Inflammatory Breast Cancer Samples Research Articles

Abstract PO5-06-02: Phase II Trial of Combination of Atezolizumab, Cobimetinib and Eribulin (ACE) or Atezolizumab and Eribulin (AE) in patients with metastatic inflammatory breast cancer (IBC): Clinical data of both cohorts

Abstract Background: Metastatic IBC is an unmet clinical need due to the aggressiveness of this breast cancer subtype. Gene expression analysis of IBC samples post-neoadjuvant chemotherapy has revealed that dysregulation of immune pathways is common in tumors that do not have a complete pathologic response (pCR) to chemotherapy. The immune checkpoint PD-L1 is expressed in a third of IBC cases, and the MEK inhibitor, cobimetinib, has been shown to enhance the expression of PD-L1, the target of atezolizumab. Taken together, dual targeted therapy with atezolizumab and cobimetinib is hypothesized to be synergistic. Eribulin is a standard of care chemotherapy used in patients who have progressed on anthracycline-taxane based regimens. Materials and Methods: Patients received triple or double combination therapy depending on the timing of their enrollment. Patients with metastatic IBC who had measurable disease after at least 1 standard regimen were eligible. Any receptor subtype was allowed, and PD-L1 positivity was not required. The study began with a single cohort (n=17 patients) receiving all 3 agents with a lead-in phase to determine the MTD of cobimetinib in this setting. The study was later amended to include only atezolizumab and eribulin (cohort 2). Ten patients were treated in cohort 2. The study closed early due to lack of efficacy in cohort 2 and the changing landscape of metastatic breast cancer therapies. In cohort 1, atezolizumab was given every 2 weeks (840 mg), cobimetinib was given at 60/40/20 mg once daily, and eribulin was given at 1.4mg/m2 on day 1 and day 8 of 21-day cycles. In cohort 2, atezolizumab was given every 3 weeks (1200 mg) during the PD window and cycles 1-4, and then every 4 weeks (1680 mg) during maintenance, and eribulin was given at 1.4mg/m2 on day 1 and day 8 of 21-day cycles. Results: The MTD of cobimetinib was 40mg. In cohort 1, 17 patients were treated, 14 had at least 1 restaging evaluation. Seven patients had a partial response (50%) and 3 stable disease. The cohort was predominantly triple receptor-negative (n=13/17), with a median age of 51 yrs. The median PFS for patients in cohort 1 was 6.2 months (0-54.1). There were 2 exceptional responders, both with triple negative subtype, one of whom remains on therapy for >4.5 years without evidence of disease. The median overall survival was 29.6 months (2.9-133). The AE profile was largely expected, with 3 irAEs (1 grade 5 colitis, and 2 grade 2 pneumonitis), and one other patient with cardiac dysfunction requiring discontinuation of cobimetinib and atezolizumab. The MTD of cobimetinib was 40 mg. Cobimetinib-related toxicities were mild and largely gastrointestinal tract related. In cohort 2, only 1 patient experienced PR, and the median PFS was 3 months (1.2-6.2) and overall survival 8.3 months (1.8-19.9). One patient experienced autoimmune related hepatitis requiring discontinuation of protocol therapy. Due to excesive myelosuppression, dose of erublin was reduced to 1.1 mg per meter squared on day 1 and 8 and pegfilgastrim was added on day 9< Conclusions: The response profile of the triple combination demonstrated promise, and suggests that MEK inhibition may warrant further investigation as a strategy in metastatic IBC in a larger sample size. However, there does not appear to be synergy between atezolizumab and eribulin without the addition of targeted therapy. Citation Format: Angela Alexander, Hope Murphy, James Reuben, H. T. Carisa Le-Petross, Deanna Lane, Monica Huang, Savitri Krishnamurthy, Yun Gong, Dan Gombos, Nimisha Patel, Richard Allen, Suyu Liu, Anisha Patel, Andrew Futreal, Ignacio Wistuba, Rachel Layman, Naoto Ueno, Debu Tripathy, Bora Lim, Vicente Valero. Phase II Trial of Combination of Atezolizumab, Cobimetinib and Eribulin (ACE) or Atezolizumab and Eribulin (AE) in patients with metastatic inflammatory breast cancer (IBC): Clinical data of both cohorts [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-06-02.

Inflammatory breast cancer biomarkers and biology.

Inflammatory breast cancer (IBC) is a unique breast cancer with a highly virulent course and low 5- and 10-year survival rates. Even though it only accounts for 1-5% of breast cancers it is estimated to account for 10% of breast cancer deaths annually in the United States. The accuracy of diagnosis and classification of this unique cancer is a major concern within the medical community. Early molecular and biological studies incidentally included IBC samples with other conventional breast cancers and were not informative as to the unique nature of the disease. Subsequent molecular studies that focused specifically on IBC demonstrated that IBC has a unique biology different from other forms of breast cancer. Additionally, a handful of unique signature genes that are hallmarks of IBC have also been suggested. Further understanding of IBC biology can help with diagnosis and treatment of the disease. The current article reviews the history and highlights of IBC studies.

Genomic and transcriptomic profiling of inflammatory breast cancers and non-inflammatory breast cancers in Asian women.

e12546 Background: Inflammatory breast cancer (IBC) is the most aggressive form of breast cancer. Despite its rare incidence, it accounts for 10% of breast cancer-caused mortality. Previous studies based on NGS have focused on western populations and found no common genomic and transcriptomic difference that could distinguish IBC from non-IBC. Methods: We performed WES on 15 IBC samples and their paired normal blood to identify somatic genomic alterations, copy number variants and large structural variants. RNA-seq was performed on 16 IBC samples to examine the RNA expression, pathway enrichment and gene fusions. WES and RNA-seq data were further investigated to discover genes that were dysregulated in both genomics and transcriptomics. For comparison, we performed WES and RNA-seq on 5 non-IBC samples and acquired additional 33 non-IBC samples of Asian women from the Cancer Genome Atlas Program (TCGA). Results: Apart from results similar to the previous reports in western IBC, ZNF74 and DYNC2H1 were identified as Asian-IBC-specific somatic mutations in our cohort. Elevated HRD mutational signature and scarHRD score indicated increased HRD events in Asian IBC patients. Structural variation analysis showed that deletions were found more frequent in IBC. RNA-seq indicated increased immune activation in IBC samples, but the immune cell infiltration within the tumor microenvironment were similar between IBC and non-IBC. Multiple gene fusions were more frequently found in IBC, including CTC-786C10.1—RP11-680G10.1, TULP4—RP11-732M18.3, RN7SL4P—RN7SL173P. Combined analysis of WES and RNA-seq showed more frequent mutation and increased pathway enrichment of RAS pathway in IBC, which may explain the aggressive biological behavior of IBC, inhibitors such as sorafenib, tipifarnib and trametinib targeting RAS signaling and its downstream pathways were predicted to possess promising effects in IBC treatment. Conclusions: Our study is the first to provide a complete genomic and transcriptomic landscape of IBC based on combined analysis of WES and RNA-seq and the first to focus on Asian women. We discovered intriguing differences unique in Asian women that could potentially explain IBC etiology and presented RAS signaling pathway as a potential therapeutic target in IBC treatment.

