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Biomedical subjects

K Hoekman

Publications and source records attributed to K Hoekman.

At least 19 recordsLinked to original sources
PubMed2005

Recombinant human endostatin administered as a 28-day continuous intravenous infusion, followed by daily subcutaneous injections: a phase I and pharmacokinetic study in patients with advanced cancer.

BACKGROUND: Endostatin is an endogenous collagen XVIII-fragment with anti-angiogenic properties and remarkable antitumor activity in mice. Preclinical data suggest that continuous low dose administration of endostatin is much more potent than intermittent dosing. The feasibility of this approach is tested in a phase I study. PATIENTS AND METHODS: We determined the safety and pharmacokinetic profile of 4-week continuous intravenous infusion of recombinant human (rh)-endostatin, followed after an interval of 1 week by twice daily subcutaneous injections in patients with advanced cancer. Thirty-two patients received rh-endostatin in six dosing cohorts, ranging from 3.75 mg/m(2)/day to 120 mg/m(2)/day. Serum endostatin pharmacokinetics, toxicity and antitumor response were determined. RESULTS: A total of 160 cycles were delivered without significant toxicities. Pharmacokinetic analysis showed a linear increase of steady-state serum endostatin concentrations with dose (i.v. r(2)=0.96; s.c. r(2)=0.99) reaching 300--1,000 ng/ml for the two highest doses, with considerable interpatient variation. The main pharmacokinetic values for both routes of administration were similar. The apparent steady-state concentration and AUC reached at 60--120 mg/m(2)/day were within the range expected to induce anti-angiogenic and antitumor effects based on preclinical tumor models. Although no objective responses were observed, two patients had long-lasting stable disease (defined as a tumor increase<100%). CONCLUSION: rh-endostatin was safely administered both by continuous infusion and by twice daily subcutaneous injections up to 120 mg/m(2)/day. Predictable pK was seen in this dose range and the target endostatin levels were reached from 60 mg/m(2)/day and above.

Adult↗
PubMed2004

Systemic and peritoneal angiogenic response after laparoscopic or conventional colon resection in cancer patients: a prospective, randomized trial.

PURPOSE: Angiogenesis is essential for wound healing. Vascular endothelial growth factor and endostatin are both endogenous angiogenic factors thought to be involved in the initiation and termination of angiogenesis. The aim of this study was to assess the local and systemic angiogenic profile in patients undergoing laparoscopic or open surgery for colon cancer. METHODS: Patients with primary colon carcinoma were prospectively randomized to curative laparoscopic (n = 12) or conventional (n = 14) resection. Vascular endothelial growth factor and endostatin levels in serum and wound fluid were investigated. RESULTS: In both groups vascular endothelial growth factor levels in wound fluid were significantly higher than postoperative serum levels, whereas endostatin levels in wound fluid were lower than serum levels and decreased progressively after surgery. The vascular endothelial growth factor levels in wound fluid measured at Day 4 were significantly higher in the laparoscopy group than in the laparotomy patients. CONCLUSIONS: Wound healing is associated with a strong local increase in pro-angiogenic factors and a decrease in antiangiogenic factors. The investigation of locally produced factors offered greater insight into the process of angiogenesis during wound healing than could be acquired from the circulation.

Aged↗
PubMed2004

Role of platelet derived endothelial cell growth factor/thymidine phosphorylase in fluoropyrimidine sensitivity and potential role of deoxyribose-1-phosphate.

Thymidine phosphorylase (TP) catalyzes the phosphorolytic cleavage of thymidine (TdR) to thymine and deoxyribose-1-phosphate (dR-1-P). TP, which is overexpressed in a wide variety of solid tumors, is involved in the activation and inactivation of fluoropyrimidines. We investigated the role of TP in 5'-deoxy-5-fluorouridine (5'DFUR), 5-fluorouracil (5FU) and trifluorothymidine (TFT) sensitivity. TP had no effect on TFT while it activated 5'DFUR and to a lesser extent 5FU. In order to provide an explanation for this difference in activation of 5'DFUR and 5FU, we studied the role of the 5FU co-substrate, dR-1-P, needed for its activation.

Antimetabolites, Antineoplastic↗
PubMed2004

Clarifying the term 'palliative' in clinical oncology.

