The mutational landscape of skull base and spinal chordomas and the identification of potential prognostic and theranostic biomarkers

OBJECTIVE

Chordomas are rare bone neoplasms characterized by a high recurrence rate and no benefit from any approved medical treatment to date. However, the investigation of molecular alterations in chordomas could be essential to prognosticate, guide clinical decision-making, and identify theranostic biomarkers. The aim of this study was to provide a detailed genomic landscape of a homogeneous series of 64 chordoma samples, revealing driver events, theranostic markers, and outcome-related genomic features.

METHODS

The authors conducted whole-exome sequencing (WES), targeted next-generation sequencing, and RNA sequencing of 64 skull base and spinal chordoma samples collected between December 2006 and September 2020. Clinical, histological, and radiological data were retrospectively analyzed and correlated to genetic findings.

RESULTS

The authors identified homozygous deletions of CDKN2A/2B, PIK3CA mutations, and alterations affecting genes of SWI/SNF chromatin remodeling complexes (PBRM1 and ARID1A) as potential theranostic biomarkers. Using matched germline WES, they observed a higher frequency of a common genetic variant (rs2305089; p.(Gly177Asp)) in TBXT (97.8%, p < 0.001) compared to its distribution in the general population. PIK3CA mutation was identified as an independent biomarker of short progression-free survival (HR 10.68, p = 0.0008). Loss of CDKN2A/2B was more frequently observed in spinal tumors and recurrent tumors.

CONCLUSIONS

In the current study, the authors identified driver events such as PBRM1 and PIK3CA mutations, TBXT alterations, or homozygous deletions of CDKN2A/2B, which could, for some, be considered potential theranostic markers and could allow for identifying novel therapeutic approaches. With the aim of a future biomolecular prognostication classification, alterations affecting PIK3CA and CDKN2A/2B could be considered as poor prognostic biomarkers.

HORMAD1 overexpression predicts response to anthracycline-cyclophosphamide and survival in triple-negative breast cancers

Triple negative breast cancers (TNBCs) represent 15-20% of all breast cancers and are associated with higher recurrence and distant metastasis rate. Standard of care for early stage TNBC is anthracyclines combined with cyclophosphamide (AC) followed by taxanes, in the neo-adjuvant or adjuvant setting. This work aimed to identify predictive biomarkers of AC response in patient-derived xenograft (PDX) models of TNBC and to validate them in the clinical setting. By gene and protein expression analysis of 39 PDX with different responses to AC, we found that high expression of HORMAD1 was associated with better response to AC. Both gene and protein expression were associated with promoter hypomethylation. In a cohort of 526 breast cancer patients, HORMAD1 was overexpressed in 71% of TNBC. In a second cohort of 186 TNBC patients treated with AC, HORMAD1 expression was associated with longer metastasis-free survival (MFS). In summary, HORMAD1 overexpression was predictive of an improved response to AC in PDX and is an independent prognostic factor in TNBC patients treated with AC.

Oxidative phosphorylation is a metabolic vulnerability of endocrine therapy and palbociclib resistant metastatic breast cancers

Resistance to endocrine treatments and CDK4/6 inhibitors is considered a near-inevitability in most patients with estrogen receptor positive breast cancers (ER + BC). By genomic and metabolomics analyses of patients' tumours, metastasis-derived patient-derived xenografts (PDX) and isogenic cell lines we demonstrate that a fraction of metastatic ER + BC is highly reliant on oxidative phosphorylation (OXPHOS). Treatment by the OXPHOS inhibitor IACS-010759 strongly inhibits tumour growth in multiple endocrine and palbociclib resistant PDX. Mutations in the PIK3CA/AKT1 genes are significantly associated with response to IACS-010759. At the metabolic level, in vivo response to IACS-010759 is associated with decreased levels of metabolites of the glutathione, glycogen and pentose phosphate pathways in treated tumours. In vitro, endocrine and palbociclib resistant cells show increased OXPHOS dependency and increased ROS levels upon IACS-010759 treatment. Finally, in ER + BC patients, high expression of OXPHOS associated genes predict poor prognosis. In conclusion, these results identify OXPHOS as a promising target for treatment resistant ER + BC patients.

Homologous recombination deficiency derived from whole-genome sequencing predicts platinum response in triple-negative breast cancers

The high frequency of homologous recombination deficiency (HRD) is the main rationale of testing platinum-based chemotherapy in triple-negative breast cancer (TNBC), however, the existing methods to identify HRD are controversial and there is a medical need for predictive biomarkers. We assess the in vivo response to platinum agents in 55 patient-derived xenografts (PDX) of TNBC to identify determinants of response. The HRD status, determined from whole genome sequencing, is highly predictive of platinum response. BRCA1 promoter methylation is not associated with response, in part due to residual BRCA1 gene expression and homologous recombination proficiency in different tumours showing mono-allelic methylation. Finally, in 2 cisplatin sensitive tumours we identify mutations in XRCC3 and ORC1 genes that are functionally validated in vitro. In conclusion, our results demonstrate that the genomic HRD is predictive of platinum response in a large cohort of TNBC PDX and identify alterations in XRCC3 and ORC1 genes driving cisplatin response.

In vivo efficacy assessment of the CDK4/6 inhibitor palbociclib and the PLK1 inhibitor volasertib in human chordoma xenografts

Background

Management of advanced chordomas remains delicate considering their insensitivity to chemotherapy. Homozygous deletion of the regulatory gene CDKN2A has been described as the most frequent genetic alteration in chordomas and may be considered as a potential theranostic marker. Here, we evaluated the tumor efficacy of the CDK4/6 inhibitor palbociclib, as well as the PLK1 inhibitor volasertib, in three chordoma patient-derived xenograft (PDX) models to validate and identify novel therapeutic approaches.

Methods

From our chordoma xenograft panel, we selected three models, two of them harboring a homozygous deletion of CDKN2A/2B genes, and the last one a PBRM1 pathogenic variant (as control). For each model, we tested the palbociclib and volasertib drugs with pharmacodynamic studies together with RT-PCR and RNAseq analyses.

Results

For palbociclib, we observed a significant tumor response for one of two models harboring the deletion of CDKN2A/2B (p = 0.02), and no significant tumor response in the PBRM1-mutated PDX; for volasertib, we did not observe any response in the three tested models. RT-PCR and RNAseq analyses showed a correlation between cell cycle markers and responses to palbociclib; finally, RNAseq analyses showed a natural enrichment of the oxidative phosphorylation genes (OxPhos) in the palbociclib-resistant PDX (p = 0.02).

Conclusion

CDK4/6 inhibition appears as a promising strategy to manage advanced chordomas harboring a loss of CDKN2A/2B. However, further preclinical studies are strongly requested to confirm it and to understand acquired or de novo resistance to palbociclib, in the peculiar view of a targeting of the oxidative phosphorylation genes.

Abstract LB567: Dramatic in vivo efficacy of the EZH2-inhibitor tazemetostat in PBRM1-mutated human chordoma xenograft

Background: Chordomas are considered as rare bone neoplasms characterized by a high level of recurrence and a poor long-term prognosis. Considering their chemo-radio-resistance, alternative treatment strategies are therefore strongly requested, but their development is limited by the paucity of relevant preclinical models. Mutations affecting genes of the SWI/SNF complex including PBMR1 are frequently found in chordomas, suggesting a potential therapeutic effect of epigenetic regulators in this indication.

Methods: Thirty-eight chordoma specimens derived from primary patients’ tumors were grafted into nude mice. Relationship between grafted tumors and clinical, biological and therapeutic features of corresponding patients were investigated. We subjected the established PDX models to histopathological and genetic examination; finally, a therapeutic program focused on the EZH2-inhibition was performed in one PDX model.

Results: Twelve PDX models were established and characterized on histological and biomolecular features. Patients whose tumors were able to grow into mice had a statistically significant lower progression-free survival than those whose tumors did not grow after in vivo transplantation (p=0.007). All PDXs maintained the same histopathological features as patients’ tumors. Homozygous deletions of CDKN2A/2B (58.3%) and PBRM1 (25%) variants were the most common genomic alterations found. In the tazemetostat treated PDX model harboring a PBRM1 variant, an overall survival of 100% was observed.

Conclusion: Our panel of chordoma PDXs represents a useful preclinical tool for both pharmacologic and biological assessments. The first demonstration of a high antitumor activity of tazemetostat in a PDX model harboring a PBRM1variant supports further evaluation of EZH2-inhibitors in this subgroup of chordomas.

Citation Format: Thibault Passeri, Ahmed Dahmani, Julien Masliah-Planchon, Adnan Naguez, Marine Michou, Rania El-Botty, Sophie Vacher, Rachida Bouarich, André Nicolas, Marc Polivka, Coralie Franck, Anne Schnitzler, Fariba Némati, Sergio Roman-Roman, Franck Bourdeaut, Homa Adle-Biassette, Hamid Mammar, Sébastien Froelich, Ivan Bièche, Didier Decaudin. Dramatic in vivo efficacy of the EZH2-inhibitor tazemetostat in PBRM1-mutated human chordoma xenograft [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 LB567.

