Towards Cancer Nanoradiopharmaceuticals-Radioisotope Nanocarrier System for Prostate Cancer Theranostics Based on Radiation-Synthesized Polymer Nanogels.

Despite the tremendous development of oncology, prostate cancer remains a debilitating malignancy. One of the most promising approaches to addressing this issue is to exploit the advancements of nanomedicine in combination with well-established nuclear medicine and radiotherapy. Following this idea, we have developed a radioisotope nanocarrier platform of electron-beam-synthesized nanogels based on poly(acrylic acid). We have developed a functionalization protocol, showing the very high (>97%) efficiency of the conjugation in targeting a ligand-bombesin derivative. This engineered peptide can bind gastrin-releasing peptide receptors overexpressed in prostate cancer cells; moreover, it bears a radioisotope-chelating moiety. Our nanoplatform exhibits very promising performance in vitro; the radiolabeled nanocarriers maintained high radiochemical purity of >90% in both the labeling buffer and human serum for up to 14 days. The application of the targeted nanocarrier allowed also effective and specific uptake in PC-3 prostate cancer cells, up to almost 30% after 4 h, which is a statistically significant improvement in comparison to carrier-free radiolabeled peptides. Although our system requires further studies for more promising results in vivo, our study represents a vital advancement in radionanomedicine-one of many steps that will lead to effective therapy for castration-resistant prostate cancer.

Nanostrategies for Therapeutic and Diagnostic Targeting of Gastrin-Releasing Peptide Receptor.

Advances in nanomedicine bring the attention of researchers to the molecular targets that can play a major role in the development of novel therapeutic and diagnostic modalities for cancer management. The choice of a proper molecular target can decide the efficacy of the treatment and endorse the personalized medicine approach. Gastrin-releasing peptide receptor (GRPR) is a G-protein-coupled membrane receptor, well known to be overexpressed in numerous malignancies including pancreatic, prostate, breast, lung, colon, cervical, and gastrointestinal cancers. Therefore, many research groups express a deep interest in targeting GRPR with their nanoformulations. A broad spectrum of the GRPR ligands has been described in the literature, which allows tuning of the properties of the final formulation, particularly in the field of the ligand affinity to the receptor and internalization possibilities. Hereby, the recent advances in the field of applications of various nanoplatforms that are able to reach the GRPR-expressing cells are reviewed.

[99mTc]Tc-PSMA-T4-Novel SPECT Tracer for Metastatic PCa: From Bench to Clinic.

Despite significant advances in nuclear medicine for diagnosing and treating prostate cancer (PCa), research into new ligands with increasingly better biological properties is still ongoing. Prostate-specific membrane antigen (PSMA) ligands show great potential as radioisotope carriers for the diagnosis and therapy of patients with metastatic PCa. PSMA is expressed in most types of prostate cancer, and its expression is increased in poorly differentiated, metastatic, and hormone-refractory cancers; therefore, it may be a valuable target for the development of radiopharmaceuticals and radioligands, such as urea PSMA inhibitors, for the precise diagnosis, staging, and treatment of prostate cancer. Four developed PSMA-HYNIC inhibitors for technetium-99m labeling and subsequent diagnosis were subjected to preclinical in vitro and in vivo studies to evaluate and compare their diagnostic properties. Among the studied compounds, the PSMA-T4 (Glu-CO-Lys-L-Trp-4-Amc-HYNIC) inhibitor showed the best biological properties for the diagnosis of PCa metastases. [99mTc]Tc-PSMA-T4 also showed effectiveness in single-photon emission computed tomography (SPECT) studies in humans, and soon, its usefulness will be extensively evaluated in phase 2/3 clinical trials.

Does the Number of Bifunctional Chelators Conjugated to a mAb Affect the Biological Activity of Its Radio-Labeled Counterpart? Discussion Using the Example of mAb against CD-20 Labeled with 90Y or 177Lu.

