Quadruple-negative Breast Cancer Research Articles

Beyond Triple-Negative: High Prevalence of Quadruple-Negative Breast Cancer in African Americans

Quadruple-negative breast cancer (QNBC) is a triple-negative breast cancer (TNBC) subtype that lacks expression of the androgen (AR) receptor. Few studies have focused on this highly aggressive breast cancer, portending worse survival rates. We aimed to determine the following: (1) QNBC’s molecular and clinical characteristics and compare them with other subtypes and (2) QNBC’s association with clinicopathological factors and prognostic markers. We performed immunohistochemical evaluations of ARs on tissue tumor microarrays from FFPE tumor blocks of invasive ductal breast carcinomas in 202 African American women. Univariate analysis was performed using the chi-square test, with survival rates calculated using Kaplan–Meier curves. Overall, 75.8% of TNBCs were AR-negative. Compared to the luminal subtypes, TNBC and QNBC tumors were likely to be a higher grade (p < 0.001); HER2+/AR- and QNBCs were also larger than the other subtypes (p < 0.001). They also expressed increasing mean levels of proteins involved in invasion, such as CD44, fascin, and vimentin, as well as decreasing the expression of proteins involved in mammary differentiation, such as GATA3 and mammaglobin. We found no association between QNBC and stage, recurrence-free survival, or overall survival rates. The high prevalence of TNBC AR-negativity in these women could explain observed worse outcomes, supporting the existence of the unique QNBC subtype.

Beyond Triple-Negative: High Prevalence of Quadruple-Negative Breast Cancer in African Americans

Quadruple-negative breast cancer (QNBC) is a triple-negative breast cancer (TNBC) subtype that lacks expression of the androgen (AR) receptor. Few studies have focused on this highly aggressive breast cancer, portending worse survival rates. We aimed to determine the following: (1) QNBC’s molecular and clinical characteristics and compare them with other subtypes and (2) QNBC’s association with clinicopathological factors and prognostic markers. We performed immunohistochemical evaluations of ARs on tissue tumor microarrays from FFPE tumor blocks of invasive ductal breast carcinomas in 202 African American women. Univariate analysis was performed using the chi-square test, with survival rates calculated using Kaplan–Meier curves. Overall, 75.8% of TNBCs were AR-negative. Compared to the luminal subtypes, TNBC and QNBC tumors were likely to be a higher grade (p < 0.001); HER2+/AR- and QNBCs were also larger than the other subtypes (p < 0.001). They also expressed increasing mean levels of proteins involved in invasion, such as CD44, fascin, and vimentin, as well as decreasing the expression of proteins involved in mammary differentiation, such as GATA3 and mammaglobin. We found no association between QNBC and stage, recurrence-free survival, or overall survival rates. The high prevalence of TNBC AR-negativity in these women could explain observed worse outcomes, supporting the existence of the unique QNBC subtype.

Kinesin Family Member C1 (KIFC1/HSET) Underlies Aggressive Disease in Androgen Receptor-Low and Basal-Like Triple-Negative Breast Cancers.

Quadruple-negative breast cancer (QNBC) lacks traditional actionable targets, including androgen receptor (AR). QNBC disproportionately afflicts and impacts patients of African genetic ancestry. Kinesin family member C1 (KIFC1/HSET), a centrosome clustering protein that prevents cancer cells from undergoing centrosome-amplification-induced apoptosis, has been reported to be upregulated in TNBCs and African-American (AA) TNBCs. Herein, we analyzed KIFC1 RNA levels and their associations with clinical features and outcomes among AR-low and AR-high TNBC tumors in three distinct publicly available gene expression datasets and in the breast cancer gene expression database (bc-GenExMiner). KIFC1 levels were significantly higher in AR-low and basal-like TNBCs than in AR-high and non-basal-like TNBCs, irrespective of the stage, grade, tumor size, and lymph node status. KIFC1 levels were also upregulated in AR-low tumors relative to AR-high tumors among Black and premenopausal women with TNBC. High KIFC1 levels conferred significantly shorter overall survival, disease-free survival, and distant metastasis-free survival among AR-low and basal-like TNBC patients in Kaplan-Meier analyses. In conclusion, KIFC1 levels may be upregulated in AR-low tumors and, specifically, in those of African descent, wherein it may promote poor outcomes. KIFC1 may be an actionable cancer-cell-specific target for the AR-low TNBC subpopulation and could aid in alleviating racial disparities in TNBC outcomes.