Abstract 649: Targeting progesterone receptor (PR) with the antiprogestin onapristone in patient-derived xenograft (PDX) models of estrogen receptor positive (ER+), PR positive (PR+) bone metastasis of breast cancer

Background: Onapristone (ONA) is a progesterone receptor (PR) antagonist that prevents PR-mediated DNA transcription. ONA is currently being evaluated in metastatic breast cancers (MBC), as well as other hormone-dependent cancers. Recently, therapeutic options for metastatic estrogen receptor (ER) positive breast cancers have been expanded by the introduction of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i), administered in combination with endocrine treatments, as first line therapy. Moreover, the selective PI3K inhibitor alpelisib (ALP) has been approved for the treatment of PIK3CA-mutated endocrine resistant MBC. The objective of this study was to evaluate the efficacy of ONA in combination with fulvestrant (FUL) and palbociclib (PAL) or ALP in different PDX models established from ER and PR positive breast cancers.

Methods: PDX models were established from primary tumors or biopsies from bone metastases from endocrine therapy patients with progressing tumors. ER and PR expression were analyzed by immunohistochemistry (IHC) and western blot (WB) analysis in 17 PDX models. The anti-tumor activity of onapristone alone or combined with FUL and PAL was tested in 2 ER+/PR+ PDX studies, while the combination with ALP+FUL was tested in one PIK3CA-mutated PDX study. Phosphorylation of both PR and ER-PR interactions were analyzed in treated tumors by WB and by the in situ Proximity Ligation Assay (PLA), respectively.

Results: PR expression was found in 1/9 PDX established from primary breast tumors and 4/8 PDX established from bone metastases. ONA in vivo activity was tested in 2 PDX of bone metastases: PDX BC1101 (PR low) and BC1117 (PR high). BC1101 showed amplification of FGFR1 and CCND1 genes, while BC1117 has an activating mutation of PIK3CA gene. In the low PR PDX BC1101, treatment with ONA was ineffective in both the monotherapy and combination setting. Conversely, in the PDX with high expression of PR, BC1117, ONA treatment, given as monotherapy, decreased tumor growth. The anti-tumor activity of ONA+FUL+PAL combination was significantly increased as compared to FUL+PAL, with the majority of xenografts showing tumor regression. Expression of PR and phospho-PR were inhibited in the tumors treated by FUL, ONA+FUL, and ONA+FUL+PAL. Interaction between ER and PR, analyzed by the in situ PLA assay, was inhibited in the ONA+FUL treated xenografts ±PAL. Finally, treatment with the triple combination of ONA+FUL+ALP was also highly effective and significantly greater than the combination of FUL+ALP. RNAseq analysis of treated xenografts is ongoing to identify transcriptomic changes in the different treatment arms. In conclusion, our study demonstrates that ONA improved the response to endocrine treatment using CDK4/6 or PI3K inhibitors in a MBC-derived PDX model with high PR expression.

Citation Format: Martin Lehr, Ahmed Dahmani, Léa Huguet, Rania El-Botty, Charlène Thiebaut, Muriel Romancer, Paul Cottu, Elisabetta Marangoni. Targeting progesterone receptor (PR) with the antiprogestin onapristone in patient-derived xenograft (PDX) models of estrogen receptor positive (ER+), PR positive (PR+) bone metastasis of breast cancer [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 649.

Abstract 3984: GATA3 and MDM2 are synthetic lethal in estrogen receptor-positive breast cancers

Introduction: GATA3 is critical for the development of the mammary gland and the loss of its expression alters the estrogen receptor (ER) transcriptional program. Approximately 70%-80% of all breast cancers are ER-positive and 15-18% of them harbor GATA3 somatic mutations. Clinically, GATA3 loss defines a subset of patients with poor response to hormonal therapy and poor prognosis. As a transcription factor, however, GATA3 is not pharmacologically targetable. Synthetic lethality refers to the interaction between genetic events in two genes whereby the inactivation of either gene results in a viable phenotype, while their combined inactivation is lethal. This approach enables the indirect targeting of undruggable genes by disrupting their genetic interactors. In this study we sought to define Synthetic lethal partners for GATA3 and explore possible therapeutic targets

Methods: Putative synthetic lethal partners for GATA3 were identified using the recently developed SLIdR (Synthetic Lethal Identification in R) algorithm. The synthetic lethal interaction and the anti-tumoral effect of putative partner was evaluated via genetic silencing or pharmacological inhibition using in-vitro, ex-vivo and in-vivo models. Putative mechanisms of action were investigate using RNA sequencing and confirmed using molecular biology technologies.

Results: We identify MDM2 as synthetically lethal partner of GATA3 in ER-positive breast cancer. Using a siRNA approach, we first validated in-silico data by confirming that silencing MDM2 significantly reduces cell proliferation of GATA3-mutant in-vitro models by inducing apoptosis. Pharmacological inhibition of MDM2 using three different compounds (RG7388-idasanutlin, RAIN-32 and MI-733) significantly impaired tumor growth in GATA3-deficient models in vitro, in vivo and in patient-derived organoid/xenograft (PDO/PDX) harboring GATA3 somatic mutation. Additionally, we showed that the synthetic lethality between GATA3 and MDM2 is p53-dependent and acts at least partially via the PI3K/Akt/mTOR pathway. This suggests that GATA3 loss-of-function (via genetic alterations or other mechanisms) activates the PI3K/Akt/mTOR pathway and leads to resistance to apoptosis.

Conclusion: Our results present MDM2 as a novel therapeutic target in the substantial cohort of ER-positive, GATA3-mutant breast cancer patients. With MDM2 inhibitors widely available, our findings can be rapidly translated into clinical trials to evaluate in-patient efficacy.

Citation Format: Mattia Marinucci, Gaia Bianco, Mairene Coto-Llierena, John Gallon, Venkatesh Kancherla, Federica Panebianco, Stephanie Taha-Mehlitz, Sumana Srivatsa, Niko Beerenwinkel, Hesam Montazeri, Vijaya Tirunagaru, Marta De Menna, Caner Ercan, Ahmed Dahmani, Elodie Montaudon, Marianna Kruithof-de Julio, Luigi M. Terracciano, Rinath M. Jeselsohn, Robert C. Doebele, François-Clément Bidard, Elisabetta Marangoni, Charlotte K. Y. Ng, Salvatore Piscuoglio. GATA3 and MDM2 are synthetic lethal in estrogen receptor-positive breast cancers [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 3984.

H3K27me3 conditions chemotolerance in triple-negative breast cancer

The persistence of cancer cells resistant to therapy remains a major clinical challenge. In triple-negative breast cancer, resistance to chemotherapy results in the highest recurrence risk among breast cancer subtypes. The drug-tolerant state seems largely defined by nongenetic features, but the underlying mechanisms are poorly understood. Here, by monitoring epigenomes, transcriptomes and lineages with single-cell resolution, we show that the repressive histone mark H3K27me3 (trimethylation of histone H3 at lysine 27) regulates cell fate at the onset of chemotherapy. We report that a persister expression program is primed with both H3K4me3 (trimethylation of histone H3 at lysine 4) and H3K27me3 in unchallenged cells, with H3K27me3 being the lock to its transcriptional activation. We further demonstrate that depleting H3K27me3 enhances the potential of cancer cells to tolerate chemotherapy. Conversely, preventing H3K27me3 demethylation simultaneously to chemotherapy inhibits the transition to a drug-tolerant state, and delays tumor recurrence in vivo. Our results highlight how chromatin landscapes shape the potential of cancer cells to respond to initial therapy.

Dramatic In Vivo Efficacy of the EZH2-Inhibitor Tazemetostat in PBRM1-Mutated Human Chordoma Xenograft

Simple Summary

Chordomas are rare bone tumors characterized by a high recurrence rate. Presently, no medical treatment is available for advanced diseases due to the lack of molecular data and preclinical models. The current study showed the establishment and characterization of the largest panel chordoma xenografts, allowing pharmacological studies. In one PBRM1-mutated model, we demonstrated a strong therapeutic efficacy of the EZH2-inhibitor tazemetostat, encouraging further research on EZH2-inhibitors in chordomas.

Abstract

Chordomas are rare neoplasms characterized by a high recurrence rate and a poor long-term prognosis. Considering their chemo-/radio-resistance, alternative treatment strategies are strongly required, but their development is limited by the paucity of relevant preclinical models. Mutations affecting genes of the SWI/SNF complexes are frequently found in chordomas, suggesting a potential therapeutic effect of epigenetic regulators in this pathology. Twelve PDX models were established and characterized on histological and biomolecular features. Patients whose tumors were able to grow into mice had a statistically significant lower progression-free survival than those whose tumors did not grow after in vivo transplantation (p = 0.007). All PDXs maintained the same histopathological features as patients’ tumors. Homozygous deletions of CDKN2A/2B (58.3%) and PBRM1 (25%) variants were the most common genomic alterations found. In the tazemetostat treated PDX model harboring a PBRM1 variant, an overall survival of 100% was observed. Our panel of chordoma PDXs represents a useful preclinical tool for both pharmacologic and biological assessments. The first demonstration of a high antitumor activity of tazemetostat in a PDX model harboring a PBRM1 variant supports further evaluation for EZH2-inhibitors in this subgroup of chordomas.