There has been considerable interest in developing a monoclonal antibody (mAb) against-CD-20 (for example, Rituximab) modified by bifunctional chelating agents (BCA) for non-Hodgkin's lymphoma radioimmunotherapy. Therefore, many researchers have modified this monoclonal antibody by attaching different BCA moieties and evaluated their biological activities in terms of in vitro study and in vivo study in healthy and tumor xenografted rodents. This mini-perspective reviews the in vitro studies, the immunoreactivity and physiological distribution studies: organ-to-blood and the tumor-to-organ ratio of conjugates with different numbers of chelators per mAb. We set up a null hypothesis that states there is no statistical significance between the biological activity of monoclonal antibody (Rituximab) and the number of conjugated bifunctional chelators. Overall, we have concluded that there is no strong evidence for this hypothesis. However, the literature data should be questioned due to the potential lack of uniform study methodology.

Design and Evaluation of 223Ra-Labeled and Anti-PSMA Targeted NaA Nanozeolites for Prostate Cancer Therapy-Part II. Toxicity, Pharmacokinetics and Biodistribution.

Metastatic castration-resistant prostate cancer (mCRPC) is a progressive and incurable disease with poor prognosis for patients. Despite introduction of novel therapies, the mortality rate remains high. An attractive alternative for extension of the life of mCRPC patients is PSMA-based targeted radioimmunotherapy. In this paper, we extended our in vitro study of 223Ra-labeled and PSMA-targeted NaA nanozeolites [223RaA-silane-PEG-D2B] by undertaking comprehensive preclinical in vitro and in vivo research. The toxicity of the new compound was evaluated in LNCaP C4-2, DU-145, RWPE-1 and HPrEC prostate cells and in BALB/c mice. The tissue distribution of 133Ba- and 223Ra-labeled conjugates was studied at different time points after injection in BALB/c and LNCaP C4-2 tumor-bearing BALB/c Nude mice. No obvious symptoms of antibody-free and antibody-functionalized nanocarriers cytotoxicity and immunotoxicity was found, while exposure to 223Ra-labeled conjugates resulted in bone marrow fibrosis, decreased the number of WBC and platelets and elevated serum concentrations of ALT and AST enzymes. Biodistribution studies revealed high accumulation of 223Ra-labeled conjugates in the liver, lungs, spleen and bone tissue. Nontargeted and PSMA-targeted radioconjugates exhibited a similar, marginal uptake in tumour lesions. In conclusion, despite the fact that NaA nanozeolites are safe carriers, the intravenous administration of NaA nanozeolite-based radioconjugates is dubious due to its high accumulation in the lungs, liver, spleen and bones.

Clickable Radiocomplexes With Trivalent Radiometals for Cancer Theranostics: In vitro and in vivo Studies.

Pre-targeting approaches based on the inverse-electron-demand Diels-Alder (iEDDA) reaction between strained trans-cyclooctenes (TCO) and electron-deficient tetrazines (Tz) have emerged in recent years as valid alternatives to classic targeted strategies to improve the diagnostic and therapeutic properties of radioactive probes. To explore these pre-targeting strategies based on in vivo click chemistry, a small family of clickable chelators was synthesized and radiolabelled with medically relevant trivalent radiometals. The structure of the clickable chelators was diversified to modulate the pharmacokinetics of the resulting [111In]In-radiocomplexes, as assessed upon injection in healthy mice. The derivative DOTA-Tz was chosen to pursue the studies upon radiolabelling with 90Y, yielding a radiocomplex with high specific activity, high radiochemical yields and suitable in vitro stability. The [90Y]Y-DOTA-Tz complex was evaluated in a prostate cancer PC3 xenograft by ex-vivo biodistribution studies and Cerenkov luminescence imaging (CLI). The results highlighted a quick elimination through the renal system and no relevant accumulation in non-target organs or non-specific tumor uptake. Furthermore, a clickable bombesin antagonist was injected in PC3 tumor-bearing mice followed by the radiocomplex [90Y]Y-DOTA-Tz, and the mice imaged by CLI at different post-injection times (p.i.). Analysis of the images 15 min and 1 h p.i. pointed out an encouraging quick tumor uptake with a fast washout, providing a preliminary proof of concept of the usefulness of the designed clickable complexes for pre-targeting strategies. To the best of our knowledge, the use of peptide antagonists for this purpose was not explored before. Further investigations are needed to optimize the pre-targeting approach based on this type of biomolecules and evaluate its eventual advantages.

