Basal-like breast carcinoma: from expression profiling to routine practice

'Why is survival with triple negative breast cancer so low? insights and talking points from preclinical and clinical research'

INTRODUCTION

Triple negative breast cancer is typically related to poor prognosis, early metastasis, and high recurrence rate. Intrinsic and extrinsic biological features of TNBC and resistance mechanisms to conventional therapies can support its aggressive behavior, characterizing TNBC how extremely heterogeneous. Novel combination strategies are under investigation, including immunotherapeutic agents, anti-drug conjugates, PARP inhibitors, and various targeting agents, exploring, in the meanwhile, possible predictive biomarkers to correctly select patients for the optimal treatment for their specific subtype.

AREAS COVERED

This article examines the main malignity characteristics across different subtype, both histological and molecular, and the resistance mechanisms, both primary and acquired, to different drugs explored in the landscape of TNBC treatment, that lead TNBC to still has high mortality rate.

EXPERT OPINION

The complexity of TNBC is not only the main reason of its aggressivity, but its heterogeneity should be exploited in terms of therapeutics opportunities, combining agents with different mechanism of action, after a correct selection by biologic or molecular biomarkers. The main goal is to understand what TNBC really is and to act selectively on its characteristics, with a personalized anticancer treatment.

Disruption of pH Dynamics Suppresses Proliferation and Potentiates Doxorubicin Cytotoxicity in Breast Cancer Cells

The reverse pH gradient is a major feature associated with cancer cell reprogrammed metabolism. This phenotype is supported by increased activity of pH regulators like ATPases, carbonic anhydrases (CAs), monocarboxylate transporters (MCTs) and sodium-proton exchangers (NHEs) that induce an acidic tumor microenvironment, responsible for the cancer acid-resistant phenotype. In this work, we analyzed the expression of these pH regulators and explored their inhibition in breast cancer cells as a strategy to enhance the sensitivity to chemotherapy. Expression of the different pH regulators was evaluated by immunofluorescence and Western blot in two breast cancer cell lines (MDA-MB-231 and MCF-7) and by immunohistochemistry in human breast cancer tissues. Cell viability, migration and invasion were evaluated upon exposure to the pH regulator inhibitors (PRIs) concanamycin-A, cariporide, acetazolamide and cyano-4-hydroxycinnamate. Additionally, PRIs were combined with doxorubicin to analyze the effect of cell pH dynamic disruption on doxorubicin sensitivity. Both cancer cell lines expressed all pH regulators, except for MCT1 and CAXII, only expressed in MCF-7 cells. There was higher plasma membrane expression of the pH regulators in human breast cancer tissues than in normal breast epithelium. Additionally, pH regulator expression was significantly associated with different molecular subtypes of breast cancer. pH regulator inhibition decreased cancer cell aggressiveness, with a higher effect in MDA-MB-231. A synergistic inhibitory effect was observed when PRIs were combined with doxorubicin in the breast cancer cell line viability. Our results support proton dynamic disruption as a breast cancer antitumor strategy and the use of PRIs to boost the activity of conventional therapy.

Androgen receptor expression in a Sri Lankan patient cohort with early breast carcinoma

BACKGROUND

Androgen receptor (AR) expression is emerging as a prognostic biomarker in breast carcinoma (BCa). The study aimed to determine the prevalence of AR expression by immunohistochemical analysis among a cohort of Sri Lankan women with early BCa and to evaluate its association with clinicopathological features including immunohistochemical molecular subtype and early survival.

METHOD

We studied the clinical and pathological features and immunohistochemical profile of 141 women undergoing primary surgery for early BCa, followed by standard adjuvant therapy. AR status was assessed by immunohistochemistry in all cases. Overall survival (OS) and disease-free survival (DFS) was determined. The relationship between AR expression and clinical and pathological parameters and immunohistochemical molecular subtype was analyzed using Student T test and chi-square tests. Cox regression analysis was used to analyze the prognostic impact of AR expression.

RESULTS

AR expression was seen in 40.8%(95%CI 33.10-49.07%) of the BCa study cohort. None of the clinical data studied showed a significant association with the AR status(p > 0.05). Ductal carcinoma in situ(p = 0.003), oestrogen receptor (ER) (p = 0.001) and progesterone receptor (PR) (p = 0.001) positivity and luminal IHC molecular subtype(p = 0.016) were significantly associated with AR-positive status. AR-negative status was significantly associated with tumour necrosis > 50%(p = 0.031), moderate to extensive lymphocytic infiltrate at the tumour margin(p = 0.025) and basal triple negative breast carcinoma(p = 0.016). The mean duration of patient follow-up was 46.70(95% CI 46.495-46.905) months (3.89 years). On univariate analysis, AR-positivity was associated with better OS among ER-positive tumours(p = 0.047), specifically in postmenopausal women (p = 0.030). In ER-negative tumours, AR positivity was associated with worse DFS (p = 0.036). On multivariate analysis, TNM stage and ER/AR status were predictive of survival. ER-positive/AR-positive (ER+/AR+) tumours demonstrated better OS than ER-positive/AR-negative (ER+/AR-) tumours(p = 0.015). ER-negative/AR-positive (ER-/AR+) tumours (p = 0.014) had a worse DFS than ER-negative/AR-negative (ER-/AR-) tumours.

CONCLUSIONS

AR prevalence obtained was low. AR positivity was associated with positivity for ER and PR. On multivariate analysis, apart from TNM stage only ER/AR status were predictive of OS and DFS, with concordant expression of ER/AR demonstrating a better, early survival.

Diverse Roles of Annexin A6 in Triple-Negative Breast Cancer Diagnosis, Prognosis and EGFR-Targeted Therapies

The calcium (Ca2+)-dependent membrane-binding Annexin A6 (AnxA6), is a multifunctional, predominantly intracellular scaffolding protein, now known to play relevant roles in different cancer types through diverse, often cell-type-specific mechanisms. AnxA6 is differentially expressed in various stages/subtypes of several cancers, and its expression in certain tumor cells is also induced by a variety of pharmacological drugs. Together with the secretion of AnxA6 as a component of extracellular vesicles, this suggests that AnxA6 mediates distinct tumor progression patterns via extracellular and/or intracellular activities. Although it lacks enzymatic activity, some of the AnxA6-mediated functions involving membrane, nucleotide and cholesterol binding as well as the scaffolding of specific proteins or multifactorial protein complexes, suggest its potential utility in the diagnosis, prognosis and therapeutic strategies for various cancers. In breast cancer, the low AnxA6 expression levels in the more aggressive basal-like triple-negative breast cancer (TNBC) subtype correlate with its tumor suppressor activity and the poor overall survival of basal-like TNBC patients. In this review, we highlight the potential tumor suppressor function of AnxA6 in TNBC progression and metastasis, the relevance of AnxA6 in the diagnosis and prognosis of several cancers and discuss the concept of therapy-induced expression of AnxA6 as a novel mechanism for acquired resistance of TNBC to tyrosine kinase inhibitors.

Pathology of triple negative breast cancer

Triple negative breast cancer (TNBC) is a subtype of breast tumor lacking hormone receptors expression and HER2 gene amplification and represents 24 % of newly diagnosed breast neoplasms. In this review, pathological aspects of triple-negative breast cancer are illustrated, with particular attention to the seminal studies that defined this subtype of breast cancer by a molecular point of view. This paper also focuses on practical issues raised in clinical routine by the introduction of genetic expression breast cancer profiling and the innovative prognostic and predictive impact on triple-negative breast cancer pathology. Moreover, histopathological aspects of triple-negative neoplasms are also mentioned, underlying the importance of histologic diagnosis of particular cancer subtypes with decisive impact on clinical outcome. Importantly, focus on new therapeutic frontier represented by immunotherapy is illustrated, with particular mention of immune checkpoint inhibitors introduction in TNBC therapy and their impact on future treatments.

