Developmental therapeutics for inflammatory breast cancer: Biology and translational directions

Comparison of the genomic alterations present in tumor samples from patients with metastatic inflammatory versus non-inflammatory breast cancer reveals AURKA as a potential treatment target

Inflammatory breast cancer (IBC) is a rare but aggressive subtype of breast cancer, mainly characterized using primary tumor samples. Here, using public datasets, we compared the genomic alterations in primary and metastatic samples from patients with metastatic IBC versus patients with metastatic non-IBC. We observed a higher frequency of AURKA amplification in IBC. We further showed that AURKA amplification was associated with increased AURKA mRNA expression, which we demonstrated was higher in IBC. Finally, higher protein expression of AURKA was associated with worse prognosis in patients with IBC. These findings deserve further investigation given the existence of AURKA-inhibitors.

Circulating PIK3CA mutation detection at diagnosis in non-metastatic inflammatory breast cancer patients

Inflammatory breast cancer (IBC) is an aggressive BC subtype with poor outcomes. A targetable somatic PIK3CA mutation is reported in 30% of IBC, allowing for treatment by PI3Kα-specific inhibitors, such as alpelisib. The aim of this study was to evaluate the detection rate of circulating PIK3CA mutation in locally-advanced IBC (LAIBC) patients harbouring a PIK3CA mutation on initial biopsy. This monocentric retrospective study was based on available stored plasma samples and tumour biopsies at diagnosis from all LAIBC patients treated with neo-adjuvant chemotherapy (NCT) between 2008 and 2018 at the Centre Henri Becquerel. PIK3CA mutations (E542K, E545K, H1047R/L) were assessed by droplet digital PCR (ddPCR) in plasma samples and tumoral tissue at diagnosis. A total of 55 patients were included. Overall, 14/55 patients (25%) had a PIK3CA mutation identified on baseline biopsy (H1047R = 8; H1047L = 3; E545K = 2; E542K = 1). Among them, 11 (79%) patients had enough DNA for circulating DNA analyses, and corresponding circulating PIK3CA mutations were found in 6/11 (55%). Among the 41 patients without PIK3CA mutations on biopsy, 32 (78%) had enough DNA for circulating DNA analysis, and no circulating PIK3CA mutation was identified. Our results revealed no prognostic or predictive value of PIK3CA mutations at the diagnosis of non-metastatic IBC but highlighted the prognostic value of the cfDNA rate at diagnosis. Our study showed that a corresponding circulating PIK3CA mutation was identified in 55% of LAIBC patients with PIK3CA-mutated tumours, while no circulating mutation was found among patients with PI3KCA wild-type tumours.

Lipocalin 2 promotes inflammatory breast cancer tumorigenesis and skin invasion

Inflammatory breast cancer (IBC) is an aggressive form of primary breast cancer characterized by rapid onset and high risk of metastasis and poor clinical outcomes. The biological basis for the aggressiveness of IBC is still not well understood and no IBC-specific targeted therapies exist. In this study, we report that lipocalin 2 (LCN2), a small secreted glycoprotein belonging to the lipocalin superfamily, is expressed at significantly higher levels in IBC vs non-IBC tumors, independently of molecular subtype. LCN2 levels were also significantly higher in IBC cell lines and in their culture media than in non-IBC cell lines. High expression was associated with poor-prognosis features and shorter overall survival in IBC patients. Depletion of LCN2 in IBC cell lines reduced colony formation, migration, and cancer stem cell populations in vitro and inhibited tumor growth, skin invasion, and brain metastasis in mouse models of IBC. Analysis of our proteomics data showed reduced expression of proteins involved in cell cycle and DNA repair in LCN2-silenced IBC cells. Our findings support that LCN2 promotes IBC tumor aggressiveness and offer a new potential therapeutic target for IBC.