PSMA-D4 Radioligand for Targeted Therapy of Prostate Cancer: Synthesis, Characteristics and Preliminary Assessment of Biological Properties.

A new PSMA ligand (PSMA-D4) containing the Glu-CO-Lys pharmacophore connected with a new linker system (L-Trp-4-Amc) and chelator DOTA was developed for radiolabeling with therapeutic radionuclides. Herein we describe the synthesis, radiolabeling, and preliminary biological evaluation of the novel PSMA-D4 ligand. Synthesized PSMA-D4 was characterized using TOF-ESI-MS, NMR, and HPLC methods. The novel compound was subject to molecular modeling with GCP-II to compare its binding mode to analogous reference compounds. The radiolabeling efficiency of PSMA-D4 with 177Lu, 90Y, 47Sc, and 225Ac was chromatographically tested. In vitro studies were carried out in PSMA-positive LNCaP tumor cells membranes. The ex vivo tissue distribution profile of the radioligands and Cerenkov luminescence imaging (CLI) was studied in LNCaP tumor-bearing mice. PSMA-D4 was synthesized in 24% yield and purity >97%. The radio complexes were obtained with high yields (>97%) and molar activity ranging from 0.11 to 17.2 GBq mcmol-1, depending on the radionuclide. In vitro assays confirmed high specific binding and affinity for all radiocomplexes. Biodistribution and imaging studies revealed high accumulation in LNCaP tumor xenografts and rapid clearance of radiocomplexes from blood and non-target tissues. These render PSMA-D4 a promising ligand for targeted therapy of prostate cancer (PCa) metastases.

PSMA targeted conjugates based on dextran.

BACKGROUND: Currently, radiotherapy is one of the most popular choices in clinical practice for the treatment of cancers. While it offers a fantastic means to selectively kill cancer cells, it can come with a host of side effects. To minimize such side effects, and maximize the therapeutic effect of the treatment, we propose the use of targeted radiopharmaceuticals. In the study presented herein, we investigate two synthetic pathways of dextran-based radiocarriers and provide their key chemical and physical properties: stability of the bonding of chelating agent and tertiary structure of obtained formulations and its influence on biological properties. Additionally, PSMA small molecule inhibitor was attached and quantified using DELFIA fluorescence assay. Finally, biological properties and radiolabeling yield were studied using confocal microscopy and ITLC-SG chromatography. RESULTS: Two types of Dex-conjugates - micelle-like nanoparticles (NPs) and non-folded conjugates - were successfully generated and shown to exhibit cellular effects. The tertiary structure of the conjugates was found to influence the selectivity of PSMA and mediate cell binding as well as cellular uptake mechanisms. NPs were shown to be internalized by other, non - PSMA mediated channels. Simultaneously, the uptake of non-folded conjugates required PSMA inhibitor to pass through cell membrane. The radiochemical yield of NHS coupled DOTA chelator was between 91.3 and 97.7% while the TCT-amine bonding showed higher stability and gave the yields of 99.8-100%. CONCLUSIONS: We obtained novel, dextran-based radioconjugates, and presented a superior method of chelator binding, resulting in exquisite radiochemical properties as well as selective cross-membrane transport.

Impact of DOTA-Chelators on the Antitumor Activity of 177Lu-DOTA-Rituximab Preparations in Lymphoma Tumor-Bearing Mice.

