Panel Of Breast Cancer Cell Lines Research Articles

Gedatolisib shows superior potency and efficacy versus single-node PI3K/AKT/mTOR inhibitors in breast cancer models

The PI3K, AKT, and mTOR (PAM) pathway is frequently dysregulated in breast cancer (BC) to accommodate high catabolic and anabolic activities driving tumor growth. Current therapeutic options for patients with hormone receptor (HR) + / HER2- advanced BC (ABC) include PAM inhibitors that selectively inhibit only one PAM pathway node, which can lead to drug resistance as cells rapidly adapt to maintain viability. We hypothesized that gedatolisib, which potently inhibits all Class I PI3K isoforms, as well as mTORC1 and mTORC2, may be more effective in BC cells than single-node PAM inhibitors by limiting adaptive resistances. By using multiple functional assays, a panel of BC cell lines was evaluated for their sensitivity to four different PAM inhibitors: gedatolisib (pan-PI3K/mTOR inhibitor), alpelisib (PI3Kα inhibitor), capivasertib (AKT inhibitor), and everolimus (mTORC1 inhibitor). Gedatolisib exhibited more potent and efficacious anti-proliferative and cytotoxic effects regardless of the PAM pathway mutational status of the cell lines compared to the single-node PAM inhibitors. The higher efficacy of gedatolisib was confirmed in three-dimensional culture and in BC PDX models. Mechanistically, gedatolisib decreased cell survival, DNA replication, cell migration and invasion, protein synthesis, glucose consumption, lactate production, and oxygen consumption more effectively than the other PAM inhibitors tested. These results indicate that inhibition of multiple PAM pathway nodes by a pan-PI3K/mTOR inhibitor like gedatolisib may be more effective at inducing anti-tumor activity than single-node PAM inhibitors. A global Phase 3 study is currently evaluating gedatolisib plus fulvestrant with and without palbociclib in patients with HR+/HER2− ABC.

Abstract PO1-24-04: Gedatolisib, a pan-PI3K/mTOR inhibitor, shows superior potency and efficacy relative to other PI3K/AKT/mTOR pathway inhibitors in breast cancer models

Abstract Background: The PI3K, AKT, and mTOR (PAM) pathway is frequently activated in breast cancer (BC). Current standard-of-care therapy options for patients with advanced BC (ABC) include PAM inhibitors (PAMi), such as everolimus and alpelisib, and hormonal therapy, such as letrozole and fulvestrant. Most PAMi selectively inhibit one or only a few PAM pathway components, which can lead to drug resistance. To minimize drug resistance, a more comprehensive inhibition of the multiple PI3K isoforms and downstream mTOR complexes may be required. We hypothesized that gedatolisib, which potently inhibits all Class I PI3K isoforms, as well as mTORC1 and mTORC2, can be more effective in BC cells than a PAMi targeting single PAM pathway components. Methods: A panel of BC cell lines with mutated or non-mutated PAM pathway genes (PIK3CA, PTEN, AKT) were evaluated for their sensitivity to gedatolisib and other PAMi (PI3K-α: alpelisib; AKT: capivasertib; mTORC1: everolimus; pan-PI3K/mTOR: gedatolisib). Cell viability, growth rate inhibition, and cell death were evaluated by luciferase- and fluorescence-based assays, both in monolayer cultures and three-dimensional (3D) cultures on reconstituted basement membrane. Flow cytometry analytical assays were conducted to assess DNA synthesis (EdU incorporation), protein synthesis (OPP incorporation), and PAM pathway activity (RPS6 and 4EBP1 phosphorylation). BC xenograft studies evaluating gedatolisib in vivo were also performed. Results: Gedatolisib strongly inhibited PAM pathway activity and reduced cell viability and growth rate in the cell lines tested. Compared to the other PAMi, gedatolisib exhibited more potent and efficacious anti-proliferative and cytotoxic effects, regardless of the cell lines’ PI3K pathway mutational status. Gedatolisib effects were confirmed in 3D culture on reconstituted basement membrane, where gedatolisib inhibited tumor cell spheroid growth and induced regression. Mechanistically, gedatolisib decreased both DNA and protein synthesis more effectively than the other PAMi tested. Gedatolisib also exerted superior anti-proliferative and cytotoxic effects relative to the other PAMi tested in estrogen receptor-positive BC cell lines concomitantly treated with fulvestrant. BC xenografts confirmed growth inhibitory effects of gedatolisib in vivo. Conclusions: The pan-PI3K/mTOR inhibitor, gedatolisib, may more effectively address potential drug resistance mechanisms associated with narrowly targeted PAM inhibitors. Gedatolisib has previously demonstrated promising preliminary clinical efficacy and safety data in ABC in combination with hormonal therapy. A Phase 3 study (VIKTORIA-1) evaluating gedatolisib plus fulvestrant with and without palbociclib is underway in patients with ABC. Citation Format: Stefano Rossetti, Aaron Broege, Adrish Sen, Salmaan Khan, Ian MacNeil, Jhomary Molden, Igor Gorbatchevsky, Brian F. Sullivan, Lance Laing. Gedatolisib, a pan-PI3K/mTOR inhibitor, shows superior potency and efficacy relative to other PI3K/AKT/mTOR pathway inhibitors in breast cancer models [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-24-04.

