Decoding circulating neutrophil phenotypes in triple-negative breast cancer via optimized single-cell RNA sequencing.

Background: Breast cancer is currently the leading cause of cancer morbidity and mortality among Algerian women. To date, triple negative breast cancer (TNBC) shows substantial overlap with basal type cancer and it is associated with aggressive tumor behavior, poor prognosis and BRCA1 mutations. In the present study, we screened for the prevalence of BRCA1 and BRCA2 germline mutations in a cohort of 169 TNBC patients using PCR-Sanger sequencing and NGS with a cancer panel of 30 hereditary cancer genes or BRCA1/BRCA2 genetic test. Materials and Methods: 169 TNBC patients and their relatives were referred trough several public hospitals from six years (2013-2019). BRCA1 germline mutation was screened using PCR-Sanger sequencing in 66 TNBC patients with strong family history of breast and ovarian cancer and 103 sporadic TNBC patients including all exons where a mutation was previously found in Algerian population (exons 2, 3, 4, 10, 17 and 19). BRCA2 germline mutation was screened using PCR-Sanger sequencing in 24 TNBC patients with strong family history of breast cancer including all exons where a mutation was previously found in Algerian patients (exons 10 and 22). In addition, nine (9) TNBC patients with strong family history of breast and ovarian cancer were analyzed by NGS using BRCA1 and BRCA2 test or a cancer panel of 30 hereditary genes (Colors genomics). Results: The analysis of the genomic DNA samples of 169 TNBC patients revealed that 15 patients carried pathogenic germline variants in BRCA1 gene and three patients carried pathogenic variants in BRCA2 gene (10.65%). Eight distinct germline mutations in BRCA1 have been detected in this study: c.83_84delTG, c.181T>G, c.798_799delTT, c.505C>T, c.923_924delGC, c.2125_2126insA, c.5257A>G and deletion of exon 15. Interestingly, the recurrent and specific mutation c.83_84delTG has been detected in 4 unrelated TNBC patients. The pathogenic variant c.2125_2126insA has been detected in three unrelated families and also in the first relatives of 2 patients. The rare likely pathogenic variant BRCA1 c.5257A>G/p.Arg1753Gly has been detected in young female TNBC patient. The Del exon 15 in BRCA1 has been detected in two unrelated patients. Three distinct germline mutations in BRCA2 have been detected in three TNBC patients: c.1813dupA, c.7654dupA and c.8485C>T. Interestingly, these three mutations are reported for the first time in Algerian population. The c.1813dupA and c.8485C>T pathogenic variants have been detected in two young female TNBC patients with a family history of male breast cancer. Conclusions: In the current study, we detected recurrent germline mutations in BRCA1 gene in early onset TNBC patients. BRCA2 pathogenic variants have also been detected in young female TNBC patients. TNBC immunophenotype should be considered as an additional criterion for genetic counselling and testing of BRCA genes in Algerian women with early onset breast cancer. Citation Format: Farid Cherbal, Chiraz Mehemmai, Hadjer Gaceb, Hassen Mahfouf, Kada Boualga. BRCA1 and BRCA2 germline mutational spectrum in Algerian triple negative breast cancer (TNBC) patients [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 1451.

Triple-negative breast cancer (TNBC) has the worst prognosis among all subtypes of breast cancer. CUE domain-containing protein-2 (CUEDC2) protein has reported to confer endocrine resistance in breast cancer by down-regulation of estrogen receptor α (ERα) expression. However, the function of CUEDC2 in TNBC subtype is unclear. Here, we showed CUEDC2 is expressed in triple-negative breast cancer and associated with its malignant phenotype. Knockdown of CUEDC2 not only inhibits TNBC cell proliferation, clone formation, migration, and invasion, but also suppresses TNBC stem cell mammosphere formation ability and cancer stem cell markers expression. While over-expression of CUEDC2 enhances its cell malignant phenotype. Furthermore, we determined that the ARM domain of β-catenin interacts with CUE domain of CUEDC2 through immunoprecipitation and pull-down assay. In the 34 TNBC samples, the expression levels of CUEDC2 and β-catenin also showed a positive correlation. Taken together, our study revealed CUEDC2 is associated with malignant phenotype and breast cancer stem cell properties of TNBC by interacting with β-catenin, and suggested that CUEDC2 may be a potential promising prognosis and therapy target for TNBC. Citation Format: Shuyan Han, Hai-Bo Han, Yan-Na Jiao, Pang-Kuo Lo, Yuan Yao, Qun Zhou, Ping-Ping Li. CUCDC2 regulates malignant phenotype of triple-negative breast cancer through interacting with â-catenin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 165.

