi). EpCAM overexpression was detected in 30 of 48 tongue cancers (62.5%), and was significantly higher in primary squamous cell carcinoma (SCC) of the tongue than in normal oral mucosa. The expression of EpCAM was significantly associated with tumor size, regional lymph node metastasis, histological differentiation and invasion pattern. Cancer cell lines with higher EpCAM expression had more invasive potential. Moreover, RNAi-mediated EpCAM reduction decreased the invasion potential and proliferation activity. These results indicated that the overexpression of EpCAM was correlated with a more aggressive phenotype of tongue cancer. Moreover, we suggested that EpCAM could be a molecular target, and that RNAi targeting EpCAM could be useful for tongue cancer gene therapy.

Human breast cancer stem cell markers CD44 and CD24: enriching for cells with functional properties in mice or in man?

Identification of breast cancer stem cells as the cells within breast tumors that have the ability to give rise to cells that make up the bulk of the tumor mass has shifted the focus of cancer research. However, there is still much debate concerning the unique nature of the markers that distinguish cancer stem cells in the breast. As such, understanding whether CD44+/CD24- breast cancer cells are merely more successful in overcoming an engraftment incompatibility that exists when injecting human cells into the mouse adipose tissue or are indeed bona fide cancer stem cells is of great importance.

Engineering zinc finger protein transcription factors to downregulate the epithelial glycoprotein-2 promoter as a novel anti-cancer treatment

Zinc finger protein transcription factors (ZFP-TFs) are emerging as powerful novel tools for the treatment of many different diseases. ZFPs are DNA-binding motifs and consist of modular zinc finger domains. Each domain can be engineered to recognize a specific DNA triplet, and stitching six domains together results in the recognition of a gene-specific sequence. Inhibition of gene expression can be achieved by fusing a repressor domain to these DNA-binding motifs. In this study, we engineered ZFP-TFs to downregulate the activity of the epithelial glycoprotein-2 (EGP-2) promoter. The protein EGP-2 is overexpressed in a wide variety of cancer types and EGP-2 downregulation has been shown to result in a decreased oncogenic potential of tumor cells. Therefore, downregulation of EGP-2 expression by ZFP-TFs provides a novel anti-cancer therapeutic. Using a straightforward strategy, we engineered a 3-ZFP that could bind a 9 bp sequence within the EGP-2 promoter. After the addition of a repressor domain, this 3-ZFP-TF could efficiently downregulate EGP-2 promoter activity by 60%. To demonstrate the flexibility of this technology, we coupled an activation domain to the engineered ZFP, resulting in a nearly 200% increase in EGP-2 promoter activity. To inhibit the endogenous EGP-2 promoter, we engineered 6-ZFP-TFs. Although none of the constructed ZFP-TFs could convincingly modulate the endogenous promoter, efficient and specific inhibition of the exogenous promoter was observed. Overall, ZFP-TFs are versatile bi-directional modulators of gene expression and downregulation of EGP-2 promoter activity using ZFP-TFs can ultimately result in a novel anti-cancer treatment.

Novel antibodies as anticancer agents

In recent years antibodies, whether generated by traditional hybridoma technology or by recombinant DNA strategies, have evolved from Paul Ehrlich's 'magic bullets' to a modern age 'guided missile'. In the recent years of immunologic research, we are witnessing development in the fields of antigen screening and protein engineering in order to create specific anticancer remedies. The developments in the field of recombinant DNA, protein engineering and cancer biology have let us gain insight into many cancer-related mechanisms. Moreover, novel techniques have facilitated tools allowing unique distinction between malignantly transformed cells, and regular ones. This understanding has paved the way for the rational design of a new age of pharmaceuticals: monoclonal antibodies and their fragments. Antibodies can select antigens on both a specific and a high-affinity account, and further implementation of these qualities is used to target cancer cells by specifically identifying exogenous antigens of cancer cell populations. The structure of the antibody provides plasticity resonating from its functional sites. This review will screen some of the many novel antibodies and antibody-based approaches that are being currently developed for clinical applications as the new generation of anticancer agents.

