Molecular correlates of platinum response in human high-grade serous ovarian cancer patient-derived xenografts

The PI3K/mTOR dual inhibitor GSK458 potently impedes ovarian cancer tumorigenesis and metastasis

PURPOSE

The PI3K/AKT/mTOR pathway is one of the most highly activated cellular signaling pathways in advanced ovarian cancer. Although several PI3K/AKT/mTOR inhibitors have been developed to treat various types of cancer, the antitumor efficacy of many of these compounds against ovarian cancer has remained unclear.

METHODS

Here, we tested and compared a panel of 16 PI3K/AKT/mTOR inhibitors (XL765, Miltefosine, Rapamycin, CCI-779, RAD001, FK506, XL147, GSK2110183, IPI-145, GSK2141795, BYL719, GSK458, CAL-101, XL765 analogue SAR245409, Triciribine, and GDC0941) that have entered clinical trials for antitumor activity against ovarian cancer, as well as the front line drug, paclitaxel. Antitumor efficacy was measured in both ovarian cancer cell lines and patient-derived ovarian primary tumor cell lines in vitro and in vivo.

RESULTS

We identified the PI3K/mTOR dual inhibitor GSK458 as a potent inhibitor of proliferation in all cell lines tested at half maximal inhibitory concentrations (IC₅₀) of approximately 0.01-1 µM, a range tens to hundreds fold lower than that of the other PI3K/AKT/mTOR inhibitors tested. Additionally, GSK458 showed the highest inhibitory efficacy against ovarian cancer cell migration. GSK458 also inhibited tumor growth and metastasis in nude mice intraperitoneally engrafted with SKOV3 cells or a patient-derived tumor cell xenograft (PDCX). Importantly, the inhibitory efficiency of GSK458 on cell proliferation and migration both in vitro and in vivo was comparable to that of paclitaxel. Mechanistically, the anti-tumor activity of GSK458 was found to be associated with inactivation of AKT and mTOR, and induction of cell cycle arrest at the G0/G1 phase.

CONCLUSIONS

Based on our results, we conclude that GSK458 may serve as an attractive candidate to treat ovarian cancer.

PIK3R1W624R Is an Actionable Mutation in High Grade Serous Ovarian Carcinoma

Identifying cancer drivers and actionable mutations is critical for precision oncology. In epithelial ovarian cancer (EOC) the majority of mutations lack biological or clinical validation. We fully characterized 43 lines of Patient-Derived Xenografts (PDXs) and performed copy number analysis and whole exome sequencing of 12 lines derived from naïve, high grade EOCs. Pyrosequencing allowed quantifying mutations in the source tumours. Drug response was assayed on PDX Derived Tumour Cells (PDTCs) and in vivo on PDXs. We identified a PIK3R1W624R variant in PDXs from a high grade serous EOC. Allele frequencies of PIK3R1W624R in all the passaged PDXs and in samples of the source tumour suggested that it was truncal and thus possibly a driver mutation. After inconclusive results in silico analyses, PDTCs and PDXs allowed the showing actionability of PIK3R1W624R and addiction of PIK3R1W624R carrying cells to inhibitors of the PI3K/AKT/mTOR pathway. It is noteworthy that PIK3R1 encodes the p85α regulatory subunit of PI3K, that is very rarely mutated in EOC. The PIK3R1W624R mutation is located in the cSH2 domain of the p85α that has never been involved in oncogenesis. These data show that patient-derived models are irreplaceable in their role of unveiling unpredicted driver and actionable variants in advanced ovarian cancer.

CCNE1 and BRD4 co-amplification in high-grade serous ovarian cancer is associated with poor clinical outcomes

Objective.

High-grade serous ovarian cancer (HGSOC) is the most common and lethal histological subtype of epithelial ovarian cancer. HGSOC with cyclin E1 gene (CCNE1) amplification and bromodomain and extraterminal 4 (BRD4) amplification have been associated with poor outcomes. Our objective was to evaluate clinical outcomes of HGSOC with co-amplification of CCNE1 and BRD4 and high protein expression of cyclin E and BRD4.

Methods.

Copy number amplification data were extracted from The Cancer Genome Atlas (TCGA) for 579 HGSOC. Reverse phase protein array (RPPA) TCGA data were used to determine cyclin E and BRD4 protein expression in 482 HGSOC. Cyclin E and BRD4 protein expression by immunohistochemistry (IHC) was evaluated in a tissue microarray (TMA) of 110 HGSOC. Measured clinical outcomes were survival and platinum sensitivity.

Results.

Of 30% of HGSOC with amplifications in CCNE1 or BRD4, 8% have both CCNE1 and BRD4 amplification. Protein expression of cyclin E and BRD4 are positively correlated, both by RPPA (r = 0.23; p < 0.001) and by IHC (r = 0.21; p = 0.025). Patients with CCNE1 and BRD4 co-amplified HGSOC have worse overall survival than patients without amplifications, 39.94 vs 48.06 months (p = 0.029). High protein expression of cyclin E, but not BRD4, was associated with poor overall survival (HR 1.62, 1.04–2.53, p = 0.033) and platinum resistance (p = 0.016).

Conclusion.

HGSOC with CCNE1 and BRD4 co-amplification are associated with poor overall survival. Further studies are warranted to determine the use of protein expression by IHC as a surrogate marker for CCNE1 and BRD4 co-amplified HGSOC.

Applications of patient-derived tumor xenograft models and tumor organoids

Patient-derived tumor xenografts (PDXs), in which tumor fragments surgically dissected from cancer patients are directly transplanted into immunodeficient mice, have emerged as a useful model for translational research aimed at facilitating precision medicine. PDX susceptibility to anti-cancer drugs is closely correlated with clinical data in patients, from whom PDX models have been derived. Accumulating evidence suggests that PDX models are highly effective in predicting the efficacy of both conventional and novel anti-cancer therapeutics. This also allows “co-clinical trials,” in which pre-clinical investigations in vivo and clinical trials could be performed in parallel or sequentially to assess drug efficacy in patients and PDXs. However, tumor heterogeneity present in PDX models and in the original tumor samples constitutes an obstacle for application of PDX models. Moreover, human stromal cells originally present in tumors dissected from patients are gradually replaced by host stromal cells as the xenograft grows. This replacement by murine stroma could preclude analysis of human tumor-stroma interactions, as some mouse stromal cytokines might not affect human carcinoma cells in PDX models. The present review highlights the biological and clinical significance of PDX models and three-dimensional patient-derived tumor organoid cultures of several kinds of solid tumors, such as those of the colon, pancreas, brain, breast, lung, skin, and ovary.

Recent Advancements and Applications of Human Immune System Mice in Preclinical Immuno-Oncology

Significant advances in immunotherapies have resulted in the increasing need of predictive preclinical models to improve immunotherapeutic drug development, treatment combination, and to prevent or minimize toxicity in clinical trials. Immunodeficient mice reconstituted with human immune system (HIS), termed humanized mice or HIS mice, permit detailed analysis of human immune biology, development, and function. Although this model constitutes a great translational model, some aspects need to be improved as the incomplete engraftment of immune cells, graft versus host disease and the lack of human cytokines and growth factors. In this review, we discuss current HIS platforms, their pathology, and recent advances in their development to improve the quality of human immune cell reconstitution. We also highlight new technologies that can be used to better understand these models and how improved characterization is needed for their application in immuno-oncology safety, efficacy, and new modalities therapy development.

