Inducing intravesical hyperthermia of the ex-vivo porcine bladder wall: radiofrequency-induction versus recirculation using a custom-made device.

INTRODUCTION: Several techniques can be used to treat intravesical chemohyperthermia (ChHT). We compared radiofrequency-induced hyperthermia (RF-HT) with conductive hyperthermia (C-HT) for their ability to induce bladder wall temperatures of >40.5 °C, the target temperature for ChHT. MATERIALS AND METHODS: Fresh porcine bladders (n = 12) were placed in a temperature-controlled saline bath to simulate body temperature and circulation. HT was induced with RF-HT (43 °C) or C-HT (inflow temperature 44 and 46 °C) using a custom-made device. In two additional bladders, we varied intravesical solution and volume. Temperatures were recorded with a three-way catheter containing three mucosal and two urethral thermocouples (TCs) and a 915 MHz RF antenna, and with external TCs in the bladder wall at three different levels and three different locations. RESULTS: Target temperature (40.5 °C) was reached in the submucosa at all locations by both techniques. In the detrusor, target temperature was reached by RF-HT at the bladder neck and side wall. C-HT46 reached significantly higher submucosal temperatures at the side wall. The bladder dome seemed best heated by C-HT, although a high inflow temperature (46 vs. 44 °C) was required (ns). Intravesical saline resulted in higher temperatures than sterile water for RF-HT. A volume of 100 mL resulted in higher bladder dome temperatures for RF-HT, and higher bladder neck with lower dome temperatures for C-HT. CONCLUSION: Our results indicate a slightly superior heating capacity for RF-HT compared to C-HT, whereas for the bladder dome, the reverse seems true. Comparative studies are warranted to evaluate whether HT efficacy differs between both techniques, with emphasis on tumor location.

Health-related quality of life and its determinants in patients with metastatic renal cell carcinoma.

PURPOSE: Based on improvements of progression-free survival (PFS), new agents for metastatic renal cell carcinoma (mRCC) have been approved. It is assumed that one of the benefits is a delay in health-related quality of life (HRQoL) deterioration as a result of a delay in progression of disease. However, little data are available supporting this relationship. This study aims to provide insight into the most important determinants of HRQoL (including progression of disease) of patients with mRCC. METHODS: A patient registry (PERCEPTION) was created to evaluate treatment of patients with (m)RCC in the Netherlands. HRQoL was measured, using the EORTC QLQ-C30 and EQ-5D-5L, every 3 months in the first year of participation in the study, and every 6 months in the second year. Participation started as soon as possible following a diagnosis of (m)RCC. Random effects models were used to study associations between HRQoL and patient and disease characteristics, symptoms and treatment. RESULTS: Eighty-seven patients with mRCC completed 304 questionnaires. The average EORTC QLQ-C30 global health status was 69 (SD, 19) before progression and 61 (SD, 22) after progression of disease. Similarly, the average EQ-5D utility was 0.75 (SD, 0.19) before progression and 0.66 (SD, 0.30) after progression of disease. The presence of fatigue, pain, dyspnoea, and the application of radiotherapy were associated with significantly lower EQ-5D utilities. CONCLUSIONS: Key drivers for reduced HRQoL in mRCC are disease symptoms. Since symptoms increase with progression of disease, targeted therapies that increase PFS are expected to postpone reductions in HRQoL in mRCC.

Variation in use of targeted therapies for metastatic renal cell carcinoma: Results from a Dutch population-based registry.

BACKGROUND: For patients with metastatic renal cell carcinoma (mRCC), targeted therapies have entered the market since 2006. The aims of this study were to evaluate the uptake and use of targeted therapies for mRCC in The Netherlands, examine factors associated with the prescription of targeted therapies in daily clinical practice and study their effectiveness in terms of overall survival (OS). METHODS: Two cohorts from PERCEPTION, a population-based registry of mRCC patients, were used: a 2008-2010 Cohort (n = 645) and a 2011-2013 Cohort (n = 233). Chi-squared tests for trend were used to study time trends in the use of targeted therapy. Patients were grouped based on the eligibility criteria of the SUTENT trial, the trial that led to sunitinib becoming standard of care, to investigate the use of targeted therapies amongst patients fulfilling those criteria. Multi-level logistic regression was used to identify patient subgroups that are less likely to receive targeted therapies. RESULTS: Approximately one-third of patients fulfilling SUTENT trial eligibility criteria did not receive any targeted therapy (29 % in the 2008-2010 Cohort; 35 % in the 2011-2013 Cohort). Patients aged 65+ years were less likely to receive targeted therapy in both cohorts and different risk groups (odds ratios range between 0.84-0.92); other factors like number of metastatic sites were of influence in some subgroups. Amongst treated patients, there was a decreasing trend in sunitinib use over time (p = 0.0061), and an increasing trend in pazopanib use (p = 0.0005). CONCLUSIONS: Targeted therapies have largely replaced interferon-alfa as first-line standard of care. Nevertheless, many eligible patients in Dutch daily practice did not receive targeted therapies despite their ability to improve survival. Reasons for their apparent underutilisation should be examined more carefully.