Molecular targets and therapeutic strategies for triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is known for its heterogeneous complexity and is often difficult to treat. TNBC lacks the expression of major hormonal receptors like estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2 and is further subdivided into androgen receptor (AR) positive and AR negative. In contrast, AR negative is also known as quadruple-negative breast cancer (QNBC). Compared to AR-positive TNBC, QNBC has a great scarcity of prognostic biomarkers and therapeutic targets. QNBC shows excessive cellular growth and proliferation of tumor cells due to increased expression of growth factors like EGF and various surface proteins. This study briefly reviews the limited data available as protein biomarkers that can be used as molecular targets in treating TNBC as well as QNBC. Targeted therapy and immune checkpoint inhibitors have recently changed cancer treatment. Many studies in medicinal chemistry continue to focus on the synthesis of novel compounds to discover new antiproliferative medicines capable of treating TNBC despite the abundance of treatments currently on the market. Drug repurposing is one of the therapeutic methods for TNBC that has been examined. Moreover, some additional micronutrients, nutraceuticals, and functional foods may be able to lower cancer risk or slow the spread of malignant diseases that have already been diagnosed with cancer. Finally, nanomedicines, or applications of nanotechnology in medicine, introduce nanoparticles with variable chemistry and architecture for the treatment of cancer. This review emphasizes the most recent research on nutraceuticals, medication repositioning, and novel therapeutic strategies for the treatment of TNBC.

VNLG-152R and its deuterated analogs potently inhibit/repress triple/quadruple negative breast cancer of diverse racial origins in vitro and in vivo by upregulating E3 Ligase Synoviolin 1 (SYVN1) and inducing proteasomal degradation of MNK1/2.

Triple-negative breast cancer (TNBC) and its recently identified subtype, quadruple negative breast cancer (QNBC), collectively account for approximately 13% of reported breast cancer cases in the United States. These aggressive forms of breast cancer are associated with poor prognoses, limited treatment options, and lower overall survival rates. In previous studies, our research demonstrated that VNLG-152R exhibits inhibitory effects on TNBC cells both in vitro and in vivo and the deuterated analogs were more potent inhibitors of TNBC cells in vitro. Building upon these findings, our current study delves into the molecular mechanisms underlying this inhibitory action. Through transcriptome and proteome analyses, we discovered that VNLG-152R upregulates the expression of E3 ligase Synoviolin 1 (SYVN1), also called 3-hydroxy-3-methylglutaryl reductase degradation (HRD1) in TNBC cells. Moreover, we provide genetic and pharmacological evidence to demonstrate that SYVN1 mediates the ubiquitination and subsequent proteasomal degradation of MNK1/2, the only known kinases responsible for phosphorylating eIF4E. Phosphorylation of eIF4E being a rate-limiting step in the formation of the eIF4F translation initiation complex, the degradation of MNK1/2 by VNLG-152R and its analogs impedes dysregulated translation in TNBC cells, resulting in the inhibition of tumor growth. Importantly, our findings were validated in vivo using TNBC xenograft models derived from MDA-MB-231, MDA-MB-468, and MDA-MB-453 cell lines, representing different racial origins and genetic backgrounds. These xenograft models, which encompass TNBCs with varying androgen receptor (AR) expression levels, were effectively inhibited by oral administration of VNLG-152R and its deuterated analogs in NRG mice. Importantly, in direct comparison, our compounds are more effective than enzalutamide and docetaxel in achieving tumor growth inhibition/repression in the AR+ MDA-MD-453 xenograft model in mice. Collectively, our study sheds light on the involvement of SYVN1 E3 ligase in the VNLG-152R-induced degradation of MNK1/2 and the therapeutic potential of VNLG-152R and its more potent deuterated analogs as promising agents for the treatment of TNBC across diverse patient populations.

