GIT1 protects against breast cancer growth through negative regulation of Notch.

Hyperactive Notch signalling is frequently observed in breast cancer and correlates with poor prognosis. However, relatively few mutations in the core Notch signalling pathway have been identified in breast cancer, suggesting that as yet unknown mechanisms increase Notch activity. Here we show that increased expression levels of GIT1 correlate with high relapse-free survival in oestrogen receptor-negative (ER(-)) breast cancer patients and that GIT1 mediates negative regulation of Notch. GIT1 knockdown in ER(-) breast tumour cells increased signalling downstream of Notch and activity of aldehyde dehydrogenase, a predictor of poor clinical outcome. GIT1 interacts with the Notch intracellular domain (ICD) and influences signalling by inhibiting the cytoplasm-to-nucleus transport of the Notch ICD. In xenograft experiments, overexpression of GIT1 in ER(-) cells prevented or reduced Notch-driven tumour formation. These results identify GIT1 as a modulator of Notch signalling and a guardian against breast cancer growth.

A prognostic model based on cell-cycle control predicts outcome of breast cancer patients.

BACKGROUND: A prognostic model combining biomarkers of metaphase-anaphase transition of the cell cycle was developed for invasive breast cancer. The prognostic value and clinical applicability of the model was evaluated in comparison with the routine prognosticators of invasive breast carcinoma. METHODS: The study comprised 1135 breast cancer patients with complete clinical data and up to 22-year follow-up. Regulators of metaphase-anaphase transition were detected immunohistochemically and the biomarkers with the strongest prognostic impacts were combined into a prognostic model. The prognostic value of the model was tested and evaluated in separate patient materials originating from two Finnish breast cancer centers. RESULTS: The designed model comprising immunoexpressions of Securin, Separase and Cdk1 identified 8.4-fold increased risk of breast cancer mortality (p < 0.0001). A survival difference exceeding 15 years was observed between the majority (> 75%) of patients resulting with favorable as opposed to unfavorable outcome of the model. Along with nodal status, the model showed independent prognostic impact for all breast carcinomas and for subgroups of luminal, N+ and N- disease. CONCLUSIONS: The impact of the proposed prognostic model in predicting breast cancer survival was comparable to nodal status. However, the model provided additional information in N- breast carcinoma in identifying patients with aggressive course of disease, potentially in need of adjuvant treatments. Concerning N+, in turn, the model could provide evidence for withholding chemotherapy from patients with favorable outcome.

Formin Proteins FHOD1 and INF2 in Triple-Negative Breast Cancer: Association With Basal Markers and Functional Activities.

Basal-like breast cancer is an aggressive form of breast cancer with limited treatment options. The subgroup can be identified immunohistochemically, by lack of hormone receptor expression combined with expression of basal markers such as CK5/6 and/or epidermal growth factor receptor (EGFR). In vitro, several regulators of the actin cytoskeleton are essential for efficient invasion of basal-like breast cancer cell lines. Whether these proteins are expressed in vivo determines the applicability of these findings in clinical settings. The actin-regulating formin protein FHOD1 participates in invasion of the triple-negative breast cancer cell line MDA-MB-231. Here, we measure the expression of FHOD1 protein in clinical triple-negative breast cancers by using immunohistochemistry and further characterize the expression of another formin protein, INF2. We report that basal-like breast cancers frequently overexpress formin proteins FHOD1 and INF2. In cell studies using basal-like breast cancer cell lines, we show that knockdown of FHOD1 or INF2 interferes with very similar processes: maintenance of cell shape, migration, invasion, and proliferation. Inhibition of EGFR, PI3K, or mitogen-activated protein kinase activity does not alter the expression of FHOD1 and INF2 in these cell lines. We conclude that the experimental studies on these formins have implications in the clinical behavior of basal-like breast cancer.

Proliferation-associated miRNAs-494, -205, -21 and -126 detected by in situ hybridization: expression and prognostic potential in breast carcinoma patients.

