Never in mitosis gene A-related kinase-8 promotes proliferation, migration, invasion, and stemness of breast cancer cells via β-catenin signalling activation

Never in mitosis gene A (NIMA)-related kinase-8 (NEK8) is involved in cell cycle progression, cytoskeleton development, and DNA damage repair. However, its role in breast cancer has not yet been explored. To investigate this, NEK8 was knocked down in MDA-MB-231, BT549, and HCC38 breast cancer cell lines. We observed a decrease in cell proliferation and colony formation owing to regulation of the G1/S and G2/M transitions. Furthermore, the expression of several cell cycle regulatory proteins was altered, including that of cyclin D1, cyclin B1, CDK4, CDK2, and surviving. NEK8 knockdown impaired cell migration and invasion as well as reduced the expression of epithelial-mesenchymal transition markers. Regarding stem-cell characteristics, NEK8 knockdown decreased the tumour sphere formation, aldehyde dehydrogenase activity, and stem-cell marker expression, including that of CD44, Sox2, Oct4a, and Nanog. Further analysis revealed that NEK8 interacts with β-catenin. Also, NEK8 knockdown promoted β-catenin degradation. NEK8-silenced MDA-MB-231 cells inhibited xenograft tumour growth, metastasis, and tumour initiation in vivo. Using the Oncomine and TNMplot public databases, we found a significant correlation between NEK8 overexpression and poor clinical outcomes in breast cancer patients. Thus, NEK8 may be a crucial regulator of breast cancer progression and a potential therapeutic target.

Triple-negative breast cancer-derived extracellular vesicles promote a hepatic pre-metastatic niche via a cascade of microenvironment remodeling

Triple negative breast cancer (TNBC) patients often develop metastases in visceral organs including the liver but the detailed molecular mechanisms of TNBC liver metastasis is not clearly understood. In this study, we tried to dissect the process of pre-metastatic niche formation in liver by using patient-derived xenograft (PDX) models of TNBC with different metastatic propensity. RNA sequencing of TNBC PDX models that successfully metastasized to liver showed up-regulation of Cx3cr1 gene in the liver microenvironment. In syngeneic breast cancer models, the Cx3cr1 up-regulation in liver preceded the development of cancer cell metastasis and was the results of recruitment of CX3CR1-expressing macrophages. The recruitment was induced by the CX3CL1 production from the liver endothelial cells and this CX3CL1-CX3CR1 signaling in the pre-metastatic niche resulted in up-regulation of MMP9 that promoted macrophage migration and cancer cell invasion. Additionally, our data suggest that the extra-cellular vesicles derived from the breast cancer cells induced the TNF-alpha expression in liver which leads to the CX3CL1 up-regulation. Lastly, the plasma CX3CL1 levels in 155 breast cancer patients were significantly associated with development of liver metastasis. Implications: Our data provides previously unknown cascades regarding the molecular education of pre-metastatic niche in liver for TNBC.

Abstract 6654: Association PD-L1 overexpression with immune checkpoint inhibitor effect in triple-negative breast cancer

Background: Recently, studies on the antitumor effects of PD-L1 inhibitors have gained importance in difficult to treat solid tumors. In particular, the expression of PD-L1 could be an important factor in evaluating the possibility of immunotherapy in triple-negative breast cancer where targeted therapy is not possible and the prognosis is poor. Accordingly, this study investigated the effect of PD-L1 overexpression on the immune checkpoint inhibitor effect in triple-negative breast cancer.

Method: The relationship between T stage and N stage according to PD-L1 mRNA expression was analyzed in the TCGA and METABRIC datasets of breast cancer. To evaluate the role of PD-L1, PD-L1-overexpressing breast cancer cell lines for in vitro and in vivo experiments were established.

Result: Using TCGA and METABRIC datasets, we found that PD-L1 showed the highest expression in breast cancer of the basal subtype, but the correlation between T stage and N stage according to PD-L1 expression was not statistically significant. To determine the functional importance of PD-L1 in breast cancer, we established 4T1-PD-L1-overexpressing breast cancer cell lines. We observed that the overexpression of PD-L1 promoted cell proliferation, migration, and invasion. In the orthotopic tumor mouse model, PD-L1 showed no significant difference in tumor growth compared to the control group, but anti-PD-L1 treatment showed a significant antitumor effect.

Conclusion: We confirmed that overexpression of PD-L1 in an orthotopic breast cancer model did not induce increased tumor growth. Above all, it was confirmed that a high PD-L1 level enhances the antitumor effect of immune checkpoint inhibitors. Our findings show that the expression level of PD-L1 in breast cancer has a significant effect on the immune checkpoint inhibitor effect. We need to further investigate the role of PD-L1 in breast cancer.

Citation Format: A Young Park, Ju Hee Kim, Sangen Lee, Hong Kyu Kim, Han-Byoel Lee, Wonshick Han. Association PD-L1 overexpression with immune checkpoint inhibitor effect in triple-negative breast cancer [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 6654.

Abstract P3-04-11: Longitudinal Changes of Contralateral Breast Mammographic Artificial Intelligence Algorithms Score in Ductal Carcinoma In Situ patient with Tamoxifen

Background Mammographic Artificial intelligence (AI) algorithms (Lunit insight MMG) draws attention as a diagnostic support tool for breast cancer detection. Lunit insight MMG provides a location suspected of breast cancer with a heatmap and a score reflecting the probability of the presence of suspicious areas. We investigated whether the Lunit insight MMG score is relevant for predicting the response to adjuvant tamoxifen. Methods Patients diagnosed with DCIS and underwent treatment at Seoul National University Hospital in 2010 were retrospectively enrolled. Clinical characteristics, tamoxifen use, survival data, and mammography images were extracted from the electronic medical records, and Lunit insight MMG scores were calculated retrospectively. We classified two groups according to tamoxifen treatment and compared the score change of contralateral breast from baseline to 5 years after surgery for DCIS. Change categories of Lunit insight MMG score included maintaining high risk, maintaining low risk, increasing from low risk to high risk, and decreasing from high risk to low risk. Results Of 100 patients, 50 (50%) had undergone tamoxifen treatment (group 1) and 50 (50%) had not (group 2). The median age of the patients was 48.4 years for group 1 and 51.5 years for group 2 (p=0.172). The median follow-up duration was 8.7 years for the whole cohort. Using Lunit insight MMG score, more patients in group 1 decreased in contralateral breast cancer (CBC) risk compared with group 2 (6.0% vs. 2.0%; P=.008). No patients in group 1 had an increase in CBC risk while 9 patients increased in group 2 (0% vs. 18.0%; P =.008). There was no ipsilateral breast cancer recurrence for the whole cohort, and two patients experienced contralateral invasive breast cancer in group 2. In two patients with CBC, the Lunit insight MMG score increased five years after surgery, one year and three years before the CBC diagnosis. Conclusions Longitudinal Changes of Mammographic AI algorithms Score may be a predictive surrogate marker for response to tamoxifen therapy in hormone receptor-positive DCIS.

Citation Format: Changjin Lim, Eun Kyung Park, Hong-Kyu Kim, Eunhye Kang, Ji-Jung Jung, Hyunsu Yeoh, Jang-il Kim, Jung Whan Chun, Han-Byoel Lee, Hyeong-Gon Moon, Wonshik Han. Longitudinal Changes of Contralateral Breast Mammographic Artificial Intelligence Algorithms Score in Ductal Carcinoma In Situ patient with Tamoxifen [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 P3-04-11.