Subcellular expression pattern and clinical significance of CBX2 and CBX7 in breast cancer subtypes.

Chromobox (CBX)2 and CBX7, members of CBX family protein, show diverse expression patterns and contrasting roles in certain cancers. We aimed to investigate the subcellular expression patterns and clinical significances of CBXs in breast cancer (BC) subtypes, which have heterogeneous clinical course and therapeutic responses. Among the subtypes, the triple-negative BC (TNBC) is a heterogeneous group that lacks specific markers. We categorized TNBC into quadruple-negative BC (QNBC) and TNBC, based on androgen receptor (AR) status, to make the groups more homogeneous. Immunohistochemistry for CBX proteins was performed on 323 primary invasive BC tissues and their clinical significances were analyzed. Cytoplasmic CBX2 (CBX2-c) was linked to adverse clinicopathological factors and TNBC and QNBC subtypes. In contrast, nuclear CBX7 (CBX7-n) was associated with favorable parameters and luminal A subtype. CBX2-c expression increased progressively from that in benign lesions to that in in situ carcinomas and invasive cancers, whereas CBX7-n and AR expressions showed sequential downregulation. AR was lower in metastatic tissues compared to matched primary cancer tissues. We speculate that the upregulation of CBX2-c and downregulation of CBX7-n could play a role in breast oncogenesis and an adverse clinical course, suggesting them as potential prognostic markers and therapeutic targets in invasive BCs.

ACSL4: biomarker, mediator and target in quadruple negative breast cancer

Breast cancer is a heterogeneous disease for which effective treatment depends on correct categorization of its molecular subtype. For the last several decades this determination has relied on hormone receptor status for estrogen, progesterone and HER2. More recently, gene expression data have been generated that further stratify both receptor-positive and receptor-negative cancers. The fatty acid-activating enzyme, ACSL4, has been demonstrated to play a role in the malignant phenotype of a variety of cancers, including breast. This lipid metabolic enzyme is differentially expressed as a function of subtype in breast tumors, with highest expression observed in the mesenchymal (claudin low) and basal-like subtypes. Here we review data that support the potential of utilizing ACSL4 status as both a biomarker of molecular subtype and a predictor of response to a variety of targeted and non-targeted treatment regimens. Based on these findings, we suggest 3 expanded roles for ACSL4: 1. as a biomarker for classification of breast cancer subtypes; 2. as a predictor of sensitivity to hormone-based and certain other therapies; and 3. as a target for the development of new treatment modalities.

The impact of Quadruple Negative Breast Cancer in prognosis

The impact of Quadruple Negative Breast Cancer in prognosis

Abstract 4628: Profiling the tumor microenvironments of triple- and quadruple-negative breast cancers

