Dalibor Antolovic

A Complex of EpCAM, Claudin-7, CD44 Variant Isoforms, and Tetraspanins Promotes Colorectal Cancer Progression

High expression of EpCAM and the tetraspanin CO-029 has been associated with colorectal cancer progression. However, opposing results have been reported on CD44 variant isoform v6 (CD44v6) expression. We recently noted in rat gastrointestinal tumors that EpCAM, claudin-7, CO-029, and CD44v6 were frequently coexpressed and could form a complex. This finding suggested the possibly that the complex, rather than the individual molecules, could support tumor progression. The expression of EpCAM, claudin-7, CO-029, and CD44v6 expression was evaluated in colorectal cancer (n = 104), liver metastasis (n = 66), and tumor-free colon and liver tissue. Coexpression and complex formation of the molecules was correlated with clinical variables and apoptosis resistance. EpCAM, claudin-7, CO-029, and CD44v6 expression was up-regulated in colon cancer and liver metastasis. Expression of the four molecules did not correlate with tumor staging and grading. However, coexpression inversely correlated with disease-free survival. Coexpression was accompanied by complex formation and recruitment into tetraspanin-enriched membrane microdomains (TEM). Claudin-7 contributes to complex formation inasmuch as in the absence of claudin-7, EpCAM hardly associates with CO-029 and CD44v6 and is not recruited into TEMs. Notably, colorectal cancer lines that expressed the EpCAM/claudin-7/CO-029/CD44v6 complex displayed a higher degree of apoptosis resistance than lines devoid of any one of the four molecules. Expression of EpCAM, claudin-7, CO-029, and CD44v6 by themselves cannot be considered as prognostic markers in colorectal cancer. However, claudin-7–associated EpCAM is recruited into TEM and forms a complex with CO-029 and CD44v6 that facilitates metastasis formation. (Mol Cancer Res 2007;5(6):553–67)

Antigen-specific Tregs control T cell responses against a limited repertoire of tumor antigens in patients with colorectal carcinoma

Spontaneous antitumor T cell responses in cancer patients are strongly controlled by Tregs, and increased numbers of tumor-infiltrating Tregs correlate with reduced survival. However, the tumor antigens recognized by Tregs in cancer patients and the impact of these cells on tumor-specific T cell responses have not been systematically characterized. Here we used a broad panel of long synthetic peptides of defined tumor antigens and normal tissue antigens to exploit a newly developed method to identify and compare ex vivo the antigen specificities of Tregs with those of effector/memory T cells in peripheral blood of colorectal cancer patients and healthy subjects. Tregs in tumor patients were highly specific for a distinct set of only a few tumor antigens, suggesting that Tregs exert T cell suppression in an antigen-selective manner. Tumor-specific effector T cells were detectable in the majority of colorectal cancer patients but not in healthy individuals. We detected differences in the repertoires of antigens recognized by Tregs and effector/memory T cells in the majority of colorectal cancer patients. In addition, only effector/memory T cell responses against antigens recognized by Tregs strongly increased after Treg depletion. The selection of antigens according to preexisting T cell responses may improve the efficacy of future immunotherapies for cancer and autoimmune disease.

Detection of hematogenous tumor cell dissemination predicts tumor relapse in patients undergoing surgical resection of colorectal liver metastases.

