Interactions between BRD4S, LOXL2, and MED1 drive cell cycle transcription in triple-negative breast cancer

Triple-negative breast cancer (TNBC) often develops resistance to single-agent treatment, which can be circumvented using targeted combinatorial approaches. Here, we demonstrate that the simultaneous inhibition of LOXL2 and BRD4 synergistically limits TNBC proliferation in vitro and in vivo. Mechanistically, LOXL2 interacts in the nucleus with the short isoform of BRD4 (BRD4S), MED1, and the cell cycle transcriptional regulator B-MyB. These interactions sustain the formation of BRD4 and MED1 nuclear transcriptional foci and control cell cycle progression at the gene expression level. The pharmacological co-inhibition of LOXL2 and BRD4 reduces BRD4 nuclear foci, BRD4-MED1 colocalization, and the transcription of cell cycle genes, thus suppressing TNBC cell proliferation. Targeting the interaction between BRD4S and LOXL2 could be a starting point for the development of new anticancer strategies for the treatment of TNBC.

Early-Stage Breast Cancer Detection in Breast Milk

Breast cancer occurring during pregnancy (PrBC) and postpartum (PPBC) is usually diagnosed at more advanced stages compared with other breast cancer, worsening its prognosis. PPBC is particularly aggressive, with increased metastatic risk and mortality. Thus, effective screening methods to detect early PrBC and PPBC are needed. We report for the first time that cell-free tumor DNA (ctDNA) is present in breast milk (BM) collected from patients with breast cancer. Analysis of ctDNA from BM detects tumor variants in 87% of the cases by droplet digital PCR, while variants remain undetected in 92% of matched plasma samples. Retrospective next-generation sequencing analysis in BM ctDNA recapitulates tumor variants, with an overall clinical sensitivity of 71.4% and specificity of 100%. In two cases, ctDNA was detectable in BM collected 18 and 6 months prior to standard diagnosis. Our results open up the potential use of BM as a new source for liquid biopsy for PPBC detection.

SIGNIFICANCE

For the first time, we show that BM obtained from patients with breast cancer carries ctDNA, surpassing plasma-based liquid biopsy for detection and molecular profiling of early-stage breast cancer, even prior to diagnosis by image. See related commentary by Cunningham and Turner, p. 2125. This article is featured in Selected Articles from This Issue, p. 2109.

Antitumor activity of the PI3K δ-sparing inhibitor MEN1611 in PIK3CA mutated, trastuzumab-resistant HER2 + breast cancer

PURPOSE

Dysregulation of the PI3K pathway is one of the most common events in breast cancer. Here we investigate the activity of the PI3K inhibitor MEN1611 at both molecular and phenotypic levels by dissecting and comparing its profile and efficacy in HER2 + breast cancer models with other PI3K inhibitors.

METHODS

Models with different genetic backgrounds were used to investigate the pharmacological profile of MEN1611 against other PI3K inhibitors. In vitro studies evaluated cell viability, PI3K signaling, and cell death upon treatment with MEN1611. In vivo efficacy of the compound was investigated in cell line- and patient-derived xenografts models.

RESULTS

Consistent with its biochemical selectivity, MEN1611 demonstrated lower cytotoxic activity in a p110δ-driven cellular model when compared to taselisib, and higher cytotoxic activity in the p110β-driven cellular model when compared to alpelisib. Moreover, MEN1611 selectively decreased the p110α protein levels in PIK3CA mutated breast cancer cells in a concentration- and proteasome-dependent manner. In vivo, MEN1611 monotherapy showed significant and durable antitumor activity in several trastuzumab-resistant PIK3CA-mutant HER2 + PDX models. The combination of trastuzumab and MEN1611 significantly improved the efficacy compared to single agent treatment.

CONCLUSIONS

The profile of MEN1611 and its antitumoral activity suggest an improved profile as compared to pan-inhibitors, which are limited by a less than ideal safety profile, and isoform selective molecules, which may potentially promote development of resistance mechanisms. The compelling antitumor activity in combination with trastuzumab in HER2 + trastuzumab-resistant, PIK3CA mutated breast cancer models is at the basis of the ongoing B-Precise clinical trial (NCT03767335).

Abstract P1-05-14: ctDNA IN BREAST MILK FOR EARLY DETECTION OF PREGNANCY ASSOCIATED BREAST CANCER

The potential of cell-free tumor DNA (ctDNA) for early tumor detection in asymptomatic patients is yet to be established. In the case of pregnancy associated breast cancer (BC), early detection is of special interest, since it is an entity of special aggressiveness due to a delay in diagnosis, along with the negative effect of mammary gland involution when BC is diagnosed during the postpartum period (PPBC). Indeed, PPBC has double metastatic risk and worst prognosis. With a potential applicability for cancer screening during breastfeeding, here we explored the presence of ctDNA in breast milk (BM) from women with BC associated to pregnancy. Matched samples from breast tumor, plasma and BM from a cohort of 14 women diagnosed during pregnancy or breastfeeding were analysed by droplet digital PCR and a targeted next generation sequencing panel (NGS). Thirteen patients had early-stage disease (11% Stage I, 61% Stage II and 28% Stage III) whilst one was diagnosed at advanced stage. BM harboured ctDNA, since mutations present in the tumor tissue were detected in 86% of the cases by ddPCR and in 71,4% by NGS (difference owing to technique sensitivity). Matched plasma samples had detectable ctDNA levels in only 8% of the cases. In one of the patients, a BM sample collected 18 months prior to BC diagnosis revealed the presence of a pathogenic PIK3CA mutation later detected in the surgically removed tumor. With the ultimate goal of applying the NGS in BM as a technique for early detection of BC in the postpartum period, we have collected samples from healthy volunteers and patients at high risk of developing BC (defined as women becoming pregnant at >40 years or carriers of germ-line pathogenic variants associated with BC -ie: BRCA1, BRCA2, PALB2, RAD51C/D). The application of NGS in BM as a technique for early detection of BC in the postpartum period, identified in a high-risk woman (criteria of enrolment was the age, 46yo) an AKT1 pathogenic mutation in the right-sided BM anticipating by 6 months the radiological diagnosis of a Luminal A tumor, stage pT1bN0M0. In summary, our data provides evidence that ctDNA in BM is highly prevalent even at initial tumor stages, and could be exploited for early breast cancer screening during breastfeeding.

Citation Format: Cristina Saura, Carolina Ortiz, Enrique Javier Arenas, Judit Matito, Anna Suñol-Camas, Octavi Cordoba, Alex Martinez-Sabadell, Itziar Garcia-Ruiz, Ignacio Miranda, Clara Morales-Comas, Estela Carrasco Lopez, Cristina Viaplana, Vicente Peg, Paolo Nuciforo, Neus Bayo, Josep Maria Miquel, Marina Gomez-Rey, Guillermo Villacampa, Silvia Arevalo, Javier Carmona, Martín Espinosa-Bravo, Judith Balmaña, Rodrigo Dienstmann, Joaquin Arribas, Josep Tabernero, miriam sanso, Ana Vivancos. ctDNA IN BREAST MILK FOR EARLY DETECTION OF PREGNANCY ASSOCIATED BREAST CANCER [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 P1-05-14.

