Rapid and specific targeting of 125I-labeled B lymphocyte stimulator to lymphoid tissues and B cell tumors in mice.

B lymphocyte stimulator (BLyS) protein is a member of the tumor necrosis factor (TNF) superfamily of cytokines that binds to B lineage cells, but not T cells, monocytes, natural killer cells, or granulocytes. BLyS protein binding to B cells is restricted to immunoglobulin-positive cells and is not evident on pro- or pre-B cell populations. This unique binding profile suggests that a radiolabeled form of BLyS protein may be a useful treatment for B cell neoplasias such as B cell lymphoma and multiple myeloma. Here, we report the biodistribution of radiolabeled recombinant human BLyS after intravenous injection into normal mice and mice bearing BCL1 tumor in the spleen or J558 tumor in the subcutaneous space. We also report the use of these data to estimate human dosimetry. METHODS: (125)I-Labeled BLyS protein (50 micro g/kg, 0.185-0.37 MBq per mouse) was injected intravenously into BALB/c mice, and biodistribution was measured by direct counting of radioactivity in dissected tissues and by quantitative whole-body autoradiography (QWBA). RESULTS: The half-life of radiolabeled BLyS protein in blood was approximately 2.7 h in both normal and tumor-bearing mice. The spleen showed the highest uptake of BLyS protein in both normal and tumor-bearing mice, with a maximum concentration (C(max)) of 35-45 percentage injected dose per gram (%ID/g) occurring between 1 and 3 h after injection. In lymph nodes, C(max) was approximately 20 %ID/g in normal and J558 tumor-bearing mice and 8-15 %ID/g in BCL1 tumor-bearing mice. Limited biodistribution data from the J558 tumors showed a C(max) of approximately 15 %ID/g. By contrast, C(max) was only approximately 5 %ID/g for both kidney and liver. QWBA confirmed high radioactivity in spleen, lymph nodes, and stomach contents and low radioactivity in kidney and liver. After 24 h, spleen and lymph nodes were still positive in QWBA images, whereas liver and kidney no longer had observable levels. CONCLUSION: Radiolabeled BLyS showed specific and rapid targeting to lymphoid tissues and B cell tumors in mice. Unlike monoclonal antibodies, which have long plasma half-lives and considerable liver uptake, BLyS has distinct pharmacokinetic and biodistribution properties that may offer advantages compared with antibody-based radioimmunotherapy.     

Comparison of gallium-67 versus indium-111 monoclonal antibody (96.5, ZME-018) in detection of human melanoma in athymic mice

We compared the biodistribution of two radiolabeled, whole, tumor selective monoclonal antibodies [( 111In]96.5, [111In]ZME-018) to 67Ga in nude mice bearing a human melanoma known to express p97 antigen. Localization of gallium was determined 48 hr following i.v. injection. Localization of the radiolabeled antibodies was determined at 3 days and 7 days following i.v. injection. All agents showed more or less similar absolute tumor uptake which varied between 22% and 36% of the injected dose per gram of tumor. Only the tumor uptake of [111In]96.5 antibody at 7 days was significantly lower than the 67Ga uptake at 48 hr. However, uptake in normal tissues was generally higher for both antibodies at 3 and 7 days than for 67Ga uptake at 48 hr. Therefore, the tumor-to-blood ratio for 67Ga was tenfold higher than that for either antibody, the tumor-to-muscle ratio was twofold higher. Bone was the only organ in which the tumor-to-organ ratio was consistently higher with radiolabeled antibody than with 67Ga. The tumor-to-liver and tumor-to-intestine ratios were comparable. Localization of the two tumor selective antibodies was greater than a nonspecific "control antibody" [( 111In]CEA) and change in specific activity from 0.17 mCi/mg to 3.3 mCi/mg did not influence localization. From these animal data it may be anticipated that tumor imaging with [111In]96.5 or [111In]ZME-018 will not be superior to imaging with 67Ga for detection of melanoma.     

Phase I trial of the positron-emitting Arg-Gly-Asp (RGD) peptide radioligand 18F-AH111585 in breast cancer patients.

