Novel Therapeutic Target In Triple-negative Breast Cancer Research Articles

Spindle apparatus coiled-coil protein 1 (SPDL1) serves as a novel prognostic biomarker in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) has a poor prognosis, an ineffective diagnosis, and a high degree of aggressiveness. Therefore, novel therapeutic targets for TNBC urgently need to be identified. Through a series of bioinformatics analyses, including analysis of differential gene expression, protein-protein interaction (PPI) network, univariate cox regression, immune infiltration, pathway enrichment, etc, as well as auxiliary immunohistochemistry (IHC) and protein quantitativae analysis, to explore prognostic marker for TNBC. In TNBC tissues, we found that SPDL1 (CCDC99) was considerably overexpressed at both the mRNA and protein levels compared to that in normal and non-TNBC tissues. Additionally, we found that SPDL1-high expression was strongly linked to poor prognosis in TNBC patients. Excessive SPDL1 expression was positively correlated with tumor growth and strongly linked to the cell cycle, DNA replication, and the p53 signaling pathway. In addition, CIBERSORT analysis revealed that SPDL1 can affect the tumor immune microenvironment (TME) in TNBC, encourage the development of TNBC and act as a potential prognostic biomarker for TNBC. Patients with SPDL1-high expression were more sensitive to AZD8055. Notably, we discovered that SPDL1 is highly expressed in the majority of malignancies and may have an impact on the pancancer prognosis. SPDL1 can serve as a novel prognostic marker for TNBC and pancancer patients.

Resveratrol-derived inhibitors of the E3 ubiquitin ligase PELI1 inhibit the metastasis of triple-negative breast cancer

Triple-negative breast cancer (TNBC), as the most challenging subtype of breast cancer, exerts highly invasive ability and metastatic nature to the lymph nodes, which is correlated with poor survival rates among patients. Pellino-1 (PELI1) is an E3 ubiquitin ligase involved in tumor invasion and metastasis, and has the potential to be developed as a novel therapeutic target for TNBC. In this study, we identified a potent inhibitor of PELI1, namely compound 3d, on the basis of natural stilbene framework through medicinal chemistry approaches. This novel PELI1 inhibitor 3d showed potent binding affinity to PELI1 (Kd 8.2 μM) in fluorescence quenching assay, and markedly interrupted the interaction of PELI1 and SNAIL/SLUG confirmed by co-immunoprecipitation. Moreover, 3d exhibited potent antitumor activity in inhibiting tumor cell migration in scratch wound healing assay without affecting cell proliferation in vitro, and down-regulated the downstream EMT-effectors of PELI1 as assessed by western blotting. In the experimental lung metastasis model, 3d showed anti-TNBC metastasis efficacy without observable toxicity in vivo.

Nrf3 promotes the proliferation and migration of triple‑negative breast cancer by activating PI3K/AKT/mTOR and epithelial‑mesenchymal transition.

Nuclear factor erythroid 2-related factor 3 (Nrf3) is increasingly implicated in multiple types of cancer; however, its function in triple-negative breast cancer (TNBC) remains unclear. This study aimed to examine the role of Nrf3 in TNBC. Compared with adjacent normal tissues, TNBC tissues expressed higher levels of Nrf3, and its expression was negatively correlated with survival time. Additionally, Nrf3 knockdown reduced the proliferation and migration of TNBC cells, whereas overexpression of Nrf3 had the opposite effects in vitro and in vivo. Moreover, functional enrichment of TNBC cells overexpressing Nrf3 allowed for the identification of numerous genes and pathways that were altered following Nrf3 overexpression. Further study showed that overexpression of Nrf3 activated the PI3K/AKT/mTOR signaling pathway and regulated the expression of proteins associated with epithelial-mesenchymal transition. Nrf3 was found to directly bind to p110α promoter regions, as evidenced by luciferase reporter and chromatin immunoprecipitation assays. Furthermore, PI3K inhibitors partially decreased the proliferation and migration of the Nrf3 overexpressing TNBC cells. In conclusion, Nrf3 enhances cellular proliferation and migration by activating PI3K/AKT/mTOR signaling pathways, highlighting a novel therapeutic target for TNBC.

Single-Cell Transcriptome Analysis Revealed Heterogeneity and Identified Novel Therapeutic Targets for Breast Cancer Subtypes.