HRAS is a therapeutic target in malignant chemo-resistant adenomyoepithelioma of the breast

Malignant adenomyoepithelioma (AME) of the breast is an exceptionally rare form of breast cancer, with a significant metastatic potential. Chemotherapy has been used in the management of advanced AME patients, however the majority of treatments are not effective. Recent studies report recurrent mutations in the HRAS Q61 hotspot in small series of AMEs, but there are no preclinical or clinical data showing H-Ras protein as a potential therapeutic target in malignant AMEs. We performed targeted sequencing of tumours’ samples from new series of 13 AMEs, including 9 benign and 4 malignant forms. Samples from the breast tumour and the matched axillary metastasis of one malignant HRAS mutated AME were engrafted and two patient-derived xenografts (PDX) were established that reproduced the typical AME morphology. The metastasis-derived PDX was treated in vivo by different chemotherapies and a combination of MEK and BRAF inhibitors (trametinib and dabrafenib). All malignant AMEs presented a recurrent mutation in the HRAS G13R or G12S hotspot. Mutation of PIK3CA were found in both benign and malignant AMEs, while AKT1 mutations were restricted to benign AMEs. Treatment of the PDX by the MEK inhibitor trametinib, resulted in a marked anti-tumor activity, in contrast to the BRAF inhibitor and the different chemotherapies that were ineffective. Overall, these findings further expand on the genetic features of AMEs and suggest that patients carrying advanced HRAS-mutated AMEs could potentially be treated with MEK inhibitors.

mTOR Repression in Response to Amino Acid Starvation Promotes ECM Degradation Through MT1-MMP Endocytosis Arrest

Under conditions of starvation, normal and tumor epithelial cells can rewire their metabolism toward the consumption of extracellular proteins, including extracellular matrix-derived components as nutrient sources. The mechanism of pericellular matrix degradation by starved cells has been largely overlooked. Here it is shown that matrix degradation by breast and pancreatic tumor cells and patient-derived xenograft explants increases by one order of magnitude upon amino acid and growth factor deprivation. In addition, it is found that collagenolysis requires the invadopodia components, TKS5, and the transmembrane metalloproteinase, MT1-MMP, which are key to the tumor invasion program. Increased collagenolysis is controlled by mTOR repression upon nutrient depletion or pharmacological inhibition by rapamycin. The results reveal that starvation hampers clathrin-mediated endocytosis, resulting in MT1-MMP accumulation in arrested clathrin-coated pits. The study uncovers a new mechanism whereby mTOR repression in starved cells leads to the repurposing of abundant plasma membrane clathrin-coated pits into robust ECM-degradative assemblies.

The Nephroprotective Effect of Zizyphus lotus L. (Desf.) Fruits in a Gentamicin-Induced Acute Kidney Injury Model in Rats: A Biochemical and Histopathological Investigation

Zizyphus lotus L. (Desf.) (Z. lotus) is a medicinal plant largely distributed all over the Mediterranean basin and is traditionally used by Moroccan people to treat many illnesses, including kidney failure. The nephrotoxicity of gentamicin (GM) has been well documented in humans and animals, although the preventive strategies against it remain to be studied. In this investigation, we explore whether the extract of Zizyphus lotus L. (Desf.) Fruit (ZLF) exhibits a protective effect against renal damage produced by GM. Indeed, twenty-four Wistar rats were separated into four equal groups of six each (♂/♀ = 1). The control group was treated orally with distilled water (10 mL/kg); the GM treated group received distilled water (10 mL/kg) and an intraperitoneal injection of GM (80 mg/kg) 3 h after; and the treated groups received ZLF extract orally at the doses 200 or 400 mg/kg and injected intraperitoneally with the GM. All treatments were given daily for 14 days. At the end of the experiment, the biochemical parameters and the histological observation related the kidney function was explored. ZLF treatment has significantly attenuated the nephrotoxicity induced by the GM. This effect was indicated by its capacity to decrease significantly the serum creatinine, uric acid, urea, alkaline phosphatase, gamma-glutamyl-transpeptidase, albumin, calcium, sodium amounts, water intake, urinary volume, and relative kidney weight. In addition, this effect was also shown by the increase in the creatinine clearance, urinary creatinine, uric acid, and urea levels, weight gain, compared to the rats treated only with the GM. The hemostasis of oxidants/antioxidants has been significantly improved with the treatment of ZLF extract, which was shown by a significant reduction in malondialdehydes levels. Histopathological analysis of renal tissue was correlated with biochemical observation. Chemical analysis by HPLC-DAD showed that the aqueous extract of ZLF is rich in phenolic compounds such as 3-hydroxycinnamic acid, catechin, ferulic acid, gallic acid, hydroxytyrosol, naringenin, p- coumaric Acid, quercetin, rutin, and vanillic acid. In conclusion, ZLF extract improved the nephrotoxicity induced by GM, through the improvement of the biochemical and histological parameters and thus validates its ethnomedicinal use.

BRCAness, SLFN11, and RB1 loss predict response to topoisomerase I inhibitors in triple-negative breast cancers

Topoisomerase I (TOP1) inhibitors trap TOP1 cleavage complexes resulting in DNA double-strand breaks (DSBs) during replication, which are repaired by homologous recombination (HR). Triple-negative breast cancer (TNBC) could be eligible for TOP1 inhibitors given the considerable proportion of tumors with a defect in HR-mediated repair (BRCAness). The TOP1 inhibitor irinotecan was tested in 40 patient-derived xenografts (PDXs) of TNBC. BRCAness was determined with a single-nucleotide polymorphism (SNP) assay, and expression of Schlafen family member 11 (SLFN11) and retinoblastoma transcriptional corepressor 1 (RB1) was evaluated by real-time polymerase chain reaction (RT-PCR) and immunohistochemistry analyses. In addition, the combination of irinotecan and the ataxia telangiectasia and Rad3-related protein (ATR) inhibitor VE-822 was tested in SLFN11-negative PDXs, and two clinical non-camptothecin TOP1 inhibitors (LMP400 and LMP776) were tested. Thirty-eight percent of the TNBC models responded to irinotecan. BRCAness combined with high SLFN11 expression and RB1 loss identified highly sensitive tumors, consistent with the notion that deficiencies in cell cycle checkpoints and DNA repair result in high sensitivity to TOP1 inhibitors. Treatment by the ATR inhibitor VE-822 increased sensitivity to irinotecan in SLFN11-negative PDXs and abolished irinotecan-induced phosphorylation of checkpoint kinase 1 (CHK1). LMP400 (indotecan) and LMP776 (indimitecan) showed high antitumor activity in BRCA1-mutated or BRCAness-positive PDXs. Last, low SLFN11 expression was associated with poor survival in 250 patients with TNBC treated with anthracycline-based chemotherapy. In conclusion, a substantial proportion of TNBC respond to irinotecan. BRCAness, high SLFN11 expression, and RB1 loss are highly predictive of response to irinotecan and the clinical indenoisoquinoline TOP1 inhibitors.

Analysis of genomic and non-genomic signaling of estrogen receptor in PDX models of breast cancer treated with a combination of the PI3K inhibitor alpelisib (BYL719) and fulvestrant

BACKGROUND

Endocrine therapies targeting estrogen signaling have significantly improved breast cancer (BC) patient survival, although 40% of ERα-positive BCs do not respond to those therapies. Aside from genomic signaling, estrogen triggers non-genomic pathways by forming a complex containing methylERα/Src/PI3K, a hallmark of aggressiveness and resistance to tamoxifen. We aimed to confirm the prognostic value of this complex and investigated whether its targeting could improve tumor response in vivo.

METHODS

The interaction of ERα/Src and ERα/PI3K was studied by proximity ligation assay (PLA) in a cohort of 440 BC patients. We then treated patient-derived BC xenografts (PDXs) with fulvestrant or the PI3K inhibitor alpelisib (BYL719) alone or in combination. We analyzed their anti-proliferative effects on 6 ERα+ and 3 ERα- PDX models. Genomic and non-genomic estrogen signaling were assessed by measuring ERα/PI3K interaction by PLA and the expression of estrogen target genes by RT-QPCR, respectively.

RESULTS

We confirmed that ERα/Src and ERα/PI3K interactions were associated with a trend to poorer survival, the latter displaying the most significant effects. In ERα+ tumors, the combination of BYL719 and fulvestrant was more effective than fulvestrant alone in 3 models, irrespective of PI3K, PTEN status, or ERα/PI3K targeting. Remarkably, resistance to fulvestrant was associated with non-genomic ERα signaling, since genomic degradation of ERα was unaltered in these tumors, whereas the treatment did not diminish the level of ERα/PI3K interaction. Interestingly, in 2 ERα- models, fulvestrant alone impacted tumor growth, and this was associated with a decrease in ERα/PI3K interaction.

