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PARP inhibitors (PARPi) are approved drugs for platinum-sensitive, high-grade serous ovarian cancer (HGSOC) and for breast, prostate, and pancreatic cancers (PaC) harboring genetic alterations impairing homologous recombination repair (HRR). Detection of nuclear RAD51 foci in tumor cells is a marker of HRR functionality, and we previously established a test to detect RAD51 nuclear foci. Here, we aimed to validate the RAD51 score cut off and compare the performance of this test to other HRR deficiency (HRD) detection methods. Laboratory models from BRCA1/BRCA2-associated breast cancer, HGSOC, and PaC were developed and evaluated for their response to PARPi and cisplatin. HRD in these models and patient samples was evaluated by DNA sequencing of HRR genes, genomic HRD tests, and RAD51 foci detection. We established patient-derived xenograft models from breast cancer (n = 103), HGSOC (n = 4), and PaC (n = 2) that recapitulated patient HRD status and treatment response. The RAD51 test showed higher accuracy than HRR gene mutations and genomic HRD analysis for predicting PARPi response (95%, 67%, and 71%, respectively). RAD51 detection captured dynamic changes in HRR status upon acquisition of PARPi resistance. The accuracy of the RAD51 test was similar to HRR gene mutations for predicting platinum response. The predefined RAD51 score cut off was validated, and the high predictive value of the RAD51 test in preclinical models was confirmed. These results collectively support pursuing clinical assessment of the RAD51 test in patient samples from randomized trials testing PARPi or platinum-based therapies.Significance:This work demonstrates the high accuracy of a histopathology-based test based on the detection of RAD51 nuclear foci in predicting response to PARPi and cisplatin.

Supplementary Table from Preclinical In Vivo Validation of the RAD51 Test for Identification of Homologous Recombination-Deficient Tumors and Patient Stratification

Supplementary Data from Preclinical In Vivo Validation of the RAD51 Test for Identification of Homologous Recombination-Deficient Tumors and Patient Stratification

Supplemental Methods. Methods used to generate supplemental data

Supplemental Figure 3. HGF and HGFAC expression in RCC-43b and RCC-47

Supplemental Figure 2. MET copy number in RCC-43 tumors from passage 6 and 9, and in RCC-47 tumors from passage 5 and 10 by qPCR

Purpose: Papillary renal cell carcinoma (PRCC) is the second most common cancer of the kidney and carries a poor prognosis for patients with nonlocalized disease. The HGF receptor MET plays a central role in PRCC and aberrations, either through mutation, copy number gain, or trisomy of chromosome 7 occurring in the majority of cases. The development of effective therapies in PRCC has been hampered in part by a lack of available preclinical models. We determined the pharmacodynamic and antitumor response of the selective MET inhibitor AZD6094 in two PRCC patient-derived xenograft (PDX) models.Experimental Design: Two PRCC PDX models were identified and MET mutation status and copy number determined. Pharmacodynamic and antitumor activity of AZD6094 was tested using a dose response up to 25 mg/kg daily, representing clinically achievable exposures, and compared with the activity of the RCC standard-of-care sunitinib (in RCC43b) or the multikinase inhibitor crizotinib (in RCC47).Results: AZD6094 treatment resulted in tumor regressions, whereas sunitinib or crizotinib resulted in unsustained growth inhibition. Pharmacodynamic analysis of tumors revealed that AZD6094 could robustly suppress pMET and the duration of target inhibition was dose related. AZD6094 inhibited multiple signaling nodes, including MAPK, PI3K, and EGFR. Finally, at doses that induced tumor regression, AZD6094 resulted in a dose- and time-dependent induction of cleaved PARP, a marker of cell death.Conclusions: Data presented provide the first report testing therapeutics in preclinical in vivo models of PRCC and support the clinical development of AZD6094 in this indication. Clin Cancer Res; 21(12); 2811–9. ©2015 AACR.