Bone sarcoma patient-derived xenografts are faithful and stable preclinical models for molecular and therapeutic investigations

Standard therapy of osteosarcoma (OS) and Ewing sarcoma (EW) rests on cytotoxic regimes, which are largely unsuccessful in advanced patients. Preclinical models are needed to break this impasse. A panel of patient-derived xenografts (PDX) was established by implantation of fresh, surgically resected osteosarcoma (OS) and Ewing sarcoma (EW) in NSG mice. Engraftment was obtained in 22 of 61 OS (36%) and 7 of 29 EW (24%). The success rate in establishing primary cell cultures from OS was lower than the percentage of PDX engraftment in mice, whereas the reverse was observed for EW; the implementation of both in vivo and in vitro seeding increased the proportion of patients yielding at least one workable model. The establishment of in vitro cultures from PDX was highly efficient in both tumor types, reaching 100% for EW. Morphological and immunohistochemical (SATB2, P-glycoprotein 1, CD99, caveolin 1) studies and gene expression profiling showed a remarkable similarity between patient’s tumor and PDX, which was maintained over several passages in mice, whereas cell cultures displayed a lower correlation with human samples. Genes differentially expressed between OS original tumor and PDX mostly belonged to leuykocyte-specific pathways, as human infiltrate is gradually replaced by murine leukocytes during growth in mice. In EW, which contained scant infiltrates, no gene was differentially expressed between the original tumor and the PDX. A novel therapeutic combination of anti-CD99 diabody C7 and irinotecan was tested against two EW PDX; both drugs inhibited PDX growth, the addition of anti-CD99 was beneficial when chemotherapy alone was less effective. The panel of OS and EW PDX faithfully mirrored morphologic and genetic features of bone sarcomas, representing reliable models to test therapeutic approaches.

Application of Highly Immunocompromised Mice for the Establishment of Patient-Derived Xenograft (PDX) Models

Patient-derived xenograft (PDX) models are created by engraftment of patient tumor tissues into immunocompetent mice. Since a PDX model retains the characteristics of the primary patient tumor including gene expression profiles and drug responses, it has become the most reliable in vivo human cancer model. The engraftment rate increases with the introduction of Non-obese diabetic Severe combined immunodeficiency (NOD/SCID)-based immunocompromised mice, especially the NK-deficient NOD strains NOD/SCID/interleukin-2 receptor gamma chain(IL2Rγ)null (NOG/NSG) and NOD/SCID/Jak3(Janus kinase 3)null (NOJ). Success rates differ with tumor origin: gastrointestinal tumors acquire a higher engraftment rate, while the rate is lower for breast cancers. Subcutaneous transplantation is the most popular method to establish PDX, but some tumors require specific environments, e.g., orthotropic or renal capsule transplantation. Human hormone treatment is necessary to establish hormone-dependent cancers such as prostate and breast cancers. PDX mice with human hematopoietic and immune systems (humanized PDX) are powerful tools for the analysis of tumor-immune system interaction and evaluation of immunotherapy response. A PDX biobank equipped with patients' clinical data, gene-expression patterns, mutational statuses, tumor tissue architects, and drug responsiveness will be an authoritative resource for developing specific tumor biomarkers for chemotherapeutic predictions, creating individualized therapy, and establishing precise cancer medicine.

Establishment of patient-derived xenograft model in ovarian cancer and its influence factors analysis

AIM

Patient-derived xenograft (PDX) model has been applied to the study of breast cancer, lung cancer, colon cancer and other cancers. However, its feasibility in ovarian cancer has not been understood. This study aimed to establish ovarian cancer PDX model and reveal its influence factors.

METHODS

In this study, 27 patients in Obstetrics and Gynecology Hospital affiliated to Fudan University from May 2015 to May 2016 were employed to explore the method of PDX model in ovarian cancer and verify its feasibility.

RESULTS

Finally, five cases of PDX models were successfully established, and the tumor formation rate (TFR) was 18.52%. In addition, immunohistochemistry and transcriptome sequencing analysis showed that tumor of PDX model have similar gene expression, gene splicing, gene fusion and single nucleotide polymorphisms with primary tumor (R² = 0.741). Furthermore, it was revealed that compared to epithelial ovarian cancer, the TFR of PDX models with nonepithelial ovarian cancer was higher, while other factors such as the initiation site of tumor, the degree of tumor malignancy, the stage of tumor, the type of tumor and the species of experimental animals were not associated with the TFR.

CONCLUSION

Ovarian cancer PDX model, as a new scientific research model, can better keep the biological characteristics of primary tumor, which has great research value in ovarian cancer.

Cellular demolition: Proteins as molecular players of programmed cell death

Apoptosis, a well-characterized and regulated cell death programme in eukaryotes plays a fundamental role in developing or later-life periods to dispose of unwanted cells to maintain typical tissue architecture, homeostasis in a spatiotemporal manner. This silent cellular death occurs without affecting any neighboring cells/tissue and avoids triggering of immunological response. Furthermore, diminished forms of apoptosis result in cancer and autoimmune diseases, whereas unregulated apoptosis may also lead to the development of a myriad of neurodegenerative diseases. Unraveling the mechanistic events in depth will provide new insights into understanding physiological control of apoptosis, pathological consequences of abnormal apoptosis and development of novel therapeutics for diseases. Here we provide a brief overview of molecular players of programmed cell death with discussion on the role of caspases, modifications, ubiquitylation in apoptosis, removal of the apoptotic body and its relevance to diseases.

Current Status of Patient-Derived Ovarian Cancer Models

Ovarian cancer (OC) is one of the leading causes of female cancer death. Recent studies have documented its extensive variations as a disease entity, in terms of cell or tissue of origin, pre-cancerous lesions, common mutations, and therapeutic responses, leading to the notion that OC is a generic term referring to a whole range of different cancer subtypes. Despite such heterogeneity, OC treatment is stereotypic; aggressive surgery followed by conventional chemotherapy could result in chemo-resistant diseases. Whereas molecular-targeted therapies will become shortly available for a subset of OC, there still remain many patients without effective drugs, requiring development of groundbreaking therapeutic agents. In preclinical studies for drug discovery, cancer cell lines used to be the gold standard, but now this has declined due to frequent failure in predicting therapeutic responses in patients. In this regard, patient-derived cells and tumors are gaining more attention in precise and physiological modeling of in situ tumors, which could also pave the way to implementation of precision medicine. In this article, we comprehensively overviewed the current status of various platforms for patient-derived OC models. We highly appreciate the potentials of organoid culture in achieving high success rate and retaining tumor heterogeneity.

Targeting HER2 in patient-derived xenograft ovarian cancer models sensitizes tumors to chemotherapy

Ovarian cancer is the most lethal gynecologic malignancy. About 75% of ovarian cancer patients relapse and/or develop chemo‐resistant disease after initial response to standard‐of‐care treatment with platinum‐based therapies. HER2 amplifications and overexpression in ovarian cancer are reported to vary, and responses to HER2 inhibitors have been poor. Next generation sequencing technologies in conjunction with testing using patient‐derived xenografts (PDX) allow validation of personalized treatments. Using a whole‐genome mate‐pair next generation sequencing (MPseq) protocol, we identified several high grade serous ovarian cancers (HGS‐OC) with DNA alterations in genes encoding members of the ERBB2 pathway. The efficiency of anti‐HER2 therapy was tested in three different PDX lines with the identified alterations and high levels of HER2 protein expression. Treatment responses to pertuzumab or pertuzumab/trastuzumab were compared in each PDX line WITH standard carboplatin and paclitaxel combination treatment. In all three PDX models, HER2‐targeted therapy resulted in significant inhibition of tumor growth compared with untreated controls. However, the responses in each case were inferior to those to chemotherapy, even for chemo‐resistant lines. When chemotherapy and HER2‐targeted therapy were administered together, a significant regression of tumor was observed after 6 weeks of treatment compared with chemotherapy alone. Post‐treatment analysis of these tissues revealed that inhibition of the ERBB2 pathway occurred at the level of phosphorylation and expression of downstream targets. In conclusion, while targeting of presumably activated ERBB2 pathway alone in HGS‐OC results in a modest treatment benefit, a combination therapy including both chemotherapy drugs and HER2 inhibitors provides a far better response. Further studies are needed to address development of recurrence and sensitivity of recurrent disease to HER2‐targeted therapy.

