Gene expression profiling of inflammatory breast cancer

Whole-exome profiles of inflammatory breast cancer and pathological response to neoadjuvant chemotherapy

BACKGROUND

Neoadjuvant chemotherapy (NACT) became a standard treatment strategy for patients with inflammatory breast cancer (IBC) because of high disease aggressiveness. However, given the heterogeneity of IBC, no molecular feature reliably predicts the response to chemotherapy. Whole-exome sequencing (WES) of clinical tumor samples provides an opportunity to identify genomic alterations associated with chemosensitivity.

METHODS

We retrospectively applied WES to 44 untreated IBC primary tumor samples and matched normal DNA. The pathological response to NACT, assessed on operative specimen, distinguished the patients with versus without pathological complete response (pCR versus no-pCR respectively). We compared the mutational profiles, spectra and signatures, pathway mutations, copy number alterations (CNAs), HRD, and heterogeneity scores between pCR versus no-pCR patients.

RESULTS

The TMB, HRD, and mutational spectra were not different between the complete (N = 13) versus non-complete (N = 31) responders. The two most frequently mutated genes were TP53 and PIK3CA. They were more frequently mutated in the complete responders, but the difference was not significant. Only two genes, NLRP3 and SLC9B1, were significantly more frequently mutated in the complete responders (23% vs. 0%). By contrast, several biological pathways involved in protein translation, PI3K pathway, and signal transduction showed significantly higher mutation frequency in the patients with pCR. We observed a higher abundance of COSMIC signature 7 (due to ultraviolet light exposure) in tumors from complete responders. The comparison of CNAs of the 3808 genes included in the GISTIC regions between both patients' groups identified 234 genes as differentially altered. The CIN signatures were not differentially represented between the complete versus non-complete responders. Based on the H-index, the patients with heterogeneous tumors displayed a lower pCR rate (11%) than those with less heterogeneous tumors (35%).

CONCLUSIONS

This is the first study aiming at identifying correlations between the WES data of IBC samples and the achievement of pCR to NACT. Our results, obtained in this 44-sample series, suggest a few subtle genomic alterations associated with pathological response. Additional investigations are required in larger series.

Mutational landscape of inflammatory breast cancer

BACKGROUND

Inflammatory breast cancer (IBC) is the most pro-metastatic form of BC. Better understanding of its enigmatic pathophysiology is crucial. We report here the largest whole-exome sequencing (WES) study of clinical IBC samples.

METHODS

We retrospectively applied WES to 54 untreated IBC primary tumor samples and matched normal DNA. The comparator samples were 102 stage-matched non-IBC samples from TCGA. We compared the somatic mutational profiles, spectra and signatures, copy number alterations (CNAs), HRD and heterogeneity scores, and frequencies of actionable genomic alterations (AGAs) between IBCs and non-IBCs. The comparisons were adjusted for the molecular subtypes.

RESULTS

The number of somatic mutations, TMB, and mutational spectra were not different between IBCs and non-IBCs, and no gene was differentially mutated or showed differential frequency of CNAs. Among the COSMIC signatures, only the age-related signature was more frequent in non-IBCs than in IBCs. We also identified in IBCs two new mutational signatures not associated with any environmental exposure, one of them having been previously related to HIF pathway activation. Overall, the HRD score was not different between both groups, but was higher in TN IBCs than TN non-IBCs. IBCs were less frequently classified as heterogeneous according to heterogeneity H-index than non-IBCs (21% vs 33%), and clonal mutations were more frequent and subclonal mutations less frequent in IBCs. More than 50% of patients with IBC harbored at least one high-level of evidence (LOE) AGA (OncoKB LOE 1-2, ESCAT LOE I-II), similarly to patients with non-IBC.

CONCLUSIONS

We provide the largest mutational landscape of IBC. Only a few subtle differences were identified with non-IBCs. The most clinically relevant one was the higher HRD score in TN IBCs than in TN non-IBCs, whereas the most intriguing one was the smaller intratumor heterogeneity of IBCs.

JAK-STAT Signaling in Inflammatory Breast Cancer Enables Chemotherapy-Resistant Cell States

Inflammatory breast cancer (IBC) is a difficult-to-treat disease with poor clinical outcomes due to high risk of metastasis and resistance to treatment. In breast cancer, CD44+CD24- cells possess stem cell-like features and contribute to disease progression, and we previously described a CD44+CD24-pSTAT3+ breast cancer cell subpopulation that is dependent on JAK2/STAT3 signaling. Here we report that CD44+CD24- cells are the most frequent cell type in IBC and are commonly pSTAT3+. Combination of JAK2/STAT3 inhibition with paclitaxel decreased IBC xenograft growth more than either agent alone. IBC cell lines resistant to paclitaxel and doxorubicin were developed and characterized to mimic therapeutic resistance in patients. Multi-omic profiling of parental and resistant cells revealed enrichment of genes associated with lineage identity and inflammation in chemotherapy-resistant derivatives. Integrated pSTAT3 chromatin immunoprecipitation sequencing and RNA sequencing (RNA-seq) analyses showed pSTAT3 regulates genes related to inflammation and epithelial-to-mesenchymal transition (EMT) in resistant cells, as well as PDE4A, a cAMP-specific phosphodiesterase. Metabolomic characterization identified elevated cAMP signaling and CREB as a candidate therapeutic target in IBC. Investigation of cellular dynamics and heterogeneity at the single cell level during chemotherapy and acquired resistance by CyTOF and single cell RNA-seq identified mechanisms of resistance including a shift from luminal to basal/mesenchymal cell states through selection for rare preexisting subpopulations or an acquired change. Finally, combination treatment with paclitaxel and JAK2/STAT3 inhibition prevented the emergence of the mesenchymal chemo-resistant subpopulation. These results provide mechanistic rational for combination of chemotherapy with inhibition of JAK2/STAT3 signaling as a more effective therapeutic strategy in IBC.

SIGNIFICANCE

Chemotherapy resistance in inflammatory breast cancer is driven by the JAK2/STAT3 pathway, in part via cAMP/PKA signaling and a cell state switch, which can be overcome using paclitaxel combined with JAK2 inhibitors.

