HER2 Pathway Research Articles

Abstract A026: An alternative to HER2 IHC 0/1+/2+ status to predict which clinically HER2-negative patients will respond to anti-HER2 therapies: A rationale for the likely superiority of quantitative HER2 pathway RPPA measurements

Abstract Immunohistochemistry (IHC) may not accurately measure HER2 levels and does not reflect HER2 activity/phosphorylation in HER2-negative patients in the HER2 LOW (IHC 1+/2+) and ULTRA-LOW (IHC 0) range [PMID: 35595825). Yet, accurate quantification of HER2 may be key for predicting response to antibody drug conjugates (ADC) such as fam-trastuzumab-deruxtecan-nxki (T-DxD). We showed previously that response to the receptor tyrosine kinase inhibitor (RTKI) neratinib and the ADC ado-trastuzumab emtansine (TDM-1) can be predicted by phospho(p) HER2 Y1248 and pEGFR Y1173, but not total HER2, in TN and HER2+ pts, respectively (PMID: 34741023; 32914002). We now utilize I-SPY2 TRIAL data to explore further relationships between HER2 IHC, Reverse Phase Protein Array (RPPA)-based quantitative HER2 measurement and a HER2 Activation Response Predictive Signature (HARPS) as candidate response predictors for HER2low-targeted agents. Tumors from 395 HER2-negative patients (HR+=200, TN=195) from 8 arms of the I-SPY2 TRIAL had HER2 IHC/FISH data, along with RPPA-based HER2, pHER2 Y1248 and pEGFR Y1173 data from Laser Capture Microdissection (LCM)-enriched tumor epithelium. Of these tumors, 37% (145/395) were HER2 IHC 0, 42% (168/395) were IHC 1+ and 21% (82/395) were IHC 2+. RPPA-based HARPS was categorized as HARPS+ (pHER2-high/pEGFR-high) or HARPS- (pHER2-low and/or pEGFR-low) using previously established combined cut points. Association between quantitative protein values and HER2 IHC was assessed using ANOVA/Tukey tests. Association between endpoint quartiles and IHC was assessed using chi-squared/posthoc tests. RPPA quantitative HER2 total protein levels were associated with HER2 IHC (Tukey p<1E-09), however, the median and ranges of HER2 expression highly overlapped between HER2 IHC 0, 1+ and 2+ (e.g. HER2=0.44 [0.27 - 0.6] in IHC 0 vs 0.69 [0.42-1.0] in IHC 2+). A significant number (34%) of HER2 IHC 0 tumors expressed HER2 above the median level in the HER2 LOW population. While pHER2 and HARPS status were not associated with HER2 IHC class, HARPS associated with total HER2 overall (chi-squared p=8E-05) and in TNBC (chi-squared p=2.4E-06). We found that 42% (81/195) of TNBC were HARPS+, as were 44% (40/89) of HER2 ULTRA-LOW and 40% (41/104) of HER2 LOW tumors. Our results reveal general disconcordance between IHC and RPPA quantitative HER2, with a third of HER2 IHC 0 tumors expressing HER2 and thus, potentially responsive to ADCs such as T-DxD or TDM1. The high proportion of HER2 ULTRA-LOW TNBC tumors classified HARPS+ by our CLIA-based assay identifies tumors predicted to respond to HER2-directed TKI therapies, representing a cohort with actionable HER2 biology missed by IHC. As HER2Low targeted therapies enter ISPY 2.2, we will test the hypothesis that quantitative HER2 is most predictive for HER2 ADCs, and HARPS is most predictive for RTKIs. Citation Format: Julia Wulfkuhle, Denise M. Wolf, Angela DeMichele, Christina Yau, Laura van ‘t Veer, Hope S. Rugo, Lajos Pusztai, Lamorna Brown-Swigart, Gillian L. Hirst, Rosa I. Gallagher, Amy L. Delson, Alexander D. Borowsky, Laura J. Esserman, Paula R. Pohlmann, Emanuel F. Petricoin. An alternative to HER2 IHC 0/1+/2+ status to predict which clinically HER2-negative patients will respond to anti-HER2 therapies: A rationale for the likely superiority of quantitative HER2 pathway RPPA measurements [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr A026.

Endocrine therapy plus HER2-targeted therapy, another favorable option for HR+/HER2+ advanced breast cancer patients.

Advanced breast cancer (ABC) that is positive for hormone receptors (HRs) and human epidermal growth factor receptor 2 (HER2) is a cancer subtype with distinctive characteristics. The primary treatment guidelines suggest that a combination therapy comprising anti-HER2 therapy and chemotherapy should be administered as the initial treatment for HR-positive/ HER2-positive (HR+/HER2+) ABC. However, crosstalk between the HR and HER2 pathways can partially account for the resistance of HR+/HER2+ disease to HER2-targeted therapy. This, in turn, provides a rationale for the concomitant administration of HER2-targeted therapy and endocrine therapy (ET). Many clinical studies have confirmed that the combination of HER2-targeted therapy and ET as a first-line treatment is not inferior to the combination of HER2-targeted therapy and chemotherapy, and support its use as a first-line treatment choice for HR+/HER2+ ABC. Other drugs, such as antibody-drug conjugates, cyclin-dependent kinase 4/6 inhibitors, phosphatidylinositol 3-kinase-protein kinase B (AKT)-mammalian target of rapamycin inhibitors, and programmed cell death protein 1 or programmed cell death ligand 1 inhibitors, may also improve the prognosis of patients with breast cancer by blocking signaling pathways associated with tumor proliferation and break new ground for the treatment of HR+/HER2+ ABC.

Anthocyanin Oligomers Induce Apoptosis and Autophagy by Inhibiting the mTOR Signaling Pathway in Human Breast Cancer Cells.