The integrin alpha v beta3 receptor is upregulated on tumor cells and endothelium and plays important roles in angiogenesis and metastasis. Arg-Gly-Asp (RGD) peptide ligands have high affinity for these integrins and can be radiolabeled for PET imaging of angiogenesis or tumor development. We have assessed the safety, stability, and tumor distribution kinetics of a novel radiolabeled RGD-based integrin peptide-polymer conjugate, 18F-AH111585, and its feasibility to detect tumors in metastatic breast cancer patients using PET. METHODS: The biodistribution of 18F-AH111585 was assessed in 18 tumor lesions from 7 patients with metastatic breast cancer by PET, and the PET data were compared with CT results. The metabolic stability of 18F-AH111585 was assessed by chromatography of plasma samples. Regions of interest (ROIs) defined over tumor and normal tissues of the PET images were used to determine the kinetics of radioligand binding in tissues. RESULTS: The radiopharmaceutical and PET procedures were well tolerated in all patients. All 18 tumors detected by CT were visible on the 18F-AH111585 PET images, either as distinct increases in uptake compared with the surrounding normal tissue or, in the case of liver metastases, as regions of deficit uptake because of the high background activity in normal liver tissue. 18F-AH111585 was either homogeneously distributed in the tumors or appeared within the tumor rim, consistent with the pattern of viable peripheral tumor and central necrosis often seen in association with angiogenesis. Increased uptake compared with background (P = 0.002) was demonstrated in metastases in lung, pleura, bone, lymph node, and primary tumor. CONCLUSION: 18F-AH111585 designed to bind the alpha v beta3 integrin is safe, metabolically stable, and retained in tumor tissues and detects breast cancer lesions by PET in most anatomic sites.     

Immunoreactivity and biodistribution of indium-111-labeled monoclonal antibody to a human high molecular weight-melanoma associated antigen

The anti-human, high molecular weight-melanoma associated antigen (HMW-MAA) MoAb 225.28S was chelated with 111In and then tested for its in vitro reactivity with cultured human melanoma cells and for its biodistribution in human melanoma bearing nude mice. In vitro studies showed that the radiolabeled antibody reacted specifically with cultured melanoma cells. However, binding of DTPA to the monoclonal antibody reduced its titer with cultured melanoma cells from 1:1024 to 1:512. Further labeling of the DTPA-antibody conjugate with 111In caused an additional reduction of its titer to 1:128. Injection of the radiolabeled monoclonal antibody into nude mice resulted in the accumulation of significantly (p less than 0.001) higher radioactivity in melanoma tissue than in nude mice injected with either [111In] chloride or 111In-labeled antibody to human acid phosphatase. The specificity of the distribution of the radiolabeled antibody in nude mice also was indicated by its poor localization in lesions other than melanoma (e.g., human prostate carcinoma and chronic abscess). The localization of antibody in liver and kidney was also high, although lower than that achieved in tumor. These results indicate that 111In-labeled monoclonal antibodies to human tumor associated antigens may be useful for localizing malignant lesions. However, there is a need to improve labeling and/or purification of antibody in order to decrease renal and hepatic activity.     

Kinetics and biodistribution in relation to tumour detection with 111In-labelled OV-TL 3 F(ab')2 in patients with ovarian cancer

The biological behaviour of 111In-labelled OV-TL 3 F(ab')2 was studied in 22 patients with suspected ovarian cancer. After i.v. injection with 140 MBq 111In-OV-TL 3 F(ab')2 (1 mg) blood samples were taken up to 96 h and urine and faeces were collected throughout the whole study. At surgery, 5 to 7 days post-injection, primary and metastatic tumour tissues, as well as fragments of several normal tissues, were removed and 111In uptake was measured. Blood activity disappeared with half-life values of 6.1 +/- 1.1 and 17.9 +/- 6.5 h. Within 96 h excretion in urine and faeces was 16.1 +/- 2.0% i.d. (mean +/- S.D.) and 3.1 +/- 1.9% i.d., respectively. Mean tissue uptake, expressed as % i.d. kg-1 was 3.9 +/- 1.0 for primary tumour, 11.5 +/- 5.0 for liver and 0.4 +/- 0.1 for several normal background tissues. Higher tumour uptake correlated with a higher detection rate at immunoscintigraphy. However, no strict correlation was found between the amount of tumour uptake and the expression of the monoclonal antibody defined OA3 antigen. Quantitation of organ activity, using region of interest analysis, resulted in mean peak organ activities for the liver of 16% i.d., spleen 9% i.d. and kidney 4% i.d. Distribution data indicate that besides specific antibody-antigen interaction several other mechanisms play a role in uptake in tumour and other tissues.     