Identification of a Molecularly-Defined Subset of Breast and Ovarian Cancer Models that Respond to WEE1 or ATR Inhibition, Overcoming PARP Inhibitor Resistance

PURPOSE

PARP inhibitors (PARPi) induce synthetic lethality in homologous recombination repair (HRR)-deficient tumors and are used to treat breast, ovarian, pancreatic, and prostate cancers. Multiple PARPi resistance mechanisms exist, most resulting in restoration of HRR and protection of stalled replication forks. ATR inhibition was highlighted as a unique approach to reverse both aspects of resistance. Recently, however, a PARPi/WEE1 inhibitor (WEE1i) combination demonstrated enhanced antitumor activity associated with the induction of replication stress, suggesting another approach to tackling PARPi resistance.

EXPERIMENTAL DESIGN

We analyzed breast and ovarian patient-derived xenoimplant models resistant to PARPi to quantify WEE1i and ATR inhibitor (ATRi) responses as single agents and in combination with PARPi. Biomarker analysis was conducted at the genetic and protein level. Metabolite analysis by mass spectrometry and nucleoside rescue experiments ex vivo were also conducted in patient-derived models.

RESULTS

Although WEE1i response was linked to markers of replication stress, including STK11/RB1 and phospho-RPA, ATRi response associated with ATM mutation. When combined with olaparib, WEE1i could be differentiated from the ATRi/olaparib combination, providing distinct therapeutic strategies to overcome PARPi resistance by targeting the replication stress response. Mechanistically, WEE1i sensitivity was associated with shortage of the dNTP pool and a concomitant increase in replication stress.

CONCLUSIONS

Targeting the replication stress response is a valid therapeutic option to overcome PARPi resistance including tumors without an underlying HRR deficiency. These preclinical insights are now being tested in several clinical trials where the PARPi is administered with either the WEE1i or the ATRi.

Abstract 2044: The target antigen determines the mechanism of acquired resistance to T cell based therapies

Introduction: Immunotherapy has revolutionized the way many cancers are treated. Despite its success, cancer patients eventually progress due to the emergence of resistance. In this scenario, the selection of the tumor antigen is important and can be decisive in the success of the clinical response, particularly when resistance emerge. T cell bispecific antibodies (TCBs) are engineered molecules that include, within a single entity, binding sites to the T cell receptor and to a tumor-specific or a tumor-associated antigen. It is assumed that, as all TCBs have the same mechanism of action, mechanisms of resistance are independent of the tumor antigen.

Objective: This study was designed to identify the mechanisms that trigger the resistance against HER2 and CEACAM5 T cell bispecific antibodies. We assessed TCB sensitivity using in vitro and in vivo assays combining human cell lines or patient-derived models with human lymphocytes.

Material and Methods: Using gastric CEA+/HER2+ MKN45 cells as a model and TCBs directed against CEA or HER2, here we show for the first time that the mechanism of resistance to a T cell-based therapy is dependent on the tumor antigen.

Results: Acquired resistant models to a high-affinity CEA-targeted TCB exhibit a reduction of CEA antigen levels due to epigenetic transcriptional silencing, which is reversible upon 5-AZA treatment. In contrast, a HER2-TCB resistant model maintains HER2 levels as HER2 downregulation led to an impairment of proliferation. Furthermore, using this latter model, we identified that disruption of interferon- gamma signaling confers resistance to killing by active T lymphocytes.

Conclusions: Our results unveil different mechanisms of acquired resistance to TCBs depending on the selected antigen, which will help in the design of combinatorial strategies to increase the efficacy of cancer immunotherapies and to anticipate and overcome resistances.

Citation Format: Alex Martínez-Sabadell, Beatriz Morancho, Irene Rius, Marta Escorihuela, Antonio Luque, Irene Chicote, Hector García Palmer, Marina Bacac, Joaquin Arribas, Enrique Javier Arenas Lahuerta. The target antigen determines the mechanism of acquired resistance to T cell based therapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2044.

Preclinical and Clinical Characterization of Fibroblast-derived Neuregulin-1 on Trastuzumab and Pertuzumab Activity in HER2-positive Breast Cancer

PURPOSE

To characterize expression of neuregulin-1 (NRG1), an HER3 ligand, in HER2-positive breast cancer and its relation with the efficacy of trastuzumab with or without pertuzumab.

EXPERIMENTAL DESIGN

Characterization of NRG1 expression in tumor cell lines, in tumor specimens, and in cancer-associated fibroblasts (CAFs). Patient-derived CAFs were used to investigate NRG1 impact on the activity of trastuzumab with or without pertuzumab in HER2-positive breast cancer cells. The relationship between NRG1 expression and pathologic response to anti-HER2-based neoadjuvant therapy was assessed in a retrospective patient cohort and in the NeoSphere trial.

RESULTS

NRG1 was expressed in HER2-positive breast cancer-derived fibroblasts at significantly higher levels than in cancer cells. NRG1 and the conditioned media (CM) from CAFs phosphorylated HER3 and AKT in cancer cells and mediated trastuzumab resistance. Stable genetic depletion of NRG1 from CAFs overcame trastuzumab resistance. Pertuzumab effectively suppressed trastuzumab resistance mediated by either NRG1 or CAF's CM. NRG1 engaged an epithelial-to-mesenchymal transition that was prevented by trastuzumab and pertuzumab. In clinical samples, stromal and/or tumor cell expression of NRG1 determined by immunohistochemistry was uncommon (13.2%) yet significantly linked with residual disease following trastuzumab-based neoadjuvant therapy. In the NeoSphere trial, the magnitude of the difference of pathologic complete response rates favoring the pertuzumab arm was higher in the NRG1-high group.

CONCLUSIONS

CAF-derived NRG1 mediates trastuzumab resistance through HER3/AKT, which might be reverted by pertuzumab. In patients with HER2-positive breast cancer, high expression of NRG1 was associated to poor response to trastuzumab, but not in combination with pertuzumab.

RANK signaling increases after anti-HER2 therapy contributing to the emergence of resistance in HER2-positive breast cancer

BACKGROUND

Around 15-20% of primary breast cancers are characterized by HER2 protein overexpression and/or HER2 gene amplification. Despite the successful development of anti-HER2 drugs, intrinsic and acquired resistance represents a major hurdle. This study was performed to analyze the RANK pathway contribution in HER2-positive breast cancer and anti-HER2 therapy resistance.

METHODS

RANK and RANKL protein expression was assessed in samples from HER2-positive breast cancer patients resistant to anti-HER2 therapy and treatment-naive patients. RANK and RANKL gene expression was analyzed in paired samples from patients treated with neoadjuvant dual HER2-blockade (lapatinib and trastuzumab) from the SOLTI-1114 PAMELA trial. Additionally, HER2-positive breast cancer cell lines were used to modulate RANK expression and analyze in vitro the contribution of RANK signaling to anti-HER2 resistance and downstream signaling.

RESULTS

RANK and RANKL proteins are more frequently detected in HER2-positive tumors that have acquired resistance to anti-HER2 therapies than in treatment-naive ones. RANK (but not RANKL) gene expression increased after dual anti-HER2 neoadjuvant therapy in the cohort from the SOLTI-1114 PAMELA trial. Results in HER2-positive breast cancer cell lines recapitulate the clinical observations, with increased RANK expression observed after short-term treatment with the HER2 inhibitor lapatinib or dual anti-HER2 therapy and in lapatinib-resistant cells. After RANKL stimulation, lapatinib-resistant cells show increased NF-κB activation compared to their sensitive counterparts, confirming the enhanced functionality of the RANK pathway in anti-HER2-resistant breast cancer. Overactivation of the RANK signaling pathway enhances ERK and NF-κB signaling and increases lapatinib resistance in different HER2-positive breast cancer cell lines, whereas RANK loss sensitizes lapatinib-resistant cells to the drug. Our results indicate that ErbB signaling is required for RANK/RANKL-driven activation of ERK in several HER2-positive cell lines. In contrast, lapatinib is not able to counteract the NF-κB activation elicited after RANKL treatment in RANK-overexpressing cells. Finally, we show that RANK binds to HER2 in breast cancer cells and that enhanced RANK pathway activation alters HER2 phosphorylation status.