Copy Number Variation in Inflammatory Breast Cancer.

Identification of a unique genomic biomarker in de novo inflammatory breast cancer (IBC) may provide an insight into the biology of this aggressive disease. The goal of our study was to elucidate biomarkers associated with IBC. We examined breast biopsies collected from Dana-Farber Cancer Institute patients with IBC prior to initiating preoperative systemic treatment (30 samples were examined, of which 14 were eligible). Patients without available biopsies (n = 1), with insufficient tumor epithelial cells (n = 10), or insufficient DNA yield (n = 5) were excluded from the analysis. Molecular subtype and tumor grade were abstracted from a medical records' review. Ten IBC tumors were estrogen-receptor-positive (ER+) and human epidermal growth factor receptor 2 (HER2)-negative (n = 10 out of 14). Sufficient RNA and DNA were simultaneously extracted from 14 biopsy specimens using the Qiagen AllPrep Kit. RNA was amplified using the Sensation kit and profiled using the Affymetrix Human Transcriptome Array 2.0. DNA was profiled for genome-wide copy number variation (CNV) using the Affymetrix OncoScan Array and analyzed using the Nexus Chromosome Analysis Suite. Among the 14 eligible samples, we first confirmed biological concordance and quality control metrics using replicates and gene expression data. Second, we examined CNVs and gene expression change by IBC subtype. We identified significant CNVs in IBC patients after adjusting for multiple comparisons. Next, to assess whether the CNVs were unique to IBC, we compared the IBC CNV data to fresh-frozen non-IBC CNV data from The Cancer Genome Atlas (n = 388). On chromosome 7p11.2, we identified significant CN gain located at position 58,019,983-58,025,423 in 8 ER+ IBC samples compared to 338 non-IBC ER+ samples (region length: 5440 bp gain and 69,039 bp, False Discovery Rate (FDR) p-value = 3.12 × 10-10) and at position 57,950,944-58,025,423 in 3 TN-IBC samples compared to 50 non-IBC TN samples (74,479 base pair, gain, FDR p-value = 4.27 × 10-5; near the EGFR gene). We also observed significant CN loss on chromosome 21, located at position 9,648,315-9,764,385 (p-value = 4.27 × 10-5). Secondarily, differential gene expression in IBC patients with 7p11.2 CN gain compared to SUM149 were explored after FDR correction for multiple testing (p-value = 0.0016), but the results should be interpreted with caution due to the small sample size. Finally, the data presented are hypothesis-generating. Validation of CNVs that contribute to the unique presentation and biological features associated with IBC in larger datasets may lead to the optimization of treatment strategies.

Abstract P6-10-15: Targeting MARCKS in inflammatory breast cancer increased paclitaxel sensitivity

Abstract Background. Because of its high metastatic potential, inflammatory breast cancer (IBC) is the most lethal and aggressive form of breast cancer. We previously demonstrated that Myristoylated Alanine-Rich C Kinase Substrate (MARCKS) protein overexpression was associated with shorter metastasis-free survival (MFS) in IBC patients, but not in non-IBC (nIBC) patients. However, the mechanism of action of MARCKS and its particular association to poorer outcome in IBC compared to nIBC are poorly understood. Methods. We evaluated in vitro the inhibitory effect of MPS (MARCKS phosphorylation site domain), a peptide targeting MARCKS phosphorylation site domain (PSD) in single and in combination with paclitaxel treatment, on cell proliferation and cell motility in two cell lines of different phenotype (SUM149 for IBC and MDA-MB-231 for nIBC), as well as its distinct molecular mechanisms of action. We also assessed the clinical relevance of the protein expression of MARCKS and phosphatase and tensin homolog (PTEN) in a large series of IBC vs. nIBC patients. Results. In vitro, the treatment with MPS peptide impaired cell proliferation, migration, and invasion in SUM149 compared to MDA-MB-231 cells. More important, MARCKS inhibition increased paclitaxel sensitivity when using combination therapy in SUM149 cells compared to MDA-MB-231 cells. Interestingly, we could partially explain this specific inhibitory effect in IBC cells using western blot: MARCKS inhibition in single and in combination induced up and downregulation of the PTEN/AKT signaling pathway respectively in IBC compared to nIBC cells. Importantly, a negative correlation of MARCKS and PTEN was only found in the clinical IBC samples (180 patients) compared to nIBC samples (355 patients). More importantly, the group of patients with negative MARCKS and positive PTEN protein expression was associated to better 5-year MFS only in IBC patients. Conclusion. These results indicate two major findings: first, the important prognostic value of the negative correlation of MARCKS and PTEN expression in IBC patients, and second the specific role of MARCKS in regulating different downstream pathways and increasing the paclitaxel response in combination treatment in IBC compared to non-IBC. They suggest a potential IBC-specific targetable biomarker, the inhibition of which might impair disease aggressiveness and perhaps enhance patients’ survival. Citation Format: Maroua Manai, Ines Bini, Pascal Finetti, Haifa Bichiou, Carolina Reduzzi, Naziha Ben Hamida, Marc Lopez, Khaled Rahal, Karima Mrad, Mohamed Manai, Massimo Cristofanilli, Hamouda Boussen, Raoudha Doghri, Maher Kharrat, François Bertucci. Targeting MARCKS in inflammatory breast cancer increased paclitaxel sensitivity [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-10-15.

MARCKS as a Potential Therapeutic Target in Inflammatory Breast Cancer.

