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Biomedical subjects

Arko Gorter

Publications and source records attributed to Arko Gorter.

9 recordsLinked to original sources
PubMed2005

Substantial changes in gene expression of Wnt, MAPK and TNFalpha pathways induced by TGF-beta1 in cervical cancer cell lines.

Transforming growth factor-beta 1 (TGF-beta1) is a potent inhibitor of epithelial cell proliferation. During the development of cervical carcinoma however, an increase in production of TGF-beta1 is accompanied by decreased sensitivity for the growth-limiting effect of TGF-beta1. TGF-beta1 has an anti-proliferative effect on cells of the immune system and thus can be advantageous for tumor progression. The aim of the present study was to determine the effect of TGF-beta1 on mRNA expression profile of genes in pathways involved in cell growth and cell death, in cervical carcinoma cell lines with different sensitivity to TGF-beta1. For this purpose, we have investigated changes in gene expression in TGF-beta1 stimulated cervical cancer cell lines with high (CC10B), intermediate (SiHa) and low (HeLa) sensitivity to the anti-proliferative effect of TGF-beta1, at timepoints 0, 6, 12 and 24 h. Microarray analysis, using Affymetrics focus arrays, representing 8973 genes, was used to measure gene expression. In our study novel target genes involved in tumor necrosis factor alpha (TNFalpha), mitogen-activated protein kinase (MAPK) and wingless type (Wnt) pathways in response to TGF-beta1 were found. Substantial differences in gene expression between TGF-beta1 sensitive and insensitive cell lines were observed involving genes in TNFalpha, MAPK, Wnt and Smad pathways. Since these pathways are implicated in cell proliferation and cell death, these pathways may play a role in determining the overall sensitivity of a cell to TGF-beta1 induced cell growth inhibition. The results were subsequently validated by quantitative real-time PCR. Increased resistance to TGF-beta1 induced cell growth inhibition was correlated with an elevated production of TGF-beta1 by the cell lines, as measured by enzyme linked immunosorbent assay. TGF-beta1 production did not inhibit cell growth, since blocking TGF-beta1 protein by anti-TGF-beta had no effect on cell proliferation. TGF-beta1 excretion by tumor cells more likely contributes to paracrine stimulation of tumor development.

Base Sequence↗
PubMed2004

Prognostic relevance of TGF-beta1 and PAI-1 in cervical cancer.

Cervical carcinoma is a human papilloma virus (HPV)-related immunogenic type of malignancy, in which escape of the tumor from the hosts' immune response is thought to play an important role in carcinogenesis. The multifunctional cytokine transforming growth factor-beta(1) (TGF-beta(1)) is involved in immunosuppression, stroma and extracellular matrix formation and controlling (epithelial) cell growth. The plasminogen activating (PA) system plays a key role in the cascade of tumor-associated proteolysis leading to extracellular matrix degradation and stromal invasion. Changes in expression of components of this system, including plasminogen activator inhibitor-1 (PAI-1), have been associated with poor prognosis in a variety of solid tumors. The present study was undertaken to assess the role of both components on relapse, survival and other clinicopathologic parameters in cervical cancer. The expression of TGF-beta(1) mRNA in 108 paraffin-embedded cervical carcinomas was detected by mRNA in situ hybridization. Immunohistochemistry was used to investigate the expression of PAI-1 protein. The presence of cytoplasmatic TGF-beta(1) mRNA in tumor cells was not significantly correlated with the other clinicopathologic parameters investigated or with a worse (disease-free) survival. Expression of the PAI-1 protein in tumor cells was strongly correlated with worse overall and disease-free survival, in addition to well-known prognostic parameters such as lymph node metastasis, depth of tumor infiltration, tumor size and vasoinvasion. In the multivariate analysis, PAI-1 turned out to be a strong independent prognostic factor. In a subgroup of patients without lymph node metastases, PAI-1 was predictive for worse survival and relapse of disease, too. Our results show that the (enhanced) expression of PAI-1 by carcinoma cells is correlated with worse (overall and disease-free) survival of patients with cancer of the uterine cervix. The expression of TGF-beta(1) in itself is not associated with worse survival in these patients. Although simultaneous presence of the 2 factors was observed in all tumors, induction of PAI-1 by TGF-beta(1) could not be demonstrated in our group of cervical carcinomas.