CONCLUSIONS

Our data support a physical and functional link between RANK and HER2 signaling in breast cancer and demonstrate that increased RANK signaling may contribute to the development of lapatinib resistance through NF-κB activation. Whether HER2-positive breast cancer patients with tumoral RANK expression might benefit from dual HER2 and RANK inhibition therapy remains to be elucidated.

Personalized cancer therapy prioritization based on driver alteration co-occurrence patterns

Identification of actionable genomic vulnerabilities is key to precision oncology. Utilizing a large-scale drug screening in patient-derived xenografts, we uncover driver gene alteration connections, derive driver co-occurrence (DCO) networks, and relate these to drug sensitivity. Our collection of 53 drug-response predictors attains an average balanced accuracy of 58% in a cross-validation setting, rising to 66% for a subset of high-confidence predictions. We experimentally validated 12 out of 14 predictions in mice and adapted our strategy to obtain drug-response models from patients’ progression-free survival data. Our strategy reveals links between oncogenic alterations, increasing the clinical impact of genomic profiling.

Abstract 5573: Mechanism of resistance against T cell bispecific antibodies depends on targeted antigen

Immunotherapy has revolutionized the way several types of cancers are treated, including breast and gastric cancer. One of the most successful therapies against HER2 positive tumors, trastuzumab, is a monoclonal antibody originally designed to inhibit HER2, which has been shown to be effective because not only impairs cell cycle but also promotes an immune reaction. Despite that, lots of patients do not respond or relapse. T Cell Bispecific antibodies (TCBs) are a promising immunotherapeutic strategy designed to boost the immune response against tumors, as they redirect cytotoxic T cells against the tumor cells. TCBs are engineered molecules that include, within a single entity, binding sites to the T cell receptor and to a tumor-specific or a tumor-associated antigen. Clinical evidence shows that TCBs are an effective immunotherapy to treat cancer. However, little is known about the mechanisms of resistance against this promising therapy. Therefore, there is a need to anticipate the mechanism of response and resistance in order to improve the clinical outcome of patients. Indeed, as all TCBs behave with the same mechanism of action, the same mechanism of resistance, independent of the target, is expected. In this piece of work, we tried to address for the first time this question, by using as a tool a gastric HER2+/CEA+ cell line MKN45, and TCBs targeting these antigens. We generated resistant cells against both HER2-TCB and CEA-TCB in vitro. To generate these immunoresistant models we co-cultured peripheral blood mononuclear cells (PBMCs) with the TCBs for several months in order to obtain resistance. We corroborated the resistance in a organotypic 3D model and also in an in vivo humanized PBMC model. In addition, we assessed the impact on T-cell effector function, and resistant cells impair T-cell activity. We next evaluated the cause of resistance, and one plausible mechanism that also happen in hematological malignancies treated with Chimeric Antigen Receptor T-cells (CAR-Ts) is the loss of the antigen, in this case HER2 and CEA. Contrary to our expectations, we observed a dramatic loss of antigen in the case of CEA-TCB resistant cells, in contrast to HER2-TCB resistant cells, which maintain HER2 levels. Our results show for the first time that the mechanism of resistance against TCBs can be totally different depending on the target, and future studies and therapeutic approaches should take this into consideration. In addition, the HER2-TCB resistant MKN45 cells can be used as a tool to identify unknown mechanisms of resistance against the redirection of T-cells.

Citation Format: Alex Martínez-Sabadell, Enrique J. Arenas, Irene Rius, Macarena Román, Beatriz Morancho, Cristina Bernado, Joaquin Arribas. Mechanism of resistance against T cell bispecific antibodies depends on targeted antigen [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5573.

Abstract 1685: The EurOPDX Research Infrastructure: Supporting European and worldwide cancer research with patient-derived xenografts

Counteracting high failure rates in oncology drug development and improving therapeutic management of cancer patients requires preclinical models that can account for the complexity and heterogeneity of human tumors. Patient-derived cancer xenografts (PDXs) maintain histopathological features and genetic profiles of the original patient tumors and are increasingly recognized as reliable models to predict treatment efficacy and discover sensitivity and resistance biomarkers with immediate clinical relevance.Launched in 2013, the EurOPDX Consortium now gathers 18 academic research institutions throughout Europe and in the US (www.europdx.eu). The goal of the Consortium is to maximize exploitation of PDXs and other patient-derived models for cancer research by: (i) integrating institutional collections into a multicentre repository; (ii) defining common standards to improve the quality and reproducibility of oncology preclinical data; (iii) sharing models within and outside the consortium to perform collaborative precision oncology “xenopatient” trials. Building on its first successes, EurOPDX is now teaming up with other key academic and SME partners in a four-year project to build the “EurOPDX Distributed Infrastructure for Research on patient-derived Xenografts" (EDIReX project, Horizon 2020 grant no. 731105).This new cutting-edge European infrastructure offers access to PDX resources for academic and industrial cancer researchers through 6 state-of-the-art installations or “nodes”. We will present the specific objectives of the project, including our work towards standardization and optimization of biobanking, quality control and data tracking, and the performance of in vivo drug efficacy experiments. Access to the resource, including the distribution of cryopreserved samples from established models, the structured biobanking of user-developed models and the performance of drug efficacy studies, is offered through a grant application system which last deadline is planned mid-June 2020. Selection of the models by users and browsing of PDXs annotation data is made possible thanks to the newly-developed EurOPDX Data Portal (dataportal.europdx.eu), which will display approximately 1,000 models by April 2020 (including 700+ models of colorectal cancer, 80+ gastric and 80+ breast cancer models).We aim to improve preclinical and translational cancer research and promote innovation in oncology by integrating a European PDX repository and facilitating access to this much-needed resource for European and worldwide researchers.

Citation Format: Emilie Vinolo, Joaquin Arribas, Andrea Bertotti, Alejandra Bruna, Annette T. Byrne, Robert B. Clarke, Nathalie Conte, Steven de Jong, Didier Decaudin, Zdenka Dudova, Jos Jonkers, Daniela Krasser, Ales Krenek, Luisa Lanfrancone, Eleonora Leucci, Elisabetta Marangoni, Gunhild Mari Maelandsmo, Michaela Th. Mayrhofer, Terrence F. Meehan, Jens Henrik Norum, Hector G. Palmer, Alejandro Piris Gimenez, Leo Price, Sergio Roman-Roman, Francesca Sarno, Violeta Serra, Laura Soucek, Livio Trusolino, Marieke van de Ven, Luca Vezzadini, Alberto Villanueva, Andrea Wutte, Enzo Medico, on behalf of the EurOPDX Research Infrastructure. The EurOPDX Research Infrastructure: Supporting European and worldwide cancer research with patient-derived xenografts [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1685.