Optimizing the design of population-based patient-derived tumor xenograft studies to better predict clinical response

The high attrition rate of preclinical agents entering oncology clinical trials has been associated with poor understanding of the heterogeneous patient response, arising from limitations in the preclinical pipeline with cancer models. Patient-derived tumor xenograft (PDX) models have been shown to better recapitulate the patient drug response. However, the platform of evidence generated to support clinical development in a drug discovery project typically employs a limited number of models, which may not accurately predict the response at a population level. Population PDX studies, large-scale screens of PDX models, have been proposed as a strategy to model the patient inter-tumor heterogeneity. Here, we present a freely available interactive tool that explores the design of a population PDX study and how it impacts the sensitivity and false-positive rate experienced. We discuss the reflection process needed to optimize the design for the therapeutic landscape being studied and manage the risk of false-negative and false-positive outcomes that the sponsor is willing to take. The tool has been made freely available to allow the optimal design to be determined for each drug-disease area. This will allow researchers to improve their understanding of treatment efficacy in the presence of genetic variability before taking a drug to clinic. In addition, the tool serves to refine the number of animals to be used for population-based PDX studies, ensuring researchers meet their ethical obligation when performing animal research.

A 3D tumor microenvironment regulates cell proliferation, peritoneal growth and expression patterns

Peritoneal invasion through the mesothelial cell layer is a hallmark of ovarian cancer metastasis. Using tissue engineering technologies, we recreated an ovarian tumor microenvironment replicating this aspect of disease progression. Ovarian cancer cell-laden hydrogels were combined with mesothelial cell-layered melt electrospun written scaffolds and characterized with proliferation and transcriptomic analyses and used as intraperitoneal xenografts. Here we show increased cancer cell proliferation in these 3D co-cultures, which we validated using patient-derived cells and linked to peritoneal tumor growth in vivo. Transcriptome-wide expression analysis identified IGFBP7, PTGS2, VEGFC and FGF2 as bidirectional factors deregulated in 3D co-cultures compared to 3D mono-cultures, which we confirmed by immunohistochemistry of xenograft and patient-derived tumor tissues and correlated with overall and progression-free survival. These factors were further increased upon expression of kallikrein-related proteases. This clinically predictive model allows us to mimic the complexity and processes of the metastatic disease that may lead to therapies that protect from peritoneal invasion or delay the development of metastasis.

Methylation of all BRCA1 copies predicts response to the PARP inhibitor rucaparib in ovarian carcinoma

Accurately identifying patients with high-grade serous ovarian carcinoma (HGSOC) who respond to poly(ADP-ribose) polymerase inhibitor (PARPi) therapy is of great clinical importance. Here we show that quantitative BRCA1 methylation analysis provides new insight into PARPi response in preclinical models and ovarian cancer patients. The response of 12 HGSOC patient-derived xenografts (PDX) to the PARPi rucaparib was assessed, with variable dose-dependent responses observed in chemo-naive BRCA1/2-mutated PDX, and no responses in PDX lacking DNA repair pathway defects. Among BRCA1-methylated PDX, silencing of all BRCA1 copies predicts rucaparib response, whilst heterozygous methylation is associated with resistance. Analysis of 21 BRCA1-methylated platinum-sensitive recurrent HGSOC (ARIEL2 Part 1 trial) confirmed that homozygous or hemizygous BRCA1 methylation predicts rucaparib clinical response, and that methylation loss can occur after exposure to chemotherapy. Accordingly, quantitative BRCA1 methylation analysis in a pre-treatment biopsy could allow identification of patients most likely to benefit, and facilitate tailoring of PARPi therapy.

Characterization of drug responses of mini patient-derived xenografts in mice for predicting cancer patient clinical therapeutic response

Background

Patient-derived organoids and xenografts (PDXs) have emerged as powerful models in functional diagnostics with high predictive power for anticancer drug response. However, limitations such as engraftment failure and time-consuming for establishing and expanding PDX models followed by testing drug efficacy, and inability to subject to systemic drug administration for ex vivo organoid culture hinder realistic and fast decision-making in selecting the right therapeutics in the clinic. The present study aimed to develop an advanced PDX model, namely MiniPDX, for rapidly testing drug efficacy to strengthen its value in personalized cancer treatment.

Methods

We developed a rapid in vivo drug sensitivity assay, OncoVee^® MiniPDX, for screening clinically relevant regimens for cancer. In this model, patient-derived tumor cells were arrayed within hollow fiber capsules, implanted subcutaneously into mice and cultured for 7 days. The cellular activity morphology and pharmacokinetics were systematically evaluated. MiniPDX performance (sensitivity, specificity, positive and negative predictive values) was examined using PDX as the reference. Drug responses were examined by tumor cell growth inhibition rate and tumor growth inhibition rate in PDX models and MiniPDX assays respectively. The results from MiniPDX were also used to evaluate its predictive power for clinical outcomes.

Results

Morphological and histopathological features of tumor cells within the MiniPDX capsules matched those both in PDX models and in original tumors. Drug responses in the PDX tumor graft assays correlated well with those in the corresponding MiniPDX assays using 26 PDX models generated from patients, including 14 gastric cancer, 10 lung cancer and 2 pancreatic cancer. The positive predictive value of MiniPDX was 92%, and the negative predictive value was 81% with a sensitivity of 80% and a specificity of 93%. Through expanding to clinical tumor samples, MiniPDX assay showed potential of wide clinical application.

Conclusions

Fast in vivo MiniPDX assay based on capsule implantation was developed-to assess drug responses of both PDX tumor grafts and clinical cancer specimens. The high correlation between drug responses of paired MiniPDX and PDX tumor graft assay, as well as translational data suggest that MiniPDX assay is an advanced tool for personalized cancer treatment.

Patient-Derived Xenograft Models for Endometrial Cancer Research

Endometrial cancer (EC) is the most common malignancy of the genital tract among women in developed countries. Recently, a molecular classification of EC has been performed providing a system that, in conjunction with histological observations, reliably improves EC classification and enhances patient management. Patient-derived xenograft models (PDX) represent nowadays a promising tool for translational research, since they closely resemble patient tumour features and retain molecular and histological features. In EC, PDX models have already been used, mainly as an individualized approach to evaluate the efficacy of novel therapies and to identify treatment-response biomarkers; however, their uses in more global or holistic approaches are still missing. As a collaborative effort within the ENITEC network, here we describe one of the most extensive EC PDX cohorts developed from primary tumour and metastasis covering all EC subtypes. Our models are histologically and molecularly characterized and represent an excellent reservoir of EC tumour samples for translational research. This review compiles the information on current methods of EC PDX generation and their utility and provides new perspectives for the exploitation of these valuable tools in order to increase the success ratio for translating results to clinical practice.