Breast cancer (BC) is a heterogeneous disease, which is primarily classified according to hormone receptors and HER2 expression. Despite the many advances in BC diagnosis and management, the identification of novel actionable therapeutic targets expressed by cancerous cells has always been a daunting task due to the large heterogeneity of the disease and the presence of non-cancerous cells (i.e., immune cells and stromal cells) within the tumor microenvironment. In the current study, we employed computational algorithms to decipher the cellular composition of estrogen receptor-positive (ER+), HER2+, ER+HER2+, and triple-negative BC (TNBC) subtypes from a total of 49,899 single cells' publicly available transcriptomic data derived from 26 BC patients. Restricting the analysis to EPCAM+Lin- tumor epithelial cells, we identified the enriched gene sets in each BC molecular subtype. Integration of single-cell transcriptomic with CRISPR-Cas9 functional screen data identified 13 potential therapeutic targets for ER+, 44 potential therapeutic targets for HER2+, and 29 potential therapeutic targets for TNBC. Interestingly, several of the identified therapeutic targets outperformed the current standard of care for each BC subtype. Given the aggressive nature and lack of targeted therapies for TNBC, elevated expression of ENO1, FDPS, CCT6A, TUBB2A, and PGK1 predicted worse relapse-free survival (RFS) in basal BC (n = 442), while elevated expression of ENO1, FDPS, CCT6A, and PGK1 was observed in the most aggressive BLIS TNBC subtype. Mechanistically, targeted depletion of ENO1 and FDPS halted TNBC cell proliferation, colony formation, and organoid tumor growth under 3-dimensional conditions and increased cell death, suggesting their potential use as novel therapeutic targets for TNBC. Differential expression and gene set enrichment analysis in TNBC revealed enrichment in the cycle and mitosis functional categories in FDPShigh, while ENO1high was associated with numerous functional categories, including cell cycle, glycolysis, and ATP metabolic processes. Taken together, our data are the first to unravel the unique gene signatures and to identify novel dependencies and therapeutic vulnerabilities for each BC molecular subtype, thus setting the foundation for the future development of more effective targeted therapies for BC.

Identification of ubiquitination-related gene classification and a novel ubiquitination-related gene signature for patients with triple-negative breast cancer.

Background: Ubiquitination-related genes (URGs) are important biomarkers and therapeutic targets in cancer. However, URG prognostic prediction models have not been established in triple-negative breast cancer (TNBC) before. Our study aimed to explore the roles of URGs in TNBC. Methods: The Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) and the Gene Expression Omnibus (GEO) databases were used to identify URG expression patterns in TNBC. Non-negative matrix factorization (NMF) analysis was used to cluster TNBC patients. The least absolute shrinkage and selection operator (LASSO) analysis was used to construct the multi-URG signature in the training set (METABRIC). Next, we evaluated and validated the signature in the test set (GSE58812). Finally, we evaluated the immune-related characteristics to explore the mechanism. Results: We identified four clusters with significantly different immune signatures in TNBC based on URGs. Then, we developed an 11-URG signature with good performance for patients with TNBC. According to the 11-URG signature, TNBC patients can be classified into a high-risk group and a low-risk group with significantly different overall survival. The predictive ability of this 11-URG signature was favorable in the test set. Moreover, we constructed a nomogram comprising the risk score and clinicopathological characteristics with favorable predictive ability. All of the immune cells and immune-related pathways were higher in the low-risk group than in the high-risk group. Conclusion: Our study indicated URGs might interact with the immune phenotype to influence the development of TNBC, which contributes to a further understanding of molecular mechanisms and the development of novel therapeutic targets for TNBC.

Abstract 1873: SpliceCore® a novel ML tool for identifying disease-specific alternative splicing uncovered a promising therapeutic target for triple negative breast cancer

Abstract Accumulating evidence highlights aberrant splicing as a disease-driving event in cancer, affecting tumor progression, metastasis, and therapy resistance. Multiple studies have described the tumor-promoting activity of specific aberrant cis-splicing variants and misregulation of trans-acting splicing factors in patients. Hence, the identification of aberrant splicing patterns has the potential to translate into actionable biomarkers and novel therapeutic targets, particularly for treatment insensitive cancers such as Triple Negative Breast Cancer (TNBC). Envisagenics’ SpliceCore is an innovative cloud-based platform that integrates machine learning (ML) algorithms with high performance computing to analyze large RNA-seq datasets to predict biologically relevant, novel, and highly prevalent tumor-specific alternative splicing (AS) changes. Using SpliceCore, we have analyzed >2500 RNA-seq samples from different breast cancer subtypes as well as normal breast tissue and identified several AS derived therapeutic targets with the potential to translate into therapeutic candidates for TNBC. Here, we report a novel, alternatively spliced isoform that is present in 60.5% of TNBC patients and correlates with poor overall survival. This cytoplasmic protein was previously described as a regulator of the TGFβ pathway; therefore, we have validated the isoform switching action in a TGFβ dependent tumor progression model and demonstrated the activity of Splice Switching Oligos (SSO) to modulate its effect. We observed that this AS was correlated to a differential response on subcellular localization for phSmad2/3, Smad2/3 and TGFβRI. Pretreatment of the TNBC cells with SSO before TGFβ pathway activation modulates its proliferation response by affecting gene expression of p21, c-Myc and Smad7, leading to a decrease of cells in the G2 mitotic phase of the cell cycle and a loss of cell viability after the SSO treatment. More importantly, migratory response induced by TGFβ in TNBC cells was significantly inhibited by SSOs. Pre-treatment with SSO-0205 before TGFβ activation downregulated gene expression of Angiopoietin-like 4, Integrins α5 and β3, TGFβ associated migration markers, which was followed by a 55% decrease in cell migration. Our state-of-the-art ML technology, SpliceCore, has proven its ability to uncover novel disease-specific AS targets and to design splice correcting oligonucleotides for subsequent therapeutic development. Our data provides experimental proof of concept that has uncovered a novel therapeutic target for TNBC, whose aberrant splicing contributes to TNBC pathogenesis by misregulation of the TGFβ pathway. Moreover, SSOs predicted by SpliceCore were able to correct the aberrant splicing downstream effect, thereby uncovering a novel alternative splicing targeted approach for treating TNBC patients. Citation Format: Miguel A. Manzanares, Alyssa Casill, Kendall Anderson, Priyanka Dhingra, Vanessa Frederick, Adam Geier, Martin Akerman, Gayatri Arun. SpliceCore® a novel ML tool for identifying disease-specific alternative splicing uncovered a promising therapeutic target for triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1873.

