Abstract P5-08-13: NDRG1 expression is an independent prognostic factor in inflammatory breast cancer

Background: Inflammatory breast cancer (IBC) is a rare and highly aggressive form of breast cancer. Patients with IBC still have worse clinical outcomes compared to patients with non-IBC (40% versus 63% for 5 years overall survival, respectively) despite advances in breast cancer treatment. IBC remains a poorly characterized disease lacking specific therapeutic targets and prognostic biomarkers. Our group demonstrated that N-myc downstream regulated gene 1 (NDRG1) is crucial in promoting tumorigenesis and brain metastasis in mouse models of IBC. Our hypothesis is that NDRG1 is a prognostic marker associated with poor outcome in IBC patients. Methods: 64 IBC patients in a tissue microarray were evaluated by immunohistochemical staining with anti-NDRG1 primary antibody and NDRG1 levels were quantified. Using the median value, 32 patients were grouped as NDRG1-low (≤ median), and 32 as NDRG1-high (>median). Survival data were compared by Kaplan–Meier curves and log-rank test. Results: The average age of patients was 50 years. Sixty-two percent of patients had estrogen receptor (ER)-negative tumors, 83% were stage III, 80% high grade, and 67% of these patients received adjuvant radiation. The median follow-up time for the patients studied was 11.7 years, and the median overall survival (OS) time was 3.7 years. On univariate analysis, NDRG1 expression, tumor grade, disease stage, ER status, and adjuvant radiation therapy were associated with OS and disease specific survival (DSS). Patients with NDRG1-low tumors experienced better actuarial 10-year OS (p=0.0129) and DSS (p=0.0074), and showed significant higher 10-year OS and DSS rates than patients with NDRG1-high(OS, 45% vs. 19%, p=0.0278; DSS, 52% vs. 22%, p=0.0139). The median OS and DSS times were shorter for NDRG1-high patients (OS, 2.5 years; DSS, 3.1 years) than for NDRG1-low patients (OS, 5.9 years; DSS, 10.7 years). Multivariable analysis, NDRG1 was an independent predictor of OS (hazard ratio [HR]=2.449, p=0.0274) and DSS (HR=2.727, p=0.0039). ER status, disease stage and adjuvant radiation were also independent predictor for both OS and DSS. Furthermore, we observed that NDRG1-high expressing ER-negative tumors exhibit worse outcome in IBC patients (OS, p=0.0003; DSS, p=0.0003). NDRG1-high expression correlated with worse outcome in patients that received adjuvant radiation treatment (OS, p=0.0088; DSS, p=0.0093), and those with stage III (OS, p=0.0450; DSS, p=0.0239). Conclusions: Our findings demonstrated that NDRG1 is positively correlated with aggressive tumor characteristics in IBC and that it is an independent prognostic factor for OS and DSS in IBC patients, suggesting that targeting NDRG1 may provide a novel therapeutic strategy to improve outcomes for patients with IBC. Our data further suggests that NDRG1 warrants further investigation in radiation response.

Citation Format: Emilly Schlee Villodre, Yun Gong, Xiaoding Hu, Lei Huo, Esther C Yoon, Naoto T Ueno, Wendy A Woodward, Debu Tripathy, Juhee Song, Bisrat G Debeb. NDRG1 expression is an independent prognostic factor in 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 P5-08-13.

