Biodistribution Studies of Epithelial Cell Adhesion Molecule (EpCAM)-Directed Monoclonal Antibodies in the EpCAM-Transgenic Mouse Tumor Model

Addition of formaldehyde releaser imidazolidinyl urea and MOPS buffer to urine samples enables delayed processing for flow cytometric analysis of urinary cells: A simple, two step conservation method of urinary cells for flow cytometry

INTRODUCTION

Kidney diseases are a major health concern worldwide. Currently there is a large unmet need for novel biomarkers to non-invasively diagnose and monitor kidney diseases. Urinary cells are promising biomarkers and their analysis by flow cytometry has demonstrated its utility in diverse clinical settings. However, up to date this methodology depends on fresh samples, as cellular event counts and the signal-to-noise-ratio deter over time. Here we developed an easy-to-use two-step preservation method for conservation of urine samples for subsequent flow cytometry.

METHODS

The protocol utilizes a combination of the formaldehyde releasing agent imidazolidinyl urea (IU) and MOPS buffer, leading to gentle fixation of urinary cells.

RESULTS

The preservation method increases acceptable storing time of urine samples from several hours to up to 6 days. Cellular event counts and staining properties of cells remain comparable to fresh untreated samples.

OUTLOOK

The hereby presented preservation method facilitates future investigations on flow cytometry of urinary cells as potential biomarkers and may enable broad implementation in clinical practice.

Antitumor activities of a defucosylated anti‑EpCAM monoclonal antibody in colorectal carcinoma xenograft models

Epithelial cell adhesion molecule (EpCAM) is a type I transmembrane glycoprotein, which is highly expressed on tumor cells. As EpCAM plays a crucial role in cell adhesion, survival, proliferation, stemness, and tumorigenesis, it has been considered as a promising target for tumor diagnosis and therapy. Anti‑EpCAM monoclonal antibodies (mAbs) have been developed and have previously demonstrated promising outcomes in several clinical trials. An anti‑EpCAM mAb, EpMab‑37 (mouse IgG₁, kappa) was previously developed by the authors, using the cell‑based immunization and screening method. In the present study, a defucosylated version of anti‑EpCAM mAb (EpMab‑37‑mG2a‑f) was generated to evaluate the antitumor activity against EpCAM‑positive cells. EpMab‑37‑mG_2a‑f recognized EpCAM‑overexpressing CHO‑K1 (CHO/EpCAM) cells with a moderate binding‑affinity [dissociation constant (K_D)=2.2x10^‑8 M] using flow cytometry. EpMab‑37‑mG_2a‑f exhibited potent antibody‑dependent cellular cytotoxicity (ADCC) and complement‑dependent cytotoxicity (CDC) for CHO/EpCAM cells by murine splenocytes and complements, respectively. Furthermore, the administration of EpMab‑37‑mG_2a‑f significantly suppressed CHO/EpCAM xenograft tumor development compared with the control mouse IgG. EpMab‑37‑mG_2a‑f also exhibited a moderate binding‑affinity (K_D=1.5x10^‑8 M) and high ADCC and CDC activities for a colorectal cancer cell line (Caco‑2 cells). The administration of EpMab‑37‑mG_2a‑f to Caco‑2 tumor‑bearing mice significantly suppressed tumor development compared with the control. By contrast, EpMab‑37‑mG_2a‑f never suppressed the xenograft tumor growth of Caco‑2 cells in which EpCAM was knocked out. On the whole, these results indicate that EpMab‑37‑mG_2a‑f may exert antitumor activities against EpCAM‑positive cancers and may thus be a promising therapeutic regimen for colorectal cancer.

