Radiolabelled Iododeoxyuridine for Experimental Targeted Radiotherapy of Glioma

Gliomas are the most common primary tumours arising in the human brain. The most malignant glioma, the glioblastoma, represents 5000 new cases per year in the United States. Despite surgery, chemotherapy, and radiotherapy, glioblastomas are almost always fatal, with a median survival of less than a year and a 5-year survival rate of 5.5% or less. After treatment, recurrent disease often occurs locally; systemic metastases are rare. Neurologic dysfunction and death are from local growth. No therapeutic modality has substantially changed the outcome of patients with glioblastoma. Therefore, we have explored a novel form of treatment: targeted radiotherapy using radioiododeoxyuridine, a thymidine analogue that is intended to destroy glioma cells yet spare normal brain tissue. Radiolabelled IUdR is an appropriate targeting vehicle for the delivery of radiation to proliferating tumour target tissue. This study included an investigation of the most suitable radioisotopes to conjugate to IUdR. Heterogeneous proliferative activity of glioma cells (ie non-cycling cells) is one of the main barriers to the therapeutic potential of radiolabelled IUdR. Therefore, an important part of this work was obtaining appropriate models for the study of human gliomas in vitro. We thus employed spheroids derived from UVW, SB 18 and U251 glioma cell lines, as well as cells in exponential monolayer growth and plateau phase for this evaluation. Multicellular spheroids grown from established cell lines have been shown to have growth kinetics similar to in vivo tumours. As with the clinical situation, in the spheroid model there is an increase in the number of resting cells as the size of the mass enlarges and also there are nonproliferating cells and necrosis in the more central hypoxic area. The UVW cell line was chosen because of its capability to grow as very large and regularly shaped spheroids. The karyotype anlaysis of UVW cell line revealed a highly aneuploid cell line. This cell line was also very radioresistant in both monolayer and spheroid cultures as determined by external beam radiation experiments. The survival fraction values obtained at 2 Gy (SF2) were 0.55 for exponential monolayer cells and 0.83-0.93 for spheroids gained from clonogenic assay and growth delay experiments respectively. These values place this cell line at the radioresistant part of the spectrum of human cell line radiosensitivity. We assessed the effect of proliferative heterogeneity on the uptake of non-radiolabelled IUdR by studying different sizes of UVW human glioma spheroids and monolayer cell cultures in exponential and plateau phases, in conjunction with flow cytometry. The results of the study confirm that there is an inverse relationship between the proportion of cycling cells and spheroid diameter. In monolayer cultures more than 95% of exponentially growing cells and 62% of plateau phase cells were labelled with IUdR after one doubling time. However, the labelling index in the small spheroids (100-200mum) was approximately 76% and 28% for large spheroids (700-1000mum) after one volume doubling time incubation (52 hours). The proportion of cells that incorporate IUdR is small and large sizes of spheroids increased with increasing the period of incubation with IUdR from one to four volume doubling times. The effect of spheroid size and incubation time on labelling index was also evaluated in conjunction with autoradiography and Ki67 immunostaining. In these experiments nuclear incorporation of [125I]IUdR decreased markedly with increasing size of spheroid. The distribution of IUdR was uniform throughout small spheroids (<200mum), while the concentration of IUdR occured predominantly in the peripheral cells of larger spheroids. Radiopharmaceutical uptake corresponded closely to the regions of cell cycling as indicated by staining for the nuclear antigen Ki67. The IUdR uptake enhancement occurred by increasing the incubation time from 52 hours to 104 hours. It was concluded that a single injection of radioiodinated IUdR would be insufficient to sterillise all of the malignant cells. Therefore, to achieve maximal therapeutic benefit IUdR should be administered either by multiple injections or by slow release from polymers or slow-pump delivery

Evaluation of The Combined Effects of Hyperthermia, Cobalt-60 Gamma Rays and IUdR on Cultured Glioblastoma Spheroid Cells and Dosimetry Using TLD-100