PURPOSE: To visualize by in situ hybridization (ISH) the levels of a set of proliferation-associated miRNAs and to evaluate their impact and clinical applicability in prognostication of invasive breast carcinoma. METHODS: Tissue specimen from breast carcinoma patients were investigated for miRNAs-494, -205, -21 and -126. Prognostic associations for levels of miRNAs were analyzed based on complete clinical data and up to 22.5-year follow-up of the patient material (n = 285). For detection of the miRNAs, an automated sensitive protocol applying in situ hybridization was developed. RESULTS: MiRNA-494 indicated prognostic value for patients with invasive breast carcinoma. Among node-negative disease reduced level of miRNA-494 predicted 8.5-fold risk of breast cancer death (p = 0.04). Altered levels and expression patterns of the studied miRNAs were observed in breast carcinomas as compared to benign breast tissue. CONCLUSIONS: The present paper reports for the first time on the prognostic value of miRNA-494 in invasive breast cancer. Particularly, detection of miRNA-494 could benefit patients with node-negative breast cancer in identifying subgroups with aggressive disease. Based on our experience, the developed automatic ISH method to visualize altered levels of miRNAs-494, -205, -21 and -126 could be applied to routine pathology diagnostics providing that conditions of tissue treatment, especially fixation delays, are managed.

PTTG1-interacting protein (PTTG1IP/PBF) predicts breast cancer survival.

BACKGROUND: PTTG1-interacting protein (PTTG1IP) is an oncogenic protein, which participates in metaphase-anaphase transition of the cell cycle through activation of securin (PTTG1). PTTG1IP promotes the shift of securin from the cell cytoplasm to the nucleus, allowing the interaction between separase and securin. PTTG1IP overexpression has been previously observed in malignant disease, e.g. in breast carcinoma. However, the prognostic value of PTTG1IP in breast carcinoma patients has not previously been revealed. METHODS: A total of 497 breast carcinoma patients with up to 22-year follow-up were analysed for PTTG1IP and securin immunoexpression. The results were evaluated for correlations with the clinical prognosticators and patient survival. RESULTS: In our material, negative PTTG1IP immunoexpression predicted a 1.5-fold risk of breast cancer death (p = 0.02). However, adding securin immunoexpression to the analysis indicated an even stronger and independent prognostic power in the patient material (HR = 2.5, p < 0.0001). The subcellular location of securin was found with potential prognostic value also among the triple-negative breast carcinomas (n = 96, p = 0.052). CONCLUSIONS: PTTG1IP-negativity alone and in combination with high securin immunoexpression indicates a high risk of breast cancer death, resulting in up to 14-year survival difference in our material.

The Expression of Cohesin Subunit SA2 Predicts Breast Cancer Survival.

Cohesin is one of the main regulators of sister chromatid separation during the metaphase/anaphase transition. It is a multiprotein complex consisting of 4 core subunits, one of those being the SA2 subunit. SA2 plays the final role in dismantling the cohesion complex from the sister chromatids and also functions in DNA double-strand break repair and gene regulation. There is increasing evidence regarding the involvement of both overexpression and underexpression of cohesin in cancer. Here, we present expression patterns of SA2 in different types of human breast tissue, and the prognostic analysis in the material from breast cancer patients with long-term follow-up. SA2 immunoexpression was evaluated in benign, precancerous, and malignant breast tissue, and was classified into low-intensity or high-intensity groups. The DNA content was determined by image cytometry on breast cancer cell imprints. Prognostic analyses were based on 445 breast cancer patients with upto 20 years' follow-up. SA2 immunoexpression was equally high in both benign and precancerous breast tissue. Instead, 72% of the invasive breast cancers showed deficient SA2 expression. These patients were also associated with an unfavorable outcome as indicated by a 1.6-fold risk of breast cancer death (P=0.0208). The majority (75%) of the patients with low SA2 expression were alive 6.0 years after the diagnosis, whereas the majority of the patients with high SA2 expression survived 17.6 years after the diagnosis. No statistically significant association could be detected between SA2 immunoexpression and DNA aneuploidy. Our results and previous literature indicate that decreased SA2 immunoexpression is associated with malignant breast disease and a particularly unfavorable course of disease.