Objective:To examine the prognostic significance of disseminated tumor cells in blood and bone marrow of patients undergoing surgical resection of colorectal liver metastases. Summary Background Data:Despite curative hepatic resection of colorectal liver metastases, a high percentage of patients develop tumor recurrence. These recurrences probably originate from disseminated tumor cells released into the circulation before or during surgery. Methods:Thirty-seven patients with potentially curative (R0) resection of colorectal liver metastases were prospectively enrolled into the study. Preoperative bone marrow samples and preoperative, intraoperative, and postoperative blood samples were examined for disseminated tumor cells by CK20 RT-PCR. Results:Tumor cells were detected in preoperative blood samples in 11 of 37 (30%) patients, in intraoperative blood samples in 17 of 37 (46%) patients, and in postoperative blood samples in 8 of 37 (22%) patients. Four of 25 (16%) patients tested positive for disseminated tumor cells in bone marrow samples. Median follow-up time for all patients was 38 months (range, 10–63 months). Multivariate analysis confirmed tumor cell detection in intraoperative blood (P = 0.009) and in bone marrow samples (P = 0.013) to be independent prognostic factors of tumor relapse. Conclusions:This is the first study demonstrating that detection of hematogenous tumor cell dissemination during hepatic resection of colorectal cancer metastases predicts tumor relapse. Detection of disseminated tumor cells may help to individualize adjuvant therapy for patients with colorectal liver metastases and to develop surgical strategies to prevent intraoperative hematogenous tumor cell shedding.

Tumor Infiltrating T Lymphocytes in Colorectal Cancer: Tumor-Selective Activation and Cytotoxic Activity In Situ

Objective:To examine whether tumor-selective infiltration, activation, and cytotoxic activity of tumor infiltrating T lymphocytes (TIL) can be demonstrated in situ in colorectal cancer samples. Summary Background Data:Recent studies indicated a correlation between the presence of TIL and an improved prognosis in colorectal cancer. However, tumor-selective activation and cytotoxic activity of CD8+ TIL in situ in colorectal cancer patients have not yet been examined. Methods:Tumor samples from 49 patients and corresponding normal mucosa samples from 23 patients with colorectal cancer (UICC stages II–IV) were examined for TIL. Two-color fluorescence immunohistochemistry and multicolor flowcytometric (FACS) analysis were used for quantification of CD8+ T cells and measurement of their activation status (CD69-expression) and cytotoxic activity (CD107a-expression) in situ. Presence of tumor antigen-reactive T cells in tumor, blood, and bone marrow was evaluated by IFN-γ Elispot analysis. Results:While absolute numbers of CD8+ T cells were similar, CD4+ T helper cells were significantly increased in tumor tissue compared with normal mucosa. There was a significantly higher proportion of activated and cytotoxically active CD8+ TIL in colorectal cancer compared with normal mucosa. Increased activation, cytotoxic activity, and functional reactivity of TIL were correlated with the presence of functional tumor antigen-reactive T cells in the blood and bone marrow. The proportion of activated TIL decreased significantly with higher tumor stage. Conclusions:Tumor-selective activation and cytotoxic activity of CD8+ TIL and tumor-selective migration of CD4+ T helper cells were demonstrated in colorectal cancer for the first time. Our data support the immunogenicity of colorectal cancer and suggest clinical significance of tumor-specific immune responses.

Short description of an alternative simplified method for screening recombinant clones within the "AdEasy-System" by Duplex-PCR

BackgroundRecombinant adenoviral vectors are highly efficient for in vitro and in vivo gene delivery. They can easily be produced in large numbers, transduce a wide variety of cell types and generate high levels of transgene expression.The AdEasy system is a widely used system for generating recombinant adenoviral vectors, which are created with a minimum of enzymatic manipulations and by employing homologous recombination in E. coli.In this paper we describe an alternative simplified method for screening recombinant DNA within the AdEasy system. This Duplex-PCR-method is independent of the transgene or insert and can be used for the complete AdEasy system. It is characterized by a simple standard protocol and the results can be obtained within a few hours. The PCR is run with two different primer sets. The primers KanaFor and KanaRev hybridizise with the Kanamycin resistence gene and AdFor and AdRev detect the adenoviral backbone. In case of recombinant clones, two diagnostic fragments with a size of 384 bp and 768 bp are generated.ResultsThe practicability of this method was verified with three different transgenes: Cytosin Deaminase (AdCD), p53 (Adp53) and Granulocyte Macrophage Colony Stimulating Factor (AdGM-CSF). Recombinant clones are indicated by two diagnostic fragments and are then suitable for further processing.ConclusionIn summary, the presented protocol allows fast detection of recombinants with an easy technique by minimizing the amount of necessary steps for generating a recombinant adenovirus. This method is time sparing and cost-effective.