Abstract Triple-negative breast cancer (TNBC) is a heterogeneous breast cancer subtype that lacks expression of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Approximately 15%-20% of breast cancers are triple-negative. Based on expression of the androgen receptor (AR), TNBC can be categorized as AR-positive (AR+ TNBC) or AR-negative (quadruple-negative breast cancer, QNBC). Studies have reported that the loss of AR expression is associated with poor prognoses. Recent evidence suggests that QNBCs disproportionately affect women of African descent and contributes to poor overall survival. QNBC is a more aggressive disease compared to TNBC, and patients with QNBC currently have no treatment options beyond chemotherapy. Data from interrogating public databases such as TCGA indicates that QNBC is distinct from TNBC in molecular makeup, particularly in immune tumor microenvironment. Currently, QNBC is not considered distinct from the broader TNBC subtype, hence a comprehensive molecular characterization is lacking. We aim to examine differences between the TNBC and QNBC tumor microenvironments that consist of both immune and stromal components. We analyzed RNA expression data from the METABRIC (TNBC= 11, QNBC= 185) and TCGA (TNBC= 29, QNBC= 103) datasets. Based on AR transcript expression, patients with TNBC were stratified into AR-low (considered QNBC) and AR-high (deemed ‘true’ TNBC) groups. The analytical immune tools - CIBERSORTx and xCELL were used to analyze the RNA-Seq data. CIBERSORTx can distinguish 22 mature human hematopoietic populations and provides abundance of member cell types in a mixed cell population, from gene expression data. xCELL is a gene signature-based method that can perform cell type enrichment analysis from gene expression for 64 immune and stromal cell types. Thus, xCell can discriminate between closely related cell types. Using these immune tools, the tumor microenvironments of the TNBC and QNBC groups were compared. Correlations between individual immune and stromal components with patient survival probability were assessed. Significant differences (p-value <0.05) in several immune and stromal cell types were noted when comparing the TNBC and QNBC groups within these datasets. CIBERSORTx and xCELL yielded both unique and common sets of cell types. Notably, significant differences in the stroma score (a composite score of stromal cell types provided by xCELL) were observed between TNBC and QNBC in both the METABRIC and TCGA datasets. These immune tools are based on different methodologies and our results show that they can provide complementary information. Our data suggest that QNBC and TNBC have distinct tumor microenvironments, and that QNBC should be considered as an independent breast cancer subtype that warrants comprehensive characterization. Citation Format: Geetanjali Saini, Manali Rupji, Mahak Bhargava, Sunil Badve, Ritu Aneja. Profiling the tumor microenvironments of triple- and quadruple-negative breast cancers. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4628.

P286 Quadruple Negative Breast Cancer (QNBC): outcomes in survival and comparison with the classic phenotype of TNBC

P286 Quadruple Negative Breast Cancer (QNBC): outcomes in survival and comparison with the classic phenotype of TNBC

Abstract C036: Correlation of Kaiso and androgen receptor expression in women of African ancestry with triple-negative breast cancer

Abstract Breast cancer (BCa) is the most frequently diagnosed female cancer and a leading cause of female deaths worldwide, regardless of increased awareness and improved therapies. Triple-negative breast cancer (TNBC) is one of the most challenging BCa subtypes as it is highly heterogeneous, metastatic in nature and has limited targeted therapies. TNBC is most prevalent in young women of African ancestry (WAA), who despite having lower BCa rates, have a disproportionately higher mortality rate compared to women of European ancestry (WEA). However, the cause for this racial disparity is currently unknown, thus highlighting the importance of unraveling the genetic and molecular factors that contribute to TNBC in WAA. Our lab previously showed that the transcription factor Kaiso may be linked to this disparity as it contributes to increased metastasis and mortality in WAA TNBC patients. Interestingly, multiple studies have indicated that WAA TNBC tissues also express less Androgen Receptor (AR) than WEA TNBC tissues, supporting the existence of a novel BCa subtype – quadruple-negative breast cancer (QNBC). Notably, in silico analysis revealed several Kaiso binding sites in the AR promoter region, and that high Kaiso and low AR expression correlated with poorer overall survival in BCa patients. Thus, we hypothesized that high Kaiso and low AR expression could be contributing to the increased mortality in WAA with TNBC. This study seeks to examine the relationship between Kaiso and AR, the clinical significance of this relationship and its role, if any, in TNBC racial disparities. Using tissue microarrays (TMAs) and immunohistochemistry (IHC), we found reduced and cytoplasmic AR expression in WAA compared to WEA. Moreover, preliminary findings from western blot analyses showed an increase in AR expression in response to Kaiso depletion in TNBC cells. These findings suggest that AR could be a bona fide Kaiso target gene and that there may be clinical relevance of high Kaiso, and low AR expression in BCa survival, especially in patients with an African heritage. Ongoing experiments are focused on determining if Kaiso directly associates with the endogenous AR promoter region and discerning the link between high Kaiso and low AR expression in TNBC racial disparities. A significant correlation between Kaiso and AR expression will help to validate the existence of QNBC in WAA and support Kaiso and AR as clinically relevant prognostic markers for TNBC, especially in WAA. Citation Format: Stephanie Ali Fairbairn, Robert Cowan, Juliet M. Daniel, Shawn M. Hercules. Correlation of Kaiso and androgen receptor expression in women of African ancestry with triple-negative breast cancer [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr C036.