Abstract PO3-26-07: Epigenetic approaches to deliver a targeted radiotherapy for triple negative breast cancer

Abstract The sodium iodide symporter (NIS, encoded by SLC5A5) is the sole transporter of iodide, and successfully exploited in thyroid cancer to uptake radioiodide (RAI). NIS is essentially undetected in normal mammary epithelial cells but elevated during lactation, and has a heterogeneous expression profile in breast cancer (BRCA), as evidenced by TCGA cohort and also in a ~120 sample TMA we have profiled. Furthermore, pre-clinical studies support an epigenetic mechanisms that involves Retinoic Acid Receptor alpha (RARa) to regulate SLC5A5 expression. Therefore, we have applied an orthogonal approach to both elucidate and target mechanisms that control NIS expression and function to deliver a therapeutic strategy that targets this transporter as a novel radiotherapy in BRCA. To understand the epigenetic control of expression we segregated samples in the TCGA-BRCA cohort into lower and upper quartile SLC5A5 expression and identified ~600 significant differentially expressed of genes (DEG). Interestingly, restricting analyses to either triple negative (TN) or tumors from African American (AA) patients doubled the number of DEGs. These DEGs were significantly associated with several transcription factors including LHX3, a pituitary development transcription factor regulated by thyroid signaling. The most significantly altered ~70 DEGs significantly clustered tumors by genomic ancestry and ERBB2/HER2 IHC status. The DEGs also supported a footprint of RARa signaling include PRAME, a known RARa co-repressor associated with histone deacetylase, and reflects the finding that NIS expression is highly responsive to SAHA treatment. To investigate if PRAME expression suppresses RARa regulation of SLC5A5 we have established a panel of BRCA cell lines (AU565, SKB3 SUM52 and MDA-MB-231) stably transfected with either CRISPR-VP64 (activator) and CRISPR-KRAB (repressor) to modulate PRAME and measure the epigenomic impact, the expression of SLC5A5 and the ability to transport RAI. In parallel we have applied a drug screen approach that targets non-canonical approaches to govern NIS expression, for example by targeting valosin-containing protein (VCP) that induces NIS proteolysis. In the first instance we have developed a therapeutic strategy to target NIS by inhibiting VCP. Specifically, we are screening a range of VCP inhibitors in combination with the HDAC inhibitor SAHA or the transcriptional potentiator, disulfiram metabolite Cu(DDC)2 in BRCA cell lines by testing the ability to augment RAI uptake. Remarkably, in MDA MB 231 cells, Cu(DDC)2 combined with the VCP inhibitor CB5339, resulted in a significant additive increase in RAI uptake and a prominent decrease in cell proliferation and survival. These studies combined with future murine and PDX testing of CRISPR-edited tumors and drug exposures will develop a comprehensive analyses of the mechanisms that control SLC5A5 expression across breast cancer cell types, how this can be most effectively targeted to restore NIS expression, and exploited to promote RAI as a novel targeted BRCA radiotherapy. Citation Format: Katie Brookes, Martin Read, Sajad Wani, Sissy Jhiang, Daniel Stover, Mathew Ringel, Christopher McCabe, Moray Campbell. Epigenetic approaches to deliver a targeted radiotherapy for triple negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-26-07.

Abstract P49: PROTAC A1874: A Potential Targeted Therapy for Breast Cancer

Abstract Background PROteolysis TArgeting Chimera (PROTAC) A1874 is a heterobifunctional structured compound consisting of a BRD4-recognizing ligand and an MDM2-recognizing ligand that functions to degrade BRD4 via the ubiquitin-proteasome system. A1874 also plays a dual role in downregulating downstream BRD4 regulator, MYC, and stabilizing p53 within nanomolar concentrations. This PROTAC thus presents itself as a potential therapy for both estrogen-receptor positive (ER+) and triple-negative breast cancer (TNBC) subtypes, which typically harbors wild-type p53 and are associated with MYC overexpression respectively. Thus, this study aims to 1) investigate the anti-oncogenic effects and mechanism of A1874 and 2) its effect in combination with existing therapies in several breast cancer (BC) cell lines. Methods A panel of BC cell lines harboring different p53 status were tested for their sensitivity to A1874. Several functional assays were conducted to determine the anti-oncogenic effects of A1874. Bliss scores were calculated using SynergyFinder to determine the interaction of drugs in combination with A1874. Results BC cell lines with p53 WT status showed significantly lower IC50 sensitivity to A1874 in the nanomolar range compared to those with p53 mutation, which exhibited sensitivity in the micromolar range regardless of subtypes. Moreover, it is effective in Tam-resistant ER+, p53 WT cells. A1874 exclusively degrades BRD4 in p53 WT cells and causes G1 arrest, inhibition of colony formation, proliferation, and migration. Knockdown of MDM2 or TP53, and lentiviral transduction of p53 mutant plasmid resulted in significant reduction in sensitivity to A1874 in p53 WT cell lines and abrogate its BRD4-degrading effect. Combination of A1874 with the mutant p53 reactivating drug, PRIMA-1, synergistically resensitize mutant p53 cells to the cytotoxic effect of A1874 across subtypes. Conclusions Our results highlight a promising potential of PROTAC A1874 as a therapeutic drug in breast cancer, specifically the ER+ subtype which typically retains its p53 WT status. Citation Format: Charlie Marvalim, Arpita Datta, Serena Bee Kee Seah, Edward Kai-Hua Chow, Soo Chin Lee. PROTAC A1874: A Potential Targeted Therapy for Breast Cancer [abstract]. In: Proceedings of Frontiers in Cancer Science; 2023 Nov 6-8; Singapore. Philadelphia (PA): AACR; Cancer Res 2024;84(8_Suppl):Abstract nr P49.