Preparation and biodistribution in mice of a new radiopharmaceutical-technetium-99m labeled methotrexate, as a tumor diagnostic agent

Our aim was to develop the procedure for radiolabeling of an anticancer drug e.g., methotrexate with (99m)Tc for tumors diagnosis. The study included the radiolabeling of methotrexate, in vitro stability of radiolabeled drug, in vitro binding of radiolabeled drug with plasma protein, partition coefficient and biodistribution of radiolabeled drug in mice. Results showed 98.2±0.5% radiolabeling of methotrexate with technetium-99m ((99m)Tc). In vitro stability was studied for 5h and 79.3±5% of the drug was bound with plasma proteins. Partition coefficient of the labeled drug showed that it was highly hydrophilic. Biodistribution study in tumor bearing mice exhibited high uptake in tumor cells which were further investigated by histopathological studies. In conclusion, our study indicates that technetium-99m labeled methotrexate is a potentially strong tumor diagnostic agent with low uptake in normal tissues.     

Comparison of In-111 granulocytes and Tc-99m albumin colloid for bone marrow scintigraphy by the use of quantitative SPECT imaging

A comparison of In-111 oxinate labeled autologous granulocytes and Tc-99m albumin colloid for bone marrow scintigraphy is reported. The aim of this report was to determine if the intense uptake in the liver and spleen with nano-sized colloids, which hampers the evaluation of the skeletal parts surrounding the liver, is reduced by the use of radiolabeled granulocytes. This study is based on a retrospective analysis of 19 abdominal tomographic examinations with In-111 granulocytes performed to detect septic foci. After correction for attenuation and scattering of photons was performed, the uptake in the bone marrow of the lumbar spine was seen to be related to the liver, spleen, and tissue background activity. The results in this study were compared with corresponding data from 20 normal liver/spleen tomographic examinations performed with Tc-99m nanocolloid, which is routinely used for bone marrow scintigraphy. The bone marrow/liver activity ratio for granulocytes varied, but it exceeded the corresponding mean ratio for colloid in all examinations. The mean values for granulocyte uptake 3 and 20 hours after injection was, respectively, about 6 and almost 10 times higher than were those for colloid. The activity ratios between bone marrow and spleen as well as between bone marrow and tissue background was not improved and or may even have been reduced by the use of granulocytes. It is suggested that granulocytes labeled in vitro by Tc-99m hexamethylpropylene amineoxime (HMPAO) or in vivo by monoclonal antigranulocyte antibodies may provide techniques for improved bone marrow imaging.     

Pharmacokinetic studies of mouse monoclonal antibodies to a rat colon carcinoma: I. Comparison of biodistribution in normal rats, syngeneic tumor-bearing rats, or tumor-bearing nude mice

The pharmacokinetics of two iodine-131-(131I) labeled murine anti-rat colon carcinoma monoclonal antibodies (D3 and E4) were compared in normal Sprague Dawley rats, syngeneic BDIX rats, or nude mice bearing that tumor. Results of antibody uptake after i.v. administration were analyzed in terms of accumulation and localization indices for normal tissues and tumor. Statistically significant differences between rat and mouse tissue biodistribution were found. D3, which reacts in vitro with the tumor and several normal rat tissues, cleared quickly from the blood of rats and was specifically targeted to several normal tissues, notably the lung. Virtually no targeting to the tumor was observed. Nude mice, however, showed a slower blood clearance and specific antibody targeting only in the tumor. Similar results were seen after injection of another antibody, E4, which is tumor-specific in vitro. Data suggest that studies on the xenogeneic nude mouse model may not necessarily be relevant to the choice of monoclonal antibodies for clinical diagnostic imaging or therapy.     

Normal volunteer studies with modified 99Tcm tin colloid

99Tcm tin colloid, modified by the addition of various amounts of the surfactant Pluronic F68 was evaluated as a new liver imaging agent in normal adult male volunteers. The relative amounts taken up in the liver and spleen were measured by two quantitative methods with a view to establishing the most useful technique. The changes in biodistribution resulting from mechanical shaking during preparation of the colloids and in vitro ageing of the preparations were assessed. The pharmacokinetics of uptake into liver and spleen of the various formulations tested were independent of Pluronic F68 content. However, at low levels of Pluronic F68 the liver:spleen ratio decreased as the colloid preparation was aged before use. At high levels of Pluronic F68 there was increased background activity. An optimum formulation was identified combining low background activity with a stable pattern of biodistribution independent of preparation age.     

