Gene-expression molecular subtyping of triple-negative breast cancer tumours: importance of immune response

Abstract

IntroductionTriple-negative breast cancers need to be refined in order to identify therapeutic subgroups of patients.MethodsWe conducted an unsupervised analysis of microarray gene-expression profiles of 107 triple-negative breast cancer patients and undertook robust functional annotation of the molecular entities found by means of numerous approaches including immunohistochemistry and gene-expression signatures. A triple-negative external cohort (n = 87) was used for validation.ResultsFuzzy clustering separated triple-negative tumours into three clusters: C1 (22.4%), C2 (44.9%) and C3 (32.7%). C1 patients were older (mean = 64.6 years) than C2 (mean = 56.8 years; P = 0.03) and C3 patients (mean = 51.9 years; P = 0.0004). Histological grade and Nottingham prognostic index were higher in C2 and C3 than in C1 (P < 0.0001 for both comparisons). Significant event-free survival (P = 0.03) was found according to cluster membership: patients belonging to C3 had a better outcome than patients in C1 (P = 0.01) and C2 (P = 0.02). Event-free survival analysis results were confirmed when our cohort was pooled with the external cohort (n = 194; P = 0.01). Functional annotation showed that 22% of triple-negative patients were not basal-like (C1). C1 was enriched in luminal subtypes and positive androgen receptor (luminal androgen receptor). C2 could be considered as an almost pure basal-like cluster. C3, enriched in basal-like subtypes but to a lesser extent, included 26% of claudin-low subtypes. Dissection of immune response showed that high immune response and low M2-like macrophages were a hallmark of C3, and that these patients had a better event-free survival than C2 patients, characterized by low immune response and high M2-like macrophages: P = 0.02 for our cohort, and P = 0.03 for pooled cohorts.ConclusionsWe identified three subtypes of triple-negative patients: luminal androgen receptor (22%), basal-like with low immune response and high M2-like macrophages (45%), and basal-enriched with high immune response and low M2-like macrophages (33%). We noted out that macrophages and other immune effectors offer a variety of therapeutic targets in breast cancer, and particularly in triple-negative basal-like tumours. Furthermore, we showed that CK5 antibody was better suited than CK5/6 antibody to subtype triple-negative patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-015-0550-y) contains supplementary material, which is available to authorized users.

Basal-like breast cancer: molecular profiles, clinical features and survival outcomes

“…In this section, we further established a consensus on the description of basal-like subgroups (Basal I and Basal II) by comparing our results with other achievements across the literature [10, 19–21, 31], as per the focus of each study. Notably, most of them have centred on the classification of triple-negative entities, a more heterogeneous group than basal-like.…”

“…Recent investigation of TNBCs pointed to the existence of intrinsic basal-like subtypes, with distinct molecular patterns [19–21]. The stratification performed and described by Lehmann et al (2011) [19] revealed the involvement of enriched cell cycle and cell division components in Basal-like 1 (BL1); growth factor signalling, glycolisis and gluconeogenesis pathways in Basal-like 2 (BL2); and immune cell processes in Immunomodulatory (IM).…”

“…The former tumour type is characterised by multiple SOX family transcription factors, while the latter is described by Stat signal transduction molecules and cytokines. More recently, Jézéquel et al (2015) [21] pointed to two other groups: a basal-like with low immune response and high M2-like macrophages, and a basal-enriched with high immune response and low M2-like macrophages. All studies above described have focused on investigating the molecular heterogeneity of TNBCs, partially supporting each other.…”

A review of the importance of immune responses in luminal B breast cancer

“…13 Gene expression studies of BC-adjacent tissues showed that the TNBC microenvironment had increased expression of genes involved in inflammation 14 and revealed further subtypes, some with a low immune response defined by a minimal T cell infiltrate and effector function, and high frequency of suppressive M2-like macrophages, and others with a high immune response and low frequency of M2-like macrophages. 15 These data imply that communication between tumor cells and other cells in cancer-adjacent tissue contributes to BC progression and/or metastasizing potential; the same is likely to be true for Luminal B BC (Fig. 1).…”

“…76 In summary, we suggest that evaluation of markers of immune suppression has prognostic value in luminal B BC. To avoid confounding factors in assessment of the role of the immune system it is vital that the study cohort be carefully selected to minimize variation in Luminal B BC patients' immune systems, e.g., restricted age range 15 and absence of comorbid conditions which may affect immune status. Further, utilization of international standardized criteria for histological analysis is vital for interpretation of the results.…”