Adult↗
PubMed2004

Tumor-specific inhibition of membrane-bound complement regulatory protein Crry with bispecific monoclonal antibodies prevents tumor outgrowth in a rat colorectal cancer lung metastases model.

Membrane-bound complement regulatory proteins (mCRP) inhibit complement-mediated tumor cell eradication in vitro and in vivo. Immunotherapy of cancer with monoclonal antibodies (mAbs) that activate complement might be hampered by expression of mCRP on tumor cells. An important strategy to improve mAb immunotherapy can be blocking or overwhelming mCRP at the tumor cells surface in a tumor-specific manner. In our study, we investigated the feasibility of this approach in vivo using bispecific mAbs (bi-mAbs). This study, performed in a syngeneic lung metastases model of rat (WAG/Rij) colorectal cancer, showed that modulation of mCRP on tumor cells resulted in significantly decreased tumor outgrowth. Opsonization of tumor cells with a bi-mAb directed against a tumor-associated antigen and rat mCRP Crry (MG4(2a)*5I2) almost completely prevented the outgrowth of lung tumors (0-7 tumors/rat; n = 17). Opsonization with mAb-cobra venom factor conjugates significantly reduced the number of lung tumors (23-59 tumors; n = 12) compared with the unconjugated MG4(2a) (175-246 tumors; n = 17; P = 0.008 and 0.014, respectively). The effect of MG4(2a)*5I2 was shown to be caused by increased complement activation due to inhibition of Crry. Moreover, prophylactic treatment with MG4(2a)*5I2 or MG4(2a) showed comparable results (3-24 and 215-472 tumors, P = 0.02; n = 6) as observed with pre-opsonized tumor cells without noticeable side effects, despite binding of MG4(2a)*5I2 to endothelium and leukocytes. These results demonstrate that Crry inhibits complement-mediated tumor cell eradication by immunotherapeutic mAbs and show that tumor-specific inhibition of complement regulatory proteins using bi-mAbs can significantly improve mAb-mediated immunotherapy.

Adenocarcinoma↗
PubMed2004

Beta-glucan enhanced killing of renal cell carcinoma micrometastases by monoclonal antibody G250 directed complement activation.

Metastases from renal cell carcinomas (RCC) are resistant to radiation and chemotherapy but are relatively immunogenic. We have investigated the possibility to eliminate human RCC micrometastases using MAb G250. G250 penetrates human micrometastases completely in a spheroid model and induces complement deposition rapidly on the outmost cell layers. However, complement dependent cytotoxicity (CDC) was barely detected using either (51)chromium release assays or confocal microscopy, due to relatively low expression of the G250 antigen and the effect of membrane bound complement regulatory proteins. Addition of blocking anti-CD59 MAbs enhanced formation of C5b-9 and consequently complement mediated lysis (13%). Complement assisted cellular cytotoxicity (CACC) was not detectable, although the iC3b ligand and CR3 receptor were present on respectively target and effector cells. Addition of soluble beta-glucan induced the killing of MAb and iC3b opsonized spheroids by effector cells (6-21%). Despite a lower affinity for G250 antigen, a bispecific anti-G250*anti-CD55 MAb enhanced cell killing in spheroids comparable to the parental G250 MAb. Our results suggest that complement-activating G250 in combination with anti-mCRP MAbs is able to kill human RCC cells in micrometastasis in vitro. For CACC the presence of CR3-priming beta-glucan seems to be obligatory. In vivo, bi-MAb may be more effective as therapeutic agent due to its increased C5a generating properties.

Antibodies, Monoclonal↗
PubMed2003

Interaction of differently designed immunoliposomes with colon cancer cells and Kupffer cells. An in vitro comparison.

PURPOSE: Evaluate the effectiveness of distal-end coupling of a tumor-specific antibody to liposomal polyethylene glycol (PEG) chains to improve target binding and reduce interference by macrophage uptake. METHODS: Monoclonal antibody CC52, specific for CC531 rat colon carcinoma, was coupled to the bilayer of PEG-liposomes (type I) or to the distal end of bilayer-anchored PEG-chains (type II). Uptake of both (radiolabeled)liposome types by CC531 cells and rat liver macrophages was determined. RESULTS: With increasing antibody density, both immunoliposome types showed increased binding to target cells, but type II liposomes displayed better target recognition than type I. Uptake by macrophages increased with antibody density for both liposome types. Lowest uptake by macrophages was found for type II liposomes at low antibody densities. Unexpectedly, not only for type I but also for type II liposomes, in which the antibody is coupled via its Fc moiety, uptake by macrophages was inhibited by aggregated IgG, indicating involvement of Fc receptors. Also polyinosinic acid, an inhibitor of scavenger receptors, reduced uptake of type II liposomes. CONCLUSION: Although distal end coupling of antibodies to bilayer-anchored PEG chains in liposomes through the Fc moiety enhances target cell binding, it does not prevent the recognition by Fc receptors on macrophages.