Radiolabeling of monoclonal antibody against carcinoembryonic antigen with 88Y and biodistribution studies

The biodistribution of the 202 monoclonal antibody against CEA labeled with 88Y by the bicyclic DTPA anhydride method was studied in normal Balb/c mice. The in vitro binding to 1 X 10(7) CO112, LS174T and WiDR colon cancer cells was 21.0, 27.3 and 18.8%, respectively. The binding to an equal number of KM-3 leukemia cells and normal human lymphocytes was 8.9 and 3.2%, respectively. Liver, spleen, kidney and blood were the tissues that showed the highest uptake of radiolabeled antibody in vivo.     

9 9mTC-紫杉醇脂质体的抑瘤作用及体内分布研究

观察＾９９ｍＴＣ紫杉醇脂质体瘤作用及其体内分布,为临床应用提供依据。方法：采用逆相蒸发法制备紫杉醇脂质体,小鼠艾氏癌实体型为实验肿瘤模型。经腹腔分别注入生理盐水,紫杉醇注射液和紫杉醇质体,观察抑瘤率和体重变化率;经尾静脉分别注入＾９９ｍＴｃ紫杉醇脂质体和＾９９ｍＴｃＯ４－洗脱液观察体内分布情况。结果紫杉醇脂质体与紫杉醇注且抑瘤率差异无显著性;同生理盐水相比,紫杉醇脂质体组的体重变化率无统计学意义,     

Radioimmunodetection of human melanoma with indium-111-labeled monoclonal antibody

The purpose of the study was threefold: (1) to evaluate the efficacy of an 111In-labeled murine monoclonal antibody (ZME-018) directed against a heavy molecular weight melanoma associated glycoprotein in localizing metastatic disease; (2) to determine the effect of unlabeled antibody mass (2.5, 5, 10, 20, and 40 mg) on labeled antibody blood clearance, biodistribution and lesion detection; (3) to estimate radiation dosimetry. Twenty-five patients with previously documented disease received an intravenous infusion of 2.5 to 40 mg of monoclonal antibody with 1 mg of the antibody labeled with 5 mCi of 111In. There were no acute reactions. Patients were scanned without computer enhancement or background subtraction techniques at 24 and 72 hr after injection. Imaging detected tumor in 14/18 (78%) patients with active disease, identified 24/44 (77%) of lesions greater than 1 cm and changed or specifically directed patient management in 22% (4/18) patients with tumor. There was a prolongation in blood clearance associated with decreased liver and spleen activity following administration of 20 and 40 mg of antibody compared to the three lower antibody dose levels. Assuming a biodistribution similar to [111In]ZME-018, the radiation dose delivered to normal tissues by [90Y]ZME-018 would restrict its use as a routine vehicle for radioimmunotherapy; however, it may be possible to deliver substantial tumor doses in selected patients.     

The effect of chelating agents on the distribution of monoclonal antibodies in mice

The potential for altering the biodistribution of radiolabel from gallium- and indium-labeled mouse monoclonal antibodies was investigated in mice using metal chelating agents. The chelating agents used were desferrioxamine (DFO), diethylenetriaminepentaacetic acid (DTPA), ethylenediamine-di (O-hydroxyphenylacetic acid) (EDHPA), and 2,2' dipyridyl (DIPY). The mouse monoclonal antibody LICR-LON-M8 was labeled with 111In after conjugation to DTPA, and with 67Ga after conjugation to DFO. All the chelating agents except DIPY altered the biodistribution of [67Ga]citrate and [111In]citrate but did not affect the 48-hr tissue uptake of label from [111In]DTPA-M8 or [67Ga]DFO-M8, confirming the in vivo stability of the antibody conjugates. Label fixed in the tissues was inaccessible to the chelating agents, indicating that they will not be suitable for reducing the high background liver radioactivity in patients undergoing scanning with indium-labeled antibodies.     

