Abstract P3-01-10: Associations between plasma Interleukin 2 (IL-2) and HER2 expression in circulating tumor cell (CTC) and MYC alterations in circulation tumor DNA (ctDNA) open a new insight on immune microenvironment for patients with metastatic breast cancer (MBC)

Introduction: Overexpression of HER2 has been reported to be associated with metastasis and poor prognosis of patients with MBC. We reported in AACR 2018 that HER2 overexpression is associated with CTC-cluster. Preclinical data suggested that MYC and HER2 cooperate to drive stem cell phenotype and poor prognosis in MBC (Nair R). Furthermore, IL-2 upregulates the transcription of MYC (Grigorieva I) and gets involved into its alterations. We reasoned that further understanding of interactions of HER2 in CTC and MYC will be important to elucidate the mechanism of metastasis of MBC. Herein, we report a significant correlation between the plasma IL-2 level and HER2 expression in CTCs, and the IL-2 related MYC ctDNA alterations in MBC.

Methods: This study enrolled 43patients with stage III/IV BCa at the Northwestern Memorial Hospital (2016-2017) that had longitudinally detection of CTCs and ctDNA. Whole blood samples (7.5ml/each) were collected for CTCs enumeration by using CELLTRACKS ANALYZERII® System (Menarini) contains antibodies of anti-EpCAM for capturing CTCs, anti-CK-PE for epithelial cells, DAPI for nucleus, anti-CD45-APC for leukocytes and anti-HER-2/neu-FLU. The CTCs were classified based on phenotype as CK+, EpCAM+, DAPI+ and CD45-.Plasma ctDNA was analyzed using the Guardant360 TM NGS-based assay (Guardant Health), a 73 genes panel. ELISA for IL-2 was performed by using patients' plasma. Database of IL-2, HER2, CTCs and ctDNA was linked with clinical database and analyzed by Kruskal-Wallis test.

Results: CTCs ≥ 5 were found in 20 patients (46%). There were 15 patients that had HER2 negative CTCs (Group 1), and 5 patients had HER2 positive (Group 2) CTCs. The level of IL-2 was much higher in Group 1 (88.17pg) compared to Group 2 (66.81pg), indicating that patients with HER2 positive CTCs have significant lower IL-2 than patients with negative CTCs (P=0.02). Meanwhile, ctDNA MYC alterations were detected in 10 patients (including 1 L114R mutation, 7 CNV and 2 SNV) who have the average IL-2 level as 94.00pg. There were 11 patients without any alterations of MYC had average IL-2 level of 70.17pg, which indicated that patients with alterations in the ctDNA MYC have significant higher level of IL-2 in compared with patients without MYC alterations (P=0.02).

Conclusions: Findings of the correlation between overexpression of HER2 in CTCs and low IL-2 level indicated that low immunity may contribute to more aggressive MBC. And the higher level of IL-2 appear associated predominantly with MYC genomic alterations indicated that overexpression of MYC may also stimulate the immune response by upregulating IL-2 via a reverse feedback pathway. We postulated that increasing IL-2 suppresses the HER2 expression in CTC and breaks cooperation between HER2 and MYC. Although the interactions between them still unknown, our results suggest that IL-2 related immune microenvironment acts as a key player to suppress HER2- and MYC-mediated progress in MBC, including the formation of CTC-cluster. Monitoring and administration of IL-2 may benefit pretreated MBC patients and predict disease metastasis.

Citation Format: Zhang Q, Gerratana L, Zhang Y, Flaum L, Shah A, Davis A, Behdad A, Gradishar W, Platanias L, Cristofanilli M. Associations between plasma Interleukin 2 (IL-2) and HER2 expression in circulating tumor cell (CTC) and MYC alterations in circulation tumor DNA (ctDNA) open a new insight on immune microenvironment for patients with metastatic breast cancer (MBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-01-10.

Abstract P4-01-14: Association between interleukin 2 (IL-2) and circulating tumor DNA (ctDNA) is a novel biomarker for patients with metastatic breast cancer (BCa) after systemic therapies

Introduction: The detection and monitoring of ctDNA in metastatic breast cancer showed ability to predict treatment resistance and outcome. But the mechanisms has been a challenge to clinicians. Immune escape and immune tolerance has also been reported to cause BCa progress. Herein, we report a novel finding of the association between plasma IL-2 and the ctDNA in advanced BCa patients who received the systemic therapies, and it is potential utilization in clinic.

