Prognostic Significance of Tumor Cell Proliferation Rate as Determined by the MIB-1 Antibody in Breast Carcinoma: Its Relationship with Vimentin and p53 Protein I

I N T R O D U C T I O N Axillary lymph node status is regarded as the single most important prognostic indicator in breast cancer. However, additional prognostic factors are needed, because the majority of breast cancer patients currently diagnosed are axillary node negative, yet 25-35% will relapse (1, 2). Tumor cell proliferation as measured by methods such as tritiated thymidine uptake (3, 4), flow cytometry (5), mitotic counts (6), and assessment of proliferation-associated antigens (7-12) is regarded as a strong indicator of poor prognosis in breast cancer. However, it seems to be interrelated with other prognostic factors. For example, both vimentin positivity (13, 14) and p53 protein positivity (15, 16) hai, e been associated with an increased tumor cell proliferation rate, and all three factors seem to have prognostic significance in breast cancer (4, 16-21). From a practical point of view, it is not known which one or which combination of these markers should be used to obtain maximum reliable prognostic information. Our interest in this study was 2-fold. First, we wanted to use the MIB-1 antibody in a prognostic study in invasive ductal NOS 3 breast cancer, with the emphasis on node-negative patients. The MIB-1 antibody was generated against recombinant parts of the Ki-67 antigen (22). Ki-67 is a nuclear antigen present in G 1, S 1 G 2, and M phases of the cell cycle but not in resting cells (23). The MIB-1 antibody is particularly useful in the evaluation of the growth fraction of tumor cells, because it immunostains formalin-fixed, paraffin-embedded sections, provided they have been heated in a microwave oven (22). A significant correlation was found between the MIB-1 labeling index and that of Ki-67 on frozen sections (24) and between the MIB-1 and mitotic tumor indices and the Scarff-Bloom-Richardson histological grade of breast carcinomas (25). Our second aim was to determine whether the proliferation rate, vimentin positivity, and p53 positivity of tumor cells are dependent or independent prognostic indicators. Although vimentin (13, 14) and p53 protein (15, 16) are related to the cell proliferation rate, the prognostic effect of p53 protein seems to be related mainly to the proliferation rate of tumor cells (16), whereas vimentin is also associated with increased invasiveness of breast cancer cell lines (26). This is also reflected in vivo, in which, particularly in node-negative patients, those with vimentin-positive tumors have a significantly higher probability of visceral relapse (19). A similar association between p53 status and visceral metastases was not found (19). Therefore, we hypothesized that in nodenegative patients, the prognostic effect of vimentin, but not that of p53 protein, might be much stronger than that of the cell proliferation rate. Therefore, we assessed tumor cell proliferation by immunohistochemistry using the novel MIB-1 monoclonal antibody on microwave-treated paraffin sections of formalin-fixed, invasive, ductal NOS breast carcinomas in which the Received 5/30/95; revised 8/10/95; accepted 8/17/95. 1 This work was supported by European Union Grant CT93-0234. 2 To whom requests for reprints should be addressed. Phone: +49-551201-1486; Fax: +49-551-201-1578. 3 The abbreviations used are: NOS, not otherwise specified; ER, estrogen receptor. Cancer Research. on November 11, 2017. © 1996 American Association for clincancerres.aacrjournals.org Downloaded from 148 MIB-1, Vimentin, p53, and Prognosis vimentin and p53 protein statuses of the same tumors were already known. The results were compared with survival curves for a