Frontotemporal clear cell meningioma. Report of 3 cases

Clear cell meningioma (CCM) is an uncommon meningioma. Some cases have been reported, and the localization of most of them is the spinal region. We present 3 cases of CCMs in the frontotemporal lobes. All cases were postmenopausal women with a history of arterial hypertension and uterine leiomyomatosis. The radiologic appearance in 2 cases was similar to that of dural hematomas, and in 1 case, the imaging study was consistent with the diagnosis of meningioma. On histologic examination, there were sheets of glycogenated polygonal cells with abundant clear cytoplasm and round, uniform, bland appearing nuclei. Numerous hyalinized blood vessels and collagenous stroma with fibrillary appearance were present in 2 cases. They were immunoreactive to epithelial membrane antigen, epithelial cell adhesion molecule, and progesterone receptors. However, 2 cases showed weak and focal reaction to Her-2/neu. In our knowledge, some cases of CCMs have been reported and no immunoexpression has been noted with those markers used. These cases illustrate a rare variant of meningioma in the frontotemporal lobes and their immunohistochemical profiles. Differential diagnosis is discussed.

Characterisation of the new EpCAM-specific antibody HO-3: implications for trifunctional antibody immunotherapy of cancer

Epithelial cell adhesion molecule EpCAM is a transmembrane glycoprotein that is frequently overexpressed in a variety of carcinomas. This pan-carcinoma antigen has served as the target for a plethora of immunotherapies. Innovative therapeutic approaches include the use of trifunctional antibodies (trAbs) that recruit and activate different types of immune effector cells at the tumour site. The trAb catumaxomab has dual specificity for EpCAM and CD3. In patients with malignant ascites, catumaxomab significantly increased the paracentesis-free interval, corroborating the high efficacy of this therapeutic antibody. Here, we characterised the monoclonal antibody (mAb) HO-3, that is, the EpCAM-binding arm of catumaxomab. Peptide mapping indicated that HO-3 recognises a discontinuous epitope, having three binding sites in the extracellular region of EpCAM. Studies with glycosylation-deficient mutants showed that mAb HO-3 recognised EpCAM independently of its glycosylation status. High-affinity binding was not only detected for mAb HO-3, but also for the monovalent EpCAM-binding arm of catumaxomab with an excellent K_D of 5.6 × 10⁻¹⁰ M. Furthermore, trAb catumaxomab was at least a 1000-fold more effective in eliciting the eradication of tumour cells by effector peripheral blood mononuclear cells compared with mAb HO-3. These findings suggest the great therapeutic potential of trAbs and clearly speak in favour of EpCAM-directed cancer immunotherapies.

Epithelial cell adhesion molecule: more than a carcinoma marker and adhesion molecule

The epithelial cell adhesion molecule (EpCAM, CD326) is a glycoprotein of approximately 40 kd that was originally identified as a marker for carcinoma, attributable to its high expression on rapidly proliferating tumors of epithelial origin. Normal epithelia express EpCAM at a variable but generally lower level than carcinoma cells. In early studies, EpCAM was proposed to be a cell-cell adhesion molecule. However, recent insights revealed a more versatile role for EpCAM that is not limited only to cell adhesion but includes diverse processes such as signaling, cell migration, proliferation, and differentiation. Cell surface expression of EpCAM may actually prevent cell-cell adhesion. Here, we provide a comprehensive review of the current knowledge on EpCAM biology in relation to other cell adhesion molecules. We discuss the implications of the newly identified functions of EpCAM in view of its prognostic relevance in carcinoma, inflammatory pathophysiology, and tissue development and regeneration as well as its role in normal epithelial homeostasis.

EpCAM expression in squamous cell carcinoma of the oral cavity: frequency and relationship to clinicopathologic features

This retrospective study was designed to investigate the prognostic significance of EpCAM expression in human oral squamous cell carcinoma on a long-term follow-up. EpCAM expression was examined immunohistochemically on a tissue microarray (TMA) of paraffin embedded tissue specimens from 77 consecutive patients who underwent surgical treatment for squamous cell carcinoma of the oral cavity in the period between 1980 and 1997 at the Department of Craniomaxillofacial and Oral Surgery, Innsbruck Medical University. High EpCAM expression was found in 17 (22.1%) of the tumor samples. Using Kaplan-Meier analysis no correlation of EpCAM overexpression was observed with conventional clinicopathologic features in this patient cohort. Taken together, these data suggest that EpCAM might become an attractive treatment target in a subgroup of patients with OSCC.

