The cell cycle in breast cancer

IDMIR: identification of dysregulated miRNAs associated with disease based on a miRNA-miRNA interaction network constructed through gene expression data

Micro ribonucleic acids (miRNAs) play a pivotal role in governing the human transcriptome in various biological phenomena. Hence, the accumulation of miRNA expression dysregulation frequently assumes a noteworthy role in the initiation and progression of complex diseases. However, accurate identification of dysregulated miRNAs still faces challenges at the current stage. Several bioinformatics tools have recently emerged for forecasting the associations between miRNAs and diseases. Nonetheless, the existing reference tools mainly identify the miRNA-disease associations in a general state and fall short of pinpointing dysregulated miRNAs within a specific disease state. Additionally, no studies adequately consider miRNA-miRNA interactions (MMIs) when analyzing the miRNA-disease associations. Here, we introduced a systematic approach, called IDMIR, which enabled the identification of expression dysregulated miRNAs through an MMI network under the gene expression context, where the network's architecture was designed to implicitly connect miRNAs based on their shared biological functions within a particular disease context. The advantage of IDMIR is that it uses gene expression data for the identification of dysregulated miRNAs by analyzing variations in MMIs. We illustrated the excellent predictive power for dysregulated miRNAs of the IDMIR approach through data analysis on breast cancer and bladder urothelial cancer. IDMIR could surpass several existing miRNA-disease association prediction approaches through comparison. We believe the approach complements the deficiencies in predicting miRNA-disease association and may provide new insights and possibilities for diagnosing and treating diseases. The IDMIR approach is now available as a free R package on CRAN (https://CRAN.R-project.org/package=IDMIR).

The effect of hesperetin on estrogen receptor gene expression and its relationship with the downstream pathways of estrogen receptor alpha

BACKGROUND

Estrogen receptor (ER) is a transcription factor that affects the expression of some genes involved in the progression and development of breast cancer (BC). Hesperetin (Hst) is a flavonoid that inhibits the proliferation of BC cells. In this study, we investigated the effect of Hst on the cell viability of MCF-7 cells and the gene expression of the ERα, ERβ, IL-6, Ps2, and Cyclin D1.

METHODS

In this study, cell viability was determined by MTT assay. The cells were seeded in RPMI-1640 medium and then exposed to different concentrations of Hst (0, 25, 50, 100, 200, and 400 µM) for 24 h, and IC50 was calculated. Real-time PCR was used to assess the expression of ERα, ERβ, pS2, Cyclin D1, and IL-6 mRNA. MCF-7 cells were seeded in RPMI-1640 medium and then exposed to different concentrations of Hst (0, 25, 50, 100, and 200 µM) for 24 h. Real-time PCR was carried out using a Step One Real-Time PCR System (ABI, USA) and Amplicon SYBR Green reagents.

RESULTS

The MTT assay revealed increased cytotoxicity with higher concentrations of Hst, and the IC50 was calculated at 200 µM. Real-time PCR analysis following treatment with Hst showed a significant increase in ERα gene expression at 25 µM of Hst and a decrease in expression at 50, 100, and 200 µM of Hst (p < 0.0001). ERβ gene expression significantly decreased across all concentrations of Hst (p < 0.0001), while IL-6 gene expression decreased significantly in all concentrations (p < 0.0001). pS2 gene expression increased significantly with all concentrations of Hst (p < 0.0001), while Cyclin D1 gene expression did not significantly decrease upon Hst exposure (p > 0.05).

CONCLUSIONS

The results of our study demonstrate that Hst has the ability to induce cell death in MCF-7 cells. Furthermore, it was observed that Hst reduces the expression of the ER gene and enhances its activity, which can affect the downstream pathways of the ER.

Trastuzumab effects depend on HER2 phosphorylation in HER2-negative breast cancer cell lines

The breast cancer (BC) biomarker HER2 (Human Epidermal Receptor 2) is overexpressed in 25% of BC. Only patients with HER2-positive tumors receive HER2-targeting therapies, like trastuzumab (Herceptin). However, some women with a HER2-negative BC could benefit from trastuzumab. This could be explained by the activation/phosphorylation of HER2 that can be recognized by trastuzumab. The aim of this study is to examine trastuzumab effects on HER2 phosphorylation at tyrosine Y877 (pHER2Y877). HER2 and pHER2Y877 status were evaluated in a cohort of BC patients representative of molecular subtypes distribution (n = 497) and in a series of BC cell lines (n = 7). Immunohistochemistry against pHER2Y877 was performed on tissue micro arrays. Cellular proliferation assays were performed on BC cell lines presenting different combinations of HER2 and pHER2Y877 status and treated with increasing doses of trastuzumab (0-150 μg/ml). The prevalence of pHER2Y877 in this cohort was 6%. Nearly 5% of patients with HER2-negative tumors (n = 406, 82%) overexpressed pHER2Y877. Among triple negative BC patients (n = 39, 8%), 7.7% expressed pHER2Y877. Trastuzumab treatment decreased cell proliferation in HER2-/pHER2Y877+ BC cell lines, to an extent comparable to what occurs in HER2+ cell lines, but did not affect HER2-/pHER2Y877- cell lines. Trastuzumab sensitivity in HER2-/pHER2Y877+ cell line is specific to HER2 tyrosine 877 phosphorylation. Hence, with further confirmation in a bigger cohort, trastuzumab treatment could be envisaged as a treatment option to women presenting with HER2-/pHER2+ tumors, representing more than 1000 BC women in Canada in 2019.