Scaffold-based tissue engineering: Supercritical carbon dioxide as an alternative method for decellularization and sterilization of dense materials.

Development of ready-to-use biomaterials and scaffolds is vital for further advancement of scaffold-based tissue engineering in clinical practice. Scaffolds need to mimic 3D ultrastructure, have adequate mechanical strength, are biocompatible, non-immunogenic and need to promote tissue regeneration in vivo. Although decellularization of native tissues seems promising to deliver scaffolds that meet these criteria, adequate decellularization of hard, poorly penetrable and poorly diffusible tissues remains challenging whilst being a very time-consuming process. In this study, a method to decellularize hard, dense tissues using supercritical carbon-dioxide preceded by a freeze/thaw cycle and followed by several washing steps is presented, demonstrating decellularisation efficiency and substantially reduced production/handling time. Additionally, supercritical carbon-dioxide treatment was used as sterilization method, further reducing the time required to produce the final scaffold. Histological evaluation showed that, after fine-tuning of the process, a partially acellular scaffold was obtained, with preservation of glycosaminoglycans and collagen fibers, albeit that the amount of residual dsDNA was still higher then chemically decellularized tissue. Biomechanical properties of the scaffold were similar to the native, non-decellularized tissue. After sterilization with supercritical carbon-dioxide the simulated functional outcome was more similar to native trachea, when compared to sterilization using gamma irradiation. Thus, decellularization and sterilization using supercritical carbon-dioxide with washing steps is an effective method for dense cartilaginous materials, and tuneable to meet different demands in other applications, but further optimization may be required. STATEMENT OF SIGNIFICANCE: Further advancement of the use of tissue engineered tracheal constructs is restricted by the lack of the ideal scaffold. Decellularized trachea is considered a promising scaffold, but the hard, poorly diffusible tissue remains challenging while forming a very time consumable process. Decellularization using supercritical carbon dioxide (scCO2) seems promising, resulting in efficient removal of cellular material while reducing production and handling time. Addition of scCO2 as a sterilization method resulted in further time reduction while improving functional outcome in comparison with traditional sterilization methods. This study presents an promising alternative method for decellularization and sterilization of dense materials, which can be tuned to meet different demands in other applications.

Carbonic anhydrase IX is a predictive marker of doxorubicin resistance in early-stage breast cancer independent of HER2 and TOP2A amplification.

BACKGROUND: In early-stage breast cancer, adjuvant chemotherapy is associated with significant systemic toxicity with only a modest survival benefit. Therefore, there is considerable interest in identifying predictive markers of response to therapy. Doxorubicin, one of the most common drugs used to treat breast cancer, is an anthracycline chemotherapeutic agent, a class of drugs known to be affected by hypoxia. Accordingly, we examined whether expression of the endogenous hypoxia marker carbonic anhydrase IX (CA IX) is predictive of outcome in early-stage breast cancer patients treated with doxorubicin. METHODS: We obtained 209 early-stage pre-treatment surgically-resected breast tumours from patients, who received doxorubicin in their chemotherapeutic regimen and had >10 years of follow-up. Immunohistochemistry was used to detect CA IX, and we used fluorescence in situ hybridisation to detect both human epidermal growth factor receptor (HER2) and DNA topoisomerase II-alpha (TOP2A) gene amplification. RESULTS: Carbonic anhydrase IX intensity was significantly correlated with progression-free survival (PFS) and overall survival (OS) in patients receiving 300 mg m(-2) of doxorubicin (HR=1.82 and 3.77; P=0.0014 and 0.010, respectively). There was a significant, inverse correlation between CA IX score and oestrogen receptor expression, but no significant correlations were seen with either HER2 or TOP2A ratio. CONCLUSION: We demonstrate that CA IX expression is correlated with worse PFS and OS for breast cancer patients treated with doxorubicin, independent of HER2 or TOP2A gene amplification. This study provides evidence that using CA IX to detect hypoxia in surgically-resected breast tumours may be of clinical use in choosing an appropriate chemotherapy regimen.