Abstract 3022: Tryptophan metabolism is associated with obesity and triple negative breast cancer risk in black and white women

Abstract Non-Hispanic black (NHB) women are more likely to be diagnosed and die from triple negative breast cancer (TNBC) than non-Hispanic white (NHW) women. We previously showed that TNBC tissues display a distinct microbial signature. Obesity which contributes to chronic low-grade inflammation and gut microbial dysbiosis further exacerbates TNBC outcomes for NHB women. However, it is unclear the extent to which microbial differences in breast tumor tissues may be driven by alterations in microbial metabolites as a result of obesity status. Therefore, the aim of this global metabolomic profiling study was to investigate alterations in microbial metabolism pathways in breast tissues of NHB and NHW obese women (avg. BMI = 35.7) relative to non-obese women (avg. BMI = 23.4) with and without TNBC. In this study, we analyzed 984 metabolites derived from a total of 51 NHB and NHW women, including 15 patients with TNBC, 12 patients with less aggressive Luminal A-type breast cancer, and 24 healthy controls for comparison using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to identify microbial metabolites and metabolomic signatures that differ by breast tumor subtype and obesity status. We detected 501 significantly increased metabolites and 33 significantly decreased metabolites in TNBC patients compared to controls. Principal component analysis and hierarchical clustering of the global metabolite profiling data revealed separation between the metabolic signatures of normal and breast tumor tissue. Random forest analysis revealed a unique biochemical signature associated with elevated L-Tryptophan (Trp) and Kynurenine (Kyn) metabolites and lower levels of microbial-derived metabolites critical for controlling inflammation and immune response in obese individuals and those with TNBC. TCGA analysis further revealed that expression of key Trp enzymes was significantly associated with worse survival outcomes in TNBC patients compared to other breast tumor subtypes. Our findings highlight a potential role for Trp metabolism through the Kyn pathway in obesity and TNBC risk. Further investigations into the Kyn metabolomic pathway may prove to be a novel therapeutic target for TNBC. Citation Format: Alana Smith, Qingqing Gu, Ernestine Kubi Amos-Abanyie, Elizabeth Tolley, Lu Lu, Beverly Lyn-Cook, Athena Starlard-Davenport. Tryptophan metabolism is associated with obesity and triple negative breast cancer risk in black and white women [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3022.

Abstract 5813: Glycogen synthesis as potential novel target in triple negative breast cancer: Glycogen synthase 1 expression in human breast cancers and the impact of downregulation on proliferation of preclinical models

Abstract Background: Triple-negative breast cancer (TNBC) has a poor clinical prognosis and is characterized by a lack of druggable targets and a hypoxic tumor microenvironment. Hypoxia-induced glycogen accumulation and utilization are involved in cancer proliferation and therapy resistance, making modulation of glycogen metabolism of therapeutic interest. Therefore, we studied expression of glycogen synthase 1 (GYS1, the key regulator of glycogen synthesis) and glycogen stores in publicly available expression data and human breast tumors including TNBC. Also, we studied downregulation of GYS1 in preclinical breast cancer models, focusing on TNBC. Methods: GYS1 mRNA expression and correlations with survival per clinical subtype were assessed in the METABRIC dataset. A tissue micro-array was constructed from primary tumors of 396 breast cancer patients with long-term follow-up, including normal breast control tissue. Triplicate tissue cores were stained immunohistochemically for GYS1, glycogen and the hypoxic marker carbonic anhydrase 9, and with periodic acid-Schiff staining for glycogen. In four TNBC cell lines and an MDA-MB-231 xenograft model, GYS1 protein expression, glycogen content and cell proliferation in normoxia and hypoxia were evaluated +/- GYS1 knockdown by siRNA or shRNA. Sensitivity of shGYS1 cell lines to drugs targeting mitochondria was tested. Results: In the METABRIC dataset (n = 1904), overexpression of GYS1 mRNA was associated with poor overall survival (HR 1.20 [95% CI 1.05 - 1.38]), which was mainly driven by the TNBC patients (n = 299, HR 1.52 [95% CI 1.09 - 2.14]). Immunohistochemically, most primary breast tumors had elevated GYS1 levels and glycogen content compared to normal breast tissue, with subtype specific analyses ongoing. In all breast cancer cell lines, hypoxia induced GYS1 protein expression and increased glycogen content. Acute siRNA-mediated GYS1 knockdown decreased proliferation of (TN)BC cell lines and MDA-MB-231 spheroids in both hypoxia and normoxia. shGYS1 MDA-MB-231 cells had decreased glycogen levels and shGYS1 MDA-MB-231 xenograft growth was impaired, especially in the first six weeks after inoculation. In control xenografts, immunohistochemical GYS1 expression was most pronounced adjacent to the necrotic tumor core, whereas shGYS1 xenografts lacked GYS1 expression. Finally, shGYS1 MDA-MB-231 cells were more sensitive to inhibitors of mitochondrial protein homeostasis, suggesting a potential synergistic approach to overcome eventual metabolic adaptation. Conclusions: GYS1 is overexpressed in primary breast tumors and high mRNA levels correlate with poor survival in TNBC. GYS1 downregulation impairs TNBC proliferation in vitro and in vivo, highlighting glycogen synthesis as potential novel therapeutic target in TNBC. Citation Format: Ellen C. De Heer, Christos E. Zois, Esther Bridges, Mieke C. Zwager, Tineke van der Sluis, Bert van der Vegt, Carolien P. Schröder, Steven de Jong, Adrian L. Harris, Mathilde Jalving. Glycogen synthesis as potential novel target in triple negative breast cancer: Glycogen synthase 1 expression in human breast cancers and the impact of downregulation on proliferation of preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5813.

