PI3K pathway activation in breast cancer is associated with the basal-like phenotype and cancer-specific mortality.

Breast cancer is a common malignancy with current biological therapies tailored to steroid hormone (ER, PR) and HER2 receptor status. Understanding the biological basis of resistance to current targeted therapies and the identification of new potential therapeutic targets is an ongoing challenge. The PI3K pathway is altered in a high proportion of breast cancers and may contribute to therapeutic resistance. We undertook an integrative study of mutational, copy number and expression analyses of key regulators of the PI3K pathway in a cohort of 292 invasive breast cancer patients with known treatment outcomes. The alterations identified in this cohort included PIK3CA mutations (12/168, i.e. 7%), PIK3CA copy number gain (28/209, i.e. 14%), PTEN loss (73/258, i.e. 28%) and AKT activation (62/258, i.e. 24%). Overall at least 1 parameter was altered in 72% (139/193) of primary breast cancers. PI3K pathway activation was significantly associated with ER negative (p = 0.0008) and PR negative (p = 0.006) status, high tumor grade (p = 0.032) and a "basal-like" phenotype (p = 0.01), where 92% (25/27) of tumors had an altered pathway. In univariate analysis, PI3K pathway aberrations were associated with death from breast cancer; however, this relationship was not maintained in multivariate analysis. No association was identified between an activated pathway and outcome in tamoxifen- or chemotherapy-treated patients. We concluded that >70% of breast cancers have an alteration in at least 1 component of the PI3K pathway and this might be exploited to therapeutic advantage especially in "basal-like" cancers.

Loss of STARD10 expression identifies a group of poor prognosis breast cancers independent of HER2/Neu and triple negative status.

The phospholipid transfer protein STARD10 cooperates with c-erbB signaling and is overexpressed in Neu/ErbB2 breast cancers. We investigated if STARD10 expression provides additional prognostic information to HER2/neu status in primary breast cancer. A published gene expression dataset was used to determine relationships between STARD10 and HER2 mRNA levels and patient outcome. The central findings were independently validated by immunohistochemistry in a retrospective cohort of 222 patients with breast cancer with a median follow-up of 64 months. Kaplan-Meier and Cox proportional hazards analyses were used for univariate and multivariate analyses. Patients with low STARD10 or high HER2 tumor mRNA levels formed discrete groups each associated with a poor disease-specific survival (p = 0.0001 and p = 0.0058, respectively). In the immunohistochemical study low/absent STARD10 expression i.e. < or = 10% positive cells was observed in 24 of 222 (11%) tumors. In a univariate model, low/absent STARD10 expression was significantly associated with decreased patient survival (p = 0.0008). In multivariate analyses incorporating tumor size, tumor grade, lymph node status, ER, PR and HER2 status, low STARD10 expression was an independent predictor of death from breast cancer (HR: 2.56 (95% CI: 1.27-5.18), p = 0.0086). Furthermore, low/absent STARD10 expression, HER2 amplification and triple negative status were independent prognostic variables. Loss of STARD10 expression may provide an additional marker of poor outcome in breast cancer identifying a subgroup of patients with a particularly adverse prognosis, which is independent of HER2 amplification and the triple negative phenotype.

High Notch1 protein expression is an early event in breast cancer development and is associated with the HER-2 molecular subtype.

AIMS: Activation of Notch signalling results in hyperplasia and tumorigenesis in murine mammary epithelium. However, there is little information regarding the expression of Notch1 in premalignant lesions and early breast cancer. We investigated expression of Notch1 in breast cancer development and its association with molecular subtypes. METHODS AND RESULTS: Immunohistochemical expression of Notch1 was determined in a murine model of mammary carcinogenesis and in breast tissue from two cohorts of breast cancer patients, the first (n=222) comprising a histological progression series and the second an outcome series of 228 patients with operable invasive ductal carcinoma. Enhanced expression of Notch1 protein was an early event in both murine and human breast cancer development with progressive increases in expression with the development of hyperplasia and malignancy. High Notch1 was not prognostic in the outcome cohort. There was, however, a highly significant association of high Notch1 protein with the HER-2 molecular subtype of breast cancer (P=0.008). CONCLUSIONS: These data demonstrate that aberrant Notch regulation is an early event in mammary carcinogenesis and is associated with the HER-2 molecular subtype of breast cancer, and suggest the Notch signalling pathway may be a potential therapeutic target worthy of further investigation.

c-Myc overexpression and endocrine resistance in breast cancer.