EpCAM an immunotherapeutic target for gastrointestinal malignancy: current experience and future challenges

Despite advances in surgery and adjuvant regimes, gastrointestinal malignancy remains a major cause of neoplastic mortality. Immunotherapy is an emerging and now successful treatment modality for numerous cancers that relies on the manipulation of the immune system and its effector functions to eradicate tumour cells. The discovery that the pan-epithelial homotypic cell adhesion molecule EpCAM is differentially expressed on gastrointestinal tumours has made this a viable target for immunotherapy. Clinical trials using naked anti EpCAM antibody, immunoconjugates, anti-idiotypic and dendritic cell vaccines have met variable success. The murine IgG2a Edrecolomab was shown to reduce mortality and morbidity at a level slightly lower than treatment with 5FU and Levamisole when administered to patients with advanced colorectal carcinoma in a large randomised controlled trial. Fully human and trifunctional antibodies that specifically recruit CD3-positive lymphocytes are now being tested clinically in the treatment of minimal residual disease and ascites. Although clinical trials are in their infancy, the future may bring forth an EpCAM mediated approach for the effective activation and harnessing of the immune system to destroy a pathological aberrance that has otherwise largely escaped its attention.

EpCAM (CD326) finding its role in cancer

Although epithelial cell adhesion/activating molecule (EpCAM/CD326) is one of the first tumour-associated antigens identified, it has never received the same level of attention as other target proteins for therapy of cancer. It is also striking that ever since its discovery in the late 1970s the actual contribution of EpCAM to carcinogenesis remained unexplored until very recently. With a First International Symposium on EpCAM Biology and Clinical Application this is now changing. Key topics discussed at the meeting were the frequency and level of EpCAM expression on various cancers and its prognostic potential, the role of EpCAM as an oncogenic signalling molecule for cancer cells, recent progress on EpCAM-directed immunotherapeutic approaches in clinical development and the interaction of EpCAM with other proteins, which may provide a basis for a therapeutic window and repression of its growth-promoting signalling in carcinoma. Future research on EpCAM may benefit from a unified nomenclature and more frequent exchange among those who have been working on this cancer target during the past 30 years and will do so in the future.

DNA methylation and histone modification regulate silencing of epithelial cell adhesion molecule for tumor invasion and progression

Epithelial cell adhesion molecule (Ep-CAM) is believed to have a critical role in carcinogenesis and cell proliferation. However, the association of Ep-CAM with cancer invasion and progression is less clear. We found that Ep-CAM was highly expressed on low-invasive cells compared with highly invasive cells. Forced expression of Ep-CAM decreased cancer invasiveness, and silencing Ep-CAM expression elevated cancer invasiveness. Ep-CAM expression was associated with promoter methylation. Treatment with a demethylating agent, and/or the histone deacetylase inhibitor reactivated Ep-CAM expression in Ep-CAM-negative cells and inhibited cancer invasiveness. Using a promoter-reporter construct, we demonstrated methylation of the promoter fragment drive Ep-CAM-silenced transcription. Additionally, silenced Ep-CAM gene in cancer cells was enriched for hypermethylated histone 3 lysine 9. When unmethylated and active, this promoter was associated with acetylated histone 3 lysine 9. Furthermore, we observed an increased association of Ep-CAM promoter with repression components as tumor invasiveness increased. In cancer tissues, Ep-CAM expression significantly correlated with tumor progression and associated with promoter methylation. Our data support the idea that modulation of Ep-CAM plays a pivotal role in tumor invasion and progression. Moreover, aberrant DNA methylation of Ep-CAM is implicated in enhancing invasive/metastatic proclivity of tumors.

Expression of EpCAM in uveal melanoma

Background

Uveal melanoma (UM) is the most common primary intraocular malignant tumor in adults, and nearly 40% of UM will develop metastasis that will ultimately lead to death. The Epithelial Cell Adhesion Molecule (EpCAM) is a type I transmembrane glycoprotein expressed by carcinomas of head and neck, ovary, colon, breast, kidney and lung. Recently, antibodies against EpCAM such as Edrecolomab and Catumaxomab were developed, and clinical trials with these antibodies have been used in several types of neoplasia. We studied the expression of EpCAM in UM.