The Biodistribution of a CD3 and EpCAM Bispecific T-Cell Engager Is Driven by the CD3 Arm

Bispecific T-cell engager (BiTE) molecules are designed to engage and activate cytotoxic T cells to kill tumor cells. Little is known about their biodistribution in immunocompetent settings. Methods: To explore their pharmacokinetics and the role of the immune cells, BiTE molecules were radiolabeled with the PET isotope ⁸⁹Zr and studied in immunocompetent and immunodeficient mouse models. Results: PET images and ex vivo biodistribution in immunocompetent mice with [⁸⁹Zr]Zr-DFO-N-suc-muS110, targeting mouse CD3 (dissociation constant [K_D], 2.9 nM) and mouse epithelial cell adhesion molecule (EpCAM; K_D, 21 nM), and with [⁸⁹Zr]Zr-DFO-N-suc-hyS110, targeting only mouse CD3 (K_D, 2.9 nM), showed uptake in the tumor, spleen, and other lymphoid organs, whereas the human-specific control BiTE [⁸⁹Zr]Zr-DFO-N-suc-AMG 110 showed similar tumor uptake but lacked spleen uptake. [⁸⁹Zr]Zr-DFO-N-suc-muS110 spleen uptake was lower in immunodeficient than in immunocompetent mice. After repeated administration of nonradiolabeled muS110 to immunocompetent mice, ⁸⁹Zr-muS110 uptake in the spleen and other lymphoid tissues decreased and was comparable to uptake in immunodeficient mice, indicating saturation of CD3 binding sites. Autoradiography and immunohistochemistry demonstrated colocalization of [⁸⁹Zr]Zr-DFO-N-suc-muS110 and [⁸⁹Zr]Zr-DFO-N-suc-hyS110 with CD3-positive T cells in the tumor and spleen but not with EpCAM expression. Also, uptake in the duodenum correlated with a high incidence of T cells. Conclusion: [⁸⁹Zr]Zr-DFO-N-suc-muS110 biodistribution is dependent mainly on the T-cell-targeting arm, with a limited contribution from its second arm, targeting EpCAM. These findings highlight the need for extensive biodistribution studies of novel bispecific constructs, as the results might have implications for their respective drug development and clinical translation.

Kidney transplant monitoring by urinary flow cytometry: Biomarker combination of T cells, renal tubular epithelial cells, and podocalyxin-positive cells detects rejection

Creatinine and proteinuria are used to monitor kidney transplant patients. However, renal biopsies are needed to diagnose renal graft rejection. Here, we assessed whether the quantification of different urinary cells would allow non-invasive detection of rejection. Urinary cell numbers of CD4⁺ and CD8⁺ T cells, monocytes/macrophages, tubular epithelial cells (TEC), and podocalyxin(PDX)-positive cells were determined using flow cytometry and were compared to biopsy results. Urine samples of 63 renal transplant patients were analyzed. Patients with transplant rejection had higher amounts of urinary T cells than controls; however, patients who showed worsening graft function without rejection had similar numbers of T cells. T cells correlated with histological findings (interstitial inflammation p = 0.0005, r = 0.70; tubulitis p = 0.006, r = 0.58). Combining the amount of urinary T cells and TEC, or T cells and PDX⁺ cells, yielded a significant segregation of patients with rejection from patients without rejection (all p < 0.01, area under the curve 0.89–0.91). Urinary cell populations analyzed by flow cytometry have the potential to introduce new monitoring methods for kidney transplant patients. The combination of urinary T cells, TEC, and PDX-positive cells may allow non-invasive detection of transplant rejection.

Targeted delivery of CD40L promotes restricted activation of antigen-presenting cells and induction of cancer cell death

Background

Stimulation of CD40 can augment anti-cancer T cell immune responses by triggering effective activation and maturation of antigen-presenting cells (APCs). Although CD40 agonists have clinical activity in humans, the associated systemic activation of the immune system triggers dose-limiting side-effects.