Genetic Variants and Tumor Immune Microenvironment: Clues for Targeted Therapies in Inflammatory Breast Cancer (IBC)

To better understand the etiology of inflammatory breast cancer (IBC) and identify potential therapies, we studied genomic alterations in IBC patients. Targeted, next-generation sequencing (NGS) was performed on cell-free DNA (cfDNA) (n = 33) and paired DNA from tumor tissues (n = 29) from 32 IBC patients. We confirmed complementarity between cfDNA and tumor tissue genetic profiles. We found a high incidence of germline variants in IBC patients that could be associated with an increased risk of developing the disease. Furthermore, 31% of IBC patients showed deficiencies in the homologous recombination repair (HRR) pathway (BRCA1, BRCA2, PALB2, RAD51C, ATM, BARD1) making them sensitive to poly (ADP-ribose) polymerase (PARP) inhibitors. We also characterized the tumor-infiltrating lymphocytes (TILs) in tumor tissue biopsies by studying several markers (CD4, CD8, FoxP3, CD20, PD-1, and PD-L1) through immunohistochemistry (IHC) staining. In 7 of 24 (29%) patients, tumor biopsies were positive for PD-L1 and PD-1 expression on TILs, making them sensitive to PD-1/PD-L1 blocking therapies. Our results provide a rationale for considering PARP inhibitors and PD-1/PDL1 blocking immunotherapy in qualifying IBC patients.

Inflammatory Breast Cancer at the Extremes of Age

BACKGROUND

Inflammatory breast cancer (IBC) is a rare breast malignancy with poor outcomes compared with non-IBC. Age-related differences in tumor biology, treatment, and clinical outcomes have been described in non-IBC. This study evaluated age-related differences in IBC.

METHODS

From an institutional prospective database, patients with an IBC diagnosed from 2010 to 2019 were identified. Age was categorized as 40 years or younger, 41 to 64 years, and 65 years or older. Demographics, clinicopathologic features, and treatment received were compared. Recurrence and survival outcomes were analyzed using the log-rank test and the Cox proportional hazards model.

RESULTS

Of 523 IBC patients, 113 (21.6%) were age 40 years or younger, and 72 (13.8%) were age 65 years or older. The groups did not differ statistically by race/ethnicity, N stage, clinical stage, or tumor subtype. The younger patients included a higher proportion of Hispanic and Asian patients, triple-negative breast cancer (TNBC), and clinical N2/N3. Trimodality therapy was received by 92% of the stage 3 patients, with no difference in pathologic complete response (pCR) by age (23.3% vs 28.6%; p = 0.46). During a median follow-up period of 40 months, 17% of the patients experienced locoregional recurrence and 42.8% had distant metastasis. No difference in 3-year recurrence-free survival (57.9% vs 42.6% vs 54%; p = 0.42, log rank) or overall survival (OS) (75.6% vs 77.1% vs 64.4%; p = 0.31, log rank) by age was observed, and no difference in OS by age in de novo stage 4 disease was observed. In the multivariate analysis, worse OS was associated with TNBC (hazard ratio [HR], 1.99, 95% confidence interval [CI], 1.31-3.05) and no pCR (HR, 4.45; 95% CI, 2.16-9.18).

CONCLUSION

No significant differences were observed in demographics, treatment patterns, or clinical outcomes for IBC patients age 40 years or younger compared with those age 65 years or older treated by a specialized multidisciplinary team. These findings do not support age-related treatment de-escalation in IBC.

C/EBPβ/AEP Signaling Regulates the Oxidative Stress in Malignant Cancers, Stimulating the Metastasis

Solid tumors start as a local disease, but some are capable of metastasizing to the lymph nodes and distant organs. The hypoxic microenvironment, which is critical during cancer development, plays a key role in regulating cancer progression and metastasis. However, the molecular mechanisms mediating the disseminated cancer cell metastasis remain incompletely understood. Here, we show that C/EBPβ/AEP signaling that is upregulated in breast cancers mediates oxidative stress and lung metastasis, and inactivation of asparagine endopeptidase (AEP, also known as legumain) robustly regulates breast cancer reactive oxygen species (ROS) and metastasis. AEP, a protease activated in acidic conditions, is overexpressed in numerous types of cancer and promotes metastasis. Employing a breast cancer cell line MDA-MD-231, we show that C/EBPβ, an oxidative stress or inflammation-activated transcription factor, and its downstream target AEP mediate ROS production as well as migration and invasion in cancer cells. Deficiency of AEP in the MMTV-PyMT transgenic breast cancer mouse model significantly regulates oxidative stress and suppresses lung metastasis. Administration of an innovative AEP inhibitor substantially mitigates ROS production and cancer metastasis. Hence, our study demonstrates that pharmacologic inhibition of AEP activity might provide a disease-modifying strategy to suppress cancer metastasis.

Identification of a Positive Association between Mammary Adipose Cholesterol Content and Indicators of Breast Cancer Aggressiveness in a French Population

BACKGROUND

Several studies have recently highlighted important roles for adipose tissue in cancer. However, few have examined adipose tissue cholesterol, and no study has been performed in breast adipose tissue associated with breast tumors.

OBJECTIVES

The present work was designed to determine if breast adipose tissue cholesterol from the tumor-surrounding area is associated with breast cancer aggressiveness.

METHODS

Between 2009 and 2011, 215 breast adipose tissue samples were collected at the Tours University Hospital (France) during surgery of women (aged 28-89 y) with invasive breast cancer. Associations of free cholesterol (FC), esterified cholesterol (EC), and total cholesterol (TC) amounts with clinical variables (age, BMI, and treated or untreated hypercholesterolemia) and tumor aggressiveness parameters [phenotype, grade, presence of inflammatory breast cancer (IBC), and multifocality] were tested using Student's t test and after ANOVA.

RESULTS

The predominant form of cholesterol in adipose tissue was FC, and 50% of patients had no detectable EC. The adipose tissue FC content (μg/mg total lipid) was 18% greater in patients >70 y old than in those 40-49 y old (P < 0.05) and the TC content tended to be 12% greater in untreated hypercholesterolemic patients than in normocholesterolemic patients (P = 0.06). Breast adipose cholesterol concentrations were increased in tissues obtained from patients with human-epidermal-growth-factor-receptor-2 (HER2) phenotype (+13% FC; P < 0.05 compared with luminal A), IBC (+15% FC; P = 0.06 compared with noninflammatory tumors), as well as with multifocal triple-negative tumors (+34% FC, P < 0.05; +30% TC, P < 0.05, compared with unifocal triple-negative tumors). Among patients with triple-negative tumors, hypercholesterolemia was significantly more common (P < 0.05) in patients with multifocal tumors (64%) than in patients with unifocal tumors (25%).