Anti-antibody enhancement of iodine-131 anti-CEA radioimmunodetection in experimental and clinical studies

Imaging of tumors with radiolabeled antibodies, especially when located in the blood-rich visceral organs, may be improved through administration of a second antibody directed against the primary tumor-associated antibody. In hamsters bearing a human colonic carcinoma xenograft producing carcinoembryonic antigen (CEA), we injected donkey anti-goat IgG 24 hr after administration of 131I-labeled goat anti-CEA IgG and achieved enhanced tumor imaging 24-48 hr later, with a significant relative decrease of radioactivity in blood and all major organs except the spleen. In seven of nine patients, this method of anti-antibody clearance of nontargeted radioactive murine monoclonal antibodies revealed sites of cancer, including liver metastases. Characterization of radioactivity in the plasma before and after administration of the second antibody confirmed that complexes were quickly formed between primary and secondary antibodies, and imaging of the patients revealed a rapid uptake of radioactivity in the liver at 2 hr that dissipated within 24 hr. Radioactivity in the spleen gradually increased over time. The method of anti-antibody immunological enhancement of cancer imaging is feasible and may reveal tumor sites missed by conventional imaging.     

Diagnostic imaging of human neuroblastoma with radiolabeled antibody

In a previous study, the authors showed that iodine-131 labeled monoclonal antibody (Mab 3F8) could be used to image human neuroblastoma xenografts in mice with excellent tumor-to-tissue ratios. In this study they report their experience with six patients scanned with radiolabeled 3F8. There was strong accumulation of the labeled antibody in viable tumor, but no significant uptake was noted in normal brain, liver, spleen, or adrenal glands. Tumor-to-nontumor activity ratios varied but were approximately 10:1-20:1. This ratio yields good contrast for visualization. Time-activity curves show that radioactivity levels in normal tissue have a half-time of about 40 hours, whereas tumor tissues show a half-time of about 60 hours. Significant gastric secretion of free iodine demonstrated that the Mab was being deiodinated. Calculated radiation doses indicate that tumors receive at least ten times the dose to other tissues. The results indicate that Mab 3F8 has clinical potential for both imaging and therapy of human neuroblastomas.     

In vivo VEGF imaging with radiolabeled bevacizumab in a human ovarian tumor xenograft.

Vascular endothelial growth factor (VEGF), released by tumor cells, is an important growth factor in tumor angiogenesis. The humanized monoclonal antibody bevacizumab blocks VEGF-induced tumor angiogenesis by binding, thereby neutralizing VEGF. Our aim was to develop radiolabeled bevacizumab for noninvasive in vivo VEGF visualization and quantification with the single gamma-emitting isotope 111In and the PET isotope 89Zr. METHODS: Labeling, stability, and binding studies were performed. Nude mice with a human SKOV-3 ovarian tumor xenograft were injected with 89Zr-bevacizumab, 111In-bevacizumab, or human 89Zr-IgG. Human 89Zr-IgG served as an aspecific control antibody. Small-animal PET and microCT studies were obtained at 24, 72, and 168 h after injection of 89Zr-bevacizumab and 89Zr-IgG (3.5 +/- 0.5 MBq, 100 +/- 6 microg, 0.2 mL [mean +/- SD]). Small-animal PET and microCT images were fused to calculate tumor uptake and compared with ex vivo biodistribution at 168 h after injection. 89Zr- and 111In-bevacizumab ex vivo biodistribution was compared at 24, 72, and 168 h after injection (2.0 +/- 0.5 MBq each, 100 +/- 4 microg in total, 0.2 mL). RESULTS: Labeling efficiencies, radiochemical purity, stability, and binding properties were optimal for the radioimmunoconjugates. Small-animal PET showed uptake in well-perfused organs at 24 h and clear tumor localization from 72 h onward. Tumor uptake determined by quantification of small-animal PET images was higher for 89Zr-bevacizumab-namely, 7.38 +/- 2.06 %ID/g compared with 3.39 +/- 1.16 %ID/g (percentage injected dose per gram) for human 89Zr-IgG (P = 0.011) at 168 h and equivalent to ex vivo biodistribution studies. Tracer uptake in other organs was seen primarily in liver and spleen. 89Zr- and 111In-bevacizumab biodistribution was comparable. CONCLUSION: Radiolabeled bevacizumab showed higher uptake compared with radiolabeled human IgG in a human SKOV-3 ovarian tumor xenograft. Noninvasive quantitative small-animal PET was similar to invasive ex vivo biodistribution. Radiolabeled bevacizumab is a new tracer for noninvasive in vivo imaging of VEGF in the tumor microenvironment.     

Targeting primary human Ph(+) B-cell precursor leukemia-engrafted SCID mice using radiolabeled anti-CD19 monoclonal antibodies.