CONCLUSIONS

Our results demonstrate that ERα/PI3K may constitute a new prognostic marker, as well as a new target in BC. Indeed, resistance to fulvestrant in ERα+ tumors was associated with a lack of impairment of ERα/PI3K interaction in the cytoplasm. In addition, an efficient targeting of ERα/PI3K in ERα- tumors could constitute a promising therapeutic option.

PLK1 inhibition exhibits strong anti-tumoral activity in CCND1-driven breast cancer metastases with acquired palbociclib resistance

A significant proportion of patients with oestrogen receptor (ER) positive breast cancers (BC) develop resistance to endocrine treatments (ET) and relapse with metastatic disease. Here we perform whole exome sequencing and gene expression analysis of matched primary breast tumours and bone metastasis-derived patient-derived xenografts (PDX). Transcriptomic analyses reveal enrichment of the G2/M checkpoint and up-regulation of Polo-like kinase 1 (PLK1) in PDX. PLK1 inhibition results in tumour shrinkage in highly proliferating CCND1-driven PDX, including different RB-positive PDX with acquired palbociclib resistance. Mechanistic studies in endocrine resistant cell lines, suggest an ER-independent function of PLK1 in regulating cell proliferation. Finally, in two independent clinical cohorts of ER positive BC, we find a strong association between high expression of PLK1 and a shorter metastases-free survival and poor response to anastrozole. In conclusion, our findings support clinical development of PLK1 inhibitors in patients with advanced CCND1-driven BC, including patients progressing on palbociclib treatment.

Combination of PI3K and MEK inhibitors yields durable remission in PDX models of PIK3CA-mutated metaplastic breast cancers

Background

Metaplastic breast cancer (MBC) is a rare form of breast cancer characterized by an aggressive clinical presentation, with a poor response to standard chemotherapy. MBCs are typically triple-negative breast cancers (TNBCs), frequently with alterations to genes of the PI3K-AKT-mTOR and RTK-MAPK signaling pathways. The objective of this study was to determine the response to PI3K and MAPK pathway inhibitors in patient-derived xenografts (PDXs) of MBCs with targetable alterations.

Methods

We compared survival between triple-negative MBCs and other histological subtypes, in a clinical cohort of 323 TNBC patients. PDX models were established from primary breast tumors classified as MBC. PI3K-AKT-mTOR and RTK-MAPK pathway alterations were detected by targeted next-generation sequencing (NGS) and analyses of copy number alterations. Activation of the PI3K-AKT-mTOR and RTK-MAPK signaling pathways was analyzed with reverse-phase protein arrays (RPPA). PDXs carrying an activating mutation of PIK3CA and genomic changes to the RTK-MAPK signaling pathways were treated with a combination consisting of a PI3K inhibitor and a MEK inhibitor.

Results

In our clinical cohort, the patients with MBC had a worse prognosis than those with other histological subtypes. We established nine metaplastic TNBC PDXs. Three had a pathogenic mutation of PIK3CA and additional alterations to genes associated with RTK-MAPK signaling. The MBC PDXs expressed typical EMT and stem cell genes and were of the mesenchymal or mesenchymal stem-like TNBC subtypes. On histological analysis, MBC PDXs presented squamous or chondroid differentiation. RPPA analysis showed activation of the PI3K-AKT-mTOR and RTK-MAPK signaling pathways. In vivo, the combination of PI3K and MAPK inhibitors displayed marked antitumor activity in PDXs carrying genomic alterations of PIK3CA, AKT1, BRAF, and FGFR4.

Conclusion

The treatment of metaplastic breast cancer PDXs by activation of the PI3K-AKT-mTOR and RTK-MAPK pathways at the genomic and protein levels with a combination of PI3K and MEK inhibitors resulted in tumor regression in mutated models and may therefore be of interest for therapeutic purposes.

Response to mTOR and PI3K inhibitors in enzalutamide-resistant luminal androgen receptor triple-negative breast cancer patient-derived xenografts

Luminal androgen receptor (LAR) breast cancer accounts for 10% of all triple-negative breast cancers (TNBC). Anti-androgen therapy for this subtype is in development, but yields only partial clinical benefits. In this study, we aimed to characterize the genomic alterations of LAR TNBC, to analyze activation of the PI3K signaling pathway and to compare the response to PI3K pathway inhibitors with that to anti-androgen therapy in patient-derived xenografts (PDX) of LAR TNBC.

Methods: Four LAR PDX models were identified, on the basis of their transcriptomic profiles, in a cohort of 57 PDX models of TNBC. The expression of AR-related genes, basal and luminal cytokeratins and EMT genes was analyzed by RT-PCR and IHC. AKT1 and PIK3CA mutations were identified by targeted NGS, and activation of the PI3K pathway was analyzed with a reverse-phase protein array. Three LAR PDXs with a PIK3CA or AKT1 mutation were treated with the AR inhibitor enzalutamide, a PI3K inhibitor, a dual PI3K-mTOR inhibitor and a mTORC1-mTORC2 inhibitor. Finally, we screened a clinical cohort of 329 TNBC for PIK3CA and AKT1 hotspot mutations.

Results: LAR TNBC PDXs were significantly enriched in PIK3CA and AKT1 mutations, and had higher levels of luminal-androgen-like gene expression and a higher PI3K pathway protein activation score than other TNBC subtypes. Immunohistochemistry analysis revealed strong expression of the luminal cytokeratin CK18 and AR in three LAR PDX models. We found that mTOR and PI3K inhibitors had marked antitumor activity in vivo in PDX harboring genomic alterations of PIK3CA and AKT1 genes that did not respond to the AR antagonist enzalutamide. PIK3CA mutations were detected in more than one third of AR+ TNBC from patients (38%), and only 10% of AR-negative TNBC.

Conclusion: Our results for PDX models of LAR TNBC resistant to enzalutamide indicate that PIK3CA and AKT1 are potential therapeutic targets.

« Réa’ssure moi » Des outils pour accompagner l’enfant visiteur en réanimation

Alors que se généralise progressivement l’ouverture des services de réanimation aux visites 24 heures sur 24, la présence des enfants semble encore controversée. Les unités de réanimation chirurgicale du CHU de Caen ont décidé de mettre fin à cette politique restrictive de visites. Cependant, accompagner un enfant face à la mort ou à la maladie ne s’improvise pas. La présence de ce « petit visiteur » est particulièrement stressante pour les familles et les soignants. Elle nécessite donc un encadrement spécifique, plus complexe que celui de l’adulte. En réponse à ce besoin, les équipes de réanimation du CHU de Caen ont développé divers supports (livret et pièce d’accueil, box de réanimation miniature) pour accompagner les enfants et soutenir les équipes soignantes dans cette démarche.

Abstract 925: PDX models of ER+ endocrine-resistant metastatic breast cancer identify Polo-like kinase 1 (PLK1) as a therapeutic target

Background: Metastatic estrogen receptor positive (ER+) breast cancers (BC) are genetically heterogeneous and a significant proportion of patients display intrinsic or acquired resistance to endocrine treatments, mTOR and CDK4/6 inhibitors. The objective of this study was to identify new therapies in clinically relevant PDX models of metastatic ER+ BC progressing on endocrine treatment and/or palbociclib.

Methods: PDX models were generated by engraftment of spinal bone metastases from 120 BC patients. PDXs were molecularly characterized using SNP-arrays, targeted exome sequencing and global gene expression (GEX) analysis. The anti-tumor efficacy of the PLK1 inhibitor volasertib was evaluated in vivo compared to fulvestrant and palbociclib in two PDX models. PLK1 abundance was analyzed by immunohistochemistry in PDXs and compared with the original primary tumor and bone metastasis from each patient. PLK1 expression measured by RT-PCR was assessed in a cohort of 441 BC patients with 15-year follow-up. GEX analysis of PLK1was assessed in patients treated with neoadjuvant anastrazole. Mechanistic studies were performed in a panel of endocrine resistant BC cell lines.

Results: Ten PDX have been established, 8 were ER+ and 2 triple-negative (TN). Genomic alterations included mutations in AKT1, PI3KCA, BRCA2, GATA3, NF1, and amplifications of FGFR1, CCND1 and CCNE2. Comparative pathway analysis of bone metastases derived PDX and patients' primary tumors showed enrichment for pathways associated with mitotic nuclear division, chromatid segregation and G2/M transition. PLK1 was the top commonly up-regulated gene within these pathways. Treatment of an endocrine-resistant ER+ PDX, harboring amplification of CCND1, CCNE2, FGFR1 and high expression of CDK1, showed only partial response to palbociclib and resistance to the FGFR inhibitor, AZD4547. However, PLK1 inhibitor volasertib induced rapid tumor shrinkage and complete response within 5 weeks. Importantly, volasertib was also highly effective when tested as second line therapy in palbociclib pre-treated xenografts. In-vitro inhibition of PLK1 by siRNA or volasertib inhibited tumor proliferation without affecting the expression of ER-regulated genes, suggesting an ER-independent function of PLK1 in regulating cell proliferation. Assessment of the clinical validity of PLK1 expression, revealed a strong association with poor metastases free survival (p&lt;0.0001) in ER+ BC, but not in HER2+ or TNBC. Finally, in a cohort of patients treated with neoadjuvant anastrozole, on-treatment gene expression of PLK1 was significantly (p&lt;0.0001) associated with poor response.