The latest animal models of ovarian cancer for novel drug discovery

INTRODUCTION

Epithelial ovarian cancer is a heterogeneous disease classified into five subtypes, each with a different molecular profile. Most cases of ovarian cancer are diagnosed after metastasis of the primary tumor and are resistant to traditional platinum-based chemotherapeutics. Mouse models of ovarian cancer have been utilized to discern ovarian cancer tumorigenesis and the tumor's response to therapeutics. Areas covered: The authors provide a review of mouse models currently employed to understand ovarian cancer. This article focuses on advances in the development of orthotopic and patient-derived tumor xenograft (PDX) mouse models of ovarian cancer and discusses current humanized mouse models of ovarian cancer. Expert opinion: The authors suggest that humanized mouse models of ovarian cancer will provide new insight into the role of the human immune system in combating and augmenting ovarian cancer and aid in the development of novel therapeutics. Development of humanized mouse models will take advantage of the NSG and NSG-SGM3 strains of mice as well as new strains that are actively being derived.

Xenopatients show the need for precision medicine approach to chemotherapy in ovarian cancer

Platinum-based chemotherapy is the recommended first-line treatment for high-grade serous (HGS) epithelial ovarian cancer (EOC). However, most patients relapse because of platinum refractory/resistant disease. We aimed at assessing whether other drugs, commonly used to treat relapsed HGS-EOC and poorly active in this clinical setting, might be more effective against chemotherapy-naïve cancers. We collected couples of HGS-EOC samples from the same patients before and after neo-adjuvant platinum-based chemotherapy. Samples were propagated as Patient Derived Xenografts (PDXs) in immunocompromised mice ("xenopatients"). Xenopatients were treated in parallel with carboplatin, gemcitabine, pegylated liposomal doxorubicin (PLD) and trabectedin. PDXs derived from a naïve HSG-EOC showed responsiveness to carboplatin, trabectedin and gemcitabine. The PDXs propagated from a tumor mass of the same patient, grown after carboplatin therapy, did no longer respond to trabectedin and gemcitabine and showed heterogeneous response to carboplatin. In line, the patient experienced clinically platinum-sensitivity first and then discordant responses of different tumor sites to platinum re-challenge. Loss of PDX responsiveness to drugs was associated with 4-fold increase of NR2F2 gene expression. PDXs from another naïve tumor showed complete response to PLD, which was lost in the PDXs derived from a mass grown in the same patient after platinum-based chemotherapy. This patient showed platinum refractoriness and responded poorly to PLD as second-line treatment. PDX response to PLD was associated with high expression of TOP2A protein. PDXs demonstrated that chemotherapy-naïve HGS-EOC might display susceptibility to agents not used commonly as first line treatment. Data suggest the importance of personalizing also chemotherapy.

Ovarian Cancers: Genetic Abnormalities, Tumor Heterogeneity and Progression, Clonal Evolution and Cancer Stem Cells

Four main histological subtypes of ovarian cancer exist: serous (the most frequent), endometrioid, mucinous and clear cell; in each subtype, low and high grade. The large majority of ovarian cancers are diagnosed as high-grade serous ovarian cancers (HGS-OvCas). TP53 is the most frequently mutated gene in HGS-OvCas; about 50% of these tumors displayed defective homologous recombination due to germline and somatic BRCA mutations, epigenetic inactivation of BRCA and abnormalities of DNA repair genes; somatic copy number alterations are frequent in these tumors and some of them are associated with prognosis; defective NOTCH, RAS/MEK, PI3K and FOXM1 pathway signaling is frequent. Other histological subtypes were characterized by a different mutational spectrum: LGS-OvCas have increased frequency of BRAF and RAS mutations; mucinous cancers have mutation in ARID1A, PIK3CA, PTEN, CTNNB1 and RAS. Intensive research was focused to characterize ovarian cancer stem cells, based on positivity for some markers, including CD133, CD44, CD117, CD24, EpCAM, LY6A, ALDH1. Ovarian cancer cells have an intrinsic plasticity, thus explaining that in a single tumor more than one cell subpopulation, may exhibit tumor-initiating capacity. The improvements in our understanding of the molecular and cellular basis of ovarian cancers should lead to more efficacious treatments.

Xenograft as In Vivo Experimental Model

The identification of experimental models that recapitulate human cancers designed to predict patient clinical response to therapies is a major break in oncology. Cancer stem cells (CSCs) represent a small tumor cell population responsible for drug resistance, where their effective killing may lead to identifying better treatment options. While the CSCs hypothesis highlights the need for a specific tumor target, patient-derived xenografts (PDXs) should also be considered for drug development as they better represent tumor heterogeneity and the environment in which a tumor develops.

Comparison of Clinical Features and Outcomes in Epithelial Ovarian Cancer according to Tumorigenicity in Patient-Derived Xenograft Models

Purpose

Although the use of xenograft models is increasing, few studies have compared the clinical features or outcomes of epithelial ovarian cancer (EOC) patients according to the tumorigenicity of engrafted specimens. The purpose of this study was to evaluate whether tumorigenicity was associated with the clinical features and outcomes of EOC patients.

Materials and Methods

Eighty-eight EOC patients who underwent primary or interval debulking surgery from June 2014 to December 2015 were included. Fresh tumor specimens were implanted subcutaneously on each flank of immunodeficient mice. Patient characteristics, progression-free survival (PFS), and germline mutation spectra were compared according to tumorigenicity.

Results

Xenografts were established successfully from 49 of 88 specimens. Tumorigenicity was associated with lymphovascular invasion and there was a propensity to engraft successfully with high-grade tumors. Tumors from patientswho underwent non-optimal (residual disease ≥ 1 cm) primary orinterval debulking surgery had a significantly greater propensity to achieve tumorigenicity than those who received optimal surgery. In addition, patients whose tumors became engrafted seemed to have a shorter PFS and more frequent germline mutations than patients whose tumors failed to engraft. Tumorigenicity was a significant factor for predicting PFS with advanced International Federation of Gynecology and Obstetrics stage and high-grade cancers.

Conclusion

sTumorigenicity in a xenograft model was a strong prognostic factor and was associated with more aggressive tumors in EOC patients. Xenograft models can be useful as a preclinical tool to predict prognosis and could be applied to further pharmacologic and genomic studies on personalized treatments.

Secondary Somatic Mutations Restoring RAD51C and RAD51D Associated with Acquired Resistance to the PARP Inhibitor Rucaparib in High-Grade Ovarian Carcinoma

High-grade epithelial ovarian carcinomas containing mutated BRCA1 or BRCA2 (BRCA1/2) homologous recombination (HR) genes are sensitive to platinum-based chemotherapy and PARP inhibitors (PARPi), while restoration of HR function due to secondary mutations in BRCA1/2 has been recognized as an important resistance mechanism. We sequenced core HR pathway genes in 12 pairs of pretreatment and postprogression tumor biopsy samples collected from patients in ARIEL2 Part 1, a phase II study of the PARPi rucaparib as treatment for platinum-sensitive, relapsed ovarian carcinoma. In 6 of 12 pretreatment biopsies, a truncation mutation in BRCA1, RAD51C, or RAD51D was identified. In five of six paired postprogression biopsies, one or more secondary mutations restored the open reading frame. Four distinct secondary mutations and spatial heterogeneity were observed for RAD51CIn vitro complementation assays and a patient-derived xenograft, as well as predictive molecular modeling, confirmed that resistance to rucaparib was associated with secondary mutations.Significance: Analyses of primary and secondary mutations in RAD51C and RAD51D provide evidence for these primary mutations in conferring PARPi sensitivity and secondary mutations as a mechanism of acquired PARPi resistance. PARPi resistance due to secondary mutations underpins the need for early delivery of PARPi therapy and for combination strategies. Cancer Discov; 7(9); 984-98. ©2017 AACR.See related commentary by Domchek, p. 937See related article by Quigley et al., p. 999See related article by Goodall et al., p. 1006This article is highlighted in the In This Issue feature, p. 920.