Supplemental Figure 1. In vitro activity of AZD6094, sunitinib, crizotinib, SGX-523, JNJ3887605, PHA-665752, and INC280 in AGS and GTL16 gastric cancer cells

Supplemental Table 1. Genes with copy number gain in RCC-43b and RCC-47

Supplementary Figure from Preclinical In Vivo Validation of the RAD51 Test for Identification of Homologous Recombination-Deficient Tumors and Patient Stratification

Supplemental Table 2. Mutations in RCC-43b and RCC-47

Despite considerable progress in understanding the biology and genetics of breast cancer, the development of effective therapies needs physiological and predictive preclinical models. In this context, breast cancer (BC) patient-derived xenograft (PDX) models have become a standard tool as they reproduce the biology of tumors of origin, in term of histology, genotype and response to chemotherapy. They have proven their relevance in the study of pathways leading to the development and progression of cancer, to the mechanisms linked to tumor resistance and to the identification of novel effective therapies. We present a preclinical platform of over 60 fully characterized BC PDX models and their in vitro cell derivatives for preclinical evaluation of new treatment modalities. Our platform consists of a PDX collection of 43 TNBC, 6 ER+, 4 HER2+, 6 Luminal B models (ER+ HER2+) and 14 cellular models derived from these PDXs, representing the variety of BC. PDX models were obtained by transplantation of post-surgery tumor specimens either by grafting of tumor fragments in the interscapular region of nude mice or by injection of tumor cells into the fat pad of NOD-Scid mice. Molecular analyses were done included gene expression, gene copy number, whole exome sequencing and IHC markers staining. In vivo drug efficacy assays were performed with standards of care as single agent or in combinations. This PDX panel mostly reflects the molecular heterogeneity of breast cancer and reproduce accurately the molecular and drug response profile of human tumors. It provides an invaluable tool for translational research. It is widely used to performed standard drug evaluation but also “Mouse Clinical Trials” (MCT) in vivo screens to provide more predictive preclinical data on single-agent or combination drug efficacy. Engrafted on highly immunodeficient mice humanized with human PBMCs or CD34+ cells, these PDX models allow bispecific T-Cell engager antibody testing or immune-checkpoint inhibitors evaluation. In addition to these PDX panel, we derived cellular models (PDXDCs) to offer a time- and cost-effective preclinical screening tool. PDXDCs were obtained from dissociated PDX tumors cultured under different media and matrix conditions. They were characterized by comparison with the parental PDX by Short Tandem Repeat (STR) profiling before performing a master bank. WES and RNASeq molecular analyses were done and in vitro drug sensitivity was compared with their parental PDX in vivo drug response. Overall, the results show that this PDXDC panel reproduced in vitro the in vivo drug response profile of the original PDXs with various therapies. This BC PDX panel and in vitro cell derivatives provide a powerful preclinical platform to improve our knowledge on BC biology and to rapidly evaluate response to new treatments and translate this knowledge to the clinic. Citation Format: Delphine Nicolle, Aurore Gorce, Marie Tavernier, Elisabetta Marangoni, Didier Decaudin, Christophe Ginestier, Emmanuelle Charafe-Jaufret, Judith Passildas, Nina Robin, Robert Clarke, Erwan Corcuff, Anaïs Joachim, Bernard Malissen, Ana Zarubica, Hervé Luche, Jean-Gabriel Judde, Olivier Déas. A preclinical platform of breast cancer PDX and derived cellular models as a tool for pharmacological screening and functional studies. [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 4677.