Abstract P2-14-15: Comparison of recurrence-free survival according to axillary surgery extent for clinical N0, sentinel node(s) positive, primary breast cancer patients who underwent total mastectomy

Purpose We investigated the recurrence-free survival difference between limited axillary node surgery and axillary node dissection (ALND) in clinical N0 primary breast cancer patients with one to three sentinel node metastasis who underwent total mastectomy. Method We retrospectively analyzed clinical data of 579 primary breast cancer patients who underwent total mastectomy between 2014 and 2018 from Seoul National University Hospital and Asan Medical Center. All included patients had clinical T1-2, N0 disease at the time of diagnosis based on physical exam, radiologic evaluation, and pathologic assessment if needed. The patients had one to three metastatic sentinel node(s) at the time of surgery. The patients received sentinel lymph node biopsy (SLNB) with result of one to three metastatic node(s) and either proceeded to ALND or not. We performed propensity score matching between the SLNB and ALND group with baseline clinical factors including clinical T stage and number of metastatic sentinel node(s). Finally, 208 patients were matched 1:1 for each group respectively for further analysis. Also, we stratified the eligible patients based on radiation therapy for subgroup analysis. We examined disease-free survival, regional recurrence-free survival, distant metastasis-free survival and compared the results between the groups. Result The median follow-up period was 64.7 months. Among matched cohorts, mean number of metastatic nodes on final pathology result was 1.2 for SLNB group and 1.7 for ALND group. Also, mean number of total removed nodes was 8.3 for SLNB group and 17.4 for ALND group. The disease-free survival [DFS] at 7 years was 89.7% for SLNB group and 91.1% for ALND group with no statistically significant difference. (hazard ratio [HR] 1.43, 95% confidence interval [CI] 0.70 to 2.92, p=0.32) Among patients who were treated with radiation, the DFS was 94.1% in the SLNB group and 94.4% in the ALND group. (HR, 0.82, 95% CI 0.17 to 4.0, p=0.81) For the subgroup without radiation, the DFS was 87.7% in the SLNB group and 89.4% in the ALND group. (HR, 1.68, 95% CI 0.75 to 3.75, p=0.19) We observed no statistically significant differences in the regional recurrence-free survival at 7 years (95.8% in the SLNB vs. 95% in the ALND, HR 0.62, 95% CI 0.53-4.95, p=0.39), and in the distant metastasis-free survival at 7 years (95.8% in the SLNB vs. 95% in the ALND, HR 1.28, 95% CI 0.59 to 2.73, p=0.52) Conclusion Our results suggest that limited axillary surgery with sentinel node biopsy may be as effective as axillary node dissection in terms of recurrence-free survival, for clinically node negative, primary breast cancer patients with limited metastatic sentinel node(s) who are candidates for total mastectomy. Key words: Breast cancer, Total mastectomy, Axillary lymph node dissection, Sentinel lymph node biopsy.

Citation Format: Jung Whan Chun, Hong-Kyu Kim, Han-Byoel Lee, Hyeong-Gon Moon, Jong Won Lee, Wonshik Han. Comparison of recurrence-free survival according to axillary surgery extent for clinical N0, sentinel node(s) positive, primary breast cancer patients who underwent total mastectomy. [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 P2-14-15.

Abstract P2-20-05: Personalized tumor vaccine can suppress tumor growth and metastasis in the syngeneic mouse breast cancer model

Objective Immunotherapy using the tumor-specific antigens (TSAs) is a promising strategy in breast cancer. Studies have suggested that the in vivo exposures to certain tumors can induce adaptive anti-tumor immunity in syngeneic tumor models. In this study, we show the efficacy of the tumor lysate vaccine and peptide-based vaccine against tumor neoantigen in suppressing tumor growth and metastasis in 4T1 syngeneic tumor models. Method We used BALB/c mice and its syngeneic tumor cell lines to evaluate the anti-tumor effect induced by the transient exposure to the tumor cells. For tumor vaccines, we synthesized the tumor lysate vaccine by the freeze-thaw method or synthetic peptide against the selected tumor neoantigens identified by exome sequencing. We systemic and local immune remodeling was investigated by using immunohistochemistry, flow cytometry, and single cell RNA sequencing. Results We observed a significant reduction of tumor growth and metastasis in 4T1 syngeneic tumors when the mice were previously exposed to the same cells (pre-exposure group). This anti-tumor effect induced by the exposures to the tumor was cell line-specific. The 4T1 tumor lysate vaccines administered prior to the tumor cell injection also showed significant inhibitory effect on tumor growth and metastasis. T lymphocytes, isolated from the tumor tissues of the 4T1 pre-exposure mice and lysate vaccine-treated mice, showed higher levels of TNF-ɑ and IFN-ɣ when compared to the control those from the control tumors. The lysate vaccine treatment resulted in a substantial remodeling of tumor microenvironment including reduction of myeloid-derived suppressor cells and M2 tumor-associated macrophages. On the other hand, the numbers of M1 tumor-associated macrophages and effector memory CD8+ T cells were increased by the lysate vaccine. While the peptide vaccine showed no inhibitory effect on the primary tumor growth, it also suppressed spontaneous lung metastasis. Finally, we administered lysate tumor vaccine after the tumor establishment to determine the therapeutic effect. The lysate vaccine significantly suppressed the tumor growth and lung metastasis of the syngeneic 4T1 tumors. Conclusion Tumor lysate vaccine can suppress the tumor growth and metastasis in the 4T1 syngeneic mouse models by inducing substantial remodeling of tumor immune microenvironment. Additionally, tumor lysate vaccine can elicit similar anti-tumor immune response when administered after the establishment of the primary tumor suggesting a potential therapeutic value.

Citation Format: Hyeong-Gon Moon, Hye Youn Son, Woo Hang Heo, Mingji Quan, SONGBIN LI, Haritonova Valentina, Hamin Jeong, Wonshik Han, Han-Byoel Lee, YUJEONG HER, Ju Hee Kim. Personalized tumor vaccine can suppress tumor growth and metastasis in the syngeneic mouse breast cancer model [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 P2-20-05.

Abstract P2-26-10: Statins exhibit an anti-tumor effect by attenuating PD-L1 in breast cancer cells and macrophages and reducing breast tumor progression in xenograft mouse model

Background: Statins were suggested for repurposed drugs, having multifaceted effects which include anti-tumor activities by modulating the immune response. Here, we aimed to demonstrate the effect of statins on programmed death-ligand 1 (PD-L1) expression in triple-negative breast cancer (TNBC) cells. Methods: Thirteen human TNBC cell lines, mouse macrophage cell line (RAW 264.7), cholesterol and 27-hydroxycholesterol, and clinically approved lovastatin and simvastatin were used. Flow cytometry, Annexin V/propidium iodide assay, western blot, qRT-PCR, transwell migration assay, and immunohistochemistry were employed. A co-culture of macrophages with various breast cancer cells was performed. An orthotopic breast tumor mouse model and metastasis model by injection of GFP-tagged MDA-MB-231 cells into mammary gland fat pad and the tail vein injection were produced. In tumor model mice, lovastatin(10mg/kg) was daily injected intraperitoneally. In vivo fluorescent imaging was used to identify primary tumor development and lung metastasis. Results: Among thirteen TNBC cell lines, MDA-MB-231, HCC38, and HCC70 highly expressed endogenous/constitutive PD-L1. Statins reduced PD-L1 expression and exerted anti-proliferative and apoptotic effects in MDA-MB-231, HCC38, HCC70, and Raw264.7 in a dose- and time-dependent manner (p< 0.05). Meanwhile, statins increased the expression of PD-L1 in Hs578T and MDA-MB-468. STAT3 phosphorylation was inhibited in MDA-MB-231 and HCC70, but not in Hs578T, while AKT phosphorylation was reduced in MDA-MB-231, HCC70, Hs578T, and MDA-MB-468 when statins were treated. The migration of MDA-MB-231 and Raw264.7 in statin-treated conditioned media was decreased (p< 0.05). Cholesterol and 27-hydroxy cholesterol did not restore PD-L1 expression in statin-treated MDA-MB-231. Statins suppressed the expression of M2 markers (PD-L1, CD206, YM-1, Fizz1, arginase-1) in RAW26437 stimulated by a conditioned medium of MDA-MB-231. Lovastatin suppressed the primary tumor growth and metastasis in xenograft tumor mice. Conclusions: Our findings show that statins have an anti-tumor effect, which kills breast cancer cells and triggers macrophage reprogramming by reducing PD-L1 expression, impairing the AKT, ERK, and STAT3 signal pathways, and decreasing M2 markers. Further study is needed to investigate an in-depth molecular mechanism study by which statins regulate PD-L1 expression in TNBC and to confirm the safe and effective use of statins as adjuvant therapy in TNBC.