Systems analysis of apoptotic priming in ovarian cancer identifies vulnerabilities and predictors of drug response

The lack of effective chemotherapies for high-grade serous ovarian cancers (HGS-OvCa) has motivated a search for alternative treatment strategies. Here, we present an unbiased systems-approach to interrogate a panel of 14 well-annotated HGS-OvCa patient-derived xenografts for sensitivity to PI3K and PI3K/mTOR inhibitors and uncover cell death vulnerabilities. Proteomic analysis reveals that PI3K/mTOR inhibition in HGS-OvCa patient-derived xenografts induces both pro-apoptotic and anti-apoptotic signaling responses that limit cell killing, but also primes cells for inhibitors of anti-apoptotic proteins. In-depth quantitative analysis of BCL-2 family proteins and other apoptotic regulators, together with computational modeling and selective anti-apoptotic protein inhibitors, uncovers new mechanistic details about apoptotic regulators that are predictive of drug sensitivity (BIM, caspase-3, BCL-X_L) and resistance (MCL-1, XIAP). Our systems-approach presents a strategy for systematic analysis of the mechanisms that limit effective tumor cell killing and the identification of apoptotic vulnerabilities to overcome drug resistance in ovarian and other cancers.High-grade serous ovarian cancers (HGS-OvCa) frequently develop chemotherapy resistance. Here, the authors through a systematic analysis of proteomic and drug response data of 14 HGS-OvCa PDXs demonstrate that targeting apoptosis regulators can improve response of these tumors to inhibitors of the PI3K/mTOR pathway.

Systems analysis of apoptotic priming in ovarian cancer identifies vulnerabilities and predictors of drug response

The lack of effective chemotherapies for high-grade serous ovarian cancers (HGS-OvCa) has motivated a search for alternative treatment strategies. Here, we present an unbiased systems-approach to interrogate a panel of 14 well-annotated HGS-OvCa patient-derived xenografts for sensitivity to PI3K and PI3K/mTOR inhibitors and uncover cell death vulnerabilities. Proteomic analysis reveals that PI3K/mTOR inhibition in HGS-OvCa patient-derived xenografts induces both pro-apoptotic and anti-apoptotic signaling responses that limit cell killing, but also primes cells for inhibitors of anti-apoptotic proteins. In-depth quantitative analysis of BCL-2 family proteins and other apoptotic regulators, together with computational modeling and selective anti-apoptotic protein inhibitors, uncovers new mechanistic details about apoptotic regulators that are predictive of drug sensitivity (BIM, caspase-3, BCL-X_L) and resistance (MCL-1, XIAP). Our systems-approach presents a strategy for systematic analysis of the mechanisms that limit effective tumor cell killing and the identification of apoptotic vulnerabilities to overcome drug resistance in ovarian and other cancers.

High-grade serous ovarian cancers (HGS-OvCa) frequently develop chemotherapy resistance. Here, the authors through a systematic analysis of proteomic and drug response data of 14 HGS-OvCa PDXs demonstrate that targeting apoptosis regulators can improve response of these tumors to inhibitors of the PI3K/mTOR pathway.

Systems analysis of apoptotic priming in ovarian cancer identifies vulnerabilities and predictors of drug response

The lack of effective chemotherapies for high-grade serous ovarian cancers (HGS-OvCa) has motivated a search for alternative treatment strategies. Here, we present an unbiased systems-approach to interrogate a panel of 14 well-annotated HGS-OvCa patient-derived xenografts for sensitivity to PI3K and PI3K/mTOR inhibitors and uncover cell death vulnerabilities. Proteomic analysis reveals that PI3K/mTOR inhibition in HGS-OvCa patient-derived xenografts induces both pro-apoptotic and anti-apoptotic signaling responses that limit cell killing, but also primes cells for inhibitors of anti-apoptotic proteins. In-depth quantitative analysis of BCL-2 family proteins and other apoptotic regulators, together with computational modeling and selective anti-apoptotic protein inhibitors, uncovers new mechanistic details about apoptotic regulators that are predictive of drug sensitivity (BIM, caspase-3, BCL-X_L) and resistance (MCL-1, XIAP). Our systems-approach presents a strategy for systematic analysis of the mechanisms that limit effective tumor cell killing and the identification of apoptotic vulnerabilities to overcome drug resistance in ovarian and other cancers.High-grade serous ovarian cancers (HGS-OvCa) frequently develop chemotherapy resistance. Here, the authors through a systematic analysis of proteomic and drug response data of 14 HGS-OvCa PDXs demonstrate that targeting apoptosis regulators can improve response of these tumors to inhibitors of the PI3K/mTOR pathway.

Combination of paclitaxel, bevacizumab and MEK162 in second line treatment in platinum-relapsing patient derived ovarian cancer xenografts

Advanced ovarian cancer is very responsive to first line platinum therapy, however almost invariably it relapses with a resistant disease. We have reported that patient derived ovarian xenografts (PDXs), independently from the degree of the initial response to cisplatin (DDP), show a significantly lower response to a second DDP cycle. We here report the effect of new combination regimens containing a MEK inhibitor (MEK), bevacizumab (BEV) and paclitaxel (PTX) as second line therapy in platinum-relapsing PDXs.

We selected three DDP-relapsing PDX models based on the presence of activation of the RAS/RAF/MEK/ERK axis, mutated p53, lack of PTEN expression and activation of the PI3K pathway. In all the selected xenograft models, the antitumor efficacy of the doublets can be summarized as PTX/BEV > BEV/MEK > PTX/MEK and the antitumor activity of the triple combination was higher than any double combination. All the different combinations were well tolerated. The present data corroborate the activity of bevacizumab in combination with chemotherapy for the treatment of relapsing ovarian tumors and suggest that the addition of another targeted agents (MEK inhibitor) can further increase the antitumor activity without any increase in toxicity. PDX models represent a useful model to test second line therapy after failure of DDP first line.

B-Cell Lymphoma Patient-Derived Xenograft Models Enable Drug Discovery and Are a Platform for Personalized Therapy

Purpose: Patients with B-cell lymphomas often relapse after frontline therapy, and novel therapies are urgently needed to provide long-term remission. We established B-cell lymphoma patient-derived xenograft (PDX) models to assess their ability to mimic tumor biology and to identify B-cell lymphoma patient treatment options.Experimental Design: We established the PDX models from 16 patients with diffuse large B-cell lymphoma, mantle cell lymphoma, follicular lymphoma, marginal zone lymphoma, or Burkitt lymphoma by inoculating the patient tumor cells into a human bone chip implanted into mice. We subjected the PDX models to histopathologic and phenotypical examination, sequencing, and drug efficacy analysis. Primary and acquired resistance to ibrutinib, an oral covalent inhibitor of Bruton tyrosine kinase, were investigated to elucidate the mechanisms underlying ibrutinib resistance and to identify drug treatments to overcome resistance.Results: The PDXs maintained the same biological, histopathologic, and immunophenotypical features, retained similar genetic mutations, and produced comparable drug responses with the original patient tumors. In the acquired ibrutinib-resistant PDXs, PLC-γ2, p65, and Src were downregulated; however, a PI3K signaling pathway member was upregulated. Inactivation of the PI3K pathway with the inhibitor idelalisib in combination with ibrutinib significantly inhibited the growth of the ibrutinib-resistant tumors. Furthermore, we used a PDX model derived from a clinically ibrutinib-relapsed patient to evaluate various therapeutic choices, ultimately eliminating the tumor cells in the patient's peripheral blood.Conclusions: Our results demonstrate that the B-cell lymphoma PDX model is an effective system to predict and personalize therapies and address therapeutic resistance in B-cell lymphoma patients. Clin Cancer Res; 23(15); 4212-23. ©2017 AACR.