Comparative analysis of transient receptor potential channel 5 opposite strand-induced gene expression patterns and protein-protein interactions in triple-negative breast cancer.

In patients with triple-negative breast cancer (TNBC), high tumour mutation burden and aberrant oncogene expression profiles are some of the causes of poor prognosis. Therefore, it is necessary to identify aberrantly expressed oncogenes, since they have the potential to serve as therapeutic targets. Transient receptor potential channel 5 opposite strand (TRPC5OS) has been previously shown to function as a novel tumour inducer. However, the underlying mechanism of TRPC5OS function in TNBC remain to be elucidated. Therefore, in the present study TRPC5OS expression was first measured in tissue samples of patients with TNBC and a panel of breast cancer cell lines (ZR-75-1, MDA-MB-453, SK-BR-3, JIMT-1, BT474 and HCC1937) by using qRT-PCR and Western blotting. Subsequently, the possible effects of TRPC5OS on MDA-MB-231 cells proliferation were determined using Cell Counting Kit-8 and 5-Ethynyl-2′-deoxyuridine assays after Lentiviral transfection of MDA-MB-231. In addition, potential interaction partners of TRPC5OS were explored using liquid chromatography-mass spectrometry (LC-MS)/MS. Gene expression patterns following TRPC5OS overexpression were also detected in MDA-MB-231 cells by using High-throughput sequencing. Gene Ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) analysis were then used to systematically verify the potential interactions among the TRPC5OS-regulated genes. The potential relationship between TRPC5OS-interacting proteins and gene expression patterns were studied using Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) analysis. TRPC5OS expression was found to be significantly higher in TNBC tumour tissues and breast cancer cell lines compared with luminal tumour tissues and ZR-75-1. In addition, the overexpression of TRPC5OS significantly increased cell proliferation. High-throughput sequencing results revealed that 5,256 genes exhibited differential expression following TRPC5OS overexpression, including 3,269 upregulated genes and 1,987 downregulated genes. GO analysis results indicated that the functions of these differentially expressed genes were enriched in the categories of ‘cell division’ and ‘cell proliferation’ regulation. KEGG analysis showed that the TRPC5OS-regulated genes were associated with processes of ‘homologous recombination’ and ‘TNF signalling pathways’. Subsequently, 17 TRPC5OS-interacting proteins were found using LC-MS/MS and STRING analysis. The most important protein among interacting proteins was ENO1 which was associated with glycolysis and regulated proliferation of cancer. In summary, data from the present study suggest that TRPC5OS overexpression can increase TNBC cell proliferation and ENO1 may be a potential target protein mediated by TRPC5OS. Therefore, TRPC5OS may serve as a novel therapeutic target for TNBC.

Abstract P5-17-11: Novel therapeutic target for triple negative breast cancer uncovered by SpliceCore® an innovative platform that identifies disease-specific alternative splicing