CONCLUSIONS

This study is the first of this magnitude that analyzes cholesterol concentrations in adipose tissue from female breast cancer patients. An increase in breast adipose tissue cholesterol content may contribute to breast cancer aggressiveness (HER2 phenotype, multifocality of triple-negative tumors, and IBC).

MicroRNAs Involved in Inflammatory Breast Cancer: Oncogene and Tumor Suppressors with Possible Targets

Inflammatory breast cancer (IBC) as a rare and highly aggressive type of breast cancer displays phenotypic characteristics. To date, the IBC-associated molecular mechanisms are entirely unknown. In addition, there is an urgent need to identify the new biomarkers involved in the diagnosis and therapeutic purposes of IBC. MicroRNAs, a category of short noncoding RNAs, are capable of controlling the post-transcriptional expression of genes and thus can act as diagnostic predictive tools. In this review, we addressed the status of oncogenic and tumor suppressor miRNA-mediated IBC in current studies. Furthermore, based on their targets, their involvement in cancer progression, angiogenesis, metastasis, and apoptosis were determined.

Immune phenotype of patients with stage IV metastatic inflammatory breast cancer

Background

Inflammatory breast cancer (IBC) is a rare but aggressive carcinoma characterized by severe erythema and edema of the breast, with many patients presenting in advanced metastatic disease. The “inflammatory” nature is not due to classic immune-mediated inflammation, but instead results from tumor-mediated blockage of dermal lymphatic ducts. Previous work has shown that expression of PD-L1 on tumor cells can suppress T cell activation in triple-negative (TN) non-IBC breast cancer. In the present work, we investigated immune parameters in peripheral blood of metastatic IBC patients to determine whether cellular components of the immune system are altered, thereby contributing to pathogenesis of the disease. These immune parameters were also compared to PD-1 and PD-L1 expression in IBC tumor biopsies.

Methods

Flow cytometry-based immune phenotyping was performed using fresh peripheral blood from 14 stage IV IBC patients and compared to 11 healthy age-similar control women. Immunohistochemistry for CD20, CD3, PD-1, and PD-L1 was performed on tumor biopsies of these metastatic IBC patients.

Results

IBC patients with Stage IV disease had lymphopenia with significant reductions in circulating T, B, and NK cells. Reductions were observed in all subsets of CD4⁺ T cells, whereas reductions in CD8⁺ T cells were more concentrated in memory subsets. Immature cytokine-producing CD56^bright NK cells expressed higher levels of FcγRIIIa and cytolytic granule components, suggesting accelerated maturation to cytolytic CD56^dim cells. Immunohistochemical analysis of tumor biopsies demonstrated moderate to high expression of PD-1 in 18.2% of patients and of PD-L1 in 36.4% of patients. Interestingly, a positive correlation was observed between co-expression levels of PD-L1 and PD-1 in tumor biopsies, and higher expression of PD-L1 in tumor biopsies correlated with higher expression of cytolytic granule components in blood CD4⁺ T cells and CD56^dim NK cells, and higher numbers of CD8⁺ effector memory T cells in peripheral blood. PD-1 expression in tumor also correlated with increased infiltration of CD20⁺ B cells in the tumor.

Conclusions

Our results suggest that while lymphocyte populations are severely compromised in stage IV IBC patients, an immune response toward the tumor had occurred in some patients, providing biological rationale to evaluate PD-1/PD-L1 immunotherapies for IBC.

Supplementary information

The online version contains supplementary material available at 10.1186/s13058-020-01371-x.

MARCKS protein overexpression is associated with poor prognosis in male breast cancer

BACKGROUND

Male breast cancer (MBC) is a rare and aggressive disease. Thus, identification of new therapeutic targets is crucial.

OBJECTIVE

Our objective was to evaluate the protein expression of MARCKS (Myristoylated Alanine-Rich C-Kinase Substrate) in MBC and to investigate its prognostic value.

MATERIALS AND METHODS

MARCKS protein expression in tumor and stromal cells was analyzed by immunohistochemistry (IHC) in a retrospective series of 96 pre-chemotherapy MBC samples and 80 normal breast samples, from Tunisian patients treated at Salah Azaiez Institute. Correlations were searched between MARCKS expression and clinicopathological features including overall survival (OS).

RESULTS

MARCKS was overexpressed in epithelial tumor cells in 66% of the MBC samples versus 26% of normal samples (p= 1.40 × 10-7). Such positive MARCKS expression in epithelial tumor cells was associated with positive HER2 status (p= 4.0 × 10-3). It was associated with shorter OS in uni-and multivariate analysis. By contrast, stromal IHC MARCKS expression was correlated only with tumor grade.

CONCLUSION

MARCKS tumor cell overexpression might in part explain the aggressiveness and the poor prognosis of MBC. MARCKS can represent a potential therapeutic target for MBC.

Expression signatures and roles of microRNAs in inflammatory breast cancer

Inflammatory breast cancer (IBC) is an infrequent but aggressive manifestation of breast cancer, which accounts for 2-4% of all breast cancer cases but responsible for 7-10% of breast cancer-related deaths, and with a 20-30% 10-year overall survival compared with 80% for patients with non-IBC with an unordinary phenotype, whose molecular mechanisms are still largely unknown to date. Discovering and identifying novel bio-markers responsible for diagnosis and therapeutic targets is a pressing need. MicroRNAs are a class of small non-coding RNAs that are capable to post-transcriptionally regulate gene expression of genes by targeting mRNAs, exerting vital and tremendous affects in numerous malignancy-related biological processes, including cell apoptosis, metabolism, proliferation and differentiation. In this study, we review present and high-quality evidences regarding the potential applications of inflammatory breast cancer associated microRNAs for diagnosis and prognosis of this lethal disease.

MARCKS protein overexpression in inflammatory breast cancer

Background

Inflammatory breast cancer (IBC) is the most aggressive form of locally-advanced breast cancer. Identification of new therapeutic targets is crucial. We previously reported MARCKS mRNA overexpression in IBC in the largest transcriptomics study reported to date. Here, we compared MARCKS protein expression in IBC and non-IBC samples, and searched for correlations between protein expression and clinicopathological features.

Results

Tumor samples showed heterogeneity with respect to MARCKS staining: 18% were scored as MARCKS-positive (stained cells ≥ 1%) and 82% as MARCKS-negative. MARCKS expression was more frequent in IBC (36%) than in non-IBC (11%; p = 1.4E−09), independently from molecular subtypes and other clinicopathological variables. We found a positive correlation between protein and mRNA expression in the 148/502 samples previously analyzed for MARCKS mRNA expression. MARCKS protein expression was associated with other poor-prognosis features in the whole series of samples such as clinical axillary lymph node or metastatic extension, high pathological grade, ER-negativity, PR-negativity, HER2-positivity, and triple-negative and HER2+ statutes. In IBC, MARCKS expression was the sole tested variable associated with poor MFS.

