Karin Collett

EZH2 Expression Is Associated With High Proliferation Rate and Aggressive Tumor Subgroups in Cutaneous Melanoma and Cancers of the Endometrium, Prostate, and Breast

PURPOSE EZH2 is a member of the polycomb group of genes and important in cell cycle regulation. Increased expression of EZH2 has been associated previously with invasive growth and aggressive clinical behavior in prostate and breast cancer, but the relationship with tumor cell proliferation has not been examined in human tumors. The purpose of this study was to validate previous findings in a population-based setting, also including tumors that have not been studied previously. PATIENTS AND METHODS In our study of nearly 700 patients, we examined EZH2 expression and its association with tumor cell proliferation and other tumor markers, clinical features, and prognosis in cutaneous melanoma and cancers of the endometrium, prostate, and breast. RESULTS Strong EZH2 expression was associated with increased tumor cell proliferation in all four cancer types. Associations were also found between EZH2 and important clinicopathologic variables. EZH2 expression showed significant prognostic impact in melanoma, prostate, and endometrial carcinoma in univariate survival analyses, and revealed independent prognostic importance in carcinoma of the endometrium and prostate. CONCLUSION Our findings point at EZH2 as a novel and independent prognostic marker in endometrial cancer, and validate previous findings on prostate and breast cancer. Further, EZH2 expression was associated with features of aggressive cutaneous melanoma. The fact that EZH2 might identify increased tumor cell proliferation and aggressive subgroups in several cancers may be of practical interest because the polycomb group proteins have been suggested as candidates for targeted therapy. EZH2 expression should, therefore, be further examined as a possible predictive factor.

Axl is an essential epithelial-to-mesenchymal transition-induced regulator of breast cancer metastasis and patient survival

Metastasis underlies the majority of cancer-related deaths. Thus, furthering our understanding of the molecular mechanisms that enable tumor cell dissemination is a vital health issue. Epithelial-to-mesenchymal transitions (EMTs) endow carcinoma cells with enhanced migratory and survival attributes that facilitate malignant progression. Characterization of EMT effectors is likely to yield new insights into metastasis and novel avenues for treatment. We show that the presence of the receptor tyrosine kinase Axl in primary breast cancers independently predicts strongly reduced overall patient survival, and that matched patient metastatic lesions show enhanced Axl expression. We demonstrate that Axl is strongly induced by EMT in immortalized mammary epithelial cells that establishes an autocrine signaling loop with its ligand, Gas6. Epiallelic RNA interference analysis in metastatic breast cancer cells delineated a distinct threshold of Axl expression for mesenchymal-like in vitro cell invasiveness and formation of tumors in foreign and tissue-engineered microenvironments in vivo. Importantly, in two different optical imaging-based experimental breast cancer models, Axl knockdown completely prevented the spread of highly metastatic breast carcinoma cells from the mammary gland to lymph nodes and several major organs and increased overall survival. These findings suggest that Axl represents a downstream effector of the tumor cell EMT that is required for breast cancer metastasis. Thus, the detection and targeted treatment of Axl-expressing tumors represents an important new therapeutic strategy for breast cancer.

Expression of Enhancer of Zeste Homologue 2 Is Significantly Associated with Increased Tumor Cell Proliferation and Is a Marker of Aggressive Breast Cancer

The polycomb group protein enhancer of zeste homologue 2 (EZH2) has been linked to invasive properties of aggressive breast cancer. In this report, tissue microarray analysis of 190 breast carcinomas from a nested case-control study shows that EZH2 is significantly associated with interval breast cancers. Further, a strong relationship was found with tumor cell proliferation (by Ki-67 expression), locally advanced disease, metastasis at presentation, markers of the basal epithelial phenotype (positivity for cytokeratin 5/6 or P-cadherin), and p53 status. EZH2 expression was also significantly associated with glomeruloid microvascular proliferation, an aggressive angiogenic phenotype. For prediction of aggressive disease (any event of locally advanced disease, lymph node spread, or distant spread), EZH2 was the only variable of significance in multivariate analysis, whereas no additional information was given by Ki-67. Although EZH2 expression was significant in univariate survival analysis, only tumor cell proliferation and lymph node status were significant in the final multivariate model. In conclusion, our findings indicate an important relationship not only between EZH2 and markers of tumor cell proliferation but also with aggressive disease. These findings might be practically important and relevant because the polycomb group proteins have recently been suggested as candidates for targeted therapy.