Abstract Aberrant splicing is a major hallmark of cancer, affecting tumor progression, metastasis, and therapy resistance. The oncogenic activity of specific cis splicing errors and trans-acting splicing factor misregulation in patient tumors have been demonstrated in multiple studies. As such, cancer-associated splicing dysregulation is a novel source of clinically actionable biomarkers and therapeutic targets, particularly for the treatment of insensitive cancers such as Triple Negative Breast Cancer (TNBC). Envisagenics’ SpliceCore technology is an innovative cloud-based software platform that integrates machine learning (ML) algorithms with high performance computing to analyze large RNA-seq datasets to predict biologically relevant, novel, and highly prevalent tumor specific alternative splicing (AS) changes. Using SpliceCore, we have analyzed >2500 RNAseq samples from different breast cancer subtypes as well as normal breast tissue and identified several AS targets with the potential to translate into therapeutic candidates for TNBC. Interestingly, one of our leading AS targets is an exon skipping isoform that is present in 60.5% of TNBC patients and correlates with poor overall survival, without showing differences in gene expression between all the breast cancer subtypes and healthy patients studied. In addition, SpliceCore was used to predict and design a set of splice switching oligos (SSO) that can efficiently switch the skipping isoform to an inclusion isoform in TNBC cells. The skipping isoform plays a critical role in tumor progression via a TGFβ-dependent mechanism as demonstrated by detailed isoform switching studies using SSO-0205. Pretreatment of the TNBC cells with SSO-0205 24 hours before TGFβ pathway activation modulated TGFβ pathway related protein levels and cellular localization and reversed the cell proliferative response associated with it. This resulted in a strong inhibition of p21 gene expression, accompanied by a 50% decrease on the number of cells in G2, the mitotic phase of the cell cycle, and 40% decrease on cell viability. Additionally, migratory response induced by TGFβ in TNBC cells was also significantly inhibited by SSO-0205 pretreatment, which downregulated ANGPTL4 gene expression followed by a 55% decrease in cell migration. In summary, we were able to uncover a novel therapeutic target for TNBC, whose aberrant splicing contributes to TNBC pathogenesis by promoting an overactivation of the TGFβ pathway. Our results provide experimental proof of concept that demonstrate SpliceCore’s ability to discover novel disease specific AS targets and design splice correcting oligonucleotides for subsequent therapeutic development. Reversal of this aberrant TNBC specific splicing using SSOs represent a new and promising therapeutic approach that will have a significant impact on TNBC treatment and clinical care. Moreover, SpliceCore can be applied to multiple other indications opening a new avenue for therapeutic development in cancer. Citation Format: Miguel A Manzanares, Priyanka Dhingra, Kendall Anderson, Vanessa Frederick, Adam Geier, Alyssa Casill, Martin Akerman, Gayatri Arun. Novel therapeutic target for triple negative breast cancer uncovered by SpliceCore® an innovative platform that identifies disease-specific alternative splicing [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 P5-17-11.

MiR-181c suppresses triple-negative breast cancer tumorigenesis by targeting MAP4K4

Breast cancer (BC) ranks as the highest incidence among cancer types in women all over the world. Triple-negative breast cancer (TNBC) is known as a highly aggressive subtype of BC due to high rate of recurrence and metastasis, poor prognosis and lacking of effective targeted therapies. MicroRNAs (miRNAs) are a class of short endogenous non-coding RNA that mostly functioning to silence the target mRNAs. In this study, we found miR-181c-5p (miR-181c) was down-expressed in TNBC tissues and cell lines, whereas MAP4K4 was highly-expressed. Up-regulation of miR-181c inhibited TNBC cells proliferation and migration, promoted TNBC cells apoptosis and regulated the cell cycle by arresting cells in the G0/G1 cell phase, while depletion of miR-181c showed opposite effect. Importantly, miR-181c suppressed MAP4K4 expression at both mRNA and protein levels by directly targeting MAP4K4, thereby inhibiting the tumor-promoting effect of MAP4K4. This study is the first to demonstrate the miR-181c/MAP4K4 signaling in suppressing TNBC, providing a novel therapeutic target for TNBC.

Dezocine, An Opioid Analgesic, Exerts Antitumor Effects in Triple-Negative Breast Cancer by Targeting Nicotinamide Phosphoribosyltransferase

Opioids are a potential adjuvant treatment for certain cancers; while they are primarily used to relieve chronic pain, these drugs may also affect cancer progression and recurrence. Dezocine is one opioid commonly used in China, but its effects on cancer cells are unknown. Here, we demonstrated the inhibitory effect of dezocine on triple-negative breast cancer (TNBC) cells, and determined the underlying molecular mechanism. We found that dezocine suppressed cell proliferation, migration and invasion, and induced apoptosis in TNBC cells. Xenograft models demonstrated the inhibitory effects of dezocine treatment on TNBC tumor growth in vivo. The anticancer effects of dezocine were independent of opioid receptors, which are not highly expressed by normal breast or breast cancer tissues. A pull-down assay and LC-MS/MS analysis indicated that dezocine directly targets NAMPT: computer modeling verified that the free energy of dezocine kinetically bound into the pocket of NAMPT was −17.4 kcal/mol. Consequently, dezocine treatment inhibited NAMPT enzyme activity, resulting in cellular NAD abolishment. We confirmed the dezocine-induced inhibition of cell proliferation by both NAMPT knockdown and upon treatment with the inhibitor FK866. Our results suggest that both dezocine and NAMPT might represent novel therapeutic targets for TNBC.

Abstract 6378: CDC20 is a novel therapeutic target in triple-negative breast cancer