Materials and Methods

We retrospectively analyzed MARCKS protein expression by immunohistochemistry in 502 tumors, including 133 IBC and 369 non-IBC, from Tunisian and French patients. All samples were pre-therapeutic clinical samples. We searched for correlations between MARCKS expression and clinicopathological features including the IBC versus non-IBC phenotype and metastasis-free survival (MFS).

Conclusions

MARCKS overexpression might in part explain the poor prognosis of IBC. As an oncogene associated with poor MFS, MARCKS might represent a new potential therapeutic target in IBC.

Similar response profile to neoadjuvant chemotherapy, but different survival, in inflammatory versus locally advanced breast cancers

Inflammatory breast cancer (IBC) is a very aggressive form of breast cancer, as compared to locally advanced breast cancer (LABC). Neoadjuvant chemotherapy followed by surgery is the standard treatment in both cases. Whether IBC is less chemosensitive than LABC remains unclear. We retrospectively compared the rate of pathological complete response (pCR) to neoadjuvant chemotherapy in IBC and LABC. Methods: Patients with IBC or LABC treated with neoadjuvant anthracycline-based chemotherapy followed by surgery were selected from our institutional database. The primary endpoint was the pCR rate, defined as absence of invasive tumor in breast and axillary lymph nodes. Results: A total of 450 patients were included, 144 with IBC and 306 with LABC. The pCR rate was similar between the two groups, in the whole population (31%) and in each molecular subtype separately. Univariate analyses for pCR in IBC and LABC separately identified the same predictive variables, except the pathological type that was associated with pCR in LABC only, but not in IBC. IBC patients displayed shorter 5-year metastasis-free survival and overall survival than LABC patients in the whole population (57% and 69% versus74% and 88% respectively), and in each molecular subtype separately. The IBC phenotype was an independent prognostic feature. Similarly, IBC patients displayed shorter 5-year loco-regional relapse-free survival than LABC patients (86% versus 95%). Conclusions: Similar pCR rates to chemotherapy were found in IBC and LABC, suggesting that IBC is not less chemosensitive than LABC. Survival was shorter in IBC, suggesting that the corresponding poorer prognosis is more due to a higher metastatic risk and/or other feature(s) than to a lesser chemosensitivity.

Inflammatory breast cancer: a proposed conceptual shift in the UICC-AJCC TNM staging system

In the absence of histological criteria that distinguish between inflammatory and non-inflammatory breast cancer, diagnosis of inflammatory breast cancer relies entirely on the existence of clinical criteria as outlined by the TNM classification. This classification restricts patients presenting with clinical criteria characteristic of inflammatory breast cancer to subcategory T4d, which immediately relegates all patients with non-metastatic inflammatory breast cancer to stage 3, regardless of tumour size or nodal spread. Patients who present with metastatic disease are consigned to stage 4, and the TNM classification does not distinguish patients on the basis of the presence of inflammatory criteria. Evidence by our group and others suggests that patients with inflammatory breast cancer have significantly reduced overall survival among those who present with distant metastasis at diagnosis (stage 4). In light of these results, this Personal View addresses whether the current TNM staging classification accurately represents a distinction between patients with inflammatory and those with non-inflammatory breast cancer.

Identification of frequent somatic mutations in inflammatory breast cancer

PURPOSE

Inflammatory breast cancer is an aggressive form of breast cancer that shows distinct clinical features from non-inflammatory breast cancer. Genomic understanding of inflammatory breast cancer will shed light on biological targets for this disease. Our objective was to identify targeted hotspot mutations using multiplex genome sequencing in inflammatory breast cancer and compare the findings with those for patients with non-inflammatory breast cancer to further recognize novel targets.

METHODS

We studied 400 patients with metastatic breast cancer who had somatic hotspot mutation testing using a 46- or 50-gene multiplex platform from March 2012 to December 2014. Among this population, 24 patients had inflammatory breast cancer and 376 patients had non-inflammatory breast cancer. We tested a total of 26 samples from 24 patients with inflammatory breast cancer.

RESULTS

The average number of mutations per patient was higher in inflammatory breast cancer than in non-inflammatory breast cancer (1.23 vs. 0.65, respectively). Identified somatic mutations in inflammatory breast cancer were TP53 (n = 18, 75%), PIK3CA (n = 10, 41.7%), and ERBB2 (n = 4, 16.7%). TP53 and ERBB2 mutations were significantly more prevalent in inflammatory breast cancer than in non-inflammatory breast cancer (P < 0.01). All patients with ERBB2 mutations had hormone receptor (HR)+ primary tumors.

CONCLUSIONS

TP53, PIK3CA, and ERBB2 were detected as three major somatic mutations in metastatic inflammatory breast cancer patients. While the inflammatory breast cancer TP53 and PIK3CA mutations mirrored previously reported data for metastatic non-inflammatory breast cancer, this is the first report of higher frequency of ERBB2 mutation in inflammatory breast cancer, especially in the HR+ subtype. Once validated in a larger cohort of inflammatory breast cancer patients, this novel finding could lead to development of treatments for HR+ inflammatory breast cancer.

Macrophages Enhance Migration in Inflammatory Breast Cancer Cells via RhoC GTPase Signaling

Inflammatory breast cancer (IBC) is the most lethal form of breast cancer. All IBC patients have lymph node involvement and one-third of patients already have distant metastasis at diagnosis. This propensity for metastasis is a hallmark of IBC distinguishing it from less lethal non-inflammatory breast cancers (nIBC). Genetic profiling studies have been conducted to differentiate IBC from nIBC, but no IBC cancer-cell-specific gene signature has been identified. We hypothesized that a tumor-extrinsic factor, notably tumor-associated macrophages, promotes and contributes to IBC’s extreme metastatic phenotype. To this end, we studied the effect of macrophage-conditioned media (MCM) on IBC. We show that two IBC cell lines are hyper-responsive to MCM as compared to normal-like breast and aggressive nIBC cell lines. We further interrogated IBC’s hyper-responsiveness to MCM using a microfluidic migration device, which permits individual cell migration path tracing. We found the MCM “primes” the IBC cells’ cellular machinery to become extremely migratory in response to a chemoattractant. We determined that interleukins −6, −8, and −10 within the MCM are sufficient to stimulate this enhanced IBC migration effect, and that the known metastatic oncogene, RhoC GTPase, is necessary for the enhanced migration response.