The objective of this study was to clarify the term 'palliative' in clinical oncology. A qualitative study design with in-depth interviews was applied. The study sample included 30 cancer patients and 16 physicians. In clinical oncology, the use of the term 'palliative' to describe both anticancer treatments and palliative care may cause confusion and misunderstanding. Different aspects of palliative care, as expressed by the WHO definition, are not so easily recognizable with regard to palliative oncological treatments. Furthermore, the fact that the same anticancer treatments can be given to patients with palliative or curative intention is confusing. The distinction between curative and palliative oncological treatments is of crucial importance for the treatment decision-making process. Close consideration of the use of the term 'palliative' will help to clarify the various goals of treatment and care in oncological practice.

Adult↗
PubMed2004

A patient with a VEGF and endostatin producing gastrointestinal autonomic nerve tumour.

Tumour associated neovascularisation has been characterised as chaotic and insufficient. This report details the results of the analysis of angiogenic factors in tumour cyst fluid, pleural fluid, and blood from a patient with a gastrointestinal autonomic nerve tumour. The tumour produced vascular endothelial growth factor and endostatin in large quantities, which may explain the dysfunctional angiogenesis and tendency to bleeding seen in this tumour type.

Adult↗
PubMed2003

Potential role of platelets in endothelial damage observed during treatment with cisplatin, gemcitabine, and the angiogenesis inhibitor SU5416.

PURPOSE: An increased incidence of thromboembolic events was observed during treatment with cisplatin-gemcitabine plus SU5416 (CG+SU5416), a tyrosine kinase inhibitor targeting the vascular endothelial growth factor (VEGF) receptor-1 and -2. Nine thromboembolic events occurred in eight of 19 patients. We performed an analysis of parameters of the coagulation cascade and vessel wall activation. MATERIALS AND METHODS: Markers for thrombin generation and endothelial cell activation were measured in three patients treated with CG+SU5416, two of whom developed a thromboembolic event. The results were compared with measurements in six patients treated with CG alone, and in 17 patients treated with SU5416 alone. RESULTS: During cycles 1 and 2 of treatment with CG+SU5416, a significant cycle-dependent activation of both the coagulation cascade and endothelial cells occurred, whereas platelet counts decreased. Change in platelet number had a significant negative predictive effect on soluble (s)-E-selectin levels. Significant activation of the coagulation cascade only was observed in the patients treated with CG alone, whereas in patients treated with SU5416 alone, significant endothelial cell activation was observed. CONCLUSION: We hypothesize that endothelial cells deprived of VEGF after exposure to SU5416 became activated and more susceptible to damage during treatment with CG+SU5416, which was aggravated by a transient decrease in platelets, which are, among other things, carriers of VEGF. These results suggests that VEGF, in addition to being a permeability, proliferation, and migration factor, also is a maintenance and protection factor for endothelial cells, and that platelets may have a role in maintaining vascular integrity.

Aged↗
PubMed2003

Role of platelet-derived endothelial cell growth factor/thymidine phosphorylase in fluoropyrimidine sensitivity.

Platelet-derived endothelial cell growth factor (PD-ECGF)/thymidine phosphorylase (TP) catalyses the reversible phosphorolysis of thymidine to thymine and 2-deoxyribose-1-phosphate and is involved in the metabolism of fluoropyrimidines. It can also activate 5'-deoxyfluorouridine (5'DFUR) and possibly 5-fluorouracil (5FU) and Ftorafur (Ft), but inactivates trifluorothymidine (TFT). We studied the contribution of TP activity to the sensitivity for these fluoropyrimidines by modulating its activity and/or expression level in colon and lung cancer cells using a specific inhibitor of TP (TPI) or by overproduction of TP via stable transfection of human TP. Expression was analysed using competitive template-RT-PCR (CT-RT-PCR), Western blot and an activity assay. TP activity ranged from nondetectable to 70678 pmol h(-1) 10(-6) cells, in Colo320 and a TP overexpressing clone Colo320TP1, respectively. We found a good correlation between TP activity and mRNA expression (r=0.964, P&<0.01) in our cell panel. To determine the role of TP in the sensitivity to 5FU, 5'DFUR, Ft and TFT, cells were cultured with the various fluoropyrimidines with or without TPI and differences in IC(50)'s were established. TPI modified 5'DFUR, increasing the IC(50)'s 2.5- to 1396-fold in WiDR and Colo320TP1, respectively. 5-Fluorouracil could be modified by inhibiting TP but to a lesser extent than 5'DFUR: IC(50)'s increased 1.9- to 14.7-fold for WiDR and Colo320TP1, respectively. There was no effect on TFT or Ft. There appears to be a threshold level of TP activity to influence the 5'DFUR and 5FU sensitivity, which is higher for 5FU. Even high levels of TP overexpression only had a moderate effect on 5FU sensitivity.