Background Several selective FGFR inhibitors have been developed for the treatment of FGFR-driven urothelial cancer, in particular erdafitinib which received FDA and EMA approval. Molecular mechanisms responsible for resistance to FGFR inhibitors have not been elucidated in urothelial cancer. Understanding these resistance mechanisms is crucial for the development of novel agents and treatment strategies. Methods We identified patients with metastatic urothelial cancer harboring FGFR mutations or rearrangements, treated with selective FGFR inhibitors in the MATCH-R (NCT02517892), MOSCATO (NCT01566019), STING-UNLOCK (NCT04932525), and CTC studies at Gustave Roussy. Post-progression tissue biopsies and circulating tumor DNA (ctDNA) were analyzed with whole exome sequencing and Illumina or FoundationOne assays, respectively. We generated Ba/F3 models containing FGFR3::TACC3 transcript with the FGFR3 kinase domain mutations detected in post-progression samples and exposed them to eight FGFR inhibitors (readouts: cell viability assays and Western blots). We established patient-derived xenografts (PDX) and cell lines to assess resistance mechanisms and perform pharmacological studies. Results Twenty-one patients with post-progression samples (n = 13 both tissue and ctDNA, n = 5 ctDNA only, n = 3 tissue only) were included in our study. The molecular driver was identified as FGFR3 mutations/fusions in 19 cases, whereas one FGFR4 mutation and one FGFR2 rearrangement were found in two patients. Patients progressed to erdafitinib (n = 14), futibatinib (n = 4) or pemigatinib (n = 3). Thirteen, six, and two patients experienced response, stable disease, and progression, respectively. At progression, we detected single mutations in the FGFR kinase domain in six (29%) patients (FGFR3 N540K, V553L, V553M, V555L, V555M, E587Q; FGFR2 L551F) and multiple mutations in one (5%) case (FGFR3 N540K, V555L, L608V). Using Ba/F3 cells, we confirmed that the detected mutations conferred resistance to FGFR inhibitors. FGFR3 V553L, emerging in a patient treated with pemigatinib, was sensitive to erdafitinib and futibatinib. We detected alterations in the mTOR pathway in 11 (52%) patients (n = 5 TSC1/2, n = 5 PIK3CA, n = 1 NF2, n = 1 PTEN), with or without FGFR3 kinase domain mutations. In patient-derived models, erdafitinib combined with pictilisib was synergic in the presence of PIK3CA E545K, while erdafitinib-gefitinib combination overcame bypass resistance mediated by EGFR activation. Conclusions We detected a high frequency of FGFR kinase domain mutations at progression to selective FGFR inhibitors in urothelial cancer. Unlike FGFR2-driven cholangiocarcinoma, polyclonality of FGFR3 kinase domain mutations does not seem to be a hallmark of FGFR-driven urothelial cancer. The identification of off-target events and the preclinical validation sustain the potential clinical applicability of combinatorial treatment strategies. Citation Format: Francesco Facchinetti, Antoine Hollebecque, Floriane Braye, Damien Vasseur, Yoann Pradat, Rastislav Bahleda, Cédric Pobel, Ludovic Bigot, Olivier Déas, Juan-David Florez-Arango, Giorgia Guaitoli, Hayato Mizuta, David Combarel, Lambros Tselikas, Stefan Michiels, Sergey Nikolaev, Jean-Yves Scoazec, Santiago Ponce-Aix, Benjamin Besse, Ken A. Olaussen, Yohann Loriot, Luc Friboulet. Resistance to selective FGFR inhibitors in FGFR-driven urothelial cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3458.

DNA damage and genomic instability contribute to non-small cell lung cancer (NSCLC) etiology and progression. However, their therapeutic exploitation is disappointing. CTC-derived explants (CDX) offer systems for mechanistic investigation of CTC metastatic potency and may provide rationale for biology-driven therapeutics. Four CDX models and 3 CDX-derived cell lines were established from NSCLC CTCs and recapitulated patient tumor histology and response to platinum-based chemotherapy. CDX (GR-CDXL1, GR-CDXL2, GR-CDXL3, GR-CDXL4) demonstrated considerable mutational landscape similarity with patient tumor biopsy and/or single CTCs. Truncal alterations in key DNA damage response (DDR) and genome integrity-related genes were prevalent across models and assessed as therapeutic targets in vitro, in ovo, and in vivo. GR-CDXL1 presented homologous recombination deficiency linked to biallelic BRCA2 mutation and FANCA deletion, unrepaired DNA lesions after mitosis, and olaparib sensitivity, despite resistance to chemotherapy. SLFN11 overexpression in GR-CDXL4 led to olaparib sensitivity and was in coherence with neuroendocrine marker expression in patient tumor biopsy, suggesting a predictive value of SLFN11 in NSCLC histological transformation into small cell lung cancer (SCLC). Centrosome clustering promoted targetable chromosomal instability in GR-CDXL3 cells. These CDX unravel DDR and genome integrity-related defects as a central mechanism underpinning metastatic potency of CTCs and provide rationale for their therapeutic targeting in metastatic NSCLC.