Background: triple-negative breast cancer (TNBC) is associated with hereditary and environmental risk factors plus an overall worse prognosis compared to other Breast Cancer (BC) subtypes. While TNBC risk factors, prevalence, clinical characteristics and prognosis may vary throughout different populations, limited data on Latin American patients forces clinical decisions to be based predominantly on data coming from non-Hispanic women. To obtain local epidemiological information, regarding risk factors and clinical outcomes, we analysed the largest Chilean BC registry. Methods: we conducted a retrospective population-cohort study involving females with any stage TNBC, treated at a community hospital (mid-low income) and at an academic private hospital (high income), between the years 2010 and 2021. Risk factors, reason for consultation, clinical and pathological characteristics and prognosis were separately analysed for both TNBC and non-TNBC subgroups. Univariate and multivariate analyses were performed to identify prognostic factors for survival on TNBC patients. Results: From 5,806 patients, 647 (11.2%) were identified as TNBC. Compared to non-TNBC patients, women were younger (median age 55.2 vs. 57.2, p=0.0001), with 15.8% of TNBC patients having been diagnosed before the age of 40 compared to 9.6% in non-TNBC (p= 0.0001). TNBC had a significantly lower screen-detected cancer rate (14.5% vs. 31.6% p= 0.0001) and worse stage at diagnosis. No differences were seen between patients seen at a community hospital and private centre, for both TNBC rate and stage. Other risk factors such as parity, age at first gestation, menarche, hormone therapy replacement and obesity showed no significant differences between TNBC and no-TNBC patients (table 1). With a median follow up of 57 months, 5-year overall survival (OS) and BC specific death were significantly shorter for TNBC compared to non-TNBC (76.4% vs 88.1% and 78.9% vs 91.2%, respectively; p=0.0001) (table 2). In the multivariate analysis, TN subtype (HR=2.3, p=0.0001), stage (HR=2.05 for stage II vs stage I, HR=7.04 for stage III vs. stage I, p=0.0001), lower income (HR= 1.64, p=0.0001), and non-screened detected BC (HR=1.32, p=0.03) were all associated with worse overall survival (table 3). Conclusion: This is the first study focusing on TNBC characteristics in Chilean BC patients and to our knowledge, the largest performed in a Latin American population. We identified a lower proportion of TNBC patients when compared with data reported from other LA groups and worldwide, a very low screen detected cancer rate and as expected significantly lower TNBC survival rate compared to non-TNBC women. While TNBC patients were younger compared to the non-TNBC group, this age difference was marginal compared to other reported studies. Community hospital patients (with mid-low income) were associated with lower survival rates for both all-cause mortality and BC specific survival, regardless of a similar stage distribution at diagnosis. Reflecting an underlying interaction between social and biological factors that needs to be addressed. Table 1. Patient characteristics: Triple-negative versus noN-triple negative breast cancer BMI: Body mass index; FH: Family history * Difference is statistically significant. Table 2. Survival comparison in triple-negative versus non-triple negative breast cancer * Difference is statistically significant. Table 3. Cox Regression Multivariate analysis * Difference is statistically significant. Citation Format: Benjamin Walbaum, FRANCISCO ACEVEDO, Catherine Bauerle, Mauricio Camus, Manuel Manzor, Raul Martinez, Paulina Veglia, Marisel Navarro, Constanza Guerra, Francisco Dominguez, Tomas Merino, Lidia Medina, CÉSAR SÁNCHEZ. Real-world data of clinical characteristics, risk factors and outcomes of Chilean triple-negative breast cancer patients [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-03-19.

Triple-negative breast cancer (TNBC) is associated with aggressive tumor behavior, poor prognosis and BRCA1 mutations. There are limited data regarding TNBC among Algerian women. In this study, we sought to determine clinical and tumor characteristics associated with TNBC. We also screened for the prevalence of BRCA1 mutations in unselected cohort of TNBC patients. Clinical and tumor characteristics data of 877 breast cancer patients diagnosed between 2011 and 2015, were collected from cancer registry of public hospital of Rouiba. Patients were divided in two groups: those with TNBC and those with other breast cancer subtypes. Differences between the two groups with regard to clinical and tumor characteristics were compared using Fisher's exact test. BRCA1 mutations analysis was performed in unselected cohort of 103 women with TNBC, including all exons where a mutation was previously found in Algerian population (exons 2, 3, 5, 11). The median age at diagnosis for TNBC and non-TNBC patients was 47.4years and 49.4years, respectively. The proportion of TNBC was 19.95%. Our data showed significant differences in menopausal status, TNM stage, histological type, tumor histological grade, Ki67 expression and family history of breast cancer between TNBC and non-TNBC patients. Four distinct deleterious mutations in BRCA1 gene were detected in eight young TNBC patients. TNBC is associated with young age, poor histopathological characteristics and family history of breast cancer. BRCA1 mutations have been detected in young TNBC patients. TNBC phenotype should be added as criterion to screen for BRCA1 mutations in Algerian women.