Inflammatory breast cancer (IBC) is the most pro-metastatic form of breast cancer (BC). We previously demonstrated that protein overexpression of Myristoylated Alanine-Rich C Kinase Substrate (MARCKS) protein was associated with shorter survival in IBC patients. MARCKS has been associated with the PI3K/AKT pathway. MARCKS inhibitors are in development. Our objective was to investigate MARCKS, expressed preferentially in IBC that non-IBC (nIBC), as a novel potential therapeutic target for IBC. The biologic activity of MPS, a MARCKS peptide inhibitor, on cell proliferation, migration, invasion, and mammosphere formation was evaluated in IBC (SUM149 and SUM190) and nIBC (MDA-MB-231 and MCF7) cell lines, as well as its effects on protein expression in the PTEN/AKT and MAPK pathways. The prognostic relevance of MARCKS and phosphatase and tensin homolog (PTEN) protein expression as a surrogate marker of metastasis-free survival (MFS) was evaluated by immunohistochemistry (IHC) in a retrospective series of archival tumor samples derived from 180 IBC patients and 355 nIBC patients. In vitro MPS impaired cell proliferation, migration and invasion, and mammosphere formation in IBC cells. MARCKS inhibition upregulated PTEN and downregulated pAKT and pMAPK expression in IBC cells, but not in nIBC cells. By IHC, MARCKS expression and PTEN expression were negatively correlated in IBC samples and were associated with shorter MFS and longer MFS, respectively, in multivariate analysis. The combination of MARCKS-/PTEN+ protein status was associated with longer MFS in IBC patient only (p = 8.7 × 10−3), and mirrored the molecular profile (MARCKS-downregulated/PTEN-upregulated) of MPS-treated IBC cell lines. In conclusion, our results uncover a functional role of MARCKS implicated in IBC aggressiveness. Associated with the good-prognosis value of the MARCKS-/PTEN+ protein status that mirrors the molecular profile of MPS-treated IBC cell lines, our results suggest that MARCKS could be a potential therapeutic target in patients with MARCKS-positive IBC. Future preclinical studies using a larger panel of IBC cell lines, animal models and analysis of a larger series of clinical samples are warranted in order to validate our results.

Characterization of the Immune Microenvironment in Inflammatory Breast Cancer Using Multiplex Immunofluorescence

Introduction: Inflammatory breast cancer (IBC) is an aggressive form of breast cancer with a poorly characterized immune microenvironment. Methods: We used a five-colour multiplex immunofluorescence panel, including CD68, CD4, CD8, CD20, and FOXP3 for immune microenvironment profiling in 93 treatment-naïve IBC samples. Results: Lower grade tumours were characterized by decreased CD4+ cells but increased accumulation of FOXP3+ cells. Increased CD20+ cells correlated with better response to neoadjuvant chemotherapy and increased CD4+ cells infiltration correlated with better overall survival. Pairwise analysis revealed that both ER+ and triple-negative breast cancer were characterized by co-infiltration of CD20 + cells with CD68+ and CD4+ cells, whereas co-infiltration of CD8+ and CD68+ cells was only observed in HER2+ IBC. Co-infiltration of CD20+, CD8+, CD4+, and FOXP3+ cells, and co-existence of CD68+ with FOXP3+ cells correlated with better therapeutic responses, while resistant tumours were characterized by co-accumulation of CD4+, CD8+, FOXP3+, and CD68+ cells and co-expression of CD68+ and CD20+ cells. In a Cox regression model, response to therapy was the most significant factor associated with improved patient survival. Conclusion: Those results reveal a complex unique pattern of distribution of immune cell subtypes in IBC and provide an important basis for detailed characterization of molecular pathways that govern the formation of IBC immune landscape and potential for immunotherapy.

Abstract P1-04-07: Xiap expression is associated with infiltration of cd163+ tumor-associated macrophages in the tumor micro-environment of inflammatory breast cancer

Abstract BACKGROUND: Inflammatory breast cancer (IBC) is a rare, but aggressive type of locally advanced breast cancer for which a specific immune response seems to be an important driver (Van Laere et al., CCR 2013). The tumor immune micro-environment (TIME) of IBC is characterized by an influx of tumor-associated macrophages (TAMs) and patients with spatial colocalization of TAMs with tumor cells seem to have a worse prognosis (Van Berckelaer et al., SABCS 2019). In contrast with TAMs, the presence of CD8+ T cells was associated with a better prognosis in IBC. Cytotoxic T cells mediate killing of the tumor by inducing apoptosis after activation of effector caspases-3/-7, regulated by the X-Linked Inhibitor of Apoptosis protein (XIAP). Recently, we reported that XIAP in breast cancer is associated with shorter survival and resistance to chemotherapy (Devi et al, Cancers 2021). In IBC, XIAP is translationally upregulated during cellular stress and induces, via NFkB, an immunosuppressive signaling (Evan et al, Cancer Res 2018). Therefore, we investigated the interplay between tumor cell driven XIAP expression and the TIME. METHODOLOGY: IBC patient clinicopathological variables (n=75) along with Affymetrix data (n=30/75) were collected. Immunostainings for XIAP, CD8 and CD163 (Hematoxylin-DAB) were done according to validated protocols. All slides were digitized and evaluated in Visiopharm to quantify the number of DAB+ immune cells and the relative marker area (RMA: the DAB+ area/total area of interest). Spatial interactions were examined using an effector index (EI) that counts the number of immune cells in a circle with a radius of 30 mcm around a CD8+ T cell or a tumor cell. We evaluated correlations between XIAP protein and mRNA expression, immune cell signatures (using CIBERSORT) & gene-expression pathways as a validation of our IHC findings. RESULTS: High XIAP expression was detected in 45.3% of the IBC samples (n= 34/75). Although, XIAP expression was not associated with any clinicopathological parameters like grade, molecular subtype, or disease stage. High XIAP expressing tumors had more sTIL infiltration (P= 0.008), PDL1 expression (P= 0.012) and infiltration with TAMs (RMA: 1.03% (0.03% – 5.97%) vs. 2.73% (0.01% – 11.3%), P= 0.003). Furthermore, in these XIAP high samples TAMs were also located closer to the tumor cells (EI: 0.95 cells (0.06 – 3.48) vs. 2.04 cells (0.28 – 5.20), P< 0.001) and the CD8+ T cells (EI: 2.85 cells (0.26 – 8.85) vs. 5.13 cells (0.87 – 10.16), P< 0.001), while there was no correlation between XIAP and the total number of CD8+ cells. Although gene expression data analysis did not reveal any correlation between protein and mRNA expression of XIAP, there was a significant correlation between XIAP activation signature and protein expression (P<0.001). Furthermore, we discovered a strong association between XIAP protein and cellular stress response- & inflammation-related gene sets. Finally, in the CIBERSORT data, we observed the strongest correlation between XIAP expression and M2 macrophages & activated dendritic cells. CONCLUSION: This is the first study showing high XIAP expressing IBC tumors have increased infiltration of immunosuppressive TAMs, which co-localized near tumor and cytotoxic T cells. We also demonstrated an association between XIAP protein expression and inflammation related & cellular stress response gene signatures. This is relevant as XIAP function depends on translational upregulation during cellular stress which leads to immunosuppressive signaling and an aggressive breast cancer phenotype. XIAP antagonists are in clinical trials and these data suggest potential benefit in targeting XIAP to enhance immunotherapeutic efficacy in IBC therapy. FUNDING: DoDs-W81XWH-17-1-0297,W81XWH-20-1-0153, ACS Mission Boost Grants(GRD) Citation Format: Christophe Van Berckelaer, Steven Van Laere, Joseph Gerardts, Luc Dirix, Michael Morse, Mark Kockx, François Bertucci, Peter Van Dam, Gayathri R Devi. Xiap expression is associated with infiltration of cd163+ tumor-associated macrophages in the tumor micro-environment of inflammatory breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-04-07.