Background: This work aimed to evaluate the influence of two chelators: DOTA(SCN) and DOTA(NHS) on radioimmunotherapy using 177Lu-DOTA-Rituximab preparations in murine lymphoma xenograft models. Subsequently, based on animal data, the organ radiation-absorbed doses were extrapolated to humans (adult male). Materials and Methods: Therapeutic efficacy of 177Lu-DOTA-Rituximab was evaluated in male nude mice bearing either Raji (B lymphocyte, CD20+) and Jurkat (T lymphocyte, CD20) xenografts, utilizing an anti-CD20 antibody-Rituximab conjugate with either DOTA(SCN) or DOTA(NHS). The DOTA-Rituximab conjugates were prepared in the form of freeze-dried kits. Results: All radioimmunoconjugates were obtained with high radiolabeling yield (radiochemical purity, RCP > 95%) and specific activity of ca. 0.5 GBq/mg. Therapeutic effects of 177Lu-DOTA-Rituximab were observed in animals regardless whether DOTA(SCN) or DOTA(NHS) were used for conjugation. Importantly, therapy involving 177Lu-DOTA-Rituximab was more effective than use of Rituximab alone. Conclusions: The degree of antitumor efficacy was dependent on the type of applied bifunctional chelators conjugated to mAb. However, this difference was not statistically significant. Dosimetry calculations showed that the absorbed radiation doses extrapolated to humans were very low for osteogenic cells regardless of the conjugates. Organs like the liver and spleen, treated with 177Lu-DOTA(SCN)-Rituximab, showed similar radiation absorbed doses when compared with 177Lu-DOTA(NHS)-Rituximab.

Influence of DOTA Chelators on Radiochemical Purity and Biodistribution of 177Lu- and 90Y-Rituximab in Xenografted Mice.

This work presents a comparative biological evaluation of 90Y- and 177Lu- labelled DOTA-SCN and DOTA-NHS conjugated to Rituximab in tumour-bearing mice. Two DOTA derivatives, p-SCN-Bn-DOTA and DOTA-NHS-ester were conjugated to Rituximab and then freeze-dried kit formulations were prepared, as previously described (1). Tissue distribution was investigated in tumour-bearing (Raji s.c.) male Rj: NMRI-Foxn1nu/Foxn1nu mice at different time points after administration of 177Lu-DOTA-Rituximab or 90Y-DOTA-Rituximab (6 MBq/10 µg per mouse). In addition, tumour images were acquired with a PhotonIMAGERTM after injection of 90Y-DOTA (SCN)-Rituximab. All radioimmunoconjugates were obtained with high radiolabelling yield (RCP > 98%) and specific activity of ca. 0.6 GBq/mg. The conjugates were stable in human serum and in 0.9% NaCl; however, progressive aggregation was observed with time, in particular for DOTA -(SCN) conjugates. Both 177Lu- and 90Y-DOTA -(SCN)-Rituximab revealed slow blood clearance. The maximum tumour uptake was found 72 h after injection of 177Lu-DOTA -(SCN)-Rituximab (9.3 ID/g). A high radioactivity uptake was observed in liver and spleen, confirming the hepatobiliary excretion route. The results obtained by the radioactive optical imaging harmonize with those from the biodistribution study.

The Effects of Isopropyl Methylphosphono-Fluoridate (IMPF) Poisoning on Tumor Growth and Angiogenesis in BALB/C Mice.

BACKGROUND Acetylcholinesterase (AChE) and cholinergic receptors have an important role in the immune system and angiogenesis. This work evaluated the effects of isopropyl methylphosphonofluoridate (IMPF), an irreversible inhibitor of AChE, on tumor growth and selected parameters associated with tumor angiogenesis. MATERIAL AND METHODS Experiments were performed on male BALB/c mice exposed to IMPF (study group) or saline buffer (control group) and inoculated with L-1 sarcoma; the number of new blood vessels (TIA test) and the level of αvß3 integrin (131I-MAb-antiß3 assay) were analyzed at seven, 14, or 21 days after implantation of the tumor cells. RESULTS The IMPF poisoning affected tumor angiogenesis (TIA test). There was a statistically significant increase in the number of newly forming blood vessels in the group subjected to IMPF and inoculated with tumor cells. CONCLUSIONS This study showed that IMPF had a significant effect on the regulation of lymphocyte-induced angiogenesis and the modulation of angiogenic and pro-inflammatory cytokines secretion. The observed effects suggest involvement of neuronal and/or non-neuronal cholinergic signaling pathway.

Oxidation of methionine - is it limiting the diagnostic properties of 99mTc-labeled Exendin-4, a Glucagon-Like Peptide-1 receptor agonist?