e12565 Background: HER2-low could be found in some patients with triple-negative breast cancer (TNBC). However, its potential impacts on clinical features and tumor biological characteristics in TNBC remain unclear. Methods: We enrolled 251 consecutive TNBC patients retrospectively, including 157 HER2-low (HER2low) and 94 HER2-negtive (HER2neg) patients to investigate the clinical and prognostic features. Then, we performed single-cell RNA sequencing (scRNA-seq) with another seven TNBC samples (HER2neg vs. HER2low, 4 vs. 3) prospectively to further explore the differences of tumor biological properties between the two TNBC phenotypes. The underlying molecular distinctions were also explored and then verified in the additional TNBC samples. Results: Compared with HER2neg TNBC, HER2low TNBC patients exhibited malignant clinical features with larger tumor size ( P = 0.04), more lymph nodes involvement ( P = 0.02), higher histological grade of lesions ( P < 0.001), higher Ki67 status ( P < 0.01), and a worse prognosis ( P < 0.001; HR [CI 95%] = 3.44 [2.10-5.62]). Cox proportional hazards analysis showed that neoadjuvant systemic therapy, lymph nodes involvement and Ki67 levels were prognostic factors in HER2low TNBC but not in HER2neg TNBC patients. scRNA-seq revealed that HER2low TNBC which showed more metabolically active and aggressive hallmarks, while HER2neg TNBC exhibited signatures more involved in immune activities with higher expressions of immunoglobulin-related genes ( IGHG1, IGHG4, IGKC, IGLC2); this was further confirmed by immunofluorescence in clinical TNBC samples. Furthermore, HER2low and HER2neg TNBC exhibited distinct tumor evolutionary characteristics. Moreover, HER2neg TNBC revealed a potentially more active immune microenvironment than HER2low TNBC, as evidenced by positively active regulation of macrophage polarization, abundant CD8+ effector T cells, enriched diversity of T-cell receptors and higher levels of immunotherapy-targeted markers, which contributed to achieve immunotherapeutic response. Conclusions: This study suggests that HER2low TNBC patients harbor more malignant clinical behavior and aggressive tumor biological properties than the HER2neg phenotype. The heterogeneity of HER2 may be a non-negligible factor in the clinical management of TNBC patients. Our data provides new insights into the development of a more refined classification and tailored therapeutic strategies for TNBC patients.

BackgroundHER2-low could be found in some patients with triple-negative breast cancer (TNBC). However, its potential impacts on clinical features and tumor biological characteristics in TNBC remain unclear.MethodsWe enrolled 251 consecutive TNBC patients retrospectively, including 157 HER2-low (HER2low) and 94 HER2-negtive (HER2neg) patients to investigate the clinical and prognostic features. Then, we performed single-cell RNA sequencing (scRNA-seq) with another seven TNBC samples (HER2negvs. HER2low, 4 vs. 3) prospectively to further explore the differences of tumor biological properties between the two TNBC phenotypes. The underlying molecular distinctions were also explored and then verified in the additional TNBC samples.ResultsCompared with HER2neg TNBC, HER2low TNBC patients exhibited malignant clinical features with larger tumor size (P = 0.04), more lymph nodes involvement (P = 0.02), higher histological grade of lesions (P < 0.001), higher Ki67 status (P < 0.01), and a worse prognosis (P < 0.001; HR [CI 95%] = 3.44 [2.10–5.62]). Cox proportional hazards analysis showed that neoadjuvant systemic therapy, lymph nodes involvement and Ki67 levels were prognostic factors in HER2low TNBC but not in HER2neg TNBC patients. ScRNA-seq revealed that HER2low TNBC which showed more metabolically active and aggressive hallmarks, while HER2neg TNBC exhibited signatures more involved in immune activities with higher expressions of immunoglobulin-related genes (IGHG1, IGHG4, IGKC, IGLC2); this was further confirmed by immunofluorescence in clinical TNBC samples. Furthermore, HER2low and HER2neg TNBC exhibited distinct tumor evolutionary characteristics. Moreover, HER2neg TNBC revealed a potentially more active immune microenvironment than HER2low TNBC, as evidenced by positively active regulation of macrophage polarization, abundant CD8+ effector T cells, enriched diversity of T-cell receptors and higher levels of immunotherapy-targeted markers, which contributed to achieve immunotherapeutic response.ConclusionsThis study suggests that HER2low TNBC patients harbor more malignant clinical behavior and aggressive tumor biological properties than the HER2neg phenotype. The heterogeneity of HER2 may be a non-negligible factor in the clinical management of TNBC patients. Our data provide new insights into the development of a more refined classification and tailored therapeutic strategies for TNBC patients.