Methods: This study enrolled 43 patients with stage III/IV BCa at the Northwestern Memorial Hospital (2016-2017) that had longitudinally detection of ctDNA and circulating tumor cells (CTCs) before (baseline, BL) or 3 months after (first evaluation, FE) systemic therapies respectively. Duplicate whole blood samples (7.5ml/each) were collected in EDTA tubes from these patients. Plasma ctDNA was analyzed using the Guardant360 NGS-based assay (Guardant Health) and CTC enrichment and enumeration were performed in FDA approved semi-automated fluorescence CELLTRACKS ANALYZERII® System (Menarini Silicon Biosystems) by using CELLSEARCH® CXC Kit (Menarini). ELISA (Fisher) for IL-2 was performed by using patients' plasma. Database of IL-2, ctDNA and CTCs was generated and linked with clinical database. Kruskal-Wallis test was used for statistics. We previously reported cut-off of 5.7 was used to dichotomize the prognostic value of ctDNA percentage (%ctDNA) in 2018 ASCO. Matched pairs variations between IL2 levels at BL and at FE were tested through Wilcoxon signed-ranks test. Associations between %ctDNA and IL2 levels were explored through Kruskal-Wallis test. The prognostic impact of IL2 was tested through Cox regression.

Results: CTCs ≥ 5 were found in 23 patients at BL and 21 patients in FE respectively. There were 12 patients that had increase CTCs, and 31 patients with similar or less CTCs FE after systemic therapies. Decreased in CTCs was associated with increased IL-2 (P=0.004).The FE analysis showed that IL-2 dropped significantly in patients with CTC stably ≥5 (from 95.84pg to 79.46pg) after therapies (P<0.001). Furthermore, baselineIL-2 levels were significantly higher in patients with % ctDNA levels ≥5.7 (97.15pg) compared to patients with %ctDNA levels <5.7 (68.64pg) (P=0.0027). No other associations were highlighted in respect to age or number of ctDNA alterations. There was no significant variations between BL and FE levels of IL2 were observed according to BCa subtypes nor in respect to baseline %ctDNA ≥5.7 or CTCs ≥5. Compared with low level of BL IL-2 (<78.3pg) group, high level of BL IL-2 (≥78.3pg) had a significant negative impact on overall survival (OS) (P=0.037) in univariate analysis.

Conclusions: Our findings indicated that aggressive BCa with high level ctDNA mutation are associated with high level of IL-2 and immune response in patients with advanced disease. In addition we confirm a reverse correlation between change of IL-2 and change of CTCs potentially indication of immune escape. In summary, the study shows a dynamic relation between IL-2 level and tumor burden (ctDNA) and immune escape (CTCs) suggesting another potential biomarker to monitor interaction between tumor and immune environment.

Citation Format: Zhang Q, Gerratana L, Zhang Y, Flaum L, Shah A, Davis A, Behdad A, Gradishar W, Platanias L, Cristofanilli M. Association between interleukin 2 (IL-2) and circulating tumor DNA (ctDNA) is a novel biomarker for patients with metastatic breast cancer (BCa) after systemic therapies [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-01-14.

Abstract P5-17-02: Dissecting the biology of inflammatory breast cancer (BC) through cell free DNA and a circulating tumor cells (CTC)-derived signature

Background: The biological characteristics conferring Inflammatory BC's (IBC) distinctive and aggressive clinical features are currently not fully clarified. The aim of this study is to dissect IBC's biology through the integration of DNA and CTC-based circulating biomarkers.

Methods: This study retrospectively analyzed 251 Advanced BC (ABC) patients (pts) treated and longitudinally characterized for CTCs and circulating tumor DNA (ctDNA) at Thomas Jefferson University (Philadephia, PA) and Northwestern University (Chicago, IL). CTCs were enumerated through CellSearch (Menarini Silicon Biosystems), and characterized for HER2 expression using the CellSearch CXC Kit, while ctDNA was analyzed using the Guardant360 NGS assay (Guardant Health) and its percentage (%ctDNA) was classified based on the previously reported cut-off of 5.7% (Gerratana et al 2018). A subset of 117 pts was further characterized for circulating cell-free DNA (ccfDNA) through Qubit® dsDNA HS quantitation Assay (Thermo Fisher Scientific) and quantitative real-time PCR assay for ALU DNA repeats on chromosome 1.Associations between clinical characteristics, CTCs-derived biomarkers and IBC were explored through Fisher's exact test; survival was tested though Cox regression and log-rank test.