Anthocyanin oligomers (AOs) are phytochemicals synthesized by fermenting anthocyanins extracted from grape skins and are more biologically active than monomeric anthocyanins. In this study, we evaluate the effects of an AO on triple-negative MDA-MB-231 and HER2-overexpressing SK-BR-3 breast cancer cells. The cell viability of MDA-MB-231 and SK-BR-3 cells was significantly inhibited in a concentration-dependent manner by AO treatment for 24 h, while delphinidin (a monomeric anthocyanin) had no effect on cell viability. In addition, the AO increased H2A.X phosphorylation (a marker of DNA damage), reduced RAD51 (a DNA repair protein) and survivin (a cell survival factor) protein levels, and induced apoptosis by caspase-3-dependent PARP1 cleavage in both cell lines. Surprisingly, the AO induced autophagy by increasing intracellular LC3-II puncta and LC3-II and p62 protein levels. In addition, the AO inhibited the mTOR pathway in MDA-MB-231 and SK-BR-3 cells by suppressing the HER2, EGFR1, and AKT pathways. These results demonstrate that the anti-cancer effect of the AO was due to the induction of apoptosis and autophagy via cleaved caspase-3-mediated PARP1 cleavage and mTOR pathway inhibition, respectively. Furthermore, our results suggest that anthocyanin oligomers could be considered potential candidates for breast cancer treatment.

Immunoexpression of HER2 pathway related markers in HER2 invasive breast carcinomas treated with trastuzumab

PurposeWe evaluated the immunoexpression of potential markers involved in the HER2 pathway in invasive breast carcinoma with HER2 amplification treated with trastuzumab. MethodsSamples of ninety patients diagnosed and treated at two public Brazilian hospitals with overexpressed invasive carcinoma between 2009 and 2018 were included. Several markers (Bcl-2, CDK4, cyclin D1, EGFR, IGF1, IGF-1R, MDM2, MUC4, p16, p21, p27, p53, PTEN, RA, TNFα, and VEGF) were immune analyzed in the tumor by immunohistochemistry and then correlated with clinicopathological variables. ResultsTumor sample expression results determined potential markers of good prognosis with statistically significant values: cyclin D1 with a nuclear grade, and recurrence; IGF-1 with tumor size, and death; p16 with a response after treatment; PTEN with a response after treatment, and death. Markers of poor prognosis: p53 with histological, and nuclear grade; IGF-1R with a compromised lymph node. The treatment resistance rate after trastuzumab was 40%; the overall survival was 4.13 years (95% CI 5.1–12.5) and the disease-free survival was 3.6 years (95% CI 5.1–13.1). ConclusionsThe tumor samples profile demonstrated that cyclin D1, IGF-1, p16, and PTEN presented the potential for a good prognosis and p53 and IGF-1R for worse.

Irreversible HER2 inhibitors overcome resistance to the RSL3 ferroptosis inducer in non-HER2 amplified luminal breast cancer.

Ferroptosis, a form of programed cell death, can be promoted by inhibitors of the xCT transporter (erastin) or GPX4 (RSL3). We found that GPX4, but not the xCT transporter, is selectively elevated in luminal breast cancer. Consistent with this observation, the majority of luminal breast cancer cell lines are exquisitely sensitive to RSL3 with limited sensitivity to erastin. In RSL3-resistant, but not sensitive, luminal breast cancer cell lines, RSL3 induces HER2 pathway activation. Irreversible HER2 inhibitors including neratinib reversed RSL3 resistance in constitutively RSL3-resistant cell lines. Combination treatment with RSL3 and neratinib increases ferroptosis through mitochondrial iron-dependent reactive oxygen species production and lipid peroxidation. RSL3 also activated replication stress and concomitant S phase and G2/M blockade leading to sensitivity to targeting the DNA damage checkpoint. Together, our data support the exploration of RSL3 combined with irreversible HER2 inhibitors in clinical trials.

Antimicrobial, Cytotoxic, and α-Glucosidase Inhibitory Activities of Ethanol Extract and Chemical Constituents Isolated from Homotrigona apicalis Propolis-In Vitro and Molecular Docking Studies.

The chemical investigation of Homotrigona apicalis propolis collected in Binh Dinh province, Vietnam, led to the isolation of nine compounds, including four sesquiterpenes: spathulenol (1), 1αH,5βH-aromandendrane-4β,10α-diol (2), 1β,6α-dihydroxy-4(15)-eudesmene (3), and 1βH,5βH-aromandendrane-4α,10β-diol (4); three triterpenes: acetyl oleanolic acid (5), 3α-hydroxytirucalla-8,24-dien-21-oic acid (6), and ursolic acid (7); and two xanthones: cochinchinone A (8) and α-mangostin (9). Sesquiterpens 1-4 and triterpene 6 were isolated for the first time from stingless bee propolis. Plants in the Cratoxylum and Aglaia genus were suggested as resin sources of the propolis sample. In the antibacterial activity evaluation, the EtOH extract only showed moderate activity on S. aureus, while the isolated compounds 7-9 showed good antibacterial activity, with IC50 values of 0.56 to 17.33 µg/mL. The EtOH extract displayed selective cytotoxicity against the A-549 cancer cell line, with IC50 values of 22.82 ± 0.86 µg/mL, and the xanthones 8 and 9 exhibited good activity against the KB, HepG-2, and A-549 cancer cell lines, with IC50 values ranging from 7.55 ± 0.25 µg/mL to 29.27 ± 2.07 µg/mL. The cytotoxic effects of xanthones 8 and 9 were determined by the inhibition of the EGFR and HER2 pathways using a molecular docking study. Compounds 8 and 9 displayed strong binding affinity with EFGR and HER2, with values of -9.3 to -9.9 kcal/mol. Compounds 5, 8, and 9 showed potential α-glucosidase inhibitory activities, which were further confirmed by computational studies. The binding energies of compounds 5, 8, and 9 were lower than that of arcabose.