Background: Triple negative breast cancer (TNBC) is known for its aggressive behavior, poor prognosis and still remains as a difficult disease since treatment options are limited. Despite some success in PARP inhibition in BRCA gene mutation patients or platinating agents that may offer superior outcomes in a subset of TNBC patients (pts), currently, there are no targeted therapies for TNBC available. Specific biomarkers are urgently needed for developing effective treatments to predict which patients will respond to the given therapy. In this regard, circulating tumor cells (CTCs) are discussed to be an ideal surrogate marker for individualized treatment options. Since TNBC is closely related to epithelial-mesenchymal transition (EMT), a stem cell phenotype and, in addition, androgen receptor (AR) expression has been detected in up to a third of TNBC pts, we here established a multi-marker gene panel for the characterization of CTCs in TNBC pts and compared these findings with CTC characteristics in non-TNBC pts. Methods: 2x5 ml blood of 30 TNBC pts before and/or after neoadjuvant therapy and 30 non- TNBC pts (E+/PR+: n=23; ER+/PR-: n=4; HER2+: n=1; HER2+/ER+: n=1; HER2+/ER+/PR+: n=1) before therapy were analyzed for CTCs applying positive immunomagnetic selection targeting EpCAM, EGFR and HER2 using the AdnaTest EMT-2/Stem Cell Select (QIAGEN Hannover GmbH, Germany). Subsequently, cDNA was gene specifically pre-amplified using TaqMan PreAmp Master Mix according to in house designed assays. Establishment of a 19 gene qPCR panel was performed for the markers PI3K, AKT2, ERCC1, Aurka, HER2, HER3, EGFR, ALK, AR (androgene receptor), BRCA1, c-KIT, c-MET, KRT5, mTOR, NOTCH1, PARP1, SRC1, CD45 (leucocyte control) and GAPDH (housekeeping gene) as well as an internal reference. The cutoff was calculated, taken the false positive rate in healthy donors into account and defined as Ct(cutoff)-Ct(sample)-[Ct(CD45cutoff)-Ct(CD45sample)]. Results: In general, the distribution of the markers across all patients was highly variable. However, different expression patterns were found when CTCs of TNBC pts were compared with those of non-TNBC pts. In TNBC pts, SRC1 was the gene that was predominantly expressed, followed by c-Kit, HER3, BRCA1 and AURKA expression, before as well as after therapy. Interestingly, AKT2, EGFR, ERCC1 and PARP1 expression could not be detected at any time point studied. In addition, ALK, AR, c-Met, HER2 and KRT5 were only detected before but not after therapy. All other genes were expressed below 15%. In contrast, in non-TNBC pts, AKT2 was the gene that was predominantly expressed, followed by c-MET, HER3 and PI3K whereas c-KIT, ERCC1, mTOR and NOTCH1 were never found. All other genes were expressed below 10%. Conclusion: We successfully established a gene panel for the detection of the heterogeneous CTC population and demonstrated that CTCs in TNBC pts and non-TNBC pts show different genetic profiles. Although these data have to be confirmed in a bigger patient cohort, the knowledge about the individual target gene expression profile might efficiently help to predict a personalized targeted therapy for these pts in the future. Citation Format: Bittner A-K, Hoffmann O, Hauch S, Kimmig R, Kasimir-Bauer S. Circulating tumor cells in triple-negative and non-triple negative breast cancer patients show different genetic profiles. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-02-05.

