Preparation and preclinical characterization of 111In-DTPA-Anti-MUC1 as a radioimmunoconjugate for diagnosis of breast cancer by single-photon emission computed tomography.

Context: Targeting MUC1 antigens which are overexpressed in 80% of breast cancers can be widely used in the field of radioimmunoscintigraphy (RIS) of breast cancer. Aims: The aim of this study was to develop a new diagnostic labeled compound for breast cancer RIS. Settings and Design: In this study, an efficient indirect labeling method of PR81 with Indium-111 was developed and preliminary preclinical qualifications were reported. Subjects and Methods: 111In-DTPA-PR81 was prepared and its radiochemical purity and stabilities in human serum and in phosphate-buffered saline (PBS) buffer were surveyed. Furthermore, cellular studies including complex reactivity, binding specificity, cell toxicity, etc., were examined. Finally, biodistribution and scintigraphy of the complex were studied in normal and tumoral animals. Statistical Analysis Used: Statistical analyses were performed using SPSS 10.0. Results: 111In-DTPA-PR81 was prepared with a radiochemical purity of >99% at optimized conditions. Stability studies showed the radiochemical purity of >90% in PBS buffer after 96 h, while the stability in human serum showed decrement to 81% after 96 h. Reactivity of the complex with MUC1 was significantly (P < 0.005) higher than bovine serum albumin (BSA) (about 7-8 times), even though BSA concentration was about twice the MUC1. The binding specificity of the complex to the MUC1 antigen was confirmed by means of immunoreactivity assay. Cell toxicity examination showed no significant lethal effect of the radiolabeled compound on the cells. Biodistribution studies of the complex in normal rats were consistent with the biodistribution of antibodies and high accumulation was observed in the tissues expressing MUC1 antigen. The results of 111In-DTPA-PR81 scintigraphy in tumoral female BALB/c mice at 24 and 48 h after injection showed an increasement of the accumulation in the tumor site. Conclusions: 111In-DTPA-PR81 can be considered as a potential agent for imaging of the MUC1 +breast tumors.

Internalization capabilities of gold-198 nanoparticles: Comparative evaluation of effects of chitosan agent on cellular uptake into MCF-7.

In this study, internalization of positively charged chitosan-coated nanoparticles (198AuNPs@chitosan) on MCF-7 cells was investigated by γ-ray spectroscopy and then statistically compared to that of 198Au and negatively charged citrate-stabilized nanoparticles (198AuNPs). Sub-50 nm 198AuNPs@chitosan had a higher internalization compared to 198Au and 198AuNPs (p < 0.05). More cellular uptake of 198AuNP@chitosan means a higher dose of radioactivity to the tumor cells which, in turn, more effective treatment of the cancer.

Development of [64Cu]-DOTA-PR81 radioimmunoconjugate for MUC-1 positive PET imaging.

OBJECTIVE: Breast cancer radioimmunoscintigraphy targeting MUC1 expression is a growing field of work in nuclear medicine research. PR81 is a monoclonal antibody that binds with high affinity to MUC1, which is over expressed on breast tumors. In this study, we report production, quality control and preclinical qualifications of a copper-64 labeled PR81 for PET imaging of breast cancer. METHODS: PR81 was conjugated with DOTA-NHS-ester and purified by molecular filtration followed by chelate:mAb ratio determination by spectrophotometric method. DOTA-PR81 was labeled with (64)Cu followed by radiochemical purity, in vitro stability, in vitro internalization and immunoreactivity determination. The tissue biodistribution of the (64)Cu-DOTA-PR81 and (64)Cu-DOTA-hIgG was evaluated in BALB/c mice with breast carcinoma tumors using tissue counting and imaging. RESULTS: The radiochemical purity of radioimmunoconjugate was >95±1.9% (ITLC) (specific activity; 4.6 µCi/µg). The average number of chelators per antibody was 3.4±0.3:1. The (64)Cu-DOTA-PR81 showed immunoreactivity towards MUC1 antigen and MCF7 cell line with significant in vitro stability (>89% in PBS and 78±0.5% in human serum) over 48 h. Maximum internalized activity of radiolabeled PR81 in 4-8 h was 81.5%. The biodistribution and scintigraphy studies showed the accumulation of the complex at the site of tumors with high sensitivity and specificity compared to control probes. CONCLUSION: The results showed that (64)Cu-DOTA-PR81 may be considered as a potential PET tracer for diagnosis and follow-up of MUC1 expression in oncology.