Reciprocal expression of Annexin A6 and RasGRF2 discriminates rapidly growing from invasive triple negative breast cancer subsets

Actively growing tumors are often histologically associated with Ki67 positivity, while the detection of invasiveness relies on non-quantitative pathologic evaluation of mostly advanced tumors. We recently reported that reduced expression of the Ca2+-dependent membrane-binding annexin A6 (AnxA6) is associated with increased expression of the Ca2+ activated RasGRF2 (GRF2), and that the expression status of these proteins inversely influence the growth and motility of triple negative breast cancer (TNBC) cells. Here, we establish that the reciprocal expression of AnxA6 and GRF2 is at least in part, dependent on inhibition of non-selective Ca2+ channels in AnxA6-low but not AnxA6-high TNBC cells. Immunohistochemical staining of breast cancer tissues revealed that compared to non-TNBC tumors, TNBC tumors express lower levels of AnxA6 and higher Ki67 expression. GRF2 expression levels strongly correlated with high Ki67 in pretreatment biopsies from patients with residual disease and with residual tumor size following chemotherapy. Elevated AnxA6 expression more reliably identified patients who responded to chemotherapy, while low AnxA6 levels were significantly associated with shorter distant relapse-free survival. Finally, the reciprocal expression of AnxA6 and GRF2 can delineate GRF2-low/AnxA6-high invasive from GRF2-high/AnxA6-low rapidly growing TNBCs. These data suggest that AnxA6 may be a reliable biomarker for distant relapse-free survival and response of TNBC patients to chemotherapy, and that the reciprocal expression of AnxA6 and GRF2 can reliably delineate TNBCs into rapidly growing and invasive subsets which may be more relevant for subset-specific therapeutic interventions.

Clinicopathological, immunohistochemical and molecular correlation of neural crest transcription factor SOX10 expression in triple-negative breast carcinoma

The transcription factor SOX10 mediates the differentiation of neural crest-derived cells, and SOX10 by immunohistochemistry (IHC) is used primarily for the diagnosis of melanoma. SOX10 expression has been previously documented in benign breast myoepithelial cells. However there is limited literature on its expression in triple-negative breast carcinoma (TNBC). The aim was to study the clinical, pathologic and molecular profiles of SOX10+ tumors in TNBC. Tissue microarrays of TNBC were evaluated for SOX10 expression in 48 cases. SOX10 expression was correlated with clinical and pathologic features such as age, grade, and stage. Gene expression was analyzed on RNA extracted from formalin-fixed paraffin-embedded (FFPE) specimens with Affymetrix 2.0 HTA. Co-expression of SOX10 with androgen receptor (AR), WT1, gross cystic disease fluid protein-15 (GCDFP-15), mammaglobin, epidermal growth factor receptor (EGFR), CK5/6 and GATA transcription factor 3 (GATA3) were also assessed. The mean age was 59.38 (range, 28-90 years). Overall, 37.5% cases (18/48) were SOX10+. There was no association between SOX10 expression and age, grade or stage of patients; 6 of 10 (60%) cases of basal-like 1 (BL1), and 5 of 8 cases of unstable (UNS) molecular subtype were SOX10+. One of 5 basal-like-2 (BL2), 1 of 6 immunomodulatory (IM), 1 of 4 mesenchymal (M), 1 of 5 luminal androgen receptor (LAR) and 2 of 8 mesenchymal stem cell (MSL) showed lower frequencies of SOX10 expression. There was negative correlation between SOX10 and AR+ subtypes (P < .002). SOX10 was positively correlated with WT1 (P = .05). SOX10 did not show significant correlation with mammaglobin, GCDFP15, EGFR, CK5/6 and GATA3. SOX10 expression in the basal-like and unstable molecular subtypes supports the concept that these neoplasms show myoepithelial differentiation.

The Association between Molecular Subtypes of Breast Cancer with Histological Grade and Lymph Node Metastases in Indonesian Woman

Objective: Breast carcinoma is a heterogeneous disease which is rich in diversity. Molecular subtypes of breast cancer, histological grade and lymph node metastases are strong prognostic and predictive factors. In Indonesia, only a limited number of studies have investigated the correlation between molecular subtypes with histological grade and lymph node metastases. Methods: We analyzed 247 invasive breast carcinoma cases from the Anatomic Pathology Installation of Dr. Sardjito General Hospital Yogyakarta between 2012-2015. The slides were stained for estrogen receptors (ER), progesterone receptors (PR), HER2, Ki-67 and CK5/6 for classification into breast cancer subtypes (BCS). Histological grade using the Nottingham system and lymph node status were obtained from anatomic pathology records. The association between histological grade and lymph node status with BCS was examined with Chi-square tests. Results: The immunohistochemical features of 247 cases of women with invasive breast carcinoma were examined. There were 102 (41.3%) patients with Luminal A, 34 (13.8%) patients with Luminal B, 48 (19.4%) patients with HER2-positive, and 63 (25.5%) patients with triple negative breast cancer (TNBC). There were 148 (59.9%) patients with negative lymph node status and 99 (40.1%) with positive status. Among 63 TNBC cases, 37 (58.7%) patients were positive for CK5/6 staining (basal-like). Statistically, there were significant differences between histological grade and subtypes (p=0.013). However, no significant differences were found for lymph node metastases (p=0.540). Conclusion: Among subtypes, Luminal A has the highest frequency, followed by TNBC, HER2-positive and Luminal B. Histological grade was associated with molecular subtypes of breast carcinoma in Yogyakarta. Grade I was associated with Luminal A, while Grade III was associated with Luminal B, HER2 and TNBC subtypes.

PTEN PDZ-binding domain suppresses mammary carcinogenesis in the MMTV-PyMT breast cancer model

Phosphatase and tension homolog (PTEN) is a potent tumor suppressor that possesses a PDZ-binding domain (PDZ-BD) at the end of its carboxyl terminus, whose functions during tumorigenesis remains unclear. Here, we crossed a mouse strain with germline deletion of PTEN PDZ-BD with MMTV-PyMT breast cancer model, and found that knockout (KO) mice display normal development of mammary glands, but have both increased breast tumorigenicity and lung metastasis. Orthotopic allograft experiments suggest the loss of PTEN PDZ-BD in breast cancer cells rather than in tumor microenvironment plays a prominent role in increasing tumor burden. Through RNA-sequencing, we observed a significant downregulation of myoepithelial marker genes in both KO primary breast cancer and orthotopic allografts. Moreover, these myoepithelial marker genes are significantly downregulated in human breast cancer tissues, and are associated with poorer clinical prognosis. In addition, several homeobox genes were also identified to be downreguated in KO breast cancer, whose expressions showed significant positive correlation with myoepithelial marker genes. Overall, our findings suggest a novel tumor suppressive role of PTEN PDZ-BD in a murine model of breast cancer, and the mechanism involves the dysregulation of homeobox genes which may result in defective myoepithelial differentiation in breast cancer cells.

Update on Immunohistochemical Analysis in Breast Lesions

CONTEXT

- The utility of immunohistochemistry (IHC) in breast lesions needs to be updated with exceptions among these lesions. Biomarker studies with IHC in triple-negative breast carcinoma may help develop targeted therapies for this aggressive breast cancer. The distinction of metastatic lung adenocarcinoma to the breast and invasive breast carcinoma has significant prognostic and therapeutic implications. The determination can be challenging because both primary tumors can express estrogen receptor and/or HER2 by IHC, creating a diagnostic dilemma.