Abstract LB_C04: Novel orally bioavailable macrocycles that target cyclin A and B elicit antitumor activity in breast cancer patient-derived xenograft models

Abstract Background: Cyclin/cyclin-dependent kinase (CDK) complexes regulate the activity of RB1 and E2F to drive cell cycle progression while ensuring fidelity of DNA replication. The interaction between cyclins and a critical subset of their substrates, including RB1 and E2F, is mediated by a conserved short linear RxL motif. RxL peptides have been shown to inhibit substrate phosphorylation by CDK2/cyclin A (AACR 2022 poster #5379). Previously, we have shown that macrocycles that selectively inhibit RxL-mediated binding to cyclins A and B (RxL inhibitors) lead to growth inhibitory activity in multiple cancer cell lines, and result in tumor regression in small cell lung cancer (SCLC) and ovarian cancer xenograft models (AACR 2023 poster #1560). Here, we test the antitumor activity of CID-016 in patient-derived xenograft (PDX) models from breast cancer. Methods: Bioinformatic analyses using RNA sequencing (RNAseq) and whole exome sequencing (WES) data from 39 breast cancer cell lines was employed to identify biomarker profiles that associate with sensitivity to CID-016. The antiproliferative activity of CID-016 was assessed by GI50 after 4-8 days of treatment. Hallmark pathway scores were calculated by Gene Set Variation Analysis (GSVA) method using MSigDb Hallmark collection from cell lines and existing PDX models. Based on the calculated hallmark pathway score, triple negative breast cancer (TNBC) PDX models were selected to test the anti-tumor activity of CID-016. In vivo, NMRI-Foxn1nu/nu mice were implanted with tumor fragments in the lower flank and treated with vehicle or CID-016 oral formulation of 50-100 mg/kg BID or 100 mg/kg QD, respectively for at least 28 days. Tumor volume and body weight were measured biweekly. Pharmacodynamic (PD) analyses will be conducted after treatment with CID-016. Results: Treatment of the breast cancer cell line panel with CID-016 demonstrated greater potency by GI50 in TNBC compared to other breast cancer cell lines (p=0.009). Gene expression levels of CCNB1, CCNA2, CCNE1 as well as target hallmark scores for “E2F targets”, “G2M checkpoint” and “Mitotic spindle” were significantly higher in TNBC vs other breast cancer cell lines. Oral treatment with CID-016 resulted in tumor regression in at least one triple-negative breast cancer PDX model and was well tolerated with no significant body weight changes. In vivo PD analyses will be assessed after 5 days of treatment with CID-016. Conclusions: The selective cyclin A/B RxL inhibitor CID-016 exhibits potent antitumor activity in TNBC preclinical models, consistent with the proposed mechanism of RB1/E2F pathway dysregulation. Given their compelling characteristics, orally bioavailable RxL inhibitors are advancing as the only first-in-class orally bioavailable dual inhibitors of cyclins A and B into clinical development. Citation Format: Mariana Paes Dias, Li-Fen Liu, Bernard Levin, Cristina Molina, Marta Guzmán, Olga Rodríguez, Evelyn W. Wang, Violeta Serra. Novel orally bioavailable macrocycles that target cyclin A and B elicit antitumor activity in breast cancer patient-derived xenograft models [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_C04.

Mechanistic and Clinical Evidence Supports a Key Role for Cell Division Cycle Associated 5 (CDCA5) as an Independent Predictor of Outcome in Invasive Breast Cancer.

Cell Division Cycle Associated 5 (CDCA5) plays a role in the phosphoinositide 3-kinase (PI3K)/AKT/mTOR signalling pathway involving cell division, cancer cell migration and apoptosis. This study aims to assess the prognostic and biological value of CDCA5 in breast cancer (BC). The biological and prognostic value of CDCA5 were evaluated at mRNA (n = 5109) and protein levels (n = 614) utilizing multiple well-characterized early stage BC cohorts. The effects of CDCA5 knockdown (KD) on multiple oncogenic assays were assessed in vitro using a panel of BC cell lines. this study examined cohorts showed that high CDCA5 expression was correlated with features characteristic of aggressive behavior and poor prognosis, including the presence of high grade, large tumor size, lymphovascular invasion (LVI), hormone receptor negativity and HER2 positivity. High CDCA5 expression, at both mRNA and protein levels, was associated with shorter BC-specific survival independent of other variables (p = 0.034, Hazard ratio (HR) = 1.6, 95% CI; 1.1-2.3). In line with the clinical data, in vitro models indicated that CDCA5 depletion results in a marked decrease in BC cell invasion and migration abilities and a significant accumulation of the BC cells in the G2/M-phase. These results provide evidence that CDCA5 plays an important role in BC development and metastasis and could be used as a potential biomarker to predict disease progression in BC.