Methods

To increase the tumor selectivity of CD40 agonist-based therapies, we developed an approach in which soluble trimeric CD40L (sCD40L) is genetically fused to tumor targeting antibody fragments, yielding scFv:CD40L fusion proteins. We hypothesized that scFv:CD40L fusion proteins would have reduced CD40 agonist activity similar to sCD40L but will be converted to a highly agonistic membrane CD40L-like form of CD40L upon anchoring to cell surface exposed antigen via the scFv domain.

Results

Targeted delivery of CD40L to the carcinoma marker EpCAM on carcinoma cells induced dose-dependent paracrine maturation of DCs ~20-fold more effective than a non-targeted control scFv:CD40L fusion protein. Similarly, targeted delivery of CD40L to the B cell leukemia marker CD20 induced effective paracrine maturation of DCs. Of note, the CD20-selective delivery of CD40L also triggered loss of cell viability in certain B cell leukemic cell lines as a result of CD20-induced apoptosis.

Conclusions

Targeted delivery of CD40L to cancer cells is a promising strategy that may help to trigger cancer-localized activation of CD40 and can be modified to exert additional anti-cancer activity via the targeting domain.

Comparison of mAbs targeting epithelial cell adhesion molecule for the detection of prostate cancer lymph node metastases with multimodal contrast agents: quantitative small-animal PET/CT and NIRF

The proliferation of most carcinomas is associated with an overexpression of epithelial cell adhesion molecule (EpCAM), a 40-kDa type I transmembrane protein found on epithelial cells yet absent from other cell types. The absence of EpCAM in normal lymphatics makes it an attractive marker for studying lymph node (LN) metastases of carcinomas to improve LN staging accuracy. Herein, we developed and quantitatively compared dual-labeled monoclonal antibodies (mAbs) of varying affinities against EpCAM for both noninvasive and intraoperative detection of metastatic LNs in prostate cancer.

METHODS

A panel of hybridoma-derived anti-EpCAM mAbs was generated and screened. Two high-affinity candidate mAbs with specificity for nonoverlapping epitopes on the EpCAM extracellular domain were chosen for further evaluation. After conjugation with DOTA for (64)Cu radiolabeling and IRDye 800CW as a fluorophore, dual-labeled specific or isotype control mAb was administered intravenously to male nu/nu mice at 10-12 wk after orthotopic implantation of DsRed-expressing PC3 cells. Within 18-24 h, noninvasive small-animal PET/CT and in vivo, in situ, and ex vivo DsRed reporter gene and near-infrared fluorescence (NIRF) imaging were performed to detect primary tumors and metastatic LNs. Using DsRed fluorescence as the true indicator of cancer-positive tissue, we performed receiver operating characteristic curve analyses of percentage injected dose per gram measured from quantitative small-animal PET/CT and fluorescence intensity measured from semiquantitative NIRF imaging for each LN examined to compare mAb sensitivity and specificity.

RESULTS

mAbs 7 and 153 generated in-house were found to have higher affinity than commercial mAb 9601. Accuracy, as a function of sensitivity and specificity, for the detection of cancer-positive LNs during in vivo small-animal PET/CT was highest for mAbs 7 (87.0%) and 153 (78.0%) and significantly greater (P < 0.001) than random chance (50.0%). Rates for mAb 9601 (60.7%) and control mAb 69 (27.0%) were not significantly different from chance. Similarly, mAb 7 had significant detection accuracy by NIRF imaging (96.0%, P < 0.001).

CONCLUSION

mAbs 7 and 153 are attractive, high-affinity candidates for further multimodal imaging agent optimization aimed at enhancing sensitivity and specificity for detection of metastatic LNs in prostate cancer. Fully quantitative NIRF imaging is needed for comprehensive analyses of NIRF-labeled agent accuracy for intraoperative guidance.