Citation Format: Sangeun Lee, Hoe Suk Kim, So-Hyun Yoon, Seungyeon Ryu, Moonjou Baek, A Young Park, Han-Byoel Lee, Wonshik Han. Statins exhibit an anti-tumor effect by attenuating PD-L1 in breast cancer cells and macrophages and reducing breast tumor progression in xenograft mouse model [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 P2-26-10.

Abstract P5-01-04: Contralateral Axillary Lymph Node Metastasis after Ipsilateral Breast Tumor Recurrence: Is it distant metastasis or locoregional progression?

Background: Contralateral axillary lymph node metastasis (CAM) in breast cancer is currently classified as a stage IV disease but its prognosis is still controversial. Purpose: To determine outcomes in overall survival (OS) and disease-free survival (DFS) in patients with and without locoregional tumor recurrence who present with contralateral axillary lymph node metastasis (CAM). Methods: Patients with pathologically confirmed invasive breast cancer with metachronous CAM who received treatment between 1988 and 2017 were retrospectively reviewed. Patients with other distant metastases at the time of CAM diagnosis were excluded. The outcome of CAM in cases of IBTR and regional recurrence (RR) were compared to CAM not accompanied by locoregional tumor recurrence. Results: Thirty-eight patients with metachronous CAM were included in the study. Metachronous CAM occurred 55 months (interquartile range, 17-77 months) after surgical treatment of the primary tumor and median follow-up was 95 months (interquartile range, 49-117 months) from the initial operation date and 40 months (interquartile range, 15-54 months) from the diagnosis of CAM. At the time of initial CAM diagnosis, 11 patients had IBTR, 12 patients had RR, and 15 patients had no locoregional recurrence. The estimated 5-year OS was 49.1% and 5-year DFS was 45.3%. Although statistically insignificant due to small sample size, when stratified by loco regional recurrence, the prognosis of CAM patients with IBTR appeared to be better than those without locoregional recurrence (5-year OS: 88.9% vs. 41.4%, HR 5.88, p = 0.09) whereas the prognosis of CAM patients with RR was worse than those without locoregional recurrence (5-year OS: 35.4% vs. 41.4%, HR 0.44, p = 0.20). Axillary lymph node dissection (ALND) improved median OS (83 vs. 36 months, p = 0.069) in all patients. When stratified, improvement in median OS was 13 vs 27 months (p = 0.094) in patients with RR, and 36 vs. 65 months (p = 0.061) in patients without locoregional recurrence. For patients accompanied by IBTR, ALND was performed in 8 out of 11 and only one patient died during the follow-up period. Conclusion: Our study indicates that the patients with CAM have superior survival outcome when compared to other stage IV patients, especially when CAM was accompanied by other loco regional recurrences. These data suggest that the CAM patients may benefit from active loco regional treatment.

Citation Format: Ji-Jung Jung, Hyeong-Gon Moon, Wonshik Han, Han-Byoel Lee, Hong-Kyu Kim, Jung Whan Chun, Eunhye Kang, Changjin Lim, Jang-il Kim, Hyunsu Yeoh. Contralateral Axillary Lymph Node Metastasis after Ipsilateral Breast Tumor Recurrence: Is it distant metastasis or locoregional progression? [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 P5-01-04.

Abstract P3-05-36: Prognostic factors in non-metastatic hormone receptor-positive HER2-negative mucinous breast cancer: an international multicentre cohort study

Background: Mucinous carcinoma is the third most common histological subtype of breast cancer after ductal and lobular carcinomas, accounting for approximately 3% of invasive breast cancers. Although considered a favourable subtype with de-escalation of treatment recommended in the National Comprehensive Cancer Network guidelines, recurrence can occur and supporting data is limited. We thus examined prognostic factors of pure mucinous breast cancer (PMBC) in an international multicentre cohort study. Methods: Patients diagnosed between January 2000 to December 2015 with hormone receptor-positive HER2-negative stage I to III PMBC, invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) at 6 centers in Singapore, Taiwan, Korea and Japan were evaluated. Cox proportional hazards regression analyses were used to compare relapse-free survival (RFS), distant relapse-free survival (DRFS) and overall survival (OS) by histological subtypes, and to identify prognostic factors for PMBC. Results: Of 23,105 women eligible for analysis, 20,684 had IDC, 1,475 had ILC and 946 had PMBC. The median follow-up was 6.6 years; 5-year RFS, DRFS and OS for PMBC were 94.6%, 96.5% and 98.1% respectively. On multivariable cox regression analyses, PMBC demonstrated superior RFS (hazard ratio [HR] = 0.70, 95% CI: 0.56 - 0.88), DRFS (HR = 0.69, 95% CI: 0.53 - 0.89) and OS (HR = 0.70, 95% CI: 0.52 - 0.93) compared to IDC, while ILC had comparable survival outcomes as IDC. When restricted to only PMBC, significant independent prognostic factors for RFS included ethnicity (vs Chinese, “Others” [non-Chinese/Japanese/Korean, mainly Malay and Indian]: HR = 2.62, 95% CI 1.23 – 5.57), older age (vs < 40 years, >70 years: HR = 3.53, 95% CI 1.67 – 7.46), tumor size (vs T1, T3-4: HR = 2.79, 95% CI 1.45 – 5.37), positive lymph nodes (HR = 2.04, 95% CI: 1.10 – 3.77), use of radiotherapy (HR = 0.54, 95% CI 0.33 – 0.91) and endocrine therapy (HR = 0.31, 95% CI 0.12 – 0.77). On further analysis, the inferior RFS, DRFS and OS in older patients (>70 years) were driven largely by non-breast cancer deaths rather than relapses. Use of endocrine therapy was also associated with superior DRFS (HR = 0.26, 95% CI 0.09 – 0.73) but not OS. In a subgroup analysis, use of chemotherapy was associated with improved DRFS (HR = 0.25, 95% CI 0.08 – 0.82) and OS (HR = 0.07, 95% CI 0.01 – 0.37) with a trend in RFS (HR = 0.41, 95% CI 0.14 – 1.24) for lymph node-positive PMBC; no differences in outcomes were observed for the lymph node-negative subgroup. Conclusions: Larger tumor size, lymph node positivity and ethnicity were significant factors for RFS in PMBC. Use of endocrine therapy was associated with superior RFS and DRFS, while chemotherapy was associated with better DRFS and OS for lymph-node positive PMBC.