Recent Advances in Understanding, Diagnosing, and Treating Ovarian Cancer

Ovarian cancer, a term that encompasses ovarian, fallopian, and peritoneal cancers, is the leading cause of gynecologic cancer mortality. To improve patient outcomes, the field is currently focused on defining the mechanisms of cancer formation and spread, early diagnosis and prevention, and developing novel therapeutic options. This review summarizes recent advances in these areas.

Patient-Derived Xenograft Models of Epithelial Ovarian Cancer for Preclinical Studies

Purpose

Patient-derived tumor xenografts (PDXs) can provide more reliable information about tumor biology than cell line models. We developed PDXs for epithelial ovarian cancer (EOC) that have histopathologic and genetic similarities to the primary patient tissues and evaluated their potential for use as a platform for translational EOC research.

Materials and Methods

We successfully established PDXs by subrenal capsule implantation of primary EOC tissues into female BALB/C-nude mice. The rate of successful PDX engraftment was 48.8% (22/45 cases). Hematoxylin and eosin staining and short tandem repeat analysis showed histopathological and genetic similarity between the PDX and primary patient tissues.

Results

Patients whose tumors were successfully engrafted in mice had significantly inferior overall survival when compared with those whose tumors failed to engraft (p=0.040). In preclinical tests of this model, we found that paclitaxel-carboplatin combination chemotherapy significantly deceased tumor weight in PDXs compared with the control treatment (p=0.013). Moreover, erlotinib treatment significantly decreased tumor weight in epidermal growth factor receptor–overexpressing PDX with clear cell histology (p=0.023).

Conclusion

PDXs for EOC with histopathological and genetic stability can be efficiently developed by subrenal capsule implantation and have the potential to provide a promising platform for future translational research and precision medicine for EOC.

Targeting the ATR/CHK1 Axis with PARP Inhibition Results in Tumor Regression in BRCA-Mutant Ovarian Cancer Models

Purpose: PARP inhibition (PARPi) has modest clinical activity in recurrent BRCA-mutant (BRCA^MUT) high-grade serous ovarian cancers (HGSOC). We hypothesized that PARPi increases dependence on ATR/CHK1 such that combination PARPi with ATR/CHK1 blockade results in increased cell death and tumor regression.Experimental Design: Effects of PARPi (olaparib), CHK1 inhibition (CHK1i;MK8776), or ATR inhibition (ATRi;AZD6738) alone or in combination on survival, colony formation, cell cycle, genome instability, and apoptosis were evaluated in BRCA1/2^MUT HGSOC cells. Tumor growth in vivo was evaluated using a BRCA2^MUT patient-derived xenograft (PDX) model.Results: PARPi monotherapy resulted in a decrease in BRCA^MUT cell survival, colony formation and suppressed but did not eliminate tumor growth at the maximum tolerated dose (MTD) in a BRCA2^MUT PDX. PARPi treatment increased pATR and pCHK1, indicating activation of the ATR-CHK1 fork protection pathway is relied upon for genome stability under PARPi. Indeed, combination of ATRi or CHK1i with PARPi synergistically decreased survival and colony formation compared with single-agent treatments in BRCA^MUT cells. Notably, PARPi led to G₂ phase accumulation, and the addition of ATRi or CHK1i released cells from G₂ causing premature mitotic entry with increased chromosomal aberrations and apoptosis. Moreover, the combinations of PARPi with ATRi or CHK1i were synergistic in causing tumor suppression in a BRCA2^MUT PDX with the PARPi-ATRi combination inducing tumor regression and in most cases, complete remission.Conclusions: PARPi causes increased reliance on ATR/CHK1 for genome stability, and combination PARPi with ATR/CHK1i is more effective than PARPi alone in reducing tumor burden in BRCA^MUT models. Clin Cancer Res; 23(12); 3097-108. ©2016 AACR.

Epigenetic inactivation of the putative DNA/RNA helicase SLFN11 in human cancer confers resistance to platinum drugs

Platinum-derived drugs such as cisplatin and carboplatin are among the most commonly used cancer chemotherapy drugs, but very few specific molecular and cellular markers predicting differential sensitivity to these agents in a given tumor type have been clearly identified. Epigenetic gene silencing is increasingly being recognized as a factor conferring distinct tumoral drug sensitivity, so we have used a comprehensive DNA methylation microarray platform to interrogate the widely characterized NCI60 panel of human cancer cell lines with respect to CpG methylation status and cisplatin/carboplatin sensitivity. Using this approach, we have found promoter CpG island hypermethylation-associated silencing of the putative DNA/RNA helicase Schlafen-11 (SLFN11) to be associated with increased resistance to platinum compounds. We have also experimentally validated these findings in vitro. In this setting, we also identified the BRCA1 interacting DHX9 RNA helicase (also known as RHA) as a protein partner for SLFN11, suggesting a mechanistic pathway for the observed chemoresistance effect. Most importantly, we have been able to extend these findings clinically, following the observation that those patients with ovarian and non-small cell lung cancer carrying SLFN11 hypermethylation had a poor response to both cisplatin and carboplatin treatments. Overall, these results identify SLFN11 epigenetic inactivation as a predictor of resistance to platinum drugs in human cancer.

Patient-derived xenografts: a relevant preclinical model for drug development

Identifying appropriate preclinical cancer models remains a major challenge in increasing the efficiency of drug development. A potential strategy to improve patient outcomes could be selecting the ‘right’ treatment in preclinical studies performed in patient-derived xenografts (PDXs) obtained by direct implants of surgically resected tumours in mice. These models maintain morphological similarities and recapitulate molecular profiling of the original tumours, thus representing a useful tool in evaluating anticancer drug response. In this review, we will present the state-of-art use of PDXs as a reliable strategy to predict clinical findings. The main advantages and limitations will also be discussed.

Genome-wide methylation profiling of ovarian cancer patient-derived xenografts treated with the demethylating agent decitabine identifies novel epigenetically regulated genes and pathways

Background

In high-grade serous ovarian cancer (HGSOC), intrinsic and/or acquired resistance against platinum-containing chemotherapy is a major obstacle for successful treatment. A low frequency of somatic mutations but frequent epigenetic alterations, including DNA methylation in HGSOC tumors, presents the cancer epigenome as a relevant target for innovative therapy. Patient-derived xenografts (PDXs) supposedly are good preclinical models for identifying novel drug targets. However, the representativeness of global methylation status of HGSOC PDXs compared to their original tumors has not been evaluated so far. Aims of this study were to explore how representative HGSOC PDXs are of their corresponding patient tumor methylome and to evaluate the effect of epigenetic therapy and cisplatin on putative epigenetically regulated genes and their related pathways in PDXs.

Methods

Genome-wide analysis of the DNA methylome of HGSOC patients with their corresponding PDXs, from different generations, was performed using Infinium 450 K methylation arrays. Furthermore, we analyzed global methylome changes after treatment of HGSOC PDXs with the FDA approved demethylating agent decitabine and cisplatin. Findings were validated by bisulfite pyrosequencing with subsequent pathway analysis. Publicly available datasets comprising HGSOC patients were used to analyze the prognostic value of the identified genes.

Results

Only 0.6–1.0 % of all analyzed CpGs (388,696 CpGs) changed significantly (p < 0.01) during propagation, showing that HGSOC PDXs were epigenetically stable. Treatment of F3 PDXs with decitabine caused a significant reduction in methylation in 10.6 % of CpG sites in comparison to untreated PDXs (p < 0.01, false discovery rate <10 %). Cisplatin treatment had a marginal effect on the PDX methylome. Pathway analysis of decitabine-treated PDX tumors revealed several putative epigenetically regulated pathways (e.g., the Src family kinase pathway). In particular, the C-terminal Src kinase (CSK) gene was successfully validated for epigenetic regulation in different PDX models and ovarian cancer cell lines. Low CSK methylation and high CSK expression were both significantly associated (p < 0.05) with improved progression-free survival and overall survival in HGSOC patients.