Robust inflammatory breast cancer gene signature using nonparametric random forest analysis

Inflammatory breast cancer (IBC) is a rare, aggressive cancer found in all the molecular breast cancer subtypes. Despite extensive previous efforts to screen for transcriptional differences between IBC and non-IBC patients, a robust IBC-specific molecular signature has been elusive. We report a novel IBC-specific gene signature (59 genes; G59) that achieves 100% accuracy in discovery and validation samples (45/45 correct classification) and remarkably only misclassified one sample (60/61 correct classification) in an independent dataset. G59 is independent of ER/HER2 status, molecular subtypes and is specific to untreated IBC samples, with most of the genes being enriched for plasma membrane cellular component proteins, interleukin (IL), and chemokine signaling pathways. Our finding suggests the existence of an IBC-specific molecular signature, paving the way for the identification and validation of targetable genomic drivers of IBC.

Gene expression profiles of inflammatory breast cancer reveal high heterogeneity across the epithelial-hybrid-mesenchymal spectrum

Inflammatory breast cancer (IBC) is a highly aggressive breast cancer that metastasizes largely via tumor emboli, and has a 5-year survival rate of less than 30%. No unique genomic signature has yet been identified for IBC nor has any specific molecular therapeutic been developed to manage the disease. Thus, identifying gene expression signatures specific to IBC remains crucial. Here, we compare various gene lists that have been proposed as molecular footprints of IBC using different clinical samples as training and validation sets and using independent training algorithms, and determine their accuracy in identifying IBC samples in three independent datasets. We show that these gene lists have little to no mutual overlap, and have limited predictive accuracy in identifying IBC samples. Despite this inconsistency, single-sample gene set enrichment analysis (ssGSEA) of IBC samples correlate with their position on the epithelial-hybrid-mesenchymal spectrum. This positioning, together with ssGSEA scores, improves the accuracy of IBC identification across the three independent datasets. Finally, we observed that IBC samples robustly displayed a higher coefficient of variation in terms of EMT scores, as compared to non-IBC samples. Pending verification that this patient-to-patient variability extends to intratumor heterogeneity within a single patient, these results suggest that higher heterogeneity along the epithelial-hybrid-mesenchymal spectrum can be regarded to be a hallmark of IBC and a possibly useful biomarker.

Abstract B035: Identification of a tumor cell adaptive stress response signaling pathway, which drives aggressive breast cancer phenotype and therapeutic resistance, in African American patients with locally advanced breast cancer subtypes

Abstract Introduction: The higher incidence of biologically aggressive and treatment-resistant breast cancer (BCa) subtypes, which includes triple negative (TN), basal, and inflammatory breast cancer (IBC), contributes to worse survival outcomes in African American/AA patients, 42% higher death rate compared to White BCa. Amongst locally advanced BCa, IBC is a model of aggressive, most lethal, frequently basal/TN, accounting for 10% AA BCa and disparity in outcomes exist after adjusting for socioeconomic and diagnosis factors. IBC exhibits a unique phenotype wherein malignant cells do not form solid masses and instead, present as hyperproliferative tumor cell clusters, termed tumor emboli, in the skin and lymphatics. Our key finding was the identification of a tumor cell adaptive stress response pathway linking the mitogen activated ser/thr kinase/MNK, X-linked inhibitor of anti-apoptotic protein, XIAP, and nuclear transcription factor, NFkB, mediated proliferative, invasive and immunosuppressive signaling. Our goal was to determine the role of the adaptive stress response pathway, which we have identified to contribute to aggressiveness of TNBC and IBC, in AA breast tumor biology. Methods: Expression of MNK, XIAP and NFkB target gene sets, a 40-gene oxidative stress response that correlates with response to cell death stimuli and a 79-gene IBC signature (identified from comparative analysis of IBC and non-IBC biospecimens) were evaluated in The Cancer Genome Atlas (TCGA) breast cancer datasets (1109 tumor; 113 normal) stratified according to race and molecular subtypes (luminal A, B, Her2, basal). The mean expression for each gene in these signatures were also assessed among different subtypes and race using R. Gene Ontology (GO) analysis was performed using GATHER online tool. XIAP immunohistochemistry (IHC) conducted in BCa samples (n=93) from Duke and MDACC biorepositories. Results: TCGA analysis of the IBC-related signatures identified genes differentially expressed (>2-fold change; Wilcoxon rank sum test, FDR<0.05) among BCa subtypes and between AA vs White within a subtype. Additionally, the oxidative stress response metagene was significantly upregulated in AA basal (p=0.037) whereas there were fewer differences in immune-related genes within AA subtypes suggesting attenuated immune response. IHC, to date, shows high XIAP in high grade, ER-negative and in majority of AA BCa and in IBC samples independent of molecular subtypes and grade. Conclusions: We report a heightened adaptive stress response gene signature and identify genes in the MNK:XIAP:NFkB pathway and IBC-related signatures in AA BCa, suggesting potential biomarkers and drug discovery targets. High XIAP expression in high grade BCa, frequent in AA patients, is of therapeutic relevance as XIAP, the most potent caspase inhibitor, is linked to chemo- and immunotherapy resistance and XIAP inhibitors are in clinical trials. Supported by DOD-Breakthrough-W81XWH-17-1-0297; Duke SOM bridge funds; NCI-1P20-CA202925-01A12. Citation Format: Gayathri R Devi, Muthana Al Abo, Larisa Gearhart-Serna, Joseph Geradts, Shannon J McCall, Savitri Krishnamurthy. Identification of a tumor cell adaptive stress response signaling pathway, which drives aggressive breast cancer phenotype and therapeutic resistance, in African American patients with locally advanced breast cancer subtypes [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr B035.