Overview of virus and cancer relationships. Position paper

The role of certain viruses in the etiology of some tumors is today indisputable, but there is a lack, however, of annoverview of the relationship between viruses and cancer with amultidisciplinary approach. For this reason, the Health Sciences Foundation has convened a group of professionals from different areas of knowledge to discuss the relationship between viruses and cancer, and the present document is the result of these deliberations. Although viruses cause only 10-15% of cancers, advances in oncology research are largely due to the work done during the last century on tumor viruses. The clearest cancer-inducing viruses are: HPV, HBV, HCV, EBV and, depending on the geographical area, HHV-8, HTLV-1 and HIV. HPVs, for example, are considered to be the causative agents of cervical carcinomas and, more recently, of a proportion of other cancers. Among the Herpes viruses, the association with the development of neoplasms is well established for EBV and HHV-8. Viruses can also be therapeutic agents in certain neoplasms and, thus, some oncolytic viruses with selective tropism for tumor cells have been approved for clinical use in humans. It is estimated that the prophylaxis or treatment of viral infections could prevent at least 1.5 million cancer deaths per year.

Implications of grey zone results for routine hepatitis C virus screening with the ARCHITECT HCV-Ag assay

AIMS

Hepatitis C virus antigen (HCV-Ag) detection requires retesting for samples with grey zone results (GzR), adding cost and time and decreasing reliability. Our aim in this study was to evaluate the frequency and significance of GzR during the use of the automated Architect HCV-Ag assay in routine clinical practice.

METHODS AND RESULTS

We studied HCV-Ag levels in 952 serum samples using the ARCHITECT HCV-Ag assay. GzR were detected in 33 samples; 25 were reactive on retesting and 19 were anti-HCV positive. Seventeen of these 19 samples were tested for HCV-RNA and were all reactive (viral loads <10⁴  IU ml^-1 ). The remaining six samples were anti-HCV nonreactive and had undetectable HCV-RNA. Eight GzR samples were nonreactive on retesting, seven were anti-HCV nonreactive (three underwent HCV-RNA quantification and were all nonreactive), and one was anti-HCV reactive (HCV-RNA nonreactive). No significant differences were found on comparing HCV-Ag values.

CONCLUSIONS

Grey zone results found to be negative on retesting do not need additional technique testing, except in donor screening scenarios, where the use of molecular methods would be advisable.

SIGNIFICANCE AND IMPACT OF THE STUDY

 The proposed diagnostic algorithm confirms that, eventhough GzR occur, hepatitis C virus antigen is a robust alternative to HCV-RNA detection in the active detection of infections.

LOXL2-mediated H3K4 oxidation reduces chromatin accessibility in triple-negative breast cancer cells

Oxidation of H3 at lysine 4 (H3K4ox) by lysyl oxidase-like 2 (LOXL2) generates an H3 modification with an unknown physiological function. We find that LOXL2 and H3K4ox are higher in triple-negative breast cancer (TNBC) cell lines and patient-derived xenografts (PDXs) than those from other breast cancer subtypes. ChIP-seq revealed that H3K4ox is located primarily in heterochromatin, where it is involved in chromatin compaction. Knocking down LOXL2 reduces H3K4ox levels and causes chromatin decompaction, resulting in a sustained activation of the DNA damage response (DDR) and increased susceptibility to anticancer agents. This critical role that LOXL2 and oxidized H3 play in chromatin compaction and DDR suggests that functionally targeting LOXL2 could be a way to sensitize TNBC cells to conventional therapy.

Abstract 3503: Biomarkers for inhibitors of the replication stress response proteins WEE1 and ATR in triple negative breast cancer

Replication stress (RS) is a hallmark of cancer and has the potential to be exploited by selective DNA Damage Response inhibitors. During replication stress, the DNA polymerase is uncoupled from the replisome helicase activity resulting in extended regions of single strand DNA that lead to the initiation of a replication stress response (RSR). Two key regulators of the RSR are the ATR and WEE1 kinases. Here, we aimed to identify patient selection biomarkers for WEE1 and ATR inhibitors (WEE1i, ATRi) from a cohort of 37 patient-derived tumor xenografts (PDX) from ovarian or triple negative breast cancer, 20 of which harbored BRCA1/BRCA2deleterious mutations. The antitumor response of the WEE1i AZD1775 and the ATRi AZD6837 was evaluated, and PDX tumors were characterized by exome sequencing, metabolomics, western blot and immunohistochemistry. AZD1775 treatment response in PDXs, measured as tumor regressions (≤-30% change in tumor volume), was observed in 28% of models tested. Exome sequencing identified an association between treatment response and concomitant alterations in RB1 and STK11 (LKB1), whose functional relevance was validated in an in vitro model. Immunoblots showed that WEE1i treatment resulted in downregulation of the ribonucleotide reductase subunit RRM2 and induction of an S-phase DNA damage response (DDR) in vivo. Metabolomics identified a profound change in the purine and pyrimidine synthesis pathways in WEE1i-sensitive PDXs and these changes appear functionally relevant since PDX ex vivo data demonstrate rescue of the WEE1i effects after addition of nucleosides. Another important association with WEE1i sensitivity was increased cyclin E expression. Together, these data suggest that early entry into S phase and an imbalance of origin firing to available dNTPs represent drivers of sensitivity to the WEE1i. Interestingly by contrast, ATRi-sensitive PDXs (representing 10% of the models) were characterized primarily by those tumors harboring ATM alterations, suggesting that synthetic lethality with this major DDR pathway is the primary mechanism of sensitivity to the ATR inhibitor in ovarian and triple negative breast cancer. This study therefore highlights differences between the drivers of sensitivity to inhibitors of these two important RSR proteins.

Citation Format: Violeta Serra, Cristina Cruz, Zhongwu Lai, Marta Castroviejo-Bermejo, Marta Palafox, Urszula M. Polanska, Gemma N. Jones, Anderson Wang, Filippos Michopoulos, Rachel Brough, Brian Dougherty, Elaine Cadogan, Susan Critchlow, Alejandra Bruna, J. Carl Barrett, Cristina Saura, Christopher J. Lord, Carlos Caldas, Joaquin Arribas, Judith Balmaña, Mark J. O’Connor. Biomarkers for inhibitors of the replication stress response proteins WEE1 and ATR in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3503.

MEN1309/OBT076, a First-In-Class Antibody-Drug Conjugate Targeting CD205 in Solid Tumors

CD205 is a type I transmembrane glycoprotein and is a member of the C-type lectin receptor family. Analysis by mass spectrometry revealed that CD205 was robustly expressed and highly prevalent in a variety of solid malignancies from different histotypes. IHC confirmed the increased expression of CD205 in pancreatic, bladder, and triple-negative breast cancer (TNBC) compared with that in the corresponding normal tissues. Using immunofluorescence microscopy, rapid internalization of the CD205 antigen was observed. These results supported the development of MEN1309/OBT076, a fully humanized CD205-targeting mAb conjugated to DM4, a potent maytansinoid derivate, via a cleavable N-succinimidyl-4-(2-pyridyldithio) butanoate linker. MEN1309/OBT076 was characterized in vitro for target binding affinity, mechanism of action, and cytotoxic activity against a panel of cancer cell lines. MEN1309/OBT076 displayed selective and potent cytotoxic effects against tumor cells exhibiting strong and low to moderate CD205 expression. In vivo, MEN1309/OBT076 showed potent antitumor activity resulting in durable responses and complete tumor regressions in many TNBC, pancreatic, and bladder cancer cell line-derived and patient-derived xenograft models, independent of antigen expression levels. Finally, the pharmacokinetics and pharmacodynamic profile of MEN1309/OBT076 was characterized in pancreatic tumor-bearing mice, demonstrating that the serum level of antibody-drug conjugate (ADC) achieved through dosing was consistent with the kinetics of its antitumor activity. Overall, our data demonstrate that MEN1309/OBT076 is a novel and selective ADC with potent activity against CD205-positive tumors. These data supported the clinical development of MEN1309/OBT076, and further evaluation of this ADC is currently ongoing in the first-in-human SHUTTLE clinical trial.