The BH3-only protein NOXA serves as an independent predictor of breast cancer patient survival and defines susceptibility to microtubule targeting agents

Breast cancer (BC) treatment frequently involves microtubule-targeting agents (MTAs), such as paclitaxel, that arrest cells in mitosis. Sensitivity to MTAs is defined by a subset of pro- and anti-apoptotic BCL2 family proteins controlling mitochondrial apoptosis. Here, we aimed to determine their prognostic value in primary tumour samples from 92 BC patients. Our analysis identified high NOXA/PMAIP mRNA expression levels as an independent prognostic marker for improved relapse-free survival (RFS) and overall survival (OS) in multivariate analysis in BC patients, independent of their molecular subtype. Analysis of available TCGA datasets of 1060 BC patients confirmed our results and added a clear predictive value of NOXA mRNA levels for patients who received MTA-based therapy. In this TCGA cohort, 122 patients received MTA-treatment and high NOXA mRNA levels correlated with their progression-free interval (PFI) and OS. Our follow-up analyses in a panel of BC cell lines of different molecular subtypes identified NOXA protein expression as a key determinant of paclitaxel sensitivity in triple-negative breast cancer (TNBC) cells. Moreover, we noted highest additive effects between paclitaxel and chemical inhibition of BCLX, but not BCL2 or MCL1, documenting dependence of TNBC cells on BCLX for survival and paclitaxel sensitivity defined by NOXA expression levels.

Differential Expression and Prognostic Significance of STARD3 Gene in Breast Carcinoma.

StAR related lipid transfer domain containing 3 (STARD3) gene has been reported to be co-amplified with human epidermal growth factor receptor 2 (HER2) in breast carcinoma. STARD3 is necessary for cholesterol transfer and metabolism in tumor cells. The possible role played by STARD3 as a diagnostic and prognostic biomarker was investigated in breast cancer (BC). Data mining was performed using several bioinformatics websites to investigate the correlation of STARD3 with BC and its molecular subtypes, and conventional PCR was used to detect the STARD3 mRNA levels in a panel of BC cell lines. STARD3 was overexpressed in BC more than the other types of cancer. The results also showed that STARD3 expression was significantly associated with HER2+ BC tumors and BC cell lines, and low STARD3 mRNA and protein expression levels were observed in estrogen receptor-positive (ER+) and triple-negative BC (TNBC) patients. Moreover, high STARD3 expression levels predicted worse overall survival (OS), relapse-free survival (RFS) and disease metastasis-free survival (DMFS) in BC, and HER2+ BC. Notably, low expression of STARD3 was associated with poor OS in ER+ BC. Our findings suggest that STARD3 may have strong diagnostic and prognostic value for HER2+ breast carcinoma.

The Anti-Breast Cancer Potential of Bis-Isatin Scaffolds.

To develop novel anti-breast cancer agents and discuss the structure-activity relationship of bis-isatin scaffolds. Breast cancer is the most common invasive cancer and the second leading cause of cancer death in women after lung cancer. Bis-isatin scaffolds possess potential anti-breast cancer activity, and some of them such as Indirubin could induce cancer cells apoptosis via multiply mechanisms. The primary objective of this study was to evaluate the potential of bis-isatin scaffolds with alkyl/ether linkers between the two isatin moieties against different human breast cancer cell lines including MCF-7, AU565, MDA-MB-231, MDA-MB-435 and MDA-MB-468 cells. The synthesized bis-isatin scaffolds with alkyl/ether linker between the two isatin moieties were evaluated for their in vitro activity against MCF-7, AU565, MDA-MB-231, MDA-MB-435, and MDA-MB-468 human breast cancer cell lines by MTT assay. All the synthesized compounds (IC50: 38.3-197.6 µM) possess considerable activity against MCF-7, AU565, MDA-MB-231, MDA-MB-435, and MDA-MB-468 human breast cancer cell lines, and the most potent compound 4e (IC50: 38.3-63.5 µM) was no inferior to Cisplatin (IC50: 20.1-38.6 μM) against the five tested human breast cancer cell lines. All the synthesized bis-isatin scaffolds were active against a panel of breast cancer cell lines, highlighting the significance of exploring the bis-isatin scaffolds to fight against breast cancers. The enriched structure-activity relationship may set up the direction for the rational design and development of novel bis-isatin scaffolds with higher efficiency.

Topoisomerase I activity and sensitivity to camptothecin in breast cancer-derived cells: a comparative study

BackgroundCamptothecin (CPT) and its derivatives are currently used as second- or third-line treatment for patients with endocrine-resistant breast cancer (BC). These drugs convert nuclear enzyme DNA topoisomerase I (TOP1) to a cell poison with the potential to damage DNA by increasing the half-life of TOP1-DNA cleavage complexes (TOP1cc), ultimately resulting in cell death. In small and non-randomized trials for BC, researchers have observed extensive variation in CPT response rates, ranging from 14 to 64%. This variability may be due to the absence of reliable selective parameters for patient stratification. BC cell lines may serve as feasible models for generation of functional criteria that may be used to predict drug sensitivity for patient stratification and, thus, lead to more appropriate applications of CPT in clinical trials. However, no study published to date has included a comparison of multiple relevant parameters and CPT response across cell lines corresponding to specific BC subtypes.MethodWe evaluated the levels and possible associations of seven parameters including the status of the TOP1 gene (i.e. amplification), TOP1 protein expression level, TOP1 activity and CPT susceptibility, activity of the tyrosyl-DNA phosphodiesterase 1 (TDP1), the cellular CPT response and the cellular growth rate across a representative panel of BC cell lines, which exemplifies three major BC subtypes: Luminal, HER2 and TNBC.ResultsIn all BC cell lines analyzed (without regard to subtype classification), we observed a significant overall correlation between growth rate and CPT response. In cell lines derived from Luminal and HER2 subtypes, we observed a correlation between TOP1 gene copy number, TOP1 activity, and CPT response, although the data were too limited for statistical analyses. In cell lines representing Luminal and TNBC subtypes, we observed a direct correlation between TOP1 protein abundancy and levels of enzymatic activity. In all three subtypes (Luminal, HER2, and TNBC), TOP1 exhibits approximately the same susceptibility to CPT. Of the three subtypes examined, the TNBC-like cell lines exhibited the highest CPT sensitivity and were characterized by the fastest growth rate. This indicates that breast tumors belonging to the TNBC subtype, may benefit from treatment with CPT derivatives.ConclusionTOP1 activity is not a marker for CPT sensitivity in breast cancer.