Prognostic impact of hormone receptor- and HER2-defined subtypes in inflammatory breast cancer treated with high-dose chemotherapy: a retrospective study

Purpose: Studies examining high-dose chemotherapy with autologous hematopoietic stem cell transplantation (HDC-AHSCT) strategies in inflammatory breast cancer (IBC), showed encouraging results in terms of disease-free survival (DFS), and overall survival (OS). The lack of data regarding HER2 status in all of these studies prevented any prognostic analysis involving breast cancer subtypes. Methods: All consecutive female patients treated for IBC with HDC and AHSCT at Institut Paoli-Calmettes between 2003 and 2012 were included. Since 2005, trastuzumab was included in initial treatment. Patient, tumor and treatment characteristics were collected. Patients were categorized in three subtypes based on hormonal receptor (HR) and HER2 status of the primary tumor: Luminal, (HR+/HER2-), HER2 (HER2+, any HR), and triple negative (TN) (HER2- and HR-). The main objective was the analysis of OS according to the IHC subtypes. Results: Sixty-seven patients were included. Eleven patients received trastuzumab. Median follow up was 80.04 months (95% CI 73.2-88.08). Five-year OS and DFS for the whole population patients were 74% (95% CI 61-83) and 65 % (95% CI 52-75), respectively. OS differed across subtypes (p=0.057) : HER2 subgroup appeared to have the best prognosis with a 5-year OS of 89% (95% CI 64-97) compared to 57% (95% CI 33-76) for the TN subgroup (HR 5.38, 95% CI 1.14-25.44; p=0.034). Conclusions: In IBC patients receiving HDC-AHSCT, OS favorably compares with data available in the literature on similar groups of patients. TN patients carried the least favourable OS and HER2 patients, half of them also receiving trastuzumab, had the best outcome. These findings provide additional information and options for patients with IBC and who could potentially benefit of HDC-AHSCT.

MicroRNA expression profiling identifies decreased expression of miR-205 in inflammatory breast cancer

Inflammatory breast cancer is the most aggressive form of breast cancer. Identifying new biomarkers to be used as therapeutic targets is in urgent need. Messenger RNA expression profiling studies have indicated that inflammatory breast cancer is a transcriptionally heterogeneous disease, and specific molecular targets for inflammatory breast cancer have not been well established. We performed microRNA expression profiling in inflammatory breast cancer in comparison with locally advanced noninflammatory breast cancer in this study. Although many microRNAs were differentially expressed between normal breast tissue and tumor tissue, most of them did not show differential expression between inflammatory and noninflammatory tumor samples. However, by microarray analysis, quantitative reverse transcription PCR, and in situ hybridization, we showed that microRNA-205 expression was decreased not only in tumor compared with normal breast tissue, but also in inflammatory breast cancer compared with noninflammatory breast cancer. Lower expression of microRNA-205 correlated with worse distant metastasis-free survival and overall survival in our cohort. A small-scale immunohistochemistry analysis showed coexistence of decreased microRNA-205 expression and decreased E-cadherin expression in some ductal tumors. MicroRNA-205 may serve as a therapeutic target in advanced breast cancer including inflammatory breast cancer.

Hyperactivated mTOR and JAK2/STAT3 Pathways: Molecular Drivers and Potential Therapeutic Targets of Inflammatory and Invasive Ductal Breast Cancers After Neoadjuvant Chemotherapy

INTRODUCTION

Inflammatory breast cancer (IBC) is an aggressive and rare cancer with a poor prognosis and a need for novel targeted therapeutic strategies. Preclinical IBC data showed strong activation of the phosphatidylinositide-3-kinase/mammalian target of rapamycin (mTOR) and Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathways, and expression of inflammatory cytokines and tumor-associated macrophages (TAMs).

PATIENTS AND METHODS

Archival tumor tissue from 3 disease types (IBC treated with neoadjuvant chemotherapy [NAC], n = 45; invasive ductal carcinoma [IDC] treated with NAC [n = 24; 'treated IDC'; and untreated IDC [n = 27; 'untreated IDC']) was analyzed for the expression of biomarkers phospho-S6 (pS6) (mTOR), phospho-JAK2 (pJAK2), pSTAT3, interleukin (IL)-6, CD68 (monocytes, macrophages), and CD163 (TAMs). Surrounding nontumor tissue was also analyzed.

RESULTS

Biomarker levels and surrogate activity according to site-specific phosphorylation were shown in the tumor tissue of all 3 disease types but were greatest in IBC and treated IDC and least in untreated IDC for pS6, pJAK2, pSTAT3, and IL-6. Of 37 IBC patients with complete biomarker data available, 100% were pS6-positive and 95% were pJAK2-positive. In nontumor tissue, biomarker levels were observed in all groups but were generally greatest in untreated IDC and least in IBC, except for JAK2.

CONCLUSION

IBC and treated IDC display similar levels of mTOR and JAK2 biomarker activation, which suggests a potential mechanism of resistance after NAC. Biomarker levels in surrounding nontumor tissue suggested that the stroma might be activated by chemotherapy and resembles the oncogenic tumor-promoting environment. Activation of pS6 and pJAK2 in IBC might support dual targeting of the mTOR and JAK/STAT pathways, and the need for prospective studies to investigate combined targeted therapies in IBC.

