Molecular classification of breast cancer: what the pathologist needs to know

Breast cancer is a heterogeneous disease featuring distinct histological, molecular and clinical phenotypes. Although traditional classification systems utilising clinicopathological and few molecular markers are well established and validated, they remain insufficient to reflect the diverse biological and clinical heterogeneity of breast cancer. Advancements in high-throughput molecular techniques and bioinformatics have contributed to the improved understanding of breast cancer biology, refinement of molecular taxonomies and the development of novel prognostic and predictive molecular assays. Application of such technologies is already underway, and is expected to change the way we manage breast cancer. Despite the enormous amount of work that has been carried out to develop and refine breast cancer molecular prognostic and predictive assays, molecular testing is still in evolution. Pathologists should be aware of the new technology and be ready for the challenge. In this review, we provide an update on the application of molecular techniques with regard to breast cancer diagnosis, prognosis and outcome prediction. The current contribution of emerging technology to our understanding of breast cancer is also highlighted

Clinicopathological significance of ataxia-telangiectasia-mutated (ATM) kinase and ataxia telangiectasia-mutated and Rad3 related (ATR) kinase in MYC overexpressed breast cancers

Purpose: MYC transcription factor has critical roles in cell growth, proliferation, metabolism, differentiation, transformation and angiogenesis. MYC overexpression is seen in about 15% of breast cancers and linked to aggressive phenotypes. MYC overexpression also induces oxidative stress and replication stress in cells. ATM and ATR- mediated signalling is critical for MYC induced DNA damage response. Whether ATM and ATR expression influence clinical outcomes in MYC overexpressed breast cancers is unknown.Methods: We investigated ATM, ATR and MYC at the transcriptional level [Molecular Taxonomy of Breast Cancer International Consortium cohort (n=1950)] and at the protein level in the Nottingham series comprising 1650 breast tumours. We correlated ATM, ATR and MYC expression to clinicopathological features and survival outcomes.Results: In MYC over expressed tumours, high ATR or low ATM levels were associated with aggressive breast cancer features such as higher tumour grade, de-differentiation, pleomorphism, high mitotic index, high risk Nottingham Prognostic Index, triple negative and basal-like breast cancers (all adjusted p values [less than] 0.05). Tumours with low ATM or high ATR levels in conjunction with MYC overexpression also have worse overall breast cancer-specific survival (BCSS) (p value [less than] 0.05).Conclusions: We conclude that ATR/ATM directed stratification and personalisation of therapy may be feasible in MYC overexpressed breast cancer

The prognostic significance of BMI1 expression in invasive breast cancer is dependent on its molecular subtypes

Purpose: BMI-1, which is a major component of the polycomb groupcomplex 1 is an essential epigenetic repressor of multiple regulatory genes and has been identified as a cancer stem cell (CSC) marker in several cancers. However, its role in breast cancer (BC) remains to be defined. In this study, we have evaluated the prognostic significance of BMI-1 among the different molecular subtypes and assessed its association with other breast CSC markers (BCSC).Material and Method: BMI-1 copy number and mRNA was assessed in large and well-characterised cohorts of early-stage BC patients [METABRIC (n=1980) and the Bc-GenExMiner (n=9616) databases]. BMI-1 protein expression was assessed using tissue microarray and immunohistochemistry in a cohort of 870 invasive BC patients with long- term outcome data and the expression of a panel of BCSC markers was monitored.Result: BMI-1 expression, prognostic significance and its association with BCSC markers were differed between molecular classes. In the luminal oestrogen receptor positive (ER+) BC, BMI-1 showed significantly higher expression compared to ER- tumours. BMI-1 showed positive correlation with favourable prognostic features and it was negatively associated with the expression of key BCSC markers (ALDH1A1, CD24, CD44, CD133, SOX10 and SOX9). High expression of BMI-1 was associated with longer breast cancer specific survival (BCSS) independent of other prognostic variables. In the basal triple negative BC subtype, BMI-1 expression showed positive association with CD133 and SOX10 and it was significantly associated with shorter BCSS.Conclusion: High variables and outcome in BC. However, this association is dependent on the molecular subtypes. Further functional assessment to detect its underlying mechanistic roles in BC subtypes is warranted

Retrospective assessment of cyclin‐dependent kinase 5 mRNA and protein expression and its association with patient survival in breast cancer