Antimetabolites↗
PubMed2003

Rapid disappearance of deoxyribose-1-phosphate in platelet derived endothelial cell growth factor/thymidine phosphorylase overexpressing cells.

Platelet derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP) catalyzes the phosphorolysis of thymidine (TdR) to thymine and deoxyribose-1-phosphate (dR-1-P) and has a pro-angiogenic effect for which dR-1-P may be responsible. Using a purine nucleoside phosphorylase based assay it was found that TdR incubation did not increase dR-1-P accumulation in colon cancer cell line Colo320 and its PD-ECGF/TP transfected variant Colo320TP1. The assay was linear up to 25,000pmol dR-1-P with complete recovery of dR-1-P from cellular extracts. There was a huge discrepancy between thymine production and the measured dR-1-P level, 0.05% of the expected value for dR-1-P was found, indicating that there was a rapid disappearance of dR-1-P. However, in cellular extracts, TdR incubation increased dR-1-P, measurable by trapping, which was inhibited by a thymidine phosphorylase inhibitor. dR-1-P directly added to cellular extracts disappeared within 5-10min. In conclusion, large amounts of dR-1-P are produced by Colo320TP1 cells, which rapidly disappear thus not resulting in a net accumulation of dR-1-P in these cells.

Cell Line↗
PubMed2003

Phase I and pharmacokinetic study of Yondelis (Ecteinascidin-743; ET-743) administered as an infusion over 1 h or 3 h every 21 days in patients with solid tumours.

Yondelis (ET-743) is a novel anticancer agent isolated from the marine ascidian Ecteinascidia turbinata. ET-743 possesses potent antitumour activity and a novel mechanism of action at the level of gene transcription. We conducted two sequential phase I dose escalation and pharmacokinetic studies of ET-743 given as a 1- or a 3-h intravenous (i.v.) infusion. Seventy-two adults with metastatic or advanced solid tumours received ET-743 in escalating doses between 50 and 1100 microg/m(2), initially as a 1-h infusion, and later at doses between 1000 and 1800 microg/m(2) as a 3-h infusion every 3 weeks. The maximum tolerated dose (MTD) of ET-743 was 1100 microg/m(2) for the 1-h infusion schedule and 1800 microg/m(2) when given as a 3-h infusion. Dose-limiting toxicities (DLTs) were fatigue, neutropenia and thrombocytopenia. Transient non-cumulatives grade 3-4 increase in transaminases (not considered DLT) and grades 3-4 nausea and vomiting were frequently observed. Other toxicities (maximum grade 3) included anaemia, increased lactate dehydrogenase (LDH), bilirubin and alkaline phosphatase serum levels, and phlebitis; there were no toxic deaths. One pCR (melanoma), CR (uterine leiomyosarcoma), one PR (colon stromal sarcoma) and a MR (37% tumour shrinkage, gastric stromal sarcoma) were observed. A further 9 patients with colorectal, mesothelioma, bile duct carcinoma and bladder cancer had SD which lasted for six or more treatment cycles. ET-743 pharmacokinetics were linear with the 3-h infusion schedule. The haematological and hepatic toxicities of ET-743 were dose-dependent and not cumulative. Based on the current trial, the recommended dose of ET-743 for phase II studies is 1650 microg/m(2) given as a 3-h infusion.

Adult↗
PubMed2003

Peripheral neuropathy due to therapy with paclitaxel, gemcitabine, and cisplatin in patients with advanced ovarian cancer.

BACKGROUND: To evaluate the peripheral neuropathic changes induced by combination chemotherapy including paclitaxel (taxol), gemcitabine and cisplatin (TGC regimen). PATIENTS AND METHODS: Eighteen patients with primary or recurrent ovarian cancer were treated with paclitaxel 150 or 110 mg/m2, respectively, together with gemcitabine 800 mg/m2 and cisplatin 75 mg/m2, 3 weekly for 6 cycles. Neurologic evaluation and quantitative assessment by vibration perception threshold (VPT) and grip strength took place before therapy, after 3 and 6 cycles of chemotherapy, and thereafter when possible. RESULTS: Both neuropathic symptoms and signs developed in all patients (100%), becoming most prominent 3 months after the last course of chemotherapy. Grade 3 peripheral neuropathy developed in one patient during chemotherapy, and in 3 additional patients after cessation of therapy. No significant differences were observed between chemo-naive patients and pretreated patients. CONCLUSION: This TGC combination is well tolerated in terms of peripheral neuropathy during therapy, although the off-therapy worsening caused by cisplatin remains a problem.