Results: Of the total 251 pts, 115 were diagnosed with IBC. Among the 117 patients characterized for ccfDNA, 70 had IBC. Median ccfDNA was 1.59 for IBC (IQR 1.02-3.19) and 2.37 for non-IBC (nIBC) (IQR 1.13-3.52), P=0.27. Consistent results were observed for %ctDNA levels (median value: 2 vs 1.6). The impact on OS of ccfDNA after log transformation was significant for the total population (HR 1.73 95%CI: 1.11-2.69) but not in IBC pts (HR 1.40 95%CI: 0.84-2.34). On the other hand, ctDNA high pts had a significantly worse OS (nIBC: HR 5.34 95%CI: 1.70-18.81 P=0.004; IBC: HR 4.05 95%CI: 1.91-8.58 P< 0.001). In the ctDNA high subgroup no differences in total number of CTCs were observed between IBC and nIBC, while significantly lower CTCs were observed in ctDNA low IBC pts (P=0.0097). The ctDNA low IBC subgroup had a higher incidence of HER2 positive BC (P=0.003) and a significantly lower incidence of CTCs clusters (P=0.006), HER2 positive CTCs (P=0.041). Notably, no associations were observed with stage at baseline, number of metastatic sites, liver, lung and visceral involvement. On the other hand, the ctDNA_high IBC subgroup was characterized by a lower incidence in liver, bone and visceral involvement (P=0.017, P=0.014 and P=0.03 respectively) and a marginally high incidence in soft tissue involvement (0.084). Moreover, IBC diagnosis conferred a significantly worse prognosis only in the ctDNA low subgroup (OS at 12 months nIBC: 100% vs IBC: 70%; P=0.049), while no differences were observed in the ctDNA_high subgroup (OS at 12 months nIBC: 29% vs IBC: 26%; P=0.767).

Conclusion: ctDNA is able to stratify BC according to aggressiveness independently from the sites and type of metastases, both in the IBC and nIBC subgroups. IBC has a distinctive CTCs/ctDNA-based signature, in particular ctDNAlow pts have a lower incidence of HER2 positive CTCs and CTC clusters. This signature is probably due to predominant lymphatic metastatic spread and aggressive phenotype.

Citation Format: Gerratana L, Zhang Q, Wang C, Shah A, Davis AA, Ye Z, Zhang Y, Abu-Khalaf M, Flaum L, Strickland K, Rossi G, Behdad A, Gradishar W, Platanias L, Yang H, Cristofanilli M. Dissecting the biology of inflammatory breast cancer (BC) through cell free DNA and a circulating tumor cells (CTC)-derived signature [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-17-02.

Abstract PD1-14: Induction of epigenetic BRCAness in BRCA1 wild-type triple negative breast cancer: BET inhibition as a therapeutic strategy

Background: Pharmacological induced BRCAness and synthetic lethality could represent a potential therapeutic strategy in triple negative breast cancer (TNBC). Bromodomain and Extra-Terminal proteins (BET) such as BRD2 and BRD4, are involved in controlling RNA polymerase II pause/release transition mediating transcriptional activation and gene bookmarking. BRD4 is found to be associated to enhancer and promoter regions to foster gene expression. Furthermore, BRD4 overexpression is described to be associated with worse outcome and increased metastasizing potential. Aim of this study was to explore novel therapeutic strategies through pharmacological induced epigenetic BRCAness in BRCA1 wild-type TNBC cells by means of BET inhibition.

Methods: The experimental models were based on the BT-549, MDA-MB-157 and MDA-MB-231 TNBC BRCA1 wild type cells lines. Two different pan-BET inhibitors were explored (i.e. JQ1 and I-BET762). BRCA1 and RAD51 levels were evaluated by both qPCR and western blotting as a marker of BRCAness phenotype onset. Chromatin immunoprecipitation (ChIP) and RNA interference (RNAi)-mediated BRD4 silencing were performed on TNBC cells. Synthetic lethality induced by JQ1 (0.5 µM) and the effects of co-treatment with the PARP inhibitor PJ34 (5-15 µM) or cisplatin (2-10 µM) were evaluated by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay.

Results: A dose-dependent reduction in BRCA1 and RAD51 protein levels was observed after treatment with both JQ1 and I-BET762 in all the cell lines tested. To verify the direct relationship between BRD4 and BRCA1/RAD51 expression, a dual approach was performed. First, BRCA1 and RAD51 protein levels were evaluated after RNAi-mediated BRD4 knockdown, verifying that the BRCAness phenotype (exemplified by BRCA1 and RAD51 protein downregulation) was due to the absence of BRD4 protein. Furthermore, a ChIP assay was performed to confirm the direct regulation of BRCA1 and RAD51 promoters by BRD4. To test the gain in sensitivity of BRCAness-displaying TNBC cells towards platinum salts, the effects of cisplatin alone or in combination with BET inhibitors were tested. JQ1 and cisplatin combinations induced a strong reduction in TNBC cell viability in all the three cell lines tested. Moreover, the pharmacological combination between JQ1 and PJ34 displayed a significant cell viability decrease in TNBC wild type cells, corroborating the synthetic lethality mechanism.

Conclusions: A decrease in BRCA1 and RAD51 levels was observed after BET inhibition by means of the JQ1 drug, exploiting synergism with PARP inhibition and use of platinum salts. Moreover, the present results demonstrate the direct interaction between BRD4, BRCA1 and RAD51, supporting the therapeutic rationale behind this novel strategy.

Citation Format: Gerratana L, Puglisi F, Damante G, Mio C. Induction of epigenetic BRCAness in BRCA1 wild-type triple negative breast cancer: BET inhibition as a therapeutic strategy [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD1-14.