Cyclin‐dependent kinase 5 (Cdk5) is an atypical member of the cyclin‐dependent kinase family and functions as a serine/threonine kinase that can be activated by non‐cyclin binding activators p35 or p39. Cdk5 expression and activity has been linked with the development and progression of cancer; however, its expression in breast cancer has not been fully described. Protein expression of Cdk5 was determined in a large cohort of early‐stage invasive breast cancer tumours (n = 1110) with long‐term follow‐up data using immunohistochemistry. Expression of CDK5 mRNA was assessed in the METABRIC cohort (n = 1980). Low nuclear and cytoplasmic expression of Cdk5 expression was significantly associated with shorter breast cancer‐specific survival (P = .004 and P = .001, respectively). Importantly, low nuclear and cytoplasmic expression of Cdk5 remained associated with survival in multivariate analysis, including potentially confounding factors (hazard ratio (HR) = 0.612, 95% confidence interval (CI) = 0.418‐0.896, P = .011 and HR = 0.507, 95% CI = 0.318‐0.809, P = .004, respectively). In addition, low nuclear and cytoplasmic expression of Cdk5 was significantly associated with clinicopathological criteria associated with adverse patient prognosis. Low CDK5 mRNA expression was associated with shorter patient survival (P = .005) in the METABRIC cohort; no associations between copy gain or loss and survival were observed. These data suggest that low Cdk5 expression is associated with poor clinical outcome of breast cancer patients and may be of clinical relevance

Chemokine (C-C motif) receptor 7 (CCR7) associates with the tumour immune microenvironment but not progression in invasive breast carcinoma

Some previous studies have reported that the chemokine (C-C motif) receptor 7 (CCR7) plays a role in breast cancer, is associated with lymph node metastasis and drives the site of distant metastasis. However, the impact of its expression on patient outcome and its association with tumour infiltrating inflammatory cells remain to be validated. We evaluated CCR7 protein expression by immunohistochemistry in a large well characterized cohort (n = 866) of early invasive primary breast cancers. CCR7 was expressed in the cytoplasm and membrane of tumour cells. We observed a weak positive association of high CCR7 expression when in either cellular component, but not both together, with axillary lymph node stage 3 tumours (p = 0.043). Logistic regression analysis of lymph node stage revealed no independent predictive value for CCR7 expression. CCR7 expression was higher in HER2 positive tumours (p = 0.03) and associated with positive CD68+ FOXP3+ tumour infiltrating cells. CCR7 staining was negatively associated with CD3+ cells. There was no significant association of CCR7 expression with breast cancer recurrence or survival. We conclude that while CCR7 is not a useful biomarker for predicting lymph node metastasis, it may reflect altered intra- and inter-cellular signalling related to the immune microenvironment. The subcellular localization of CCR7 appears to affect the nature of these interactions

The prognostic significance of ALDH1A1 expression in early invasive breast cancer

Aims: Aldehyde dehydrogenase family 1 member A1 (ALDH1A1)is reportedly a key ALDH isozyme linked to the cancer stem cells (CSC) of many solid tumours, where it is involved in self-renewal, differentiation and self-protection. In this study, the prognostic significance of ALDH1A1 expression in early invasive breast cancer (BC) and its role as a BC stem cell (BCSC) were evaluated.Methods: ALDH1A1 expression was assessed, using immunohistochemistry and tissue microarrays, in a large well- characterised BC cohort. ALDH1A1 mRNA expression was also assessed at the transcriptomic levels, utilising data from the Molecular Taxonomy of Breast Cancer International Consortium. The associations of ALDH1A1 with clinicopathological parameters, other stem cell markers and patient outcomes were determined.Results: ALDH1A1 was expressed in 71% of BC cases, at both the protein and mRNA levels. High ALDH1A1 expression was associated with poor prognostic features, including high grade, poor Nottingham Prognostic Index (NPI), lymph node metastasis and highly proliferative ER+ (luminal B) and triple negative (TNBC) subtypes. ALDH1A1 expression was positively correlated with the expression of CD44, CD24, TWIST, SOX9, EPCAM and CD133. The high immunoexpression of ALDH1A1 was significantly associated with poor BC-specific survival [less than] 0.001), and specifically in the luminal B and TNBC subtypes (P=0.042 and P=0.003, respectively). The immunoexpression of ALDH1A1 was an independent predictor of poor prognosis (P=0.015).Conclusions: ALDH1A1, as assessed using IHC, seems to act as a BCSC marker associated not only with other BCSC markers but also with poor prognostic characteristics and poor outcomes, particularly in the luminal B and TNBC subtypes