NDRG1 Expression Is an Independent Prognostic Factor in Inflammatory Breast Cancer

Simple Summary

Inflammatory breast cancer (IBC) is a rare and aggressive variant of breast cancer that is responsible for a significant number of breast cancer-related deaths. Herein, we describe how the expression of a specific protein named N-myc downstream-regulated gene 1 (NDRG1), commonly described as a gene that prevents the spread of cancer cells to distant organs, may have a paradoxical role in cancer progression in IBC. We found that the level of expression of NDRG1 in tumor tissues predicts the survival outcome of patients with IBC. We also observed that NDRG1, together with other important prognostic factors such as estrogen receptor status and stage, could be used to further analyze prognostic outcome or treatment response of patients.

Abstract

NDRG1 is widely described as a metastasis suppressor in breast cancer. However, we found that NDRG1 is critical in promoting tumorigenesis and brain metastasis in mouse models of inflammatory breast cancer (IBC), a rare but highly aggressive form of breast cancer. We hypothesized that NDRG1 is a prognostic marker associated with poor outcome in patients with IBC. NDRG1 levels in tissue microarrays from 64 IBC patients were evaluated by immunohistochemical staining with NDRG1 (32 NDRG1-low (≤median), 32 NDRG1-high (>median)). Overall and disease-free survival (OS and DSS) were analyzed with Kaplan–Meier curves and log-rank test. Univariate analysis showed NDRG1 expression, tumor grade, disease stage, estrogen receptor (ER) status, and receipt of adjuvant radiation to be associated with OS and DSS. NDRG1-high patients had poorer 10-year OS and DSS than NDRG1-low patients (OS, 19% vs. 45%, p = 0.0278; DSS, 22% vs. 52%, p = 0.0139). On multivariable analysis, NDRG1 independently predicted OS (hazard ratio (HR) = 2.034, p = 0.0274) and DSS (HR = 2.287, p = 0.0174). NDRG1-high ER-negative tumors had worse outcomes OS, p = 0.0003; DSS, p = 0.0003; and NDRG1-high tumors that received adjuvant radiation treatment had poor outcomes (OS, p = 0.0088; DSS, p = 0.0093). NDRG1 was a significant independent prognostic factor for OS and DSS in IBC patients. Targeting NDRG1 may represent a novel strategy for improving clinical outcomes for patients with IBC.

In vitro vascularized tumor platform for modeling tumor-vasculature interactions of inflammatory breast cancer

Inflammatory breast cancer (IBC), a rare form of breast cancer associated with increased angiogenesis and metastasis, is largely driven by tumor-stromal interactions with the vasculature and the extracellular matrix (ECM). However, there is currently a lack of understanding of the role these interactions play in initiation and progression of the disease. In this study, we developed the first three-dimensional, in vitro, vascularized, microfluidic IBC platform to quantify the spatial and temporal dynamics of tumor-vasculature and tumor-ECM interactions specific to IBC. Platforms consisting of collagen type 1 ECM with an endothelialized blood vessel were cultured with IBC cells, MDA-IBC3 (HER2+) or SUM149 (triple negative), and for comparison to non-IBC cells, MDA-MB-231 (triple negative). Acellular collagen platforms with endothelialized blood vessels served as controls. SUM149 and MDA-MB-231 platforms exhibited a significantly (p < .05) higher vessel permeability and decreased endothelial coverage of the vessel lumen compared to the control. Both IBC platforms, MDA-IBC3 and SUM149, expressed higher levels of vascular endothelial growth factor (p < .05) and increased collagen ECM porosity compared to non-IBCMDA-MB-231 (p < .05) and control (p < .01) platforms. Additionally, unique to the MDA-IBC3 platform, we observed progressive sprouting of the endothelium over time resulting in viable vessels with lumen. The newly sprouted vessels encircled clusters of MDA-IBC3 cells replicating a key feature of in vivo IBC. The IBC in vitro vascularized platforms introduced in this study model well-described in vivo and clinical IBC phenotypes and provide an adaptable, high throughput tool for systematically and quantitatively investigating tumor-stromal mechanisms and dynamics of tumor progression.