Bone tumor-targeted delivery of theranostic 195mPt-bisphosphonate complexes promotes killing of metastatic tumor cells.

Platinum-based drugs such as cisplatin are very potent chemotherapeutics, whereas radioactive platinum (195mPt) is a rich source of low-energy Auger electrons, which kills tumor cells by damaging DNA. Auger electrons damage cells over a very short range. Consequently, 195mPt-based radiopharmaceuticals should be targeted toward â€‹tumors to maximize radiotherapeutic efficacy and minimize Pt-based systemic toxicity. Herein, we show that systemically administered radioactive bisphosphonate-functionalized platinum (195mPt-BP) complexes specifically accumulate in intratibial bone metastatic lesions in mice. The 195mPt-BP complexes accumulate 7.3-fold more effectively in bone 7 days after systemic delivery compared to 195mPt-cisplatin lacking bone-targeting bisphosphonate ligands. Therapeutically, 195mPt-BP treatment causes 4.5-fold more γ-H2AX formation, a biomarker for DNA damage in metastatic tumor cells compared to 195mPt-cisplatin. We show that systemically administered 195mPt-BP is radiotherapeutically active, as evidenced by an 11-fold increased DNA damage in metastatic tumor cells compared to non-radioactive Pt-BP controls. Moreover, apoptosis in metastatic tumor cells is enhanced more than 3.4-fold upon systemic administration of 195mPt-BP vs. radioactive 195mPt-cisplatin or non-radioactive Pt-BP controls. These results provide the first preclinical evidence for specific accumulation and strong radiotherapeutic activity of 195mPt-BP in bone metastatic lesions, which offers new avenues of research on radiotherapeutic killing of tumor cells in bone metastases by Auger electrons.

Curcumin as Treatment for Bladder Cancer: A Preclinical Study of Cyclodextrin-Curcumin Complex and BCG as Intravesical Treatment in an Orthotopic Bladder Cancer Rat Model.

OBJECTIVE: To evaluate the antitumor effect of cyclodextrin-curcumin complex (CDC) on human and rat urothelial carcinoma cells in vitro and to evaluate the effect of intravesical instillations of CDC, BCG, and the combination in vivo in the AY-F344 orthotopic bladder cancer rat model. Curcumin has anticarcinogenic activity on urothelial carcinoma and is therefore under investigation for the treatment of non-muscle invasive bladder cancer. Curcumin and BCG share immunomodulating pathways against urothelial carcinoma. METHODS: Curcumin was complexed with cyclodextrin to improve solubility. Four human urothelial carcinoma cell lines and the AY-27 rat cell line were exposed to various concentrations of CDC in vitro. For the in vivo experiment, the AY-27 orthotopic bladder cancer F344 rat model was used. Rats were treated with consecutive intravesical instillations of CDC, BCG, the combination of CDC+BCG, or NaCl as control. RESULTS: CDC showed a dose-dependent antiproliferative effect on all human urothelial carcinoma cell lines tested and the rat AY-27 urothelial carcinoma cell line. Moreover, intravesical treatment with CDC and CDC+BCG results in a lower percentage of tumors (60% and 68%, respectively) compared to BCG (75%) or control (85%). This difference with placebo was not statistically significant (p=0.078 and 0.199, respectively). However, tumors present in the placebo and BCG-treated rats were generally of higher stage. CONCLUSIONS: Cyclodextrin-curcumin complex showed an antiproliferative effect on human and rat urothelial carcinoma cell lines in vitro. In the aggressive orthotopic bladder cancer rat model, we observed a promising effect of CDC treatment and CDC in combination with BCG.

Potential health gains for patients with metastatic renal cell carcinoma in daily clinical practice: A real-world cost-effectiveness analysis of sequential first- and second-line treatments.