The solute carrier SLC7A8 is a marker of favourable prognosis in ER-positive low proliferative invasive breast cancer

Purpose: Breast cancer (BC) is a heterogeneous disease consisting of various subtypes, withdifferent prognostic and therapeutic outcomes. The amino acid transporter, SLC7A8, is over expressed in estrogen receptor positive BC. However the consequences of this overexpression, it terms of disease prognosis, is still obscure. This study aimed to evaluate the biological and prognostic value of SLC7A8 in BC with emphasis on the intrinsic molecular subtypes.Methods: SLC7A8 was assessed at the genomic, using METABRIC data (n=1,980), and proteomic, using immunohistochemistry and TMA (n=1,562), levels in well-characterised primary BC cohorts. SLC7A8 expression was examined with clinicopathological parameters, molecular subtypes, and patient outcome.Results: SLC7A8 mRNA and SLC7A8 protein expression were strongly associated with good prognostic features, including small tumour size, low tumour grade and good Nottingham Prognostic Index (NPI) (all

Atypical ductal hyperplasia: update on diagnosis, management, and molecular landscape

BackgroundAtypical ductal hyperplasia (ADH) is a common diagnosis in the mammographic era and a significant clinical problem with wide variation in diagnosis and treatment. After a diagnosis of ADH on biopsy a proportion are upgraded to carcinoma upon excision; however, the remainder of patients are overtreated. While ADH is considered a non-obligate precursor of invasive carcinoma, the molecular taxonomy remains unknown.Main textAlthough a few studies have revealed some of the key genomic characteristics of ADH, a clear understanding of the molecular changes associated with breast cancer progression has been limited by inadequately powered studies and low resolution methodology. Complicating factors such as family history, and whether the ADH present in a biopsy is an isolated lesion or part of a greater neoplastic process beyond the limited biopsy material, make accurate interpretation of genomic features and their impact on progression to malignancy a challenging task. This article will review the definitions and variable management of the patients diagnosed with ADH as well as the current knowledge of the molecular landscape of ADH and its clonal relationship with ductal carcinoma in situ and invasive carcinoma.ConclusionsMolecular data of ADH remain sparse. Large prospective cohorts of pure ADH with clinical follow-up need to be evaluated at DNA, RNA, and protein levels in order to develop biomarkers of progression to carcinoma to guide management decisions

PPFIA1 expression associates with poor response to endocrine treatment in luminal breast cancer

BackgroundPPFIA1 is an important regulator of cell migration and invasion, regulating focal adhesion signalling and disassembly. PPFIA1 is frequently amplified in breast cancer, and recent functional studies indicate that PPFIA1 is an important promoter of migration and invasion in breast cancer. This study aims to evaluate the utility of PPFIA1 expression in the luminal breast cancer as a prognostic marker to predict the response to endocrine therapy.MethodsLarge, well-characterised cohorts of primary luminal breast cancer patients with long-term follow-up was assessed for the clinical impact of PPFIA1 expression at the transcriptomic and proteomic levels. Prognostic significance of PPFIA1 and its relationship with clinical outcome and benefit of endocrine therapy were analysed. In addition, its association with other related-genes was analysed.ResultsThere was significant association between PPFIA1 expression and a member of the liprin family that involves in cell invasion (PPFIBPI), and the cell cycle regulator (CCND1), whereas a negative association was observed with the tumour suppressor gene (CD82). Patients with high PPFIA1 expression were associated with high risk of recurrence, distant metastasis and death from breast cancer (P< 0.05). Importantly, high PPFIA1 expression predicted relapse in a subset of patients who were subject to endocrine treatment alone, and was an independent prognostic marker of unfavourable outcome in these patients (P< 0.05).ConclusionsThese findings support the proposed role for PPFIA1 as a regulator of cell migration in breast cancer and provides definitive evidence for the clinical utility of PPFIA1 expression in patients with luminal breast cancer. Most importantly, our data suggests that PPFIA1 might be a potential predictive marker for poor benefit from endocrine therapy