Conclusion: We show that inhibition of PLK1 is a new potential treatment strategy for metastatic ER+ BC. Additional experiments are ongoing in PDX and cell lines to investigate G2/M phase dependence of ER+ BC and to identify predictive biomarkers.

Citation Format: Elodie Montaudon, Joanna Nikitorowicz-Buniak, Laura Sourd, Rania El Botty, Ahmed Dahmani, Léa Huguet, Ludivine Morriset, Pierre Painsec, Fariba Nemati, Sophie Vacher, Sophie Chateau-Joubert, Sunil Pancholi, Camilla Rega, Ricardo Ribas, André Nicolas, Didier Meseure, Anne Salomon, Zakia Tariq, Keltouma Driouch, Florence Coussy, Guillaume Dutertre, Paul Cottu, Ivan Bièche, Lesley-Ann Martin, Elisabetta Marangoni. PDX models of ER+ endocrine-resistant metastatic breast cancer identify Polo-like kinase 1 (PLK1) as a therapeutic target [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 925.

A large collection of integrated genomically characterized patient-derived xenografts highlighting the heterogeneity of triple-negative breast cancer

Triple-negative breast cancer (TNBC) represents 10% of all breast cancers and is a very heterogeneous disease. Globally, women with TNBC have a poor prognosis, and the development of effective targeted therapies remains a real challenge. Patient-derived xenografts (PDX) are clinically relevant models that have emerged as important tools for the analysis of drug activity and predictive biomarker discovery. The purpose of this work was to analyze the molecular heterogeneity of a large panel of TNBC PDX (n = 61) in order to test targeted therapies and identify biomarkers of response. At the gene expression level, TNBC PDX represent all of the various TNBC subtypes identified by the Lehmann classification except for immunomodulatory subtype, which is underrepresented in PDX. NGS and copy number data showed a similar diversity of significantly mutated gene and somatic copy number alteration in PDX and the Cancer Genome Atlas TNBC patients. The genes most commonly altered were TP53 and oncogenes and tumor suppressors of the PI3K/AKT/mTOR and MAPK pathways. PDX showed similar morphology and immunohistochemistry markers to those of the original tumors. Efficacy experiments with PI3K and MAPK inhibitor monotherapy or combination therapy showed an antitumor activity in PDX carrying genomic mutations of PIK3CA and NRAS genes. TNBC PDX reproduce the molecular heterogeneity of TNBC patients. This large collection of PDX is a clinically relevant platform for drug testing, biomarker discovery and translational research.

Abstract 2973: A comprehensive panel of patient-derived xenografts representing the molecular heterogeneity and diversity of triple-negative breast cancer

Purpose: Triple-negative breast cancer (TNBC) is a heterogeneous disease. Patients diagnosed with TNBC have a poor prognosis and identification of new biomarkers and therapeutic agents is a high priority. Patient-derived xenografts (PDX) are clinically relevant models that have emerged as important tool for the analysis of drug activity and predictive biomarker discovery. The purpose of this work was to analyze the molecular heterogeneity of a large panel of TNBC PDX with the perspective to test targeted therapy and to identify biomarkers of response.

Experimental Design: PDX of early-stage TNBC established from 2003 to 2016 (N=60) were analyzed by high-resolution array CGH and gene expression profiling (Cytoscan HD and Human Gene 1.1 ST arrays). Subtypes were identified with the tool TNBCtype (Chen et al., 2012) based on transcriptomic data. A targeted next-generation sequencing (NGS) of 100 genes (the top frequently mutated genes in breast cancer) was performed on Illumina HiSeq2500 sequencer. COSMIC, Tumorportal and cBioportal databases were used for the interpretation of genomic variants. Immunohistochemistry (IHC) and morphologic analysis of PDX were performed as compared to the corresponding patients' tumors. PDX carrying targetable genomic alterations in the PI3K/AKT/mTOR and MAPK signaling pathways were treated by specific inhibitors (selumetinib, BAY 80-6946 and PF-04691502).

Results: At the gene expression level, TNBC PDX represent all the different TNBC subtypes identified by the Lehmann classification. The frequency of the different TNBC subtypes was similar to the TGCA TNBC, except for the immunomodulatory subtype, underrepresented in PDX. Somatic pathologic mutations and copy number alterations were similar in PDX and TCGA TNBC patients. Among the top altered genes are TP53 and oncogenes and tumor suppressors of the PI3K/AKT/mTOR and MAPK pathways (including PIK3CA, AKT1, NF1 and NRAS/KRAS). At the histologic level, TNBC PDX were mainly composed of invasive ductal carcinoma of no special type, with some tumors being classified as apocrine or metaplastic carcinomas. Comparison with the original tumors show similar patterns (based on IHC analysis of CK5, CK8/18, CK14 and AR, FOXA1, EGFR and Ki67). In vivo efficacy experiments with PI3K and MAPK pathways inhibitors showed marked antitumor activity in PDX carrying genomic alterations of PIK3CA, AKT1 and NRAS, NF1 genes. Drug combination experiments are currently ongoing in PDX with simultaneous genomic alterations of PI3KCA and MAPK related genes.

Conclusions: TNBC PDX reproduce the molecular heterogeneity and diversity of TNBC patients. This large collection of PDX is a clinically relevant platform for drug testing, biomarker discovery and translational research.

Citation Format: Florence Coussy, Virginie Bernard, Marion Lavigne, Anais Boulai, Sophie Chateau-Joubert, Ahmed Dahmani, Elodie Montaudon, Cécile Reyes, Rania El Botty, Gaëlle Pieron, Cécile Laurent, Samia Melaabi, Anne Vincent Salomon, Ivan Bièche, Elisabetta Marangoni. A comprehensive panel of patient-derived xenografts representing the molecular heterogeneity and diversity of triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2973.

Abstract 1718: Tumor immune gene profile before and after various targeted therapies in NSCLC PDXs

Introduction: The blockade of immune checkpoints with antibodies directed against CTLA-4, PD-1 and PD-L1 molecules, is now entering in the current management of non-small cell lung cancer (NSCLC) patients; those tumors are heterogeneous regarding driver oncogenes, which predict the efficacy of targeted therapies (TT). In this context, our study aimed to define the relationship between conventional TT used in NSCLC and the dynamic expression of immune genes.

Experimental procedure: Eight different NSCLC Patient-Derived Xenografts (PDXs) with defined mutations, were grafted in immunodeficient mice which were then treated by various TT (Table). About 3 tumors per group were collected at the end of the in vivo experiments. The expression of human and mouse genes, using species-specific primers was determined by qPCR and normalized to the expression of the human or mouse Total Binding Protein gene. Basal gene expression, predictive markers of response and resistance to tested therapies, as well as pharmacodynamics (PD) markers were analyzed.

Results: Basal immune gene expression analysis revealed various immune profiles in this panel of NSCLC PDXs, with clustering of both models and genes. Predictive and pharmacodynamics markers underlined the impact of human HLA class I and II gene expression in the response to erlotinib and everolimus (HLA-A, HLA-DRA, and HLA-DRB); of B7-H3 (CD276), PDL1 (CD274) and Tigit (PVRIG) in the response to erlotinib; and of TNFSF7 (CD70) and TNFSF9 in the response to BKM120. PD markers showed that PDL1, B7-H3, and Tigit expression was highly impacted by everolimus, erlotinib, and BKM120 treatments, respectively. Complete gene expression results can be presented at the meeting.

Conclusions: Using NSCLC PDXs, we have identified specific tumor immune profiles and a set of genes involved in the response to TT. Moreover, PD analysis of immune markers reveals potential combinations of TT with immune checkpoints blockade that may have important translational value.

NSCLC PDXsLCF4LCF9LCF12LCF15LCF25LCF29ML1ML5HistologyAdenocarcinomaXXXXXXXLarge cellsXMUTATIONSEGFRXXKRASXXPi3KCAXXXTREATMENTS (Targets)Cetuximab (1)EGFRXXXXErlotinib (2)EGFRXXXXAfatinib (3)EGFR/HER2XXXXBKM120 (4)Pi3KXXXXXXXXEverolimus (5)mTORC1XXXXSelumetinib (6)MEK1/2XXXXXXXX1 + 2/XXXX1 + 3/XXXX1 + 4/X2 + 4/X3 + 4/X5 + 6/XXXX

Citation Format: Elodie Montaudon, Sophie Vacher, Wilfrid Richer, Ahmed Dahmani, Caroline Guibaudet, Olivier Déas, Stefano Cairo, Ludmilla De Plater, Marine Dubois, Fariba Némati, Christine Sedlik, Jean-Gabriel Judde, Nicolas Girard, Ivan Bieche, Eliane Piaggio, Didier Decaudin. Tumor immune gene profile before and after various targeted therapies in NSCLC PDXs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1718.