INTRODUCTION: Randomised controlled trials have shown that targeted therapies like sunitinib are effective in metastatic renal cell carcinoma (mRCC). Little is known about the current use of these therapies, and their associated costs and effects in daily clinical practice. We estimated the real-world cost-effectiveness of different treatment strategies comprising one or more sequentially administered drugs. METHODS: Analyses were performed using patient-level data from a Dutch population-based registry including patients diagnosed with primary mRCC from January 2008 to December 2010 (i.e., treated between 2008 and 2013). The full disease course of these patients was estimated using a patient-level simulation model based on regression analyses of the registry data. A healthcare sector perspective was adopted; total costs included healthcare costs related to mRCC. Cost-effectiveness was expressed in cost per life-year and cost per quality-adjusted life-year (QALY) gained. Probabilistic sensitivity analysis was conducted to estimate the overall uncertainty surrounding cost-effectiveness. RESULTS: In current daily practice, 54% (336/621) of all patients was treated with targeted therapies. Most patients (84%; 282/336) received sunitinib as first-line therapy. Of the patients receiving first-line therapy, 30% (101/336) also received second-line therapy; the majority was treated with everolimus (40%, 40/101) or sorafenib (28%, 28/101). Current treatment practice (including patients not receiving targeted therapy) led to 0.807 QALYs; mean costs were €58,912. This resulted in an additional €105,011 per QALY gained compared to not using targeted therapy at all. Forty-six percent of all patients received no targeted therapy; of these patients, 24% (69/285) was eligible for sunitinib. If these patients were treated with first-line sunitinib, mean QALYs would improve by 0.062-0.076 (where the range reflects the choice of second-line therapy). This improvement is completely driven by the health gain seen amongst patients eligible to receive sunitinib but did not receive it, who gain 0.558-0.684 QALYs from sunitinib. Since additional costs would be €7,072-9,913, incremental costs per QALY gained are €93,107-111,972 compared to current practice. DISCUSSION: Health can be gained if more treatment-eligible patients receive targeted therapies. Moreover, it will be just as cost-effective to treat these patients with sunitinib as current treatment practice.

Bioinspired coupled helical coils for soft tissue engineering of tubular structures - Improved mechanical behavior of tubular collagen type I templates.

The design of constructs for tubular tissue engineering is challenging. Most biomaterials need to be reinforced with supporting structures such as knittings, meshes or electrospun material to comply with the mechanical demands of native tissues. In this study, coupled helical coils (CHCs) were manufactured to mimic collagen fiber orientation as found in nature. Monofilaments of different commercially available biodegradable polymers were wound and subsequently fused, resulting in right-handed and left-handed polymer helices fused together in joints where the filaments cross. CHCs of different polymer composition were tested to determine the tensile strength, strain recovery, hysteresis, compressive strength and degradation of CHCs of different composition. Subsequently, seamless and stable hybrid constructs consisting of PDSII® USP 2-0 CHCs embedded in porous collagen type I were produced. Compared to collagen alone, this hybrid showed superior strain recovery (93.5±0.9% vs 71.1±12.6% in longitudinal direction; 87.1±6.6% vs 57.2±4.6% in circumferential direction) and hysteresis (18.9±2.7% vs 51.1±12.0% in longitudinal direction; 11.5±4.6% vs 46.3±6.3% in circumferential direction). Furthermore, this hybrid construct showed an improved Young's modulus in both longitudinal (0.5±0.1MPavs 0.2±0.1MPa; 2.5-fold) and circumferential (1.65±0.07MPavs (2.9±0.3)×10-2MPa; 57-fold) direction, respectively, compared to templates created from collagen alone. Moreover, hybrid template characteristics could be modified by changing the CHC composition and CHCs were produced showing a mechanical behavior similar to the native ureter. CHC-enforced templates, which are easily tunable to meet different demands may be promising for tubular tissue engineering. STATEMENT OF SIGNIFICANCE: Most tubular constructs lack sufficient strength and tunability to comply with the mechanical demands of native tissues. Therefore, we embedded coupled helical coils (CHCs) produced from biodegradable polymers - to mimic collagen fiber orientation as found in nature - in collagen type I sponges. We show that the mechanical behavior of CHCs is very similar to native tissue and strengths structurally weak tubular constructs. The production procedure is relatively easy, reproducible and mechanical features can be controlled to meet different mechanical demands. This is promising in template manufacture, hence offering new opportunities in tissue engineering of tubular organs and preventing graft failure.

A theranostic dental pulp capping agent with improved MRI and CT contrast and biological properties.

