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

Abstract

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.

Keywords: ¹¹¹In; MUC1; PR81; breast tumor; radioimmunoscintigraphy.