The Philadelphia chromosome translocation (Ph(+)) confers a poor prognosis in patients with acute lymphocytic leukemia (ALL). CD19 is highly expressed (CD19(+)) on ALL cells and is an attractive target for antibody-based therapies. CLB-CD19 is an IgG1kappa murine monoclonal antibody (mAb) directed against an epitope on the CD19 antigen. METHODS: Radiolabeled CLB-CD19 antibody was evaluated for targeting ALL in a severe combined immunodeficient (SCID) mouse model engrafted with primary human leukemia cells. Lodgment of CD19(+) ALL cells in spleen and liver was confirmed using immunohistochemistry analyses. Circulating CD19(+) ALL cells in blood were also detected by flow cytometry. RESULTS: Antibody was labeled directly with the radiohalogen (125)I and radiometal (111)In via the bifunctional metal ion chelate CHX-A"-diethylenetriaminepentaacetic acid (DTPA) with retention of immunoreactivities. After intravenous injection of radioconjugates, biodistribution studies showed rapid localization of the (111)In-conjugate to leukemia-infiltrated spleen, reaching a maximum (mean +/- SD) of 72.78 +/- 13.67 % injected dose per gram of tissue (%ID/g) by 24 h after injection. In contrast, peak localization of coinjected (125)I-CLB-CD19 occurred by 4 h and was significantly lower (11.41 +/- 12.79 %ID/g) (P < 0.001). Uptake of (111)In-conjugate in the liver containing tumor was also evident but not in other normal tissues. Uptake of radiolabeled CLB-CD19 in tumor-bearing organs was specific, as uptake of radiolabeled isotype-matched antibody control was low. Gamma-camera imaging detected the uptake of (111)In-CHX-A"-DTPA CLB-CD19 in enlarged tumor-bearing spleen of engrafted mice. A single injection of 32 micro g CLB-CD19 mAb had a delayed suppressive effect on the level of circulatory leukemia cells in surviving mice and extended the median survival from 48.5 to 58 d (n = 8; P = 0.03). CONCLUSION: The radiolabeled anti-CD19 antibody showed specific targeting and rapid internalization in ALL cell-engrafted SCID mice and may also be used for selective intracellular delivery of cytotoxic radionuclides with beta-, Auger, or alpha-emissions.     

Pulsed high-intensity focused ultrasound enhances uptake of radiolabeled monoclonal antibody to human epidermoid tumor in nude mice.

The aim of this study was to determine if pulsed high-intensity focused ultrasound (HIFU) exposures could enhance tumor uptake of (111)In-MX-B3, a murine IgG1kappa monoclonal antibody directed against the Le(y) antigen. METHODS: MX-B3 was labeled with (111)In, purified, and confirmed for its binding to the antigen-positive A431 cell line. Groups of nude mice were inoculated subcutaneously with A431 tumor cells on both hind flanks. A tumor on one flank was treated with pulsed-HIFU; the other tumor was used as an untreated control. Within 10 min after the HIFU exposure, the mice received intravenous (111)In-MX-B3 for imaging and biodistribution studies. Mice were euthanized at 1, 24, 48, and 120 h after injection for biodistribution studies. RESULTS: The HIFU exposure shortened the peak tumor uptake time (24 vs. 48 h for the control) and increased the peak tumor uptake value (38 vs. 25 %ID/g [percentage injected dose per gram] for the control). The HIFU effect on enhancing tumor uptake was greater at earlier times up to 24 h, but the effect was gradually diminished thereafter. The HIFU effect on enhancing tumor uptake was substantiated by nuclear imaging studies. HIFU also increased the uptake of the antibody in surrounding tissues, but the net increase was marginal compared with the increase in tumor uptake. CONCLUSION: This study demonstrates that pulsed-HIFU significantly enhances the delivery of (111)In-MX-B3 in human epidermoid tumors xenografted in nude mice. The results of this pilot study warrant further evaluation of other treatment regimens, such as repeated HIFU exposures for greater delivery enhancement of antibodies labeled with cytotoxic radioisotopes or pulsed-HIFU exposure in addition to a combined therapy of (90)Y-B3 and taxol to enhance the synergistic effect.     