Prognostic impact of hematogenous tumor cell dissemination in patients with stage II colorectal cancer

Adjuvant chemotherapy is not routinely recommended in patients with colorectal cancer stage UICC II. Some of these patients, however, develop recurrent disease. Therefore, valid prognostic criteria are needed to identify high‐risk patients who might benefit from adjuvant therapy. Disseminated tumor cells, detected in blood and bone marrow, may prove to be a valid marker, however, the prognostic relevance of these cells remains debated. In our study, we examined the prognostic significance of disseminated tumor cells in blood and bone marrow of patients with stage II colorectal cancer. Ninety patients with potentially curative (R0) resection of colorectal cancer stage II were prospectively enrolled into the study. Bone marrow and blood samples were examined for disseminated tumor cells by CK 20 RT‐PCR. Patient, tumor and treatment factors were analyzed as prognostic factors. Multivariate analysis confirmed tumor cell detection in blood (hazard ratio 2.1, p = 0.03) and T‐category (hazard ratio 2.2, p = 0.02) to be independent prognostic factors for relapse‐free survival. Tumor cell detection in postoperative blood samples (hazard ratio 7.7, p < 0.001) and number of removed lymph nodes (hazard ratio 6.4, p < 0.001) were independent prognostic factors for disease‐specific survival. Detection of circulating tumor cells in blood samples of patients with stage II colorectal cancer identifies patients with poor outcome. This finding should be confirmed by further studies and could then be used as a basis for conducting a randomized trial evaluating the effect of adjuvant chemotherapy in stage II patients.

Heterogeneous detection of circulating tumor cells in patients with colorectal cancer by immunomagnetic enrichment using different EpCAM-specific antibodies

BackgroundCirculating tumor cells (CTC) and disseminated tumor cells (DTC) are thought to be responsible for metastasis, so the detection of CTC may serve as individual prognostic factor in patients suffering from colorectal cancer. Therefore, a series of immunomagnetic enrichment methods for CTC have been developed using a variety of monoclonal antibodies against the Epithelial Cell Adhesion Molecule (EpCAM). However, it remains unclear whether all commercially available EpCAM antibodies show the same sensitivity and specificity. Furthermore, it remains unclear which method of sample preparation and cell extraction is most suitable for immunomagnetic enrichment and detection of CTC. In this study, we aimed to investigate whether the detection of CTC by a cytokeratin 20 reverse transcriptase-polymerase chain reaction (CK20 RT-PCR) may be influenced by the use of various Epithelial Cell Adhesion Molecule (EpCAM) antibodies for immunomagnetic isolation of CTC.ResultsUsing both EpCAM antibodies (mAb BerEP4 and mAb KS1/4) for immunomagnetic enrichment in blood samples of 39 patients with colorectal cancer we found heterogenous results in each patient with regard to tumor cell detection. In the tumor cell spiking experiments with whole blood samples the sensitivity of the CK 20 RT-PCR assay was higher using immunomagnetic beads coated with mAb KS1/4 compared to precoated mAb BerEP4 Dynabeads. Extraction of MNC fraction with Ficoll gradient centrifugation prior to immunomagnetic enrichment resulted in a higher sensitivity of the CK 20 RT-PCR assay.ConclusionsWe concluded that isolation and detection of CTC with immunomagnetic enrichment methods is critically dependent on the used EpCAM clone. Further studies with a larger number of patients should clarify if the enrichment protocol influences the prognostic value of the tumor cell detection protocol.