Robust clustering of noisy high-dimensional gene expression data for patients subtyping

Motivation

One of the most important research areas in personalized medicine is the discovery of disease sub-types with relevance in clinical applications. This is usually accomplished by exploring gene expression data with unsupervised clustering methodologies. Then, with the advent of multiple omics technologies, data integration methodologies have been further developed to obtain better performances in patient separability. However, these methods do not guarantee the survival separability of the patients in different clusters.

Results

We propose a new methodology that first computes a robust and sparse correlation matrix of the genes, then decomposes it and projects the patient data onto the first m spectral components of the correlation matrix. After that, a robust and adaptive to noise clustering algorithm is applied. The clustering is set up to optimize the separation between survival curves estimated cluster-wise. The method is able to identify clusters that have different omics signatures and also statistically significant differences in survival time. The proposed methodology is tested on five cancer datasets downloaded from The Cancer Genome Atlas repository. The proposed method is compared with the Similarity Network Fusion (SNF) approach, and model based clustering based on Student's t-distribution (TMIX). Our method obtains a better performance in terms of survival separability, even if it uses a single gene expression view compared to the multi-view approach of the SNF method. Finally, a pathway based analysis is accomplished to highlight the biological processes that differentiate the obtained patient groups.

Availability and implementation

Our R source code is available online at https://github.com/angy89/RobustClusteringPatientSubtyping.

Supplementary information

Supplementary data are available at Bioinformatics online.

IFN-γ regulates human dental pulp stem cells behavior via NF-κB and MAPK signaling

During caries, dental pulp expresses a range of pro-inflammatory cytokines in response to the infectious challenge. Interferon gamma (IFN-γ) is a dimerized soluble cytokine, which is critical for immune responses. Previous study has demonstrated that IFN-γ at relative high concentration (100 ng/mL) treatment improved the impaired dentinogenic and immunosuppressive regulatory functions of disease-derived dental pulp stem cells (DPSCs). However, little is known about the regulatory effects of IFN-γ at relative low concentration on healthy DPSC behavior (including proliferation, migration, and multiple-potential differentiation). Here we demonstrate that IFN-γ at relatively low concentrations (0.5 ng/mL) promoted the proliferation and migration of DPSCs, but abrogated odonto/osteogenic differentiation. Additionally, we identified that NF-κB and MAPK signaling pathways are both involved in the process of IFN-γ-regulated odonto/osteogenic differentiation of DPSCs. DPSCs treated with IFN-γ and supplemented with pyrrolidine dithiocarbamate (PDTC, an NF-κB inhibitor) or SB203580 (a MAPK inhibitor) showed significantly improved potential for odonto/osteogenic differentiation of DPSCs both in vivo and in vitro. These data provide important insight into the regulatory effects of IFN-γ on the biological behavior of DPSCs and indicate a promising therapeutic strategy for dentin/pulp tissue engineering in future endodontic treatment.

Effects of carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone on the growth inhibition in human pulmonary adenocarcinoma Calu-6 cells

Carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) is an uncoupler of mitochondrial oxidative phosphorylation in eukaryotic cells. Here, we evaluated the in vitro effects of FCCP on the growth of Calu-6 lung cancer cells. FCCP inhibited the growth of Calu-6 cells with an IC(50) of approximately 6.64+/-1.84 microM at 72 h, as shown by MTT. DNA flow cytometric analysis indicated that FCCP induced G1 phase arrest below 20 microM of FCCP. Treatment with FCCP decreased the level of CDKs and cyclines in relation to G1 phase. In addition, FCCP not only increased the p27 level but also enhanced its binding with CDK4, which was associated with hypophosphorylation of Rb protein. While transfection of p27 siRNA inhibited G1 phase arrest in FCCP-treated cells, it did not enhance Rb phosphorylation. FCCP also efficiently induced apoptosis. The apoptotic process was accompanied with an increase in sub-G1 cells, annexin V staining cells, mitochondria membrane potential (MMP) loss and cleavage of PARP protein. All of the caspase inhibitors (caspase-3, -8, -9 and pan-caspase inhibitor) markedly rescued the Calu-6 cells from FCCP-induced cell death. However, knock down of p27 protein intensified FCCP-induced cell death. Moreover, FCCP induced the depletion of GSH content in Calu-6 cells, which was prevented by all of the caspase inhibitors. In summary, our results demonstrated that FCCP inhibits the growth of Calu-6 cells in vitro. The growth inhibitory effect of FCCP might be mediated by cell cycle arrest and apoptosis via decrease of CDKs and caspase activation, respectively. These findings now provide a better elucidation of the mechanisms involved in FCCP-induced growth inhibition in lung cancer.