Nutrient deprivation is one of the hallmark conditions of a rapidly growing tumor. Rapid proliferation of tumor cells leads to increased consumption of metabolites such as glucose and glutamine resulting in metabolic stress. However, phenotypic and functional status of tumor cells under these conditions is not clear. We hypothesize that nutrient deprivation-induced metabolic stress results in a breast cancer stem cell-like (BCSC) phenotype in triple negative breast cancer (TNBC). We found that serum-deprived conditions result in significant upregulation of GD2+ cells compared to serum rich conditions: from 9%±2% to 26%±5% in MDA-MB-231 and 7%±2% to 29%±5% in SUM159 cells. Interestingly, this affect was compensated when the cells were supplemented with serum-rich medium. In addition, a positive correlation was observed between GD2+ cell number and tumor volume in vivo, suggesting metabolic stress in the growing tumors results in GD2+ phenotype in TNBC cells. Next, TNBC cells cultured under glucose deprivation or in the presence of glycolysis inhibitor, 2-deoxy glucose (2DG) showed a 2-fold increase in GD2+ cells compared to cells cultured with glucose (6g/L) or without 2DG, suggesting that glucose deprivation enhances GD2 expression. Nutrient deprived conditions also showed a significant increase in the expression of stress markers ATF4 and SESN2 demonstrating TNBC cells under metabolic stress. In addition, the above conditions also showed a 2.5-fold upregulation of the mammosphere formation in TNBC cells compared to nutrient rich conditions. Global metabolomics profiling identified glutathione biosynthesis to be most highly upregulated in GD2+ cells. Furthermore, we found that supplementation of glutamine (precursor for glutathione biosynthesis) increases the percentage of GD2+ cells. Carbon and nitrogen tracing using 13C- and 15N-labeled glutamine by mass spectrometry showed its direct contribution to GD2 biosynthesis. Treatment with glutamine transporter (ASCT2) inhibitor V9302 reduced GD2+ cell number by 70%-80% in TNBC cell lines and dramatically inhibited mammosphere and soft agar colony formation, and migration of TNBC cell lines. Mechanistic studies revealed that V9302 inhibits glutathione pathway and induces ROS levels in TNBC cells. Additionally, V9302 treatment inhibited AKT-ERK-mTOR-4E-BP1 pathway and combination of V9302 with paclitaxel synergizes TNBC cell killing. We also identified that, V9302 treatment induced ferroptosis (iron-dependent cell death) in TNBC cells. Finally, V9302 treatment significantly inhibited tumor growth (p&amp;lt;0.0001) in TNBC-PDX model. In conclusion, metabolic stress results in GD2+ BCSC phenotype in TNBC cells and glutamine directly contributes to GD2 biosynthesis. Targeting ASCT2 could complement conventional chemotherapy in TNBC. Citation Format: Appalaraju Jaggupilli, Stanley Ly, Khoa Nguyen, Roshan Borkar, Bin Yuan, Danthasinghe Waduge Piyarathna, Yuanqing Yan, Helen Piwnica-Worms, Henry Charles Manning, Michael Andreeff, Nagireddy Putluri, Lokesh Battula. Targeting glutamine transporter (ASCT2) inhibits metabolic stress-induced GD2+ cancer stem cell-like phenotype in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2322.

Here, we investigated the possible predictive value of stromal caveolin-1 (Cav-1) as a candidate biomarker for clinical outcome in triple negative (TN) breast cancer patients. A cohort of 85 TN breast cancer patients was available, with the necessary annotation and nearly 12 years of follow-up data. Our primary outcome of interest in this study was overall survival. Interestingly, TN patients with high-levels of stromal Cav-1, had a good clinical outcome, with >50% of the patients remaining alive during the follow-up period. In contrast, the median survival for TN patients with moderate stromal Cav-1 staining was 33.5 months. Similarly, the median survival for TN patients with absent stromal Cav-1 staining was 25.7 months. A comparison of 5-year survival rates yields a similar pattern. TN patients with high stromal Cav-1 had a good 5-year survival rate, with 75.5% of the patients remaining alive. In contrast, TN patients with moderate or absent stromal Cav-1 levels had progressively worse 5-year survival rates, with 40% and 9.4% of the patients remaining alive. In contrast, in a parallel analysis, the levels of tumor epithelial Cav-1 had no prognostic significance. As such, the prognostic value of Cav-1 immunostaining in TN breast cancer patients is compartment-specific, and selective for an absence of Cav-1 staining in the stromal fibroblast compartment. A recursive-partitioning algorithm was used to assess which factors are most predictive of overall survival in TN breast cancer patients. In this analysis, we included tumor size, histologic grade, whether the patient received surgery, radiotherapy or chemotherapy, CK5/6, EGFR, p53 and Ki67 status, as well as the stromal Cav-1 score. This analysis indicated that stromal Cav-1 expression was the most important prognostic factor for overall survival in TN breast cancer. Virtually identical results were obtained with CK5/6 (+) and/or EGFR (+) TN breast cancer cases, demonstrating that a loss of stromal Cav-1 is also a strong prognostic factor for basal-like breast cancers. Our current findings may have important implications for the close monitoring and treatment stratification of TN and basal-like breast cancer patients.