BACKGROUND: Preliminary clinical evaluation of 99mTc-EDDA/HYNIC-Met14-Exendin-4 showed that the complex offers new diagnostic possibilities for insulinoma and MTC. Exendin-4 contains methionine at position 14 in the amino acid chain, which may be oxidized to methionine sulfoxide and, from the pharmaceutical point of view, the oxidized moiety becomes an undesired impurity in the final radioactive preparation. Therefore, the aim of this study was to investigate the influence of commonly used methods to eliminate the effect of methionine oxidation in peptides, i.e. the replacement of methionine by norleucine (Nle) and the addition of L-methionine, on the in vitro stability and the biodistribution. MATERIAL AND METHODS: 99mTc-EDDA/HYNIC-Met14-Exendin-4, 99mTc-EDDA/HYNIC-Nle14-Exendin-4, 99mTc-EDDA/HYNIC-Met14-Ex-endin-4 with the addition of L-methionine and an oxidized form of Exendin-4, i.e. 99mTc-EDDA/HYNIC-Met14(ox)-Exendin-4 were compared in vivo with 68Ga-NODAGA-Nle14-Exendin-4 in normal Wistar rats. The stability and lipophilicity were determined in vitro. RESULTS: Biodistribution studies confirmed the specific uptake of all tested complexes in the GLP-1 positive organs: lungs, pancreas and stomach. The uptake of 99mTc-EDDA/HYNIC-Met14-Exendin-4 with the addition of L-methionine and for 68Ga-NODAGA-Nle14-Exendin-4 at 1h p.i. was around 2-fold higher than that of 99mTc-EDDA/HYNIC-Met14-Exendin-4 and 99mTc-EDDA/HYNIC-Nle14-Exendin-4. CONCLUSION: Although the substitution of methionine by norleucine in the HYNIC-Exendin-4 did not result in improved bio-distribution, the use of L-methionine, as the excipient that inhibits the oxidation of methionine in the peptide chain resulted in higher lung/blood and stomach/blood uptake ratios. Our results confirmed that methionine at position 14 of amino acid chain of Exendin-4 plays an important role in the interaction with GLP-1 receptor positive tissue.

Standardization of Procedures for the Preparation of (177)Lu- and (90)Y-labeled DOTA-Rituximab Based on the Freeze-dried Kit Formulation.

Rituximab when radiolabelled with (177)Lu or (90)Y has been investigated for the treatment of patients with Non-Hodgkin's Lymphoma. In this study, we optimized the preparation of antibody conjugates with chelating agent in the freeze-dried kit. It shortens procedures needed for the successful radiolabeling with lutetium-177 and yttrium-90 and assures reproducible labelling yields. Various molar ratios of Rituximab:DOTA (from 1:5 to 1:100) were used at the conjugation step and different purification method to remove unbound DOTA were investigated (size-exclusion chromatography, dialysis, ultrafiltration). The final monoclonal antibody concentration was quantified by Bradford method, and the number of DOTA molecules was determined by radiolabeling assay using (64)Cu. The specific activity of (177)Lu-DOTA-Rituximab and (90)Y-DOTA-Rituximab were optimized using various amounts of radiometal. Quality control (SE-HPLC, ITLC) and stability study were performed. An average of 4.2 ± 0.8 p-SCN-Bz-DOTA molecules could be randomly conjugated to a single molecule of Rituximab. The ultrafiltration system was the most efficient for purification and resulted in the highest recovery efficiency (77.2%). At optimized conditions the (177)Lu-DOTARituximab and (90)Y-DOTA-Rituximab were obtained with radiochemical purity >99% and specific activity ca. 600 MBq/mg. The radioimmunoconjugates were stable in human serum and 0.9% NaCl. After 72 h of incubation the radiochemical purity of (177)Lu-DOTA-Rituximab decreased to 94% but it was still more than 88% for (90)Y-DOTA-Rituximab. The radioimmunoconjugate showed stability after six months storage at 2 - 8(0)C, as a lyophilized formulation. Our study shows that Rituximab-DOTA can be efficiently radiolabeled with (177)Lu and (90)Y via p-SCN-Bn-DOTA using a freezedried kit.