A signature-based method for indexing cell cycle phase distribution from microarray profiles

Background

The cell cycle machinery interprets oncogenic signals and reflects the biology of cancers. To date, various methods for cell cycle phase estimation such as mitotic index, S phase fraction, and immunohistochemistry have provided valuable information on cancers (e.g. proliferation rate). However, those methods rely on one or few measurements and the scope of the information is limited. There is a need for more systematic cell cycle analysis methods.

Results

We developed a signature-based method for indexing cell cycle phase distribution from microarray profiles under consideration of cycling and non-cycling cells. A cell cycle signature masterset, composed of genes which express preferentially in cycling cells and in a cell cycle-regulated manner, was created to index the proportion of cycling cells in the sample. Cell cycle signature subsets, composed of genes whose expressions peak at specific stages of the cell cycle, were also created to index the proportion of cells in the corresponding stages. The method was validated using cell cycle datasets and quiescence-induced cell datasets. Analyses of a mouse tumor model dataset and human breast cancer datasets revealed variations in the proportion of cycling cells. When the influence of non-cycling cells was taken into account, "buried" cell cycle phase distributions were depicted that were oncogenic-event specific in the mouse tumor model dataset and were associated with patients' prognosis in the human breast cancer datasets.

Conclusion

The signature-based cell cycle analysis method presented in this report, would potentially be of value for cancer characterization and diagnostics.

E1AF promotes breast cancer cell cycle progression via upregulation of Cyclin D3 transcription

E1AF transcription factor, a member of Ets family, is deregulated in many tumors and widely known to play critical roles in tumor metastasis via directly binding to the promoter of genes involved in tumor migration and invasion. Here, we found that E1AF overexpression promoted breast cancer cell cycle progression and growth in vivo as well as the transcription of cell cycle-related protein Cyclin D3. And, the interference of Cyclin D3 expression by transfecting with Cyclin D3 RNAi inhibited the positive role of E1AF in cell cycle progression. We further showed that decreasing the expression of E1AF by E1AF RNAi reduced Cyclin D3 transcription and expression, and inhibited cell cycle progression that was abrogated by Cyclin D3 overexpression. Taken together, E1AF increases cell cycle progression via upregulation of Cyclin D3 transcription, which elicits a new mechanism of breast cancer growth and a new mechanism of Cyclin D3 transcription.

Geographic patterns of advanced breast cancer in Los Angeles: associations with biological and sociodemographic factors (United States)

OBJECTIVE

Examination of patterns of advanced breast cancer may provide evidence needed to direct health care resources to those communities or population groups in greatest need. We assessed to what degree biologic, ethnic, and sociodemographic factors could explain such patterns within Los Angeles County.

METHODS

The proportion of cases of advanced disease among all breast cancer cases identified during 1992-1996 were analyzed using generalized linear mixed models with random census tract effects. Models included characteristics of the individual and her tumor, census tract of residence, and aggregated health districts.

RESULTS

Approximately 6% of cases, ranging from 4% for Asian to 10% for Black women, were diagnosed as advanced, exhibiting striking geographic patterns. Tumor histology and hormone receptor status were most predictive of advanced disease. Sociodemographic variables such as marital status, median income, and distance to nearest mammography unit showed additional association with risk.

CONCLUSIONS

These models explain most of the geographical patterns and eliminate differences between White and Hispanic but not Asian or Black women, identify subpopulations at high risk of advanced disease, and suggest cancer control opportunities.

Cell Proliferation in Breast Cancer is a Major Determinant of Clinical Outcome in Node-Positive but Not in Node-Negative Patients

The growth rate of a tumor cell population depends on two major factors: the percentage of proliferating cells (cell growth fraction) and the rapidity of their duplication (cell proliferation rate). The authors evaluated the prognostic and predictive value of both kinetics parameters in a large series of breast cancer patients (n=504). The cell growth fraction was determined by MIB-1 immunostaining, the cell proliferation rate by AgNOR analysis. Ki-67 LI (labeling index) and AgNOR area were significantly associated with histotype, histologic grade, tumor size, estrogen/progesterone receptor status, patient age, and lymph node involvement (P<0.005). In the entire series of patients, both kinetics variables were significantly and independently associated with the clinical outcome, but their prognostic relevance was quite different when node-negative and node-positive patients were considered separately. Although in node-positive patients Ki-67 LI and AgNOR area were the unique independent predictors of disease-free and overall survival, they were excluded by the multivariate Cox model in node-negative patients, where only tumor size and estrogen receptor status retained a significant P-value. These results show that in breast carcinoma the cell growth fraction and the cell proliferation rate have a different prognostic impact with respect to the lymph node status and are major determinants of clinical outcome in node-positive patients only. Within this subgroup, the rapidity of cell proliferation as assessed by AgNOR analysis also served as a sensitive predictor of the response to adjuvant treatments.