Low co-expression of PD-L1 and oncogenic receptor tyrosine kinases HER2 and cMET in urothelial carcinoma is associated with discordant expression between primary and metastatic sites

Novel regimens targeting immune checkpoints and the cMET or HER2 pathways are under investigation in metastatic urothelial carcinoma (mUC) though co-expression of these molecular targets has not been defined. We sought to characterize the protein co-expression rates of PD-L1, cMET and HER2 in primary and metastatic mUC lesions and agreement rates in paired biopsies.We assessed PD-L1, cMET and HER2 protein expression by immunohistochemistry (IHC) in archival mUC samples identified from an institutional database (n = 143). Correlation of expression between primary and metastatic biopsies was performed in patients with available paired biopsies (n = 79). Protein expression levels by predefined thresholds were measured, and Cohen's kappa statistics (κ) were utilized to assess the agreement in expression between paired primary and metastatic samples.In primary tumors (n = 85), high expression of PD-L1, cMET, and HER2 was observed in 14.1%, 34.1%, and 12.9%, respectively. In metastatic samples (n = 143), high expression of PD-L1, cMET and HER2 was detected in 9.8%, 41.3%, and 9.8%, respectively. Expression agreement rates between paired specimens (n = 79) were PD-L1: 79.7% (κ = 0.09), cMET: 69.6% (κ = 0.35), HER2: 84.8% (κ = 0.17). High PD-L1/cMET co-expression was observed in only 5.1% (n = 4) of primary and 4.9% (n = 7) of metastatic specimens. High co-expression of PD-L1/HER2 occurred in 3.8% (n = 3) of primary samples and no metastatic samples. The overall co-expression agreement between paired samples was 55.7% (κ = 0.22) for PD-L1/cMET and 67.1% (κ = 0.06) for PD-L1/HER2, but agreement for high co-expression between paired samples was very low (2.5% for PD-L1/cMET and 0% for PD-L1/HER2).Tumor co-expression of high cMET or HER2 and PD-L1 is low in this cohort. Agreement of high co-expression between primary and metastatic sites is rare. Biomarker-based strategies used in selection of patients for contemporary trials testing combinations of immune checkpoint inhibitors with either cMET or HER2-targeted agents should account for discordant biomarker expression between primary and metastatic sites.

Genomic characterization between HER2-positive and negative gastric cancer patients in a prospective trial.

We aimed to clarify the genomic characteristics of HER2-positive and negative gastric cancer cases that potentially affect tumor progression and treatment response in a prospective trial. We collected 80 formalin-fixed paraffin-embedded (FFPE) samples (49 HER2+ and 31 HER2-) from gastric cancer patients who participated in the TROX-A1 trial (UMIN000036865). We queried a 435-gene panel (CANCERPLEX-JP) to generate comprehensive genomic profiling data, including the tumor mutation burden, somatic mutations, and copy number variations. In addition, the genomic differences between HER2+ and HER2- gastric cancer patients were analyzed. Mutational analyses showed that TP53 was the most frequently mutated gene regardless of HER2 status. ARID1A mutation was significantly enriched in HER2-negative patients. The number of total mutations in HER2-negative patients with ARID1A mutation was remarkably higher than that in HER2-positive patients. Next, copy number variation analyses showed that the number of amplified genes (such as CCNE1, PGAP3, and CDK12) in HER2-positive cases was significantly higher than that in HER2-negative cases. Moreover, PTEN deletion was more common in HER2-positive cases. Finally, we found that, compared with HER2-positive patients, HER2-negative patients tended to have a higher tumor mutation burden, particularly in patients with ARID1A mutation. Pathway analyses of the gene alterations showed an enrichment of several immune-related pathways in HER2-negative patients. According to the genomic profiling of HER2-positive and negative gastric cancer, several gene alterations in the HER2 pathway may be the potential mechanism underlying trastuzumab resistance. Relative to HER2-positive gastric cancer, HER2-negative gastric tumors with ARID1A mutation may be sensitive to immune checkpoint inhibitors.

CRUCUMIN ROLE IN BREAST CANCER TREATMENT

One of the most common forms of malignant tumors is breast cancer worldwide, has a high fatality rate. The development of novel chemicals and technological advancements that will allow the adoption of safer and more efficient therapeutic techniques has received a lot of attention in order to address this problem. In order to maximize tumor growth inhibition and reduce side effects, it has been suggested that combining nanoparticles with well-known anticancer agents including compounds derived from plants, like curcumin is an effective strategy. Curcumin exploits a complex network of molecular signals, including the proliferative, ER, and HER2 pathways, to exert its anticancer actions. According to experimental results, curcumin controls genes associated to cell phase, microRNA, and apoptosis in breast cancer cells.

Afatinib in patients with recurrent/metastatic (RM) squamous cell carcinoma of the head and neck (SCCHN) harboring alterations in the HER pathway: Results of the B1 cohort of the EORTC-HNCG-1559 trial (UPSTREAM).