Abstract P2-03-07: Backwards translation: Exploring beta-adrenoreceptors (ßAR) in triple negative breast cancer (TNBC), a novel and druggable pathway

Abstract Introduction: several retrospective studies suggest that ßAR blocking drugs (BB) are associated with improved survival in patients with a wide range of cancers. Recently, we retrospectively showed an association between BB intake and improved progression free survival in patients with HER2 negative advanced breast cancer (BC), particularly striking in triple-negative disease (TNBC) (Reference). Based on this finding we decided to conduct an in silico study in which we have interrogated ßARs in a publicly available BC sample database and the Translational Oncology Research Lab (TORL) translational platform with a genomic, transcriptomic and proteomic approach. Methodology: genomic and transcriptomic data sets for ßAR 1, 2 and 3 were retrieved from cBioPortal considering all BC samples available with this information in The Cancer Genome Atlas (TCGA). Transcriptomic and proteomic data sets from 48 BC cell lines obtained from TORL were queried for ßARs as well and used with validation and exploratory intent. Mutations, amplifications and deletions were queried in DNA; gene expression profiles were interrogated using RNAseq data together with protein expression by RPPA. Average expression, log ratio and fold change in mRNA and Reverse Phase Protein Array (RPPA) quantitative assessments for corresponding proteins were noted. BC cell lines with top 10 mRNA and protein levels of ßAR 1, 2 and 3 were identified. Results: CBioPortal DNA data shows ß AR1 amplified in 1-10% and deleted in 0,4%; ß-AR2 amplified in 1-3% and deleted in 0,1%; ß-AR3 amplified in 15-20% and deleted in 2% of the BC samples. CBioPortal mRNA data shows ß-AR1 is upregulated in 2.7% (mostly Progesterone Receptor negative BC); ßAR2 is upregulated in 4% (mostly TNBC); ßAR3 is upregulated in 4% (mostly HER2 negative BC) in BC samples. TORL cell line panel shows that ßARs are heterogeneously expressed between the BC cell lines (fold change range: ßAR 1 2.015-3.636; ßAR2 2.545-8.248; ßAR3 1.809-2.444). Within the 10 BC cell lines with highest ßAR1 and ßAR2 expression, 7(COLO-824, HCC1937, BT-549, BT-20, HCC1599, HCC1143, HCC1806) and 6 (184A1, MDA-MB-231, 184B5, HCC1806, MCF-10A and MDA-MB-468) of them respectively correspond to the basal BC subtype. RPPA identifies caveolin 1, PAI 1, EGFR and Bax as the proteins with the higher co-expression with ßAR1 and ßAR2. Conclusions: DNA alterations are infrequent in ßARs in BC samples. Transcriptional mRNA data from BC samples shows ßARs mostly expressed in non-luminal BC subtypes, being ßAR 2 the one with highest expression. In silico data results from BC cell line panel show ßAR 1 and ßAR 2 are highly expressed in basal BC subtype. The above data suggest that ßAR, and ßAR 2 in particular could be a relevant target to explore in in vivo BC models. Table 1:mRNA and RPPA in BC cell linesCell lineAverage mRNALog RatioFold ChangeCaveolin 1PAI1EGFR184A1313173.048.244.183.411.72SUM-190223292.811.03-1.37-0.570.09MDA-MB-231151002.997.993.853.251.57184B5130121.973.933.902.361.82HCC1806124112.375.193.750.491.67MCF-10A119122.194.583.892.670.08ZR-75-3093001.893.72-1.51-0.61-0.25JIMT-163541.593.013.082.010.81MDA-MB-41562391.242.370.96-0.39-0.13MDA-MB-46862801.342.541.06-0.251.72 Citation Format: Spera G, Von Euw E, Fresco R, Slamon DJ. Backwards translation: Exploring beta-adrenoreceptors (ßAR) in triple negative breast cancer (TNBC), a novel and druggable pathway [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 P2-03-07.

HER2-positive breast-cancer cell lines are sensitive to KDM5 inhibition: definition of a gene-expression model for the selection of sensitive cases.