MicroRNAs within the Basal-like signature of Quadruple Negative Breast Cancer impact overall survival in African Americans

We previously found that QNBC tumors are more frequent in African Americans compared to TNBC tumors. To characterize this subtype further, we sought to determine the miRNA–mRNA profile in QNBC patients based on race. Both miRNA and mRNA expression data were analyzed from TCGA and validated using datasets from the METABRIC, TCGA proteomic, and survival analysis by KMPLOT. miRNA–mRNAs which include FOXA1 and MYC (mir-17/20a targets); GATA3 and CCNG2 (mir-135b targets); CDKN2A, CDK6, and B7-H3 (mir-29c targets); and RUNX3, KLF5, IL1-β, and CTNNB1 (mir-375 targets) were correlated with basal-like and immune subtypes in QNBC patients and associated with a worse survival. Thus, QNBC tumors have an altered gene signature implicated in racial disparity and poor survival.

Clinical Utility of Predictive Markers in Triple Negative Breast Cancer

Background & Objective: Triple negative breast cancer (TNBC) is an aggressive disease and visceral metastasis occurs due to unavailability of targeted therapy. This study was undertaken to evaluate incidence of predictive markers in TNBC which further guide to select adjuvant treatment. Method: This study evaluated androgen receptor (AR), PI3K, mTOR, c-myc and TLE3 expression by immunohistochemistry on tumor tissues of 50 untreated TNBC. The protein expression of markers was correlated with clinicopathological parameters and disease status. The data was analysed statistically using SPSS software version 20. Results: The incidence of expression of AR (18%) and TLE3 (22%) was found lower and c-myc (88%), PI3K (74%) and mTOR (86%) was found higher in TNBC. 82% were quadruple negative breast cancer. PI3K expression was seen higher in post-menopausal patients and mTOR expression was significantly higher in smaller tumor size and high BR score tumors with a trend in younger patients. Overexpression of c-myc was associated with post-menopausal status, early stage disease and high BR score tumors. These markers when intercorrelated, a significant positive correlation was noted of PI3K with mTOR, and mTOR with c-myc. Further, c-myc emerged as significant prognosticator predicting higher relapse rate in quadruple negative breast cancer, and death rate in total patients and quadruple negative breast cancer in multivariate analyses. Interpretation & Conclusion: Identification of potentially actionable targets is essential to plan adjuvant therapy for better patient management of TNBC. Keywords: predictive markers, c-myc, PI3K, mTOR, TNBC

Racial Disparity in Quadruple Negative Breast Cancer: Aggressive Biology and Potential Therapeutic Targeting and Prevention.