6034 Background: Afatinib (A) is an irreversible pan-HER inhibitor that improved PFS in second line RM SCCHN after platinum (LUX-H&N1 trial). In a retrospective biomarker analysis, subgroups of pts with p16 negative, PTEN high or EGFR amplification SCCHN seem to benefit the most. Other studies suggest that A has activity in tumors with HER2 gene activation. Methods: The UPSTREAM trial is a biomarker-driven umbrella trial of targeted therapies and immunotherapy for RM SCCHN (post-platinum, ECOG 0-1, measurable disease). The B1 cohort was a phase II, randomized, open-label substudy evaluating the efficacy of afatinib (orally, 40mg/day) vs physician’s choice (ctrl) (2:1 ratio) in pts with p16 negative RM SCCHN harboring one of the following biomarkers (fresh biopsy): EGFR mutation(mut)/amplification(amp) or HER2 mut/amp or PTEN high by immunohistochemistry (IHC, H-score > 150). Only KRAS/ HRAS/ NRAS wild type tumors were included. The primary endpoint was progression-free survival rate (PFSR) at 16 weeks after randomization. A 2-stage Simon optimal design was applied to arm A (H1 40%, H0 20%, 1-sided α 10%, power 90%) with 17 and 20 pts enrolled in the first and second stage respectively. Secondary endpoints included ORR, toxicity, PFS, and OS. Results: 59 RM SCCHN pts were included in the B1 cohort (A: n = 40, ctrl: n = 19). Out of the 59 patients, EGFR amp, HER2 amp and HER2 mut were found in 6 pts (10%), 1 pt (2%) and 1 pt (2%), respectively. PTEN (IHC) was high in 97%. 55 pts were evaluable (A: n = 38, ctrl: n = 17) (median age: 62, oral cavity: 29%, oropharynx: 36%, hypopharynx: 24%, larynx: 11%). 69% of pts had received ≥ 2 lines of systemic treatment for RM disease. 80% were pretreated with cetuximab. In arm A, 13/38 patients were alive and free of objective progression at 16 weeks (34.2%, 1-sided 90%CI, 23.9±inf), meeting the predefined criteria of success. The PFSR at 16W in ctrl arm was 29.4% (5/17). 4 objective responses were observed in arm A (3 PR and 1 CR) (ORR 11%, 95%CI 2.9-24.8%) and 1 PR in ctrl arm (6%). The median duration of response under A was 5.7 mo (range: 3.7-25.9 mo). All responding patients had previously been treated with cetuximab, were PTEN high but none had EGFR or HER2 alterations. The median PFS and OS were 2.2/2.4 mo and 7.2/5.0 mo in the A/ctrl arms, respectively. Grade ≥3 drug-related AEs were reported in 31% in arm A and 12% in ctrl arm. The most frequent drug-related AE with A were diarrhea (67%, G3:8%), rash (41%, G3: 3%), fatigue (31%, no G3) and mucositis (23%, G3: 3%). Conclusions: The B1 substudy met its primary endpoint of PFSR at 16 weeks. Responses were seen in cetuximab pre-treated pts. However, the clinical activity of A in this biomarker-selected population remains limited. Translational research is ongoing to better define potential biomarkers. Clinical trial information: NCT03088059 .

Isoliquiritigenin inhibits circ0030018 to suppress glioma tumorigenesis via the miR-1236/HER2 signaling pathway.

In the central nervous system diseases, glioma is one of the most common malignancies around the world. Despite the recent improvements in therapies for glioma, the prognosis of some high-risk glioma remains poor. In glioma, isoliquiritigenin (ISL) is reported to have antioxidative and antitumor activities. However, the potential mechanisms between ISL and circle RNAs (circRNAs) in the glioma tumorigenesis process have not yet been reported. Here, we treated glioma cells with ISL, and circRNA expression levels were detected. Circ0030018 was found significantly downregulated by ISL. Therefore, we explored circ0030018 expression profiles and functions in glioma, finding that circ0030018 was evidently overexpressed in glioma cell lines. Colony formation, CCK-8, and transwell assay made clear that circ0030018 silencing dramatically cut down glioma growth and invasion. Moreover, ROS level was detected to find that circ0030018 silence remarkably enhanced cell oxidative stress in glioma. Mechanism studies were conducted to investigate the underlying basis of circ0030018 function in glioma, unveiling that circ0030018 realized its functions partially through the miR-1236/HER2 signaling in glioma. In conclusion, our study investigated the roles and mechanisms of the ISL on the circ0030018/miR-1236/HER2 pathway in glioma tumorigenesis and progression. Circ0030018 could act as the prospective biologic signature or therapeutic target for glioma.

Abstract 3636: Liver endothelium secreted LRG1 promotes metastatic colorectal cancer growth through the HER3/RSK/EIF4B AXIS

Abstract Background: 25% of patients diagnosed with colorectal cancer (CRC) have liver metastasis at presentation, and ~80% of all metastatic CRC are developed in the liver. We previously reported that liver endothelial cells (ECs), a key component of the liver microenvironment, secrete LRG1 to promote CRC growth via activating human epidermal growth factor receptor (ERbB3, also known as HER3). However, we found that LRG1-induced HER3 activation is distinct from the canonical neuregulin 1 (NRG1)-induced HER3 pathway. The present study further validated LRG1 as a new HER3 ligand for promoting mCRC growth and elucidated the novel downstream signaling pathway induced by LRG1-HER3. Methods: We first measured the binding affinity between HER3 and LRG1 by Biolayer interferometry (BLI). We then used in vitro and in vivo xenograft approaches to determine the effect of LRG1 monoclonal antibody (15C4) on HER3 activation and CRC growth. To further determine the role of LRG1 in promoting CRC growth in the liver, we used murine CRC cells in a syngeneic orthotropic liver injection model to establish CRC allografts in the liver of LRG1−/− mice with systemic LRG1 knockout and wild-type siblings (LRG1+/+). We also performed unbiased phospho-MS analysis and subsequent validations to determine the downstream signaling pathway activated by LRG1-HER3. Results: We identified that LRG1 binds to HER3 with the affinity at ~100nM. The LRG1 antibody 15C4 completely attenuated LRG1-induced HER3 activation and in vitro and xenograft growth in vivo. Moreover, LRG1−/− mice with CRC allografts in the liver had 2 times longer overall survival than tumor-bearing LRG1+/+ mice. Lastly, unbiased -omics analysis identified eIF4-protein synthesis is significantly activated by LRG1. With target-specific inhibitors, we further determined that LRG1-HER3 activates the PI3K-PDK1-RSK1/3-eIF4 axis independent of AKT. Conclusions: We identified LRG1 as a novel HER3 ligand and demonstrated that the liver microenvironment-derived LRG1 plays a key oncogenic role in mCRC, by activating a novel RSK-eIF4 survival pathway. Our findings highlighted the potential of blocking LRG1-HER3 and involved downstream pathways for treating patients with mCRC. Citation Format: Moeez Ghani Rathore, Michelle Wright, Wei Huang, Derek Taylor, Yamu Li, Jordan Winter, Zhenghe Wang, John Greenwood, Stephen Moss, Rui Wang. Liver endothelium secreted LRG1 promotes metastatic colorectal cancer growth through the HER3/RSK/EIF4B AXIS. [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 3636.