High interstitial fluid pressure is associated with low tumour penetration of diagnostic monoclonal antibodies applied for molecular imaging purposes

The human epithelial cell adhesion molecule (EpCAM) is highly expressed in a variety of clinical tumour entities. Although an antibody against EpCAM has successfully been used as an adjuvant therapy in colon cancer, this therapy has never gained wide-spread use. We have therefore investigated the possibilities and limitations for EpCAM as possible molecular imaging target using a panel of preclinical cancer models. Twelve human cancer cell lines representing six tumour entities were tested for their EpCAM expression by qPCR, flow cytometry analysis and immunocytochemistry. In addition, EpCAM expression was analyzed in vivo in xenograft models for tumours derived from these cells. Except for melanoma, all cell lines expressed EpCAM mRNA and protein when grown in vitro. Although they exhibited different mRNA levels, all cell lines showed similar EpCAM protein levels upon detection with monoclonal antibodies. When grown in vivo, the EpCAM expression was unaffected compared to in vitro except for the pancreatic carcinoma cell line 5072 which lost its EpCAM expression in vivo. Intravenously applied radio-labelled anti EpCAM MOC31 antibody was enriched in HT29 primary tumour xenografts indicating that EpCAM binding sites are accessible in vivo. However, bound antibody could only be immunohistochemically detected in the vicinity of perfused blood vessels. Investigation of the fine structure of the HT29 tumour blood vessels showed that they were immature and prone for higher fluid flux into the interstitial space. Consistent with this hypothesis, a higher interstitial fluid pressure of about 12 mbar was measured in the HT29 primary tumour via "wick-in-needle" technique which could explain the limited diffusion of the antibody into the tumour observed by immunohistochemistry.

Therapeutic potential of amanitin-conjugated anti-epithelial cell adhesion molecule monoclonal antibody against pancreatic carcinoma

BACKGROUND

Human epithelial cell adhesion molecule (EpCAM) is overexpressed in many cancers. Anti-EpCAM antibodies have shown promise in preclinical studies, but showed no tumor regression in a recent phase II clinical trial. Therefore, we generated a novel anti-EpCAM antibody-drug conjugate and assessed whether it showed enhanced antitumor effects.

METHODS

Chemical cross-linking was conducted to covalently conjugate α-amanitin, a toxin known to inhibit DNA transcription, with chiHEA125, a chimerized anti-EpCAM monoclonal antibody, to generate the antibody-drug conjugate α-amanitin-glutarate-chiHEA125 (chiHEA125-Ama). Antiproliferative activity of chiHEA125-Ama was tested in human pancreatic (BxPc-3 and Capan-1), colorectal (Colo205), breast (MCF-7), and bile duct (OZ) cancer cell lines in vitro using [(3)H]-thymidine incorporation assay. Antitumor activity of chiHEA125-Ama was assessed in vivo in immunocompromised mice bearing subcutaneous human BxPc-3 pancreatic carcinoma xenograft tumors (n = 66 mice). Cell proliferation and apoptosis were evaluated in xenograft tumors by immunohistochemistry. All statistical tests were two-sided.

RESULTS

In all cell lines, chiHEA125-Ama reduced cell proliferation (mean half maximal inhibitory concentration [IC(50)] = 2.5 × 10(-10) to 5.4 × 10(-12) M). A single dose of chiHEA125-Ama inhibited BxPc-3 xenograft tumor growth (chiHEA125 [control, n = 4 mice] vs. chiHEA125-Ama [n = 6 mice], dose of 15 mg/kg with respect to IgG and 50 μg/kg with respect to α-amanitin, mean relative increase in tumor volume on day 16 = 884% vs. -79%, difference = 963%, 95% CI = 582% to 1344%, P = .019). Two higher doses of chiHEA125-Ama (100 μg/kg with respect to α-amanitin), administered 1 week apart (n = 10 mice per group), led to complete tumor regression in nine of 10 (90%) mice compared with chiHEA125, during the observation period of 16 days; increased apoptosis and reduced cell proliferation were observed in mice treated with chiHEA125-Ama.