Comparative study on DOTA-derivatized bombesin analog labeled with 90Y and 177Lu: in vitro and in vivo evaluation.

INTRODUCTION: The aim of the study was to compare in vitro and in vivo a novel DOTA-chelated bombesin (BN) analog of the amino acid sequence, QRLGNQWAVGHLM-CONH(2) (BN[2-14]NH(2)), labeled with (90)Y and (177)Lu, for its potential use in targeted radiotherapy of tumors expressing gastrin releasing peptide (GRP) receptors. The same amino acid sequence, but with different chelator, referred as BN1.1 (Gly-Gly-Cys-Aca-QRLGNQWAVGHLM-CONH(2)), has already been studied and reported; however, the DOTA-chelated one, suitable for labeling with M(+3) type radiometals, was not yet described. METHODS: The conditions for labeling of DOTA-BN[2-14]NH(2) with noncarrier added (90)Y and with (177)Lu [specific activity (SA), 15 Ci/mg Lu] were investigated and optimized to provide (90)Y-DOTA-BN[2-14]NH(2) and (177)Lu-DOTA-BN[2-14]NH(2) of high SA. The stability of the radiolabeled compounds in human serum was evaluated over a period of 24 h. The human prostate cancer cell line PC-3, known to express GRP receptors, was used for in vitro evaluation of radiolabeled peptide affinity to GRP receptors and for assessment of cytotoxicity of both nonlabeled and radiolabeled peptide. Biodistribution accompanied by receptor blocking was studied in normal Swiss mice. RESULTS: (90)Y-DOTA-BN[2-14]NH(2) and (177)Lu-DOTA-BN[2-14]NH(2) were obtained with radiochemical yield >98% and high SA (67.3 GBq (90)Y/mumol and 33.6 GBq (177)Lu/mumol, respectively). They were stable when incubated in human serum for up to 24 h. The binding affinities of DOTA-BN[2-14]NH(2) and both (nat)Y- and (nat)Lu-labeled analogs to GRP receptors were high (IC(50)=1.78, 1.99, and 1.34 nM, respectively), especially for the (nat)Lu-DOTA-BN[2-14]NH(2) complex. The cytotoxicity study of DOTA-BN[2-14]NH(2) to PC-3 cells revealed an IC(50)=6300 nM after 72 h of exposition, while the labeled derivatives showed no significant cytotoxic effect. The internalization rate to PC-3 cells was more rapid for (177)Lu-labeled peptide (84.87%) than for the (90)Y-labeled one (80.79%), while the efflux rate was slower for (177)Lu-DOTA-BN[2-14]NH(2) (46.8% vs. 61.74%). The biodistribution study of both derivatives in normal mice revealed a specific binding to GRP receptor-positive tissues, which could be blocked by coinjection of cold peptide. The effect of receptor blockage in vivo was also more pronounced for the (177)Lu-labeled peptide than that for the (90)Y-labeled (81% vs. 42%, respectively). CONCLUSIONS: Our studies demonstrated that DOTA-BN[2-14]NH(2) can be labeled with (90)Y (NCA) and (177)Lu (CA) with high radiochemical yields. The in vitro and in vivo comparison between (90)Y-DOTA-BN[2-14]NH(2) and (177)Lu-DOTA-BN[2-14]NH(2) indicated that the change of radiometal in the complex from Y to Lu influence the binding affinity to the GRP receptors with preference to the (177)Lu-labeled derivative.

Antitumor activity of platinum(II) complexes with histamine and radioiodinated histamine in a transplantable murine adenocarcinoma model.