OBJECTIVES

- To provide a practical update on the use of IHC markers in differential diagnoses in breast lesions, including benign, atypical, precancerous, and malignant tumors; to highlight recently published research findings on novel IHC markers in triple-negative breast carcinoma cases; and to reinforce the importance of IHC use as an ancillary tool in distinguishing metastatic lung adenocarcinoma to the breast from primary breast carcinoma using real case examples.

DATA SOURCES

- PubMed (US National Library of Medicine, Bethesda, Maryland) literature review and authors' research data and personal experiences were used in this review.

CONCLUSIONS

- Immunohistochemistry has an important role in making differential diagnoses in breast lesions in morphologically equivocal settings; recognizing IHC expression status in the exceptions among these lesions will aid in the correct diagnosis of challenging breast cases. Studies suggest that androgen receptor, p16, p53, GATA3, and PELP1 may have potential diagnostic, prognostic, and predictive value in triple-negative breast carcinoma cases; these findings may provide insight and a greater understanding of the tumor biology in triple-negative breast carcinomas. In distinguishing metastatic estrogen receptor-positive or HER2⁺ lung adenocarcinoma to the breast from primary breast carcinoma, napsin A, TTF-1, and GATA3 comprise a useful IHC panel.

Prognostic impact of EGFR and cytokeratin 5/6 immunohistochemical expression in triple-negative breast cancer

Triple-negative breast cancer (TNBC) has an aggressive behavior and limited therapeutic options due to lack of targeted therapy. We aimed in this study to assess the immunohistochemical expression of EGFR and cytokeratin 5/6 and their ability to predict survival and response to neoadjuvant chemotherapy (NAC) among triple-negative breast cancer patients. Thirty-five cases with TNBC were studied by immunohistochemistry for EGFR and CK5/6 expression. Data on overall survival (OS), disease-free survival (DFS) and response to NAC were collected. The resulted data were statistically analyzed. Invasive carcinoma of no special type (NST) was the predominant histopathological type (80%). The commonest histological grade was grade II-III (88.6%). About 57.1% of TNBC cases were CK5/6-positive, and 71.4% were EGFR-positive. EGFR expression showed a significant association with tumor grade and axillary lymph node metastasis (p=0.006, 0.016 respectively). EGFR expression was related to unfavorable response to NAC (p=0.036), poor OS (p=0.002) and poor DFS (p=0.003). CK5/6 expression showed a significant association with tumor grade, unfavorable response to NAC, poor OS & DFS (p=0.007, 0.048, <0.001, 0.043 respectively). Immunohistochemical expression of EGFR and/or CK5/6 showed a high significant association with an unfavorable response to NAC, poor DFS &OS (p=0.010, 0.012, 0.030 respectively).

CONCLUSIONS

EGFR and CK5/6 are adverse prognostic markers in TNBC. EGFR and CK5/6 expression could serve as biomarkers for identifying TNBC patients with poor survival that are unlikely to benefit from neoadjuvant chemotherapy. So, targeted therapy against EGFR may be a hopeful therapy for TNBC with NAC resistance.

Are breast cancer stem cells the key to resolving clinical issues in breast cancer therapy?

Despite the dramatic advances in breast cancer treatment over the past two decades, it is still the most common malignancies in women. One of the reasons patients succumb to breast cancer is treatment resistance leading to metastasis and recurrence. Recently, cancer stem cells (CSCs) have been suggested as a cause of metastasis and recurrence in several cancers because of their unique characteristics, including self-renewal, pluripotency, and high proliferative ability. Increasing evidence has implicated breast cancer stem cells (BCSCs) as essential for tumor development, progression, recurrence, and treatment resistance. BCSCs exhibit resistance to treatment owing to several inter-related factors, including overexpression of ATP-binding cassette (ABC) transporters and increased aldehyde dehydrogenase (ALDH) activity, DNA repair, and reactive oxygen species (ROS) scavenging. In addition, the Notch, Hedgehog, and Wnt signaling pathways have been suggested as the major pathways involved in the self-renewal and differentiation of BCSCs. Despite growing evidence suggesting the importance of BCSCs in progression and metastasis, clear criteria for the identification of BCSCs in clinical practice have yet to be established. Several potential markers have been suggested, including CD44⁺/CD24^-/low, ALDH1, EpCAM/ESA, and nestin; however, there is no standard method to detect BCSCs. Triple-negative breast cancer, which shows initial chemosensitivity, demonstrates worsened prognosis due to therapy resistance, which might be related to the presence of BCSCs. Several clinical trials aimed at the identification of BCSCs or the development of BCSC-targeted therapy are in progress. Determining the clinical relevance of BCSCs may provide clues for overcoming therapy resistance in breast cancer.

Integrated molecular pathway analysis informs a synergistic combination therapy targeting PTEN/PI3K and EGFR pathways for basal-like breast cancer

Background

The basal-like breast cancer (BLBC) subtype is characterized by positive staining for basal mammary epithelial cytokeratin markers, lack of hormone receptor and HER2 expression, and poor prognosis with currently no approved molecularly-targeted therapies. The oncogenic signaling pathways driving basal-like tumorigenesis are not fully elucidated.

Methods

One hundred sixteen unselected breast tumors were subjected to integrated analysis of phosphoinositide 3-kinase (PI3K) pathway related molecular aberrations by immunohistochemistry, mutation analysis, and gene expression profiling. Incidence and relationships between molecular biomarkers were characterized. Findings for select biomarkers were validated in an independent series. Synergistic cell killing in vitro and in vivo tumor therapy was investigated in breast cancer cell lines and mouse xenograft models, respectively.

Results

Sixty-four % of cases had an oncogenic alteration to PIK3CA, PTEN, or INPP4B; when including upstream kinases HER2 and EGFR, 75 % of cases had one or more aberration including 97 % of estrogen receptor (ER)-negative tumors. PTEN-loss was significantly associated to stathmin and EGFR overexpression, positivity for the BLBC markers cytokeratin 5/14, and the BLBC molecular subtype by gene expression profiling, informing a potential therapeutic combination targeting these pathways in BLBC. Combination treatment of BLBC cell lines with the EGFR-inhibitor gefitinib plus the PI3K pathway inhibitor LY294002 was synergistic, and correspondingly, in an in vivo BLBC xenograft mouse model, gefitinib plus PI3K-inhibitor PWT-458 was more effective than either monotherapy and caused tumor regression.

Conclusions

Our study emphasizes the importance of PI3K/PTEN pathway activity in ER-negative and basal-like breast cancer and supports the future clinical evaluation of combining EGFR and PI3K pathway inhibitors for the treatment of BLBC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2609-2) contains supplementary material, which is available to authorized users.