Targeting of histone methylation has therapeutic potential in oncology. Here, we provide proof-of-principle that pharmacological inhibition of KDM5 histone-demethylases is a new strategy for the personalized treatment of HER2+ breast cancer. The anti-proliferative effects of the prototype of a new class of selective KDM5-inhibitors (KDM5-inh1) are evaluated in 40 cell lines, recapitulating the heterogeneity of breast cancer. This analysis demonstrates that HER2+ cells are particularly sensitive to KDM5 inhibition. The results are confirmed in an appropriate in vivo model with a close structural analog (KDM5-inh1A). RNA-seq data obtained in HER2+ BT-474 cells exposed to KDM5-Inh1 indicate that the compound alters expression of numerous genes downstream of the ERBB2 gene-product, HER2. In selected HER2-positive breast-cancer cells, we demonstrate synergistic interactions between KDM5-inh1 and HER2-targeting agents (trastuzumab and lapatinib). In addition, HER2+ cell lines with innate and acquired resistance to trastuzumab show sensitivity to KDM5-inh1. The levels of KDM5A/B/C proteins, which are selectively targeted by the agent, have no significant association with KDM5-inh1 responsiveness across our panel of breast-cancer cell lines, suggesting the existence of other determinants of sensitivity. Using RNA-seq data of the breast-cancer cell lines we generate a gene-expression model that is a robust predictor of KDM5-inh1 sensitivity. In a test set of breast cancers, this model predicts sensitivity to the compound in a large fraction of HER2+ tumors. In conclusion, KDM5 inhibition has potential in the treatment of HER2+ breast cancer and our gene-expression model can be developed into a diagnostic tool for the selection of patients.

Correlation of Platinum Cytotoxicity to Drug-DNA Adduct Levels in a Breast Cancer Cell Line Panel.

Platinum drugs, including carboplatin and oxaliplatin, are commonly used chemotherapy drugs that kill cancer cells by forming toxic drug-DNA adducts. These drugs have a proven, but modest, efficacy against several aggressive subtypes of breast cancer but also cause several side effects that can lead to the cessation of treatment. There is a clinical need to identify patients who will respond to platinum drugs in order to better inform clinical decision making. Diagnostic microdosing involves dosing patients or patient samples with subtherapeutic doses of radiolabeled platinum followed by measurement of platinum-DNA adducts in blood or tumor tissue and may be used to predict patient response. We exposed a panel of six breast cancer cell lines to 14C-labeled carboplatin or oxaliplatin at therapeutic and microdose (1% therapeutic dose) concentrations for a range of exposure lengths and isolated DNA from the cells. The DNA was converted to graphite, and measurement of radiocarbon due to platinum-DNA adduction was quantified via accelerator mass spectrometry (AMS). We observed a linear correlation in adduct levels between the microdose and therapeutic dose, and the level of platinum-DNA adducts corresponded to cell line drug sensitivity for both carboplatin and oxaliplatin. These results showed a clear separation in adduct levels between the sensitive and resistant groups of cell lines that could not be fully explained or predicted by changes in DNA repair rates or mutations in DNA repair genes. Further, we were able to quantitate oxaliplatin-DNA adducts in the blood and tumor tissue of a metastatic breast cancer patient. Together, these data support the use of diagnostic microdosing for predicting patient sensitivity to platinum. Future studies will be aimed at replicating this data in a clinical feasibility trial.

Abstract 1852: Combination of the CDK4/6 inhibitor abemaciclib with xentuzumab, a humanized IGF-1 and IGF-2 ligand co-neutralizing monoclonal antibody, results in synergistic antineoplastic effects in human breast cancer cell lines

Abstract Background: The proliferative and pro-survival signals driven by the insulin-like growth factor (IGF) ligands, IGF-1 and IGF-2, are transmitted through their binding to the IGF-1 receptor (IGF-1R). In addition, IGF-2 promotes proliferation through activation of the insulin receptor variant A (IR-A) that is expressed during embryonic development as well as in many cancers. IGF survival signaling has been implicated in driving resistance to cancer therapies with diverse mechanisms of action, due to cross-talk between cellular signaling networks. Recent studies[1][2] suggest that the combination of IGF-1R signaling inhibitors with CDK4/6 inhibitors can result in enhanced anti-tumor activity. The aim of this study was to explore the potential of the IGF-1/-2 ligand blocking antibody, xentuzumab (BI 836845[3]), to enhance the anti-tumor activity of the CDK4/6 inhibitor abemaciclib, alone or in combination with fulvestrant, in human breast cancer (BC) cell lines. Methods: The anti-proliferative activity of the xentuzumab/abemaciclib combination was evaluated using CellTiter-Glo and propidium iodide staining in a panel of 51 and 20 BC cell lines, respectively. Detailed studies of abemaciclib (+/- fulvestrant), xentuzumab and combinations thereof were performed in MCF7 cells. Cell cycle analysis was done by FACS and BrdU ELISA, cellular signaling was assessed by Western blotting, proliferation was evaluated by Incucyte, CellTiter-Glo and alamarBlue assay. Apoptosis was measured by detection of cleaved PARP and caspase 3. Results: Among a panel of BC cell lines, enhanced anti-proliferative activity of xentuzumab+abemaciclib vs. abemaciclib alone was observed specifically in hormone receptor positive (HR+) cell lines. Combined treatment resulted in more pronounced cell cycle arrest in MCF7 cells, associated with synergistic blockade of IGF survival signaling and suppression of cell cycle genes downstream of CDK4/6. The triple combination with fulvestrant more effectively inhibited tumor cell proliferation than the doublet abemaciclib+fulvestrant, and led to induction of apoptosis. Conclusion: The study results show that addition of the IGF-1/-2 neutralizing antibody xentuzumab to abemaciclib, in the absence or presence of fulvestrant, leads to improved anti-proliferative activity and, in the triple combination, results in cellular death in MCF7 HR+ breast cancer cells. A phase Ib trial evaluating the abemaciclib+xentuzumab combination, including triplets with endocrine therapy in HR+BC patients, is currently ongoing.