PURPOSE: Antitumor activity of the dichloroplatinum(II)-histamine complexes labeled with I-125 or I-131 was investigated in a transplantable murine adenocarcinoma (MA) model. METHODS: The tumor model was obtained in C3H/W female mice after subcutaneous inoculation of the tumor cells derived from the mice bearing a mammary tumor of spontaneous origin. Antitumor activities of the platinum-histamine complexes were investigated in three independent experiments, which differed in applied doses of preparations (PtCl(2)Hist, PtCl(2)[(125)I]Hist, PtCl(2)[(131)I]Hist, PtCl(2)Hist/PtCl(2)[(125)I]Hist and PtCl(2)Hist/PtCl(2)[(131)I]Hist), treatment schedules as well as stages of the disease progress in the animals used. Experiment 1 included long-term, multidose treatment with low single doses (treatment duration 31-32 days; 8-10 doses of ca. 0.25.MTD(Pt) each). Experiment 2 included short-term, multidose treatment with higher single doses (4 x ca. 0.5.MTD(Pt) up to Day 13 of the treatment). Experiment 3 included long-term concomitant multidose treatment with higher single doses (9x0.9-0.4.MTD(Pt) up to Day 33). RESULTS: The long-term treatment with the platinum-histamine preparations revealed inhibiting activity on the tumor growth and size in comparison to control groups. The most intensive and significant antitumor effects were observed for the radioactive complexes. The tumor growth delay factors (GDFs) observed in Experiment 1 were 0.4, 0.7, and 1.2 for PtCl(2)Hist, PtCl(2)Hist/PtCl(2)[(131)I]Hist, and PtCl(2)Hist/PtCl(2)[(125)I]Hist, respectively. Significant (P<.05) prolongations of median survivals (MS) were found in Experiment 2 following the treatment with higher single doses of PtCl(2)Hist and PtCl(2)His/PtCl(2)[(125)I]Hist (Ratio MS(tr)/MS(con) ca. 1.4). A slightly less potent activity was observed for PtCl(2)Hist/PtCl(2)[(131)I]Hist, and no survival improvement was found for the groups treated mostly with the radiation (PtCl(2)[(125)I]Hist and PtCl(2)[(131)I]Hist). The intensive and long-term concomitant scheduling of the radioactive platinum-histamine complexes labeled with I-125 and I-131 (Experiment 3) resulted in a significant inhibition of the tumor growth (GDF=1.9) and survival prolongation of the tumor-bearing mice (MS(tr)/MS(con)=1.5, P=.023). The treatment-related toxicity was mild. CONCLUSION: An enhancement of the antitumor activity due to the multidose concomitant treatment with a combination of cytotoxic/cytostatic dichloroplatinum(II)-histamine and the attached iodine radionuclides was shown in the murine model of experimental neoplasm.

Uptake of radiolabelled modified fragment of human alfa-fetoptrotein by experimental mammary adenocarcinoma: in vitro and in vivo studies.

BACKGROUND: The aim of the study was to examine in vitro and in vivo binding of radiolabelled analogues of P149 peptide by experimental mammary adenocarcinoma with the intention of potential application for diagnosis and internal radiotherapy of tumours. MATERIAL AND METHODS: The 36-amino acid peptide (P149-QY) of 90% homology to 447-480 peptide fragment of hAFP was synthesised and radiolabelled with iodine-125. The biodistribution of P149-Q[125I]-Y was studied in experimental mammary tumours. For in vitro experiments, extract from mouse mammary tumours were prepared and incubated with radioiodinated P149-QY peptide in the presence of a cross-linking reagent. RESULTS: The gel electrophoresis analysis (SDS-PAGE) showed that radioiodinated P149-QY peptide formed a complex with adenocarcinoma proteins of about 30 kDa. The biodistribution of P149-Q[125I]-Y studied in experimental mammary tumours revealed a higher pharmacokinetic rate in comparison with the whole radioiodinated AFP molecule. A moderate uptake of P149-Q[125I]-Y in the tumour tissue was observed (3.2% ID/g at 30-min p.i.v). However, a faster radioactivity clearance from blood and normal tissues resulted in an increase in the tumour/muscle (T/M) ratio, i.e. from 2.3 to 3.4 after 30 mins and 24 h p.i.v, respectively. CONCLUSIONS: The present study shows that radioiodinated P149-QY peptide reveals some positive features as the AFP receptor radioligand, however, some additional structural modifications of the initial peptide molecule are necessary for full retention of the ligand-receptor interaction of its radiolabelled forms.