[Systemic treatments of inflammatory breast cancer: an overview]

The poor prognosis of inflammatory breast cancer (IBC) is due to its strong metastatic potential. During the last three decades, the introduction of neoadjuvant chemotherapy (CT), and its improvement with successive additions of anthracyclines and then taxanes, allowed to double the survival. However, the 5-year survival still remains lower than 50%, with the pathological complete response (pCR) to neoadjuvant CT being a major prognostic factor. Since 1995, several innovative approaches have been evaluated. Initially, the trials of high-dose CT with hematopoietic stem cell transplantation have generated promising results, but ultimately failed to change standards of treatment, in particular because of its toxicity. More recently, a few targeted therapies, combined to conventional CT, have been assessed, due to the frequent overexpression of HER2 and EGFR and the important vascularization of IBC. Trastuzumab, a monoclonal antibody targeting HER2, has shown a clear advantage in terms of pCR and survival in studies dedicated to, HER2-positive locally advanced breast cancers, including IBC. Lapatinib, a dual tyrosine kinase inhibitor anti-HER2 and EGFR, has shown significant activity in two phase II studies dedicated to HER2-positive IBC. The interest of HER2-double blockade by the combination of trastuzumab-pertuzumab combined to docetaxel has been demonstrated in term of pCR in the NEOSPHERE study which also included HER2-positive IBC. Among the anti-angiogenic drugs tested in studies dedicated to IBC, bevacizumab has given the most interesting results in term of efficacy/toxicity ratio. In the Beverly 2 study HER2-positive IBC patients were treated by the combination chemotherapy, trastuzumab and bevacizumab: the rate of pCR was 64%, and the 3-year disease-free and overall survivals were 68% and 90%, respectively; the increase of endothelial cells circulating was inversely correlated to the probability of pCR. All those treatments have been extrapolated from standard breast cancers. Thus, a deep molecular knowledge of IBC appears to be critical in order to develop specific treatments effectively targeting its particular aggressiveness.

TLRs: linking inflammation and breast cancer

Breast cancer is one of the leading causes of mortality in the females. Intensive efforts have been made to understand the molecular mechanisms of pathogenesis of breast cancer. The physiological conditions that lead to tumorigenesis including breast cancer are not well understood. Toll like receptors (TLRs) are essential components of innate immune system that protect the host against bacterial and viral infection. The emerging evidences suggest that TLRs are activated through pathogen associated molecular patterns (PAMPs) as well as endogenous molecules, which lead to the activation of inflammatory pathways. This leads to increased levels of several pro-inflammatory cytokines and chemokines mounting inflammation. Several evidences support the view that chronic inflammation can lead to cancerous condition. Inflammation aids in tumor progression and metastasis. Association of inflammation with breast cancer is emerging. TLR mediated activation of NF-κB and IRF is an essential link connecting inflammation to cancer. The recent reports provide several evidences, which suggest the important role of TLRs in breast cancer pathogenesis and recurrence. The current review focuses on emerging studies suggesting the strong linkages of TLR mediated regulation of inflammation during breast cancer and its metastasis emphasizing the initiation of the systematic study.

Genomic profiling of inflammatory breast cancer: a review

Inflammatory breast cancer (IBC) is a rare but aggressive form of breast cancer. Despite efforts in the past decade to delineate the molecular biology of IBC by applying high-throughput molecular profiling technologies to clinical samples, IBC remains insufficiently characterized. The reasons for that include limited sizes of the study population, heterogeneity with respect to the composition of the IBC and non-IBC control groups and technological differences across studies. In 2008, the World IBC Consortium was founded to foster collaboration between research groups focusing on IBC. One of the initial projects was to redefine the molecular profile of IBC using an unprecedented number of samples and search for gene signatures associated with survival and response to neo-adjuvant chemotherapy. Here, we provide an overview of all the molecular profiling studies that have been performed on IBC clinical samples to date.

Gene expression profiles of inflammatory breast cancer: correlation with response to neoadjuvant chemotherapy and metastasis-free survival

BACKGROUND

Inflammatory breast cancer (IBC) is an aggressive disease. To date, no molecular feature reliably predicts either the response to chemotherapy (CT) or the survival. Using DNA microarrays, we searched for multigene predictors.

PATIENTS AND METHODS

The World IBC Consortium generated whole-genome expression profiles of 137 IBC and 252 non-IBC (nIBC) samples. We searched for transcriptional profiles associated with pathological complete response (pCR) to neoadjuvant anthracycline-based CT and distant metastasis-free survival (DMFS) in respective subsets of 87 and 106 informative IBC samples. Correlations were investigated with predictive and prognostic gene expression signatures published in nIBC (nIBC-GES). Supervised analyses tested genes and activation signatures of 19 biological pathways and 234 transcription factors.

RESULTS

Three of five tested prognostic nIBC-GES and the two tested predictive nIBC-GES discriminated between IBC with and without pCR, as well as two interferon activation signatures. We identified a 107-gene signature enriched for immunity-related genes that distinguished between responders and nonresponders in IBC. Its robustness was demonstrated by external validation in three independent sets including two IBC sets and one nIBC set, with independent significant predictive value in IBC and nIBC validation sets in multivariate analysis. We found no robust signature associated with DMFS in patients with IBC, and neither of the tested prognostic GES, nor the molecular subtypes were informative, whereas they were in our nIBC series (220 stage I-III informative samples).

CONCLUSION

Despite the relatively small sample size, we show that response to neoadjuvant CT in IBC is, as in nIBC, associated with immunity-related processes, suggesting that similar mechanisms responsible for pCR exist. Analysis of a larger IBC series is warranted regarding the correlation of gene expression profiles and DMFS.

Inflammatory and microenvironmental factors involved in breast cancer progression

The primary reason for the high mortality rate of breast cancer is metastasis, which can result in a poor survival rate. The tumor environment is important for promotion and invasion of cancer cells. Recent studies have shown that inflammation is associated with breast cancer. Therefore, it is important to investigate the role of the inflammatory and microenvironment in breast cancer progression and metastasis. The present review summarizes some of the markers for inflammation and breast cancer invasion, which may aid in the design of an appropriate therapy for metastatic breast cancer. The following four inflammatory markers are discussed in this review: (1) Tumor associated macrophages (TAMs); (2) Matrix metalloproteinases (MMPs); (3) Sphingosine 1-phosphate (S1P); (4) C-reactive protein (CRP). TAMs are commonly found in breast cancer patients, and high infiltration is positively correlated with poor prognosis and low survival rate. MMPs are well-known for their roles in the degradation of ECM components when cancer cells invade and migrate. MMPs are also associated with inflammation through recruitment of a variety of stromal cells such as fibroblasts and leukocytes. S1P is an inflammatory lipid and is involved in various cellular processes such as proliferation, survival, and migration. Recent studies indicate that S1P participates in breast cancer invasion in various ways. CRP is used clinically to indicate the outcome of cancer patients as well as acute inflammatory status. This review summarizes the current understanding on the role of S1P in CRP expression which promotes the breast epithelial cell invasion, suggesting a specific mechanism linking inflammation and breast cancer. The present review might be useful for understanding the relationship between inflammation and breast cancer for the development of pharmacological interventions that may control the primary molecules involved in the breast cancer microenvironment.