Abstract Background: Approximately 15% of breast cancers lack expression of Estrogen Receptor (ER), Progesterone Receptor (PR) and Human Epidermal Growth Factor Receptor 2 (HER-2), and are referred to as Triple-Negative Breast Cancer (TNBC). Due to a lack of targeted therapies, clinical outcomes in patients with TNBC continue to be poor. Likewise, due to the inherently aggressive biology of the disease, patients are forced to deal with the toughest breast cancer while having the least treatment options. In this study, we identified Cell Division Cycle protein 20 (CDC20), a key regulatory protein that mediates sister chromatid separation in mitosis, as a novel therapeutic target in TNBC. Methods: To uncover new drivers of TNBC, we nominated genes that are significantly overexpressed in patients with TNBC, compared to non-TNBCs. After identifying CDC20 as a top hit in this analysis, we used RNAseq analyses, expression microarrays, and Western blotting to assess CDC20 expression levels in breast cancer patients and cell lines. Kaplan-Meier analyses were formed to study the correlation between clinical outcomes and CDC20 expression levels, including recurrence-free survival, metastasis-free survival and overall survival. shRNA and siRNA-mediated knockdown of CDC20 in TNBC cell lines were employed to study the role of CDC20 in TNBC proliferation, invasion, and migration. Results: CDC20 was significantly overexpressed in TNBCs (compared to non-TNBCs) patients and is a predictor of poor clinical outcomes and radiation resistance. CDC20 expression was also significantly higher in TNBC cell lines compared to non-TNBC cell lines, reflecting what is seen in clinical data sets, such as in The Cancer Genome Atlas. Sh and siRNA-mediated knockdown of CDC20 expression resulted in decreased proliferation, invasion and migration in TNBC cell lines. Conclusions and future directions: Our findings support the development of pharmacologic strategies to inhibit CDC20 function as a potential targeted therapy against TNBC. Efforts are underway to validate our findings in vivo in xenograft models of TNBC in mice. Citation Format: Jayesh K. Sharma, Prasanna Alluri, Nashir Udden. CDC20 is a novel therapeutic target in triple-negative breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6378.

Construction and Comprehensive Analysis of a ceRNA Network to Reveal Potential Novel Biomarkers for Triple-Negative Breast Cancer.

BackgroundTriple-negative breast cancer (TNBC) is the most common and aggressive type of breast cancer with an unfavourable outcome worldwide. Novel therapeutic targets are urgently required to explore this malignancy. This study explored the ceRNA network and the important genes for predicting the therapeutic targets.MethodsIt identified the differentially expressed genes of mRNAs, lncRNAs and miRNAs between TNBC and non-TNBC samples in four cohorts (TCGA, GSE38959, GSE45827 and GSE65194) to explore the novel therapeutic targets for TNBC. Downstream analyses, including functional enrichment analysis, ceRNA network, protein–protein interaction and survival analysis, were then conducted by bioinformatics analysis. Finally, the potential core protein of the ceRNA network in TNBC was validated by immunohistochemistry.ResultsA total of 1,045 lncRNAs and 28 miRNAs were differentially expressed in the TCGA TNBC samples, and the intersections of 282 mRNAs (176 upregulations and 106 downregulations) between the GEO and TCGA databases were identified. A ceRNA network composed of 7 lncRNAs, 62 mRNAs, 12 miRNAs and 244 edges specific to TNBC was established. The functional assay showed dysregulated genes, and GO, DO and KEGG enrichment analysis were performed. Survival analysis showed that mRNA LIFR and lncRNA AC124312.3 were significantly correlated with the overall survival of patients with TNBC in the TCGA databases (P < 0.05). Finally, the LIFR protein was validated, and immunohistochemical results showed the upregulated expression of LIFR in TNBC tissues.ConclusionThus, our study presents an enhanced understanding of the ceRNA network in TNBC, where the key gene LIFR may be a new promising potential therapeutic target for patients with TNBC.

The clinical impact of the expression of the cancer stem cell marker CD44v9 in early triple negative breast cancer (TNBC).

e12566 Background: The adhesion molecule CD44 is expressed in cancer stem-like cells (CSCs). CD44 variant 9 (CD44v9), a splicing variant of CD44, has emerged as a novel marker of cancer stemness. CD44v9 was reported to be associated with the resistance to chemotherapy in several malignancies. We recently reported that the high expression of CD44v9 is associated with the poor prognosis of the patients with triple negative breast cancer (TNBC), who received neoadjuvant chemotherapy (NAC). In this study, we investigated the clinical impact of the expression of CD44v9 in early TNBC who underwent surgery without NAC. Methods: Among 2257 primary breast cancer patients at clinical stage I-III who underwent surgery without NAC form 2002 to 2015, 201 patients with TNBC were included in this study. The expression of CD44v9 was analyzed immunohistochemistry (IHC). The associations between the CD44v9 expression and the clinicopathological characteristics and the prognosis were investigated. The tumors with the positive staining in more than two third of the cancer cells were regarded to be high expression of CD44v9. Results: CD44v9 high expression was observed in 62 cases (30.8%) and the low expression was in 139 cases (69.2%). Many of the CD44v9 high tumors were low grade than the tumors with low CD44v9. There were no significant associations between the expression levels of CD44v9 and the tumor size, lymph node metastasis and the pathological stage (pStage). There were no differences in the prognosis between the high and low CD44v9 expression in pStage I. However, in the patients with the tumors with pT1c or more (pT2, pT3) and the patients with pStage 2 and more, the high CD44v9 expression was significantly associated with the poor prognosis in terms of distant recurrence-free survival (DRFS) and overall survival (OS). In addition, high CD44v9 was associated with significantly shorter survival after recurrence. Many of these patients received various chemotherapy in the adjuvant setting and after recurrence. Therefore, CD44v9 high expression is considered to be associated with the poor prognosis due to the resistance to various chemotherapeutic agents. Conclusions: The prognosis of the TNBC patients with the high expression of CD44v9 is poor, which might be induced by the resistance to various chemotherapeutic agents. These results suggest that CD44v9 might be a novel therapeutic target for TNBC.