Introduction: Population-based incidence rates of triple negative breast cancer (TNBC) are higher for African American (AA) compared to White American (WA) women, but it is unclear whether TNBC risk is genetically associated with African ancestry because AA women represent an ancestrally admixed population. Higher frequencies of TNBC have also been observed in sub-Saharan African breast cancer (BC) patients, but comparative analyses of biomarker expression among datasets that include AA, WA, and African women are sparse. We report findings from an international registry that features specimens from a diverse patient population in Detroit, Michigan as well as a hospital in Kumasi, Ghana. Methods: The study dataset included formalin-fixed, paraffin-embedded invasive BC tumors diagnosed between 1998 and 2014 at the Komfo Anokye Teaching Hospital in Ghana and the prospectively-maintained/annotated Henry Ford Health System cohort in Michigan. All Ghanaian tumors underwent pathology confirmation and immunohistochemistry for estrogen receptor (ER), progesterone receptor (PR) and HER2/neu expression at the University of Michigan. Women were classified into five BC phenotypes and dichotomized into two age groups, &amp;lt;50 and ≥50 years. Polychotomous multivariate GLM models were developed to estimate the risk for each BC phenotype. Statistical analyses were performed in SAS v. 9.0 (Carey, NC). This research was approved by the Institutional Review Boards of the participating institutions. Results: A total of 234 Ghanaian cases with mean age 49 years (range 24-92); 271 AA with mean age 60 (range 27-87); and 321 WA with mean age 62 (range 31-91) (P=0.001) contributed to this study. Prevalence of histologic grade 3 was lowest in WA (n=107, 33.7%) which was statistically significant from the observed prevalence in AA (n=135, 50.4%) and Ghanaians (n=84, 53.8%) (P&amp;lt;0.0001). ER-negative and TNBC were more common among Ghanaian and AA compared to WA cases (frequency ER-negativity 67.5%, 37.1%, and 19.8%, respectively, p&amp;lt;0.0001; frequency TNBC 53.2%, 29.8%, and 15.5%, respectively, p&amp;lt;0.0001). In the age group &amp;lt;50 years, 82 women (42.5%) were diagnosed with ER+/PR+/HER2-, 65 (33.7%) with TNBC, 27 (14.0%) with ER+/PR+/HER2+, 14 (7.2%) with ER-/PR-/HER2+ and 5(2.6%) with ER-/PR+/HER2- phenotypes. In this young age group, prevalence of TNBC remained highest among Ghanaian women (50.8%), followed by AA (34.3%) and WA (15.9%); (P=.0006). In contrast, highest prevalence of ER+/PR+/HER2+ and ER+/PR+/HER2- phenotypes was observed in WA, followed by AA and Ghanaians. On multivariate analysis histologic grade 3 and racial heritage remained statistically significantly associated with the TNBC phenotype (OR for AA vs. WA with TNBC 1.87, 95% CI 1.15-3.04; OR for Ghanaian vs. WA with TNBC 10.63, 95% CI 5.32-21.25; OR for Grade 3 vs Grade 1 histology with TNBC 33.3, 95% CI 13.45-82.4). Conclusions: This study confirms an association between the TNBC phenotype and African ancestry; furthermore, extent of African ancestry appears to be associated with an increased likelihood of having a TNBC tumor, since frequency of TNBC among AA patients was intermediate between WA and Ghanaian patients. Citation Format: Newman LA, Jiagge E, Bensenhaver JM, Chitale D, Kleer C, Merajver S, Kyei I, Aitpillah F, Oppong J, Amankwaa-Frempong E, Adjei E, Wicha M, Awuah B, Stark A. Comparative analysis of breast cancer phenotypes in African American, White American, and African patients- Correlation between African ancestry and triple negative breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-12-14.

c-Jun N-terminal kinase (JNK) plays a vital role in malignant transformation of different cancers, and JNK is highly activated in basal-like triple-negative breast cancer (TNBC). However, the roles of JNK in regulating cancer stem-like cell (CSC) phenotype and tumorigenesis in TNBC are not well defined. JNK is known to mediate many cellular events via activating c-Jun. Here, we found that JNK regulated c-Jun activation in TNBC cells and that JNK activation correlated with c-Jun activation in TNBC tumors. Furthermore, the expression level of c-Jun was significantly higher in TNBC tumors than in non-TNBC tumors, and high c-Jun mRNA level was associated with shorter disease-free survival of patients with TNBC. Thus, we hypothesized that the JNK/c-Jun signaling pathway contributes to TNBC tumorigenesis. We found that knockdown of JNK1 or JNK2 or treatment with JNK-IN-8, an adenosine triphosphate-competitive irreversible pan-JNK inhibitor, significantly reduced cell proliferation, the ALDH1+ and CD44+/CD24- CSC subpopulations, and mammosphere formation, indicating that JNK promotes CSC self-renewal and maintenance in TNBC. We further demonstrated that both JNK1 and JNK2 regulated Notch1 transcription via activation of c-Jun and that the JNK/c-Jun signaling pathway promoted CSC phenotype through Notch1 signaling in TNBC. In a TNBC xenograft mouse model, JNK-IN-8 significantly suppressed tumor growth in a dose-dependent manner by inhibiting acquisition of the CSC phenotype. Taken together, our data demonstrate that JNK regulates TNBC tumorigenesis by promoting CSC phenotype through Notch1 signaling via activation of c-Jun and indicate that JNK/c-Jun/Notch1 signaling is a potential therapeutic target for TNBC.