Methods

25 enucleated formalin-fixed, paraffin-embedded UM specimens were immunostained for EpCAM. Histopathological analysis of the specimens with regards to prognostic factors such as cell type, largest (linear) tumor dimension, number of mitotic figures, scleral invasion and tumor infiltrating lymphocytes were done.

Results

None of them was positive for this EpCAM.

Conclusion

In our report, UM did not express EpCAM. Therefore, it is not a helpful immunohistochemical marker to predict the behavior of UM. Further studies are needed to verify if EpCAM could also be related with prognosis and treatment of UM.

A phase I study with adecatumumab, a human antibody directed against epithelial cell adhesion molecule, in hormone refractory prostate cancer patients

AIM OF THE STUDY

Adecatumumab (also known as MT201) is a human recombinant IgG1 monoclonal antibody binding with low affinity to epithelial cell adhesion molecule (EpCAM). To explore safety, pharmacokinetics and pharmacodynamics of adecatumumab, a phase I trial in patients with hormone refractory prostate cancer (HRPC) was performed.

METHODS

Twenty patients were treated with two adecatumumab infusions on days 0 and 14 in cohorts with doses of ten up to 262 mg/m2.

RESULTS

Adecatumumab was well tolerated at all doses tested, and no maximum tolerated dose reached. Most adverse events were mild or moderate with pyrexia and nausea being most frequent. The highest dose of adecatumumab induced shortly after infusion robust and transient increases of TNF-alpha serum levels. At all doses, significant transient declines of peripheral natural killer cells were observed shortly after antibody infusions. Adecatumumab had a serum half-life of 15 days, and immune responses to the antibody were not detected.

CONCLUSIONS

A benign safety profile, long serum half-life and low immunogenicity do warrant further exploration of adecatumumab for treatment of EpCAM-expressing neoplasia.

Prospects of RNA interference therapy for cancer

RNA interference (RNAi) is a powerful gene-silencing process that holds great promise in the field of cancer therapy. The discovery of RNAi has generated enthusiasm within the scientific community, not only because it has been used to rapidly identify key molecules involved in many disease processes including cancer, but also because RNAi has the potential to be translated into a technology with major therapeutic applications. Our evolving understanding of the molecular pathways important for carcinogenesis has created opportunities for cancer therapy employing RNAi technology to target the key molecules within these pathways. Many gene products involved in carcinogenesis have already been explored as targets for RNAi intervention, and RNAi targeting of molecules crucial for tumor-host interactions and tumor resistance to chemo- or radiotherapy has also been investigated. In most of these studies, the silencing of critical gene products by RNAi technology has generated significant antiproliferative and/or proapoptotic effects in cell-culture systems or in preclinical animal models. Nevertheless, significant obstacles, such as in vivo delivery, incomplete suppression of target genes, nonspecific immune responses and the so-called off-target effects, need to be overcome before this technology can be successfully translated into the clinical arena. Significant progress has already been made in addressing some of these issues, and it is foreseen that early phase clinical trials will be initiated in the very near future.

Genetic vaccines against Ep-CAM break tolerance to self in a limited subset of subjects: initial identification of predictive biomarkers

The epithelial cell adhesion molecule, Ep-CAM, has been historically considered a target of passive immunotherapy using monoclonal antibodies, and more recently, of a first Pox-vector-based cancer vaccine Phase I trial in colorectal cancer patients. To shed further light on the use of this antigen, we isolated the mouse and rhesus homologues of human Ep-CAM and explored different genetic vaccination modalities based on the use of adenoviral vectors as well as DNA electroporation (DNA-EP). Immune responses to Ep-CAM were measured by IFN-gamma ELISPOT and intracellular staining assays using overlapping sets of peptides covering the entire coding regions. We found the most powerful vaccination regimen to be constituted by DNA-EP-prime/Adeno-boost mixed-modality protocols. Vaccination in rhesus macaques resulted in breakage of immunological tolerance in a minority of cases. Similarly, a low frequency of responders was observed with the mouse Ep-CAM vaccine in outbred CD1 mice. When immunized CD1 mice were analyzed for MHC haplotype and TCR expression levels, we observed that immune responders all had the same q/q MHC class I haplotype and showed higher expression levels of the TCRVbeta4 and TCRVbeta8 T cell receptors. Our results underscore the current limitations in our capacity to induce efficient cancer vaccines against self antigens like Ep-CAM, but also represent a first effort to identify predictive biomarkers of response.