Citation Format: Ryan Tan, Whee Sze Ong, Kyung-Hun Lee, Seri Park, Jabed Iqbal, Yeon Hee Park, Jeong-Eon Lee, Jong Han Yu, Ching-Hung Lin, Yen-Shen Lu, Makiko Ono, Takayuki Ueno, Yoichi Naito, Tatsuya Onishi, Geok hoon Lim, Su-Ming Tan, Han-Byoel Lee, Jiwon Koh, Han Suk Ryu, Wonshik Han, Veronique Kiak Mien Tan, Fuh-Yong Wong, Seock-Ah Im, Puay Hoon Tan, Yoon-Sim Yap. Prognostic factors in non-metastatic hormone receptor-positive HER2-negative mucinous breast cancer: an international multicentre cohort study [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 P3-05-36.

Abstract P6-02-14: Contralateral breast cancer risk in patients with or without BRCA mutation

Background: Patients who carry mutated BRCA1 or BRCA2 genes have a significantly increased risk of breast cancer and developing contralateral breast cancer (CBC). In this study, we aimed to investigate the acceptance rate of BRCA1/2 testing in Korean breast cancer patients and to determine the risk of CBC in Korean patients with BRCA 1/2 germline mutations. Methods: This study included 13,109 patients with first primary breast cancer who were treated at Seoul National University Hospital from January 2005 to December 2018. These patients were divided into high-risk for BRCA1/2 mutation group and low-risk group. High risk patients were defined as those who were eligible for BRCA testing per Korean National Health Insurance Service. The high-risk group was further classified into three groups; BRCA1/2 mutation carrier, BRCA 1/2 non carrier and BRCA/12 untested. Results: Among the 4,446 high-risk patients, 962 (21.7%) patients underwent BRCA1/2 testing. The testing rate varied among different indications (47.8% of patients with a family history, 23.3% of patients under 40 years of age, and 13.0% of patients with triple negative breast cancer). The risk of the CBC in BRCA mutation group was higher than other groups (p value < 0.001). The 10-year cumulative risk of CBC was 11.0% BRCA1 mutation carrier and 7.4% for BRCA2 mutation carrier. In the BRCA1/2 non-carriers, the cumulative risk of CBC was 5.7%. Interestingly, the CBC risk for BRCA1/2 non-carriers significantly higher than BRCA1/2 untested group and the low-risk group (p < 0.001). When compared to the BRCA1/2 untested group, the relative risk for CBC was 6.7-fold increase for the BRCA1/2 mutation carrier group (95% CI = 3.65-12.22, p < 0.001), and 2.3-fold increase for the BRCA1/2 non-carriers group (95% CI = 1.44-3.83, p < 0.001). The relative risk for CBC in high-risk group also depended on subtype of breast cancer and family history. Hormone receptor negative breast cancer patients had a 1.5-fold (95% CI = 1.02-2.31, p = 0.04) increased risk of CBC and patients with one or more 1st degree relative with breast cancer had 2.4-fold increased risk (95% CI = 1.55-3.67, p < 0.001). Conclusion: About one out of five Korean breast cancer patients, who are eligible for the BRCA1/2 testing, undergo testing for BRCA1/2 germline mutations. We observed increased CBC risk not only for the BRCA1/2 mutation carriers but also for the BRCA1/2 non-carriers. At present, we are conducting multi-gene panel testing for the BRCA1/2 non-carriers to understand the mechanisms of the increased CBC risk.

Citation Format: Eunhye Kang, Ji-Jung Jung, Hyunsu Yeoh, Changjin Lim, Jang-il Kim, Jung Whan Chun, Hong-Kyu Kim, Han-Byoel Lee, Wonshik Han, Hyeong-Gon Moon. Contralateral breast cancer risk in patients with or without BRCA mutation [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-02-14.

Role of Doppler US and elastography prior to biopsy to identify candidates for avoidance of surgery following neoadjuvant chemotherapy for breast cancer

PURPOSE

This study aimed to evaluate the role of Doppler ultrasound (US) and elastography to identify residual breast cancer for patients showing near complete response following chemotherapy on magnetic resonance imaging (MRI).

METHODS

Between September 2016 and January 2018, 40 breast cancer patients who showed near complete response (either tumor size ≤0.5 cm or lesion-to-background parenchymal signal enhancement ratio ≤1.6) on MRI following neoadjuvant chemotherapy were prospectively enrolled. After excluding seven women who did not undergo Doppler US and elastography, 33 women (median age, 49 years; ranges, 32 to 67 years) were analyzed. On the day of surgery, women underwent Doppler US and elastography for tumor bed prior to US-guided core needle biopsy. Histopathologic results of biopsy and surgery were evaluated. Negative predictive value (NPV) and false negative rate (FNR) of biopsy and the combined Doppler US and elastography were analyzed, respectively.

RESULTS

After surgery, nine women had residual cancers and 24 women had pathologic complete response. The NPV and FNR of biopsy were 92% (24 of 26) and 22% (2 of 9), respectively. The NPV and FNR of combined Doppler US and elastography were 100% (14 of 14) and 0% (0 of 9), respectively. All of nine women with residual cancers had positive vascularity or elasticity. Two women with false-negative biopsy results, having 0.3 cm or 2.5 cm ductal carcinoma in situ at surgery, showed positive vascularity or elasticity.

CONCLUSION

Tumor bed showing positive vascularity or elasticity indicates residual breast cancer for patients showing near complete response on MRI following chemotherapy.

Protocol for the postoperative radiotherapy in N1 breast cancer patients (PORT-N1) trial, a prospective multicenter, randomized, controlled, non-inferiority trial of patients receiving breast-conserving surgery or mastectomy

Background

Postoperative radiotherapy (PORT) could be useful for pN1 breast cancer patients who have undergone breast-conserving surgery (BCS) or mastectomy. However, the value of regional nodal irradiation (RNI) for BCS patients, and the indications for post-mastectomy radiotherapy (PMRT) for pN1 breast cancer mastectomy patients, have recently been challenged due to the absence of relevant trials in the era of modern systemic therapy. “PORT de-escalation” should be assessed in patients with pN1 breast cancer.

Methods

The PORT-N1 trial is a multicenter, randomized, phase 3 clinical trial for patients with pN1 breast cancer that compares the outcomes of control [whole-breast irradiation (WBI) and RNI/PMRT] and experimental (WBI alone/no PMRT) groups. PORT-N1 aims to demonstrate non-inferiority of the experimental group by comparing 7-year disease-free survival rates with the control group. Female breast cancer patients with pT1-3 N1 status after BCS or mastectomy are eligible. Participants will be randomly assigned to the two groups in a 1:1 ratio. Randomization will be stratified by surgery type (BCS vs. mastectomy) and histologic subtype (triple-negative vs. non-triple-negative). In patients who receive mastectomy, dissection of ≥5 nodes is required when there is one positive node, and axillary lymph node dissection when there are two or three positive nodes. Patients receiving neoadjuvant chemotherapy are not eligible. RNI includes a “high-tangent” or wider irradiation field. This study will aim to recruit 1106 patients.

Discussion

The PORT-N1 trial aims to verify that PORT de-escalation after BCS or mastectomy is safe for pN1 breast cancer patients in terms of oncologic outcomes and capable of reducing toxicity rates. This trial will provide information crucial for designing PORT de-escalation strategies for patients with pN1 breast cancer.

Trial registration

This trial was registered at ClinicalTrials.gov (NCT05440149) on June 30, 2022.