Fasciolosis due to Fasciola hepatica in ruminants in abattoirs and its economic impact in two regions in Algeria

and February 2009. The aim of the study was to determine the prevalence of infected livers with fascioliasis and to evaluate the economic loss due to the condemnation of livers infected with fascioliasis. A total of 3,457 cattle, 6,161 sheep and 5,764 goats were slaughtered and examined in El Tarf abattoir, north Algeria (humid climate), and 2,151 cattle, 5,724 sheep, 351 goats and 582 camels in Ouargla abattoir, south Algeria (saharan climate). In El Tarf region, the prevalence of fascioliasis infection was 26.7±2.5%, 6.5±0.4% and 2.5±0.2% in cattle, sheep and goats, respectively (P< 0.001). In Ouargla region, fascioliasis is reported for the first time in cattle (1.7±0.7%). Sheep, goats and camels were not infected. The overall economic loss due to hepatic condemnations as a result of fascioliasis was estimated at 60,000 euros in El Tarf region and 4,000 euros in Ouargla region. According to this study, it can be concluded that fascioliasis is endemic in the northern Algeria in ruminants and, the disease should be considered seriously as a great threat to ruminant health and profitability.

Capecitabine Efficacy Is Correlated with TYMP and RB1 Expression in PDX Established from Triple-Negative Breast Cancers

Purpose: Triple-negative breast cancer (TNBC) patients with residual disease after neoadjuvant chemotherapy have a poor outcome. We developed patient-derived xenografts (PDX) from residual tumors to identify efficient chemotherapies and predictive biomarkers in a context of resistance to anthracyclines- and taxanes-based treatments.Experimental Design: PDX were established from residual tumors of primary breast cancer patients treated in neoadjuvant setting. TNBC PDX were treated by anthracyclines, taxanes, platins, and capecitabine. Predictive biomarkers were identified by transcriptomic and immunohistologic analysis. Downregulation of RB1 was performed by siRNA in a cell line established from a PDX.Results: Residual TNBC PDX were characterized by a high tumor take, a short latency, and a poor prognosis of the corresponding patients. With the exception of BRCA1/2-mutated models, residual PDX were resistant to anthracyclines, taxanes, and platins. Capecitabine, the oral prodrug of 5-FU, was highly efficient in 60% of PDX, with two models showing complete responses. Prior treatment of a responder PDX with 5-FU increased expression of thymidylate synthase and decreased efficacy of capecitabine. Transcriptomic and IHC analyses of 32 TNBC PDX, including both residual tumors and treatment-naïve derived tumors, identified RB1 and TYMP proteins as predictive biomarkers for capecitabine response. Finally, RB1 knockdown in a cell line established from a capecitabine-responder PDX decreased sensitivity to 5-FU treatment.Conclusions: We identified capecitabine as efficient chemotherapy in TNBC PDX models established from residual disease and resistant to anthracyclines, taxanes, and platins. RB1 positivity and high expression of TYMP were significantly associated with capecitabine response. Clin Cancer Res; 24(11); 2605-15. ©2018 AACR.

Dual inhibition of protein kinase C and p53-MDM2 or PKC and mTORC1 are novel efficient therapeutic approaches for uveal melanoma

Uveal melanoma (UM) is the most common cancer of the eye in adults. Many UM patients develop metastases for which no curative treatment has been identified. Novel therapeutic approaches are therefore urgently needed. UM is characterized by mutations in the genes GNAQ and GNA11 which activate the PKC pathway, leading to the use of PKC inhibitors as a rational strategy to treat UM tumors. Encouraging clinical activity has been noted in UM patients treated with PKC inhibitors. However, it is likely that curative treatment regimens will require a combination of targeted therapeutic agents. Employing a large panel of UM patient-derived xenograft models (PDXs), several PKC inhibitor-based combinations were tested in vivo using the PKC inhibitor AEB071. The most promising approaches were further investigated in vitro using our unique panel of UM cell lines. When combined with AEB071, the two agents CGM097 (p53-MDM2 inhibitor) and RAD001 (mTORC1 inhibitor) demonstrated greater activity than single agents, with tumor regression observed in several UM PDXs. Follow-up studies in UM cell lines on these two drug associations confirmed their combination activity and ability to induce cell death. While no effective treatment currently exists for metastatic uveal melanoma, we have discovered using our unique panel of preclinical models that combinations between PKC/mTOR inhibitors and PKC/p53-MDM2 inhibitors are two novel and very effective therapeutic approaches for this disease. Together, our study reveals that combining PKC and p53-MDM2 or mTORC1 inhibitors may provide significant clinical benefit for UM patients.

Abstract 1853: Inhibition of mTOR downregulates expression of DNA repair proteins and is highly efficient against BRCA2-mutated breast cancer when combined to PARP inhibition

Purpose: DNA repair deficiencies and activation of PI3K/AKT/mTOR pathway are common events in breast cancer. BRCA1/2 mutations have been associated with sensitivity to PARP1 inhibitors (synthetic lethality), while alterations in component of the PI3K/AKT/mTOR pathway might confer sensitivity to PI3KCA and mTOR inhibitors. Here we explored the therapeutic benefit of combining a mTOR and a PARP inhibitor in BRCA2-mutated patient-derived xenografts (PDX) with alterations in the PI3K/AKT/mTOR pathway.

Experimental design: the combination of the mTOR inhibitor everolimus and the PARP inhibitor olaparib was tested in two BRCA2-mutated PDX established from a luminal B tamoxifen-resistant and a basal-like breast cancers. Both carried alterations in the PI3K/AKT/mTOR pathway: PIK3R1 mutation and PTEN loss for the luminal B PDX and PTEN loss for the basal-like PDX. To identify putative crosstalk events between mTOR and DNA repair, a Reverse Phase Protein Array (RPPA) analysis of multiple signaling pathways and DNA repair processes was performed on untreated and treated xenografts. Gene and protein expression changes were confirmed by RT-PCR and Western Blot analyses. The capacity to repair DNA damage was measured by P-H2AX immunostaining.

Results: in both PDX, everolimus and olaparib showed marked anti-tumor activity with a growth inhibition comprised between 78% and 86% in the monotherapy setting and 96% in the combination arm, where 100% of mice showed tumor regressions. In the luminal B tumor this combination was more efficient than the combination of everolimus and endocrine therapies (fulvestrant or tamoxifen). In both PDX, the fraction of P-H2AX (marker of unrepaired DNA double-strand breaks) positive cells was increased after everolimus treatment, suggesting a link between mTOR and DNA damage, and strongly increased in the combination setting. RPPA analysis of tumors treated by everolimus alone revealed a marked downregulation of different proteins involved in DNA repair, including FANCD2, RAD50 and SUV39H1, a chromatin compactor factor essential in homologous recombination. In the combination setting, expression of these proteins was almost completely abolished, suggesting convergence of PARP and mTOR in downregulation of DNA repair components.

Conclusions: our results suggest that combining mTOR and DNA repair inhibitors could be a successful strategy to treat a subset of breast cancer with BRCA2 mutation and alterations in the PI3K/AKT/mTOR pathway. Further experiments with mTOR and PARP inhibitors combinations are ongoing in sporadic breast cancer PDX showing a BRCAness phenotype.

Citation Format: Florence Coussy, Rania El Botty, Rana Hatem, Franck Assayag, Ahmed Dahmani, Marine Huppé, Sophie Chateau Joubert, Jean -Luc Servely, Virginie Bernard, Sophie Vacher, Berangere Ouine, Aurelie Cartier, Leanne De Koning, Paul Cottu, Ivan Bieche, Elisabetta Marangoni. Inhibition of mTOR downregulates expression of DNA repair proteins and is highly efficient against BRCA2-mutated breast cancer when combined to PARP inhibition [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 1853. doi:10.1158/1538-7445.AM2017-1853

Abstract 3027: Dual inhibition of PKC and p53-MDM2 or PKC and mTORC1 are novel efficient therapeutic approaches for uveal melanoma

Uveal melanoma (UM), although rare in incidence, is the most common cancer of the eye in adults. Many UM patients develop metastases for which no curative treatment has been identified and therefore novel therapeutic approaches are urgently needed. UM is characterized by mutations in the genes GNAQ and GNA11 which activate the PKC pathway. This has led to the use of PKC inhibitors as a rational targeting strategy to treat UM tumors. Encouraging clinical activity has been noted in UM patients treated with PKC inhibitors. However, it is likely that curative treatment regimens will require a combination of targeted therapeutic agents. Employing a large panel of UM patient-derived xenograft models, several PKC inhibitor-based combination studies were performed using the PKC inhibitor AEB071 (Sotrastaurin). When combined with AEB071, the targeted agents CGM097 (p53-MDM2 inhibitor), RAD001 (Everolimus, mTORC1 inhibitor) and MEK162 (Binimetinib, a MEK inhibitor) demonstrated greater activity in the UM patient-derived xenograft models than their activity as single agents. Importantly, tumor regressions were observed in several UM models with AEB071 + RAD001 and AEB071 + CGM097 co-treatments. Follow-up in vitro studies in UM cell lines using AEB071 combined with either CGM097 or RAD001 provided a more detailed mechanistic understanding of their combination activity and confirmed their ability to induce cell death. Together, these preclinical studies reveal that combining PKC and p53-MDM2 inhibitors or PKC and mTORC1 inhibitors may provide significant clinical benefit for patients with UM.