SPDL1 Is an Independent Predictor of Patient Outcome in Colorectal Cancer

Spindle Apparatus Coiled-Coil Protein 1 (SPDL1) is a relatively recently identified coiled-coil domain containing protein and an important determinant of DNA fidelity by ensuring faithful mitosis. Hence, SPDL1 is suspected to underlie genomic (in-)stability in human cancers, yet its exact roles in these diseases remain largely underexplored. Given that genomic instability (GIN) is a crucial feature in colorectal cancer (CRC), we primarily asked whether the expression of this protein may account for differences in clinicopathological features and survival rates of CRC patients. Protein expression was evaluated by immunohistochemistry in the institutional tissue microarray (TMA), and gene expression by the analysis of publicly available datasets. To place the prognostic relevance in a predicted biological context, gene co-expression set around SPDL1 identified by public data mining was annotated and assessed for enrichment in gene ontology (GO) categories, BRITE hierarchies, and Reactome pathways. The comparison with adjacent normal tissue revealed a high expression of SPDL1 protein in a subset of tumor cases (48.84%), and these had better prognosis than the SPDL1-low expression counterpart even after adjustment for multiple confounders. SPDL1-high expression within tumors was associated with a median 56-month survival advantage, but not with any clinicopathological characteristics of our cohort. In the TCGA cohort, SPDL1 was overexpressed in tumor tissue and positively associated with improved survival, chromosome instability phenotype, and various GIN markers. In addition to the genes critically involved in the cell cycle and mitosis, a gene set co-expressed with SPDL1 contained checkpoint members of both chromosome segregation and DNA replication, as well as those associated with defective DNA repair, and retrograde vesicle-mediated transport. In conclusion, SPDL1 is an independent predictor of CRC patient survival in a possible connection with chromosomal instability.

Abstract P3-01-06: Decorin-mediated suppression of tumorigenesis and skin invasion in inflammatory breast cancer via inhibition of the E-cadherin/EGFR axis

Background: Inflammatory breast cancer (IBC) is a clinically distinct and highly aggressive form of primary breast cancer. Although considered rare, IBC accounts for 10% of breast cancer-related deaths owing to its rapid proliferation and strong propensity to metastasize. The molecular mechanisms underlying the aggressiveness and metastatic propensity of IBC remain elusive. Through transcriptome profiling we identified Decorin (DCN) as being significantly altered in metastatic IBC cell sublines. DCN is a secreted, small leucine-rich proteoglycan known to function as a tumor/metastasis suppressor by inhibiting several signaling pathways including EGFR, TGFβ, and c-MET. However, whether or how DCN regulates IBC tumorigenesis or metastasis is unknown. The aim of this study was to investigate the function and mechanism of DCN in IBC tumorigenesis and metastasis.

Methods: Three IBC cell lines [ER-/HER2+ (MDA-IBC3, SUM190) and ER-/HER2- (SUM149)] were used. DCN gene expression in clinical samples was analyzed from publically available datasets and the IBC Consortium dataset. DCN was stably expressed in IBC cell lines by using lentiviral vectors. For in vivo studies, DCN-overexpressing stable cell lines were injected into cleared mammary fat pads of SCID/Beige mice and tumor growth was monitored via caliper measurements. Tumor-skin involvement was assessed visually during primary tumor growth and tumor excision. Reverse phase protein array analysis was used for proteomic profiling. Protein-protein interactions were analyzed by reciprocal immunoprecipitation of exogenous or endogenous proteins.

Results: DCN expression was significantly lower in breast cancer samples than in normal breast (p<0.0001), in more aggressive breast cancer subtypes (p<0.0001), and in metastatic tumors relative to primary tumors (p<0.0001). High DCN expression correlated with improved overall survival (p<0.0001) and relapse-free survival (p=0.0003). In vitro, DCN overexpression in IBC cell lines inhibited colony formation (MDA-IBC3, p=0.0115; SUM149, p=0.0068), migration (SUM149, p=0.0165), invasion (SUM149, p=0.0159), and primary and secondary mammosphere formation (primary: MDA-IBC3, p=0.0209; SUM149, p=0.0232; secondary: MDA-IBC3, p=0.01; SUM149, p=0.0031). In vivo, DCN overexpression in MDA-IBC3 cells inhibited primary tumor growth (p=0.0092) and reduced skin invasion (89.9% DCN control vs 33.3% DCN-overexpressed, p=0.017, Chi-square test). Our proteomics data in DCN-overexpressing SUM149 and MDA-IBC3 cells showed downregulated EGFR and E-cadherin protein levels. Mechanistically, DCN reduced expression of E-cadherin and EGFR and reduced phosphorylation of EGFR in IBC cells. Exogenous and endogenous co-immunoprecipitation experiments showed direct physical binding between DCN and E-cadherin proteins in all IBC cell lines. Moreover, overexpression of DCN downregulated E-cadherin via protein instability rather than decreased E-cadherin mRNA expression. E-cadherin knockdown in IBC cells decreased, whereas its overexpression increased, activation of EGFR signaling without affecting DCN expression. Finally, restoring E-cadherin in DCN-overexpressing IBC cell lines rescued the inhibitory effect of DCN on EGFR signaling.