HER2 and p95HER2 differentially regulate miRNA expression in MCF-7 breast cancer cells and downregulate MYB proteins through miR-221/222 and miR-503

The HER2 oncogene and its truncated form p95HER2 play central roles in breast cancer. Here, we show that although HER2 and p95HER2 generally elicit qualitatively similar changes in miRNA profile in MCF-7 breast cancer cells, a subset of changes are distinct and p95HER2 shifts the miRNA profile towards the basal breast cancer subtype. High-throughput miRNA profiling was carried out 15, 36 and 60 h after HER2 or p95HER2 expression and central hits validated by RT-qPCR. miRNAs strongly regulated by p95HER2 yet not by HER2, included miR-221, miR-222, miR-503, miR-29a, miR-149, miR-196 and miR-361. Estrogen receptor-α (ESR1) expression was essentially ablated by p95HER2 expression, in a manner recapitulated by miR-221/-222 mimics. c-Myb family transcription factors MYB and MYBL1, but not MYBL2, were downregulated by p95HER2 and by miR-503 or miR-221/-222 mimics. MYBL1 3′UTR inhibition by miR-221/222 was lost by deletion of a single putative miR-221/222 binding sites. p95HER2 expression, or knockdown of either MYB protein, elicited upregulation of tissue inhibitor of matrix metalloprotease-2 (TIMP2). miR-221/222 and -503 mimics increased, and TIMP2 knockdown decreased, cell migration and invasion. A similar pathway was operational in T47D- and SKBr-3 cells. This work reveals important differences between HER2- and p95HER2- mediated miRNA changes in breast cancer cells, provides novel mechanistic insight into regulation of MYB family transcription factors by p95HER2, and points to a role for a miR-221/222– MYB family–TIMP2 axis in regulation of motility in breast cancer cells.

RAD51 foci as a functional biomarker of homologous recombination repair and PARP inhibitor resistance in germline BRCA-mutated breast cancer

Background

BRCA1 and BRCA2 (BRCA1/2)-deficient tumors display impaired homologous recombination repair (HRR) and enhanced sensitivity to DNA damaging agents or to poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi). Their efficacy in germline BRCA1/2 (gBRCA1/2)-mutated metastatic breast cancers has been recently confirmed in clinical trials. Numerous mechanisms of PARPi resistance have been described, whose clinical relevance in gBRCA-mutated breast cancer is unknown. This highlights the need to identify functional biomarkers to better predict PARPi sensitivity.

Patients and methods

We investigated the in vivo mechanisms of PARPi resistance in gBRCA1 patient-derived tumor xenografts (PDXs) exhibiting differential response to PARPi. Analysis included exome sequencing and immunostaining of DNA damage response proteins to functionally evaluate HRR. Findings were validated in a retrospective sample set from gBRCA1/2-cancer patients treated with PARPi.

Results

RAD51 nuclear foci, a surrogate marker of HRR functionality, were the only common feature in PDX and patient samples with primary or acquired PARPi resistance. Consistently, low RAD51 was associated with objective response to PARPi. Evaluation of the RAD51 biomarker in untreated tumors was feasible due to endogenous DNA damage. In PARPi-resistant gBRCA1 PDXs, genetic analysis found no in-frame secondary mutations, but BRCA1 hypomorphic proteins in 60% of the models, TP53BP1-loss in 20% and RAD51-amplification in one sample, none mutually exclusive. Conversely, one of three PARPi-resistant gBRCA2 tumors displayed BRCA2 restoration by exome sequencing. In PDXs, PARPi resistance could be reverted upon combination of a PARPi with an ataxia-telangiectasia mutated (ATM) inhibitor.

Conclusion

Detection of RAD51 foci in gBRCA tumors correlates with PARPi resistance regardless of the underlying mechanism restoring HRR function. This is a promising biomarker to be used in the clinic to better select patients for PARPi therapy. Our study also supports the clinical development of PARPi combinations such as those with ATM inhibitors.

Highlights of the 2017 European AIDS Clinical Society (EACS) Guidelines for the treatment of adult HIV-positive persons version 9.0

Background

The European AIDS Clinical Society (EACS) Guidelines have since 2005 provided multidisciplinary recommendations for the care of HIV‐positive persons in geographically diverse areas.

Guideline highlights

Major revisions have been made in all sections of the 2017 Guidelines: antiretroviral treatment (ART), comorbidities, coinfections and opportunistic diseases. Newly added are also a summary of the main changes made, and direct video links to the EACS online course on HIV Management. Recommendations on the clinical situations in which tenofovir alafenamide may be considered over tenofovir disoproxil fumarate are provided, and recommendations on which antiretrovirals can be used safely during pregnancy have been revised. Renal and bone toxicity and hepatitis C virus (HCV) treatment have been added as potential reasons for ART switches in fully virologically suppressed individuals, and dolutegravir/rilpivirine has been included as a treatment option. In contrast, dolutegravir monotherapy is not recommended. New recommendations on non‐alcoholic fatty liver disease, chronic lung disease, solid organ transplantation, and prescribing in elderly are included, and human papilloma virus (HPV) vaccination recommendations have been expanded. All drug–drug interaction tables have been updated and new tables are included. Treatment options for direct‐acting antivirals (DAAs) have been updated and include the latest combinations of sofosbuvir/velpatasvir/voxilaprevir and glecaprevir/pibrentasvir. Recommendations on management of DAA failure and acute HCV infection have been expanded. For treatment of tuberculosis (TB), it is underlined that intermittent treatment is contraindicated, and for resistant TB new data suggest that using a three‐drug combination may be as effective as a five‐drug regimen, and may reduce treatment duration from 18‐24 to 6‐10 months.

Conclusions

Version 9.0 of the EACS Guidelines provides a holistic approach to HIV care and is translated into the six most commonly spoken languages.

Abstract 3129: Patient-derived tumor xenografts (PDXs) recapitulate the antitumor activity of novel therapies in metastatic breast cancer (MBC) patients (pts)

PDXs are preferred laboratory models that recapitulate the biology of pts’ tumors. We aimed to assess if the antitumor activity of novel therapies in PDXs correlates with the observed activity in the corresponding MBC patient, which would support cross-analysis of drug/genotype vulnerabilities.

MBC pts eligible for clinical trials were offered a research biopsy and establishment of PDX, under an IRB-approved protocol. Biopsies were implanted in nude mice subcutaneously. Upon successful engraftment, models were expanded for drug testing, specifically with the same drug/combination given to the patient. This is a retrospective analysis of our MBC patient/PDX (Pt/PDX) co-clinical trial cohort. Pts’ outcomes were measured as: RECIST response, clinical benefit [CB: partial response (PR) or stable disease (SD) &gt;4 months], and time to progression [TTP: time until RECIST progressive disease (PD), in months). PDX endpoints were measured as: TTP (time until 25% increase in tumor volume, in days), response (WHO criteria, at week 3), and relative area under the curve (rAUC) of treated versus vehicle. A concordant Pt/PDX response was defined as CB in pts whose paired PDX showed PR/SD, or no-CB in pts whose paired PDX showed PD. Pts outcomes and PDX endpoints were correlated using Spearman's test.