Hepaticojejunostomy—Analysis of Risk Factors for Postoperative Bile Leaks and Surgical Complications

Anastomoses between the jejunum and the bile duct are an important component of many surgical procedures; however, risk factors for clinically relevant bile leaks have not yet been adequately defined. The objective of this study was to describe the incidence of bile leaks after hepaticojejunostomy and to define predictive factors associated with this risk and with surgical morbidity. Between October 2001 and April 2004, hepaticojejunostomies were performed in 519 patients in a standardized way. Patient- and treatment-related data were documented prospectively. A bile leak was defined as bilirubin concentration in the drains exceeding serum bilirubin with a consecutive change of clinical management or occurrence of a bilioma necessitating drainage. Surgical morbidity occurred in 15% of patients, the incidence of a bile leak was 5.6%. Multivariate analysis confirmed preoperative radiochemotherapy, preoperative low cholinesterase levels, biliary complications after liver transplantation necessitating a hepaticojejunostomy, and simultaneous liver resection as risk factors for bile leakages, whereas biliary complications after liver transplantation necessitating hepaticojejunostomy, simultaneous liver resection, and diabetes mellitus were significantly associated with postoperative surgical morbidity. Our results demonstrate that hepaticojejunostomy is a safe procedure if performed in a standardized fashion. The above found factors may help to better predict the risk for complications after hepaticojejunostomy.

Ischemic colitis: Who will survive?

BACKGROUND Operative treatment for acute ischemic colitis is associated with a high morbidity and mortality. These patients often have a prolonged postoperative stay in the intensive care unit with an uncertain outcome. In this study, we aimed to develop a predictive risk score for perioperative mortality and to examine long-term follow-up of patients with acute ischemic colitis. METHODS All patients (n = 177) undergoing surgical treatment for acute ischemic colitis in our institution from 2002 to 2008 were prospectively included in this study. Independent predictors of perioperative mortality and poor long-term survival were assessed by uni- and multivariate analysis. RESULTS A risk score including various perioperative variables (nonocclusive ischemic colitis, acute renal failure, extent of bowel ischemia, serum lactate, and duration of catecholamine therapy) was defined being highly predictive for postoperative mortality of patients having undergone an operation for acute ischemic colitis. Mesenteric atherosclerosis in the surgical specimen is an independent prognostic factor for poor long-term survival (52 vs 40 months with mesenteric atherosclerosis; P = .027). CONCLUSION This study for the first time presents a risk score highly predictive of postoperative mortality of patients undergoing an operation for ischemic colitis. Our score may help to further select and modify therapeutic management in patients with acute ischemic colitis on the basis of validated data. Furthermore, we could demonstrate a significant influence of mesenteric atherosclerosis on long-term survival of patients with acute ischemic colitis.

Influence of two different resection techniques (conventional liver resection versus anterior approach) of liver metastases from colorectal cancer on hematogenous tumor cell dissemination - prospective randomized multicenter trial.

BackgroundSurgical hepatic resection remains the treatment of choice for patients with liver metastases from colorectal cancer despite the use of alternative therapeutic strategies. Although this procedure provides long-term survival in a significant number of patients, 50–75% of the patients develop intra- and/or extrahepatic recurrence. One possible reason for tumor recurrence may be intraoperative hematogenous tumor cell dissemination due to mechanical manipulation of the tumor during hepatic resection. Surgical technique may have an influence on hematogenous tumor cell spread. We hypothesize that hematogenous tumor cell dissemination may be reduced by using the anterior approach technique compared to conventional liver resection.Methods/DesignThis is a multi-centre prospective randomized controlled, superiority trial to compare two liver resection techniques of liver metastases from colorectal cancer. 150 patients will be included and randomized intraoperatively after surgical exploration just prior to resection. The primary objective is to compare the anterior approach with the conventional liver resection technique with regard to intraoperative haematogenous tumor cell dissemination. As secondary objectives we examine five year survival rates (OS and DFS), blood loss, duration of operation, requirement of blood transfusions, morbidity rate, prognostic relevance of tumor cell detection in blood and bone marrow and the comparison of tumor cell detection by different detection methods.ConclusionThis trial will answer the question whether there is an advantage for the anterior approach technique compared to the conventional resection group with regard to tumor cell dissemination. It will also add further information about prognostic differences, safety, advantages and disadvantages of each technique.Trial registrationCurrent controlled trials – ISRCTN45066244