MicroRNA-205 directly targets Krüppel-like factor 12 and is involved in invasion and apoptosis in basal-like breast carcinoma

We investigated microRNAs (miRs) specific to its target gene and exerting distinct biological functions for basal-like breast carcinoma (BLBC). Total RNA was extracted and subjected to miR microarray and bioinformatics analysis. Based on the comprehensive analysis, expression of miRs including its target was analyzed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), western blot analysis and immunohistochemistry (IHC). Further functional analyses were conducted including proliferation, invasion and apoptosis. miR-205 was identified as downregulated (less than 0.5-fold) in BLBC relatively to normal control (NC). Gene ontology (GO) analysis suggested miR-205 may directly targeted Krüppel-like factor 12 (KLF12; degree=4). Luciferase assay revealed miR-205 directly targeted KLF12 through binding its 3'-untranslated region (3'-UTR; p=0.0016). qRT-PCR and western blot analysis showed miR-205 expression was low in cells (p=0.007) and tumor tissues (n=6; p=0.0074), and KLF12 RNA/protein was observed at high levels in cells (p=0.0026; p=0.0079) and tumor tissues (n=9; p=0.0083); knock-up of miR-205 increased its expression (p=0.0021) but reduced KLF12 RNA/protein levels (p=0.0038; p=0.009) in cells. Modulation of miR-205 expression by transfecting its mimics in cells, was involved in invasion (p=0.00175) and apoptosis (p=0.006). In conclusion, our results supported that miR-205 was a miR specific to BLBC which functioned as tumor suppressor gene through directly targeting and negatively regulating proto-oncogene KLF12. miR-205 dysregulation was involved in invasion and apoptosis. miR-205 and KLF12 provided a potential diagnosis biomarker and therapeutic approach for BLBC.

Significantly increased PELP1 protein expression in primary and metastatic triple-negative breast carcinoma: comparison with GATA3 expression and PELP1's potential role in triple-negative breast carcinoma

PELP1 is a novel coregulator of nuclear hormone receptors and is implicated in playing a role in driving breast cancer and enhancing metastatic potential. The PELP1 protein expression and potential role of PELP1 in triple-negative breast carcinoma (TNBC) have not been well characterized. We investigated PELP1 expression by immunohistochemistry in primary and metastatic triple-negative tumors in human tissues and compared its expression with GATA-binding protein 3 (GATA3), a novel diagnostic marker for TNBC. We examined the expression of PELP1 and GATA3 in 70 primary TNBC cases and found that PELP1 had a significantly higher frequency of expression compared to GATA3 (96% versus 46%; P < .0001). The mean extent score of expression of PELP1 was also significantly higher than GATA3's expression (3.87 ± 0.07 versus 0.91 ± 0.15; P < .0001). PELP1 had stronger staining intensity than GATA3. Furthermore, PELP1 immunoreactivity was consistently maintained in paired primary and metastatic TNBC cases (100%). The frequency of PELP1 expression (100%) in metastatic triple-negative tumors was higher than that of GATA3 (40%) in the same tumors (P < .0001). These findings indicate that PELP1 is a much more sensitive marker than GATA3 for TNBCs. PELP1 may have diagnostic utility for metastatic TNBC in appropriate settings, such as history of primary TNBC in cases where the primary is negative for GATA3, mammaglobin, and GCDFP-15. The diffuse and strong nuclear immunoreactivity of PELP1 in most cases suggests that PELP1 may be a molecular target for the treatment of TNBC. We hope that this study will provide insights into the role of PELP1 in TNBC.

Loss of PTEN expression is associated with aggressive behavior and poor prognosis in Middle Eastern triple-negative breast cancer

PTEN is a tumor suppressor that negatively regulates the PI3 K-AKT signaling pathway which is involved in the pathogenesis of many different tumor types and serves as a prognostic marker in breast cancer. However, the significance of the role of PTEN in Middle Eastern ethnic breast cancer has not been explored especially with the fact that breast cancer originating from this ethnic population tend to behave more aggressively than breast cancer in the west. In this study, we analyzed PTEN alteration in a tissue microarray format containing more than 1000 primary breast cancers with clinical follow-up data. Tissue Microarray sections were analyzed for protein expression and copy number change using immunohistochemistry and fluorescence in situ hybridization. Loss of PTEN immunostaining was observed in 77 % of the cases. PTEN loss was significantly associated with large tumor size (p = 0.0030), high grade (p = 0.0281), tumor recurrence (p = 0.0333), and triple-negative breast cancers (p = 0.0086). PTEN loss in triple-negative breast cancers was significantly associated with rapid tumor cell proliferation (p = 0.0396) and poor prognosis (p = 0.0408). PTEN deletion was found only in 60 cases (6.4 %). Loss of PTEN protein expression occurs at high frequency in Middle Eastern breast cancer. PTEN inactivation may potentially lead to an aggressive behavior of tumor cells through stimulation of tumor cell proliferation. Furthermore, PTEN signaling pathway might be used as potential therapeutic target in triple-negative breast cancers since loss of its expression is shown to be significantly associated with this aggressive subtype of breast cancer.

Correlation of clinicopathologic parameters and immunohistochemical features of triple-negative invasive lobular carcinoma

PURPOSE

Invasive lobular carcinoma (ILC) is a subtype of invasive breast carcinoma. With the advent of gene profiling, breast cancer has been classified into luminal A, luminal B, HER2-overexpressing, and triple-negative carcinoma (TNC). Several studies have described TNC (ER, PR, HER2) as a surrogate for basal-like breast carcinoma. However, there is sparse literature on triple-negative lobular carcinoma (TNLC), as most of them show hormone receptor expression. The aim of this study was to investigate the correlation of clinicopathologic parameters of TNLC that has been demonstrated in invasive ductal carcinoma.

MATERIALS AND METHODS

Clinicopathologic parameters and immunohistochemical stains for ER, PR, E-cadherin, HER2, MIB1, and fluorescent in situ hybridization for HER2 of 255 ILC cases were retrieved. In addition, immunohistochemical analysis was performed for p53, c-kit, vimentin, p16, cyclinD1, and BCL2 on 78 cases where 12 were TNC cases and 66 were non-TNC cases.

RESULTS

Of the 255 ILC cases, 218 (85.5%) were classic and 37 (14.5%) were pleomorphic. Seventy-seven (30.1%) cases showed axillary lymph node metastasis. There were 14 of the 255 TNC cases (5.49%) that showed higher incidence in the elderly patients. Six of the 37 (16.21%) cases were pleomorphic and 8 of the 218 (3.7%) cases were classic. Positivity for vimentin was seen in 8 of the 12 cases (67.7%), CK 5 in 3 of the 12 (25%) cases, p16 in 11 of the 12 (91.6%) cases, p53 in 8 of the 12 (66.7%) cases, c-kit in 6 of the 12 (50%) cases, and cyclinD1 in 6 of the 12 cases (50%) indicating basal-like phenotype in 3 cases and nonbasal-like phenotype in 9 cases. There was no statistical significance in lymph node metastasis, tumor recurrence, and distant metastasis between TNC and non-TNC.

CONCLUSIONS

TNLC showed distinct clinicopathologic features such as more frequently seen in the elderly, pleomorphic, larger tumor size, increased expression of vimentin, CK 5, p16, p53, and c-kit. Not all cases showed basal-like phenotype. TNLC is less frequently seen as compared with TNC in invasive ductal carcinoma.

Correlation of CK5 and EGFR with Clinicopathological Profile of Triple-Negative Breast Cancer

Purpose. Triple-negative breast cancer (TNBC) is defined by the loss of expression of ER, PR, and Her2neu expressions. The aim of this study was to examine the expression of the EGFR, CK5, and Ki-67 among triple-negative breast cancer cases and to correlate the expression of the basal markers with the clinicopathological prognostic parameters. Materials and Methods. Thirty-six female patients with TNBC based on ER, PR, and the HER2neu negativities were studied by immunohistochemistry for EGFR, CK5, and Ki-67 expression. Statistical analysis was done using the SPSS software version 20. Results. The mean and median ages were 45.18 years and 46.70 years, respectively. Infiltrating ductal carcinoma NOS was the predominant histopathological type (29/36 [80.6%]). The commonest histological grade was grade 2 (17/36 [47.2%]). Tumour necrosis was seen in 16/36 (44.4%) patients. Infiltrative margins were shown in 69.44% (25/36) cases. Ki-67 was positive in 80.56% (29/36) cases, 61.11% (22/36) were CK5-positive, and 86.11% (31/36) were EGFR-positive. The only significant positive association observed was between the CK5 and histological grade (P < 0.05). Conclusion. CK5 shows a statistically significantly correlation with TNBC histological grade. The majority of the specimens show EGFR expression. Therefore TNBCs could potentially benefit from EGFR-targeted therapeutic strategies.