PARP inhibitors (PARPi) are approved drugs for platinum-sensitive, high-grade serous ovarian cancer (HGSOC) and for breast, prostate, and pancreatic cancers (PaC) harboring genetic alterations impairing homologous recombination repair (HRR). Detection of nuclear RAD51 foci in tumor cells is a marker of HRR functionality, and we previously established a test to detect RAD51 nuclear foci. Here, we aimed to validate the RAD51 score cut off and compare the performance of this test to other HRR deficiency (HRD) detection methods. Laboratory models from BRCA1/BRCA2-associated breast cancer, HGSOC, and PaC were developed and evaluated for their response to PARPi and cisplatin. HRD in these models and patient samples was evaluated by DNA sequencing of HRR genes, genomic HRD tests, and RAD51 foci detection. We established patient-derived xenograft models from breast cancer (n = 103), HGSOC (n = 4), and PaC (n = 2) that recapitulated patient HRD status and treatment response. The RAD51 test showed higher accuracy than HRR gene mutations and genomic HRD analysis for predicting PARPi response (95%, 67%, and 71%, respectively). RAD51 detection captured dynamic changes in HRR status upon acquisition of PARPi resistance. The accuracy of the RAD51 test was similar to HRR gene mutations for predicting platinum response. The predefined RAD51 score cut off was validated, and the high predictive value of the RAD51 test in preclinical models was confirmed. These results collectively support pursuing clinical assessment of the RAD51 test in patient samples from randomized trials testing PARPi or platinum-based therapies. Significance: This work demonstrates the high accuracy of a histopathology-based test based on the detection of RAD51 nuclear foci in predicting response to PARPi and cisplatin.

Prostate Cancer (PCa) is the most frequently diagnosed cancer in men and remains one of the leading causes of cancer death worldwide. It is a highly heterogenous and complex disease, presenting serious challenges to preclinical drug development and biomedical research. Prostate normal development, growth and function, as well as most of its pathological drifts, are associated to androgen receptor (AR) pathway regulation. Most patients subjected to androgen deprivation therapy (ADT) respond well to the treatment, however they usually progress into intractable castration-resistant PCa (CRPC) within 2 to 3 years. Therefore, understanding the mechanisms of castration resistance underlying PCa progression is key to develop future therapies. Patient-Derived Xenografts (PDX) are mouse models that recapitulate the disease more faithfully than any other in vivo model in terms of histopathologic, genomic and metastatic features, facilitating the translation of preclinical results in the clinical setting. PCa PDXs are challenging to develop, and only few are available to the scientific community. This lack of relevant preclinical models is a major limitation in PCa research. In particular, the development of PCa PDX models from castration-resistant tumors to explore new treatments against CRPC is a requirement. To fill this gap, XenTech and Gustave Roussy Institute are collaborating to develop a panel of PCa PDX models. In the framework of the MATCH-R clinical trial (NCT02517892), in which patients with disease progression under treatment are enrolled and switched to new targeted therapy based on the genetic alterations identified in biopsies, 8 PCa PDXs have been developed from metastatic lesions biopsy. In addition, we developed a PCa PDX model from circulating tumor cells (CTCs) obtained by leukapheresis at diagnosis. These 9 models, plus 4 PCa PDXs previously developed at XenTech, increases our PCa PDX panel to 13 models. All models were characterized at molecular level by whole exome and RNA sequencing and pharmacologically for response to standards of care, physical castration and response to the androgen receptor inhibitor enzalutamide. This PDX collection is a valuable preclinical tool to identify pivotal mechanisms underlying acquired resistance to current therapies and develop novel treatment strategies against PCa and CRPC. Citation Format: Laura Brulle-Soumare, Ludovic Bigot, Katell Mevel, Enora Le Ven, Luc Friboulet, Benjamin Besse, Françoise Farace, Jean Gabriel Judde, Stefano Cairo, Yohann Loriot, Olivier Déas. Molecular and pharmacological profiling of a novel prostate cancer-derived xenograft panel to identify resistance mechanisms and new therapeutic options [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 3113.

Significant rational is available for specific targeting of PI3K/AKT/mTOR pathway in the treatment of non-small cell lung cancer (NSCLC). However, almost all clinical trials that have evaluated Pi3K pathway-based monotherapies/combinations did not observe an improvement of patient’s outcome. The aim of our study was therefore to define combination of treatment based on the determination of predictive markers of resistance to the mTORC1 inhibitor RAD001/Everolimus. An in vivo study showed high efficacy of RAD001 in NSCLC Patient-Derived Xenografts (PDXs). When looking at biomarkers of resistance by RT-PCR study, three genes were found to be highly expressed in resistant tumors, i.e., PLK1, CXCR4, and AXL. We have then focused our study on the combination of RAD001 + Volasertib, a PLK1 inhibitor, and observed a high antitumor activity of the combination in comparison to each monotherapy; similarly, a clear synergistic effect between the two compounds was found in an in vitro study. Pharmacodynamics study demonstrated that this synergy was due to (1) tumor vascularization decrease, increase of the HIF1 protein expression and decrease of the intracellular pH, and (2) decrease of the Carbonic Anhydrase 9 (CAIX) protein that could not correct intracellular acidosis. In conclusion, all these preclinical data strongly suggest that the inhibition of mTORC1 and PLK1 proteins may be a promising therapeutic approach for NSCLC patients.