Objective: In radiation treatment, the irradiation which is effective enough to control the tumors far exceeds normal-tissues tolerance. Thus to avoid such unfavourable outcomes, some methods sensitizing the tumor cells to radiation are used. Iododeoxyuridine (IUdR) is a halogenated thymidine analogue that known to be effective as a radiosensitizer in human cancer therapy. Improving the potential efficacy of radiation therapy after combining to hyperthermia depends on the magnitude of the differential sensitization of the hyperthermic effects or on the differential cytotoxicity of the radiation effects on the tumor cells. In this study, we evaluated the combined effects of IUdR, hyperthermia and gamma rays of 60Co on human glioblastoma spheroids culture. Materials and Methods: In this experimental study,the cultured spheroids with 100μm diameter were treated by 1 μM IUdR, 43˚C hyperthermia for an hour and 2 Gy gamma rays, respectively. The DNA damages induced in cells were compared using alkaline comet assay method, and dosimetry was then performed by TLD-100. Comet scores were calculated as mean ± standard error of mean (SEM) using one-way ANOVA. Results:Comparison of DNA damages induced by IUdR and hyperthermia + gamma treatment showed 2.67- and 1.92-fold enhancement, respectively, as compared to the damages induced by radiation alone or radiation combined IUdR. Dosimetry results showed the accurate dose delivered to cells. Conclusion: Analysis of the comet tail moments of spheroids showed that the radiation treatments combined with hyperthermia and IUdR caused significant radiosensitization when compared to related results of irradiation alone or of irradiation with IUdR. These results suggest a potential clinical advantage of combining radiation with hyperthermia and indicate effectiveness of hyperthermia treatment in inducing cytotoxicity of tumor cells

Cytogenetic Damages from Iododeoxyuridine -induced Radiosensitivity with and without Methoxyamine in Human Glioblastoma Spheroids

Objective: Iododeoxyuridine-induced Radiosensitivityi (IUdR) is ahalogenated thymidine analogue recognized to be effective in vitro andin vivo radiosensitizer in human cancers. It is reported that Methoxyamine (MX)potentiates DNA damages in cancer cells with blocking the repair pathway ofIUdR damages. But studies, entirely, are restricted on monolayer culture cellsfrom human colon cancer cells. Spheroids are 3D form of cells that aggregateand grow together which resemble in vivo tumor models in several aspects andthe the results of such studies can be extended to tumor in vivo. The aim of thecurrent study was to evaluate DNA damages from IUdR and gamma rays withand without Methoxyamine in human Glioblastoma spheroids.Materials and Methods: The DNA induced damages in U87MG cell line werecompared using alkaline comet assay method. Experiments were performedwith two different sizes of spheroids (100μm and 300μm).Results: Evaluation of the effects of IUdR with and without MX pretreatmenton spheroids following ionizing radiation showed that MX increased the celldamages of IUdR with and without irradiation in both diameters spheroids. Thedamages were further increased in 100μm compared with 300μm diameter.Conclusion: Comparisons of tail moments in spheroids with 100 and 300μmdiameter showed that cell damages in larger spheroids, 300μm, are lesserthan smaller one, 100μm. This could be due to existence of G0 cells and cellswith longer cycle which IUdR was less incorporated into them. Thus, decreasein IUdR radiosensitization and base wxcision repair (BER), results in reductionof MX activities. Using agents for Inhibiting the activities of proteins whichare responsible for carrying the cells to G0 may be beneficial in solving suchproblems

Relative Biological Effectiveness (RBE) of 131I Radiation Relative to 60Co Gamma Rays

Objective: To assess relative biological effectiveness (RBE) of 131I radiation relative to 60Co gamma rays in glioblastoma spheroid cells.Materials and Methods: In this experimental study, glioblastoma spheroid cells were exposed to 131I radiation and 60Co gamma rays. Radiation induced DNA damage was evaluated by alkaline comet assay. Samples of spheroid cells were treated by radiation from 131I for four different periods of time to find the dose-response equation. Spheroid cells were also exposed by 200 cGy of 60Co gamma rays as reference radiation to induce DNA damage as endpoint.Results: Resulted RBE of 131I radiation relative to 60Co gamma rays in 100 μm giloblastoma spheroid cells was equal to 1.16.Conclusion: The finding of this study suggests that 131I photons and electrons can be more effective than 60Co gamma rays to produce DNA damage in glioblastoma spheroid cells

Evaluation of the Combined Effect of 2ME2 and Co on the Inducement of DNA Damage by IUdR in a Spheroid Model of the U87MG Glioblastoma Cancer Cell Line Using Alkaline Comet Assay