Different materials have been used for vital dental pulp treatment. Preferably a pulp capping agent should show appropriate biological performance, excellent handling properties, and a good imaging contrast. These features can be delivered into a single material through the combination of therapeutic and diagnostic agents (i.e. theranostic). Calcium phosphate based composites (CPCs) are potentially ideal candidate for pulp treatment, although poor imaging contrast and poor dentino-inductive properties are limiting their clinical use. In this study, a theranostic dental pulp capping agent was developed. First, imaging properties of the CPC were improved by using a core-shell structured dual contrast agent (csDCA) consisting of superparamagnetic iron oxide (SPIO) and colloidal gold, as MRI and CT contrast agent respectively. Second, biological properties were implemented by using a dentinogenic factor (i.e. bone morphogenetic protein 2, BMP-2). The obtained CPC/csDCA/BMP-2 composite was tested in vivo, as direct pulp capping agent, in a male Habsi goat incisor model. Our outcomes showed no relevant alteration of the handling and mechanical properties (e.g. setting time, injectability, and compressive strength) by the incorporation of csDCA particles. In vivo results proved MRI contrast enhancement up to 7weeks. Incisors treated with BMP-2 showed improved tertiary dentin deposition as well as faster cement degradation as measured by µCT assessment. In conclusion, the presented theranostic agent matches the imaging and regenerative requirements for pulp capping applications. STATEMENT OF SIGNIFICANCE: In this study, we combined diagnostic and therapeutic agents in order to developed a theranostic pulp capping agent with enhanced MRI and CT contrast and improved dentin regeneration ability. In our study we cover all the steps from material preparation, mechanical and in vitro characterization, to in vivo study in a goat dental model. To the best of our knowledge, this is the first time that a theranostic pulp capping material have been developed and tested in an in vivo animal model. Our promising results in term of imaging contrast enhancement and of induction of new dentin formation, open a new scenario in the development of innovative dental materials.

Population Modeling Integrating Pharmacokinetics, Pharmacodynamics, Pharmacogenetics, and Clinical Outcome in Patients With Sunitinib-Treated Cancer.

The tyrosine kinase inhibitor sunitinib is used as first-line therapy in patients with metastasized renal cell carcinoma (mRCC), given in fixed-dose regimens despite its high variability in pharmacokinetics (PKs). Interindividual variability of drug exposure may be responsible for differences in response. Therefore, dosing strategies based on pharmacokinetic/pharmacodynamic (PK/PD) models may be useful to optimize treatment. Plasma concentrations of sunitinib, its active metabolite SU12662, and the soluble vascular endothelial growth factor receptors sVEGFR-2 and sVEGFR-3, were measured in 26 patients with mRCC within the EuroTARGET project and 21 patients with metastasized colorectal cancer (mCRC) from the C-II-005 study. Based on these observations, PK/PD models with potential influence of genetic predictors were developed and linked to time-to-event (TTE) models. Baseline sVEGFR-2 levels were associated with clinical outcome in patients with mRCC, whereas active drug PKs seemed to be more predictive in patients with mCRC. The models provide the basis of PK/PD-guided strategies for the individualization of anti-angiogenic therapies.

Complex cadherin expression in renal cell carcinoma.

E-cadherin is an intercellular adhesion protein expressed by most epithelia. Decreased expression of E-cadherin correlates with tumor aggressiveness in most carcinomas. In renal cell carcinoma (RCC), however, this correlation is not well established and the prevalence of negative tumors is higher than in other carcinomas. Our immunofluorescence study of alpha-catenin expression in 20 RCC cell lines revealed a typical honeycomb staining pattern in all of the lines, whereas only six expressed E-cadherin. This suggested that other cadherins are expressed in RCC lines. Indeed, immunoprecipitation with an anti-alpha-catenin antibody resulted in coprecipitation of proteins of Mr 125,000-135,000. Using Western blot, these proteins react with a pan-cadherin antibody. To identify these cadherin related proteins, RT-PCR using degenerated primers and sequence comparisons was carried out. We then assessed the expression of the identified cadherins. N-cadherin mRNA was present in all cell lines; and cadherin 6 mRNA was seen in 16 lines. Cadherin 11 (mRNA) and E-cadherin (protein) were expressed in five and six lines, respectively. A cadherin 4 transcript was observed in only one line, whereas no P-cadherin protein could be detected. Expression of the four main cadherins was also found in normal kidney (two samples tested) and RCC specimens (four samples). Thus, RCC and normal kidney express a complex set of cadherins.

The renal cell carcinoma-associated antigen G250 encodes a human leukocyte antigen (HLA)-A2.1-restricted epitope recognized by cytotoxic T lymphocytes.