The oncoprotein c-Myc is frequently overexpressed in breast cancer and ectopic expression in breast cancer cell lines attenuates responses to antiestrogen treatment. Here, we review preliminary data aimed at further elucidating a potential role for c-Myc in clinical endocrine resistance in breast cancer. Immunohistochemical and semi-quantitative PCR revealed that c-Myc protein and c-myc mRNA were frequently overexpressed in both ER-positive and ER-negative breast carcinoma. Furthermore, both constitutive and inducible c-Myc overexpression in MCF-7 breast cancer cell lines markedly reduced their sensitivity to the growth inhibitory effects of the pure antiestrogen ICI 182,780. In order to identify potential downstream targets of c-Myc that mediate this effect, Affymetrix microarrays were employed to examine the patterns of gene expression shared by MCF-7 cells stimulated by estrogen, or by induction of c-Myc. Approximately 50% of estrogen target genes identified 6h after treatment were also regulated by c-Myc. One novel target, EMU4, was transcriptionally regulated by c-Myc. In addition, there was a strong correlation between c-myc and EMU4 mRNA expression in a battery of breast cancer cell lines. These data confirm that c-Myc overexpression is a common event in breast cancer, and that this is associated with resistance to antiestrogens in vitro. Furthermore, the development of an experimental paradigm for the discovery of c-Myc and estrogen target genes associated with endocrine resistance provides a framework for the discovery and validation of genes involved in estrogen signalling, and c-Myc-mediated-antiestrogen resistance.

Sentinel node micrometastases in breast cancer: clinical outcome.

AIM: The sentinel lymph node biopsy has steadily replaced axillary lymph node dissection for staging clinically node-negative breast cancer. This study assesses surgical and adjuvant practice in relation to micrometastases and isolated tumor cells found on biopsy in a single surgeon cohort. METHODS: Clinicopathological characteristics were collated from 700 breast cancer patients undergoing sentinel lymph node biopsies between 1999 and 2007. The status and details of the node biopsies, continuing treatment and adverse outcomes were reported. Patient details at the time of diagnosis were entered into Adjuvant! online to look at likely prognosis. For both isolated tumor cells and micrometastases, data input was conducted twice, once as node-negative and again as node-positive, thus providing two predicted benefit data series. RESULTS: A total of 665 women were eligible for inclusion, 67 with micrometastases and 20 with isolated tumor cells. Overall 33 patients developed recurrence with nine breast-cancer related deaths. Women with isolated tumor cells or micrometastases were more likely to receive adjuvant radiotherapy to the axilla compared with women with node-negative disease. Compared to those with isolated tumor cells, a higher number of women with micrometastases received systemic chemotherapy despite similar predicted benefits. Individual comparisons showed significantly higher rates of recurrence in women with isolated tumor cells than in node-negative disease (P < 0.0001). CONCLUSION: The biological behavior of early breast cancer with isolated tumor cells on sentinel node biopsy is similar to both micrometastases and macrometastases, i.e. they behave in a node-positive fashion. This is an early indication that these patients should be treated with more aggressive adjuvant therapy.

Cytoplasmic localization of beta-catenin is a marker of poor outcome in breast cancer patients.

Beta-catenin is involved in cell adhesion through catenin-cadherin complexes and as a transcriptional regulator in the Wnt signaling pathway. Its deregulation is important in the genesis of a number of human malignancies, particularly colorectal cancer. A range of studies has been undertaken in breast cancer, with contradictory associations reported among beta-catenin expression, clinicopathologic variables, and disease outcome. We undertook an immunohistochemical study measuring the levels and subcellular localization of beta-catenin in 292 invasive ductal breast cancers with known treatment and outcome. No association with breast cancer-specific death was observed for cytoplasmic or membrane expression alone; however, a continuous score representing both locations (membrane minus cytoplasmic expression: MTC score) was associated with a worse outcome in univariate analysis (P = 0.004), and approached significance in a multivariate analysis model that included lymph node, progesterone receptor (PR), and HER2 status (P = 0.054). Therefore, the MTC score was used for further statistical analyses due to the importance of both the subcellular location and the levels of expression of beta-catenin. An association was identified between high cytoplasmic expression (low MTC score), and high tumor grade (P = 0.004), positive Ki67 (P = 0.005), negative estrogen receptor (ER) (P = 0.005), positive HER2 (P = 0.04) status, and an active phosphoinositide 3-kinase pathway (P = 0.005), measured as PIK3CA mutations (P = 0.05) or PTEN loss (P = 0.05). Low cytoplasmic expression (high MTC score) was associated with the luminal A subtype (P = 0.004). In conclusion, a low beta-catenin MTC score is associated with an adverse outcome in breast cancer, which may be of mechanistic significance in the disease process.