NOTCH and DNA repair pathways are more frequently targeted by genomic alterations in inflammatory than in non-inflammatory breast cancers.

Inflammatory breast cancer (IBC) is the most pro‐metastatic form of breast cancer. Better understanding of its pathophysiology and identification of actionable genetic alterations (AGAs) are crucial to improve systemic treatment. We aimed to define the DNA profiles of IBC vs noninflammatory breast cancer (non‐IBC) clinical samples in terms of copy number alterations (CNAs), mutations, and AGAs. We applied targeted next‐generation sequencing (tNGS) and array‐comparative genomic hybridization (aCGH) to 57 IBC and 50 non‐IBC samples and pooled these data with four public datasets profiled using NGS and aCGH, leading to a total of 101 IBC and 2351 non‐IBC untreated primary tumors. The respective percentages of each molecular subtype [hormone receptor‐positive (HR+)/HER2−, HER2+, and triple‐negative] were 68%, 15%, and 17% in non‐IBC vs 25%, 35%, and 40% in IBC. The comparisons were adjusted for both the molecular subtypes and the American Joint Committee on Cancer (AJCC) stage. The 10 most frequently altered genes in IBCs were TP53 (63%), HER2/ERBB2 (30%), MYC (27%), PIK3CA (21%), BRCA2 (14%), CCND1 (13%), GATA3 (13%), NOTCH1 (12%), FGFR1 (11%), and ARID1A (10%). The tumor mutational burden was higher in IBC than in non‐IBC. We identified 96 genes with an alteration frequency (p < 5% and q < 20%) different between IBC and non‐IBC, independently from the molecular subtypes and AJCC stage; 95 were more frequently altered in IBC, including TP53, genes involved in the DNA repair (BRCA2) and NOTCH pathways, and one (PIK3CA) was more frequently altered in non‐IBC. Ninety‐seven percent of IBCs displayed at least one AGA. This percentage was higher than in non‐IBC (87%), notably for drugs targeting DNA repair, NOTCH signaling, and CDK4/6, whose pathways were more frequently altered (DNA repair) or activated (NOTCH and CDK4/6) in IBC than in non‐IBC. The genomic landscape of IBC is different from that of non‐IBC. Enriched AGAs in IBC may explain its aggressiveness and provide clinically relevant targets.

Abstract P4-04-04: The mutational profile of inflammatory breast cancer reveals a higher mutational burden leading to MAPK activation and chromatin remodeling

Abstract Introduction. Inflammatory breast cancer (IBC) is an aggressive form of locally advanced breast cancer with increased metastatic potential. In the past, we have identified a gene expression profile that characterizes IBC, suggesting that a specific molecular biology underpins this devastating disease. Here, we explore the hypothesis that the molecular portrait of IBC is a reflection of underlying genomic alterations. Materials and Methods. Mutation and copy number variation (CNV) profiles for 663 genes were assembled from 2.352 publicly available primary tumor samples (subtype distribution: 1.520 HR+, 355 HER2+, 414 TNBC and 190 unassigned) including 127 profiles from patients with IBC. Gene-wise differences in the frequency of genomic aberrations between patients with and without IBC, stratified per subtype, were investigated using Chi-square testing with adjustment for multiple comparisons. Genomic perturbation differences of pathways and processes, represented by KEGG or Gene Ontology gene sets, were evaluated by collapsing mutation and CNV profiles across all genes associated with the respective gene sets. Finally, mutational signature (MS) profiles were calculated and compared between patients with and without IBC. Results. Seventy-six genes showed evidence of more extensive genomic alterations in samples from patients with IBC as compared to those without IBC (i.e. false discovery rate &amp;lt; 10%), whereas only 3 genes reveal the opposite pattern. Genes mutated in more than 15% (range 16.2% - 63,5%) of the IBC samples include: AXIN1, ERBB2, ERBB3, CBL, CTNNB1, CYP2D6, FGFR1, INSR, KIT, KMT2A, LRP1B, MYC, PBRM1, SACS, SMAD4, TP53 and ZNF217. Analysis of MS profiles revealed differences for signature 1 (i.e. age-related deamination of 5-methylcytosine), 2 (i.e. APOBEC3 activity), 3 (i.e. defective homologuous recombination), 11 (i.e. alkylating agents), 20 (i.e. DNA mismatch repair) and 24 (i.e. aflatoxin), of which MS 11 and 24 are more active in IBC. When evaluating the same panel of genes in TNBC only, 28 genes were retained, suggesting data are confounded by the subtype distribution. Pathway analysis revealed genomic perturbation of MAPK signaling and chromatin organizational processes in respectively 55% and 74% of TN IBCs. Discussion. These data suggest that IBC is characterized by an extensive mutational burden that results, amongst others in the activation of MAPK signaling as well as chromatin remodeling. The analysis of MS profiles does not provide a clear biological explanation for the increased frequency of genomic alterations in IBC, with APOBEC3 activity, defective homologous recombination, defective DNA mismatch repair and age-related deamination of 5-methylcytosinie all being more prominent in nIBC samples. Notably, the lower frequency of age-related C&amp;gt;T transitions is in line with younger age at diagnosis typical for patients with IBC. Citation Format: Van Laere S, Finetti P, Rypens C, Billet C, Birnbaum D, Vermeulen P, Viens P, Dirix L, Bertucci F. The mutational profile of inflammatory breast cancer reveals a higher mutational burden leading to MAPK activation and chromatin remodeling [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-04-04.