Retrospective Cohort Study on the Longterm Oncologic Outcomes of Sentinel Lymph Node Mapping Methods (Dye-Only Versus Dye and Radioisotope Mapping) in Early Breast Cancer: A Propensity Score-Matched Analysis

Purpose

In sentinel lymph node (SLN) biopsy (SLNB) during breast cancer surgery, SLN mapping using dye and isotope (DUAL) may have lower false-negative rates than the dye-only (DYE) method. However, the longterm outcomes of either method are unclear. We aimed to compare longterm oncological outcomes of DYE and DUAL for SLNB in early breast cancer.

Materials and Methods

This retrospective single-institution cohort study included 5,795 patients (DYE, 2,323; DUAL, 3,472) with clinically node-negative breast cancer who underwent SLNB and no neoadjuvant therapy. Indigo carmine was used for the dye method and Tc99m-antimony trisulfate for the isotope. To compare longterm outcomes, pathologic N0 patients were selected from both groups, and propensity score matching (PSM), considering age, pT stage, breast surgery, and adjuvant treatment, was performed (1,441 patients in each group).

Results

The median follow-up duration was 8.7 years. The median number of harvested sentinel nodes was 3.21 and 3.12 in the DYE and DUAL groups, respectively (p=0.112). The lymph node-positive rate was not significantly different between the two groups in subgroups of similar tumor sizes (p>0.05). Multivariate logistic regression revealed that the mapping method was not significantly associated with the lymph node-positive rate (p=0.758). After PSM, the 5-year axillary recurrence rate (DYE 0.8% vs. DUAL 0.6%; p=0.096), and 5-year disease-free survival (DYE 93.9% vs. DUAL 93.7%; p=0.402) were similar between the two groups.

Conclusion

Dye alone for SLNB was not inferior to dual mapping regarding longterm oncological outcomes in early breast cancer.

Targeting CLK4 inhibits the metastasis and progression of breast cancer by inactivating TGF-β pathway

Triple-negative breast cancer (TNBC) represents the most aggressive subtype of breast cancer that is highly resistant to current therapeutic options. According to the public databases Oncomine and KM plotter, the CLK4 expression is correlated with poor patient survival in TNBC, especially in mesenchymal-like TNBC (MES-TNBC) that has strong metastatic potential. Therefore, we investigated the potential involvement of CLK4 in the metastasis and progression of MES-TNBC. In the MES-TNBC cell lines, the CLK4 expression was elevated. Notably, the RNAi-mediated silencing of CLK4 reduced the expression of multiple epithelial-mesenchymal transition (EMT) genes that mediate metastasis. Furthermore, CLK4 silencing reduced both the invasive behaviors of the cultured cells and tumor metastasis in the mouse xenograft model. It is also noteworthy that CLK4 silencing repressed the invasive and cancer stem cell (CSC) properties that are induced by the TGF-β signaling. Importantly, the pharmacological inhibition of CLK4 potently repressed the invasion and proliferation of MES-TNBC cell lines and patient-derived cells, which demonstrates its clinical applicability. Collectively, our results suggest that CLK4 plays a crucial role in invasion and proliferation of MES-TNBC, especially in the processes that are induced by TGF-β. Also, this study characterizes CLK4 as a novel therapeutic target in breast cancer.

Abstract 6373: Spheroid culture of ER+ breast cancer patient-derived tumor cells enriches cancer stem-likecells with EpCAM-/CD49f+and high ALDH activity and poor prognostic gene signatures

Background: Cancer stem-like cells (CSCs) represent a critical subset of the tumor population, which contributes to tumor recurrence, metastasis and therapy resistance. Spheroid culture is unique method for CSC enrichment. Patient-derived breast cancer cells (PDBCCs) has provided an invaluable tool in preclinical and translational research. The objective of this study is to characterize the immunophenotype and transcriptomes of PDBCCs grown in the adherent monolayer and spheroid condition.

Methods: PDBCCs were harvested from residual tumor of fresh surgical specimens of patients with ER-positive subtype (8 cases). The adherent monolayer(M) and spheroid(S) culture of PDBCCs were applied on collagen I-coated plate and an ultra-low attachment polymer-X coated plate. Flow cytometry and immunocytochemistry was performed by using fluorescent-dye conjugated antibodies for EpCAM, CD49f, CD24, CD44, and cytokeratin. ALDEFLUOR® assay to detect ALDH activity was used. Total RNA-sequencing was applied to investigate differentially expressed genes (DEGs), followed by GO and KEGG pathway enrichment analysis. Real-time RT-PCR was performed to evaluate BCSC-related RNA levels. The Kaplan-Meier Plotter online database was used to evaluate the prognostic value of DEGs (2-fold change, p<0.05).

Results: Under adherent monolayer condition, more than 95% of PDBCCs passaged for up to 5 passages on collagen I-coated plate sustained EpCAM+/cytokeratin+/fibroblast marker_ phenotype. On polymer-X coated plates, PDBCCs formed compact multicellular spheroids with a diameter of less than 300 µm. As compared with monolayer, CSCs with EpCAM-/CD49f+ phenotype (M vs S; 0.16±0.06 vs 2.34±0.65, p=0.015) and high ALDH activity (M vs S; 0.73±0.43 vs 7.05±1.48, p=0.038) were significantly increased by spheroid culture. In whole-transcriptome analysis (3 cases) between spheroid and monolayer, a total of 561 DEGs were identified, including 290 upregulated and 271 downregulated DEGs (2- fold change, p<0.05) in spheroid. The upregulated and downregulated DEGs in spheroids were enriched in 8 and 19 KEGG pathways, respectively. In recurrence-free survival analysis based on the Kaplan-Meier Plotter database of the genes corresponding to Oncotype Dx, Mammaprint, and Prosigna and top 30 ranked DEGs identified in spheroids, 15 upregulated and 14 downregulated DEGs were associated with poor prognosis of breast cancer patients.

Conclusion: Spheroid culture of PDBCCs with ER+ subtype enriches CSCs and poor prognostic gene signatures. Future studies to explore the specific molecular mechanisms underlying these observations may provide new molecular targets for the development of therapies for targeting CSCs in breast cancer patient.

Citation Format: Hoe Suk Kim, Seungyeon Ryu, So-Hyun Yoon, Sangeun Lee, Junhyuk Song, Yoonjung Choi, Moonjou Baek, Han-Byoel Lee, Sangyong Jon, Daeyoup Lee, Wonshik Han. Spheroid culture of ER+ breast cancer patient-derived tumor cells enriches cancer stem-likecells with EpCAM-/CD49f+and high ALDH activity and poor prognostic gene signatures [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 6373.

Abstract 6039: Application of triple negative breast cancer patient-derived organoid and xenograft model for drug screening

Background: Breast cancer Patient Derived Organoids (PDOs) and patient-derived xenografts (PDXs) which recapitulate the tumor heterogeneity and molecular signatures of original tumor tissue, are useful tools to enable greater precision of both approved and experimental medicines through personalized therapeutic approaches. We focus on use of ex vivo PDOs, PDX-derived organoids (PDXOs), and vivo PDXs models for drug testing and personalized therapy. In this study, we investigated the oncogenic role and therapeutic potency of targeting WEE1 in breast cancer.

Methods: Fresh surgical specimens of primary TNBC breast tumor (N=3) were used for PDOs. PDOs and PDX-derived organoids (PDXOs) were cultured in previously reported media compositions based on ECM hydrogel. PODs and PDXOs were subjected to drug screening for 22 anticancer drugs including chemoreagents and targeted drugs in the 3D HTS system. Drug sensitivity was tested in triplicate in different concentration ranges for 7 days. The IC50 for each drug was calculated by a sigmoidal dose-response curve, using the GraphPad Prism 9 program. For drug screening in PDXs models, PDOs were injected into the fourth mammary fat pads of NOD.Cg-Prkdcscid Il2rgtm1wjl/SzJ mice. WEE1 inhibitor (AZD1775) was administered by oral gavage (AZD1775, 30 mg/kg) for 3 weeks. Immunostaining of ER, PR, Her2, CK5 and Ki67 was performed in PODs, PODXs and PDX tumor tissues.