A Basal Epithelial Phenotype Is More Frequent in Interval Breast Cancers Compared with Screen Detected Tumors

Interval breast cancer reduce the effectiveness of mammography screening programs. We studied 95 interval cancers, diagnosed during 1996 to 2001 as part of the population-based Norwegian Breast Cancer Screening Program. These cases were matched on size (±2.0 mm) to 95 screen-detected breast cancers, and the tumors were compared by immunohistochemical methods using tissue microarrays. Patients with interval cancers were more likely to be younger [odds ratio (OR), 4.7; P = 0.0001], to have dense breasts (OR, 3.4; P = 0.004), and to have estrogen receptor–negative tumors (OR, 2.6, P = 0.01), and p53 expression was more frequent (OR, 4.0; P = 0.001). Notably, interval cancers were more likely to have a basal epithelial phenotype, in that expression of cytokeratin 5/6 (OR, 2.3; P = 0.04) and P-cadherin (OR, 2.5; P = 0.04) was more frequent in interval cases than in size-matched, screen-detected tumors. In a logistic regression model, p53 expression, age, and breast density were independent predictors of interval cancers. Our data suggest that breast cancers with a basal epithelial phenotype are more likely than nonbasal breast cancers to present between regular mammograms.

Suppression of heat shock protein 27 induces long-term dormancy in human breast cancer

The mechanisms underlying tumor dormancy have been elusive and not well characterized. We recently published an experimental model for the study of human tumor dormancy and the role of angiogenesis, and reported that the angiogenic switch was preceded by a local increase in VEGF-A and basic fibroblast growth factor. In this breast cancer xenograft model (MDA-MB-436 cells), analysis of differentially expressed genes revealed that heat shock protein 27 (HSP27) was significantly up-regulated in angiogenic cells compared with nonangiogenic cells. The effect of HSP27 down-regulation was further evaluated in cell lines, mouse models, and clinical datasets of human patients with breast cancer and melanoma. Stable down-regulation of HSP27 in angiogenic tumor cells was followed by long-term tumor dormancy in vivo. Strikingly, only 4 of 30 HSP27 knockdown xenograft tumors initiated rapid growth after day 70, in correlation with a regain of HSP27 protein expression. Significantly, no tumors escaped from dormancy without HSP27 expression. Down-regulation of HSP27 was associated with reduced endothelial cell proliferation and decreased secretion of VEGF-A, VEGF-C, and basic fibroblast growth factor. Conversely, overexpression of HSP27 in nonangiogenic cells resulted in expansive tumor growth in vivo. By clinical validation, strong HSP27 protein expression was associated with markers of aggressive tumors and decreased survival in patients with breast cancer and melanoma. An HSP27-associated gene expression signature was related to molecular subgroups and survival in breast cancer. Our findings suggest a role for HSP27 in the balance between tumor dormancy and tumor progression, mediated by tumor–vascular interactions. Targeting HSP27 might offer a useful strategy in cancer treatment.

Independent prognostic value of the basal-like phenotype of breast cancer and associations with EGFR and candidate stem cell marker BMI-1

Aims:  To study the relationship between basal‐like breast cancers, epidermal growth factor receptor (EGFR) and candidate stem cell markers (BMI‐1, EZH2, Oct‐4) in a population‐based setting.

Prognostic role of oestrogen and progesterone receptors in patients with breast cancer: relation to age and lymph node status.

AIMS: To consider the prognostic role of oestrogen receptor and progesterone receptor status in relation to the age at surgery, length of follow up and lymph node status. METHODS: The study population comprised 977 patients with histologically confirmed breast carcinoma, with a median follow up of nine years. The actuarial life table method was used to test for survival differences. The Cox proportional hazard model was used to test for interaction effects between each hormone receptor and age, lymph node status and length of follow up. As the analysis involved multiple subgroups, significance was set at the 1% level (p < 0.01). RESULTS: When the patients were subdivided into groups according to lymph node status and age, progesterone and oestrogen receptor status predicted prognosis in middle aged (46-60 years) patients with lymph node positive breast cancer. Their prognostic effect in this subgroup, however, was restricted to the first five years after surgery. Progesterone receptor status was the strongest predictor of outcome. CONCLUSION: The prognostic power of oestrogen and progesterone receptor status varies depending on age, lymph node status and length of follow up after surgery.