Uncovering the molecular secrets of inflammatory breast cancer biology: an integrated analysis of three distinct affymetrix gene expression datasets

BACKGROUND

Inflammatory breast cancer (IBC) is a poorly characterized form of breast cancer. So far, the results of expression profiling in IBC are inconclusive due to various reasons including limited sample size. Here, we present the integration of three Affymetrix expression datasets collected through the World IBC Consortium allowing us to interrogate the molecular profile of IBC using the largest series of IBC samples ever reported.

EXPERIMENTAL DESIGN

Affymetrix profiles (HGU133-series) from 137 patients with IBC and 252 patients with non-IBC (nIBC) were analyzed using unsupervised and supervised techniques. Samples were classified according to the molecular subtypes using the PAM50-algorithm. Regression models were used to delineate IBC-specific and molecular subtype-independent changes in gene expression, pathway, and transcription factor activation.

RESULTS

Four robust IBC-sample clusters were identified, associated with the different molecular subtypes (P<0.001), all of which were identified in IBC with a similar prevalence as in nIBC, except for the luminal A subtype (19% vs. 42%; P<0.001) and the HER2-enriched subtype (22% vs. 9%; P<0.001). Supervised analysis identified and validated an IBC-specific, molecular subtype-independent 79-gene signature, which held independent prognostic value in a series of 871 nIBCs. Functional analysis revealed attenuated TGF-β signaling in IBC.

CONCLUSION

We show that IBC is transcriptionally heterogeneous and that all molecular subtypes described in nIBC are detectable in IBC, albeit with a different frequency. The molecular profile of IBC, bearing molecular traits of aggressive breast tumor biology, shows attenuation of TGF-β signaling, potentially explaining the metastatic potential of IBC tumor cells in an unexpected manner.

How do I treat inflammatory breast cancer?

Inflammatory breast cancer (IBC) is an uncommon and aggressive presentation of locally advanced breast cancer that is potentially curable when localized but may be associated with distant metastasis in up to one-third of patients at presentation. The diagnosis of IBC is made based on clinical features, including the presence of skin edema and erythema involving at least one-third of the breast, with or without a mass, and usually associated with dermal lymphatic invasion (DLI) on skin biopsy. Management requires combined modality therapy, including neoadjuvant chemotherapy with an anthracycline and taxane-based regimen, followed by surgery and radiotherapy, plus concurrent anti-HER2 therapy for HER2-positive disease, and endocrine therapy for at least 5 years after surgery for estrogen-receptor-positive disease (Fig. 1). There have been few large clinical trials focused on IBC; therefore, most data regarding treatment are derived from retrospective analyses, small studies, and extrapolation of results from trials of noninflammatory locally advanced breast cancer. Patients with IBC should be encouraged to enroll in clinical trials whenever possible. In addition, further research into the biology of IBC may help to elucidate the mechanisms underlying its aggressive clinical behavior and to assist in the development of therapies targeted for this specific population.

Inflammatory breast cancer (IBC): clues for targeted therapies

Inflammatory breast cancer (IBC) is the most aggressive type of advanced breast cancer characterized by rapid proliferation, early metastatic development and poor prognosis. Since there are few preclinical models of IBC, there is a general lack of understanding of the complexity of the disease. Recently, we have developed a new model of IBC derived from the pleural effusion of a woman with metastatic secondary IBC. FC-IBC02 cells are triple negative and form clusters (mammospheres) in suspension that are strongly positive for E-cadherin, β-catenin and TSPAN24, all adhesion molecules that play an important role in cell migration and invasion. FC-IBC02 cells expressed stem cell markers and some, but not all of the characteristics of cells undergoing epithelial mesenchymal transition (EMT). Breast tumor FC-IBC02 xenografts developed quickly in SCID mice with the presence of tumor emboli and the development of lymph node and lung metastases. Remarkably, FC-IBC02 cells were able to produce brain metastasis in mice on intracardiac or intraperitoneal injections. Genomic studies of FC-IBC02 and other IBC cell lines showed that IBC cells had important amplification of 8q24 where MYC, ATAD2 and the focal adhesion kinase FAK1 are located. MYC and ATAD2 showed between 2.5 and 7 copies in IBC cells. FAK1, which plays important roles in anoikis resistance and tumor metastasis, showed 6–4 copies in IBC cells. Also, CD44 was amplified in triple-negative IBC cells (10–3 copies). Additionally, FC-IBC02 showed amplification of ALK and NOTCH3. These results indicate that MYC, ATAD2, CD44, NOTCH3, ALK and/or FAK1 may be used as potential targeted therapies against IBC.

Regulation of inflammatory breast cancer cell invasion through Akt1/PKBα phosphorylation of RhoC GTPase

With a 42% and 18% 5- and 10-year respective disease-free survival rate, inflammatory breast cancer (IBC) is arguably the deadliest form of breast cancer. IBC invades the dermal lymphatic vessels of the skin overlying the breast and as a consequence nearly all women have lymph node involvement and ~1/3 have gross distant metastases at the time of diagnosis. One year after diagnosis ~90% of patients have detectable metastases, making IBC a paradigm for lymphovascular invasion. Understanding the underlying mechanisms of the IBC metastatic phenotype is essential for new therapies. Work from our laboratory and others show distinct molecular differences between IBC and non-IBCs (nIBCs). Previously we showed that RhoC GTPase is a metastatic switch responsible for the invasive phenotype of IBC. In this study we integrate observations made in IBC patients with in vitro analysis. We show that the PI3K/Akt signaling pathway is crucial in IBC invasion. Key molecules involved in cytoskeletal control and cell motility are specifically upregulated in IBC patients compared with stage and cell-type-of-origin matched nIBCs patients. Distinctively, RhoC GTPase is a substrate for Akt1 and its phosphorylation is absolutely essential for IBC cell invasion. Further our data show that Akt3, not Akt1 has a role in IBC cell survival. Together our data show a unique and targetable pathway for IBC invasion and survival.

8q24 Cancer risk allele associated with major metastatic risk in inflammatory breast cancer

BACKGROUND

Association studies have identified low penetrance alleles that participate to the risk of cancer development. The 8q24 chromosomal region contains several such loci involved in various cancers that have been recently studied for their propensity to influence the clinical outcome of prostate cancer. We investigated here two 8q24 breast and colon cancer risk alleles in the close vicinity of the MYC gene for their role in the occurrence of distant metastases.