The CD151-midkine pathway regulates the immune microenvironment in inflammatory breast cancer

The immune microenvironment in inflammatory breast cancer (IBC) is poorly characterised, and molecular and cellular pathways that control accumulation of various immune cells in IBC tissues remain largely unknown. Here, we discovered a novel pathway linking the expression of the tetraspanin protein CD151 in tumour cells with increased accumulation of macrophages in cancerous tissues. It is notable that elevated expression of CD151 and a higher number of tumour-infiltrating macrophages correlated with better patient responses to chemotherapy. Accordingly, CD151-expressing IBC xenografts were characterised by the increased infiltration of macrophages. In vitro migration experiments demonstrated that CD151 stimulates the chemoattractive potential of IBC cells for monocytes via mechanisms involving midkine (a heparin-binding growth factor), integrin α6β1, and production of extracellular vesicles (EVs). Profiling of chemokines secreted by IBC cells demonstrated that CD151 increases production of midkine. Purified midkine specifically stimulated migration of monocytes, but not other immune cells. Further experiments demonstrated that the chemoattractive potential of IBC-derived EVs is blocked by anti-midkine antibodies. These results demonstrate for the first time that changes in the expression of a tetraspanin protein by tumour cells can affect the formation of the immune microenvironment by modulating recruitment of effector cells to cancerous tissues. Therefore, a CD151-midkine pathway can be considered as a novel target for controlled changes of the immune landscape in IBC. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

A history of exploring cancer in context

The concept that progression of cancer is regulated by interactions of cancer cells with their microenvironment was postulated by Stephen Paget over a century ago. Contemporary tumour microenvironment (TME) research focuses on the identification of tumour-interacting microenvironmental constituents, such as resident or infiltrating non-tumour cells, soluble factors and extracellular matrix components, and the large variety of mechanisms by which these constituents regulate and shape the malignant phenotype of tumour cells. In this Timeline article, we review the developmental phases of the TME paradigm since its initial description. While illuminating controversies, we discuss the importance of interactions between various microenvironmental components and tumour cells and provide an overview and assessment of therapeutic opportunities and modalities by which the TME can be targeted.

Clinically relevant inflammatory breast cancer patient-derived xenograft-derived ex vivo model for evaluation of tumor-specific therapies

Inflammatory breast cancer (IBC) is a rare and aggressive presentation of invasive breast cancer with a 62% to 68% 5-year survival rate. It is the most lethal form of breast cancer, and early recognition and treatment is important for patient survival. Like non-inflammatory breast cancer, IBC comprises multiple subtypes, with the triple-negative subtype being overrepresented. Although the current multimodality treatment regime of anthracycline- and taxane-based neoadjuvant therapy, surgery, and radiotherapy has improved the outcome of patients with triple-negative IBC, overall survival continues to be worse than in patients with non-inflammatory locally advanced breast cancer. Translation of new therapies into the clinics to successfully treat IBC has been poor, in part because of the lack of in vitro preclinical models that can accurately predict the response of the original tumor to therapy. We report the generation of a preclinical IBC patient-derived xenograft (PDX)-derived ex vivo (PDXEx) model and show that it closely replicates the tissue architecture of the original PDX tumor harvested from mice. The gene expression profile of our IBC PDXEx model had a high degree of correlation to that of the original tumor. This suggests that the process of generating the PDXEx model did not significantly alter the molecular signature of the original tumor. We demonstrate a high degree of similarity in drug response profile between a PDX mouse model and our PDXEx model generated from the same original PDX tumor tissue and treated with the same panel of drugs, indicating that our PDXEx model had high predictive value in identifying effective tumor-specific therapies. Finally, we used our PDXEx model as a platform for a robotic-based high-throughput drug screen of a 386-drug anti-cancer compound library. The top candidates identified from this drug screen all demonstrated greater therapeutic efficacy than the standard-of-care drugs used in the clinic to treat triple-negative IBC, doxorubicin and paclitaxel. Our PDXEx model is simple, and we are confident that it can be incorporated into a PDX mouse system for use as a first-pass screening platform. This will permit the identification of effective tumor-specific therapies with high predictive value in a resource-, time-, and cost-efficient manner.