Evaluation of Ki67 Expression across Distinct Categories of Breast Cancer Specimens: A Population-Based Study of Matched Surgical Specimens, Core Needle Biopsies and Tissue Microarrays

Introduction Tumor cell proliferation in breast cancer is strongly prognostic and may also predict response to chemotherapy. However, there is no consensus on counting areas or cut-off values for patient stratification. Our aim was to assess the matched level of proliferation by Ki67 when using different tissue categories (whole sections, WS; core needle biopsies, CNB; tissue microarrays, TMA), and the corresponding prognostic value. Methods We examined a retrospective, population-based series of breast cancer (n = 534) from the Norwegian Breast Cancer Screening Program. The percentage of Ki67 positive nuclei was evaluated by visual counting on WS (n = 534), CNB (n = 154) and TMA (n = 459). Results The median percentage of Ki67 expression was 18% on WS (hot-spot areas), 13% on CNB, and 7% on TMA, and this difference was statistically significant in paired cases. Increased Ki67 expression by all evaluation methods was associated with aggressive tumor features (large tumor diameter, high histologic grade, ER negativity) and reduced patient survival. Conclusion There is a significant difference in tumor cell proliferation by Ki67 across different sample categories. Ki67 is prognostic over a wide range of cut-off points and for different sample types, although Ki67 results derived from TMA sections are lower compared with those obtained using specimens from a clinical setting. Our findings indicate that specimen specific cut-off values should be applied for practical use.

The prognostic contribution of estrogen and progesterone receptor status to a modified version of the Nottingham Prognostic Index

The aim of this study was to test the prognostic contribution of estrogen (ER) and progesterone (PgR) receptor status to an index consisting of the number of positive lymph nodes, the mean nuclear area of the breast cancer cells (MNA), and tumour diameter. This index is compared with a Danish index, which includes the same factors but uses histological grade instead of MNA. The Danish index has been developed from the Nottingham Prognostic Index (NPI). In the present study of 1629 breast cancer patients the Cox proportional hazard method is used to examine the time-dependency of the index, and to test for interaction between the index and the hormone receptors. The index sorts the patients into groups with low, intermediate, and high risk of dying. Logistic regression analysis is used to report the sensitivity and specificity of the index with and without ER and PgR. Our index gave information comparable to that of the Danish group. However, the information given by our index is time-dependent, its strength being weaker after 5-year of follow-up. PgR and ER add information to high risk patients, but only in the first 5-year period. High risk patients with positive hormone receptors have a prognosis similar to intermediate risk ones. PgR increases the ability of the index to predict breast cancer deaths correctly by 5 percent in high risk patients. In conclusion, PgR and ER act differently in groups of patients with different risk levels when time-dependency is considered. This indicates biological differences in subgroups as defined by the index.

Estrogen receptor β– an independent prognostic marker in estrogen receptor α and progesterone receptor‐positive breast cancer?

Both subtypes of estrogen receptor (ER), ERα and ERβ, are normally present in the mammary gland. The role of ERα as a prognostic marker in breast cancer is well established due to the beneficial effect of providing tamoxifen as adjuvant therapy. The role of ERβ, however, is less clear. To gain insight into the importance of ERβ in breast cancer, 145 primary breast cancers were examined by immunohistochemistry for ERβ, and the expression level was compared with ERα and progesterone receptor (PR) status. Especially, we wanted to examine the significance of ERβ in the contrasting ERα+/PR+ and ERα−/PR− subgroups. In the ERα+/PR+ subgroup (dual positive), the survival difference between patients with low, medium and high ER β level was statistically significant (p = 0.004), with more than 70% of patients with medium and high ERβ levels surviving 100 months, compared with less than 30% in the group with low ERβ level. Further, for ERα+/PR+ patients there was a reduced risk of fatal outcome by multivariate analysis with increasing ERβ levels (p(trend) < 0.01 [univariate analysis]; p(trend) = 0.05 [multivariate analysis]). The risk was 31% and 27% for medium and high ERβ levels, respectively, compared with low ERβ level, adjusting for standard prognostic factors such as tumor diameter, nuclear tumor grade (quantified by mean nuclear area), lymph node status, and patient age at operation. For patients with ERα−/PR− tumors (dual negative), however, there was no association between ERβ levels and patient outcome. Our findings indicate that ERβ expression provides independent prognostic information for breast cancers with ERα/PR‐positive status, a feature typical among screen‐detected breast cancers. The role of ERβ needs to be further evaluated especially in this group of breast cancers.