Cyclin I is expressed in human breast cancer and closely associated with VEGF and KDR expression

In the present study, cyclin I protein expression in 114 invasive human breast cancers was correlated with cell cycle and angiogenesis-related proteins and clinico-pathological data. A strong association was found between cytoplasmic cyclin I staining and VEGF (p = 0.001) as well as the VEGF receptor KDR (p = 0.001), suggesting a link between cyclin I and angiogenesis.

Expression and Signaling Activity of Wnt-5a/Discoidin Domain Receptor-1 and Syk Plays Distinct but Decisive Roles in Breast Cancer Patient Survival

Purpose: The loss of Wnt-5a, a G-protein-coupled receptor ligand, or Syk, an intracellular kinase, has in separate studies been associated with poor prognosis of breast cancer patients. Both proteins are involved in cell adhesion, a key event in epithelial cancer metastasis. Here, we have investigated whether Syk is part of the Wnt-5a/discoidin domain receptor-1 (DDR1) signaling pathway and if a signaling interaction of these proteins is important for breast cancer–specific survival.

Experimental Design: The signaling interactions between Wnt-5a/DDR1 and Syk were addressed in mammary cell lines. Their mRNA and protein levels and the respective clinical correlates were investigated in 94 cases of primary breast cancer.

Results: The expression of Wnt-5a and Syk correlated in four of five tumor cell lines. However, despite a constitutive association between Syk and the Wnt-5a-dependent adhesion receptor DDR1, we found no evidence of a Wnt-5a/DDR1-mediated activation of Syk. Instead, β1 integrins initiate the adhesion-induced activation of Syk. In tumors from breast cancer patients, the protein expression of Wnt-5a and Syk were differently regulated at the translational and transcriptional level, respectively. Analysis of breast cancer–specific survival revealed that the presence of Wnt-5a and Syk in primary tumors has good predictive value for a favorable outcome. Intriguingly, a simultaneous loss of both proteins did not reduce survival more than loss of either.

Conclusions: Despite the difference in regulation of Wnt-5a and Syk protein expression and their lack of signaling interaction, our clinical data indicate that a favorable prognosis in breast cancer requires the expression and signaling activity of both.

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.

Differential prognostic impact of the cyclins E and B in premenopausal and postmenopausal women with lymph node-negative breast cancer

Searching for new prognostic factors, we investigated the influence of cyclin expression on breast cancer prognosis. A total of 273 archival tumor specimens from patients with pT1/pT2 N0 breast cancers treated by surgery and local irradiation were immunostained for cyclins E, A and B. Outcome was evaluated as metastasis-free (MFS) and disease-specific survival (DSS) over a median observation period of 99 months. In postmenopausal women, DSS was significantly predicted by cyclin E, and in premenopausal patients by cyclin B. No statistical significance was found for cyclin A. When the prognostic impact of cyclins was compared to that of standard prognostic indicators in a multivariate analysis, both cyclin E and cyclin B were selected as independent predictors of survival in postmenopausal and premenopausal patients, respectively. After inclusion of Ki-67 in the model, cyclin E lost its significance, whereas cyclin B remained the only independent prognostic factor with a hazard ratio of 4.5 (p = 0.026) for tumor-related death. Assessment of cyclin expression may, therefore, refine current prognostic models if considered in relation to menopausal status. The prognostic relevance of cyclins is likely attributable to an influence on proliferation, cell survival and genetic instability. Awareness of the molecular mechanisms leading to deregulated cyclin expression may guide decisions for risk-adapted therapy regimens.

Expression of cyclins E, A, and B, and prognosis in lymph node-negative breast cancer

Unexpected outcomes in breast cancer demand a refinement of prognostic criteria. This study therefore investigated the prognostic relevance of cyclin expression in a cohort of 332 T1-T2 N0 infiltrating ductal carcinomas with long-term follow-up (median 99 months). By univariate analysis, tumour size, histopathological grade, hormone receptor content, cyclin E, cyclin B, and the Ki-S5 (Ki-67) index significantly predicted disease-specific and metastasis-free survival. Cyclin A did not achieve statistical significance. In a multivariate analysis, both cyclin E [relative risk (RR) 2.01, p = 0.021] and cyclin B (RR 1.85, p = 0.033) were selected as independent prognosticators of metastasis-free survival when the Ki-67 index was omitted, but only cyclin E expression was associated with disease-specific survival (RR 2.56, p = 0.006). When Ki-67 was included as a covariate, cyclin E lost its significance with respect to disease-specific survival but remained significant for metastasis-free survival. In an analogous analysis including Ki-67, the number of concurrently overexpressed cyclins did not attain statistical significance regarding disease-specific survival but was selected as the leading predictor of metastatic disease. It is concluded that combined overexpression of cyclins may imply genetic instability enhancing metastatic potential, but that survival ultimately depends on the proliferative activity of tumour cells.