Conclusions: We found that DCN inhibited tumorigenesis and skin invasion in IBC via its direct interaction with and stabilization of E-cadherin and its suppression of EGFR signaling. Our findings provide new insights and a novel mechanism for IBC pathobiology that may be therapeutically targetable. Future studies will determine the role of DCN in IBC metastasis and the detailed mechanism of DCN-mediated suppression of tumorigenesis and metastasis in IBC.

Citation Format: Xiaoding Hu, Emilly Schlee Villodre, Richard Larson, Omar M. Rahal, Xiaoping Wang, Savitri Krishnamurthy, Debu Tripathy, Naoto T Ueno, Wendy A Woodward, Bisrat Godefay Debeb. Decorin-mediated suppression of tumorigenesis and skin invasion in inflammatory breast cancer via inhibition of the E-cadherin/EGFR axis [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-01-06.

Abstract P3-01-10: Ndrg1-egfr axis in inflammatory breast cancer tumorigenesis and brain metastasis

Background: Inflammatory breast cancer (IBC) is a rare (1-2%) but lethal form of primary breast cancer responsible for 10% of breast cancer-related deaths in the United States. IBC tumors grow aggressively and have a high risk of metastasis, particularly to the brain. Unraveling the pathways involved in IBC aggressiveness and metastasis could reveal new therapeutic targets. We recently identified NDRG1 (N-Myc downstream regulated gene1) in a newly isolated subline of MDA-IBC3 cells as a top candidate protein associated with enhanced propensity for brain metastasis. Although the metastasis suppressor properties of NDRG1 are widely described, its function in the pathobiology of IBC is unknown. Here we investigated the function of NDRG1 in tumorigenesis and metastatic progression to brain in IBC.

Methods: NDRG1 gene expression was analyzed in large publically available breast cancer clinical datasets and the IBC Consortium dataset, and median expression level was used to stratify patients into NDRG1-high and NDRG1-low groups. Tissue microarrays of IBC patient samples were immunostained with anti-NDRG1 antibody. Stable knockdown (KD) of NDRG1 in IBC cell lines (HER2+: MDA-IBC3; TNBC: SUM149, BCX010) was obtained by lentiviral gene transfer. For in vivo studies, control and NDRG1 KD IBC cell lines were transplanted into cleared mammary fat pads of SCID/Beige mice and tumor growth monitored via caliper measurements. Reverse phase protein array analysis was used for proteomic profiling.