Iodine-124-labeled iodo-azomycin-galactoside imaging of tumor hypoxia in mice with serial microPET scanning

Tumor hypoxia, present in many human cancers, can lead to resistance to radiation and chemotherapy, is associated with a more aggressive tumor phenotype and is an independent prognostic factor of clinical outcome. It is therefore important to identify and localize tumor hypoxia in cancer patients. In the current study, serial microPET imaging was used to evaluate iodine-124-labeled iodo-azomycin-galactoside (¹²⁴I-IAZG) (4.2-day physical half-life) as a hypoxia imaging agent in 17 MCa breast tumors and six FSaII fibrosarcomas implanted in mice. For comparison, another promising hypoxic-cell PET radiotracer, fluorine-18-labeled fluoro-misonidazole (¹⁸F-FMISO), was also imaged in the same tumor-bearing animals. Twelve animals were also imaged with ¹⁸F-labeled fluoro-deoxyglucose (¹⁸F-FDG). In addition, histological examination was performed, and direct measurement of tumor oxygenation status carried out with the Oxylite probe system. Two size groups were used, relatively well-oxygenated tumors in the range of 80–180 mg were designated as small, and those >300 mg and highly hypoxic, as large. Based on the data from 11 MCa and six FSaII tumors, both ¹²⁴I-IAZG and ¹⁸F-FMISO images showed high tracer uptake in the large tumors. In ¹⁸F-FMISO images at 1, 3–4, and 6–8 h post-injection (p.i.), there was considerable whole-body background activity. In contrast, ¹²⁴I-IAZG imaging was optimal when performed at 24–48 h p.i., when the whole-body background had dissipated considerably. As a result, the ¹²⁴I-IAZG images at 24–48 h p.i. had higher tumor to whole-body activity contrast than the ¹⁸F-FMISO images at 3–6 h p.i. Region-of-interest analysis was performed as a function of time p.i. and indicated a tumor uptake of 5–10% (of total-body activity) for FMISO at 3–6 h p.i., and of ~17% for IAZG at 48 h p.i. This was corroborated by biodistribution data in that the tumor-to-normal tissue (T/N, normal tissues of blood, heart, lung, liver, spleen, kidney, intestine, and muscle) activity ratios of IAZG at 24 h p.i. was 1.5–2 times higher than those of FMISO at 3 h p.i., with the exception of stomach. Statistical analysis indicated that these differences in T/N ratios were significant. The small tumors were visualized in the ¹⁸F-FDG images, but not in the ¹²⁴I-IAZG or ¹⁸F-FMISO images. This was perhaps due to the combined effect of a smaller tumor volume and a lower hypoxic fraction. Oxylite probe measurement indicated a lesser proportion of regions with pO₂<2.5 mmHg in the small tumors (e.g., pO₂ was <2.5 mmHg in 28% and 67% of the data in small and large FSaII tumors, respectively), and the biodistribution data showed lower uptake of the tracers in the small tumors than in the large tumors. In the first study of its kind, using serial microPET imaging in conjunction with biodistribution analysis and direct probe measurements of local pO₂ to evaluate tumor hypoxia markers, we have provided data showing the potential of ¹²⁴I-IAZG for hypoxia imaging.     

Improved radiolabeled monoclonal antibody uptake by lavage of intraperitoneal carcinomatosis in mice

The effect of peritoneal lavage with saline on tumor and systemic uptake of intraperitoneally administered tumor-specific (131I-5G6.4) and nonspecific (125I-UPC-10) radiolabeled monoclonal antibodies was evaluated in a nude mouse model of human intraperitoneal ovarian carcinomatosis (IP3 model). Peritoneal lavage at 2 or 6 hr postintraperitoneal antibody injection significantly improves intraperitoneal tumor/nontumor uptake ratios of specific antibody apparently by limiting systemic exposure to antibody. This enhancement tends to be more dramatic if lavage is performed within 2 hr, rather than 6 hr, of intraperitoneal antibody administration, though both times result in significant improvements in target/background ratios over no lavage. Twenty-four-hour tumor/nontumor ratios for specific antibody 5G6.4 generally are 1.5-fourfold higher following lavage than those achieved in control animals, without decreasing absolute tumor uptake of specific radiolabeled antibody. By contrast, nonspecific antibody UPC-10 binding is lower in tumor and normal tissues following lavage, with no lavage-induced improvement in tumor/nontumor ratios seen. Peritoneal lavage is a simple method to allow for specific antibody binding to accessible intraperitoneal tumors yet to limit systemic exposure thus increasing the therapeutic margin. This method may have considerable applicability in the enhancement of intraperitoneal immunoconjugate delivery to intraperitoneal tumors.