Results: All PDOs, PDXs, and PDXOs were ER-, PR- and HER2- negative. PDOs and PDXOs (172T, 185T, 207T) showed differential response to 22 anticancer drugs. In PDOs and PDXOs models, 172T and 207T PDOs and PDXOs are highly sensitive to AZD1775, but 185T PDOs and PDXOs less sensitive or never respond to treatment with AZD1775 (10 µM). In PDX models, treatment with AZ1775 decreased tumor growth (P<0.0079) as well as distance metastasis in 207T-PDX mice, whereas in 172T- and 185T-PDX mice, the tumor growth and metastasis were not reduced compared with the vehicle group.

Conclusion: Consequently, PDOs, PDXOs and PDXs recapitulated immunohistological signatures of original tumor tissues. The results of WEE1 inhibitor response between PDOs, PDXOs and PDXs were consistent. This study may provide a preclinical tool to screen drug responses to standard-of-care and newly identified drugs.

Citation Format: Seungyeon Ryu, Hoe Suk Kim, Jung Eun KIM, So-Hyun Yoon, Sangeun Lee, Moonjou Baek, Han-Byoel Lee, Dong Woo Lee, Bosung Ku, Wonshik Han. Application of triple negative breast cancer patient-derived organoid and xenograft model for drug screening [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 6039.

Abstract 2369: The NRF2 and dimeric STAT3 complex coordinately regulates IL-23 expression: Implications for breast cancer progression

Basal-like breast cancer (BLBC) is an aggressive malignancy with a poor prognosis. Persistent activation of NRF2 and STAT3 is considered to stimulate the aggressive behavior of BLBC. An online database, NRF2-ome predicted the possibility of interplay between NRF2 and STAT3 based on domain motif interactions. However, cooperation between NRF2 and STAT3 and its implications for breast cancer progression remain elusive. Immunoprecipitation and in situ proximity analyses revealed that NRF2 and STAT3 directly interact with each other, which predominantly occurred in the nucleus of human breast cancer cells. After confirming the physical interaction between STAT3 and NRF2, we examined whether this could influence the expression or stability of each transcription factor. While silencing of NRF2 failed to alter the STAT3 expression, STAT3 knockdown facilitated degradation of NRF2. Of note, silencing of STAT3 did not affect the mRNA expression of NRF2, suggesting that STAT3-induced accumulation of NRF2 is attributable to stabilization of the preexisting protein. As the NRF2-STAT3 complex was found to accumulate predominantly in the nucleus, we speculate that NRF2 could bind to a functionally active phosphorylated form of STAT3 (P-STAT3Y705). The substitution of Y705 of STAT3 with the non-phosphorylatable phenylalanine (STAT3Y705F) abolished interaction with NRF2. Notably, the dimeric form, but not a monomeric form, of STAT3 interacts directly with the Neh1 and Neh3 domains of NRF2. Next, we investigated the functional significance of STAT3- NRF2 interaction in BLBC growth in vivo. STAT3 knockdown significantly reduced expression of NRF2 in the xenograft tumor tissues derived from MDA-MB-231 human breast cancer cells. Tumors derived from cells transfected with the non-specific control siRNA showed a pronounced interaction between STAT3 and NRF2, whereas such interaction was abolished in the STAT3-silenced xenograft tumor. Analysis of the TCGA multi-omics data showed that high levels of STAT3 and NRF2 mRNA transcripts were correlated with elevated expression of P-STAT3Y705 and NRF2 target proteins in breast cancer patients. Next generation RNA sequencing analysis identified the gene encoding interleukin-23A (IL-23A) upregulated by concurrent binding of STAT3 and NRF2 to its promoter. IL-23A is markedly overexpressed in BLBC, compared with other subtypes of breast cancer. Combined silencing of NRF2 and STAT3 inhibited BLBC growth to a greater extent than that achieved with single siRNA transfection. IL-23A depletion by siRNA also showed the similar phenotypic changes to those caused by double knockdown of both transcription factors. In conclusion, these findings suggest that the STAT3-NRF2 interaction accelerates BLBC growth and progression by augmenting IL-23A expression, which underscores the importance of subtype-specific molecular pathways in human breast cancer.

Citation Format: Su-Jung Kim, Soma Saeidi, Nam-Chul Cho, Seung Hyeon Kim, Han-Byoel Lee, Wonshik Han, Hye-Kyung Na, Young-Joon Surh. The NRF2 and dimeric STAT3 complex coordinately regulates IL-23 expression: Implications for breast cancer progression [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 2369.

Abstract 6241: Macc1 regulates breast cancer progression and metastasis via remodeling tumor immune microenvironment

Although the established cancer cell lines exhibit less degrees of intratumoral heterogeneity when compared to human solid tumors, studies have suggested that, even within the same cancer cell line, substantial degree of heterogeneity may exist. In this study, we have performed single cell cloning experiment using 4T1 mouse mammary carcinoma cell line and compared the phenotypes of different clones. When compared to the parental 4T1 cell line, one clone (C12) showed markedly different phenotype by exhibiting less aggressive features in vitro and significantly slower tumor growth and metastasis in vivo. The tumor tissue of the C12 showed significant alteration in immune microenvironment as higher number of recruited immune cells including T and B cells. RNA sequencing of the C12 clones and parental 4T1 cells identified Macc1 as a significantly up-regulated gene in parental 4T1 cells. Metastasis-associated colon cancer 1 (MACC1) has been associated with poor prognosis and the promotion of metastasis within several types of cancer, especially colon cancer. The gene encoding the hepatocyte growth factor (HGF) receptor, MET, is a transcriptional target of MACC1. Next, we established Macc1-silenced 4T1 cells using the parental 4T1 cells and observed that Macc1-silencing resulted in a similar phenotype seen in the C12 clone; decreased cell proliferation and migration in vitro and slow tumor growth and metastasis in vivo. To mimic the metastasis in vitro, intravasation was determined as which tumor cells were co-cultured with HUVEC, human umbilical vein endothelial cells. We discovered tumor cell penetration into HUVEC cells was blocked in Macc1-silencing 4T1 group. According to CD45, CD3, and CD19 immunohistochemistry, we also defined immune cells, especially T and B cells, were highly infiltrated in Macc1-silencing tumor like as C12 clone tumor. These results were also reconstructed in EMT6, another TNBC mouse cell line model. In this study, we show that MACC1 can regulate tumor progression and metastasis by remodeling of immune microenvironment.

Citation Format: Hye-Youn Son, Woo Hang Heo, Song Bin Li, Mingji Quan, Yu Jeong Her, Kyu-Jin Lee, Ju Hee Kim, Han-Byoel Lee, Wonshik Han, Hyeong-Gon Moon. Macc1 regulates breast cancer progression and metastasis via remodeling tumor immune microenvironment [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 6241.