Evidence has accumulated that the immune system can play a significant role in the defense against tumors in humans. Especially melanoma and renal cell carcinoma (RCC) are considered immunogenic tumors. In contrast to melanoma, hardly any RCC-associated antigens have been identified as targets for RCC-reactive T cells. Here, we report the identification of a human leukocyte antigen (HLA)-A2.1-restricted T-cell epitope within the G250 antigen. This antigen is expressed in 85% of RCCs but not by neighboring normal kidney tissue and has recently been molecularly defined and shown to be identical to MN/CA IX. Computer-aided motif prediction revealed the presence of 60 potential HLA-A2.1-binding peptides within the G250 antigen. Subsequent binding analysis showed that 13 of these peptides bound to HLA-A2.1 with high-to-intermediate affinity. Analysis of their immunogenicity in HLA-A2.1Kb transgenic mice indicated that 4 of the 13 peptides gave rise to cytotoxic T lymphocytes (CTLs) capable of lysing peptide-loaded target cells. However, only the G250 peptide 254-262 induced CTLs that recognized target cells that endogenously expressed the G250 antigen. Similarly, we were also able to raise human CTLs against the G250 peptide 254-262, which lysed target cells that endogenously expressed the G250 antigen. These findings and the high prevalence of this antigen in RCC patients makes G250 a potential target for anti-RCC immunotherapy.

Development and characterization of anti-renal cell carcinoma x antichelate bispecific monoclonal antibodies for two-phase targeting of renal cell carcinoma.

To test a two-step approach for radioimmunotargeting of renal cell cancer, quadroma cells secreting antichelate x anti-renal cell carcinoma bispecific antibodies were obtained by somatic cell fusion. Five monoclonal antibodies against the chelate 1,4,7-triazaheptane-N,N',N"-pentaacetic acid (DTPA) were produced and characterized. Competitive binding assays indicated that the anti-DTPA antibodies reacted with DTPA chelated with indium, yttrium, chromium, iron, or zinc. The affinity constants of the anti-DTPA antibodies for 111In-DTPA ranged from 0.19 to 0.23 nM-1. Using different chelates, a remarkable chelate specificity of the anti-DTPA antibodies was demonstrated. The chelates recognized by the antibodies DTIn1, DTIn2, and DTIn4 share a N(N")-diacetic acid group, whereas the chelates recognized by DTIn3 share a N'-acetic acid group, suggesting the presence of different essential structures within the DTPA molecule that determine the reactivity of the antibodies. Five anti-DTPA antibody-producing hybridomas were used for somatic cell fusion with hybridoma G250 directed against renal cell carcinoma, resulting in three bispecific antibody-producing quadroma cell lines. The bispecific monoclonal antibodies were purified from ascites fluid using protein A affinity chromatography followed by hydroxylapatite chromatography and/or cation exchange chromatography. Of the total IgG amount present in the ascites fluid, 10-15% represented the bispecific antibodies. These bispecific antibodies will allow testing and optimization of a two-step approach for radioimmunotargeting of chelated radionuclides.

Intratumoral distribution of two consecutive injections of chimeric antibody G250 in primary renal cell carcinoma: implications for fractionated dose radioimmunotherapy.

Tumor uptake of the chimeric G250 (cG250) monoclonal antibody (mAb) in patients with primary renal cell carcinoma (RCC) is among the highest reported in solid tumors. However, as observed in other tumor types, the intratumoral distribution of the antibody is highly heterogeneous, which may limit the efficacy of radioimmunotherapy. A number of highly dynamic physiological factors have been postulated that may contribute to heterogeneous tumor uptake of antibodies. Their impact on tumor uptake of antibodies may vary from one tumor region to another as well as from one day to the next. Here, we report on a clinical study that was designed to investigate whether the pattern of mAb cG250 uptake within RCC tumors is altered with subsequent injections. Ten patients with a clinical diagnosis of primary RCC were studied. Nine days before surgery, patients received 125I-cG250 (5 mg of cG250, 50 microCi of 125I), followed by a second injection of 131I-cG250 (5 mg of cG250, 3.5 mCi of 131I) 4 days later. Postsurgery, the tumor was cut into (1-cm) thick slices. Slices were imaged on a gamma camera, and the slice with the most pronounced heterogeneity in 131I-cG250 distribution was selected and cut into 1-cm3 cubes. Each cube was analyzed for 121I-cG250 and 131I-cG250 uptake, and the 131I/125I ratio was determined. For each tumor slice, the distribution patterns of both isotopes were reconstructed and compared with each other. All tumors analyzed showed a heterogeneous distribution of both isotopes throughout the tumor slice; focal uptake in some areas of a tumor reached very high levels (up to 0.19% injected dose/g), whereas other tumorous areas of the same slice showed much lower uptake (as low as 0.0047% injected dose/g). Remarkably, in all tumors, the distribution pattern of both injections was identical: without exception, in all samples analyzed (n = 692), the uptake of 125I-cG250 was similar to 131I-cG250 uptake. Overall, the 131I/125I ratio was 1.64+/-0.31 (mean+/-SD). The constant 131I/125I ratios, observed in all tumor samples investigated, indicate that the tumor parameters governing cG250 mAb uptake were not altered significantly within the time period studied. In addition, the results of this study suggest that multiple radiolabeled antibody injections, administered within short time periods, will target the same areas within a tumor and, thus, will not solve the problem of heterogeneous tumor uptake of antibody.