Abstract P5-17-01: Patient-derived organoid models of inflammatory breast cancer

Abstract Background: Inflammatory Breast Cancer (IBC) is an aggressive subtype of breast cancer that is associated with an increased likelihood of early metastasis and a poor prognosis, accounting for approximately 10% of all breast cancer mortality. Currently, there is limited availability of cell line and patient-derived xenograft (PDX) models of IBC. As a result, there is an urgent need for additional model systems to facilitate our understanding of this disease. Organoids have been used to grow breast cancer cells with high efficiency, resulting in long-term cultures with genetic and phenotypic stability; however, the extent to which IBC can be modeled using this system is unknown. We undertook an evaluation of organoid culture technology for growing IBC patient samples, with the goal of generating a model of IBC that more faithfully recapitulates the key features of the disease. Methods: Tumor samples (taken from lumpectomy, mastectomy, PDX, or core biopsy samples), were digested to the organoid level using collagenase, and were grown in three dimensional cultures using a basement membrane extract and a fully-defined organoid medium, as described (Sachs et al. Cell 2018). First, we surveyed non-IBC metastatic breast cancer samples to determine the efficiency of growth of multiple breast cancer subtypes under these conditions. Then, we assessed the efficiency of growth of IBC samples taken after treatment, at the time of mastectomy. Co-culture experiments in which IBC organoids were grown in the presence of human endothelial cells were performed in three dimensional culture using a mixture of type I collagen and basement membrane extract. Results: Our success rate for establishing organoid cultures from breast cancer samples in general was 75% (33 out of 44 samples), and for triple-negative breast cancers, the success rate for establishment of organoid cultures was 100% (14 out of 14 samples). Expansion of ER+ tumor organoids (16 of 26 samples) was primarily restricted by a slow growth rate in culture, as compared to triple-negative tumor organoids. We were able to establish 12 breast cancer organoids from core biopsies of multiple metastatic sites, including brain, liver, bone, breast, and skin. We subsequently were able to establish organoid cultures from five out of five IBC tumor samples. Our IBC organoids preserved histopathologic features of the original tumor, and expressed key markers, such as E-cadherin, that are known to be associated with IBC. In addition, our IBC organoids interacted with human endothelial cells under co-culture conditions designed to model lymphovascular invasion, an essential feature of IBC. Conclusion: We have shown that organoid cultures can be established to propagate IBC tumors with high efficiency, preserve key pathologic features of IBC in vitro, and model interactions between tumor cells and the microenvironment. Thus, organoids are useful complements to existing IBC models, and can be used to identify potential therapeutic vulnerabilities associated with this particularly aggressive breast cancer subtype. Citation Format: Rosenbluth JM, Zervantonakis I, Boedicker M, Wagle N, Dillon D, Nakhlis F, Brugge JS, Overmoyer B. Patient-derived organoid models of inflammatory breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-17-01.

Mammary stem cell and macrophage markers are enriched in normal tissue adjacent to inflammatory breast cancer.

We hypothesized that breast tissue not involved by tumor in inflammatory breast cancer (IBC) patients contains intrinsic differences, including increased mammary stem cells and macrophage infiltration, which may promote the IBC phenotype. Normal breast parenchyma ≥ 5cm away from primary tumors was obtained from mastectomy specimens. This included an initial cohort of 8 IBC patients and 60 non-IBC patients followed by a validation cohort of 19 IBC patients and 25 non-IBC patients. Samples were immunostained for either CD44+CD49f+CD133/2+ mammary stem cell markers or the CD68 macrophage marker and correlated with IBC status. Quantitation of positive cells was determined using inForm software from PerkinElmer. We also examined the association between IBC status and previously published tumorigenic stem cell and IBC tumor signatures in the validation cohort samples. 8 of 8 IBC samples expressed isolated CD44+CD49f+CD133/2+ stem cell marked cells in the initial cohort as opposed to 0/60 non-IBC samples (p = 0.001). Similarly, the median number of CD44+CD49f+CD133/2+ cells was significantly higher in the IBC validation cohort as opposed to the non-IBC validation cohort (25.7 vs. 14.2, p = 0.007). 7 of 8 IBC samples expressed CD68 + histologically confirmed macrophages in initial cohort as opposed to 12/48 non-IBC samples (p = 0.001). In the validation cohort, the median number of CD68 + cells in IBC was 3.7 versus 1.0 in the non-IBC cohort (p = 0.06). IBC normal tissue was positively associated with a tumorigenic stem cell signature (p = 0.02) and with a 79-gene IBC signature (p < 0.001). Normal tissue from IBC patients is enriched for both mammary stem cells and macrophages and has higher association with both a tumorigenic stem cell signature and IBC-specific tumor signature. Collectively, these data suggest that IBC normal tissue differs from non-IBC tissue. Whether these changes occur before the tumor develops or is induced by tumor warrants further investigation.

Abstract P2-02-04: Circulating protein biomarker profile for inflammatory breast cancer using a multiplexed proximity extension assay