XIAP Regulation by MNK Links MAPK and NFκB Signaling to Determine an Aggressive Breast Cancer Phenotype

Hyperactivation of the NFκB pathway is a distinct feature of inflammatory breast cancer (IBC), a highly proliferative and lethal disease. Gene expression studies in IBC patient tissue have linked EGFR (EGFR/HER2)-mediated MAPK signaling to NFκB hyperactivity, but the mechanism(s) by which this occurs remain unclear. Here, we report that the X-linked inhibitor of apoptosis protein (XIAP) plays a central role in linking these two pathways. XIAP overexpression correlated with poor prognoses in breast cancer patients and was frequently observed in untreated IBC patient primary tumors. XIAP drove constitutive NFκB transcriptional activity, which mediated ALDH positivity (a marker of stem-like cells), in vivo tumor growth, and an IBC expression signature in patient-derived IBC cells. Using pathway inhibitors and mathematical models, we defined a new role for the MAPK interacting (Ser/Thr)-kinase (MNK) in enhancing XIAP expression and downstream NFκB signaling. Furthermore, targeted XIAP knockdown and treatment with a MNK inhibitor decreased tumor cell migration in a dorsal skin fold window chamber murine model that allowed for intravital imaging of local tumor growth and migration. Together, our results indicate a novel role for XIAP in the molecular cross-talk between MAPK and NFκB pathways in aggressive tumor growth, which has the potential to be therapeutically exploited.Significance: Signaling by the MNK kinase is essential in inflammatory breast cancer, and it can be targeted to inhibit XIAP-NFκB signaling and the aggressive phenotype of this malignancy. Cancer Res; 78(7); 1726-38. ©2018 AACR.

Scientific Summary from the Morgan Welch MD Anderson Cancer Center Inflammatory Breast Cancer (IBC) Program 10th Anniversary Conference

In 2006, a remarkable collaboration between University of Texas MD Anderson Cancer Center clinicians and Texas and New Mexico State legislators led to the formation of a dedicated IBC Research Program and Clinic at MD Anderson. This initiative provided funding and infrastructure to foster coordination of an IBC World Consortium of national and international experts, and launch the first ever IBC international conference in 2008, which brought together experts from around the world to facilitate collaborations and accelerate progress. Indeed great progress has been made since then. National and international experts in IBC convened at the 10^th Anniversary Conference of the MD Anderson IBC Clinic and Research Program and presented the most extensive sequencing analysis to date comparing IBC to non-IBC, gene- and protein-based immunoprofiling of IBC versus non-IBC patients, and converging lines of evidence on the specific role of the microenvironment in IBC. Novel models, unique metabolic mechanisms, and prominent survival pathways have been identified and were presented. Multiple clinical trials based on the work of the last decade are in progress or in development. The important challenges ahead were discussed. This progress and a coordinated summary of these works are presented herein.

EGFR signaling promotes inflammation and cancer stem-like activity in inflammatory breast cancer

Inflammatory breast cancer (IBC) is the most lethal and aggressive type of breast cancer, with a strong proclivity to metastasize, and IBC-specific targeted therapies have not yet been developed. Epidermal growth factor receptor (EGFR) has emerged as an important therapeutic target in IBC. However, the mechanism behind the therapeutic effect of EGFR targeted therapy is not well defined. Here, we report that EGFR regulates the IBC cell population that expresses cancer stem-like cell (CSC) markers through COX-2, a key mediator of inflammation whose expression correlates with worse outcome in IBC. The COX-2 pathway promoted IBC cell migration and invasion and the CSC marker-bearing population in vitro, and the inhibition of this pathway reduced IBC tumor growth in vivo. Mechanistically, we identified Nodal, a member of the TGFβ superfamily, as a potential driver of COX-2-regulated invasive capacity and the CSC phenotype of IBC cells. Our data indicate that the EGFR pathway regulates the expression of COX-2, which in turn regulates the expression of Nodal and the activation of Nodal signaling. Together, our findings demonstrate a novel connection between the EGFR/COX-2/Nodal signaling axis and CSC regulation in IBC, which has potential implications for new combination approaches with EGFR targeted therapy for patients with IBC.