Multiparameter DNA content analysis identifies distinct groups in primary breast cancer.

BACKGROUND: Multiparameter flow cytometry is a robust and reliable method for determining tumour DNA content applicable to formalin-fixed paraffin-embedded (FFPE) tissue. This study examined the clinical and pathological associations of DNA content in primary breast cancer using an improved multiparametric technique. METHODS: The FFPE tissue from 201 primary breast cancers was examined and the cancers categorised according to their DNA content using multiparametric flow cytometry incorporating differential labelling of stromal and tumour cell populations. Mathematical modelling software (ModFit 3.2.1) was used to calculate the DNA index (DI) and percentage S-phase fraction (SPF%) for each tumour. Independent associations with clinical and pathological parameters were sought using backward stepwise Binary Logistic Regression (BLR) and Cox's Regression (CR) analysis. RESULTS: Tumours were grouped into four categories based on the DI of the tumour cell population. Low DI tumours (DI=0.76-1.14) associated with progesterone receptor-positive status (P=0.012, BLR), intermediate DI (DI=1.18-1.79) associated with p53 mutant tumours (P=0.001, BLR), high DI (DI1.80) tumours with human epidermal growth factor receptor 2 (HER2)-positive status (P=0.004, BLR) and 'multiploid tumours' (two or more tumour DNA peaks) did not show any significant associations. Tumours with high SPF% (10%) independently associated with poor overall survival (P=0.027, CR). CONCLUSION: Multiparametric flow analysis of FFPE tissue can accurately assess tumour DNA content. Tumour sub-populations associated with biomarkers of prognosis or likely response to therapy. The alterations in DNA content present the potential for greater understanding of the mechanisms underlying clinically significant biomarker changes in primary breast cancer.

High frequency of complex TP53 mutations in CNS metastases from breast cancer.

BACKGROUND: Brain metastasis from breast cancer is usually associated with a poor prognosis and early death. Alteration of p53 may contribute to malignant progression by abrogation of apoptosis induced by oncogene activation and by acquisition of gain-of-function properties, which promote tumour aggression. Mutation in TP53 occurs at high frequency in carcinomas of the lung and gastro-intestinal tract, but is much less frequent, at 25%, in primary breast cancer. The frequency of TP53 alteration in the central nervous system (CNS) metastatic breast cancer is not known. METHODS: In all, 23 cases of histologically confirmed CNS metastatic breast cancer were identified and the coding sequence of TP53 determined. TP53 was also sequenced in two control series of primary breast carcinomas from independent clinical centres. RESULTS: We demonstrate a strikingly high frequency of TP53 mutation in the CNS metastatic lesions with an over-representation of complex mutations (non-sense/deletions/insertions). Complex mutations occur in metastatic lesions in both triple-negative breast cancer and hormone receptor/HER2-positive cases. Analysis of paired primary carcinomas and brain metastatic lesions revealed evidence for both clonal selection and generation of new mutations (missense and complex) in progression from a primary breast carcinoma to brain metastasis. CONCLUSION: Mutation in TP53 is the most common genetic alteration reported during metastasis to the brain in breast cancer.

Endoglin expression in breast tumor cells suppresses invasion and metastasis and correlates with improved clinical outcome.

Tumor growth factor-ß (TGF-ß) signaling in cancer has been implicated in growth suppression of early lesions and enhancing tumor cell invasion and metastasis. However, the cellular mechanisms that determine this signaling output in individual tumors are still largely unknown. In endothelial cells, TGF-ß signaling is modulated by the TGF-ß co-receptor endoglin (CD105). Here we demonstrate that endoglin is expressed in a subset of invasive breast cancers and cell lines and is subject to epigenetic silencing by gene methylation. Endoglin downregulation in non-tumorigenic MCF10A breast cells leads to the formation of abnormal acini in 3D culture, but does not promote cell migration or transformation. In contrast, in the presence of activated ErbB2, endoglin downregulation in MCF10A cells leads to enhanced invasion into a 3D matrix. Consistent with these data, ectopic expression of endoglin in MDA-MB-231 cells blocks TGF-ß-enhanced cell motility and invasion and reduces lung colonization in an in vivo metastasis model. Unlike endothelial cells, endoglin does not modulate Smad-mediated TGF-ß signaling in breast cells but attenuates the cytoskeletal remodeling to impair cell migration and invasion. Importantly, in a large cohort of invasive breast cancers, lack of endoglin expression in the tumor cell compartment correlates with ENG gene methylation and poor clinical outcome.

The RNA helicase p68 modulates expression and function of the Δ133 isoform(s) of p53, and is inversely associated with Δ133p53 expression in breast cancer.

The RNA helicase p68 is a potent co-activator of p53-dependent transcription in response to DNA damage. Previous independent studies have indicated that p68 and the Δ133p53 isoforms, which modulate the function of full-length p53, are aberrantly expressed in breast cancers. Here we identify a striking inverse association of p68 and Δ133p53 expression in primary breast cancers. Consistent with these findings, small interfering RNA depletion of p68 in cell lines results in a p53-dependant increase of Δ133p53 in response to DNA damage, suggesting that increased Δ133p53 expression could result from downregulation of p68 and provide a potential mechanistic explanation for our observations in breast cancer. Δ133p53α, which has been shown to negatively regulate the function of full-length p53, reciprocally inhibits the ability of p68 to stimulate p53-dependent transcription from the p21 promoter, suggesting that Δ133p53α may be competing with p68 to regulate p53 function. This hypothesis is underscored by our observations that p68 interacts with the C-terminal domain of p53, co-immunoprecipitates 133p53α from cell extracts and interacts only with p53 molecules that are able to form tetramers. These data suggest that p68, p53 and 133p53α may form part of a complex feedback mechanism to regulate the expression of Δ133p53, with consequent modification of p53-mediated transcription, and may modulate the function of p53 in breast and other cancers that harbour wild-type p53.

p53 mutation, deprivation and poor prognosis in primary breast cancer.

BACKGROUND: The deprivation gap for breast cancer survival remains unexplained by stage at presentation, treatment, or co-morbidities. We hypothesised that p53 mutation might contribute to the impaired outcome observed in patients from deprived communities. METHODS: p53 mutation status was determined using the Roche Amplichip research test in 246 women with primary breast cancer attending a single cancer centre and related to deprivation, pathology, overall, and disease-free survival. RESULTS: p53 mutation, identified in 64/246 (26%) of cancers, was most common in 10 out of 17 (58.8%) of the lowest (10th) deprivation decile. Those patients with p53 mutation in the 10th decile had a significantly worse disease-free survival of only 20% at 5 years (Kaplan-Meier logrank chi(2)=6.050, P=0.014) and worse overall survival of 24% at 5 years (Kaplan-Meier logrank chi(2)=6.791, P=0.009) than women of deciles 1-9 with p53 mutation (c.f. 56% and 72%, respectively) or patients in the 10th decile with wild-type p53 (no disease relapse or deaths). CONCLUSION: p53 mutation in breast cancer is associated with socio-economic deprivation and may provide a molecular basis, with therapeutic implications, for the poorer outcome in women from deprived communities.