CONCLUSION

This preclinical study suggests that anti-EpCAM antibody conjugates with α-amanitin have the potential to be highly effective therapeutic agents for pancreatic carcinomas and various EpCAM-expressing malignancies.

Pre-clinical strategies and safety issues in developing therapeutic monoclonal antibodies

Although mAbs present a different set of challenges from other product classes, and the pre-clinical safety evaluation may need to be more extensive than for other medicinal products to overcome the limited predictive value of conventional pre-clinical test systems, the level of risk associated with first administration to human subjects can be effectively mitigated. This article seeks to provide a systematic approach to identifying and addressing the pertinent risks relative to the characteristics of the particular mAb product before the first administration to human subjects.

Biodistribution of [125I]-labeled therapeutic proteins: application in protein drug development beyond oncology

The majority of biodistribution studies of therapeutic proteins published to date focus on tumor-targeting agents. In this report we present a number of case studies that demonstrate the utility of biodistribution studies during preclinical development of biotherapeutics for non oncology indications, as well as provide a practical perspective on the methodology applied to these studies. For the commonly used classes of biologics (such as human monoclonal antibodies), biodistribution profiles may be compared to those of other therapeutics of the same class and compounds with unexpected off-target mediated uptake may be identified. Temporal biodistribution profiles may be used to address kinetics and reversibility of target- and/or off-target-mediated accumulation. In cases when circulating biotherapeutic is rapidly eliminated from circulation due to the formation of anti-product antibodies, tissue data may provide useful insight on test article exposure at the site of therapeutic action (or at the site of toxicity). Comparison of temporal biodistribution profiles between the genetically engineered and wild-type mouse strains or between the disease models and healthy animals may provide useful insight on sites and kinetics of target-mediated elimination. Finally, biodistribution studies will be a useful tool to study in vivo disposition for a variety of existing and upcoming novel classes of protein compounds.

Stage-specific regulation of adhesion molecule expression segregates epithelial stem/progenitor cells in fetal and adult human livers

PURPOSE

Regulated expression of cell adhesion molecules could be critical in the proliferation, sequestration, and maintenance of stem/progenitor cells. Therefore, we determined fetal and adult stage-specific roles of cell adhesion in liver cell compartments.

METHODS

We performed immunostaining for the adhesion molecules, E-cadherin and Ep-CAM, associated proteins, beta-catenin and alpha-actinin, hepatobiliary markers, albumin, alpha-fetoprotein, and cytokeratin-19, and the proliferation marker, Ki-67. Expression of albumin was verified by in situ mRNA hybridization.

RESULTS

In the fetal liver, hepatoblasts showed extensive proliferation with wide expression of E-cadherin, beta-catenin, and alpha-actinin, although Ep-CAM was expressed in these cells less intensely and focally in the cell membrane to indicate weak cell adhesion. Hepatoblasts in ductal plate and bile ducts showed less proliferation and Ep-CAM was intensely expressed in these cells throughout the cell membrane, indicating strong adhesion. In some ductal plate cells, beta-catenin was additionally in the cytoplasm and nucleus, suggesting active cell signaling by adhesion molecules. In adult livers, cells were no longer proliferating and E-cadherin, beta-catenin, and alpha-actinin were expressed in hepatocytes throughout, whereas Ep-CAM was expressed in only bile duct cells. Some cells in ductal structures of the adult liver with Ep-CAM coexpressed albumin and cytokeratin-19, indicating persistence of fetal-like stem/progenitor cells.

CONCLUSIONS

Regulated expression of Ep-CAM supported proliferation in fetal hepatoblasts through weak adhesion and helped in biliary morphogenesis by promoting stronger adhesion in hepatoblasts during this process. Restriction of Ep-CAM expression to bile ducts in the adult liver presumably facilitated sequestration of stem/progenitor cells. This stage-specific and cell compartment-related regulation of adhesion molecules should be relevant for defining how liver stem/progenitor cells enter, exit, and remain in hepatic niches during both health and disease.