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MIB-1 immunostaining on cytological samples: a protocol without antigen retrieval
I Srebotnik Kirbis1, M Strojan Flezar, M Us Krasovec
1Department of Cytopathology, Institute of Oncology, Zaloska, Ljubljana, Slovenia. ikirbis@onko-i.si
Abstract:
The aim of the study was to evaluate the effect of fixation procedures on MIB-1 immunostaining on microwave-treated Papanicolaou-stained slides and to establish protocol for MIB-1 immunostaining on cytological samples without microwave pre-treatment. Cytospins for immunostaining and nuclear suspension for DNA measurement were prepared from human breast cancer cell line (MCF-7). Following fixation, the cytospins were either stained by Papanicolaou, stored in methanol or air-dried. Antigen retrieval by microwave was used before MIB-1 immunostaining only for Papanicolaou-stained cytospins. Air-dried cytospins and cytospins stored in methanol were immunostained without pre-treatment. The percentage of MIB-1 positive cells was compared with the S phase fraction of MCF-7 cells calculated from DNA histograms. Variations in fixation procedures used before Papanicolaou staining had no influence on the percentage of MIB-1 positive cells. The difference between the percentage of the MIB-1-positive cells on microwave-treated Papanicolaou-stained cytospins and on methanol-fixed cytospins without microwave pre-treatment was not significant. There was a strong correlation between the percentage of the MIB-1-positive cells and S phase fraction. Monoclonal antibody MIB-1 recognized Ki-67 antigen in Papanicolaou-stained cytospins treated by microwave as well as in cytospins that were fixed and stored in methanol without microwave pre-treatment.
Insights
This study found that MIB-1 immunostaining is effective on both microwave-treated Papanicolaou-stained slides and methanol-fixed cytological samples without microwave pre-treatment. Results strongly correlate MIB-1 positive cells with the S phase fraction, validating the Ki-67 antigen detection method.
Area of Science:
- Cytopathology
- Immunohistochemistry
- Cell Biology
Background:
- Standardization of MIB-1 immunostaining protocols is crucial for accurate Ki-67 antigen detection in cytological samples.
- Microwave-based antigen retrieval is commonly used for Papanicolaou-stained slides, but alternative methods for non-pre-treated samples are needed.
Purpose of the Study:
- To assess the impact of different fixation methods on MIB-1 immunostaining results in Papanicolaou-stained cytological specimens.
- To develop a reliable protocol for MIB-1 immunostaining on cytological samples without requiring microwave pre-treatment.
Main Methods:
- Human breast cancer cells (MCF-7) were used to prepare cytospins.
- Cytospins underwent fixation, Papanicolaou staining, methanol storage, or air-drying.
- MIB-1 immunostaining was performed with and without microwave antigen retrieval.
- DNA histograms were used to determine the S phase fraction for comparison.
Main Results:
- Fixation variations before Papanicolaou staining did not significantly affect MIB-1 positive cell percentages.
- MIB-1 staining on microwave-treated Papanicolaou slides showed no significant difference compared to methanol-fixed slides without microwave treatment.
- A strong positive correlation was observed between MIB-1 positive cell percentage and the S phase fraction.
Conclusions:
- Monoclonal antibody MIB-1 effectively detects the Ki-67 antigen in both microwave-treated Papanicolaou-stained and methanol-fixed cytological samples.
- The study validates MIB-1 immunostaining as a reliable method for assessing cell proliferation in cytological specimens, correlating well with DNA-based S phase fraction analysis.
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