Pretargeting of renal cell carcinoma: improved tumor targeting with a bivalent chelate.

Radiolabeled monoclonal antibodies (mAbs) can target tumors selectively. Sustained activity levels in nontarget tissues limit their application. Pretargeting approaches using bispecific mAbs (bsmAbs) or the biotinavidin interaction have been proposed to improve tumor:nontumor ratios. Pretargeting a tumor and subsequently administering the radioactivity as a low molecular weight ligand fundamentally changes the pharmacokinetics of the radiolabel. In previous studies, we have shown successful radioimmunotargeting of diethylenetriaminepentaacetic acid (DTPA) labeled with indium-111 to renal cell carcinoma (RCC) after pretargeting in nude mice. In this study, we aimed to optimize further a pretargeting strategy in nude mice with RCC xenografts based on a bispecific anti-RCC x anti-DTPA mAb. Using this two-step approach, we studied whether the use of a bivalent chelate ((111)In-diDTPA) could improve radioimmunotargeting. The (111)In-diDTPA dose greatly affected the uptake of the radiolabeled chelate in the tumor. At a low (111)In-diDTPA dose (< or = 7 pmol), tumor uptake of (111)In-diDTPA was very high [>50% injected dose (ID)/g, 1 h postinjection (p.i.)], whereas at higher doses (> or = 20 pmol), tumor uptake of (111)In-diDTPA decreased (<30% ID/g). With monovalent (111)In-DTPA uptake of the radiolabel in the tumor was much lower (<10% ID/g, 1 h p.i.). Furthermore, the bivalent chelate accreted rapidly in the tumor (78% ID/g, 4 h p.i.) and was virtually completely retained in the tumor during several days p.i. (92% ID/g, 72 h p.i.). Clearance of the (111)In-diDTPA from the blood and kidneys was rapid and complete without the need to clear the bsmAb from the blood, probably due to the relative lability of the univalent bsmAb-diDTPA complexes in the blood. As a result, with this two-step pretargeting approach tumor:blood ratios increased up to values as high as 3500 at 72 h p.i. High doses of diDTPA could be targeted preferentially to the tumor, indicating that this approach could also be used for radioimmunotherapy. Tumors could be imaged up to 1 week p.i. of 50 microCi of (111)In-diDTPA. Quantitative analysis of the images confirmed the biodistribution data and indicated that, at 20 h p.i., 50 +/- 15% of the whole-body activity was localized in the tumor. In conclusion, these studies indicate that the use of bivalent chelates can very effectively optimize two-step targeting of tumors with bsmAbs. Our data indicate that this approach could optimize radioimmunotherapy.

Antibody localization in human renal cell carcinoma: a phase I study of monoclonal antibody G250.

PURPOSE: To define the imaging and biodistribution characteristics of iodine 131-labeled monoclonal antibody (mAb) G250 (131I-mAbG250), which recognizes a cell-surface antigen expressed by human renal cell carcinoma (RCC). PATIENTS AND METHODS: G250 is a cell-surface antigen recognized by mAbG250 expressed by RCC but not detected in normal kidney. Clear-cell RCC, the most frequent form of RCC, shows homogeneous expression of G250, whereas non-clear-cell RCC and cancers derived from other organs generally do not express G250. Expression in normal tissues is highly restricted and limited to large bile ducts and gastric epithelium. 131I-mAbG250 was administered intravenously (IV) to 16 patients with RCC 7 to 8 days before surgery at five dose levels, with at least three patients entered at each dose level. RESULTS: Clear tumor images were observed in 12 patients with G250-positive tumors and in one of three patients with G250-negative tumors. Imaged lesions in the peritoneal cavity were confirmed at surgery. The smallest lesion visualized was 8 mm in diameter. The specificity of 131I-mAbG250 localization to tumor tissue was established by radioactivity measurements, autoradiography, and immunohistochemistry of biopsied tissues, and technetium 99-human serum albumin blood-flow studies. The fraction of the injected 131I-mAbG250 dose per gram tumor (%ID/g tumor) localized in G250-positive tumors showed a broad range, but reached levels as high as 0.02% to 0.12%. CONCLUSION: 131I-mAbG250 localized specifically to G250 antigen-positive RCC and seems to have considerable potential as an imaging agent in RCC patients. 131I-mAbG250 uptake in the tumors, relative as well as absolute, are among the highest reported for tumor biopsies obtained 8 days after IV mAb administration. Based on the specific localization and high accumulation, mAb G250 may have therapeutic potential.