Conclusions

HGSOC PDXs resemble the global epigenome of patients over many generations and can be modulated by epigenetic drugs. Novel epigenetically regulated genes such as CSK and related pathways were identified in HGSOC. Our observations encourage future application of PDXs for cancer epigenome studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-016-0361-5) contains supplementary material, which is available to authorized users.

Histologic and molecular analysis of patient derived xenografts of high-grade serous ovarian carcinoma

BACKGROUND

Patient derived xenografts (PDX) are generated by transplanting the original patient's tumor tissue into immune-deficient mice. Unlike xenograft models derived from cell lines, PDX models can better preserve the histopathology from the original patient and molecular pathways. High-grade serous carcinoma (HGSC) is a deadly form of ovarian/fallopian tube cancer whose response to current chemotherapies varies widely due to patient variability. Therefore, a PDX model can provide a valuable tool to study and test treatment options for each individual patient.

METHODS

In this study, over 200 PDX tumors from nine HGSC were analyzed to investigate the nature and behavior of PDX tumors originating from HGSC. PDX tumors were serially passaged (from P0 to P4) and tumors were grafted orthotopically under the ovarian bursa or subcutaneously.

RESULTS

Comparative analysis of the histology and molecular markers of tumors from over 200 PDX tumor-bearing mice, revealed that the tumors maintained similar histologies, stem cell populations, and expression for the majority of the tested oncogenic markers, compared to the primary tumors. However, a significant loss of steroid hormone receptors and altered expression of immunoresponsive genes in PDX tumors were also noted.

CONCLUSION

Our findings provide substantial new information about PDX tumor characteristics from HGSC which will be valuable towards the development of personalized therapy and new drug development for HGSC.

Establishment of Patient-Derived Tumor Xenograft Models of Epithelial Ovarian Cancer for Preclinical Evaluation of Novel Therapeutics

Purpose: Ovarian cancer is the leading cause of death from gynecologic malignancy in the United States, with high rates of recurrence and eventual resistance to cytotoxic chemotherapy. Model systems that allow for accurate and reproducible target discovery and validation are needed to support further drug development in this disease.Experimental Design: Clinically annotated patient-derived xenograft (PDX) models were generated from tumor cells isolated from the ascites or pleural fluid of patients undergoing clinical procedures. Models were characterized by IHC and by molecular analyses. Each PDX was luciferized to allow for reproducible in vivo assessment of intraperitoneal tumor burden by bioluminescence imaging (BLI). Plasma assays for CA125 and human LINE-1 were developed as secondary tests of in vivo disease burden.Results: Fourteen clinically annotated and molecularly characterized luciferized ovarian PDX models were generated. Luciferized PDX models retain fidelity to both the nonluciferized PDX and the original patient tumor, as demonstrated by IHC, array CGH, and targeted and whole-exome sequencing analyses. Models demonstrated diversity in specific genetic alterations and activation of PI3K signaling pathway members. Response of luciferized PDX models to standard-of-care therapy could be reproducibly monitored by BLI or plasma markers.Conclusions: We describe the establishment of a collection of 14 clinically annotated and molecularly characterized luciferized ovarian PDX models in which orthotopic tumor burden in the intraperitoneal space can be followed by standard and reproducible methods. This collection is well suited as a platform for proof-of-concept efficacy and biomarker studies and for validation of novel therapeutic strategies in ovarian cancer. Clin Cancer Res; 23(5); 1263-73. ©2016 AACR.

Ovarian carcinoma patient derived xenografts reproduce their tumor of origin and preserve an oligoclonal structure

Advanced Epithelial Ovarian Cancer (EOC) patients frequently relapse by 24 months and develop resistant disease. Research on EOC therapies relies on cancer cell lines established decades ago making Patient Derived Xenografts (PDX) attractive models, because they are faithful representations of the original tumor. We established 35 ovarian cancer PDXs resulting from the original graft of 77 EOC samples onto immuno-compromised mice. PDXs covered the diversity of EOC histotypes and graft take was correlated with early patient death. Fourteen PDXs were characterized at the genetic and histological levels. PDXs reproduced phenotypic features of the ovarian tumors of origin and conserved the principal characteristics of the original copy number change (CNC) profiles over several passages. However, CNC fluctuations in specific subregions comparing the original tumor and the PDXs indicated the oligoclonal nature of the original tumors. Detailed analysis by CGH, FISH and exome sequencing of one case, for which several tumor nodules were sampled and grafted, revealed that PDXs globally maintained an oligoclonal structure. No overgrowth of a particular subclone present in the original tumor was observed in the PDXs. This suggested that xenotransplantation of ovarian tumors and growth as PDX preserved at least in part the clonal diversity of the original tumor. We believe our data reinforce the potential of PDX as exquisite tools in pre-clinical assays.

Panobinostat sensitizes cyclin E high, homologous recombination-proficient ovarian cancer to olaparib

OBJECTIVE

Homologous recombination (HR) proficient ovarian cancers, including CCNE1 (cyclin E)-amplified tumors, are resistant to poly (ADP-ribose) polymerase inhibitors (PARPi). Histone deacetylase inhibitors (HDACi) are effective in overcoming tumor resistance to DNA damaging drugs. Our goal was to determine whether panobinostat, a newly FDA-approved HDACi, can sensitize cyclin E, HR-proficient ovarian cancer cells to the PARPi olaparib.

METHODS

Expression levels of CCNE1 (cyclin E), BRCA1, RAD51 and E2F1 in ovarian tumors and cell lines were extracted from The Cancer Genome Atlas (TCGA) and Broad-Novartis Cancer Cell Line Encyclopedia (CCLE). In HR-proficient ovarian cancer cell line models (OVCAR-3, OVCAR-4, SKOV-3, and UWB1.289+BRCA1 wild-type), cell growth and viability were assessed by sulforhodamine B and xenograft assays. DNA damage and repair (pH2AX and RAD51 co-localization and DRGFP reporter activity) and apoptosis (cleaved PARP and cleaved caspase-3) were assessed by immunofluorescence and Western blot assays.

RESULTS

TCGA and CCLE data revealed positive correlations (Spearman) between cyclin E E2F1, and E2F1 gene targets related to DNA repair (BRCA1 and RAD51). Panobinostat downregulated cyclin E and HR repair pathway genes, and reduced HR efficiency in cyclin E-amplified OVCAR-3 cells. Further, panobinostat synergized with olaparib in reducing cell growth and viability in HR-proficient cells. Similar co-operative effects were observed in xenografts, and on pharmacodynamic markers of HR repair, DNA damage and apoptosis.

CONCLUSIONS

These results provide preclinical rationale for using HDACi to reduce HR in cyclin E-overexpressing and other types of HR-proficient ovarian cancer as a means of enhancing PARPi activity.

Inhibiting MDM2-p53 Interaction Suppresses Tumor Growth in Patient-Derived Non-Small Cell Lung Cancer Xenograft Models

BACKGROUND

The tumor suppressor p53 is frequently inactivated in non-small cell lung cancer (NSCLC). Activation of the p53 pathway by inhibition of its negative regulator MDM2 may offer an attractive approach for NSCLC therapy. We evaluated the antitumor activity of the small-molecule MDM2 inhibitor RG7388 in patient-derived xenograft (PDX) models of NSCLC.