Identification of new treatments for relapsing pediatric cancer is an unmet clinical need and a societal challenge. Liver cancer occurrence in infancy, 1.5 for million children per year, falls far below the threshold of interest for dedicated drug development programs, and this disease is so rare that it is very difficult to gather enough children into a phase II clinical trial. Here, we present the establishment of an unprecedented preclinical platform of 24 pediatric liver cancer patient-derived xenografts (PLC-PDXs) from 20 hepatoblastomas (HBs), 1 transitional liver cell tumor (TCLT), 1 hepatocellular carcinoma, and 2 malignant rhabdoid tumors. Cytogenetic array and mutational analysis of the parental tumors and the corresponding PLC-PDXs show high conservation of the molecular features of the parental tumors. The histology of PLC-PDXs is strikingly similar to that observed in primary tumors and recapitulates the heterogeneity of recurrent disease observed in the clinic. Tumor growth in the mouse is strongly associated with elevated circulating alpha-fetoprotein (AFP), low rate of necrosis/fibrosis after treatment, and gain of chromosome 20, all indicators of resistance to chemotherapy and poor outcome. Accordingly, the ability of a tumor to generate PLC-PDX is predictive of poor prognosis. Exposure of PLC-PDXs to standards of care or therapeutic options already in use for other pediatric malignancies revealed unique response profiles in these models. Among these, the irinotecan/temozolomide combination induced strong tumor regression in the TCLT and in a model derived from an AFP-negative relapsing HB. Conclusion: These results provide evidence that PLC-PDX preclinical platform can strongly contribute to accelerate the identification and diversification of anticancer treatment for aggressive subtypes of pediatric liver cancer. (Hepatology 2016;64:1121-1135)

Identification of new treatments for relapsing pediatric cancer is an unmet clinical need and a societal challenge. Hepatoblastoma (HB) is a rare tumor that constitutes the most frequent form of childhood liver cancer. Current improvement in medical care allows 80% of children to survive this disease, but no second line treatment is available at relapse, so that 20% will not survive. Patient population small size and very low mutation rate besides beta-catenin activating mutation, which is at present undruggable, make HB an orphan disease. Very few anti-cancer drugs evaluated for adult diseases are investigated in the pediatric population, with 12 drugs approved for adult cancers every year against 6 drugs approved in childhood cancer since 1978. The need of incentives to encourage pharmaceutical industry to invest in this field has been well received by the European and US medicine agencies, and recent modification to regulations on adult and pediatric oncology drug development are expected to induce pharmaceutical companies to test their new compounds in the pediatric setting. Parallel to this initiative, it is imperative that the scientific community develops research tools and scientific rational to assist drug development as well as repositioning of drugs already approved in adult cancers. To this aim, in collaboration with the International Childhood Liver Tumour Strategy Group (SIOPEL) and the network of hospitals in the Paris area (AP-HP), XenTech has launched in 2010 the development of a panel of HB patient-derived xenografts (HB-PDXs). To date, 26 HB-PDXs have been established from 80 engraftments from patients at surgery after chemotherapy or at relapse. As these models were established from tumor cells that either evaded chemotherapy or promoted local and distant metastases, they present a biological surrogate of the recurrent disease. From these PDXs, 9 cellular models have been established to allow the exploration of the functional mechanisms of tumor growth and resistance to treatment, as well as to facilitate drug screening. This project is receiving worldwide participation from the HB scientific community including clinicians, academic researchers and parents associations. Thanks to this joint effort all the models are now fully characterized at the molecular level, PDXs pharmacological profiling has been done and is currently ongoing for many of these models, and PDXs and cellular models are being used from a growing number of collaborators to perform 3D culture, to improve our knowledge on the HB biology and to identify new drugs. The ambition of this project is to generate a reference preclinical platform that will be used for research purposes by the academic community and as a testing site for biotechs and pharmaceutical companies to accelerate the identification of anti-cancer therapies for children with aggressive HB. Citation Format: Carolina Armengol, Roland Kappler, Liqin Zhu, Nikolai Timchenko, Dina Kats, Charles Keller, Lisa Howard, Christophe Grosset, Delphine Nicolle, Olivier Déas, Martina Pigazzi, Laurence Brugières, Charlotte Mussini, Louise Galmiche-Rolland, Christophe Chardot, Sophie Brancereau, Jean-Gabriel Judde, Stefano Cairo. A scientific task force to generate proof-of-concept data packages for clinical trials in pediatric cancers: The hepatoblastoma example [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 3107.

Poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi) have recently emerged as therapeutic options for patients with homologous recombination-deficient (HRD) breast or ovarian cancer, two heterogeneous diseases associated with high mortality rates. As shown in several clinical studies, patient response to PARPi is invariably followed by eventual mid-long term resistance and progression under treatment. The molecular processes contributing to PARPi-resistance are at present under-explored. Therefore, a huge effort is being made to better understand how to overcome resistance and to identify ad-hoc combinations with other targeted therapies to improve tumor response and extend progression-free survival. We have previously published the PARPi-response profile of a panel of 40 breast cancer (BC) patient-derived xenografts (PDXs). The models tested showed heterogeneous response to PARPi, and only partial association with the genomic status of BRCA genes, the only currently acknowledged clinical marker to select patients that can benefit from PARPi administration. Although these models are ideal preclinical tools for the evaluation of drug combinations to improve tumor response to PARPi as single agent, the use of these models for early preclinical evaluation of combination efficacy is not straightforward in reason of the limited throughput and of the ethical issue with respect of the 3Rs. The use of cellular models is still considered as a standard early preclinical test to evaluate drug response before moving to in vivo assays. However, the main concern when using in vitro models is the representativeness of the results obtained when transposed to in vivo models. In this study, we have setup an in vitro assay that recapitulates the response to PARPi observed in vivo in our BC PDXs, with particular focus on the models that show resistance to PARPi. To this aim we generated 9 cellular models from 9 BC PDX models: HBCx-2, HBCx-3, HBCx-6, HBCx-8, HBCx-9, HBCx-17, HBCx-19, HBCx-39 and T174. Two cellular models (HBCx-3, and HBCx-19) were established from ER+ BC PDX and 7 from ER- BC PDXs and two models, HBCx-8 and HBCx-17, harbor BRCA1 and BRCA2 mutation, respectively. Seven out of 9 models are resistant to PARPi in vivo, with HBCx-6 PDX showing partial tumor regression and HBCx-17 PDX showing tumor stabilization upon treatment. Several different 2D-culture experimental conditions, namely different cell growth conditions, drug concentrations, duration of cell exposure to drugs, time points and readouts, have been tested to evaluate response to olaparib. The results showed that a 2D colony assay is the best experimental strategy to faithfully evaluate tumor cell sensitivity, minimizing the false positive results when compared to the in vivo data.. This cell panel will be used to identify combination of PARPi with a library of FDA-approved targeted therapy to identify the treatments to be moved forward in vivo. Citation Format: Olivier Déas, Romain Rousseau, Sophie Banis, Kathleen Flosseau, Enora Le Ven, Jean-Gabriel Judde, stefano cairo. Establishment of an in vitro assay that phenocopies tumor response to PARP inhibitors in vivo [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 3810.