Objective: In this study, we investigated the combined effect of 2-Methoxyestradiol (2ME2)and 60Co on the cytogenetic damage of iododeoxyuridine (IUdR) in the spheroid model ofU87MG glioblastoma cancer cell lines by alkaline comet assay.Materials and Methods: U87MG cells were cultured as spheroids with diameters of 350μm. As control, the spheroids of one plate were not treated. Other cultures were pretreatedwith 2ME2 (250 μM) for one volume doubling time (1 VDT). After this time, the subsequenttreatments were performed according to the following groups:1. Vehicle (this sample was not treated in the 2nd VDT)2. Treated with 2ME2 (250 μM) for 1 VDT3. Treated simultaneously with 2ME2 (250 μM) and IUdR (1 μM) for 1 VDT4. Treated with 2ME2 (250 μM) for 1 VDT then irradiated with 60Co (2 Gy)5. Treated simultaneously with 2ME2 (250 μM) and IUdR (1 μM) for 1 VDT then irradiatedwith 60Co (2 Gy)Then the DNA damage was evaluated using the alkaline comet assay method.Results: The results showed that 2ME2 in combination with gamma irradiation of 60Cosignificantly (p<0.001) increased the DNA damage by IUdR as compared to the controlgroup. Thus the combination of these two agents increased the cytogenetic effects ofIUdR in the spheroid culture model of U87MG glioblastoma cell lines.Conclusion: By inhibiting the HIF-1α protein and preventing the G0 phase arrest, 2ME2causes an increased progression into S phase and increases the IUdR absorption. Thenthe DNA damage in the spheroid cells increases as the uptake of IUdR is increased.These results suggest that the combined use of 2ME2 and 60Co can increase the radiosensitizationeffect of IUdR

An Update on the Role of mpMRI and ⁶⁸Ga-PSMA PET Imaging in Primary and Recurrent Prostate Cancer

The objective of this work was to review comparisons of the efficacy of 68Ga-PSMA-11 (prostate-specific membrane antigen) PET/CT and multiparametric magnetic resonance imaging (mpMRI) in the detection of prostate cancer among patients undergoing initial staging prior to radical prostatectomy or experiencing recurrent prostate cancer, based on histopathological data. A comprehensive search was conducted in PubMed and Web of Science, and relevant articles were analyzed with various parameters, including year of publication, study design, patient count, age, PSA (prostate-specific antigen) value, Gleason score, standardized uptake value (SUVmax), detection rate, treatment history, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and PI-RADS (prostate imaging reporting and data system) scores. Only studies directly comparing PSMA-PET and mpMRI were considered, while those examining combined accuracy or focusing on either modality alone were excluded. In total, 24 studies comprising 1717 patients were analyzed, with the most common indication for screening being staging, followed by relapse. The findings indicated that 68Ga-PSMA-PET/CT effectively diagnosed prostate cancer in patients with suspected or confirmed disease, and both methods exhibited comparable efficacy in identifying lesion-specific information. However, notable heterogeneity was observed, highlighting the necessity for standardization of imaging and histopathology systems to mitigate inter-study variability. Future research should prioritize evaluating the combined diagnostic performance of both modalities to enhance sensitivity and reduce unnecessary biopsies. Overall, the utilization of PSMA-PET and mpMRI in combination holds substantial potential for significantly advancing the diagnosis and management of prostate cancer.</p

An Update on the Role of mpMRI and 68Ga-PSMA PET Imaging in Primary and Recurrent Prostate Cancer

The objective of this work was to review comparisons of the efficacy of 68Ga-PSMA-11 (prostate-specific membrane antigen) PET/CT and multiparametric magnetic resonance imaging (mpMRI) in the detection of prostate cancer among patients undergoing initial staging prior to radical prostatectomy or experiencing recurrent prostate cancer, based on histopathological data. A comprehensive search was conducted in PubMed and Web of Science, and relevant articles were analyzed with various parameters, including year of publication, study design, patient count, age, PSA (prostate-specific antigen) value, Gleason score, standardized uptake value (SUVmax), detection rate, treatment history, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and PI-RADS (prostate imaging reporting and data system) scores. Only studies directly comparing PSMA-PET and mpMRI were considered, while those examining combined accuracy or focusing on either modality alone were excluded. In total, 24 studies comprising 1717 patients were analyzed, with the most common indication for screening being staging, followed by relapse. The findings indicated that 68Ga-PSMA-PET/CT effectively diagnosed prostate cancer in patients with suspected or confirmed disease, and both methods exhibited comparable efficacy in identifying lesion-specific information. However, notable heterogeneity was observed, highlighting the necessity for standardization of imaging and histopathology systems to mitigate inter-study variability. Future research should prioritize evaluating the combined diagnostic performance of both modalities to enhance sensitivity and reduce unnecessary biopsies. Overall, the utilization of PSMA-PET and mpMRI in combination holds substantial potential for significantly advancing the diagnosis and management of prostate cancer