Prognostic and Therapeutic Implications of the MIB-1 Labeling Index in Breast Cancer

Theranostic and molecular classification of breast cancer

CONTEXT

Despite advances in breast cancer management, women continue to relapse and die of breast cancer. Traditionally, evaluation for hormone receptors (estrogen and progesterone), as well as HER2 overexpression, have guided therapy-related decision-making because they are both prognostic and predictive indicators. However, there are limitations with those studies, which can lead to improper treatment. Gene signatures have recently been shown to be of value in identifying molecular portraits of breast carcinoma and are beginning to play role in management and treatment algorithms.

OBJECTIVE

To provide a summary of the prognostic and predictive indicators of breast cancer, such as hormone receptors, HER2, and molecular gene signatures that currently help guide clinical decision making.

DATA SOURCES

Published articles from peer-reviewed journals in PubMed (US National Library of Medicine).

CONCLUSIONS

Emerging evidence shows promise that, in addition to hormone receptors and HER2 studies, evaluating tumors with gene expression profiling can provide additional prognostic and predictive information, further aiding clinical management and leading to a more personalized approach to treating breast cancer.

Signal amplification in immunohistochemistry: loose-jointed deformable heteropolymeric HRP conjugates vs. linear polymer backbone HRP conjugates

Improvements in reagents and protocols for immunohistochemistry have led to increased sensitivity of detection systems. A significant level of signal amplification was achieved by the chain-polymer conjugate technology utilizing enzyme-labeled inert "backbone" molecule of dextran (Dako). However, the relatively large size of the dextran molecule in aqueous phase appears to create spatial hindrance compromising the penetrative ability of the detection reagent. Novel AmpliStain™ detection systems (SDT GmbH, Baesweiler, Germany) seem to overcome these constraints offering a more compact and deformable conjugate design that facilitates agile penetration through the narrowest diffusion pathways in tissue sections. Here, we compared the level of signal amplification achievable with AmpliStain™-HRP (SDT) and EnVision™+-HRP (Dako). Our results show that the AmpliStain™-HRP systems allow higher dilutions of primary antibodies in both immunohistochemistry and ELISA. Compared with EnVision™+, anti-mouse AmpliStain™ enables at least three times more sensitive detection of mouse antibodies, whereas anti-rabbit AmpliStain™ is ten times more sensitive than anti-rabbit EnVision™+.

Prognostic value of proliferation in invasive breast cancer: a review

Breast cancer is the leading cause of death among solid tumours in women, and its incidence is increasing in the West. Adjuvant chemotherapy and hormonal treatment improve survival but have potentially serious side effects, and are costly. Because adjuvant treatment should be given to high risk patients only, and traditional prognostic factors (lymph node status, tumour size) are insufficiently accurate, better predictors of high risk and treatment response are needed. Invasive breast cancer metastasises haematogenously very early on, so many breast cancer prognosticators are directly or indirectly related to proliferation. Although studies evaluating the role of individual proliferation regulating genes have greatly increased our knowledge of this complex process, the functional end result-cells dividing-has remained the most important prognostic factor. This article reviews the prognostic value of different proliferation assays in invasive breast cancer, and concludes that increased proliferation correlates strongly with poor prognosis, irrespective of the methodology used. Mitosis counting provides the most reproducible and independent prognostic value, and Ki67/MIB1 labelling and cyclin A index are promising alternatives that need methodological fine tuning.

Immunohistochemical analysis of MIB-1 proliferative activity in human endometrial cancer. Correlation with clinicopathological parameters, patient outcome, retinoblastoma immunoreactivity and K-ras codon 12 point mutations

To test the prognostic utility of MIB-1 in human endometrial neoplasias, the proliferative activities of fifty-two endometrial carcinomas obtained from Polish women were assessed. We also investigated the relationship between the MIB-1 Proliferative Index and the well-known clinicopathological features of cancer (clinical stage, histological type, histological grade, depth of myometrial invasion), patient's age, overall survival, retinoblastoma immunostaining and K-ras codon 12 point mutations. The mean MIB-1 Proliferation Index was 43.8%, with a median of 36.0%. Due to the great intratumour heterogeneity of the immunoreaction, the Index ranged from 0% to 98%. A significant relationship was noted between MIB-1 expression and histological grading (p = 0.0004) and myometrial invasion of cancer (p = 0.01). Multivariate Cox regression demonstrated that the clinical stage was the only independent prognostic factor during follow-up (p = 0.025). There was a tendency towards a poorer outcome for women with a Proliferative Index of > 31% than for patients whose Index was < or = 31%; the difference, however, did not reach significance (p = 0.25; log-rank test). Interestingly, uterine cancers lacking retinoblastoma protein expression had a mean MIB-1 Proliferation Index that was nearly twice as high as in those neoplasias that stained positively for retinoblastoma (70.33% and 42.14%, respectively; p = 0.09; Mann-Whitney-U test). There were no significant differences between K-ras codon 12 point mutation-positive and -negative endometrial carcinomas regarding the proliferative activity of the cancer (mean Indexes 47.6% and 43.8%, respectively; p = 0.66, Mann-Whitney-U test). Our data support the view that MIB-1 proliferative activity was significantly increased with a decrease of the histological grading and with the myometrial invasion of human endometrial cancer.