METHODS

We investigated the effect of RG7388 treatment on cell proliferation, cell cycle arrest, and apoptosis using a panel of human NSCLC cell lines (A549, H157, H1650, H1395, and H358) and PDX cell lines (human lung cell lines 12, 137, 277, and 196). PDX-bearing mice were used to test the therapeutic efficacy and pharmacodynamic effects of RG7388 treatment.

RESULTS

We demonstrated that RG7388 promotes low nanomolar antiproliferative activity selectively in cell lines with wild-type p53 and p53 pathway activation, resulting in cell cycle arrest and apoptosis. In PDX models, oral administration of RG7388 led to potent dose-dependent and time-dependent activation of p53 and had a significant impact on p53 downstream targets. Daily treatment of RG7388 in mice at 50 and 80 mg/kg/day inhibited tumor growth in three wild-type p53 PDX models. Activation of the p53 pathway inhibited cell proliferation as observed by reduced Ki-67-positive cells in xenograft tumors. However, induction of apoptotic caspase activity was not observed in these tumors. Notably, RG7388 treatment remains effective in tumors lacking MDM2 amplification but expressing wild-type p53.

CONCLUSIONS

MDM2 small-molecule inhibitor is effective in treating NSCLC tumors with wild-type p53, supporting further clinical investigation as a potential NSCLC therapy.

Molecular and clinical implementations of ovarian cancer mouse avatar models

Innovation in oncology drug development has been hindered by lack of preclinical models that reliably predict clinical activity of novel therapies in cancer patients. Increasing desire for individualize treatment of patients with cancer has led to an increase in the use of patient-derived xenografts (PDX) engrafted into immune-compromised mice for preclinical modeling. Large numbers of tumor-specific PDX models have been established and proved to be powerful tools in pre-clinical testing. A subset of PDXs, referred to as Avatars, establish tumors in an orthotopic and treatment naïve fashion that may represent the most clinical relevant model of individual human cancers. This review will discuss ovarian cancer (OC) PDX models demonstrating the opportunities and limitations of these models in cancer drug development, and describe concepts of clinical trials design in Avatar guided therapy.

It's Totally Tubular....Riding The New Wave of Ovarian Cancer Research

Hereditary breast and ovarian cancer syndrome carries significant mortality for young women if effective preventive and screening measures are not taken. Preventive salpingo-oophorectomy is currently the only method known to reduce the risk of ovarian cancer-related death. Histopathological analyses of these surgical specimens indicate that a high proportion of ovarian cancers in women at high risk and in the general population arise from the fallopian tube. This paradigm shift concerning the cell of origin for the most common subtype of ovarian cancer, high-grade serous carcinoma, has sparked a major effort within the research community to develop new and robust model systems to study the fallopian tube epithelium as the cell of origin of "ovarian" cancer. In this review, evidence supporting the fallopian tube as the origin of ovarian cancer is presented as are novel experimental model systems for studying the fallopian tube epithelium in high-risk women as well as in the general population. This review also addresses the clinical implications of the newly proposed cell of origin, the clinical questions that arise, and novel strategies for ovarian cancer prevention.

Studying platinum sensitivity and resistance in high-grade serous ovarian cancer: Different models for different questions

High-grade serous ovarian cancer (HGSOC) has the highest mortality rate among all gynecological cancers. Patients are generally diagnosed in an advanced stage with the majority of cases displaying platinum resistant relapses. Recent genomic interrogation of large numbers of HGSOC patient samples indicated high complexity in terms of genetic aberrations, intra- and intertumor heterogeneity and underscored their lack of targetable oncogenic mutations. Sub-classifications of HGSOC based on expression profiles, termed 'differentiated', 'immunoreactive', 'mesenchymal' and 'proliferative', were shown to have prognostic value. In addition, in almost half of all HGSOC patients, a deficiency in homologous recombination (HR) was found that potentially can be targeted using PARP inhibitors. Developing precision medicine requires advanced experimental models. In the current review, we discuss experimental HGSOC models in which resistance to platinum therapy and the use of novel therapeutics can be carefully studied. Panels of better-defined primary cell lines need to be established to capture the full spectrum of HGSOC subtypes. Further refinement of cell lines is obtained with a 3-dimensional culture model mimicking the tumor microenvironment. Alternatively, ex vivo ovarian tumor tissue slices are used. For in vivo studies, larger panels of ovarian cancer patient-derived xenografts (PDXs) are being established, encompassing all expression subtypes. Ovarian cancer PDXs grossly retain tumor heterogeneity and clinical response to platinum therapy is preserved. PDXs are currently used in drug screens and as avatars for patient response. The role of the immune system in tumor responses can be assessed using humanized PDXs and immunocompetent genetically engineered mouse models. Dynamic tracking of genetic alterations in PDXs as well as patients during treatment and after relapse is feasible by sequencing circulating cell-free tumor DNA and analyzing circulating tumor cells. We discuss how various models and methods can be combined to delineate the molecular mechanisms underlying platinum resistance and to select HGSOC patients other than BRCA1/2-mutation carriers that could potentially benefit from the synthetic lethality of PARP inhibitors. This integrated approach is a first step to improve therapy outcomes in specific subgroups of HGSOC patients.

Patient-derived xenograft models in gynecologic malignancies

In the era of targeted therapies, patients with gynecologic malignancies have not yet been major beneficiaries of this new class of agents. This may reflect the fact that the main tumor types-ovarian, uterine, and cervical--are a highly heterogeneous group of cancers with variable response to standard chemotherapies and the lack of models in which to study the diversity of these cancers. Cancer-derived cell lines fail to adequately recapitulate molecular hallmarks of specific cancer subsets and complex microenvironments, which may be critical for sensitivity to targeted therapies. Patient-derived xenografts (PDX) generated from fresh human tumor without prior in vitro culture, combined with whole genome expression, gene copy number, and sequencing analyses, could dramatically aid the development of novel therapies for gynecologic malignancies. Gynecologic tumors can be engrafted in immunodeficient mice with a high rate of success and within a reasonable time frame. The resulting PDX accurately recapitulates the patient's tumor with respect to histologic, molecular, and in vivo treatment response characteristics. Orthotopic PDX develop complications relevant to the clinic, such as ascites and bowel obstruction, providing opportunities to understand the biology of these clinical problems. Thus, PDX have great promise for improved understanding of gynecologic malignancies, serve as better models for designing novel therapies and clinical trials, and could underpin individualized, directed therapy for patients from whom such models have been established.

Rethinking ovarian cancer II: reducing mortality from high-grade serous ovarian cancer

High-grade serous ovarian cancer (HGSOC) accounts for 70-80% of ovarian cancer deaths, and overall survival has not changed significantly for several decades. In this Opinion article, we outline a set of research priorities that we believe will reduce incidence and improve outcomes for women with this disease. This 'roadmap' for HGSOC was determined after extensive discussions at an Ovarian Cancer Action meeting in January 2015.

Rethinking ovarian cancer II: reducing mortality from high-grade serous ovarian cancer

High-grade serous ovarian cancer (HGSOC) accounts for 70-80% of ovarian cancer deaths, and overall survival has not changed significantly for several decades. In this Opinion article, we outline a set of research priorities that we believe will reduce incidence and improve outcomes for women with this disease. This 'roadmap' for HGSOC was determined after extensive discussions at an Ovarian Cancer Action meeting in January 2015.

Rethinking ovarian cancer II: reducing mortality from high-grade serous ovarian cancer

High-grade serous ovarian cancer (HGSOC) accounts for 70-80% of ovarian cancer deaths, and overall survival has not changed significantly for several decades. In this Opinion article, we outline a set of research priorities that we believe will reduce incidence and improve outcomes for women with this disease. This 'roadmap' for HGSOC was determined after extensive discussions at an Ovarian Cancer Action meeting in January 2015.