Simple SummaryQuadruple negative breast cancer (QNBC), a subgroup of triple negative BC, has emerged as a highly aggressive BC subtype that disproportionately afflicts and impacts Black/African-American (AA) women. In this article, we review molecular distinctions in Black/AA and White/European-American (EA) QNBC biology as well as address potential non-genetic risk factors that could be underlying this racially disparate burden. We aim to provide deeper insight and provide a framework for novel discovery of actionable therapeutic targets and identify lifestyle changes to improve outcomes for Black/AA QNBC patients.Black/African-American (AA) women, relative to their White/European-American (EA) counterparts, experience disproportionately high breast cancer mortality. Central to this survival disparity, Black/AA women have an unequal burden of aggressive breast cancer subtypes, such as triple-negative breast cancer (ER/PR-, HER2-wild type; TNBC). While TNBC has been well characterized, recent studies have identified a highly aggressive androgen receptor (AR)-negative subtype of TNBC, quadruple-negative breast cancer (ER/PR-, HER2-wildtype, AR-; QNBC). Similar to TNBC, QNBC disproportionately impacts Black/AA women and likely plays an important role in the breast cancer survival disparities experienced by Black/AA women. Here, we discuss the racial disparities of QNBC and molecular signaling pathways that may contribute to the aggressive biology of QNBC in Black/AA women. Our immediate goal is to spotlight potential prevention and therapeutic targets for Black/AA QNBC; ultimately our goal is to provide greater insight into reducing the breast cancer survival burden experienced by Black/AA women.

Programmed death-ligand 1 (PD-L1) expression predicts response to neoadjuvant chemotherapy in triple-negative breast cancer: a systematic review and meta-analysis

Background In patients with metastatic triple-negative breast cancer (TNBC), programmed death-ligand 1 (PD-L1) expression has been demonstrated to predict response to immunotherapy. It is unclear whether PD-L1 expression measured with currently available validated assays can predict chemotherapy response in patients with non-metastatic TNBC. Methods We conducted a systematic review and meta-analysis of clinical studies to assess the PD-L1 expression as a predictor of response to chemotherapy in non-metastatic TNBC using validated assays. The primary endpoint was pathological complete response (pCR) rate to neoadjuvant chemotherapy. Secondary endpoints included the prevalence of PD-L1 expression in non-metastatic TNBC and its impact on disease-free survival (DFS) and overall survival (OS). Moreover, RNA sequence data from the TCGA breast cancer cohort was used to define the relationship between PDCD1 expression and response to chemotherapy and prognosis. Results Nineteen studies were eligible for the meta-analysis with a total of 2403 patients with non-metastatic TNBC disease. The PD-L1-positive cohort had a significantly higher likelihood of achieving pCR with neoadjuvant chemotherapy (pooled odds ratio = 1.95; 95% CI = 1.39–2.73, p < 0.0001). In studies which reported long-term outcomes, PD-L1 positivity was associated with significantly better DFS and OS compared to PD-L1 negative patients (pooled hazard ratio = 0.51; 95% CI = 0.35–0.74, p < 0.0001 and 0.51; 95% CI = 0.27–0.94, p = 0.031, respectively). Transcriptomic data suggested that PD-L1 expression is a surrogate marker for the upregulation of key immune-related genes that mediate response to chemotherapy in TNBC. Conclusion This analysis clearly shows that patients with PD-L1 positive TNBC respond better to neoadjuvant chemotherapy and are associated with better survival outcomes compared to patients with PD-L1 negative tumours. The newly distinct quadruple negative breast cancer (QNBC) subtype should be defined as the BC subtype with the poorest outcome in the non-metastatic setting, highlighting the need for more aggressive therapy approaches.

Abstract 3682: Quadruple negative breast tumors in African American women express factors associated with worse prognosis compared to triple negative tumors