Citation Format: Guillaume Carita, Estelle Frisch Dit Leitz, Ahmed Dahmani, Chloe Raymondie, Nathalie Cassoux, Sophie Piperno-Neumann, Fariba Némati, Ensar Halilovic, Sebastien Jeay, Andrew Wylie, Caroline Emery, Sergio Roman-Roman, Marie Schoumacher, Didier Decaudin. Dual inhibition of PKC and p53-MDM2 or PKC and mTORC1 are novel efficient therapeutic approaches for uveal melanoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3027.

Vasculature analysis of patient derived tumor xenografts using species-specific PCR assays: evidence of tumor endothelial cells and atypical VEGFA-VEGFR1/2 signalings

BACKGROUND

Tumor endothelial transdifferentiation and VEGFR1/2 expression by cancer cells have been reported in glioblastoma but remain poorly documented for many other cancer types.

METHODS

To characterize vasculature of patient-derived tumor xenografts (PDXs), largely used in preclinical anti-angiogenic assays, we designed here species-specific real-time quantitative RT-PCR assays. Human and mouse PECAM1/CD31, ENG/CD105, FLT1/VEGFR1, KDR/VEGFR2 and VEGFA transcripts were analyzed in a large series of 150 PDXs established from 8 different tumor types (53 colorectal, 14 ovarian, 39 breast and 15 renal cell cancers, 6 small cell and 5 non small cell lung carcinomas, 13 cutaneous melanomas and 5 glioblastomas) and in two bevacizumab-treated non small cell lung carcinomas xenografts.

RESULTS

As expected, mouse cell proportion in PDXs -evaluated by quantifying expression of the housekeeping gene TBP- correlated with all mouse endothelial markers and human VEGFA RNA levels. More interestingly, we observed human PECAM1/CD31 and ENG/CD105 expression in all tumor types, with higher rate in glioblastoma and renal cancer xenografts. Human VEGFR expression profile varied widely depending on tumor types with particularly high levels of human FLT1/VEGFR1 transcripts in colon cancers and non small cell lung carcinomas, and upper levels of human KDR/VEGFR2 transcripts in non small cell lung carcinomas. Bevacizumab treatment induced significant low expression of mouse Pecam1/Cd31, Eng/Cd105, Flt1/Vegfr1 and Kdr/Vefr2 while the human PECAM1/CD31 and VEGFA were upregulated.

CONCLUSIONS

Taken together, our results strongly suggest existence of human tumor endothelial cells in all tumor types tested and of both stromal and tumoral autocrine VEGFA-VEGFR1/2 signalings. These findings should be considered when evaluating molecular mechanisms of preclinical response and resistance to tumor anti-angiogenic strategies.

Abstract A15: Establishment and characterization of a new patient-derived non-small cell lung cancer xenograft panel for pharmacological assessment

Background: Development of targeted therapies in non-small cell lung carcinoma (NSCLC) is rapidly growing and offers promising treatment perspectives for cancer patients. However, the assessment of new therapeutic compounds requires preclinical models defined by precise tumor molecular features that could impact their antitumor efficacy. The aim of this study was then to develop and characterize a new reliable panel of human NSCLC xenografts.

Material and methods: From 28 samples of NSCLC specimens obtained from patient's surgery and grafted into Swiss nude mice, 18 transplantable xenografts were established (64%). Molecular characterization included histological features, gene mutation status (EGFR, KRAS, and BRAF), and research of ALK translocation in both xenografts and their corresponding patient's tumors. For determination of the predictive value of the models, a standard pharmacological assessment was then performed in 6 adenocarcinoma (ADK) models using the EGFR inhibitor erlotinib (50 mg/kg/day, 5 days/week, 4 weeks, orally). Tumor Growth Inhibition (TGI) was calculated to measure the efficiency of erlotinib. Finally, to evaluate responses to erlotinib according to individual mouse variability, we decided to consider each mouse as one tumor-bearing entity. In all in vivo experiments, a relative tumor volume variation (RTVV) of each erlotinib-treated mouse was calculated from the following formula: Vt/Vc, where Vt is the volume of the treated mouse and Vc the median volume of the corresponding control group at a time corresponding to the end of treatment. An overall response rate (ORR) was then calculated for both EGFR-mutated and -non mutated tumors.

Results: Among the 18 established models, we have diagnosed 9 ADK, 6 epidermoid carcinomas, and 3 undifferientiated large cell cancers, with a high degree of similarity with the originated patient's tumors in regard to histological characteristics (Morphology and IHC), and a complete concordance for gene mutation status. Among the 18 NSCLC xenografts, 3 were EGFR mutated (exon 18 G719A, exon 19 del18b, and exon 21 L858R) and 3 others were KRAS mutated (G12C). No BRAF mutation nor ALK translocation were found. Erlotinib induced a TGI of 30%, 62%, and 93% for the 3 EGFR-mutated xenografts, and 0% (preliminary result), 37%, and 52% (KRAS-mutated model) for the 3 wild type EGFR tumors. Moreover, the individual mouse ORR ORR ≥ 90% was 26% in the first group and 4% in the second one, respectively (p &lt; 0,05).

Conclusions: We have developed and characterized a new panel of primary human NSCLC xenografts that is highly representative of the heterogeneity of the disease and responses to the anti-EGFR targeted therapy, and provides precious tools to assess innovative therapeutic approaches.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A15.

Abstract B217: Antitumor activity of the new Bcl-2/Bcl-xl inhibitor S44563 in primary human uveal melanoma xenografts

Background: Uveal melanoma (UM) is the most common primary malignancy of the eye in adults. Although over 95% of patients have disease limited to the eye at diagnosis, 50% will develop liver metastases and ultimately die of their disease. Because of the limited efficacy of current treatments, new therapeutic strategies need therefore to be developed. Reduced capacity for apoptosis induction is one potential obstacle to therapy but, consequently, regulators of apoptosis may constitute an attractive approach to anticancer therapeutics, such as the Bcl-2 family proteins. Human uveal melanomas are characterized by a high amount of Bcl-2 expression, ranging between 50% and 100% of studied cases. Such an observation has been confirmed in our panel of 16 primary human uveal melanoma xenografts obtained from patient's tumors (Némati et al, CCR 2010). We have therefore investigated the efficacy of the new Bcl-2/Bcl-XL inhibitor S44563 on 4 primary human UM xenografts.

Materials and methods: Four well characterized models of primary human UM, obtained from patients after enucleation (MP41 and MP77) or liver metastasis surgery (MM26 and MM66) (Némati et al, CCR 2010), were used for the in vivo experiments. S44563 (50 or 100 mg/kg/day, days 1–5/8–12/22–26/29–33) was administered IP alone or combined with fotemustine, either concomitant (15 or 30 mg/kg days 1 and 22), or after chemotherapy (100 mg/kg) at days 43–47/50–54/64–68/71–75. Tumor Growth Inhibition (TGI) was calculated to measure the efficiency of various tested compounds. Bcl-2, Bcl-XL, and Mcl-1 expressions after S44563 administration were determined by immunohistochemistry (IHC).

Results: The expression of Bcl-2, defined by IHC, was highly positive for the 4 models used (75% to 100% of tumor cells). S44563 administered alone at 50 and 100 mg/kg induced a moderate TGI of about 50% in 1 model (MP41) among all without dose effect. When S44563 was combined to fotemustine, we observed a synergistic activity in 2 models (MP77 and MM66) among the 4 tested, without impact on the proportion of complete remission. Finally, when S44563 was concomitantly and/or administered after fotemustine, we found a delay of tumor growth in 2 among the 3 tested xenografts (MP77, and MM26). IHC analyses showed that Bcl-2, Bcl-XL, and Mcl-1 expressions were not modified after S44563 administration.

Conclusion: We have shown that S44563, despite a relative low efficacy when administered alone, increased the efficacy of chemotherapy in concomitant combination or after fotemustine. Such preliminary results therefore underline the therapeutic potential of this new Bcl-2/Bcl-xl inhibitor in human uveal melanoma. Némati et al. Clin Cancer Res 2010;16:2352–2362.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B217.

Abstract 1772: PDL192, a humanized anti-Tweak receptor monoclonal antibody, mediates antitumor effects in primary human breast carcinoma xenografts

Background: PDL192 is a humanized IgG1 monoclonal antibody that binds the human TWEAK receptor (TweakR). TweakR, a member of the TNFR (Tumor Necrosis Factor Receptor) superfamily, is overexpressed in several human cancers including breast cancer (BC). In BC, it may also play a role in the invasive and metastatic potential of the disease (Willis et al, Mol Cancer Res 2008). In TweakR-expressing cancer cell lines or mouse xenograft models, PDL192 has a potent antitumor effect (Culp et al., CCR 2010). All these data therefore suggest that anti-TweakR targeting could be a promising new therapeutic approach for human BC patients.

