Immunohistochemical Expression of p16, MCM2, Topo II and MCM2/Topo II in Cervical Squamous Intraepithelial Lesions
A Heras, W Bakeman, A Sanchez, G King, G Ghirardi. BIO SB, Inc., Santa Barbara, CA; Hospital Cordoba, Cordoba, Argentina
Background: The protein p16INK4a (p16) is a cell-cycle regulator that has shown to help in the detection of high-risk HPV infections. Minichromosome maintenance protein 2 (MCM2) is essential for eukaryotic DNA replication and drives the formation of pre-replicative complexes, which is the key first step during G1 phase. DNA Topoisomerase II (Topo II) is a nucleic enzyme that affects the topological structure of DNA by interacting with the double-helix DNA, thus playing an important role in DNA replication, transcription, recombination, condensation, and segregation. The objective of this study was to evaluate the IHC expression of p16, MCM2, Topo II, and MCM2/Topo II in different grades of malignancy of cervical squamous intraepithelial lesions.
Design: The expression p16 (clone 16P04), MCM2 (rabbit polyclonal), Topo II (clone 3F6) and a cocktail of MCM2/Topo II in 119 surgically resected FFPE tissues (43 normal, 40 LSIL and 36 HSIL's) was analyzed using IHC. Results were reported as follows: 0 when immunostaining was found only in the parabasal and basal cells, 1+ when 1/3 of the epithelium showed immunoreactivity, 2+ when 2/3 of the epithelial layer produced immunostainings and 3+ when positive reactions were seen throughout the cervical epithelium, including superficial cells. An independent sample T-test was used to compare the expression of the different markers in normal, LSIL and HSIL samples.
Results: p16, MCM2, Topo II, and MCM2/Topo II showed a statistically significant difference of expression among normal, LSIL and HSIL (p <0.001), with increased immunoexpression correlating with higher degree of malignancy for all markers. MCM2 and MCM2/Topo II were always expressed in higher quantities than p16 and Topo II in LSIL (p<0.001). The average immunopositivity for p16, MCM2, Topo II, and MCM2/Topo II in LSIL was 1.28, 1.71, 0.45 and 1.76, and in HSIL was 2.5, 2.4, 1.05 and 2.5, respectively. There was a 100% correlation in the expression and localization of IHC signals for p16, MCM2 and MCM2/Topo II in both LSIL and HSIL's.
Conclusions: The results of the current study show that expression patterns of MCM2 and MCM2/TOPO II correlate with p16, especially in HSIL. Their IHC expression is closely associated with progression of cervical squamous intraepithelial lesions, and they may be useful markers for assessing the staging of SIL's. MCM2/TOPO II increases the diagnostic sensitivity for both LSIL and HSIL's.
Tuesday, March 10, 2009 1:00 PM
Platform Session: Section C, Tuesday Afternoon