Abstract Introduction: Quadruple negative breast cancer (QNBC) is defined by the absence of androgen (AR), estrogen (ER), progesterone (PR) receptors and human epidermal growth factor (HER2) expression. This subset of triple negative breast cancer (TNBC) has been described as unique to African American (AA) women and represents about 67-90% of all TNBC. Yet, there are limited clinical and therapeutic studies focused on this new subset of breast cancer (BCa) that is highly aggressive and portends a worse survival compared to AR positive Bca subtypes. The objectives of our study were to 1) determine the molecular and clinical characteristics of QNBC and compare them with other BCa subtypes and 2) determine the association of QNBC with clinicopathological factors and prognostic markers. Materials and Methods: Tissue arrays were constructed from FFPE tumor blocks of invasive ductal breast carcinomas in 202 AAs, diagnosed at Howard University from 2000 to 2010. Two separate tissue cores of IDC represented each surgical case in the TMA and was linked to an Institutional Review Board-approved database of demographic and clinical data. Using a microtome, 5-µm sections were cut from the TMA blocks and mounted onto Superfrost Plus microscope slides. Sections were stained with a mouse monoclonal antibody against AR (Clone AR 441, DAKO). Immunohistochemistry for AR was considered positive if ≥10% of tumor cells showed nuclear staining. Bivariate analysis was performed via χ2 analysis and survival data was calculated via Kaplan-Meier curves (SPSS v28.0.0). Results: The most prevalent breast cancer subtype was luminal A (ER+ or PR+, HER2−; 43.5%), followed by TNBC (33.7%). Of the 67 TNBCs on the array, 63 had AR data; 33 (52%) of the TNBCs were AR negative. Greater than 70% of all tumors were stage I and II; and Grade 3 comprised 67.4% of the tumors. QNBC tumors were more likely to be higher grade (p&amp;lt;0.001) and larger in size (p=0.05) compared to other subtypes. There was also a trend for increased metastases in QNBCs (Luminal and HER2 tumors=11.2%; TNBC=13.3%; AR negative= 18.8%; and QNBC=20.8% (p=0.15)). Compared to TNBCs, QNBCs were larger (p=0.048), more likely to express markers associated invasion (Fascin, p=0.004) and reduced survival (Vimentin, p=0.014). There was a trend for increased expression of markers associated with metastases: Mammaglobin (expressed in 30.8% of TNBCs compared to 52.1% of QNBCs; p=0.17) and CD105 (expressed in 6.7% of TNBCs compared to 27.1% of QNBCs; p=0.097). There was no association between QNBC and stage, recurrence-free survival, or overall survival. Conclusion: In our study of AAs, a statistically significant association was noted between QNBC tumors and poorer prognosis. The high prevalence of AR negativity of TNBCs in AAs could explain observed worse outcomes and supports the existence of a unique subtype of Bca known as QNBC, worthy of scientific attention. Citation Format: Oluwadamilola Oladeru, Yasmine Kanaan, Tammy Naab, Luisel J. Ricks-Santi. Quadruple negative breast tumors in African American women express factors associated with worse prognosis compared to triple negative tumors [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 3682.

Abstract 1781: Up284, a novel inhibitor to treat quadruple negative breast cancer