Effect of neoadjuvant versus adjuvant chemotherapy on ipsilateral breast tumor recurrence after breast-conserving surgery and whole-breast irradiation

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Background: Early Breast Cancer Trialists’ Collaborative Group conducted a large meta-analysis and reported that patients who underwent neoadjuvant chemotherapy (NAC) had higher ipsilateral breast tumor recurrence (IBTR) rate than those with adjuvant chemotherapy. However, since the study was conducted with patients treated two decades ago, the results could not reflect the advance in treatments and IBTR rate was much higher than in recent studies, Thus, we investigated the association between chemotherapy settings and IBTR rates in breast cancer patients. Methods: We retrospectively reviewed the data of 5,307 patients who underwent breast conserving surgery followed by whole breast irradiation between January 2004 and December 2018 in a single institution. Patients who underwent mastectomy or omitted chemotherapy were excluded. Results: The 1,473 patients who underwent NAC showed significantly higher IBTR rate than the 3,564 patients who underwent adjuvant chemotherapy (10-year risk: 4.5% vs. 4.0%; log-rank p=0.045, hazard ratio 1.42 [95%CI,1.01-1.99]). The difference was more evident for patients with hormone receptor (HR) positive and human epidermal growth factor receptor-2 (HER2) negative tumor (unadjusted p=0.001, hazard ratio 2.27 [95%CI,1.37-3.74; adjusted p=0.002, hazard ratio 2.80 [95%CI,1.45-5.42]], and the statistical significance was still remained after 1:1 propensity score matching (p=0.026). In contrast, patients with other subtypes did not show significant differences between two groups. Conclusions: Patients who underwent NAC for HR+/HER2- tumors carry increased risk of IBTR than those who underwent adjuvant chemotherapy. Our observation supports the need for considering tumor subtypes in initial treatment. In addition, more intensive surveillance would be needed for patients with HR+/HER2- tumors after NAC.

A randomized, prospective, multicenter trial of 3D printing, a patient-specific surgical guide for breast-conserving surgery after neoadjuvant chemotherapy: Comparative evaluation according to the presence or absence of surgical guide

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Background: To obtain a clear resection margin during breast-conserving surgery (BCS) after neoadjuvant chemotherapy (NCT), accurate targeting of the location and assessment extent of the tumor are essential. However, conventional targeting methods such as USG/MMG guided hook wire insertion have disadvantages in that they could only localize the tumor, not reflecting its extent. To assess this problem, we developed an MRI-based 3D printed breast surgical guide (3DP-BSG) and conducted a multicenter randomized clinical study to prove its clinical effectiveness. Methods: In this multicenter, randomized (1:1), controlled trial (KCT0004469), we assigned 566 patients who underwent NCT and planned to undergo BCS, to use customized 3DP-BSG for lumpectomy, or not to use 3DP-BSG for lumpectomy. We assumed that 3DP-BSG group achieve non-inferior outcomes compared with control group with conventional targeting method. The primary endpoint was the margin positivity of the first resected margin. Under the assumption that the proportion of margin positivity would be 23% in both groups, a total of 438 patients were calculated to have 80% power to establish non-inferiority with a margin of 10% at a one-sided significance level of 0.05. Efficacy was assessed in the intention-to-treat (ITT) population. Results: Between 2019 and 2021, 282 (49.8%) patients were assigned to 3DP-BSG group, and 284 (50.2%) patients were assigned to control group with conventional targeting method. The median age was 51 years. In the ITT analysis, first resected margin was positivity in 5 (2.1%) of 235 patients in 3DP-BSG group and 7 (2.9%) of 244 patients in control group (difference -1.15 [95% CI -3.58 to -1.28], pnon-inferiority <.0001). In the analysis of population excluding patients assessed as complete response (CR), first resected margin was positivity in 5 (3.40%) of 147 patients in 3DP-BSG group and 7 (4.8%) of 145 patients in control group (difference -1.43 [95% CI -5.25 to -2.40], pnon-inferiority <.0001). Most of the cases, marked areas with 3DP-BSG were partially different from those with conventional targeting method, and there were some cases where completely different areas were marked. In most of these cases, pathological CR made it difficult to compare the accuracy of the targeting methods, but in one case, a malignant tumor was diagnosed only in the 3DP-BSG targeting region. Even lesions that have been incorrectly targeted by conventional methods can be properly removed using 3DP-BSG, which is believed to be helpful in surgery. Conclusions: Lumpectomy using 3DP-BSG showed non-inferiority compared to the conventional targeting group, and the surgeon's satisfaction was higher by quantitatively presenting the extent of initial tumor. Clinical trial information: KCT0004469.

Spatial epitranscriptomics reveals A-to-I editome specific to cancer stem cell microniches

Epitranscriptomic features, such as single-base RNA editing, are sources of transcript diversity in cancer, but little is understood in terms of their spatial context in the tumour microenvironment. Here, we introduce spatial-histopathological examination-linked epitranscriptomics converged to transcriptomics with sequencing (Select-seq), which isolates regions of interest from immunofluorescence-stained tissue and obtains transcriptomic and epitranscriptomic data. With Select-seq, we analyse the cancer stem cell-like microniches in relation to the tumour microenvironment of triple-negative breast cancer patients. We identify alternative splice variants, perform complementarity-determining region analysis of infiltrating T cells and B cells, and assess adenosine-to-inosine base editing in tumour tissue sections. Especially, in triple-negative breast cancer microniches, adenosine-to-inosine editome specific to different microniche groups is identified.

The spatial context of epitranscriptomic features in the tumour microenvironment remains poorly understood. Here, a method for transcriptomic and epitranscriptomic analysis of immunofluorescence-stained tissue, Select-seq, is applied to stem cell-like microniches in triple negative breast cancer.

HER2 expression, copy number variation and survival outcomes in HER2-low non-metastatic breast cancer: an international multicentre cohort study and TCGA-METABRIC analysis

BACKGROUND

HER2-low breast cancer (BC) is currently an area of active interest. This study evaluated the impact of low expression of HER2 on survival outcomes in HER2-negative non-metastatic breast cancer (BC).

METHODS

Patients with HER2-negative non-metastatic BC from 6 centres within the Asian Breast Cancer Cooperative Group (ABCCG) (n = 28,280) were analysed. HER2-low was defined as immunohistochemistry (IHC) 1+ or 2+ and in situ hybridization non-amplified (ISH-) and HER2-zero as IHC 0. Relapse-free survival (RFS) and overall survival (OS) by hormone receptor status and HER2 IHC 0, 1+ and 2+ ISH- status were the main outcomes. A combined TCGA-BRCA and METABRIC cohort (n = 1967) was also analysed to explore the association between HER2 expression, ERBB2 copy number variation (CNV) status and RFS.

RESULTS

ABCCG cohort median follow-up was 6.6 years; there were 12,260 (43.4%) HER2-low BC and 16,020 (56.6%) HER2-zero BC. The outcomes were better in HER2-low BC than in HER2-zero BC (RFS: centre-adjusted hazard ratio (HR) 0.88, 95% CI 0.82-0.93, P < 0.001; OS: centre-adjusted HR 0.82, 95% CI 0.76-0.89, P < 0.001). On multivariable analysis, HER2-low status was prognostic (RFS: HR 0.90, 95% CI 0.85-0.96, P = 0.002; OS: HR 0.86, 95% CI 0.79-0.93, P < 0.001). These differences remained significant in hormone receptor-positive tumours and for OS in hormone receptor-negative tumours. Superior outcomes were observed for HER2 IHC1+ BC versus HER2-zero BC (RFS: HR 0.89, 95% CI 0.83-0.96, P = 0.001; OS: HR 0.85, 95% CI 0.78-0.93, P = 0.001). No significant differences were seen between HER2 IHC2+ ISH- and HER2-zero BCs. In the TCGA-BRCA and METABRIC cohorts, ERBB2 CNV status was an independent RFS prognostic factor (neutral versus non-neutral HR 0.71, 95% CI 0.59-0.86, P < 0.001); no differences in RFS by ERBB2 mRNA expression levels were found.