Abstract P2-04-01: Immunoexpression of markers related to the HER2 pathway in cases of pure positive her2 breast carcinoma treated with trastuzumab

Abstract Introduction: Breast cancer is a heterogeneous disease with well-defined molecular subtypes and variable clinical behavior. The overexpressed HER2 subtype represents approximately 20% of all breast carcinomas. It is associated with a poor prognosis, increased risk of systemic and brain metastases, and poor overall survival until the advent of anti-HER2 therapies, such as trastuzumab. Its introduction into clinical practice has improved the prognosis in cases of breast cancer with overexpressing of pure HER2. However, some cases develop resistance to this drug. Objectives: To evaluate immunoexpression of possible markers involved in the HER2 pathway in breast carcinoma with overexpressing of pure HER2 treated with trastuzumab. Methods: We included 90 patients diagnosed with pure positive HER2 breast carcinoma treated with trastuzumab at the IBCC and HSP/Unifesp public hospitals between 2009 and 2018. Through immunohistochemistry, markers involved in the HER2 pathway (MUC4, IGF-1, IGF-1R, EGFR, p21, p27, p53, p16, cyclin D1, PTEN, CDK4, Bcl-2, VEGF, AR, MDM2, and TNFα) were analyzed samples paraffin-embedded of tumor and compromised lymph nodes and then, correlated with clinicopathological variables. The statistics were performed using the SPSS® software, version 25, from the company IBM, values equal to or less than 0.05 were considered significant (p ≤0.05). To verify possible associations between the clinical-pathological variables and the analyzed markers, Pearson’s X2 test, and Fisher’s exact test were used; for survival analysis, the Kaplan-Meier method was used. Results: Treatment resistance of pure HER2-positive breast cancer cases after trastuzumab treatment was 40%; the OS of this series was 4.13 years (95% CI 5.1 - 12.5) and the DFS was 3.6 years (95% CI 5.1 - 13.1). In the tumor samples it was possible to determine potential markers of good prognosis: cyclin D1 with nuclear grade (p=0.049) and recurrence (p=0.038); IGF-1 with tumor size (p= 0.015) and death (p= 0.046); p16 with response to treatment (p= 0.016); PTEN with response to treatment (p= 0.050) and death (p= 0.030). The results also showed possible markers of poor prognosis such as p53 with SBR GH (p= 0.003) and GN (p= 0.048); and IGF-1R with compromised lymph node (p=0.016). In compromised lymph nodes samples, the correlations showed TNFα with tumor size (p=0.043); and CDK4 with the response to treatment (p=0.011) as possible markers of good prognosis; only p53 with GH SBR grade (p= 0.045) maintained its potential for poor prognosis. Conclusions: In tumor samples, it was possible to demonstrate that the markers: cyclin D1, IGF-1, p16, and PTEN had the potential for a good prognosis panel and p53 and IGF-1R for worse. In samples of compromised lymph nodes, p53 remained as a marker of poor prognosis, while TNFα and CDK4 of good prognosis. Citation Format: Andreia Fabiana V. Franco, Angela Flavia L. Waitzberg, Joaquim T. Araujo Neto, Fatima S. Pasini. Immunoexpression of markers related to the HER2 pathway in cases of pure positive her2 breast carcinoma treated with trastuzumab [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 P2-04-01.

Abstract P6-12-09: Retinoic acid receptor (RAR) signalling plays a role in neratinib (NER) resistance in HER2+ breast cancer (BC) cell lines