PO-502 A potential role for HSP90 in HER2-driven breast cancer (BC)

IntroductionHER2 (amplified in 30% of BC) is involved in the activation of many pathways and its function is regulated by HSP90. Thus, HSP90 co-targeting is emerging as a potential molecular target for HER2-directed BC therapy.Material and methodsWe analysed HER2 and HSP90 expression in a panel of BC cell lines, including MCF7 cells stably transfected with a constitutively active HER2. HER2/HSP90 expression and growth inhibition were monitored over time upon exposure to trastuzumab (T) and docetaxel (D), in the presence or absence of HSP90 silencing. We also retrospectively evaluated a series of 24 locally advanced/operable BC patients (pts) who underwent neoadjuvant T+D for HSP90 expression and correlated it with pathological complete response (pCR).Results and discussionsIn the BC cell lines analysed there was no clear-cut correlation between HSP90 and HER2 expression. HER2 transfection into MCF7 cells increased HSP90 mRNA and protein expression; however, treatment with T further increased HSP90 levels. Conversely D increased HER2, but did not affect HSP90, expression. In HER2 +BC cell lines, simultaneous T+D combination resulted in synergistic growth inhibition in vitro, while their staggered combination, particularly T followed by D, did not afford synergistic effects. Effects of simultaneous and staggered treatments on HSP90 and HER2 expression were analysed by WB: HER2 expression decreased in the simultaneous and staggered combination (D followed by T), while HSP90 expression did not change upon combined treatment. The effects of HSP90 silencing and overexepression on functional response to T+D are being analysed in HER2 +BC models: preliminary results indicate that HSP90 silencing in HER2 +BC decreases the therapeutic synergism of the simultaneous T+D combination. Accordingly, in locally advanced/operable pts undergoing neoadjuvant T+D, pCR occurred more frequently in pts with a baseline HSP90 score of 3+, as compared to 2+and 1+ (50.0% vs. 14.3% vs. none, p=0.05). These results suggest the possibility to classify HER2-positive pts into HSP90 defined subgroups and elaborate specific therapeutic strategies.ConclusionPreclinical data indicate that constitutive HER2 activation induces HSP90 expression and HSP90 modulation influences the functional response to combined treatment. Baseline HSP90 expression may potentially represent a pre-requisite of pharmacological response in HER2-addicted BC.

Abstract 5543: Network guided modeling allows tumor type independent prediction of sensitivity to retinoic acid

Abstract Background: All-trans retinoic acid (ATRA) is a differentiating agent used in the treatment of acute-promyelocytic-leukemia and it is under-exploited in other malignancies despite its low systemic toxicity. A rational/personalized use of ATRA requires development of predictive tools allowing identification of sensitive cancer types and responsive individuals. Materials and Methods: RNA-Sequencing data for 10080 patients and 33 different tumor-types were derived from the TCGA and Leucegene datasets and completely re-processed. The study was performed using machine learning methods and network analysis. Results: We profiled a large panel of breast-cancer cell-lines for in vitro sensitivity to ATRA and exploited the associated basal gene-expression data to initially generate a model predicting ATRA-sensitivity in this disease. Starting from these results and using a network-guided approach, we developed a generalized model (ATRA-21) whose validity extends to tumor-types other than breast cancer. ATRA-21 predictions correlate with experimentally determined sensitivity in a large panel of cell-lines representative of numerous tumor-types. In patients, ATRA-21 correctly identifies APL as the most sensitive acute-myelogenous-leukemia subtype and indicates that uveal-melanoma and low-grade glioma are top-ranking diseases as for average predicted responsiveness to ATRA. There is a consistent number of tumor-types for which higher ATRA-21 predictions are associated with better outcomes. Conclusions: In summary, we generated a tumor-type independent ATRA-sensitivity predictor which consists of a restricted number of genes and has the potential to be applied in the clinics. Identification of the tumor-types which are likely to be generally sensitive to the action of ATRA paves the way to the design of clinical studies in the context of these diseases. In addition, ATRA-21 may represent an important diagnostic tool for the selection of individual patients who may benefit from ATRA-based therapeutic strategies also in tumors characterized by lower average sensitivity. Citation Format: Enrico Garattini, Marco Bolis, Maddalena Fratelli, Mineko Terao. Network guided modeling allows tumor type independent prediction of sensitivity to retinoic acid [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5543. doi:10.1158/1538-7445.AM2017-5543

Effect of surgical wound fluids after intraoperative electron radiotherapy on the cancer stem cell phenotype in a panel of human breast cancer cell lines.