A comparative study: immunohistochemical detection of cytosolic thymidine kinase and proliferating cell nuclear antigen in breast cancer

To explore the expression of cytosolic thymidine kinase 1 (TK1) as a cell proliferative marker in human breast cancers, immunohistochemistry was used to detect the expression of TK1 in 52 malignant breast lesions, 20 benign breast lesions, and 16 normal breast tissues. The results were compared to the expression of proliferating cell nuclear antigen (PCNA) in the same specimens. The TK1-labelling index (TK1-LI) and PCNA-labeling index (PCNA-LI) were significantly higher in malignant lesions than in nonmalignant lesions (p < 0.0001 and p < 0.0013, respectively). The TK1-LI (78.9%) in malignant lesions was higher compared to PCNA-LI (64.5%). No significant difference was found for TK1-LI and PCNA-LI between benign lesions and normal tissues. Concerning the tumor stages and the tumor grades, TK1-LI showed a significant correlation with the increased tumor stages (p = 0.023) and tumor grades (p = 0.009). However, PCNA-LI was neither significantly different in tumor stages (p = 0.062) nor in tumor grades (p = 0.073). We conclude that TK1 might be a more accurate marker than PCNA for estimation of cell proliferation and malignant potentials in breast carcinomas.

Expression and regulation of tumor suppressor gene maspin in breast cancer

Maspin (mammary serpin) is an inhibitor of serine proteases with tumor suppressor activity in breast cancer. Maspin was originally identified by subtractive hybridization in normal breast epithelial cells, but its expression decreased during tumor progression. The loss of maspin gene expression with increasing malignancy is by transcriptional regulation. Maspin is known to be involved in invasion and metastasis, interact with the p53 tumor suppressor pathway, and act as an inhibitor of angiogenesis. The immunohistochemical analysis and reverse-transcription polymerase chain reaction of maspin in normal human breast tissue and breast carcinoma indicated a stepwise reduction of maspin expression during the progression from ductal carcinoma in situ to invasive carcinoma to lymph node metastasis. The lack of maspin expression in breast cancer seems to be associated with a short disease-free survival and supports maspin's function as an indicator for tumor aggressiveness and metastatic potential. New studies on the gene regulation of maspin provide evidence for promising potential of possible re-expression of maspin in tumor cells. The function of maspin as a tumor suppressor gene involved in tumor invasion, metastasis, and angiogenesis may not be limited to breast cancer.

Multiparameter analyses of cell cycle regulatory proteins in human breast cancer: a key to definition of separate pathways in tumorigenesis

Breast cancer is one of the most common cancer forms affecting many women. The disease nevertheless has widely varying behavior and therefore patient outcome, and an important undertaking is to define and understand the molecular mechanisms behind these actions. Defects in the G1/S transition in the cell cycle affect both tumor proliferation and the fidelity of check points responsible for chromosomal integrity and DNA damage response and has lately been shown to represent one of a rather limited set of key aberrations in the transformation process. Many cell cycle regulatory proteins are either oncogenes or suppressor genes or are closely associated to the transformation process. The types of aberrations in the G1/S transition seem to be different in various cancers but are nevertheless often linked to clinical behaviors. In this review the role of multiparameter analyses of cell cycle regulatory proteins in breast cancer will be outlined with special attention to pattern analyses as well as the definition of two contrasting pathways in tumorigenesis defined by either cyclin D1 or cyclin F overexpression.

The cyclin D1 high and cyclin E high subgroups of breast cancer: separate pathways in tumorogenesis based on pattern of genetic aberrations and inactivation of the pRb node

In an attempt to identify subtypes of breast cancer and pinpoint patterns of cell cycle regulatory defects associated with clinical behaviour, proliferation and other transformation associated events, a multitude of cell cycle regulatory proteins were analysed in a material of 113 primary breast cancers. Increased proliferation was observed in two different scenarios; (1) with high cyclin D1 and elevated retinoblastoma protein (pRb) phosphorylation, (cyclin D1(high) tumours) or (2) with high cyclin E protein but low cyclin D1 and lack of corresponding pRb phosphorylation (cyclin E(high) tumours) indicative of an interrupted pRb pathway. Characteristic for cyclin E(high) tumours were further defects in p53, p27 and bcl-2, while c-erbB2 overexpression and c-myc amplification was found in both cyclin D1(high) and E(high) tumours. Using transfected cell lines overexpressing cyclin E, cyclin E(high) and D1(high) tumours were mimicked and the cyclin D1(high) cell line normalized the cyclin E kinase activity by an induction and redirection of p21 and p27 to the cyclin E complex whereas cyclin E(high) cell lines obtained increased kinase activity without redirection of inhibitors. Based on differences in genetic aberrations as well as function of the pRb node we therefore propose a model in which cyclin D1(high) and cyclin E(high) tumours represent two alternative mechanisms to inactivate the pRb pathway and thereby achieve unrestrained growth in the tumorogenesis of breast cancer.