Significance of rat mammary tumors for human risk assessment

We have previously indicated that the ideal animal tumor model should mimic the human disease. This means that the investigator should be able to ascertain the influence of host factors on the initiation of tumorigenesis, mimic the susceptibility of tumor response based on age and reproductive history, and determine the response of the tumors induced to chemotherapy. The utilization of experimental models of mammary carcinogenesis in risk assessment requires that the influence of ovarian, pituitary, and placental hormones, among others, as well as overall reproductive events are taken into consideration, since they are important modifiers of the susceptibility of the organ to neoplastic development. Several species, such as rodents, dogs, cats, and monkeys, have been evaluated for these purposes; however, none of them fulfills all the criteria specified previously. Rodents, however, are the most widely used models; therefore, this work will concentrate on discussing the rat rodent model of mammary carcinogenesis.

Cellular heterogeneity profiling by hyaluronan probes reveals an invasive but slow-growing breast tumor subset

Tumor heterogeneity confounds cancer diagnosis and the outcome of therapy, necessitating analysis of tumor cell subsets within the tumor mass. Elevated expression of hyaluronan (HA) and HA receptors, receptor for HA-mediated motility (RHAMM)/HA-mediated motility receptor and cluster designation 44 (CD44), in breast tumors correlates with poor outcome. We hypothesized that a probe for detecting HA-HA receptor interactions may reveal breast cancer (BCa) cell heterogeneity relevant to tumor progression. A fluorescent HA (F-HA) probe containing a mixture of polymer sizes typical of tumor microenvironments (10-480 kDa), multiplexed profiling, and flow cytometry were used to monitor HA binding to BCa cell lines of different molecular subtypes. Formulae were developed to quantify binding heterogeneity and to measure invasion in vivo. Two subsets exhibiting differential binding (HA(-/low) vs. HA(high)) were isolated and characterized for morphology, growth, and invasion in culture and as xenografts in vivo. F-HA-binding amounts and degree of heterogeneity varied with BCa subtype, were highest in the malignant basal-like cell lines, and decreased upon reversion to a nonmalignant phenotype. Binding amounts correlated with CD44 and RHAMM displayed but binding heterogeneity appeared to arise from a differential ability of HA receptor-positive subpopulations to interact with F-HA. HA(high) subpopulations exhibited significantly higher local invasion and lung micrometastases but, unexpectedly, lower proliferation than either unsorted parental cells or the HA(-/low) subpopulation. Querying F-HA binding to aggressive tumor cells reveals a previously undetected form of heterogeneity that predicts invasive/metastatic behavior and that may aid both early identification of cancer patients susceptible to metastasis, and detection/therapy of invasive BCa subpopulations.

Roles of p53 and p16 in triple-negative breast cancer

SUMMARY p53 and p16 are both tumor suppressors. This article summarizes the current investigation status on their roles and interaction in triple-negative breast cancer (TNBC) to explore their potential as prognostic, predictive and therapeutic targets. There is significant evidence implicating that p53 mutation as a driver plays an important role in tumorigenesis and progression of TNBC. p53 mutations are more frequently observed in TNBCs compared with ER-positive breast cancers. The presence of a p53 mutation is associated with poorer prognosis in TNBC patients. The status of p53 protein expression divides TNBCs into two biologically distinct subgroups (p53-positive vs p53-negative); p53-positive tumors have more aggressive behavior. p53 has clinical prognostic utility and is a promising target candidate for directed therapy for TNBC patients. p16 appears to play a significant role in tumorigenesis of TNBC through the Rb/p16 dysfunction pathway. A high level of p16 protein expression is associated with aggressive behavior and tumor proliferation of TNBC. The status of p16 expression may have potential predictive value for TNBC response to chemotherapy; further investigation is needed to support the proposal. p16 expression has been strongly correlated with p53 expression in TNBC, suggesting interactions between the two mutations in tumorigenesis. It has been proposed that the two tumor suppressors appear to be involved in early events of TNBC formation with subsequent interplay resulting in their mutual inactivation and, ultimately, leading to a proliferative environment.

High-risk human papillomavirus (HPV) DNA sequences in metaplastic breast carcinomas of Mexican women

BACKGROUND

Metaplastic carcinoma, an uncommon subtype of breast cancer, is part of the spectrum of basal-like, triple receptor-negative breast carcinomas. The present study examined 20 surgical specimens of metaplastic breast carcinomas, for the presence of high-risk Human papillomavirus (HPV), which is suspected to be a potential carcinogenic agent for breast carcinoma.

METHODS

Mastectomy specimens from patients harboring metaplastic breast carcinoma, as defined by the World Health Organization (WHO), and who attended the Instituto Nacional de Cancerologia in Mexico City, were retrieved from the files of the Department of Pathology accumulated during a 16-year period (1995-2008). Demographic and clinical information was obtained from patients' medical records. DNA was extracted from formalin-fixed, paraffin-embedded tumors and HPV type-specific amplification was performed by means of Polymerase chain reaction (PCR). Quantitative Real-time (RT) PCR was conducted in HPV positive cases. Statistically, the association of continuous or categorical variables with HPV status was tested by the Student t, the Chi square, or Fisher's exact tests, as appropriate.

RESULTS

High-risk HPV DNA was detected in eight (40%) of 20 metaplastic breast carcinomas: seven (87.5%) HPV-16 and one (12.5%) HPV-18. Mean age of patients with HPV-positive cases was 49 years (range 24-72 years), the same as for HPV-negative cases (range, 30-73 years). There were not striking differences between HPV + and HPV- metaplastic carcinomas regarding clinical findings. Nearly all cases were negative for estrogen, progesterone and Human epidermal growth factor receptor 2 (HER2), but positive for Epidermal growth factor receptor (EGFR).

CONCLUSIONS

High-risk HPV has been strongly associated with conventional breast carcinomas, although the subtle mechanism of neoplastic transformation is poorly understood. In Mexican patients, the prevalence of HPV infection among metaplastic breast carcinomas is higher than in non-metaplastic ones, as so the HPV viral loads; notwithstanding, HPV viral loads show wide variation and remain even lower than cervical and other non-cervical carcinomas, making it difficult to assume that HPV could play a key role in breast carcinogenesis. Further studies are warranted to elucidate the meaning of the presence of high-risk HPVDNA in breast carcinomas.

