Cell Membrane Reactivity of MIB-1 Antibody to Ki67 in Human Tumors: Fact or Artifact?

Abstract

Ki67 immunohistochemistry is a widely used marker of the tumor proliferative fraction. Apart from the nuclear staining of dividing cells, MIB-1 monoclonal antibody was also found to stain the cell membrane of some tumor types. Indeed, such membrane reactivity was proposed as a diagnostic feature of hyalinizing trabecular tumor (HTT) of the thyroid. To verify the diagnostic role of Ki67 membrane pattern, 6 HTTs, 8 pulmonary sclerosing hemangiomas (SH), and 6 other human tumors with MIB-1 cell membrane immunoreactivity were stained by immunoperoxidase with 5 different anti-Ki67 antibodies in different experimental conditions. We show here that the cell membrane reactivity reported in HTT is produced only by MIB-1 and not by other antibodies to Ki67 (including commercially available mouse and rabbit monoclonal antibodies). In addition, this peculiar pattern is obtained only if the reaction is performed at room temperature, because automated immunostainers which operate at 37 degrees C do not produce any MIB-1 membrane localization. The same findings were obtained in the other 6 tumors. Conversely, sclerosing hemangioma of the lung did not produce any MIB-1 cell membrane reactivity in our hands. A cross-reactivity of the MIB-1 monoclonal antibody with an epitope expressed at the cell membrane level (rather than an artifact) seems the most likely explanation for this finding, because the immunoreactivity is generally intense and uniform in the membrane positive tumors. We conclude that when Ki67 immunohistochemistry is used for diagnostic purposes in a suspected HTT, only MIB-1 clone at room temperature should be employed.

Hyalinizing trabecular tumor of the thyroid: Case report and review of the literature

“…MIB-1 staining pattern is useful as the membrane-positive reactivity is a distinctive feature of HTT, however, no such pattern appears in PTC. Notably, it has been reported that the membrane-positive pattern is observed for the MIB-1 clone only but not other clones of Ki-67, which was also confirmed in our present study (16).…”

Long Non-Coding RNA LINC01260 Inhibits the Proliferation, Migration and Invasion of Spinal Cord Glioma Cells by Targeting CARD11 Via the NF-κB Signaling Pathway

“…Based on bioinformatics prediction, the binding site for LINC01260 and CARD11 were present in the CARD11 3' untranslated region (UTR), with a free energy between of ΔG = -76. 38 and ΔG/n = -0.066. Therefore, CARD11 was confirmed as a target gene for LINC01260.…”

Re-evaluation of MIB-1 immunostaining for diagnosing hyalinizing trabecular tumour of the thyroid: semi-automated techniques with manual antigen retrieval are more accurate than fully automated techniques

“…The aberrant staining pattern was not identified in other thyroid tumours [5][6][7], and other Ki-67 clones, such as 7B11, KIS5, KI88, and SP6, did not show this phenomenon [3,8]. Therefore, immunostaining for MIB-1 has been generally used in diagnosing HTT.…”

“…Of note, the aberrant staining pattern is also observed in breast carcinoma [9], salivary gland pleomorphic adenoma [10], and pulmonary sclerosing hemangiomas [11], but no diagnostic significance has been demonstrated. Leonardo et al described that crossreactivity of MIB-1 monoclonal antibody with a cell membrane epitope seems the most likely explanation for the findings [8].…”