Abstract Introduction: NER is a pan-HER tyrosine kinase inhibitor (TKI) approved for the treatment of HER2+ BC in the adjuvant setting following trastuzumab and in combination with capecitabine for advanced disease. Resistance to small molecule TKIs like NER can develop in the clinic. Pre-clinical studies have highlighted that retinoic acid can inhibit BC growth and modulate HER2 signalling pathways. The RAR family of nuclear transcription factors consists of RARα, RARβ and RARγ. The synthetic retinoic acid fenretinide (FN) acts as a pan-RAR agonist, while AGN194310 (AG) acts as a pan-RAR antagonist. In order to investigate the anti-proliferative potential of co-targeting RAR and HER2 pathways in sensitive and resistant BC cell line models, we examined the effect of FN and AG in combination with NER in two HER2+, estrogen receptor-negative, trastuzumab-resistant cell lines HCC1569 and HCC1954, and their NER-resistant (NR) sub-lines HCC1569-NR and HCC1954-NR. Methods: HCC1569 and HCC1954 cell lines were cultured in RPMI/10% FCS at 370C/5% CO2. NR cell lines were generated by continuous exposure to 150nM NER for 6 months. 10 mM stock solutions of FN (H7779-Sigma), AG (SML2665-Sigma) and NER (supplied by Puma Biotechnology, Inc) were made in DMSO. Proliferation was measured as percentage growth versus DMSO control using an acid phosphatase based assay after 5 days drug exposure. The half-maximal inhibitory concentration (IC50) was calculated for each drug using CalcuSyn. The combination assays were performed using fixed ratios. The combination index (CI) values were calculated at the effective dose that inhibits 50% growth (ED50) using CalcuSyn. Values < 1 represent a synergistic effect, a value of 1 is additive and values > 1 represent an antagonistic effect. All data presented as the mean of biological triplicate experiments ± standard deviation. Results: This research found that the NR cell lines were >10-fold resistant to NER (HCC1569-NR IC50 0.44 ± 0.1 μM, HCC1954-NR IC50 0.198 ± 0.019 μM) compared to the parental HCC1569 (IC50 0.018 ± 0.015 μM) and HCC1954 (IC50 0.017 ± 0.001 μM) cell lines. Pan-RAR agonism by FN had a potent anti-proliferative effect in the HCC1569 (FN IC50 0.22 ± 0.02 μM) and the HCC1569-NR cell lines (FN IC50 0.28 ± 0.13 μM), with the HCC1954 and HCC1954-NR cell lines proving less sensitive (IC50 6.47 ± 1.3 μM and 1.9 ± 0.2 μM, respectively). When combined with NER, FN produced a strong antagonistic effect in the HCC1569 cell line (CI value: 15.63 ± 9.5) and a strong synergistic effect in the HCC1954 cell line (CI value: 0.42 ± 0.06). For the NR cell line models, the NER/FN combination proved synergistic (HCC1569-NR, CI value: 0.84 ± 0.46) or additive (HCC1954-NR, CI value: 0.97 ± 0.15). Next, we wanted to assess the impact of antagonising rather than activating RAR activity in our cell line models. All four cell lines were less sensitive to antagonist AG (IC50 >8μM for all cell lines) compared to FN. The addition of AG to NER resulted in responses diametrically opposed to the FN/NER combination. The AG/NER combination produced a strong synergistic effect in the HCC1569 cell line (CI value: 0.52 ± 0.17), an antagonistic effect in the HCC1954 cell line (CI value: 2.1 ± 0.4) and an antagonistic effect in both NR cell lines (HCC1954-NR, CI value: 2.69 ± 0.6 and HCC1569-NR, CI value: 1.58 ± 0.12). Conclusions: This pre-clinical study suggests involvement of the RAR signalling pathway in response to NER and the development of NR. Results also suggest pan-RAR agonism, rather than pan-RAR antagonism, as a potential therapeutic strategy to overcome NR. Further investigation is warranted to determine how targeting the RAR signalling pathway may assist in the treatment of HER2+ BC. Citation Format: Debbie O’Reilly, Lisa D. Eli, Alvin Wong, John Crown, Denis M. Collins. Retinoic acid receptor (RAR) signalling plays a role in neratinib (NER) resistance in HER2+ breast cancer (BC) cell lines [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 P6-12-09.

Abstract P1-13-17: Hyperactivation of the EGFR pathway is associated with resistance to tucatinib in HER2-positive breast cancer models

Abstract Background: The HER2-specific tyrosine kinase inhibitor (TKI) tucatinib (Tuca) recently approved for advanced HER2+ breast cancer is making a move towards the early setting. Given its growing use, resistance is inevitable, as observed in the HER2CLIMB study, where only one patient with brain metastasis remained progression free after 2 years on Tuca. Driven by the prevailing lack of knowledge about the mechanisms of resistance, in this study, we sought to define these mechanisms and identify treatment strategies to overcome them. We previously reported (SABCS 2021) that our BT474 TucaR models acquired EGFR amplification and showed elevated levels of phosphorylated (p) and total (t) EGFR, pHER2, pHER3, and downstream pAKT and pS6. Since the HER pathway is activated by ligands, here we aim to assess if hyperactivation of EGFR via high levels of its ligands is an alternative mechanism of Tuca resistance. Materials and Methods: Our recently developed HER2+ BT474 (ATCC and AZ) cell models with acquired resistance to Tuca (TucaR) developed through long-term exposure to gradually increasing doses of Tuca and their naïve parental (P) were used. Genomic (DNA-seq), transcriptomic (RNA-seq), and proteomic (western blot) characterization were performed. Changes in cell growth and migration were assessed by methylene blue and Incucyte wound healing assays, respectively. Results: RNA-seq analysis demonstrated that the levels of TGFα was significantly higher in our BT474 TucaR models compared to P cells. Our results now demonstrate that exogenous supplementation of EGF to BT474-P cells rescues the Tuca-mediated inhibition of pEGFR, pHER2, and the downstream pAKT, pERK, and pS6 levels. Exogenous EGF was also found to reduce the levels of apoptosis, as assessed by cleaved PARP, mitigating the Tuca-induced cell death. Exogenous EGF or TGFα rendered naïve BT474 and SKBR3 cells resistant to Tuca while neratinib, a pan-HER TKI, effectively inhibited this ligand-driven cell growth. We previously showed that the HER signaling reactivation observed in our EGFR-amplified TucaR cells was inhibited by the EGFR-specific TKI gefitinib (Gef) (SABCS 2021) and that the TucaR cells displayed enhanced migratory capabilities (AACR 2022). Here, we demonstrate that in addition to curbing the growth of TucaR cells, Gef, either alone or together with Tuca, also markedly reverts the migration of the TucaR cells. Knockdown (KD) of EGFR but not HER2 selectively and substantially inhibited the migration of the TucaR cells. KD of EGFR also had a marked cell killing effect on only the TucaR cells, whereas HER2 KD inhibited the growth of P but not TucaR cells. Our findings are consistent with the notion that while the P cells are functionally dependent on HER2, in TucaR cells the survival dependence could be rewired to rely primarily on the hyperactive EGFR signaling. Genomic analysis further revealed that in addition to EGFR amplification, the AZ TucaR cells also acquired a gain of YES1, a src family receptor tyrosine kinase implicated in cancer cell growth, invasion, and metastasis. Functional studies using 2 siRNAs, however, showed that YES1 KD had no effect on the growth of TucaR cells, and the migration of both TucaR and P cells was equally affected by YES1 KD, precluding the potential role of YES1 in driving the resistant and enhanced migratory phenotypes. Conclusions: Hyperactivation of the EGFR pathway via amplification of EGFR or increased expression of its ligands confers resistance to Tuca, which may be overcome using dual/pan-HER TKIs or the combination of potent EGFR and HER2 inhibitors. Given the rapidly evolving treatment landscape of HER2+ breast cancer and biomarkers of resistance, our novel findings have potentially crucial therapeutic implications and suggest that rationally sequencing the currently available TKIs may be clinically important. Citation Format: Fu-Tien Liao, Tia Gordon, Chia Chia Liu, Pier Selenica, Yingjie Zhu, Juber Patel, Sarmistha Nanda, Lanfang Qin, Xiaoyong Fu, Andrea Gazzo, Antonio Marra, Juan Blanco-Heredia, Britta Weigelt, Jorge Reis-Filho, C. Kent Osborne, Mothaffar Rimawi, Rachel Schiff, Jamunarani Veeraraghavan. Hyperactivation of the EGFR pathway is associated with resistance to tucatinib in HER2-positive breast cancer models [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 P1-13-17.