Comparison of basal-like triple-negative breast cancer defined by morphology, immunohistochemistry and transcriptional profiles

Basal-like invasive breast cancer is an important clinical group because of its association with a triple-negative phenotype defined by the lack of expression of estrogen, progesterone and human epidermal growth factor receptors 2, relative lack of therapeutic options and poor prognosis. However, depending on the method used to define these lesions, morphological assessment, immunohistochemical markers or gene expression, a different set of tumors is captured. The aim of this study was to investigate the consequences of using different methodological approaches to define basal-like lesions among triple-negative breast carcinomas with regard to their clinicopathological features and patient outcome. The cohort consisted of 142 invasive breast cancers with a triple-negative receptor status. First, each was reviewed histologically and those with morphological basal-like features were characterized as 'Path-Basal'. Second, the 'Core Basal' immunohistochemical lesions, defined as cytokeratin 5/6 and/or epidermal growth factor receptor 1 positive, within the triple-negative breast cancers were identified, and third their classification based on gene expression profiling was retrieved and those in the molecular 'PAM50 basal-like' subtype recorded. A total of 116 basal-like breast cancers were identified among the 142 triple-negative breast cancers by at least one of these three classifications (80%), but only 13 samples were defined as basal-like with all three methods. None of these 13 tumors were associated with lymphovascular invasion. The 34 morphological 'Path-Basal' lesions were significantly associated with a lack of nodal metastases. Comparing the estimates of death in the three classifications, the highest risk of death was seen for the 'Core Basal' group. In this study, we highlight that the definition of basal-like breast cancer based on different methodologies varies significantly and does not identify the same lesions. This incomplete overlap of cases emphasizes the need for consistent or new approaches to improve precise identification.

c-Kit expression as a prognostic molecular marker in patients with basal-like breast cancer

Background

As patients with basal-like breast cancer (BLBC) have a poor prognosis and there is no specifically tailored therapy, molecular biological characterization of BLBC is necessary. c-Kit is a transmembrane receptor tyrosine kinase known to play important roles in various solid cancers. This study classified BLBCs from patients with breast carcinoma, and addressed the significance of c-Kit expression in these tumours.

Methods

Primary breast tumours were stained with antibodies against oestrogen receptor, progesterone receptor, human epidermal growth factor receptor (HER) 2, epidermal growth factor receptor (EGFR), cytokeratin 5/6 and c-Kit. The association between c-Kit, BLBC and survival was analysed.

Results

A total of 667 patients with breast cancer were followed up for a median of 39 (range 6–72) months. Some 190 tumours (28·5 per cent) were classified as triple-negative for breast cancer (negative for oestrogen receptor, progesterone receptor and HER2) and 149 (78·4 per cent) had characteristics of BLBC (positive for cytokeratin 5/6 and/or EGFR). c-Kit expression was detected in 111 (16·6 per cent) of 667 tumours. c-Kit-positive tumours were more commonly found among patients with BLBC (42 of 149, 28·2 per cent; P &lt; 0·001) and in patients with nodal metastasis (47 of 216, 21·8 per cent; P = 0·014) than in those without. In patients with BLBC, the prognosis was significantly worse in those with c-Kit expression (P &lt; 0·001). Multivariable logistic regression analysis revealed c-Kit as an independent negative prognostic factor for cancer-specific survival in patients with BLBC (hazard ratio 2·29, 95 per cent confidence interval 1·11 to 4·72).

Conclusion

c-Kit might be a prognostic marker and possible molecular target for therapy in patients with BLBC.

SOX9 regulates low density lipoprotein receptor-related protein 6 (LRP6) and T-cell factor 4 (TCF4) expression and Wnt/β-catenin activation in breast cancer

Gene expression profiling has identified breast cancer (BCa) subtypes, including an aggressive basal-like (BL) subtype. The molecular signals underlying the behavior observed in BL-BCa group are largely unknown, although recent results indicate a prevalent increase in Wnt/β-catenin activity. Our immunohistochemistry study confirmed that SOX9, one of the BL-BCa signature genes, was expressed by most BL-BCa, and its expression correlated with indicators of poor prognosis. Importantly, BCa gene expression profiling strongly associated SOX9 with the expression of Wnt/β-catenin pathway components, LRP6 and TCF4. In cancer cell lines, SOX9 silencing reduced cell proliferation and invasion, LRP6 and TCF4 transcription, and decreased Wnt/β-catenin activation. SOX9 expression was also increased by Wnt, indicating that SOX9 is at the center of a positive feedback loop that enhances Wnt/β-catenin signaling. Consistently, SOX9 overexpression in BCa cell lines and transgenic SOX9 expression in breast epithelium caused increased LRP6 and TCF4 expression and Wnt/β-catenin activation. These results identify SOX9-mediated Wnt/β-catenin activation as one of the molecular mechanisms underlying aberrant Wnt/β-catenin activity in BCa, especially in the BL-BCa subgroup.

A comprehensive morphological study for basal-like breast carcinomas with comparison to nonbasal-like carcinomas

Background

Breast carcinomas can be classified into five subtypes based on gene expression profiling or immunohistochemical characteristics. Among these subtypes, basal-like breast carcinomas (BLBCs) are one of the most studied group, due to their poor prognosis. The aim of this study was to investigate the prevalance, morphological and immunohistochemical features of BLBCs, in Turkish population.

Methods

Five hundred invasive breast carcinomas were reviewed for several morphological features and immunostained for oestrogen and progesterone receptors, c-ERB-B2, cytokeratin5/6, cytokeratin14, vimentin and epidermal growth factor receptor (EGFR). Basal-like breast carcinoma was defined as a triple negative tumor with cytokeratin5/6 and/or EGFR positive.

Results

The prevalance of BLBC was 9.6%. All medullary carcinomas and 55.6% of metaplastic carcinomas showed basal-like immunophenotype. Patients with BLBC were younger (p=0.04) and had higher-grade tumors (p<0.0001). Morphologic features associated with BLBC included increased mitosis, nuclear pleomorphism, presence of geographic and/or central necrosis, pushing margin of invasion and stromal lymphocytic response (p<0.0001). Presence of prominent nucleoli and vesicular nuclear chromatin were the cytological features correlated with basal-like phenotype (p<0.0001). On multivariate analyses, BLBCs were associated with high mitotic number (p<0.0001), the presence of vesicular chromatin (p=0.004), high tubular grade (p=0.011), lymphocytic response (p=0.031) and the absence of carcinoma insitu (p=0.039). Vimentin was positive in 53.2% of BLBCs, while cytokeratin14 was less frequently expressed (27.7%).

Conclusions

BLBCs have some distinctive, but not pathognomonical, morphological features. Paying attention to these features and adding cytokeratin14 and vimentin to the immunohistochemical panel can help the definitive diagnosis of BLBCs.

Virtual slide

Http://www.diagnosticpathology.diagnomx.eu/vs/5962175467857400

PARP inhibitors--current status and the walk towards early breast cancer

Epithelial carcinomas in general arise as a result of the acquisition of and selection for multiple mutations in a parental somatic cell clone within the tissues of the primary organ of origin. In the last two decades genome caretakers, which function in key areas of DNA damage response, have been recognized as important tumour suppressor genes. Inactivating mutations in these genes occur both as germline and/or somatic mutations with increasing evidence of epigenetic silencing as an additional cause of loss of function. In any event, loss of function in a tumour cell pre-cursor clone leads to accelerated mutation acquisition and underpins the aetiology of the tumour. With increasing understanding of the complex network that is the DNA damage response, signaling pathways already recognized to be central to the establishment of the cancer phenotype are gaining additional roles as controllers of DNA repair. This has relevance to identification of wider populations of patients with tumours susceptible to approaches that target DNA repair deficiency. These have classically been with DNA damaging chemotherapy but the recently developed small molecule inhibitors of DNA repair enzymes such as Poly-ADP polymerases PARP-1 and PARP-2 have been shown to target tumour deficiencies in DNA repair as well sensitizing to DNA damaging therapeutics such as radiation and chemotherapy. Early phase trials with efficacy endpoints have been presented for the PARP inhibitors AG014699, olaparib, veliparib, iniparib and MK4827. The results of the first phase II trials exploring monotherapy PARP inhibitor strategies, which are based on revisiting the concept of synthetic lethality, have emerged and are reviewed herein. The clinical trials that have or are exploring combinations with DNA damaging therapy in these contexts are discussed with particular reference to breast cancer, as are biomarkers that have been proposed and are being investigated to develop optimal drug schedule and patient selection criteria for these DNA repair targeting approaches.