The wound healing process after surgery alters the area surrounding the original tumor and around the scar, and the modified microenvironment is more favorable for tumor recurrence. Intraoperative radiotherapy (IORT) is one of the more novel strategies in breast cancer (BC) treatment. Irradiation during surgery has effects on the tumor microenvironment, abrogating the proliferative cascade induced by surgical wound healing. The aim of the present study was to determine the effect of surgical wound fluids from IOERT treatment (RT-WF) compared with wound fluids from conservative-breast surgery only (WF) on the cancer stem cell phenotype in a panel of BC cell lines. Post-operative wound fluids were derived from patients with BC who underwent a tumor resection (quadrantectomy) plus intraoperative electron radiotherapy using a single dose of ≤10 Gy on the tumor bed and surrounding tissues, or from those who underwent a tumor resection without IOERT. Cell lines were incubated with 10% wound fluids, and after 4 days, the cluster of differentiation (CD)44+/CD24−/low phenotype and aldehyde dehydrogenase 1 (ALDH1) activity were determined by flow cytometry. The two types of fluid each affected the CD44+/CD24−/low phenotype. The results varied markedly between each cell line, even for the same histological subtypes. RT-WF decreased the CD44+/CD24−/low populations in the basal-like BT-549 and MDA-MB-468 cell lines, whereas in the luminal type MCF7 cell line, the two fluids inhibited these populations. The HER-OE subtypes harbored a minimal CD44+/CD24−/low population, but the growth of SK-BR-3 was stimulated by the two post-operative fluids. WF exhibited a stronger effect on ALDH1 activity compared with RT-WF. The stimulatory effect was dependent on the histological subtype of the cell line and the strongest dependence was observed in luminal subtypes characterized by low dehydrogenase activity in the control group. The present results enable a better understanding of the mechanism of recurrence and metastases following BC surgery. With respect to histological phenotype, its effect on tumor progression, either local or systemic, strongly suggests the requirement for further research and clinical validation.

Squalene epoxidase is a bona fide oncogene by amplification with clinical relevance in breast cancer.

SQLE encodes squalene epoxidase, a key enzyme in cholesterol synthesis. SQLE has sporadically been reported among copy-number driven transcripts in multi-omics cancer projects. Yet, its functional relevance has never been subjected to systematic analyses. Here, we assessed the correlation of SQLE copy number (CN) and gene expression (GE) across multiple cancer types, focusing on the clinico-pathological associations in breast cancer (BC). We then investigated whether any biological effect of SQLE inhibition could be observed in BC cell line models. Breast, ovarian, and colorectal cancers showed the highest CN driven GE among 8,783 cases from 22 cancer types, with BC presenting the strongest one. SQLE overexpression was more prevalent in aggressive BC, and was an independent prognostic factor of unfavorable outcome. Through SQLE pharmacological inhibition and silencing in a panel of BC cell lines portraying the diversity of SQLE CN and GE, we demonstrated that SQLE inhibition resulted in a copy-dosage correlated decrease in cell viability, and in a noticeable increase in replication time, only in lines with detectable SQLE transcript. Altogether, our results pinpoint SQLE as a bona fide metabolic oncogene by amplification, and as a therapeutic target in BC. These findings could have implications in other cancer types.

Time-tuning cancer therapy

Time-tuning cancer therapy

Abstract 3813: TRAIL and IAP inhibitor AZD5582 combination treatment induces profound tumor cell death, which is differentially dependent on the mitochondrial apoptotic pathway

Abstract Background It has been suggested that activation of the death receptors may induce selective tumour cell lethality and therefore represent a safe and effective therapeutic approach. However, several recent clinical trials evaluating either recombinant TRAIL or TRAIL receptor agonistic antibodies have shown very limited responses despite favourable safety profiles. This lack of efficacy suggests that combination with other agents will be required to unleash the therapeutic potential of the death receptor pathway. Through a high-throughput combination screen, we identified the combination of TRAIL and an IAP (Inhibitor of Apoptosis Proteins) inhibitor AZD5582 to be highly synergistic in inducing tumour cell death across a number of tumour cell line panels. Since the molecular mechanisms underlying the synergistic activity of combined IAP inhibition and TRAIL remain unclear, we investigated the modes of the death signal transduction and its execution in a panel of breast cancer cell lines. Methods Cell number and viability were assessed using the nuclear staining dye Sytox green. BID, BAX and BAK gene expression was modulated using siRNA, protein expression was evaluated by western blotting. Total caspase activity was inhibited with Q-VD-OPh. Results We observed a diverse sensitivity profile in response to the AZD5582/TRAIL combination in it's ability to enhance cell killing over the single agent across the breast cancer cell line panel. A smaller panel was selected to contain members either resistant or exquisitely sensitive to AZD5582/TRAIL. Analysis of cell death confirmed early induction of apoptosis following treatment in sensitive cell lines. Combination treatment induced both caspase-8 activation and a concomitant apoptotic cell death in sensitive cell lines but we observed neither event in resistant cell lines. Importantly, knockdown of BID demonstrated the requirement of this BH3-only protein in two out of four IAPi/TRAIL sensitive cell lines. Conclusions In this study we investigated the exceptionally synergistic effect of combining TRAIL and the IAP inhibitor AZD5582 in mediating enhanced tumour cell lethality. We have shown that the combination induces both caspase-8 activation and a concomitant apoptotic cell death in sensitive cell lines but not in resistant cell lines upon combination treatment. We also demonstrated that the BID-initiated mitochondrial apoptotic pathway plays an essential role in some cell lines but is dispensable in others. Thus our study provides new insights into the molecular events responsible for the death signal transduction and execution in response to the IAPi/TRAIL combination treatment. Citation Format: Radoslaw Polanski, John Vincent, Urszula Polanska, Eric Tang. TRAIL and IAP inhibitor AZD5582 combination treatment induces profound tumor cell death, which is differentially dependent on the mitochondrial apoptotic pathway. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3813. doi:10.1158/1538-7445.AM2015-3813