Introduction: Triple-negative breast cancer (TNBC), an aggressive form of breast cancer (BC) that is associated with poor prognosis, accounts for 10-15% of all BCs. Chemotherapy remains the standard of care (SOC) for advanced disease, with limited clinical benefit. Oncology clinical trials (CTs) are globally recommended and encouraged as the preferred treatment (tx) option for any cancer patient (pt). ‘TrialJectory’ (TJ) is an artificial intelligence (AI)-based technology that matches pts to oncology CTs. Here, we identified distinct characteristics of TNBC pts who signed up to the TJ platform compared to non-TNBC pts. Methods: Using AI and an unsupervised natural language processing approach, the TJ platform clinically matches pts to CTs. Matching is achieved by pt response to an online dynamic questionnaire (www.trialjectory.com) that collects detailed clinical data including clinico-pathologic characteristics, tx history, general health, and comorbidities. Those are compared to the eligibility criteria of available CTs to yield a high-quality actionable matched-trial list. Results: Between 1/2020 and 12/2021, out of 9796 BC pts that signed up, 2688 were TNBC pts (27%). There was no significant difference in age at sign-up between TNBC and non-TNBC patients (median age of 57 years vs 58 years, respectively). Consistently with Non-hispanic black (NHB) race prevalence in the different molecular subtypes in the general US population, NHB race had higher signup rate in TNBC compared to non-TNBC (9.95% vs 5.76%, respectively). TNBC pts signed up at a later disease stage compared to non-TNBC pts (19% of TNBC reported having a stage 1 disease compared to 27% of non-TNBC pts, p&amp;lt; 0.001).A significantly higher percentage of pts with advanced/metastatic TNBC signed up to the TJ platform before starting tx compared to non-TNBC patients (34% vs 22%, respectively, p&amp;lt; 0.001). Furthermore, there was a significant difference in the willingness to travel any distance within the US for a matched clinical trial between TNBC and non-TNBC pts (39% vs 34%, respectively, p&amp;lt; 0.001). Conclusions: In this study, we found significant differences in the characteristics of TNBC vs non-TNBC pts that have signed up to the TJ platform. There was an up to 2-fold enrichment of TNBC on the TJ platform pts compared to their frequency in the general population. While previous studies do not show a difference in stage distribution between different subtypes, TNBC patients initiated their search for CTs at a higher stage. In addition, advanced TNBC patients started their search earlier in their journey, before starting chemotherapy. This may reflect the lack of effective SOC and possibly, the motivation to avoid the use of chemotherapy. This is also supported by the willingness of TNBC patients to travel farther in order to identify and enroll in a CT compared to non-TNBC pts. Importantly, the motivation of TNBC pts to travel any distance has not been reduced despite the COVID-19 pandemic, reflecting a strong drive of this pt population to enroll in CTs. It also demonstrates that with the right access, diverse patient populations are willing to participate in clinical trials. In sum, TNBC pts are more likely to explore CT options, in the advanced stage setting, earlier in their journey. This study demonstrates the power of TJ platform for clinico-pathologic characterization and diverse pt groups, including their drivers and behavioral choices during their battle with cancer. Citation Format: Michal Safran, Yelena Lapidot, Tzvia Bader, Avital Gaziel. Triple Negative Breast Cancer (TNBC) patients are more likely to digitally explore clinical trial options and prior to receiving treatment for advanced disease compared to non-TNBC patients [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-13-05.