Results: In several independent cohorts of patients with breast cancer (including The Cancer Genome Atlas), NDRG1 mRNA expression was significantly higher in ER-negative and high-grade breast tumors (p<0.0001) and was associated with poor overall survival (p=0.0003), relapse-free survival (p<0.0001), and metastasis-free survival (p=0.0012). NDRG1 expression was higher in more aggressive, basal-like and HER2+ subtypes than in hormone receptor-positive subtypes (p<0.0001), and was also higher in IBC vs. non-IBC tumors (p=0.007, IBC consortium dataset). Immunostaining showed NDRG1 was frequently expressed in IBC patient tumors (83%) and was associated with worse overall survival (OS, p=0.0129) and disease-specific survival (DSS, p=0.013). On multivariate analysis, NDRG1 was an independent prognostic factor for poor OS [HR 2.5 (95%CI, 1.3-4.7), p=0.0047] and DSS [HR 2.6 (95%CI 1.3-5.1), p=0.006]. Notably, NDRG1 expression was higher in patients with brain metastasis vs. primary tumors (GSE43837, p=0.018) and correlated with shorter time to development of brain metastasis (GSE2034, p=0.026). NDRG1-high sublines had enhanced propensity for brain metastasis as shown by higher incidence (100% vs. 44% for NDRG1-low sublines, p=0.01) and increased brain metastasis burden (p=0.0008). Invitro, silencing NDRG1 in IBC cell lines significantly reduced colony formation, migration, invasion, and cancer stem-like properties. In vivo, silencing of NDRG1 inhibited primary tumor growth of SUM149 (p<0.0001) and MDA-IBC3 (p=0.0426) xenografts. Proteomics analysis showed that NDRG1 correlated positively with activation of the EGFR/STAT3 signaling pathway. Mechanistically, NDRG1 knockdown in IBC cell lines reduced EGFR expression and suppressed phosphorylation of EGFR and STAT3, whereas NDRG1 overexpression increased EGFR expression and enhanced EGFR-STAT3 activation.

Conclusions: We showed that high NDRG1 was associated with worse clinical outcomes in patients with IBC and that NDRG1 drives tumor progression in IBC potentially via activation of the EGFR-STAT3 signaling pathway. Targeting the NDRG1-EGFR axis may be a novel therapeutic approach in IBC and other aggressive breast cancers. Additional investigations are underway to determine the detailed mechanisms of NDRG1-mediated IBC tumorigenesis and brain metastasis

Citation Format: Emilly Schlee Villodre, Xiaoding Hu, Richard Larson, Bedrich L Eckhardt, Yun Gong, Lei Huo, Juhee Song, Savitri Krishnamurthy, Nuhad Ibrahim, Naoto T Ueno, Debu Tripathy, Wendy A Woodward, Bisrat G Debeb. Ndrg1-egfr axis in inflammatory breast cancer tumorigenesis and brain metastasis [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-01-10.

Abstract P2-01-03: Lipocalin 2 promotes inflammatory breast cancer tumorigenesis and skin invasion

Background: Inflammatory breast cancer (IBC) is the most lethal form of primary breast cancer and accounts for a significant 10 % of breast cancer deaths in the USA owing to its aggressive proliferation and metastasis, and a lack of effective therapeutic options. Unraveling the underlying mechanisms of growth and metastasis of this aggressive disease could lead to effective therapeutic strategies for an improved outcome in IBC patients. We recently generated in vitro and in vivo IBC models for brain metastasis studies [Debeb et al. JNCI, 2016] and observed an upregulation of Lipocalin 2 (LCN2), a small, secreted iron-trafficking protein which plays a significant role in immune and inflammatory responses and the promotion of malignant progression. The purpose of this study was to investigate the function of LCN2 in IBC tumorigenesis and metastasis.

Methods: Stable knockdown (KD) of LCN2 in IBC cell lines was achieved with lentiviral vectors. Proteomic and gene expression profiling were performed using RPPA and Affymetrix Clariom D microarray. For in vivo studies, control and LCN2 KD IBC cells were transplanted into the cleared mammary fat pad of SCID/Beige mice. Tumor-skin involvement was assessed visually during primary tumor growth and tumor excision. LCN2 gene expression levels in clinical samples were analyzed from the IBC Consortium as well as public data sets. LCN2 serum levels in IBC patients were measured using ELISA and were correlated with clinicopathological variables and outcome data.