MIB-1 Assessments in breast cancers

The variability of MIB-1 measurements in breast cancer was assessed in histological sections from core and excision biopsies taken simultaneously in 13 cases and sequentially (with an intervening period of 2-3 weeks) in 17 cases. Results showed no significant differences in values between cores and sections, whether taken simultaneously or sequentially. Individual pairs of cores and sections occasionally demonstrated substantial differences. The mean ratio of MIB-1 scores between cores and sections was 0.97 [95% confidence interval (CI)=0.68-1.38]. However 95% confidence intervals for ratios within individuals were 0.14-6.68. Although the two samples can be equivalent on an average over numerous patients, they cannot be taken as equivalent within individuals. Severe heterogeneity complicates the assessment of MIB-1 in individual breast cancers and limits utility in monitoring changes in proliferation with treatment.

Role of expression of cell cycle inhibitor p27 and MIB-1 in predicting lymph node metastasis in male breast carcinoma

Tumor expression of the proliferation marker (MIB-1) and the cell cycle-related protein (p27) may predict the biologic behavior of various human tumors. The purpose of this study was to evaluate the role of p27 and MIB-1 expression in predicting lymph node metastasis in male breast carcinomas (MBCs). We studied 67 patients with invasive MBC who had undergone modified radical mastectomy. Pathologic lymph node status was correlated with the p27 protein and the MIB-1 proliferation index. These factors were studied immunohistologically by standard methods. Men in this study ranged from 36 to 92 years of age (mean, 63 years); 43 (64%) were T1 lesions, and 24 (36%) were T2 lesions. Twenty-nine patients (43%) had positive nodes. p27 was expressed in 43 tumors (64%) and MIB-1 in 13 tumors (19.4%). Tumors with positive p27 showed positive lymph nodes in 10 cases (23%). In contrast, p27-negative tumors had positive lymph nodes in 18 cases (75%). Tumors positive for MIB-1 show positive lymph nodes in 11 cases (85%). However, when MIB-1 was negative, only 16 patients (30%) had positive lymph nodes. Multivariate logistic regression analysis confirmed the utility of MIB-1 overexpression in predicting lymph node metastasis ( p < 0.0006). Also, decreased p27 protein expression strongly correlates with lymph node metastasis ( p < or = 0.0001). Furthermore, when p27 was negative and MIB-1 was positive, 100% of the patients had positive lymph nodes. In contrast, when p27 was positive and MIB-1 was negative, only 12% of patients had positive lymph nodes. The reduced expression of the p27 protein and the overexpression of the MIB-1 proliferation index in this study show a significant correlation in predicting lymph nodes metastasis in MBCs.

Decline in the expression of the serine proteinase inhibitor maspin is associated with tumour progression in ductal carcinomas of the breast

Maspin is an inhibitor of serine proteinases with tumour suppressor activity. Its expression appears to be reduced in advanced stages of breast cancer. A large series of archival breast tissue specimens has been examined, including normal glands (n=7), fibrocystic change (n=22), ductal carcinoma in situ (DCIS, n=12), infiltrating carcinomas (n=128) and their lymph node metastases (n=65), using a specific monoclonal antibody. Myoepithelium invariably showed strong maspin expression. In epithelial cells, the strongest expression was found in normal breast and fibrocystic change. A significant stepwise decrease in maspin expression (p<0.0001) occurred in the sequence DCIS - invasive cancer - lymph node metastasis. However, a subset of infiltrating carcinomas showed strong maspin expression, significantly associated with a lower rate of lymph node metastasis at the time of diagnosis (p<0.01). This was independent of tumour size and grade. The in vivo observations presented here are in keeping with data obtained in prior in vitro experiments. Maspin emerges as an indicator of tumour progression and metastatic potential, and might be exploited to predict breast cancer prognosis. According to in vitro data, its tumour suppressor activity is likely to involve both the modulation of cell motility/invasiveness and the inhibition of angiogenesis.

Downregulation of the potential suppressor gene IGFBP-rP1 in human breast cancer is associated with inactivation of the retinoblastoma protein, cyclin E overexpression and increased proliferation in estrogen receptor negative tumors

The complex insulin-like growth factor network of ligands, receptors and binding proteins has been shown to be disturbed in breast cancer. In addition to defects in proteins controlling cell cycle checkpoints, this type of aberrations could affect tumor growth and survival thereby influencing both tumor aggressiveness and potential response to treatments. We have previously identified the T1A12/mac25 protein, which is identical to the IGFBP-rP1, as a differentially expressed gene product in breast cancer cells compared with normal cells. Here we compare the expression of IGFBP-rP1 in 106 tumor samples with known status of cell cycle aberrations and other clinicopathological data. This was done using a tumor tissue section array system that allows for simultaneous immunohistochemical staining of all samples in parallel. Cytoplasmic staining of variable intensity was observed in most tumors, 15% lacked IGFBP-rP1 staining completely, 20% had weak staining, 32% intermediate and 33% showed strong staining. Low IGFBP-rP1 was associated with high cyclin E protein content, retinoblastoma protein (pRb) inactivation, low bcl-2 protein, poorly differentiated tumors and higher stage. There was a significantly impaired prognosis for patients with low IGFBP-rP1 protein tumors. Interestingly, IGFBP-rP1 showed an inverse association with proliferation (Ki-67%) in estrogen receptor negative tumors as well as in cyclin E high tumors suggesting a separate cell cycle regulatory function for IGFBP-rP1 independent of interaction with the estrogen receptor or the pRb pathway.