Abstract P3-07-16: Pre-clinical study of amcenestrant and HER2-targeted therapies in HER2+/ER+ breast cancer cell line models

Abstract Background: Up to 70% of HER2 over-expressing (HER2+) breast cancers also express estrogen receptor (ER). Dual targeting of HER2 and ER has shown pre-clinical and clinical benefit in HER2+/ER+ breast cancer. Rationale for these combinations is based on circumvention of resistance mediated by crosstalk between HER2 and ER signalling pathways. Fulvestrant is the only selective estrogen receptor degrader (SERD) approved by the FDA for the treatment of ER+ breast cancer. Development of alternative orally available SERDs with improved bioavailability, such as amcenestrant, is underway. The HER2-targeted tyrosine kinase inhibitors (TKIs) lapatinib, neratinib and tucatinib and the antibody drug conjugate T-DM1 are approved for the treatment of HER2+ breast cancer. This pre-clinical study aims to investigate the potential of combining the oral SERD amcenestrant with HER2-targeted therapies for the treatment of HER2+/ER+ breast cancer through identification of synergistic combinations. Methods: ER and HER2 expression levels were assessed in the HER2+/ER+ BT-474 and MDA-MB-361 cell lines by western blot. 5-day acid phosphatase-based assays were used to assess cell viability following treatment with neratinib, lapatinib, tucatinib, and T-DM1; alone and in combination with amcenestrant. All TKIs were commercially sourced, T-DM1 was obtained from Saint Vincent’s University Hospital. Amcenestrant was supplied by Sanofi. IC50 values were determined using Calcusyn, while matrix combination assays of the HER2-targeted therapies combined with amcenestrant were analysed using Combenefit software employing the Loewe model (LM) to determine synergy (Score > 0) or antagonism (Score < 0). All data are the result of a minimum of three independent experiments. Results: HER2 and ER expression was confirmed in the MDA-MB-361 and BT-474 cell lines. MDA-MB-361 cells express higher levels of ER and lower levels of HER2 and phosphorylated HER2 than BT474 cells. MDA-MB-361 exhibited a higher sensitivity to 1 µM amcenestrant alone (% cell viability = 53.3 ± 2.3 %) than the BT-474 (% viability = 85.3 ± 5%). A comparison of IC50 values for each TKI alone or in combination with 1 µM amcenestrant showed amcenestrant significantly lowered the IC50 values for neratinib and tucatinib in BT-474, and all three TKIs in MDA-MB-361 (Table 1). In matrix combination assays, all TKIs exhibited synergistic combinations, with the combination of neratinib and amcenestrant demonstrating the highest synergy values in MDA-MB-361 (LM max value = 25 ± 7) and in BT-474 (LM max value = 19 ± 7). The combination of amcenestrant and T-DM1 displayed additivity (LM value = 0) rather than synergy in the BT-474 cell line, likely due to the high potency of T-DM1 as a single agent. Conclusions: The combination of amcenestrant and HER2-targeting therapies such as neratinib shows potential as a dual-target therapeutic strategy for the treatment of HER2+/ER+ breast cancer and warrants further investigation. Table 1. IC50 values for TKIs alone and with the addition of 1 µM amcenestrant. Significance of chance in IC50 point calculated by Student’s T test, ns = p > 0.05, * = p < 0.05, ** = p < 0.01, SD = standard deviation Citation Format: Amira F. Mahdi, Niall Ashfield, Neil T. Conlon, John Crown, Denis M. Collins. Pre-clinical study of amcenestrant and HER2-targeted therapies in HER2+/ER+ breast cancer cell line models [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 P3-07-16.

Co-expression of PD-L1 and oncogenic receptor tyrosine kinases HER2 and cMET is low in metastatic urothelial carcinoma.

