Condensed chromatin staining of CKAP2 as surrogate marker for mitotic figures

Purpose Proliferation activity has long been known to be one of the strongest prognostic factors in many different cancers. Nevertheless, microscopic evaluation of mitotic figures remains time-consuming and, furthermore, is relatively subjective. As the expression of cytoskeleton-associated protein 2 (CKAP2) is closely related to the mitotic phase, CKAP2 was evaluated as a surrogate mitotic figure (MF) marker. Methods A monoclonal antibody specific to human CKAP2 was produced, and immunohistochemistry was performed on normal tissue array sections and 30 breast cancer tissues. Results The expression of CKAP2 in the normal human tissues was limited to well-known cell proliferation zones. Strong, readily visible, condensed chromatin staining of CKAP2 was observed specifically in mitotic cells, and the number of these cells was tightly correlated with the MF count in breast cancer tissues (P<0.001, q=0.743), suggesting its usefulness as a surrogate marker for MF counting. Conclusion Immunohistochemical staining with CKAP2 monoclonal antibody can be considered to be a new, effective approach to the assessment of proliferation activity in cancer tissues.