Targeting of renal cell carcinoma with iodine-131-labeled chimeric monoclonal antibody G250.

PURPOSE: Pharmacokinetics, biodistribution, immunogenicity, and imaging characteristics of iodine 131 (131I)-labeled chimeric monoclonal antibody (mAb) G250 (cG250) were studied in patients with renal cell carcinoma (RCC) to determine the therapeutic potential of this antibody. PATIENTS AND METHODS: Sixteen patients with RCC received a single intravenous (IV) infusion of 6 mCi 131I-labeled cG250. Five protein dose levels were investigated (2 to 50 mg). Planar scintigraphic images were acquired, and normal tissue biopsies and tumor samples were obtained of surgery (7 days postinjection). The immunogenicity of cG250 was investigated using a sandwich enzyme-linked immunosorbent assay (ELISA) and dosimetric analysis was performed. RESULTS: In all patients with antigen-positive tumors (n = 13), the primary tumors and all known metastases were clearly visualized. Overall uptake, expressed as the percentage of the injected dose (%ID), in the primary tumors ranged from 2.4 to 9.0. Focally, 131I-cG250 uptake as high as 0.52% ID/g was observed. However, intratumoral uptake was highly heterogeneous. 131I-cG250 uptake in nontumorous tissues remained low. Dosimetric analysis showed that up to .48 Gy/mCi was guided to the primary tumors. Selected "hot areas" within these tumors received up to .72 Gy/mCi. A bone metastasis received .23 Gy/mCi and regional lymph node metastases received .20 Gy/mCi. Minimal human antichimeric antibody (HACA) levels were detected in two of 16 patients. CONCLUSION: 131I-cG250 tumor uptake is among the highest reported in clinical studies with antitumor antibodies in solid tumors. Since tumor-sterilizing levels may be guided to the tumor when high doses 131I-cG250 are administered (> 100 mCi) and cG250 appears to be immunosilent, cG250 is a promising vehicle for radioimmunotherapy in RCC.

Expression of cadherin-6 as a novel diagnostic tool to predict prognosis of patients with E-cadherin-absent renal cell carcinoma.

In many carcinomas, E-cadherin is considered to be a prognostic marker for patient survivals, and its decreased expression is associated with metastatic disease. Among renal cell carcinomas (RCCs), however, only 20% of tumors express E-cadherin, whereas a much higher percentage express other cadherins, e.g., N-cadherin and cadherin-6 (T. Shimazui et al, Cancer Res., 56: 3234-3237, 1996). Among these cadherins expressed in RCCs, cadherin-6 has been identified as a major cadherin in the renal proximal tubules and in the tumors themselves. Hence, we have investigated the relationship between prognosis and cadherin-6 expression in tumor cells in 43 patients with RCC. Expression of cadherin-6, E-cadherin, and alpha-catenin was detected immunohistochemically and evaluated microscopically as normal, heterogeneous, or absent. Normal, heterogeneous, and absent expression of cadherin-6 were observed in 19, 16, and 8 of 43 cases, respectively. Coexpression of E-cadherin and cadherin-6 was detected in only 10 cases. Among 30 tumors in which E-cadherin expression was absent, 24 expressed cadherin-6. In addition, the expression pattern of alpha-catenin correlated more highly with that of cadherin-6 than it did with E-cadherin (P = 0.0003 versus 0.025). In survival analyses, aberrant expression of cadherin-6 correlated with poor survivals both among all patients (P = 0.0009) and in those with E-cadherin-absent RCC (P = 0.0008). These results suggest that cadherin-6 is a major cadherin playing an essential role in cell-cell adhesion in E-cadherin-absent RCC.