Abstract Background: Expression of cancer related genes and proteins in clinical specimens are the mainstay of personalized targeted therapy; however, a diagnostic signature for inflammatory breast cancer (IBC) remains elusive. In this study, we employed a blood-based, non-invasive, sensitive technology to map biomarkers in patients with IBC at the protein level. Proximity Extension Assay consists of a harmonious blending of immunoassay and PCR to amplify protein expression signal, thereby enabling multiplexing with small sample input (1 μl). Other multi-platform assays require a large amount of clinical material, multi-step sample processing and complicated data analysis. Materials and methods: Serum samples (n= 159) from patients with primary IBC (IBC, n= 30), metastatic IBC (MIBC, n= 54), locally advanced breast cancer (LABC, n= 24) and metastatic breast cancer (MBC, n= 27) were prospectively collected from subjects prior to starting a new therapy (treatment naive) or a new line of therapy between 2009 and 2012. Sera from 24 healthy normal donors (HD) were included in the analysis for comparison. The samples were analyzed using two panels: Proseek Multiplex Oncology II and Proseek Multiplex Inflammation I (Olink Proteomics, Uppsala, Sweden) for simultaneous detection of 92 human protein biomarkers in each panel. In the assay, each protein biomarker is detected by a matched pair of antibodies coupled to unique DNA-tags. Upon binding to the proteins, the correctly hybridized DNA-tags form an amplicon that can be measured by PCR.For initial analysis, sample populations were compared using the Mann-Whitney-U test. Results: In comparison with HD sera, sera of breast cancer patients had 41 proteins from the oncology panel and 28 from the inflammation panel that were significantly higher, whereas 5 from the inflammation panel were significantly lower. From the inflammation panel, 11 proteins (PD-L1, IL-2, IL-7, IL-18, uPA, CCL4, CCL23, CXCL9, CXCL10, CXCL11 and TNF-alpha) showed significant differential expression between IBC and non-IBC derived samples (irrespective of metastatic status); for each marker, levels were higher in IBC than in non-IBC. In contrast, 9 proteins from the oncology panel (CRNN, CTSV, ERBB4, FR-gamma, ITGAV, MIA, PODXL, SCF and SEZ6L) were differentially expressed; however, each of these proteins was higher in non-IBC than in IBC. Among the aforementioned proteins, CCL4, IL-2, IL-7, PD-L1, TNF-alpha, uPA, CRNN, CTSV, FR-gamma, ITGAV, MIA, SCF and SEZ6L did not differentiate cancer and HD, but were uniquely characteristic of the IBC vs non-IBC comparison. Conclusion: These preliminary data suggest that it is possible to distinguish between cancer patients and healthy normal donors, and also to delineate between IBC and non-IBC patients based on expression of serum proteins. Validation of this serum protein signature is planned in a larger patient cohort. Citation Format: Cohen EN, Jayachandran G, Gao H, Tin S, Alvarez RH, Valero V, Lim B, Woodward WA, Ueno NT, Reuben JM. Circulating protein biomarker profile for inflammatory breast cancer using a multiplexed proximity extension assay [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-02-04.

Inflammatory breast cancer: High incidence of GCC haplotypes (-1082A/G, -819T/C, and -592A/C) in the interleukin-10 gene promoter correlates with over-expression of interleukin-10 in patients' carcinoma tissues.

Interleukin-10 is involved in carcinogenesis by supporting tumor escape from the immune response. The aim of this study was to assess the single nucleotide polymorphisms, -1082A/G, -819T/C and -592A/C, in interleukin-10 gene promoter in inflammatory breast cancer compared to non-inflammatory breast cancer and association of these polymorphisms with interleukin-10 gene expression. We enrolled 105 breast cancer tissue (72 non-inflammatory breast cancer and 33 inflammatory breast cancer) patients and we determined the three studied single nucleotide polymorphisms in all samples by polymerase chain reaction restriction fragment length polymorphism and investigated their association with the disease and with various prognostic factors. In addition, we assessed the expression of interleukin-10 gene by real-time quantitative reverse transcription polymerase chain reaction and the correlation between studied single nucleotide polymorphisms and interleukin-10 messenger RNA expression. We found co-dominant effect as the best inheritance model (in the three studied single nucleotide polymorphisms in non-inflammatory breast cancer and inflammatory breast cancer samples), and we didn't identify any association between single nucleotide polymorphisms genotypes and breast cancer prognostic factors. However, GCC haplotype was found highly associated with inflammatory breast cancer risk (p < 0.001, odds ratio = 43.05). Moreover, the expression of interleukin-10 messenger RNA was significantly higher (p < 0.001) by 5.28-fold and 8.95-fold than non-inflammatory breast cancer and healthy control, respectively, where GCC haplotype significantly increased interleukin-10 gene expression (r = 0.9, p < 0.001).

Abstract P1-05-01: Landscape of somatic mutations in inflammatory breast cancer whole-genome sequences

Abstract Goal: Inflammatory breast cancer (IBC) is a rare, aggressive form of breast cancer that is characterized by a highly metastatic phenotype. Numerous previous attempts failed to identify, recurrent, IBC-specific gene expression or DNA copy number alterations. We performed whole genome sequencing (WGS) of IBC biopsies obtained before any therapy to define a comprehensive genomic landscape of this disease. Methods: Illumina paired-end whole genome sequencing (WGS) of 20 IBC (n=9 ER+, n=11 ER-) and matched normal samples were performed with median coverage of 60X and 40X for cancer and normal, the percentages of mapped reads were 99.3% and 99.2%, respectively. We identified germ-line and somatic variants, indels as well as large scale structural variants, using GATK Haplotype Caller, MuTect and CREST, respectively. We performed the same analysis on WGS data from 23, age, race and ER and HER2 matched, non-IBC (n=12 ER+, n=11 ER-) from the TCGA for comparison. Variants in both coding and noncoding sequences were categorized by FunSeq to identify potential drivers. Mutation clustering in each gene, as well as significantly mutated non-coding regulatory modules, were identified using LARVA. DeconstructSigs were used to decompose the mutational spectrum of each cancer into 30 validated, mutational signatures provided by COSMIC. Contributions of each validated signature to mutations in IBC vs. non-IBC were compared using Welch's t-test. Results: We identified 118,818 somatic variants in the IBC samples (median: 3,856; minimum: 1,109; maximum: 24,815) including 1,060 variants (~0.9%) in coding regions. 5,287 somatic indels and 5,959 large scale structural variants were detected including 1,028 insertions and 1,857 deletions. Recurrent, non-synonymous mutations were detected in the coding region of GRIN2A gene in 3/20 IBC samples (15%), (previously reported as a potential driver mutation in 1.7% of breast cancers). Other significant mutations in coding regions included GRHL1, PIK3R2, ESR1, FLG2 and etc. Three DNase I hypersensitive sites (DHSs) in non-coding regions were altered in 20% (4/20) IBC samples vs. fewer than 8.7% (2/23) in non-IBC. Mutational frequency of GATA3 is 80.0% vs. 47.8% (p=0.03), and PTEN is 45.0% vs. 73.9% (p=0.05), in IBC vs. non-IBC samples when including both coding and non-coding variants. Contributions of mutational signature 9, that is associated with polymerase η , were significantly higher in IBC cohort than non-IBC cohort (p-value=0.056). Conclusion: This is the first whole genome sequencing analysis of IBC and comparison with the results from non-IBC. We identified promising candidate drivers in the coding sequence and in non-coding regulatory modules of expressed genes. We also identified mutational signature 9, and mutations in several DHS as significantly more frequent alterations in IBC compared to non-IBC. Citation Format: Li X, Krishnamurthy S, Kumar S, Reddy S, Woodward W, Reuben J, Hatzis C, Ueno NT, Gerstein M, Pusztai L. Landscape of somatic mutations in inflammatory breast cancer whole-genome sequences [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-05-01.