Molecular subtyping of male breast cancer by immunohistochemistry

Molecular subtyping of breast cancer by gene expression has proven its significance in females. Immunohistochemical surrogates have been used for this classification, because gene expression profiling is not yet routinely feasible. Male breast cancer is rare and large series are lacking. In this study, we used immunohistochemistry for molecular subtyping of male breast cancer. A total of 134 cases of male breast cancer were immunohistochemically stained on tissue microarrays for estrogen receptor (ER), progesterone receptor (PR), HER2 and epidermal growth factor receptor (EGFR), as well as for CK5/6, CK14, and Ki67. HER2 was also assessed by chromogen in situ hybridization. Cases were classified as luminal A (ER+ and/or PR+, and HER2- and Ki67 low), luminal B (ER+ and/or PR+, and HER2+ or Ki67 high), HER2 driven (ER-, PR-, HER2+), basal-like (ER-, PR-, HER2-, CK5/6+ and/or CK14+ and/or EGFR+), or unclassifiable triple-negative (negative for all six markers). Luminal type A was by far the most encountered type of male breast cancers, representing 75% of the cases. Luminal type B was seen in 21% and the remaining 4% of cases were classified as basal-like (n=4) and unclassifiable triple-negative (n=1). No HER2 driven cases were identified. Patients with basal-like cancer were significantly younger (P=0.034). Luminal B type cancers showed significantly higher histological grade (P<0.001), mitotic index (P<0.001), and PR negativity (P=0.005) compared with luminal type A cancers. In conclusion, most male breast cancers are luminal A and luminal B types, whereas basal-like, unclassifiable triple-negative, and HER2 driven male breast cancers are rare. Luminal type B seem to represent a subtype with an aggressive phenotype. This distribution of molecular subtypes in male breast cancer is clearly different compared with female breast cancers, pointing to possible important differences in carcinogenesis.

[Modern pathologic diagnostics in breast cancer]

The diagnosis of breast cancer is morphologically based. Pathologic parameters, such as tumor size, lymph node status, and histological grade are well accepted to guide treatment decisions in clinical practice. Estrogen receptor, progesterone receptor and HER2 status are also routinely assessed in today's pathology laboratories to provide further information on predictive and prognostic factors affecting patients' care. Newer molecular techniques, including gene-expression profiling have been widely used to study breast cancer and several molecular prognostic tests already available for clinical use stemmed from these scientific efforts. Authors review prognostically important aspects of the diagnostic pathology and the molecular classification of invasive breast cancer.

Role of epigenetics in cancer health disparities

Cancer disparities in incidence and death rates exist among various racial and ethnic groups. These disparities are thought to be due to socioeconomic status, culture, diet, stress, the environment, and biology. Biological functions, such as epigenetic processes, are affected by all these causal factors and extend throughout the life course. Epigenetic processes, in particular DNA methylation, may play a role in the induction of phenotypes with increased cancer risk due to exposure to these multiple factors. DNA methylation is known to cause changes in gene expression of key regulatory genes in cancer. There are limited studies in which epigenetic changes have been explored to address cancer disparities in various racial and ethnic populations. These few studies have reported significant epigenetic differences in various racial and ethnic groups that could account for the differences seen in tumor initiation, progression, aggressiveness, and outcome of these cancers. Genes differentially methylated among these racially and ethnically diverse populations were involved in important cellular functions, such as tumor growth, tumor suppression, hormone receptors, and genes involved in tumor metastasis. Epigenetic research with the advancement in technology has helped identify biomarkers, therapeutic targets, and understand cancer causation in the general population. Unfortunately, these advances in technology have not been applied to explore the basis for cancer health disparities. More research in epigenetics is needed that will enhance our understanding of the determinants of cancer across various diverse populations and ultimately reduce cancer health disparities.

Triple-negative and basal-like breast cancer: implications for oncologists

Since the start of the 1990s, molecular pathology has been playing an increasingly important role in cancer diagnosis and treatment.[...]

A Comparative Analysis of Biomarker Expression and Molecular Subtypes of Pure Ductal Carcinoma In Situ and Invasive Breast Carcinoma by Image Analysis: Relationship of the Subtypes with Histologic Grade, Ki67, p53 Overexpression, and DNA Ploidy

There is a paucity of data regarding molecular subtypes of pure ductal carcinoma in situ (pDCIS). We evaluated the expression of ER, PR, HER2, Ki67, and p53 and DNA ploidy in 118 pDCIS and 100 invasive breast carcinomas (IBCAs) by routine IHC and classified them according to molecular subtypes. Quantification of biomarkers and DNA ploidy was performed by image analysis. Expression of ER, PR, and high ki67 was more frequent in pDCIS compared to IBCA. High-grade tumors had lower ER and PR expression, high Ki67, overexpression of HER2 and p53, and DNA aneuploidy. Luminal A and HER2 subtypes were more common in pDCIS, and triple negative was more prevalent in IBCA. In both groups, HER2 and triple negative subtypes were characterized by high ki67, overexpression of p53, and DNA aneuploidy compared to luminal subtypes. Molecular subtypes of IBCA are distinct from those of pDCIS. Invasion is characterized by change in phenotype in some tumors.

Molecular pathology of breast cancer: the journey from traditional practice toward embracing the complexity of a molecular classification

CONTEXT

Adenocarcinoma of the breast is the most frequent cancer affecting women in both developed and developing regions of the world. From the moment of clinical presentation until the time of pathologic diagnosis, patients affected by this disease will face daunting questions related to prognosis and treatment options. While improvements in targeted therapies have led to increased patient survival, these same advances have created the imperative to accurately stratify patients to achieve maximum therapeutic efficacy while minimizing side effects. In this evolving era of personalized medicine, there is an ever-increasing need to overcome the limitations of traditional diagnostic practice.

OBJECTIVE

To summarize the molecular diagnostics traditionally used to guide prognostication and treatment of breast carcinomas, to highlight published data on the molecular classification of these tumors, and to showcase molecular assays that will supplement traditional methods of categorizing the disease.

DATA SOURCES

A review of the literature covering the molecular diagnostics of breast carcinomas with a focus on the gene expression and array studies used to characterize the molecular signatures of the disease. Special emphasis is placed on summarizing evolving technologies useful in the diagnosis and characterization of breast carcinoma.

CONCLUSIONS

Available and emerging molecular resources will allow pathologists to provide superior diagnostic, prognostic, and predictive information about individual breast carcinomas. These advances should translate into earlier identification and tailored therapy and should ultimately improve outcome for patients affected by this disease.

Multifocality in "basal-like" breast carcinomas and its influence on lymph node status

BACKGROUND

Basal-like breast carcinomas often are regarded for circumscribed solitary lesions having unfavorable prognosis. On the other hand, a considerable proportion of breast carcinomas is multifocal and has increased metastatic potential. In this study, we analyzed the subgross distribution of the lesions in a series of basal-like carcinomas, compared it with that in nonbasal-like tumors and studied the frequency of vascular invasion and lymph node metastasis in relation to focality of the lesions.