Concurrent overexpression of p53 and c-erbB-2 correlates with accelerated cycling and concomitant poor prognosis in node-negative breast cancer

Simultaneous overexpression of c-erbB-2 and p53 has been reported to be prognostically unfavorable in breast cancer. Herein, we show that concurrent overexpression of these 2 proteins is associated with a marked reduction in the relative fraction of cells in G(1) phase of the cell cycle, indicating an accelerated cell cycle progression. Using an immunohistochemical approach, we examined 261 cases of node-negative infiltrating ductal carcinomas of the breast with respect to c-erbB-2 and p53 expression and to the proliferative activity measured by the Ki-67 index. By means of a novel monoclonal antibody, Ki-S2, which exclusively recognizes proliferating cells in the S, G(2), and M phases of the reproductive cycle, we were further able to calculate the relative fraction of the cells having passed the restriction point at the G(1)/S boundary, thus defining a cycling ratio (CR). The results were correlated with clinical outcome; median follow-up time was 96 months. Tumors that simultaneously overexpressed c-erbB-2 and p53 had a high median CR and followed an unfavorable course. However, increased CRs were also observed independently of c-erbB-2 and p53 overexpression, suggesting that other molecular mechanisms may contribute to acceleration of cell cycle progression. In a multivariate analysis that included patient age, tumor size, hormone receptor status, c-erbB-2 and p53 expression, and the Ki-67 index, CR emerged as the most significant independent predictor of overall and disease-free survival (P <.0001). It is concluded that the CR is a gauge of cell cycle deregulation and therefore may be a powerful indicator of the biologic behavior of cancers. HUM PATHOL 32:311-319.

G1-S transition defects occur in most breast cancers and predict outcome

Cell cycle deregulation is frequently observed in tumors and has moreover been proposed to be a requirement for tumor development. By analyzing the expression of p27 by immunohistochemistry in 100 primary breast tumors and combining the analyses with our earlier characterization of cyclin E, D1, p16, and the retinoblastoma protein (pRB), we have been able to cover the majority of potential G1-S transition defects and observed that 90% of the tumors had alterations in one or several cell cycle regulatory proteins. Considerable variations in protein levels were found among tumors, with low p16 expression as the most common alteration followed by cyclin E or cyclin D1 overexpression, low p27 expression or pRB inactivation in decreasing prevalence. Tumors were grouped according to observed combinations of defects and the proliferative capacity was determined for each group by analyzing Ki-67 labeling index. Low proliferation was observed in tumors with: low p16; high cyclin D1 with normal or high p16 expression; and in tumors without cell cycle defects. Tumors with high cyclin E/low p27 or pRB defects showed higher proliferation. The survival differed noticeably for patients with various combinations of cell cycle defects, and four distinctive clusters were identified showing significantly different breast cancer specific survival (p<0.0001) for both node-positive (p = 0.0006) and node-negative patients (p<0.0001). In summary, we have shown that G1-S transition defects are nearly obligatory in breast tumors and that the specific type of cell cycle defect influences the clinical behavior of the tumor.

Cyclin E dependent kinase activity in human breast cancer in relation to cyclin E, p27 and p21 expression and retinoblastoma protein phosphorylation

The cell cycle machinery is regulated by cyclin dependent kinases and sets of activating and inhibitory proteins. The G1-S control mechanism is often deregulated in tumours supposedly leading to increased kinase activity, phosphorylation of substrates and subsequent S phase entrance. Increased kinase activity has been proposed to be essential in cell cycle aberrations, but few studies have actually shown enhanced kinase activity related to specific cell cycle defects in primary tumours. In the present study we have determined the cyclin E dependent kinase activity (cyclin E(kinase)) in 59 primary breast cancers, using an H1-kinase assay, and related the activity to the expression of cyclin E, p27 and p21. In a subgroup of 48 tumours, we further characterized the association between cyclin E(kinase), in vivo phosphorylation of the retinoblastoma protein (pRb) and proliferation. The cyclin E(kinase) correlated significantly with cyclin E content and inversely with p27 and p21 expression. P27, but not p21, was associated with low cyclin E(kinase) in specimens with normal/low levels of cyclin E. At elevated cyclin E levels, suppression of cyclin E(kinase) seemed to require high levels of both p21 and p27. The cyclin E(kinase) correlated with the phosphorylation status of pRb as well as with proliferation. Surprisingly, pRb phosphorylation did not correlate with proliferation. Our results support that pRb is a substrate for cyclin E(kinase) in primary breast cancer and that deregulation of cyclin E and p27 act through increased CDK-kinase activity, but cyclin E associated events beside pRb phosphorylation might be rate-limiting for entrance into S phase.