533 Background: Activation of HER2 and cMET signaling has been implicated in the pathogenesis of urothelial carcinoma subsets, and the use of anti-PD-(L)1 agents is well established in this disease. Novel therapeutic combinations targeting both immune checkpoints and the cMET or HER2 pathways are currently under investigation in metastatic urothelial carcinoma (mUC). Co-expression of these molecular targets has not been characterized in mUC. We hypothesized that the rate of PD-L1 co-expression with cMET and HER2 may be low. Therefore, we sought to define tumor protein co-expression of PD-L1, HER2 and cMET in a cohort of mUC patients. Methods: Patients with mUC were identified from an institutional database. FFPE tumor specimens from metastatic sites and available paired primary tumors underwent immunohistochemical staining for PD-L1 (SP-142), cMET, and HER2 expression. High expression was defined using the following thresholds: PD-L1: >=5% of infiltrated immune cells; cMET: >=50% of tumor cells; HER2: score=3+ (complete membrane staining that is intense and >10% of tumor cells). Simple and Weighted Cohen’s kappa Statistics (κ) were utilized to assess the agreement in expression and co-expression between paired primary and metastatic samples. Cohen’s interpretation of the κ results is provided. Results: Specimens from 143 mUC patients were analyzed, including 79 with available paired primary tumors. In primary tumors (N=79), high expression of PD-L1, cMET, and HER2 was observed in 15.2%, 34.2%, and 12.7%, respectively. In metastatic samples (N=143), high expression of PD-L1, cMET and HER2 was detected in 9.8%, 41.3%, and 9.8%, respectively. Expression agreement rates between primary and metastatic specimens (n=79) were PD-L1: 79.7% (κ=0.09, slight agreement), cMET: 69.6% (κ=0.35, fair agreement), HER2: 84.8% (κ=0.17, slight agreement) and were driven by high prevalence of low expression. High PD-L1/cMET co-expression was observed in only 5.1% (n = 4) of primary and 4.9% (n =7) of metastatic specimens. High co-expression of PD-L1/HER2 occurred in only 3.8% (n=3) of primary samples and in no metastatic samples. The overall co-expression agreement rate between paired primary and metastatic samples was 55.7% (κ = 0.22, fair agreement) for PD-L1/cMET and 67.1% (κ = 0.06, slight agreement) for PD-L1/HER2. Importantly, however, agreements rates for high co-expression between primary and metastatic samples were very low (2.5% for PD-L1/cMET and 0% for PD-L1/HER2). Conclusions: Tumor co-expression of high cMET or HER2 and PD-L1 is low in this cohort of metastatic urothelial carcinoma patients. Furthermore, agreement of high co-expression between primary and metastatic sites is rare. These results suggest that investigational strategies combining immune checkpoint inhibition with either cMET or HER2 targeted agents in mUC may have limited synergistic activity.

Comprehensive biomarker analysis of long-term response to trastuzumab in patients with HER2-positive advanced gastric or gastroesophageal adenocarcinoma

BackgroundA subgroup of patients with HER2-positive metastatic gastric and gastroesophageal junction cancers shows long-term response under trastuzumab maintenance monotherapy. Obviously, HER2 status alone is not able to identify these patients. We performed this study to identify potential new prognostic biomarkers for this long-term responding patient group. Patients and methodsTumour samples of 19 patients with HER2-positive metastatic gastric and gastroesophageal junction cancer who underwent trastuzumab treatment were retrospectively collected from multiple centres. Patients were divided into long-term responding (n = 7) or short-term responding group (n = 12) according to progression-free survival (PFS≥12 months vs. PFS < 12 months). Next-generation sequencing and microarray-based gene expression analysis were performed along with HER2 and PD-L1 immunohistochemistry. ResultsLong-term responding patients had significantly higher PD-L1 combined positive scores (CPS) and CPS correlated with longer progression-free survival. PD-L1 positivity (CPS ≥ 1) was further associated with an increased CD4+ memory T-cell score. The ERBB2 copy number as well as the tumour mutational burden could not discriminate between short-term and long-term responding patients. Genetic alterations and coamplifications in HER2 pathway associated genes such as EGFR, which were connected to trastuzumab resistance, were present in 10% of the patients and equally distributed between the groups. ConclusionThe study highlights the clinical relevance of PD-L1 testing also in the context of trastuzumab treatment and offers a biological rational by demonstrating elevated CD4+ memory T-cells scores in the PD-L1-positive group.

PAQR8 promotes breast cancer recurrence and confers resistance to multiple therapies

BackgroundBreast cancer mortality is principally due to recurrent disease that becomes resistant to therapy. We recently identified copy number (CN) gain of the putative membrane progesterone receptor PAQR8 as one of four focal CN alterations that preferentially occurred in recurrent metastatic tumors compared to primary tumors in breast cancer patients. Whether PAQR8 plays a functional role in cancer is unknown. Notably, PAQR8 CN gain in recurrent tumors was mutually exclusive with activating ESR1 mutations in patients treated with anti-estrogen therapies and occurred in > 50% of both patients treated with anti-estrogen therapies and those treated with chemotherapy or anti-Her2 agents.MethodsWe used orthotopic mouse models to determine whether PAQR8 overexpression or deletion alters breast cancer dormancy or recurrence following therapy. In vitro studies, including assays for colony formation, cell viability, and relative cell fitness, were employed to identify effects of PAQR8 in the context of therapy. Cell survival and proliferation were quantified by immunofluorescence staining for markers of apoptosis and proliferation. Sphingolipids were quantified by liquid chromatography-high resolution mass spectrometry.ResultsWe show that PAQR8 is necessary and sufficient for efficient mammary tumor recurrence in mice, spontaneously upregulated and CN gained in recurrent tumors that arise following therapy in multiple mouse models, and associated with poor survival following recurrence as well as poor overall survival in breast cancer patients. PAQR8 promoted resistance to therapy by enhancing tumor cell survival following estrogen receptor pathway inhibition by fulvestrant or estrogen deprivation, Her2 pathway blockade by lapatinib or Her2 downregulation, and treatment with chemotherapeutic agents. Pro-survival effects of PAQR8 were mediated by a Gi protein-dependent reduction in cAMP levels, did not require progesterone, and involved a PAQR8-dependent decrease in ceramide levels and increase in sphingosine-1-phosphate levels, suggesting that PAQR8 may possess ceramidase activity.ConclusionsOur data provide in vivo evidence that PAQR8 plays a functional role in cancer, implicate PAQR8, cAMP, and ceramide metabolism in breast cancer recurrence, and identify a novel mechanism that may commonly contribute to the acquisition of treatment resistance in breast cancer patients.

Retraction Note: PlncRNA-1 induces apoptosis through the Her-2 pathway in prostate cancer cells.

Retraction to: Asian Journal of Andrology 2017; 19 (4): 453–57. Doi: 10.4103/1008-682X.178849. During our recent follow-up study, we found that the previous results could not be reproduced. In Figure 2f and 3f, Her-2 and CyclinD1 expression was not repeated by western blotting in RWPE-1 cells. We are therefore retracting our initial article to maintain the integrity of the scientific record. All authors have approved this retraction. We deeply apologize for any confusion it may have caused.