Adult↗
PubMed2003

VEGF and endostatin levels in wound fluid and plasma after breast surgery.

Angiogenesis is essential for wound repair after surgical trauma. Vascular endothelial growth factor (VEGF) and endostatin are endogenous angiogenic factors involved in the initiation and completion of angiogenesis. The aim of this study was to examine the local and systemic VEGF and endostatin profiles in patients undergoing surgery for benign and malignant breast processes. A total of 16 patients with or without cancer underwent breast surgery. Group I: eight patients with primary breast cancer underwent a simple or radical mastectomy according to Madden including dissection of axillary lymph nodes. Group II: eight healthy female-to-male transsexuals underwent subcutaneous mastectomy. VEGF and endostatin levels in plasma and wound fluid were determined. In both groups VEGF levels in wound fluid were significantly higher compared to postoperative plasma levels, whereas wound fluid endostatin levels were lower than plasma levels and decreased progressively after surgery. In both groups plasma VEGF and endostatin levels did not change significantly before and after surgery. The local VEGF increase and endostatin decrease observed immediately after surgery appears to be a physiological response to operative trauma, which can be studied more profoundly in locally generated fluid than in blood. This process did not seem to be influenced by the type of process (cancerous or non-cancerous) involved in the surgical intervention.

Breast Neoplasms↗
PubMed2002

Analysis of coagulation cascade and endothelial cell activation during inhibition of vascular endothelial growth factor/vascular endothelial growth factor receptor pathway in cancer patients.

OBJECTIVE: The angiogenesis inhibitor SU5416 is a potent inhibitor of vascular endothelial growth factor (VEGF) receptor-1 and -2. VEGF may be involved in hemostasis by altering the hemostatic properties of endothelial cells. We analyzed the effects of SU5416 on the coagulation cascade and the vessel wall in patients with advanced cancer. METHODS AND RESULTS: Markers for thrombin generation, activation of the protein C pathway, fibrinolysis, and endothelial cell activation were measured in patients with renal cell carcinoma, soft tissue sarcoma, or melanoma on days 0, 14, and 28 of treatment with SU5416. Three of 17 sampled patients developed a thromboembolic event in the fifth week of treatment. Markers for thrombin generation and fibrinolysis did not show significant changes. We observed a significant increase in endogenous thrombin potential and of parameters reflecting endothelial cell activation (von Willebrand antigen, soluble tissue factor, and soluble E-selectin) in all patients (P< or =0.001). In patients experiencing a thromboembolic event, endogenous thrombin potential, soluble tissue factor, and soluble E-selectin increased to a significantly greater extent (P=0.029, P=0.021, and P=0.007, respectively). CONCLUSIONS: VEGF is not only a permeability, proliferation, and migration factor, but it is also a maintenance and protection factor for endothelial cells.

Angiogenesis Inhibitors↗
PubMed2002

Treatment of haemangiopericytoma-associated hypoglycaemia with embolisation.

A 48-year-old woman with a known history of metastatic haemangiopericytoma presented with intractable hypoglycaemia. Hypoglycaemia was accompanied by undetectable serum insulin levels with high levels of proforms of insulin-like growth factor-II ('big' IGF-II). Reduction of tumour load with embolisation resulted in a normal pattern of serum glucose levels throughout the day.

Journal Article↗
PubMed2001

Granulocyte-macrophage colony-stimulating factor (GM-CSF) decreases left ventricular function. An echocardiographic study in cancer patients.

To study the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on the heart, echocardiographic assessments of left ventricular (LV) end-diastolic and end-systolic (ES) diameters (D), ejection fraction (EF) and cardiac output (CO) were done in six male patients (28-70 years of age) with advanced sarcoma (Group 1), prior to (day -1-0), during (day 7-9) and after (day 20-21) a first course of i.v. doxorubicin (day 0) without GM-CSF and a second course (3 weeks after the first one) with GM-CSF 250 microg/m(2)subcutaneously and daily from day 1-11. A similar study was done in ten female patients with advanced breast cancer (31-58 years of age, Group 2) for a first course of doxorubicin+cyclophosphamide with GM-CSF (same schedule as in Group 1). As compared to the mean of values prior to and after the course with GM-CSF in Group 1 and 2, the LVESD during GM-CSF administration transiently increased by median 6% (range -19 to 30%, P<0.05) vs -9% (-21 to 6%, not significant) in the first course without GM-CSF in Group 1 (P<0.05 between courses). The CO and EF tended to decrease during GM-CSF. GM-CSF thus causes a small and transient decrease of LV contractility.