METHODOLOGY/PRINCIPAL FINDINGS

A retrospective series of 449 patients affected with breast or colon adenocarcinoma was genotyped for the rs13281615 and/or rs6983267 SNPs. Statistical analyses were done using the survival package v2.30 in the R software v2.9.1. The two SNPs did not influence the development of distant metastases of colon cancer; rs6983267 showed a mild effect on breast cancer. However, this effect was greatly emphasized when considering inflammatory breast cancer (IBC) solely. Replicated on a larger and independent series of IBC the contribution of the genotype to the metastatic risk of IBC was found an independent predictor of outcome (p = 2e-4; OR 8.3, CI95:2.6-33).

CONCLUSIONS/SIGNIFICANCE

Our study shows first that the monitoring of this specific germline variation may add a substantial tool for IBC prognostication, an aggressive disease that evolves towards distant metastases much more frequently than non-IBC and for which no reliable prognostic factor is available in medical practice. Second, it more generally suggests that risk alleles, while associated with low susceptibility, could correlate with a high risk of metastasis.

Inflammatory breast cancer: what we know and what we need to learn

PURPOSE

We review the current status of multidisciplinary care for patients with inflammatory breast cancer (IBC) and discuss what further research is needed to advance the care of patients with this disease.

DESIGN

We performed a comprehensive review of the English-language literature on IBC through computerized literature searches.

RESULTS

Significant advances in imaging, including digital mammography, high-resolution ultrasonography with Doppler capabilities, magnetic resonance imaging, and positron emission tomography-computed tomography, have improved the diagnosis and staging of IBC. There are currently no established molecular criteria for distinguishing IBC from noninflammatory breast cancer. Such criteria would be helpful for the diagnosis and development of novel targeted therapies. Combinations of neoadjuvant systemic chemotherapy, surgery, and radiation therapy have led to an improved prognosis; however, the overall 5-year survival rate for patients with IBC remains very low (∼30%). Sentinel lymph node biopsy and skin-sparing mastectomy are not recommended for patients with IBC.

CONCLUSION

Optimal management of IBC requires close coordination among medical, surgical, and radiation oncologists, as well as radiologists and pathologists. There is a need to identify molecular changes that define the pathogenesis of IBC to enable eradication of IBC with the use of IBC-specific targeted therapies.

Nestin expression associates with poor prognosis and triple negative phenotype in locally advanced (T4) breast cancer

Nestin, an intermediate filament protein, has traditionally been noted for its importance as a neural stem cell marker. However, in recent years, expression of nestin has shown to be associated with general proliferation of progenitor cell populations within neoplasms. There is no reported study addressing nestin expression in T4 breast cancer patients. Thus, the aim of the present study was to investigate, through immunohistochemistry, the expression and distribution of nestin in T4 breast cancer, in order to determine its association with clinical and pathological parameters as well as with patients' outcome. Nestin was detectable in tumoral cells and in endothelial cells of blood microvessels, and it is significantly expressed in triple-negative and in inflammatory breast cancer (IBC) subgroups of T4 breast tumours. The Kaplan-Meier analysis showed that the presence of nestin in tumoral cells significantly predicted poor prognosis at 5-years survival (P=0.02) and with borderline significance at 10-years of survival (P=0.05) in T4 breast cancer patients. On the basis of these observations, we speculate that nestin expression may characterize tumours with an aggressive clinical behavior, suggesting that the presence of nestin in tumoral cells and vessels may be considered an important factor that leads to a poor prognosis. Further studies are awaited to define the biological role of nestin in the etiology of these subgroups of breast cancers.

Choosing the right cell line for breast cancer research

Breast cancer is a complex and heterogeneous disease. Gene expression profiling has contributed significantly to our understanding of this heterogeneity at a molecular level, refining taxonomy based on simple measures such as histological type, tumour grade, lymph node status and the presence of predictive markers like oestrogen receptor and human epidermal growth factor receptor 2 (HER2) to a more sophisticated classification comprising luminal A, luminal B, basal-like, HER2-positive and normal subgroups. In the laboratory, breast cancer is often modelled using established cell lines. In the present review we discuss some of the issues surrounding the use of breast cancer cell lines as experimental models, in light of these revised clinical classifications, and put forward suggestions for improving their use in translational breast cancer research.

Inflammatory breast cancer: high risk of contralateral breast cancer compared to comparably staged non-inflammatory breast cancer

Inflammatory breast cancer (IBC), the most lethal form of breast cancer, has characteristics linked to higher risk of contralateral breast cancer. However, no large studies have examined risk of contralateral breast cancer following IBC. We calculated absolute risk of invasive contralateral breast cancer among 5,631 IBC and 174,634 comparably staged non-IBC first breast cancer cases who survived at least 2 months following diagnosis and were reported to 13 Surveillance, Epidemiology, and End Results (SEER) registries between January 1, 1973 and December 31, 2006. We considered that contralateral cancers occurring within 2-23 months of first cancer diagnosis may more likely be metastatic/recurrent disease and those occurring 2 or more years after diagnosis independent primaries. Absolute risk of contralateral breast cancer was generally greater following IBC than regional/distant non-IBC, regardless of age and hormone receptor status of first cancer diagnosis. Much of the increase in absolute risk following IBC occurred within 2-23 months of first cancer diagnosis, while the risk for non-IBC occurred more gradually over time since diagnosis. For instance, among women first diagnosed before age 50, absolute risks following IBC and non-IBC were 4.9 vs. 1.1% at 2 years, 6.0 vs. 2.2% at 5 years, and 7.7 vs. 6.1% at 20 years after diagnosis. However, patterns of higher risk following IBC than non-IBC were also evident for at least 10-15 years in the subcohort of women who survived at least 24 months without a contralateral cancer. In conclusion, our results suggest that IBC has higher risk of cancer in the contralateral breast than comparably staged non-IBC, possibly due to both metastatic/recurrent disease and independent primaries.

MicroRNA profiling in cancer

The diagnosis of cancer has undergone major changes in the last 40 years. Once based purely on morphology, diagnosis has come to incorporate immunological, cytogenetic and molecular methods. Many cancers, especially leukaemias, are now defined by molecular markers. Gene expression profiling based on mRNA has led to further refinement of the classification and diagnosis of cancer. More recently, miRNAs (microRNAs), among other small non-coding RNA molecules, have been discovered and found to be major players in cell biology. miRNAs, having both oncogenic and tumour-suppressive functions, are dysregulated in many types of cancer. miRNAs also interfere with metastasis, apoptosis and invasiveness of cancer cells. In the present review, we discuss recent advances in miRNA profiling in human cancer. We discuss both frequent and rare tumour types and give an outlook on future developments.