Abstract Quadruple negative breast cancer (QNBC), lacking the expression of ER (estrogen receptor), PR (progesterone receptor), HER2 (human epidermal growth factor receptor 2) and AR (androgen receptor), is the breast cancer subtype with the worst prognosis, and QNBC disproportionately afflicts African Americans. It has no standard-of-care treatment targets and thus efficacious and safe treatments are urgently sought for this unmet medical need, and to address the disparity in breast cancer outcomes. The current proposal is motivated by data showing elevated expression of proteasome subunit RPN13 is associated with both African American race and lower survival in QNBC patients, that RPN13 selectively targeted by a small molecule Up284 developed by Up Therapeutics. Both triple negative breast cancer and QNBC cell lines show evidence of greater vulnerability to proteasome inhibitors. However, licensed 20S proteasome inhibitors, e.g. bortezomib, have proven ineffective against solid tumors, with emergence of resistance, and dose limiting toxicities including thrombocytopenia and neutropenia. Up284 has a target and structure designed to overcome the limitations of the licensed drugs with respect to drug resistance. Up284 blocks substrate recognition and deubiquitination rather than just one of the three 20S catalytic activities), poor activity against solid tumors (Up284 has a novel spiro structure with evidence of improved drug access to tumor as compared to peptide-based 20S inhibitors), key toxicities of thrombocytopenia and neutropenia (unlike 20S inhibitors, Up284 does not target the immunoproteasome expressed by hematopoietic cells and does not show these toxicities). Up284 shows broad anticancer activity in vitro, including against QNBC lines with a robust therapeutic index, a promising safety profile and pharmacodynamics, and the ability to control xenograft tumor. By inhibiting proteasome ubiquitin receptor RPN13 function and its associated deubiquitinase activity, Up284 triggers more rapid accumulation and increased molecular weight polyubiquinated protein aggregates than is induced by 20S inhibitors. These toxic misfolded protein aggregates produce an unresolved ER stress, activate the canonical Unfolded Protein Response (UPR) signaling cascade and more rapidly triggers apoptosis than 20S inhibitor. The safety parameters and promising efficacy of Up284 against breast cancer lines encourages us to validate Up284 efficacy in more QNBC lines and animal models. We discuss Up284 efficacy and pharmacological analysis in our presentation. Citation Format: Balasubramanyam Karanam, Clayton Yates, Ravi Anchoori. Up284, a novel inhibitor to treat quadruple 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 1781.

34P Quadruple-negative breast cancer (PD-L1-negative triple-negative breast cancer, TNBC): Poorer response to chemotherapy and poorer survival compared to other TNBCs: A systematic review and meta-analysis

PD-L1 expression has shown to be predictive of response to immunotherapy in patients with metastatic triple-negative breast cancer (TNBC). It is unclear if PD-L1 expression by currently available validated assays has predictive capacity for response to chemotherapy in patients with non-metastatic TNBC.

Potential epigenetic modifications implicated in triple- to quadruple-negative breast cancer transition: a review.

Current research on triple-negative breast cancer (TNBC) has resulted in delineation into the quadruple-negative breast cancer (QNBC) subgroup. Epigenetic modifications such as DNA methylation, histone posttranslational modifications and associated changes in chromatin architecture have been implicated in breast cancer pathogenesis. Herein, the authors highlight genes with observed epigenetic modifications that are associated with more aggressive TNBC/QNBC pathogenesis and possible interventions. Advanced literature searches were done on PubMed/MEDLINE, Scopus and Google Scholar. The results suggest that nineepigenetically altered genes/differentially expressedproteins in addition to the downregulated androgen receptor are associated with TNBC aggressiveness and could be implicated in the TNBC to QNBC transition. Thus, restoring the normal expression of these genes via epigenetic reprogramming could be therapeutically beneficial to TNBC and QNBC patients.

The functional significance and cross-talk of non-coding RNAs in triple negative and quadruple negative breast cancer.

One of the leading causes of cancer-related deaths worldwide is breast cancer, among which triple-negative breast cancer (TNBC) is the most malignant and lethal subtype. This cancer accounts for 10-20% of all breast cancer deaths. Proliferation, tumorigenesis, and prognosis of TNBC are affected when the androgen receptor (AR) is not expressed, and it is classified as quadruple negative breast cancer (QNBC). Non-coding RNAs, such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), play a significant role in tumorigenesis by virtue of their oncogenic and tumor-suppressive properties. To regulate tumorigenesis, miRNAs interact with their target mRNAs and modulate their expression, whereas lncRNAs can either act alone or interact with miRNAs or other molecules through various signaling pathways. Conversely, circRNAs regulate tumorigenesis by acting as miRNA sponges predominantly. Recently, non-coding RNAs were studied comprehensively for their roles in tumor proliferation, progression, and metastasis. As a result of existing studies and research progress, non-coding RNAs have been implicated in TNBC, necessitating their use as biomarkers for future diagnostic applications. In this review, the non-coding RNAs are explicitly implicated in the regulation of breast cancer, and their cross-talk between TNBC and QNBC is also discussed.