We identified 10 MBC pts (7 TNBC, 3 HR+; all biopsies from skin/subcutaneous lesions) with corresponding PDX, treated with paired therapies (7 molecularly matched): 3 lurbinectedin (BRCA1-mut), 3 olaparib (BRCA1-mut), 1 AZD5363 + fulvestrant (AKT1-mut), 1 AZD5363 + paclitaxel, 1 buparlisib, 1 eribulin. In 9/10 cases we found concordant Pt/PDX responses (6 cases with no-CB in patient/PD in PDX, 3 with CB/SD; and 1 lurbinectedin case with no-CB/PR). Two pts had biopsy for PDX implantation at progression of paired therapy and were excluded from TTP analyses. In cases with concordant Pt/PDX response, we found a significant correlation between RECIST response in pts and rAUC in PDX (ρ=0.82, p=0.03), a trend for comparable TTP in pts and TTP in PDX (ρ=0.67, p=0.10), but no correlation between RECIST response in pts and response at week 3 in PDX (ρ=0.46, p=0.30).

In this cohort of MBC pts, we found high concordance in Pt/PDX response. Our results suggest that rAUC in PDX may be the best read-out to identify relevant drug/genotype associations that can potentially be translated to patient benefit. Data will be updated with additional ongoing PDX experiments.

Citation Format: Mafalda Oliveira, Javier Pascual, Cristina Cruz, Alberto Gris, Marta Palafox, Alba Llop, Marta Castroviejo, Cristina Viaplana, Yasir H Ibrahim, Joaquin Arribas, Javier Cortés, José Baselga, Jordi Rodón, Judith Balmaña, Rodrigo Dienstmann, Cristina Saura, Violeta Serra. Patient-derived tumor xenografts (PDXs) recapitulate the antitumor activity of novel therapies in metastatic breast cancer (MBC) patients (pts) [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 3129. doi:10.1158/1538-7445.AM2017-3129

Abstract 2630: MEN1309, a novel antibody drug conjugate (ADC) targeting Ly75 antigen, induces complete responses in several xenografts of solid tumors

The cell surface antigen Lymphocyte antigen 75 (LY75, CD205, DEC-205) is over-expressed in several tumor histotypes. It is a type I C-type lectin receptor (CLR), normally expressed on various APC subsets, characterized by a cytoplasmic domain containing protein motifs crucial for endocytosis and internalization upon ligation. These features make the antigen ideal to be exploited as a target for a novel ADC. MEN1309 is a humanized IgG1 antibody directed against the cell surface antigen Ly75, conjugated through a cleavable linker to a potent maytansinoid microtubule disruptor, DM4. In this study, we evaluated the in vitro and in vivo (xenografts and PDX) efficacy of MEN1309 in different tumor histotypes. A PK/PD relationship was also investigated in tumor-bearing mice. IHC demonstrated high prevalence of Ly75 in human pancreatic, triple negative breast, and bladder cancers, as well as in diffuse large B-cell lymphoma. In vitro experiments showed that cytotoxic activity of MEN1309 was in nM/sub nM range against several lymphoma, pancreatic, bladder and triple-negative breast cancer (TNBC) cell lines. Moreover, MEN1309 exhibited high cell-killing ability against cells having either strong as well as low to moderate antigen expression. In vivo, MEN1309 at 2.5-5 mg/kg (schedule varying from single dose, q7dx3, or q21dx3) showed an impressive antitumor activity, resulting in complete and long lasting responses in most of the xenograft models representing lymphoma, TNBC, bladder and pancreatic cancers, expressing the antigen at high but also at low levels. No treatment related toxicity in terms of change of body weight and death events were detected. Moreover, the administration of (i) isotype control-DM4, (ii) the non-conjugate antibody IgG1 and (iii) the free toxin DM4 (at a dosage corresponding to the equimolar concentration linked at 10 mg/kg ADC) showed little to no therapeutic efficacy on tumor growth. In TNBC patient-derived xenograft (PDX) model (coming from a heavily pre-treated patient and expressing high level of the antigen Ly75), MEN1309 (5 mg/kg q21dx3) showed a complete tumor regression. Finally, in the pancreatic adenocarcinoma xenograft model HPAFII, the pharmacokinetics profile in serum of MEN1309 at 5 mg/kg was characterized and it was qualitatively correlated, using immunofluorescence, with the occurrence of phosphorylation of Serine 10 of H3 Histone in cancer cells, as a pharmacodynamic (PD) marker of DM4 activity on microtubules. Initial ADC exposure was noteworthy and was followed by a relatively fast decline. In parallel with the decay of the serum ADC concentrations there was a progressive increase in the number of positive cells showing the PD marker for mitotic arrest. Overall, our data suggest that MEN1309 is a selective and potent novel antitumoral ADC and it deserves to enter into aPhase I study for a variety of Ly75 positive tumor histotypes.

Citation Format: Mario Bigioni, Giuseppe Merlino, Cristina Bernadó Morales, Rossana Bugianesi, Attilio Crea, Rosanna Manno, Joaquin Arribas, Rachel Dusek, Nickolas Attanasio, Keith Wilson, Christian Rohlff, Monica Binaschi. MEN1309, a novel antibody drug conjugate (ADC) targeting Ly75 antigen, induces complete responses in several xenografts of solid tumors [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 2630. doi:10.1158/1538-7445.AM2017-2630

Abstract B02: Co-clinical trial of olaparib in breast and ovarian patient-derived tumor xenografts (PDX) enables the identification of response biomarkers

Background: Women with heterozygous germline mutations in BRCA1 or BRCA2 are predisposed to developing breast or ovarian cancers, since BRCA1/2 mutation results in impaired high-fidelity DNA repair by homologous recombination (HR) and subsequently genetic instability. In non-gBRCA TNBC, HR deficiency occurs at the somatic level, by means of BRCA1 mutation, BRCA1 epigenetic loss or mutation in other HR-associated genes. PARP1/2 inhibitors (PARPi) are active anti-cancer agents in gBRCA with advanced breast or ovarian cancer. However, not all HR-deficient tumors respond to PARP blockade, and eventually all develop acquired resistance. Here, we sought to identify PARPi response biomarkers using PDX derived from both the early disease and the metastatic setting.

Methods: We developed a panel of PDX from patients harboring or not germline BRCA1/2 mutations, namely from 26 primary or advanced breast cancer and 2 high-grade serous metastatic ovarian cancer (HGSOC). The antitumor activity of the PARP1/2 inhibitor olaparib as single agent (50 mg/kg) was assessed in all models. To study the mechanisms of acquired resistance, the olaparib-sensitive PDXs were exposed to olaparib for &gt;100 days, until individual tumors regrew. The tumor's capacity to repair DNA double strand breaks was estimated by quantification of the BRCA1 and RAD51 nuclear foci in the S/G2-phase of the cell cycle. We investigated the correlation between the tumor's BRCA1/RAD51 foci formation and sensitivity to olaparib, and also identified potential genetic modifiers of PARPi sensitivity by targeted sequencing.

Results: Seven out of 28 PDX (25%) treated with single agent olaparib exhibited tumor regression or disease stabilization. Among the non-gBRCA PDX, BRCA1 hypermethylation or PALB2 mutation were present in olaparib-sensitive PDX. No genetic reversions in BRCA1/2 mutations were identified as the mechanism of olaparib resistance in gBRCA but BRCA1 foci formation was observed in 6 out of 10 resistant models (60%). Nuclear RAD51 foci formation correlated with PARPi resistance in twenty PDX models investigated, either with primary or acquired resistance. The duration of response was similar between gBRCA and non-gBRCA PDX. Acquired-resistance mechanisms involve restoration of HR functionality.