BackgroundMetaplastic breast cancer remains poorly characterized given its rarity and heterogeneity. The majority of metaplastic breast cancers demonstrate a phenotype of triple-negative breast cancer; however, differences in clinical outcomes between metaplastic breast cancer and triple-negative breast cancer in the era of third-generation chemotherapy remain unclear.MethodsWe compared the clinical outcomes between women with metaplastic breast cancer and women with triple-negative breast cancer diagnosed between 1994 and 2014. Metaplastic breast cancer patients were matched 1:3 to triple-negative breast cancer patients by stage and age at diagnosis. Distant disease-free survival (DDFS) and overall survival (OS) were estimated using Kaplan Meier methods and Cox proportional hazard regression models. Immune checkpoint markers were characterized by immunohistochemistry in a subset of samples.ResultsForty-four metaplastic breast cancer patients (stage I 14%; stage II 73%; stage III 11%; stage IV 2%) with an average age of 55.4 (± 13.9) years at diagnosis. Median follow-up for the included metaplastic breast cancer and triple-negative breast cancer patients (n = 174) was 2.8 (0.1–19.0) years. The DDFS and OS between matched metaplastic breast cancer and triple-negative breast cancer patients were similar, even when adjusting for clinical covariates (DDFS: HR = 1.64, p = 0.22; OS: HR = 1.64, p = 0.26). Metaplastic breast cancer samples (n = 27) demonstrated greater amount of CD163 in the stroma (p = 0.05) and PD-L1 in the tumor (p = 0.01) than triple-negative breast cancer samples (n = 119), although more triple-negative breast cancer samples were positive for CD8 in the tumor than metaplastic breast cancer samples (p = 0.02).ConclusionsPatients with metaplastic breast cancer had similar outcomes to those with triple-negative breast cancer based on DDFS and OS. The immune checkpoint marker profile of metaplastic breast cancers in this study may prove useful in future studies attempting to demonstrate an association between immune profile and survival.

Purpose: Based on clinical and molecular data, breast cancer is a heterogeneous disease. Breast cancers that have no expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) are defined as triple negative breast cancers (TNBCs); luminal cancers have different expressions of ER, PR and/or HER2. TNBCs are frequently linked with advanced disease, poor prognosis and occurrence in young African women, and about 15% of the cases are associated with germline BRCA1/2 mutations. Since radiotherapy is utilized as a principle treatment in the management of TNBC, we aimed to investigate the chromosomal instability and radiosensitivity of lymphocytes in TNBC patients compared to luminal breast cancer patients and healthy controls using the micronucleus (MN) assay. The effect of mutations in breast cancer susceptibility genes on chromosomal radiosensitivity was also evaluated.Methods: Chromosomal radiosensitivity was evaluated in the G0 (83 patients and 90 controls) and S/G2 (34 patients and 17 controls) phase of the cell cycle by exposing blood samples from all patients and controls to 2 and 4 Gy ionizing radiation (IR).Results: In the G0 MN assay, the combined cohort of all breast cancer, TNBC and luminal patients’ exhibit significantly elevated spontaneous MN values compared to controls indicating chromosomal instability. Chromosomal radiosensitivity is also significantly elevated in the combined cohort of all breast cancer patients compared to controls. The TNBC patients, however, do not exhibit enhanced chromosomal radiosensitivity. Similarly, in the S/G2 phase, 76% of TNBC patients do not show enhanced chromosomal radiosensitivity compared to the controls. In both the G0 and S/G2 phase, luminal breast cancer patients demonstrate a shift toward chromosomal radiosensitivity compared to TNBC patients and controls.Conclusions: The observations of the MN assay suggest increased chromosomal instability and chromosomal radiosensitivity in South African breast cancer patients. However, in TNBC patients, the irradiated MN values are not elevated. Our results suggest that the healthy lymphocytes in TNBC patients could handle higher doses of IR.

The aim of the present study was to investigate the expression of estrogen receptor β (ERβ) in triple-negative and triple-positive breast cancer patients, and evaluate its utility as a prognostic factor. Between January 2000 and December 2010, primary tumor tissue samples were collected from 234 subjects, including 107 triple-negative and 127 triple-positive breast cancer patients. The samples were embedded in paraffin and immunohistochemical staining was conducted to determine the expression levels of ERβ. The Kaplan-Meier method was used to analyze patient survival rates. ERβ expression was observed in 38/107 patients (35.5%) with triple-negative breast cancer and 63/127 patients (49.6%) with triple-positive breast cancer. The ERβ expression rate was significantly decreased in the patients with triple-negative breast cancer, as compared with those with triple-positive breast cancer (P=0.03). Analysis of the survival rates indicated that patients with triple-negative breast cancer and positive ERβ expression exhibited poor disease progression-free survival (DFS) compared with those with negative ERβ expression (P=0.021). However, no statistically significant difference was observed in the DFS between the triple-positive breast cancer patients with positive and negative ERβ expression. Therefore, the expression of ERβ varies between triple-negative and triple-positive breast cancer patients. In addition, positive expression of ERβ indicates a poor prognosis in triple-negative breast cancer patients; however, this is not the case for triple-positive breast cancer patients.