Correlation between p53, c-erbB-2, and topoisomerase II alpha expression, DNA ploidy, hormonal receptor status and proliferation in 356 node-negative breast carcinomas: prognostic implications

Various new prognostic indicators have been identified for mammary carcinomas, but the issue of their significance remains unsettled. The prognostic impact of p53, c-erbB-2, and topoisomerase II alpha expression was investigated in relation to standard prognostic factors for carcinomas of the breast and to the tumour cell growth fraction. Paraffin-embedded specimens of 356 node-negative infiltrating ductal carcinomas were stained immunohistochemically using a polyclonal antiserum to c-erbB-2, and the monoclonal antibodies DO-1 (p53), Ki-S4 (topoisomerase II alpha), and Ki-S5 (Ki-67). The patients were followed for a median duration of 99 months. Both p53 and c-erbB-2 were significantly associated with high tumour grade, large tumour size, DNA aneuploidy, lack of steroid hormone receptors, young age, and increased topoisomerase II alpha and Ki-67 expression levels. The correlation of p53 and c-erbB-2 was not significant. Topoisomerase II alpha and Ki-67 scores closely paralleled each other, indicating that both reflect the proliferative activity of tumour cells. A univariate analysis of overall (OS), specific (SS), and disease-free survival (DFS) revealed all the above-mentioned parameters to be statistically significant except patient age, which was relevant only to overall survival. Multivariate analysis with inclusion of all covariates selected tumour size and proliferation (topoisomerase II alpha and Ki-67) indices as independent predictors of survival in all three models. No additional information was gained by p53 or c-erbB-2. It is concluded that the proliferative activity, as assessed by topoisomerase II alpha or Ki-67 immunostaining, is the most useful indicator of breast cancer prognosis, except for tumour size.

Cell cycle regulators and their abnormalities in breast cancer

One of the main properties of cancer cells is their increased and deregulated proliferative activity. It is now well known that abnormalities in many positive and negative modulators of the cell cycle are frequent in many cancer types, including breast carcinomas. Abnormalities such as defective function of the retinoblastoma gene and cyclin-dependent kinase inhibitors (for example, p16, p21, and p27), as well as upregulation of cyclins, are often seen in breast tumours. These abnormalities are sometimes coincidental, and newly described interplays between them suggest the existence of a complex regulatory web in the cell cycle.

Proliferating cell nuclear antigen (PCNA) immunolabeling as a prognostic factor in invasive ductal carcinoma of the breast in Taiwan

To evaluate the prognostic significance of proliferating cell nuclear antigen (PCNA) in breast cancer, an immunohistochemical assay was performed in 150 patients with invasive ductal carcinomas. The PCNA labeling index (PCNA-LI) was classified into two subgroups at a cut-off point of 45% that gave the best prognostic estimates for PCNA in survival analyses. Seventy-eight tumors had a low PCNA-LI of < or =45% and 72 tumors had a high PCNA-LI of >45%. A high PCNA-LI correlated significantly with p53 overexpression (P<0.03), positive axillary node (P<0.04), short disease-free survival (P<0.001) and overall survival (P<0.0002), but not with other factors. In multivariate analysis, the PCNA-LI predicted the disease-free (P<0.008) and overall survival (P = 0.0007) independently. Our study indicates that the PCNA-LI has independent prognostic value.

Telomerase activity in relation to p53 status and clinico-pathological parameters in breast cancer

Cell cycle deregulation can occur at different levels in cancer. In human breast cancer it includes overexpression of cyclins D1 and E, down-regulation of cyclin-dependent kinase inhibitors and inactivation of the retinoblastoma and p53 tumor suppressor proteins. Telomerase activity is strongly associated with an immortal phenotype and expression of telomerase is linked to the cell cycle. We have recently demonstrated a connection between specific cell cycle defects within the pRB pathway and levels of telomerase activity in breast cancer. In the present study, 106 tumors were investigated for p53 gene and protein status. By single strand conformation polymorphism (SSCP) analysis, 15% showed mutations within exons 5-8 and by immunohistochemistry (IHC), 29% were p53 positive. Tumors with a telomerase activity above median (i.e., telomerase(high)) were significantly associated with p53 protein accumulation (p = 0.004), but not with p53 gene mutations. The strongest telomerase expression was found in tumors with p53 protein accumulation. Morphologic grade, estrogen and progesterone receptor expression differed significantly between the telomerase(high) and telomerase(low) groups (p < 0.0001, p = 0.016 and p = 0.046, respectively), but no difference was observed for stage or nodal status. Telomerase(high) tumors were significantly associated with a poor prognosis for node-negative (N0) patients (p = 0.008), but not for node-positive (N+) patients, whereas the opposite was demonstrated for tumors with p53 accumulation. The survival data indicated that telomerase expression has biological importance particularly for N0 tumors, suggesting that telomerase(low) tumors constitute a group of "pre-immortalized" tumors with a good prognosis.