Abstract P4-03-14: Stem cell and macrophage markers are enriched in normal tissue adjacent to inflammatory breast cancer

Abstract Introduction: We hypothesized that normal breast tissue in inflammatory breast cancer (IBC) patients contains intrinsic differences, including increased mammary stem cells and macrophage infiltration, which may promote the IBC phenotype. Materials and Methods: Normal breast tissue at least 5cm away from primary tumors were obtained from mastectomy specimens. This included an initial cohort of 8 IBC patients and 60 non-IBC patients followed by a validation cohort of 19 IBC patients and 25 non-IBC patients. Samples were immunostained for either CD44+CD49f+CD133/2+ stem cell markers or the CD68 macrophage marker and correlated with IBC status. Automated quantitation of positive cells was employed for the validation cohort. We also examined the association between IBC status and previously published tumorigenic stem cell and IBC tumor signatures in the validation cohort samples. Results: 8 of 8 IBC normal tissue samples expressed CD44+CD49f+CD133/2+ stem cell markers in the initial cohort as opposed to 0/60 non-IBC normal tissue samples (p=0.001). Similarly, the median number of CD44+CD49f+CD133/2+ cells was 25.7 in the IBC validation cohort as opposed to 14.2 in the non-IBC validation cohort (p=0.007). 7 of 8 IBC samples expressed CD68+ macrophages in initial cohort as opposed to 12/48 non-IBC samples (p=0.001). In the validation cohort the median number of CD68+ cells was 3.7 in the IBC cohort vs 1.0 in the non-IBC cohort (p=0.06). Normal tissue of IBC patients was positively associated with a tumorigenic stem cell signature (p=0.02) and with a 79-gene IBC gene signature (p&amp;lt;0.001). Conclusions: Normal tissue from IBC patients is enriched for both mammary stem cells and macrophages. Further, normal tissue of IBC patients has higher association with both a tumorigenic stem cell signature and IBC-specific tumor signature. Collectively, these data suggest that normal tissue from IBC patients is distinct from non-IBC normal tissue and may support the hypothesis that a primed normal breast contributes to the development of IBC symptoms upon oncogenic insult. Validation of these results in additional normal tissue in cancer-free women would better determine causality. Citation Format: Reddy JP, Atkinson RL, Larson RA, Burks JK, Smith D, Debeb BG, Ruffell B, Creighton C, Reuben JM, Krishnamurthy S, Symmans WF, Brewster A, Van Laere SJ. Stem cell and macrophage markers are enriched in normal tissue adjacent to inflammatory breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-03-14.

Abstract B44: Immune pathway dysregulations in inflammatory breast cancer health disparity

Abstract Background: Inflammatory breast cancer (IBC) is a distinct, aggressive and the most lethal form of breast cancer. Furthermore, data from population-based registries, when stratified by race and compared to other locally advanced breast cancers, suggest that IBC has a disproportionately high incidence, prevalence &amp; shorter median survival time in African Americans (AA) compared to Caucasian American (CA) patients. IBC health disparities that are independent of external factors like differences in income, screening rates, and access to health care suggest a biological component to poor outcomes. IBC pathobiology is also unique wherein instead of a solid tumor, tightly packed tumor cell clusters/emboli are formed with a propensity for lymphatic dissemination. The underlying mechanisms for this extremely aggressive breast cancer phenotype are largely unknown and, therefore, present a major impediment to identifying the molecular underpinnings for health disparities in IBC patients. Methods and Results: In order to understand how IBC cells evade cell death signals in the host microenvironment, we conducted comparative analysis of the largest collection of untreated primary tumor samples of IBC (N=137), along with stage- and subtype-matched non-IBC (N=252) and normal breast tissue. Results reveal that pretreatment tumor tissue samples from IBC patients have a heightened expression of adaptive stress response genes comprised of high levels of the nuclear transcription factor, NFkappaB, and its target genes in the anti-apoptotic and immune/inflammatory pathways that correlate with cell survival. In addition, guided by analysis based on presence of tumor infiltrating leukocytes in IBC (N=69) and non-IBC (N=62) patient samples, we have identified a set of pathways and genes that have the ability to distinguish the immune responses in IBC and non-IBC patients in a subtype independent manner. In particular, interferon alpha/beta and NFκB signaling pathways were differentially regulated in IBC vs. non-IBC. Gene expression driven analysis of enrichment of leukocyte subsets reveal specific differences in plasma cells and effector memory CD8 cells in IBC bulk tumor samples. Preliminary data analysis of gene expression data sets from laser microdissected epithelium and stromal compartments of AA and CA breast cancer patients also show enrichment of plasma cells, effector memory CD4+, and M1 macrophages. Studies are ongoing to characterize these immune profiles that are unique and distinguishable in IBC patients and further identify race-related differences. Most importantly, we discovered that the constitutive NFκB hyperactivation observed in IBC tumor cells is driven by stress-mediated translational upregulation of the most potent anti-apoptotic protein, XIAP. Interestingly, XIAP:NFκB overexpressing cells are highly resistant to immunotherapy mediated cell death. These data strongly suggest that in IBC, host immune phenotype promotes outgrowth of cell death resistant population and specific tumor cell pro-survival signaling mechanisms that enhances invasion and lymphatic dissemination. We have developed novel in vitro IBC tumor emboli culture model and a transgenic mouse bearing red fluorescent lymphatic vasculature that allow recapitulating host factors to define tumor cell signaling mechanisms on immune effector function and the resultant invasive phenotype. Conclusions: As the incidence is rising and targets for therapy are scant, IBC has the potential to become a major public health disparity concern. This study reveals that the immune factors in the host microenvironment may interact with underlying IBC genetics to promote the aggressive nature of the tumor, and more specifically, these factors may be one of the sources of biologic variation between patients of different ethnicities leading to IBC disparity outcomes. Supported in part by Duke IBC Consortium, DCI NIH CAO14236 development funds (GRD), DoD W81XWH-13-1-0047 (GRD). Citation Format: Gayathri R. Devi, Eun-Sil Shelley Hwang, John Stewart, Michael A. Morse, Steven Van Laere. Immune pathway dysregulations in inflammatory breast cancer health disparity. [abstract]. In: Proceedings of the Ninth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2016 Sep 25-28; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(2 Suppl):Abstract nr B44.