LncRNA FAM83H-AS1 promotes triple-negative breast cancer progression by regulating the miR-136-5p/metadherin axis.

In this study, we evaluated the function and regulation of the long non-coding RNA (lncRNA) FAM83H-AS1 in triple-negative breast cancer (TNBC). Our data show that the FAM83H-AS1 levels are increased in human TNBC cells and tissues. Proliferation, migration, and invasion of TNBC cells are decreased by FAM83H-AS1 suppression, but increased by FAM83H-AS1 overexpression. Bioinformatics analysis revealed that miR-136-5p is a potential target of FAM83H-AS1. MiR-136-5p expression is decreased in TNBC tissues, and its overexpression suppresses TNBC cell proliferation, migration, and invasion. MiR-136-5p suppression reverses the FAM83H-AS1 silencing-mediated inhibition of TNBC cell proliferation, migration, and invasion, suggesting that FAM83H-AS1 exerts its oncogenic effect by inhibiting miR-136-5p. Our data identify metadherin (MTDH) as the target gene of miR-136-5p, and demonstrate that the MTDH expression is increased in human TNBC tissues, which induces proliferation, migration, and invasion of TNBC cells. Importantly, our in vivo data show that FAM83H-AS1 also promotes tumor growth in TNBC mouse xenografts. Together, our results demonstrate that FAM83H-AS1 functions as an oncogenic lncRNA that regulates miR-136-5p and MTDH expression during TNBC progression, and suggest that targeting the FAM83H-AS1/miR-136-5p/MTDH axis may serve as a novel therapeutic target in TNBC.

Abstract P6-07-04: Mechanosensing calcium channel PIEZO2 accelerates epithelial-mesenchymal transition in triple-negative breast cancer

Abstract Introduction: Breast cancer is the most common female malignancy. Despite improvements in therapeutic options, metastatic disease remains incurable with limited treatments especially in triple-negative breast cancer (TNBC). Clinical outcomes in patients with TNBC continue to be worse as compared to other breast cancer subtypes. Therefore, novel therapeutic targets for TNBC are in urgent need. PIEZO2, which is a transmembrane calcium channel, is known to function as a channel-type mechanosensor in various aspects of mechanotransduction. Recently there have been reports that PIEZO2 may be involved in carcinogenesis and cancer progression. However, the role of PIEZO2 in breast cancer has not been elucidated. We hypothesized that PIEZO2 plays significant roles in progression of TNBC. Methods: To investigate the role of PIEZO2 in human breast cancer patients, The Cancer Genome Atlas (TCGA) breast cancer cohort, in which there are mRNA expression data from RNA-seq and clinical data, was utilized. PIEZO2 expression level was compared among breast cancer subtypes. Patients’ survival was compared based on PIEZO2 expression in each subtype. We used gene set enrichment analysis (GSEA) algorithm to evaluate pathways associated with PIEZO2 expression. To further elucidate the mechanisms of PIEZO2 roles, TNBC cell line, MDA-MB-231 was utilized for in vitro experiments. PIEZO2 expression was downregulated by small interfering RNA (siRNA). Cell viability was quantified by MTT assay. Protein expression was compared by western blot. Results: Breast cancer showed the highest PIEZO2 expression level, among various types of cancers in TCGA. In the breast cancer cohort, PIEZO2 expression level was lower in the TNBC subtype compared to other subtypes (p&amp;lt;0.001). Thus we hypothesized that PIEZO2 has different roles in each subtype. Survival analyses revealed that patients with high expression of PIEZO2 tumors showed significantly worse overall survival (p=0.016) in the TNBC cohort. However, there was no significant difference in the hormone receptor (HR)-positive (p=0.555) and the HER2-positive (p=0.380) cohorts. To explore underlying mechanisms how PIEZO2 high expressing tumors associate with worse prognosis in TNBC, GSEA was conducted. PIEZO2 high expressing tumors enriched epithelial-mesenchymal transition (EMT; NES=1.90, p=0.012) and Angiogenesis (NES=1.91, p&amp;lt;0.001) gene sets, as well as TAZ/YAP gene set (NES=1.57, p=0.028). PIEZO2 knockdown by siRNA significantly suppressed cell viability. This finding was validated by PIEZO inhibitor GSMTx-4 treatment. Further, expression levels of EMT related proteins, such as Vimentin and Snail, were downregulated in the PIEZO2 knockdown MDA-MB-231 cells compared to control cells. Conclusion: We describe a novel signaling pathway mediated by PIEZO2 leading to worse clinical outcomes in patients with TNBC by activation of EMT. Further work is ongoing to validate PIEZO2 as a novel therapeutic target for TNBC. Citation Format: Eriko Katsuta, Marija Vujcic, Shipra Gandhi, Arthur Beyder, Kazuaki Takabe, Mateusz Opyrchal. Mechanosensing calcium channel PIEZO2 accelerates epithelial-mesenchymal transition in triple-negative breast cancer [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 P6-07-04.