METHODS

A total of 511 consecutive cases documented in large-format histologic sections were studied. Tumors expressing at least one of the basal (myoepithelial) markers (CK5/6, CK14, EGFR) in at least one of the invasive tumor foci were categorized as basal-like tumors. Triple-negative (ER/PR/HER-2-negative) basal-like carcinomas also were analyzed. The distribution of lesions and the frequency of vascular invasion and lymph node metastasis were analyzed. The study was approved by the Regional Ethical Committee Uppsala-Örebro.

RESULTS

In 44% of cases, the invasive component was multifocal or diffuse. Combining the in situ and invasive tumor components resulted in 61% of cases with multifocal/diffuse distribution. The only statistically significant difference observed was that basal-like tumors lacked in situ components more often (21% vs. 9%; P = 0.0075). No significant differences could be demonstrated regarding vascular invasion and lymph node status. Lymph node metastasis appeared significantly more frequently in multifocal cases in both tumor categories.

CONCLUSIONS

Basal-like breast carcinomas are as frequently multifocal as their non-basal-like counterparts; multifocality is associated with increased risk for vascular invasion and lymph node metastasis in both tumor categories.

Selection for EGFR gene amplification in a breast epithelial cell line with basal-like phenotype and hereditary background

An epithelial cell line, referred to as A163, was established from breast carcinoma derived from a patient with a strong family history of breast cancer but no known breast cancer susceptibility mutation. A163 was propagated in a serum-free culture medium including the epidermal growth factor. Immunophenotypic characterization demonstrated a mixed luminal and basal-like phenotype. When epidermal growth factor was excluded from the culture medium, A163 entered a quiescent period followed by a period of increased cell proliferation in a subpopulation of the cells. The epidermal growth factor-independent subpopulation retained the basal-like phenotype of the parental cell line. Karyotype and fluorescent in situ hybridization analysis showed an amplification of epidermal growth factor receptor on 7q in A163-S1 only, resulting in high expression of total and phosphorylated epidermal growth factor receptor. The A163-S1 sub-line piles up in culture, indicating a loss of contact inhibition. When grown on transwell filters, A163 shows basal expression of P63 and cytokeratin 14, whereas A163-S1 expresses P63 ubiquitously, and has lost the basal specific expression of cytokeratin 14, indicating a loss of polarity. Furthermore, when cultured in reconstituted basement membrane matrix, A163 form polarized normal like acini. In contrast, A163-S1 form large disorganized structures with lack of polarity. These cell lines may prove useful to understand molecular changes in breast cancer progression, in particular basal-like breast cancer subtype with bad prognosis and no current treatment options.

Intratumoral expression level of epidermal growth factor receptor and cytokeratin 5/6 is significantly associated with nodal and distant metastases in patients with basal-like triple-negative breast carcinoma

Triple-negative (TN) breast carcinoma, characterized by estrogen receptor, progesterone receptor, and HER2 negativity, is a group of aggressive tumors that can be further classified into 2 subtypes: basal-like, defined as CK5/6 and/or epidermal growth factor receptor (EGFR) positive by immunohistochemistry; and non-basal-like. Clinical characteristics and tumor profiles were analyzed in 105 cases of TN tumors. Among these cases, 35 had distant metastasis, 34 had axillary nodal metastasis only, and 36 were nodal negative. Our results indicate basal-like TN breast tumors with nodal and distant metastases are significantly associated with a higher intratumoral expression of EGFR and CK5/6 compared to those in the nodal negative group. High level of intratumoral EGFR and CK5/6 expression may play a role in development of nodal or distant metastases in patients with basal-like TN tumors and may be predictive of metastatic disease. Furthermore, EGFR targeted therapy may be potentially useful in the treatment of basal-like TN breast cancer.

Molecular morphological approach to the pathological study of development and advancement of human breast cancer

Since the concept of gene profile-based intrinsic subtypes was proposed, various studies on pathological characteristics have been performed. Particularly, triplenegative (TN) breast cancer, which is negative for all hormone receptors [estrogen receptor (ER) and/or progesterone receptor (PgR) and human epidermal growth factor 2 (HER2)], has been attracting attention because effects of endocrine and targeting therapies cannot be anticipated and thus selecting a treatment method is difficult. TN cancer accounts for about 10%-15% of all invasive breast cancer cases in Japanese, which is significantly lower than the incidence reported in the United States. Cytokeratin (CK) 5/6 or epidermal growth factor receptor (EGFR) is positive in 80%, being classified as basal-like carcinoma, but it should be understood that TN breast cancer and basal-like carcinoma are not necessarily the same. Criteria for positivity judgment of ER, PgR, and HER2 were established to select treatment in cases positive for each marker, and greater importance is attached to strict accuracy control. Inversely, the level of negative findings to judge TN varies among the judgment criteria. In any case, the prognosis of TN breast cancer is poor. Pathologically, TN breast cancer shows certain morphological characteristics, such as high grade and a pushing margin, and abnormalities of BRCA1 and p53 are frequently noted. At present, as no effective therapeutic strategy has been established for TN breast cancer, further clarification of the molecular biological characteristics of such cancers is needed. In addition, the incidence of TN-type ductal carcinoma in situ (DCIS) is low, suggesting that TN does not remain preinvasive DCIS for a prolonged period and that it transforms to invasive cancer in an early stage. Because mammary gland basal cells have characters of progenitor or stem cells that differentiate into both luminal epithelium and myoepithelial cells, these cells may be utilized for the differential diagnosis of the benignity or malignancy of intraductal lesions in routine pathological practice. As proliferation markers, such as Ki-67, and multiple gene arrays for gene signature are also utilized to select adjuvant therapy, analysis may progress further in the future.

Classification and prognosis of invasive breast cancer: from morphology to molecular taxonomy

For many years, patient age, axillary lymph node status, tumor size, histological features (especially histological grade and lymphovascular invasion), hormone receptor status, and HER2 status have been the major factors used to categorize patients with breast cancer in order to assess prognosis and determine the appropriate therapy. These factors are most often viewed in combination to group patients into various risk categories. Although these risk categories are useful for assessing prognosis and risk in groups of patients with breast cancer, their role in determining prognosis and evaluating risk in an individual patient is more limited. Therefore, better methods are required to help assess prognosis and determine the most appropriate treatment for patients on an individual basis. Recently, various molecular techniques, particular gene expression profiling, have been increasingly used to help refine breast cancer classification and to assess prognosis and response to therapy. Although the precise role of these newer techniques in the daily management of patients with breast cancer continues to evolve, it is clear that they have the potential to provide value above and beyond that provided by the traditional clinical and pathological prognostic and predictive factors.

Combinatorial biomarker expression in breast cancer

Current clinical management of breast cancer relies on the availability of robust clinicopathological variables and few well-defined biological markers. Recent microarray-based expression profiling studies have emphasised the importance of the molecular portraits of breast cancer and the possibility of classifying breast cancer into biologically and molecularly distinct groups. Subsequent large scale immunohistochemical studies have demonstrated that the added value of studying the molecular biomarker expression in combination rather than individually. Oestrogen (ER) and progesterone (PR) receptors and HER2 are currently used in routine pathological assessment of breast cancer. Additional biomarkers such as proliferation markers and 'basal' markers are likely to be included in the future. A better understanding of the prognostic and predictive value of combinatorial assessment of biomarker expression could lead to improved breast cancer management in routine clinical practice and would add to our knowledge concerning the variation in behaviour and response to therapy. Here, we review the evidence on the value of assessing biomarker expression in breast cancer individually and in combination and its relation to the recent molecular classification of breast cancer.