The last 20 years have witnessed the identification of an increasing number of actionable oncogenic drivers and the development and clinical use of specific inhibitors against these targets. Unfortunately, patients treated with targeted therapies consistently develop resistance and progression under treatment. Hence, important scientific, pharmaceutical and medical research efforts are directed towards understanding the mechanisms of acquired resistance to explore new therapeutic pathways. The MATCH-R clinical trial enrolls patients with oncogene-driven cancer who have had previous clinical response to targeted therapy and subsequently experienced disease progression. In the framework of this project, Gustave Roussy and XenTech are joining forces to develop a panel of patient-derived xenografts (PDXs) derived from biopsies collected from these patients at the stage of acquired resistance. These PDX models will be fully characterized at molecular and pharmacological level and used to improve knowledge on the mechanisms underlying resistance to treatment and to evaluate response to new treatments. In this perspective, the development of 75 PDX-AR (Acquired Resistance) models is planned over 3 years. All the models are maintained under the same therapeutic pressure the parental tumor was submitted to at the time of biopsy, and will be subjected to extensive phenotypic and genotypic characterization. To favor successful xenograft establishment, the first two passages are performed without drug treatment, which is applied from the third passage on. When doing so, we observed 3 types of response: some models showed resistance from the first passage under treatment, some showed stabilization under treatment at the first passages and rapidly acquired resistance over passages, and others showed sensitivity to treatment, whereas the patient tumor showed progression under the same treatment. These different behaviors might be due to different mechanisms of resistance, irreversible for the former, reversible for the two latter, as well as to suboptimal correlation of the clinical dose with the one used in mice. An example of such discrepancies has been found in two models of NSCLC PDX obtained from two metastases from a patient treated by a ROS1 and ALK inhibitor. While LCx-MR135PD2-AR PDX does not respond to the treatment, the LCx-MR135PD1 model is highly sensitive. As both metastases were progressing under treatment in the patient, molecular and pharmacological comparative analysis of these two models will investigate these discrepancy and provide important insights into the mechanisms of resistance to such inhibitors. Overall, the MatchR PDX project will provide a unique preclinical platform to identify resistance mechanisms to current targeted therapies and to develop next generation therapeutic strategies. Citation Format: Olivier Déas, Ludovic Bigot, Emilie Dasse, Guillaume Lang, Yohann Loriot, Fabrice Andre, Jean-Charles Soria, Benjamin Besse, Stefano Cairo, Marie Tavernier, Katell Mevel, Enora Le Ven, Jean-Gabriel Judde, Luc Friboulet. Generation of a fully characterized preclinical PDX panel to accelerate the identification of next generation treatments for patients with acquired resistance to targeted therapies [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 2122.

Activating mutations in NOTCH1, an essential regulator of T cell development, are frequently found in human T cell acute lymphoblastic leukemia (T-ALL). Despite important advances in our understanding of Notch signal transduction, the regulation of Notch functions in the nucleus remains unclear. Using immunoaffinity purification, we identified NOTCH1 nuclear partners in T-ALL cells and showed that, beyond the well-characterized core activation complex (ICN1-CSL-MAML1), NOTCH1 assembles a multifunctional complex containing the transcription coactivator AF4p12, the PBAF nucleosome remodeling complex, and the histone demethylases LSD1 and PHF8 acting through their demethylase activity to promote epigenetic modifications at Notch-target genes. Remarkably, LSD1 functions as a corepressor when associated with CSL-repressor complex and as a NOTCH1 coactivator upon Notch activation. Our work provides new insights into the molecular mechanisms that govern Notch transcriptional activity and represents glimpse into NOTCH1 interaction landscape, which will help in deciphering mechanisms of NOTCH1 functions and regulation.

Purpose: Papillary renal cell carcinoma (PRCC) is the second most common cancer of the kidney and carries a poor prognosis for patients with nonlocalized disease. The HGF receptor MET plays a central role in PRCC and aberrations, either through mutation, copy number gain, or trisomy of chromosome 7 occurring in the majority of cases. The development of effective therapies in PRCC has been hampered in part by a lack of available preclinical models. We determined the pharmacodynamic and antitumor response of the selective MET inhibitor AZD6094 in two PRCC patient-derived xenograft (PDX) models. Experimental Design: Two PRCC PDX models were identified and MET mutation status and copy number determined. Pharmacodynamic and antitumor activity of AZD6094 was tested using a dose response up to 25 mg/kg daily, representing clinically achievable exposures, and compared with the activity of the RCC standard-of-care sunitinib (in RCC43b) or the multikinase inhibitor crizotinib (in RCC47). Results: AZD6094 treatment resulted in tumor regressions, whereas sunitinib or crizotinib resulted in unsustained growth inhibition. Pharmacodynamic analysis of tumors revealed that AZD6094 could robustly suppress pMET and the duration of target inhibition was dose related. AZD6094 inhibited multiple signaling nodes, including MAPK, PI3K, and EGFR. Finally, at doses that induced tumor regression, AZD6094 resulted in a dose- and time-dependent induction of cleaved PARP, a marker of cell death. Conclusions: Data presented provide the first report testing therapeutics in preclinical in vivo models of PRCC and support the clinical development of AZD6094 in this indication. Clin Cancer Res; 21(12); 2811–9. ©2015 AACR.