Results: LCN2 gene expression is higher in IBC versus non-IBC patients (p=0.00036), independently of the molecular subtypes, and higher in more aggressive (TNBC and HER2+) than hormone receptor-positive subtypes (p<0.00001). LCN2 expression in patient tissues is correlated with reduced overall survival (p<0.00001) and metastasis-free survival (p=0.04) in non-IBC; however, LCN2 was not associated with overall survival in IBC patient serum samples. LCN2 expression was also significantly higher in IBC cell lines, in their culture media, and in brain metastasis sublines compared to non-IBC cell lines (p=0.004). In IBC cell lines, LCN2 KD reduced proliferation, colony formation, migration, and cancer stem cell properties. In vivo silencing of LCN2 in SUM149 cells inhibited primary tumor growth (p=0.001)and resulted in a well-differentiated tumor histology. Additionally, SUM149 LCN2 KD significantly reduced skin invasion/recurrence (LCN2 control vs LCN2 KD: 88 % vs 25 %, p=0.01) suggesting LCN2 is a mediator of tumorigenesis. Analysis of proteomics data showed changes in major signaling pathways including PI3K-Akt signaling and EGF/EGFR signaling pathways. Mechanistically, LCN2 depletion in SUM149 abrogated EGF-induced EGFR phosphorylation and ERK activation.

Conclusions: Our findings suggest that LCN2 may drive IBC tumor progression and skin invasion/recurrence potentially via the EGFR signaling pathway.Future studies will determine the role of LCN2 in metastasis and pinpoint the detailed mechanisms of LCN2-mediated IBC tumorigenesis and recurrence.

Citation Format: Villodre ES, Larson R, Hu X, Stecklein SR, Gomez K, Finetti P, Krishnamurthy S, Ivan C, Su X, Ueno NT, Van Laere S, Bertucci F, Tripathy D, Vivas-Mejía P, A Woodward W, Debeb BG. Lipocalin 2 promotes inflammatory breast cancer tumorigenesis and skin invasion [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 P2-01-03.

Autophagy interplay with apoptosis and cell cycle regulation in the growth inhibiting effect of resveratrol in glioma cells

Prognosis of patients with glioblastoma (GBM) remains very poor, thus making the development of new drugs urgent. Resveratrol (Rsv) is a natural compound that has several beneficial effects such as neuroprotection and cytotoxicity for several GBM cell lines. Here we evaluated the mechanism of action of Rsv on human GBM cell lines, focusing on the role of autophagy and its crosstalk with apoptosis and cell cycle control. We further evaluated the role of autophagy and the effect of Rsv on GBM Cancer Stem Cells (gCSCs), involved in GBM resistance and recurrence. Glioma cells treated with Rsv was tested for autophagy, apoptosis, necrosis, cell cycle and phosphorylation or expression levels of key players of these processes. Rsv induced the formation of autophagosomes in three human GBM cell lines, accompanied by an upregulation of autophagy proteins Atg5, beclin-1 and LC3-II. Inhibition of Rsv-induced autophagy triggered apoptosis, with an increase in Bax and cleavage of caspase-3. While inhibition of apoptosis or autophagy alone did not revert Rsv-induced toxicity, inhibition of both processes blocked this toxicity. Rsv also induced a S-G2/M phase arrest, accompanied by an increase on levels of pCdc2(Y15), cyclin A, E and B, and pRb (S807/811) and a decrease of cyclin D1. Interestingly, this arrest was dependent on the induction of autophagy, since inhibition of Rsv-induced autophagy abolishes cell cycle arrest and returns the phosphorylation of Cdc2(Y15) and Rb(S807/811), and levels of cyclin A, and B to control levels. Finally, inhibition of autophagy or treatment with Rsv decreased the sphere formation and the percentage of CD133 and OCT4-positive cells, markers of gCSCs. In conclusion, the crosstalk among autophagy, cell cycle and apoptosis, together with the biology of gCSCs, has to be considered in tailoring pharmacological interventions aimed to reduce glioma growth using compounds with multiple targets such as Rsv.