Adult↗
PubMed2001

Pharmacologic study of paclitaxel administered with or without the cytoprotective agent amifostine, and given as a single agent or in combination with epirubicin and cisplatin in patients with advanced solid tumors.

The main purpose of this study was to investigate whether the coadministration of amifostine alters the pharmacokinetic behavior of paclitaxel. Eight patients were included in the study: six received paclitaxel in combination with epirubicin and cisplatin, and two received paclitaxel as a single agent. Doses of paclitaxel in these protocols were 135, 150, 175, and 200 mg/m(2) and two patients were treated at each dose level. Pharmacokinetic sampling for paclitaxel analysis was performed in each patient during two consecutive cycles, one with and one without amifostine (750 mg/m(2) as a 15-minute intravenous infusion 30 minutes before paclitaxel administration). At each dose level, the pharmacokinetic data of paclitaxel were compared per patient for a cycle without amifostine versus a cycle with amifostine. Amifostine did not seem to interact pharmacokinetically with paclitaxel, given either alone or in combination chemotherapy. This is in line with the clinical findings that amifostine has no negative effects on the antitumor activity of various antineoplastic agents. Also, amifostine may reduce toxic effects of combination chemotherapy regimens that include paclitaxel.

Amifostine↗
PubMed2000

Vascular endothelial growth factor-stimulated endothelial cells promote adhesion and activation of platelets.

Coagulation abnormalities, including an increased platelet turnover, are frequently found in patients with cancer. Because platelets secrete angiogenic factors on activation, this study tested the hypothesis that platelets contribute to angiogenesis. Stimulation with vascular endothelial growth factor (VEGF, 25 ng/mL) of human umbilical vein endothelial cells (HUVECs) promoted adhesion of nonactivated platelets 2.5-fold. In contrast, stimulation of HUVECs with basic fibroblast growth factor (bFGF) did not promote platelet adhesion. By blocking tissue factor (TF) activity, platelet adhesion was prevented and antibodies against fibrin(ogen) and the platelet-specific integrin, alpha(IIb)beta(3), inhibited platelet adhesion for 70% to 90%. These results indicate that VEGF-induced platelet adhesion to endothelial cells is dependent on activation of TF. The involvement of fibrin(ogen) and the alpha(IIb)beta(3) integrin, which exposes a high-affinity binding site for fibrin(ogen) on platelet activation, indicates that these adhering platelets are activated. This was supported by the finding that the activity of thrombin, a product of TF-activated coagulation and a potent platelet activator, was required for platelet adhesion. Finally, platelets at physiologic concentrations stimulated proliferation of HUVECs, indicative of proangiogenic activity in vivo. These results support the hypothesis that platelets contribute to tumor-induced angiogenesis. In addition, they may explain the clinical observation of an increased platelet turnover in cancer patients. Platelets may also play an important role in other angiogenesis-dependent diseases in which VEGF is involved, such as diabetes and autoimmune diseases. (Blood. 2000;96:4216-4221)

Adult↗
PubMed2000

[Added value of positron emission tomography with fluoro-18-deoxyglucose as the tracer (FDG-PET) in clinical problem cases in oncology].

Positron emission tomography with fluoro-18-deoxyglucose as tracer molecule (FDG-PET) is a relatively new imaging technique used in oncology to study tumour metabolism in vivo. Both qualitative and quantitative data obtained by PET provide unique information to the clinician and may guide the therapeutic approach in selected patients, where conventional diagnostic tests like CT or MRI yield equivocal results. According to the experience obtained in the Vrije Universiteit Medical Centre in Amsterdam, the additional value of FDG-PET can be explained by the sensitivity and the specificity of the technique, combined with the visualization of the whole body. FDG-PET may reveal metastases and tumour tissue may be differentiated from scar tissue and necrosis. PET is expensive and its effects on patient outcome has yet to be established.

Adult↗