Animals↗
PubMed2002

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

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

Animals↗
PubMed2002

The inhibitory effect of CD46, CD55, and CD59 on complement activation after immunotherapeutic treatment of cervical carcinoma cells with monoclonal antibodies or bispecific monoclonal antibodies.

The role of membrane-bound complement regulatory proteins (mCRP) in the protection of tumor cells in vivo against elimination by the immune system is still unknown. In this study the effect of expression of these mCRP by cervical cancer cells was investigated. In situ expression of mCRP was observed on cervical carcinomas, normal cervical epithelial cells, and the surrounding stroma. Deposition of C3 and C5b-9 was sporadically found on the tumor cells and the surrounding stroma. A low expression of CD46 was statistically significantly associated with deposition of C3. Comparable expression patterns were shown on primary cervical tumor cell suspensions. A relatively high deposition of C4c was found on these tumor cells, indicating classical pathway activation. Furthermore, it was demonstrated that CD55 and CD59 were the most potent inhibitors of C3 deposition and classical pathway-mediated lysis, respectively, on cervical cancer cell lines. The feasibility of increasing complement activation at the tumor cell membrane surface was demonstrated with an anti-HLA Class I*anti-CD55 bispecific mAb. The potential immunotherapeutic applicability was investigated with both anti-G250*anti-CD55 and anti-Ep-CAM*anti-CD55 bispecific mAbs. An approximate 2-fold increase in C3 deposition, compared with the parental anti-Ep-CAM mAb, was attained with an anti-Ep-CAM*anti-CD55 bispecific mAb when the tumor-associated antigen was expressed in sufficient amounts. These results demonstrate that when tumor-associated antigens are expressed in adequate amounts, bispecific mAbs in vivo may be potent immunotherapeutic agents to enhance an inflammatory reaction at the tumor site.

Antibodies, Bispecific↗
PubMed2002

Transforming growth factor-beta1 induces tumor stroma and reduces tumor infiltrate in cervical cancer.

Cervical carcinomas consist of tumor cell nests surrounded by varying amounts of intratumoral stroma containing different quantities and types of immune cells. Besides controlling (epithelial) cell growth, the multifunctional cytokine transforming growth factor-beta(1) (TGF-beta(1)) is involved in the formation of stroma and extracellular matrix (ECM) and in immunosuppression. Several malignancies are known to be associated with enhanced production of TGF-beta(1), repression or mutation of TGF-beta transmembrane receptors, or mutations at the postreceptor intracellular signaling pathway. The aim of our study was to investigate the role of tumor cell-derived TGF-beta(1) on the amount of intratumoral stroma; the deposition of collagen IV, fibronectin, and laminin; and the tumor infiltrate in cervical carcinoma. The expression of TGF-beta(1) mRNA in 108 paraffin-embedded cervical carcinomas was detected by mRNA in situ hybridization. Immunohistochemistry was used to investigate the amount of tumor stroma and ECM proteins and the extent of the tumor infiltrate. Plasminogen activator inhibitor-1 (PAI-1) protein expression in tumor cells was determined to verify the biological activity of TGF-beta(1.) Cytoplasmatic TGF-beta(1) mRNA expression in tumor cells was significantly correlated with the amount of intratumoral stroma and the deposition of collagen IV. TGF-beta(1) mRNA expression in every tumor was accompanied by PAI-1 expression, indicating biological activity of TGF-beta(1). An inverse relationship between TGF-beta(1) mRNA expression in tumor cells and the extent of the tumor infiltrate was demonstrated. Our results indicate that cervical cancer cells affect the amount and the composition of the intratumoral stroma and the tumor infiltrate by the production and secretion of TGF-beta(1).

Collagen Type IV↗