Conclusions: Our study highlights that somatic HR-deficiency is frequent in TNBC and provides the basis of sensitivity to PARPi. In our gBRCA (n=12) and non-gBRCA (n=16) PDX, reactivation of HR functionality measured as RAD51 foci formation is a frequent event that is associated with PARPi resistance.

Citation Format: Violeta Serra, Cristina Cruz, Marta Castroviejo, Sara Gutiérrez, Alba Llop, Alejandra Bruna, Beatriz Morancho, Ginevra Caratú, Ludmila Prudkin, Ana Vivancos, Paolo Nuciforo, Mark O'Connor, Jos Jonkers, Carlos Caldas, Joaquin Arribas, José Baselga, Isabel T. Rubio, Cristina Saura, Orland Díez, Judith Balmaña, Javier Cortés. Co-clinical trial of olaparib in breast and ovarian patient-derived tumor xenografts (PDX) enables the identification of response biomarkers. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr B02.

Cancer Therapeutic Resistance: Progress and Perspectives (April 7-8, 2016 - Barcelona, Spain)

At the Cancer Therapeutic Resistance: Progress and Perspectives conference, in Barcelona, Spain, April 7-8, 2016, researchers, clinicians and students gathered to discuss our current understanding of intrinsic and acquired resistance of tumors to cancer therapies and to explore how to translate strategies to predict risk or overcome resistance to the clinic. The sessions covered a wide range of topics, including cancer omics, molecular classification, clinically relevant tumor models, biomarkers and novel therapeutic targets, and personalized medicine, with talks from many international experts in the field. This report highlights the main presentations that demonstrate the progress being made in predicting and identifying drug resistance in patients with cancer, personalized approaches to direct treatment and understanding the mechanisms involved. With better models of human cancer and powerful high-throughput screening techniques, translation to the clinic leading to tangible benefits for patients is attainable.

Prospective study on cost-effectiveness of home-based motor assessment in Parkinson's disease

Introduction Treatment adjustments in Parkinson's disease (PD) are in part dependent on motor assessments. The aim of this study was to evaluate the cost-effectiveness of home-based motor monitoring plus standard in-office visits versus in-office visits alone in patients with advanced PD. Methods The procedures consisted of a prospective, one-year follow-up, randomized, case-control study. A total of 40 patients with advanced PD were randomized into two groups: 20 patients underwent home-based motor monitoring by using wireless motion sensor technology, while the other 20 patients had in-office visits. Motor and non-motor symptom severities, quality of life, neuropsychiatric symptoms, and comorbidities were assessed every four months. Direct costs were assessed using a standardized questionnaire. Cost-effectiveness was assessed using the incremental cost-effectiveness ratio (ICER). Results Both groups of PD patients were largely comparable in their clinical and demographic variables at baseline; however, there were more participants using levodopa-carbidopa intestinal gel in the home-based motor monitoring group. There was a trend for lower Unified Parkinson's Disease Rating Scale functional status (UPDRS II) scores in the patients monitored at home compared to the standard clinical follow-up ( p = 0.06). However, UPDRS parts I, III, IV and quality-adjusted life-years scores were similar between both groups. Home-based motor monitoring was cost-effective in terms of improvement of functional status, motor severity, and motor complications (UPDRS II, III; IV subscales), with an ICER/UPDRS ranging from €126.72 to €701.31, respectively. Discussion Home-based motor monitoring is a tool which collects cost-effective clinical information and helps augment health care for patients with advanced PD.

High HER2 protein levels correlate with increased survival in breast cancer patients treated with anti-HER2 therapy

INTRODUCTION

Current methods to determine HER2 (human epidermal growth factor receptor 2) status are affected by reproducibility issues and do not reliably predict benefit from anti-HER2 therapy. Quantitative measurement of HER2 may more accurately identify breast cancer (BC) patients who will respond to anti-HER2 treatments.

METHODS

Using selected reaction monitoring mass spectrometry (SRM-MS), we quantified HER2 protein levels in formalin-fixed, paraffin-embedded (FFPE) tissue samples that had been classified as HER2 0, 1+, 2+ or 3+ by immunohistochemistry (IHC). Receiver operator curve (ROC) analysis was conducted to obtain optimal HER2 protein expression thresholds predictive of HER2 status (by standard IHC or in situ hybridization [ISH]) and of survival benefit after anti-HER2 therapy.

RESULTS

Absolute HER2 amol/μg levels were significantly correlated with both HER2 IHC and amplification status by ISH (p < 0.0001). A HER2 threshold of 740 amol/μg showed an agreement rate of 94% with IHC and ISH standard HER2 testing (p < 0.0001). Discordant cases (SRM-MS-negative/ISH-positive) showed a characteristic amplification pattern known as double minutes. HER2 levels >2200 amol/μg were significantly associated with longer disease-free survival (DFS) and overall survival (OS) in an adjuvant setting and with longer OS in a metastatic setting.

CONCLUSION

Quantitative HER2 measurement by SRM-MS is superior to IHC and ISH in predicting outcome after treatment with anti-HER2 therapy.

High HER2 expression correlates with response to the combination of lapatinib and trastuzumab

PURPOSE

Expression of p95HER2 has been associated with resistance to trastuzumab-based therapy in patients with metastatic breast cancer. Conversely, high levels of HER2 have been linked with increased clinical benefit from anti-HER2 therapy. In this work, we aimed to investigate whether the levels of p95HER2 and HER2 can predict response to anti-HER2 therapy in patients with breast cancer.

EXPERIMENTAL DESIGN

We measured p95HER2 and HER2 by VeraTag and HERmark, respectively, in primary tumors of patients enrolled in the neoadjuvant phase III study NeoALTTO and correlated these variables with pathologic complete response (pCR) and progression-free survival (PFS) following lapatinib (L), trastuzumab (T), or the combination of both agents (L+T).

RESULTS

A positive correlation between p95HER2 and HER2 levels was found in the 274 cases (60%) in which quantification of both markers was possible. High levels of these markers were predictive for pCR, especially in the hormone receptor (HR)-positive subset of patients. High HER2 expression was associated with increased pCR rate upon L+T irrespective of the HR status. To examine whether the levels of either p95HER2 or HER2 could predict for PFS in patients treated with lapatinib, trastuzumab or L+T, we fit to the PFS data in Cox models containing log2(p95HER2) or log2(HER2). Both variables correlated with longer PFS.

CONCLUSIONS

Increasing HER2 protein expression correlated with increased benefit of adding lapatinib to trastuzumab. HER2 expression is a stronger predictor of pCR and PFS than p95HER2 for response to lapatinib, trastuzumab and, more significantly, L+T.

Poly (ADP-ribose) polymerase inhibition enhances trastuzumab antitumour activity in HER2 overexpressing breast cancer

AIM

Poly (ADP-ribose) polymerase (PARP) inhibitors have shown promising results in Breast Cancer (BRCA) deficient breast cancer, but not in molecularly unselected patient populations. Two lines of research in this field are needed: the identification of novel subsets of patients that could potentially benefit from PARP inhibitors and the discovery of suitable targeted therapies for combination strategies.

