Authors
1
Ph.D. Student in Medical Physics, Medical Physics Dept., Tarbiat Modarres University, Tehran, Iran
2
Assistant Professor, Medical Physics Dept., Tarbiat Modarres University, Tehran, Iran.
3
Assistant Professor, Radioisotope Dept., Nuclear Research Center, Atomic Energy Organization of Iran, Tehran, Iran.
4
Professor, Medical Biotechnology Dept., Tarbiat Modarres University, Tehran, Iran.
5
-Associate Professor, Radioisotope Dept., Nuclear Research Center, Atomic Energy Organization of Iran, Tehran, Iran.
6
B. Sc. Radioisotope Dept., Nuclear Research Center, Atomic Energy Organization of Iran, Tehran, Iran.
7
M. Sc. Radioisotope Dept., Nuclear Research Center, Atomic Energy Organization of Iran, Tehran, Iran.
8
Professor, Immunology Dept., Tarbiat Modarres University, Tehran, Iran.
9
Ph.D. Student in Medical Physics, Medical Physics Dept., Tarbiat Modarres University, Tehran, Iran.
10
Ph.D. Student in Medical Biotechnology, Medical Physics Dept., Tarbiat Modarres University, Tehran, Iran
11
Professor, Pathology Dept., Tarbiat Modarres University, Tehran, Iran.
12
Assistant Professor,Laboratory Animal Sciences Dept., Institue Pastor, Tehran, Iran.
Abstract
Introduction: The radioimmunoscintigraphy (RIS) has found widespread clinical applications in
tumor diagnosis. Human epithelial mucin, MUC1, is commonly over expressed in
adenocarcinoma including 80% of breast cancers and represents a useful target for RIS. The PR81
is a new murine anti-MUC1 monoclonal antibody that was found to react with the membrane
extracts of several human breast cancerous tissues and the cell surface of some MUC1 positive
cell lines. In this study, a direct method which is very simple, rapid and efficient for the labeling
of this MAb with 99mTc, particularly suitable for the development of a ‘kit’, was developed. The
quality control of new radiopharmaceutical and immunoscintigraphy studies in BALB/c mice
bearing breast tumor xenografts were also performed.
Materials and Methods: The Ab reduction was performed with 2-mercaptoethanol (2-ME) at a
molar ratio of 2000:1 (2-ME:MAb) and reduced Ab was labeled with 99mTc via methylene
diphosphonate (MDP) as a transchelator. The labeling efficiency was determined by ITLC. The
amount of radiocolloids was measured by cellulose nitrate electrophoresis. The stability of the
labeled product was checked in fresh human serum by gel filtration chromatography (FPLC) over
24 hrs. The integrity of the labeled MAb was checked by the means of SDS-PAGE. Cell-binding
assay was used to test the binding ability of 99mTc-PR81 to MCF7 cells. Biodistribution was
studied in normal BALB/c mice at 4 and 24 hrs post-injection. The tumor imaging was performed
in female BALB/c mice with breast tumor xenografts 24 hrs after the new complex injection.
Results: The labeling efficiency was 94.2%±2.3 and radiocolloids were 2.5%±1.7. In vitro
stability was 70%±5.7 in fresh human serum over 24 hrs. There was no significant Ab
fragmentation due to the labeling procedure. Both the labeled and unlabeled PR81 were able to
compete for binding to MCF7 cells. The biodistribution studies in normal BALB/c mice showed
that there was no important accumulation in any organ. The immunoscintigraphy studies
demonstrated definite localization of the preparation at the site of tumors with high sensitivity.
Discussion and Conclusion: The results show that by using the Schwarz method of radiolabeling
MAb PR81, a labeling yield higher than 90% with high stability of the complex in human serum
can be obtained. These findings demonstrated that the new radiopharmaceutical can be considered
as a promising candidate for imaging of human breast cancer.
Keywords
Main Subjects