Abstract P3-06-06: The importance of p300/CBP (CREBBP)-survivin (BIRC5) for cell cycle and apoptosis in triple negative breast cancer

Abstract In breast cancer, both incidence and mortality have been increasing. Triple negative breast cancer (TNBC), one of breast cancer subtypes, is a heterogeneous nature that is negative for estrogen receptor (ER), progesterone receptor (PR) and human epithelial growth factor receptor type 2 (HER2). Due to the lack of expression of therapeutic targets, new therapeutic strategy and elucidation the mechanism of action in TNBC are strongly desired. Histone acetyltransferases E1A binding protein (p300) and CREB binding protein (CBP) are coactivators of a large number of essential transcription factors that contribute to cell survival and proliferation. p300/CBP (CREBBP) interacts with transcription factors and other proteins through histone acetyltransferase (HAT) and regulates several gene expression. Dysregulation of CREBBP HAT activity could contribute to various diseases, including cancer. It is reported that the high expression of p300 correlates with poor prognosis in breast cancers. However, the mechanism of CREBBP HAT activity remains unclear. We, therefore, focused on CREBBP and clarified its important mechanism in TNBC. In breast cancer cell lines, p300 expression was higher than the normal mammary epithelial cell (MCF10A) in mRNA and protein levels and positively correlated with that of CBP. To evaluate the roles of p300 and CBP in cell survival and proliferation, the loss of function studies was conducted. In TNBC cell line (MDA-MB-231), cell survival and proliferation significantly reduced in p300 knockdown cells. The reduction in cell survival and proliferation was also observed using p300 inhibitor (L002). To examine the mechanism of action for the reduction of cell survival and proliferation in p300 inhibition, cell cycle assay and apoptosis assay were performed. We found that the cell-cycle progression was arrested at the cell cycle G2/M phase and apoptosis induction in p300 knockdown cells. These results suggest that cell cycle G2/M phase arrest and the late stage of apoptosis are caused by p300 inhibition and p300 inhibition enhances the anti-tumor effect. To identify a mechanism responsible for the reduction of cell survival and proliferation in p300 inhibition, antibody array was performed. As a result of this assay and TCGA patients cohorts analysis, we identified survivin (BIRC5), a member of the inhibitor of apoptosis (IAP) family, as a functional novel biomarker of TNBC with significantly higher expression. These results suggest that suppression of BIRC5 through CREBBP inhibitor result in G2/M phase cell cycle arrest and apoptotic cell death in vitro and in vivo. In conclusion, CREBBP-BIRC5 transcriptional complex could be a novel therapeutic target for TNBC. Citation Format: Sunao Tanaka, Natsuki Wariishi, Nobuko Kawaguchi-Sakita, Souichi Adachi, Masakazu Toi, Yasuhiko Kamikubo. The importance of p300/CBP (CREBBP)-survivin (BIRC5) for cell cycle and apoptosis in triple negative breast cancer [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 P3-06-06.

RNA-seq analysis identified hormone-related genes associated with prognosis of triple negative breast cancer.

Triple negative breast cancer (TNBC) is an aggressive subtype of breast cancer that currently lacks effective biomarkers and therapeutic targets required to investigate the diagnosis and treatment of TNBC. Here we performed a comprehensive differential analysis of 165 TNBC samples by integrating RNA-seq data of breast tumor tissues and adjacent normal tissues from both our cohort and The Cancer Genome Atlas (TCGA). Pathway enrichment analysis was conducted to evaluate the biological function of TNBC-specific expressed genes. Further multivariate Cox proportional hazard regression was performed to evaluate the effect of these genes on TNBC prognosis. In this report, we identified a total of 148 TNBC-specific expressed genes that were primarily enriched in mammary gland morphogenesis and hormone levels related pathways, suggesting that mammary gland morphogenesis might play a unique role in TNBC patients differing from other breast cancer types. Further survival analysis revealed that nine genes ( FSIP1, ADCY5, FSD1, HMSD, CMTM5, AFF3, CYP2A7, ATP1A2, and C11orf86) were significantly associated with the prognosis of TNBC patients, while three of them ( ADCY5, CYP2A7, and ATP1A2) were involved in the hormone-related pathways. These findings indicated the vital role of the hormone-related genes in TNBC tumorigenesis and may provide some independent prognostic markers as well as novel therapeutic targets for TNBC.

CircPLK1 sponges miR-296-5p to facilitate triple-negative breast cancer progression.

Aim: To investigate the role of circRNAs in triple-negative breast cancer (TNBC) and the underlying mechanisms. Materials & methods: We performed circRNA microarrays to explore the expression profiles of TNBC cell lines. Experiments in vitro and in vivo were conducted to explore the effects of circPLK1 on tumor proliferation and metastasis as well as the interaction between circPLK1, miR-296-5p and PLK1 in TNBC. Results & conclusion: CircPLK1 was significantly upregulated in TNBC and associated with poor survivals. CircPLK1 knockdown inhibited cell growth and invasion in vitro as well as tumor occurrence and metastasis in vivo. CircPLK1-miR-296-5p-PLK1 axis regulates tumor progression by ceRNA mechanism in TNBC, indicating that circPLK1 may serve as a prognostic factor and novel therapeutic target for TNBC.