CONCLUSIONS

HER2-low BC had a superior prognosis compared to HER2-zero BC in the non-metastatic setting, though absolute differences were modest and driven by HER2 IHC 1+ BC. ERBB2 CNV merits further investigation in HER2-negative BC.

Polygenic risk scores for prediction of breast cancer risk in Asian populations

PURPOSE

Non-European populations are under-represented in genetics studies, hindering clinical implementation of breast cancer polygenic risk scores (PRSs). We aimed to develop PRSs using the largest available studies of Asian ancestry and to assess the transferability of PRS across ethnic subgroups.

METHODS

The development data set comprised 138,309 women from 17 case-control studies. PRSs were generated using a clumping and thresholding method, lasso penalized regression, an Empirical Bayes approach, a Bayesian polygenic prediction approach, or linear combinations of multiple PRSs. These PRSs were evaluated in 89,898 women from 3 prospective studies (1592 incident cases).

RESULTS

The best performing PRS (genome-wide set of single-nucleotide variations [formerly single-nucleotide polymorphism]) had a hazard ratio per unit SD of 1.62 (95% CI = 1.46-1.80) and an area under the receiver operating curve of 0.635 (95% CI = 0.622-0.649). Combined Asian and European PRSs (333 single-nucleotide variations) had a hazard ratio per SD of 1.53 (95% CI = 1.37-1.71) and an area under the receiver operating curve of 0.621 (95% CI = 0.608-0.635). The distribution of the latter PRS was different across ethnic subgroups, confirming the importance of population-specific calibration for valid estimation of breast cancer risk.

CONCLUSION

PRSs developed in this study, from association data from multiple ancestries, can enhance risk stratification for women of Asian ancestry.

Abstract P3-18-12: Achieving negative margin after repeated attempts for lumpectomy does not nullify the risk of ipsilateral breast tumor recurrences

Introduction: Currently, the widely accepted principle in managing lumpectomy margins in early breast cancer patients is to avoid the presence of tumor cell at the margin. The presence of tumor cells on lumpectomy margin can represent two different aspects of local control in breast cancer. One aspect is related to the potential technical failure that may lead to an incomplete resection of the tumor. The other aspect of positive margin is associated with a biologic nature of the tumor. For example, some tumors show features of extensive intraductal component which often result in positive lumpectomy margins and may lead to increased risk of local recurrence after breast conservation surgery. Therefore, the two-fold increase of IBTR risk with positive margin would be the reflection of the combined effect of both technical failure and the biologic features.In this study, we aimed to address this issue by investigating the IBTR rates of patients in whom negative margins were achieved by initial lumpectomy or by re-excision. Our assumption was if the IBTR rates of the two groups are identical, then the two-fold increase of IBTR risk is mostly caused by the technical incomplete resection and therefore the measures to achieve negative margins would be justified. Methods: We retrospectively reviewed the data of 5,633 patients who underwent breast conservation surgery and whole breast irradiation for invasive breast cancer between January 2004 and December 2018 from Seoul National University Hospital. During the period, a total of 828 patients had positive lumpectomy margin after their initial surgery. Among them, thirty-five patients who did not undergo re-operation were excluded due to the small sample size. Results: The median age of the studied patients was 49 years old (19-92), and nearly two third of the patients had T1 tumors (64.3%). 4,293 patients (76.7%) were node negative and 4,332 patients (77.4%) had hormone receptor positive tumors. During the median follow-up period of 76.6 ( ± 44.6) months, a total of 121 patients (2.2%) experienced IBTR. Patients who underwent re-excision to achieve negative margins experienced significantly higher rate of IBTR compared to patients in whom the margins were clear at the first lumpectomy (p=0.031, HR: 1.61; 95% C.I., 1.04-2.48). The survival curves began to separate around 4-5 years after surgery (98.5% vs 98.0% at 5 year and 97.4% vs 94.7% at 10 years of follow-up). The survival difference was more clearly observed for younger patients (p=0.033, HR 1.72; 95% C.I., 1.04-2.85 for age less than 50). When the patients were divided according to their hormone receptor and HER2 amplification status, we observed significant difference in HR+/HER2- and HR-/HER2- subtypes while the HER2-amplified tumors showed no significant differences.By using Cox regression analysis, we adjusted for other significant predictors of IBTR such as age, histologic grade, lymphovascular invasion, hormone receptor status, HER2 amplification status, and Ki-67 levels. The results of the Cox regression analysis showed that re-excision to achieve negative margin is significantly associated with the risk of IBTR after adjusting for these variables (p=0.023, HR: 1.72; 95% C.I., 1.08-2.74). Conclusion: Patients who underwent re-excision after lumpectomy for initial positive margin carry increased risk of developing IBTR even they achieve final negative margin when compared to patients with initially negative lumpectomy margin. Our observation indicate that a substantial proportion of the increasing risk of IBTR associated with positive lumpectomy margin can be attributed to the biologic characteristics of the tumor rather than technical incomplete resection.

Citation Format: Jong Ho Cheun, Hong-Kyu Kim, Han-Byoel Lee, Wonshik Han, Hyeong-Gon Moon. Achieving negative margin after repeated attempts for lumpectomy does not nullify the risk of ipsilateral breast tumor recurrences [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 P3-18-12.

Abstract P3-18-14: Assessment of quality of life and objective cosmetic outcome of breast conserving surgery with or without latissimus dorsi mini-flap in breast cancer

Introduction : Latissimus dorsi mini-flap (LDMF) with breast conserving surgery (BCS) was introduced as a useful volume replacement technique when the tumor is located in upper or outer portion of breast and the tumor size is large requiring extensive excision of breast tissue. However few studies have assessed quality of life (QoL) and objective cosmetic outcome of LDMF in breast cancer surgery. We tried to evaluate those in patients who underwent BCS with or without LDMF. Methods : This study was a prospective, single-center cohort study of patients who underwent LDMF and BCS between 2011 and 2018. As a control, patients who underwent BCS without any volume replacement and the tumor size equal to or greater than 2.5cm on the upper or upper outer of the breast on preoperative imaging. Breast Q questionnaire and body photo were taken at least 1 year after surgery. Two breast surgeons and one plastic surgeon who did not performed LDMF assessed the cosmetic outcome of the patients with photo. Results : 62 patients were in the BCS with LDMF group and 58 patients were in BCS-only group. Pathologic tumor size was significantly larger in LDMF group than BCS-only group (LDMF 3.89cm vs BCS-only 2.92cm, p= 0.001 ). Psychosocial well-being (P= 0.024), physical well-being (P= 0.000), and satisfaction with surgeon (p= 0.006) were significantly better in the BCS-only group than in the LDMF group respectively. But, there were no significant difference in neither sexual well-being (p= 0.286) nor satisfaction for breast (p=0.278) between BCS and LDMF group. In the physicians assessment, there was no significant difference in the cosmetic outcome score between the two groups (LDMF 2.56/4 vs. BCS-only 2.58/4, p= 0.884). Conclusion : In conclusion, physician assessed cosmetic outcome of LDMF was equivalent to that of BCS without LDMF although the tumor size was significantly larger in patients with LDMF. Some inferiority of QoL might be due to postoperative pain or arm movement discomfort. We are planning to evaluate objective cosmetic results using BCCT.core software.

Citation Format: Jang-il Kim, Yireh Han, Changjin Lim, Jong-Ho Cheun, Ji Gwang Jung, Hong Kyu Kim, Han-Byoel Lee, Hyeong-Gon Moon, Wonshik Han. Assessment of quality of life and objective cosmetic outcome of breast conserving surgery with or without latissimus dorsi mini-flap in breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-18-14.