Material and methods: TweakR expression was assessed by IHC (immunohistochemistry) on 3 Tissue-Micro-Array (TMA) banks of BC samples (basal-like, ERBB2, and luminal A/B), and 25 primary human BC xenografts (HBCx). The cut-off of positivity was defined as at least 25% cells with membraneous or cytoplasmic staining or by a combined score of percentage of positive staining cells x intensity &gt; 50. The in vivo antitumor effect of PDL192 was then assessed on 7 TweakR-positive models (10 mg/kg thrice a week for 3 weeks by intraperitoneal route) in which one in combination with chemotherapy as maintenance therapy, as previsouly reported (Marangoni et al., BJC 2009).

Results: TMA analyses showed that TweakR was expressed in 16/37 basal like BC (43%), 23/37 ERBB2-positive BC (62%), and 38/71 luminal BC (54%). A high TweakR expression was correlated with double estrogen receptor- and Her2-positive tumors. Moreover, 13/25 xenografts have been found to be TweakR-positive (52%). Nine human BC models have been treated with PDL192, with 4 models (44%) showing a tumor growth inhibition (TGI) ranging between 59% and 91%. No correlation has been observed between TweakR expression and in vivo TGI. Moreover, when PDL192 was administered in complete remission after chemotherapy (doxorubicin + cyclophosphamide), we observed a highly significant delay of relapse greater than 2 months.

Conclusions: TweakR is expressed in 77/145 human BC samples (53%). In in vivo experiments, PDL192 showed potent TGI in 4/9 models, and significantly delayed tumor relapses after chemotherapy-induced complete remission. All these data therefore support the use of anti-TWEAK receptor monoclonal antibodies in the treatment of TweakR-positive BC patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1772. doi:10.1158/1538-7445.AM2011-1772

Establishment and characterization of a panel of human uveal melanoma xenografts derived from primary and/or metastatic tumors

PURPOSE

Uveal melanoma is the most common primary intraocular malignant tumor in adults and is defined by a poor natural outcome, as 50% of patients die from metastases. The aim of this study was to develop and characterize a panel of human uveal melanoma xenografts transplanted into immunodeficient mice.

EXPERIMENTAL DESIGN

Ninety tumor specimens were grafted into severe combined immunodeficient mice, and 25 transplantable xenografts were then established (28%). Relationship between tumor graft and clinical, biological, and therapeutic features of the patients included were investigated. Characterization of 16 xenografts included histology, molecular analyses by immunohistochemistry, genetic alteration analysis (single-nucleotide polymorphism), and specific tumor antigen expression by quantitative reverse transcription-PCR. Pharmacologic characterization (chemosensitivity) was also done in four models using two drugs, temozolomide and fotemustine, currently used in the clinical management of uveal melanoma.

RESULTS

Take rate of human uveal melanoma was 28% (25 of 90). Tumor take was independent of size, histologic parameters, or chromosome 3 monosomy but was significantly higher in metastatic tumors. Interestingly, in vivo tumor growth was prognostic for a lower metastasis-free survival in patients with primary tumors. A high concordance between the patients' tumors and their corresponding xenografts was found for all parameters tested (histology, genetic profile, and tumor antigen expression). Finally, the four xenografts studied displayed different response profiles to chemotherapeutic agents.

CONCLUSIONS

Based on these results, this panel of 16 uveal melanoma xenografts represents a useful preclinical tool for both pharmacologic and biological assessments.

Abstract A27: Efficacy of estramustine + docetaxel in docetaxel-resistant human prostate cancer xenograft: a preclinical model of docetaxel resistance reversion

Introduction: Androgen-dependent prostate cancers (PC) are usually sensitive to docetaxel chemotherapy. Nevertheless, docetaxel-resistance frequently appears after several cycles of treatment, raising the treatment rescue of docetaxel-resistant PC patients. If the combination of estramustine to docetaxel prolongs the metastatic-free and overall survivals of patients with androgen-dependent PC, its use remains limited in patients because of unacceptable toxicity including venous thromboses. The aims of this study were (1) to evaluate the in vivo efficacy of estramustine combined to docetaxel since initial tumor growth and since appearance of docetaxel resistance in one androgen-dependent human PC xenograft, and (2) to evaluate the efficacy of estramustine in six human androgen-independent human PC variants.

Experimental procedures: The preclinical models included the androgen-dependent PAC120 tumor obtained from a Gleason-9 primary PC of a 51-years old patient (De Pinieux et al, Am J Pathol, 2001), and six hormone-independent variants derived from PAC120. Docetaxel was administrated at a dosage of 20 mg/kg every three weeks by intraperitoneal injection for at most six cycles, and estramustine was given intraperitoneally at a dosage of 12 mg/kg days 1 to 5 every 3 weeks until mice sacrifice. Tumor volume was measured twice a week and Relative Tumor Volume (RTV) from start of treatment were then calculated. In the PAC120 model, escape to docetaxel was defined at the beginning of each next cycle (n + 1) as a ratio of RTVn+1/RTVn ≥ 2. Resistant mice were then randomized into two groups, one receiving estramustine alone, and the other treated by a combination of docetaxel + estramustine, with an evaluation of the tumor growth delay for a 2-fold tumor size increase from randomisation (TGD2). In the 6 androgen-independent PC xenografts (HID), estramustine administered alone was compared to a control group.

Results: Estramustine alone did not induce significant tumor growth inhibition in both PAC120 and HID xenografts. In PAC120 model, tumor growth inhibition (TGI) after docetaxel alone and docetaxel + estramustine was 81% and 95%, with a mean response duration of 29 days [21–63] and 68 days [64–74], respectively (p &lt; 0.05). In docetaxel-resistant tumor bearing mice, estramustine alone induced a TGD2 of 18 days, whereas estramustine + docetaxel induced a TGD2 of 49 days (p &lt; 0.05). Metastatic lesions and venous thromboses into lung of tumor-bearing mice have also been evaluated by histopathological analyses and may be presented during the meeting.

Conclusions: Estramustine alone was not efficient in both human androgen-dependent and -independent PC xenografts. Inversely, the combination of estramustine + docetaxel in first treatment line and estramustine added to docetaxel in docetaxel-resistant xenografts was highly effective. These data therefore suggest that estramustine should be combined to docetaxel in PC patients, but its use could be delayed, particularly in elderly patients, to docetaxel refractory cases.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A27.

Beta1 integrins are required for the invasion of the caecum and proximal hindgut by enteric neural crest cells

Integrins are the major adhesive receptors for extracellular matrix and have various roles in development. To determine their role in cell migration, the gene encoding the beta1 integrin subunit (Itgb1) was conditionally deleted in mouse neural crest cells just after their emigration from the neural tube. We previously identified a major defect in gut colonisation by conditional Itgb1-null enteric neural crest cells (ENCCs) resulting from their impaired migratory abilities and enhanced aggregation properties. Here, we show that the migration defect occurs primarily during the invasion of the caecum, when Itgb1-null ENCCs stop their normal progression before invading the caecum and proximal hindgut by becoming abnormally aggregated. We found that the caecum and proximal hindgut express high levels of fibronectin and tenascin-C, two well-known ligands of integrins. In vitro, tenascin-C and fibronectin have opposite effects on ENCCs, with tenascin-C decreasing migration and adhesion and fibronectin strongly promoting them. Itgb1-null ENCCs exhibited an enhanced response to the inhibitory effect of tenascin-C, whereas they were insensitive to the stimulatory effect of fibronectin. These findings suggest that beta1 integrins are required to overcome the tenascin-C-mediated inhibition of migration within the caecum and proximal hindgut and to enhance fibronectin-dependent migration in these regions.

Sarcoidosis-related hypercalcemia in 3 chronic hemodialysis patients

Hypercalcemia is a frequent complication in chronic hemodialysis (CHD) patients. A rare cause of this condition is sarcoidosis, and has only been reported 6 times in CHD. Herein, we report on 3 cases of sarcoidosis-related hypercalcemia in CHD patients: an overt case, a probable case, and a recurrence of pre-dialysis sarcoidosis. Hypercalcemia is a frequent complication in chronic hemodialysis patients: it is often related to uncontrollable secondary hyperparathyroidism or to the inappropriate use of calcium phosphate binders, 1alpha-hydroxylated vitamin D metabolites, high dialysate calcium concentrations, or to aluminium-related bone disease [Uach and Bover 1996]. However, other rare causes should also be considered, such as multiple myeloma, non-Hodgkin lymphoma [Uach and Bover 1996], vitamin A intoxication [Fishbane et al. 1995], or granulomatous diseases such as sarcoidosis. The latter has only been described in a total of 6 hemodialysis patient reports [Barbour et al. 1981, Barnard et al. 2002, Herrero et al. 1998, Kalantar-Zadeh et al. 1994, Kuwae et al. 2003, Naito et al. 1999]. In the present paper, we report on 3 cases of sarcoidosis-related hypercalcemia in chronic hemodialysis patients with 3 different patterns, i.e. overt sarcoidosis, probable sarcoidosis, and recurrence of pre-dialysis sarcoidosis.