METHODS

We tested PARP inhibition, alone or combined with the anti-HER2 antibody trastuzumab on HER2+ breast cancer. We used two PARP inhibitors in clinical development, olaparib and rucaparib, as well as genetic downmodulation of PARP-1 for in vitro studies. DNA damage was studied by the formation of γH2AX foci and comet assay. Finally, the in vivo anti-tumour effect of olaparib and trastuzumab was examined in nude mice subcutaneously implanted with BT474 cells.

RESULTS

In a panel of four HER2 overexpressing breast cancer cell lines, both olaparib and rucaparib significantly decreased cell growth and enhanced anti-tumour effects of trastuzumab. Cells exposed to olaparib and trastuzumab had greater DNA damage than cells exposed to each agent alone. Mechanistic exploratory assays showed that trastuzumab downmodulated the homologous recombination protein proliferating cell nuclear antigen (PCNA). Combination treatment in the BT474 xenograft model resulted in enhanced growth inhibition, reduced tumour cell proliferation, and increased DNA damage and apoptosis.

CONCLUSION

Taken together, our results show that PARP inhibition has antitumour effects and increases trastuzumab activity in HER2 overexpressing breast cancer. These findings make this novel combination a promising strategy for clinical development.

Enhancing the Biological Relevance of Secretome-Based Proteomics by Linking Tumor Cell Proliferation and Protein Secretion

Secretome profiling has become a methodology of choice for the identification of tumor biomarkers. We hypothesized that due to the dynamic nature of secretomes cellular perturbations could affect their composition but also change the global amount of protein secreted per cell. We confirmed our hypothesis by measuring the levels of secreted proteins taking into account the amount of proteome produced per cell. Then, we established a correlation between cell proliferation and protein secretion that explained the observed changes in global protein secretion. Next, we implemented a normalization correcting the statistical results of secretome studies by the global protein secretion of cells into a generalized linear model (GLM). The application of the normalization to two biological perturbations on tumor cells resulted in drastic changes in the list of statistically significant proteins. Furthermore, we found that known epithelial-to-mesenchymal transition (EMT) effectors were only statistically significant when the normalization was applied. Therefore, the normalization proposed here increases the sensitivity of statistical tests by increasing the number of true-positives. From an oncology perspective, the correlation between protein secretion and cellular proliferation suggests that slow-growing tumors could have high-protein secretion rates and consequently contribute strongly to tumor paracrine signaling.

Abstract P1-08-42: High HER2 expression correlates with response to trastuzumab and the combination of trastuzumab and lapatinib in the NeoALTTO phase III trial

Background: Expression of p95HER2, a truncated form of HER2 lacking the extracellular domain, has been associated with resistance to trastuzumab (T)-based therapy in metastatic breast cancer patients. Conversely, high levels of HER2 have been correlated with increased clinical benefit from anti-HER2 therapy in the neoadjuvant setting. In this work we correlated the expression of p95HER2 and HER2 with pathological complete response (pCR) following T, lapatinib (L) or the combination of both agents (T+L) with paclitaxel.

Methods: p95HER2 and HER2 were quantified by VeraTag® and HERmark® (Monogram Biosciences), respectively, in primary tumors of 455 patients enrolled in the phase III neoadjuvant study NeoALTTO (Baselga J. et al. Lancet, 2012). The relationship of pCR status to p95HER2 and HER2 was studied using logistic regression models, which accounted for stratification factors and treatment. Unless specified, p95HER2 and HER2 were included as log terms.

Results: p95HER2 was measurable in 283 cases (62%) and HER2 in 327 cases (72%). A positive correlation between p95HER2 and HER2 levels was found in the 274 cases (60%) where quantification of both markers was available. Increased HER2 was strongly associated with increased pCR rate in patients treated with the combination of T+L (OR 5.09, 95%CI 2.27-11.44; p&lt;0.01), with a trend observed also in the L-only arm (OR 1.88, 95% CI 0.96-3.70; p = 0.067). Overall, patients with tumors that were HER2-positive (&gt;17.8 RF/mm2) by HERmark had a higher pCR rate than those that were HER2-negative by HERmark (39% vs. 11%, respectively; p&lt;0.001). Increasing p95HER2 levels did not predict for pCR in the L or T+L arms and showed weak evidence (p = 0.073) of an increase in pCR in the T arm.

In an unplanned analysis, we examined the odds of achieving response to anti-HER2 therapy in patients with HER2 levels above and below the median (100 RF/mm2, HER2 entered as a binary covariate). HER2 levels above the median predicted a higher response rate to T (OR 3.6, 95% CI 1.2-11; p&lt;0.05) and, more significantly, to T+L (OR 6.01, 95% CI 2.51-14.4; p&lt;0.001). In particular, patients treated with T+L had a higher probability to achieve pCR compared to T alone when HER2 was above the median (T+L = 73% pCR vs. T = 43% pCR, p&lt;0.01; OR 3.74, 95% CI 1.57-8.90), but not when HER2 was below the median (T+L = 29% pCR vs. T = 19% pCR, p&gt;0.2; OR 1.84, 95% CI 0.74-4.55). When tumors were divided in hormone receptor (HR)-positive and HR-negative groups, total levels of HER2 still predicted response to T or T+L.

Conclusions: Increasing HER2 protein expression correlated with increased benefit of adding L to T compared to T alone. In tumors above the median of HER2 expression, the levels of HER2 predicted for response to both T and T+L. Our interpretation is that, in the neoadjuvant setting, the association between p95HER2 expression and response to anti-HER2 therapy is likely a consequence of the correlation between p95HER2 and total HER2 levels. HER2 expression seems to be a stronger predictor of pCR than p95HER2 for response to T, L and especially, T+L. Future studies to understand the impact of p95HER2 and HER2 expression on disease-free and overall survival following anti-HER2 therapy are warranted.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-08-42.

Clinical benefit of lapatinib-based therapy in patients with human epidermal growth factor receptor 2-positive breast tumors coexpressing the truncated p95HER2 receptor

PURPOSE

A subgroup of human epidermal growth factor receptor 2 (HER2)-overexpressing breast tumors coexpresses p95HER2, a truncated HER2 receptor that retains a highly functional HER2 kinase domain but lacks the extracellular domain and results in intrinsic trastuzumab resistance. We hypothesized that lapatinib, a HER2 tyrosine kinase inhibitor, would be active in these tumors. We have studied the correlation between p95HER2 expression and response to lapatinib, both in preclinical models and in the clinical setting.

EXPERIMENTAL DESIGN

Two different p95HER2 animal models were used for preclinical studies. Expression of p95HER2 was analyzed in HER2-overexpressing breast primary tumors from a first-line lapatinib monotherapy study (EGF20009) and a second-line lapatinib in combination with capecitabine study (EGF100151). p95HER2 expression was correlated with overall response rate (complete + partial response), clinical benefit rate (complete response + partial response + stable disease > or =24 wk), and progression-free survival using logistic regression and Cox proportional hazard models.

RESULTS

Lapatinib inhibited tumor growth and the HER2 downstream signaling of p95HER2-expressing tumors. A total of 68 and 156 tumors from studies EGF20009 and EGF100151 were evaluable, respectively, for p95HER2 detection. The percentage of p95HER2-positive patients was 20.5% in the EGF20009 study and 28.5% in the EGF100151 study. In both studies, there was no statistically significant difference in progression-free survival, clinical benefit rate, and overall response rate between p95HER2-positive and p95HER2-negative tumors.

CONCLUSIONS

Lapatinib as a monotherapy or in combination with capecitabine seems to be equally effective in patients with p95HER2-positive and p95HER2-negative HER2-positive breast tumors.