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.

Primary CNS lymphoma patient-derived orthotopic xenograft model capture the biological and molecular characteristics of the disease.

Primary CNS lymphomas (PCNSL) are rare and poor prognosis diffuse large B-cell lymphomas. Because of the brain tumor environment and the restricted distribution of drugs in the CNS, specific PCNSL patient-derived orthotopic xenograft (PDOX) models are needed for preclinical research to improve the prognosis of PCNSL patients. PCNSL patient specimens (n = 6) were grafted in the caudate nucleus of immunodeficient nude mice with a 83% rate of success, while subcutaneous implantation in nude mice of human PCNSL sample did not generate lymphoma, supporting the role of the brain microenvironment in the PCNSL physiopathology. PDOXs showed diffuse infiltration of B-cell lymphoma cells in the brain parenchyma. Each model had a unique mutational signature for genes in the BCR and NF-κB pathways and retained the mutational profile of the primary tumor. The models can be stored as cryopreserved biobank. Human IL-10 levels measured in the plasma of PCNSL-PDOX mice showed to be a reliable tool to monitor the tumor burden. Treatment response could be measured after a short treatment with the targeted therapy ibrutinib. In summary, we established a panel of human PCNSL-PDOX models that capture the histological and molecular characteristics of the disease and that proved suitable for preclinical experiments. Our methods of generation and characterization will enable the generation of additional PDOX-PCNSL models, essential tools for cognitive and preclinical drug discovery.

The iron chelator deferasirox synergises with chemotherapy to treat triple-negative breast cancers.

To ensure their high proliferation rate, tumor cells have an iron metabolic disorder causing them to have increased iron needs, making them more susceptible to iron deprivation. This vulnerability could be a therapeutic target. In breast cancers, the development of new therapeutic approaches is urgently needed for patients with triple-negative tumors, which frequently relapse after chemotherapy and suffer from a lack of targeted therapies. In this study, we demonstrated that deferasirox (DFX) synergises with standard chemotherapeutic agents such as doxorubicin, cisplatin and carboplatin to inhibit cell proliferation and induce apoptosis and autophagy in triple-negative breast cancer (TNBC) cells. Moreover, the combination of DFX with doxorubicin and cyclophosphamide delayed recurrences in breast cancer patient-derived xenografts without increasing the side-effects of chemotherapies alone or altering the global iron storage of mice. Antitumor synergy of DFX and doxorubicin seems to involve downregulation of the phosphoinositide 3-kinase and nuclear factor-κB pathways. Iron deprivation in combination with chemotherapy could thus help to improve the effectiveness of chemotherapy in TNBC patients without increasing toxicity. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

HDAC inhibition does not induce estrogen receptor in human triple-negative breast cancer cell lines and patient-derived xenografts.

Several publications have suggested that histone deacetylase inhibitors (HDACis) could reverse the repression of estrogen receptor alpha (ERα) in triple-negative breast cancer (TNBC) cell lines, leading to the induction of a functional protein. Using different HDACis, vorinostat, panobinostat, and abexinostat, we therefore investigated this hypothesis in various human TNBC cell lines and patient-derived xenografts (PDXs). We used three human TNBC cell lines and three PDXs. We analyzed the in vitro toxicity of the compounds, their effects on the hormone receptors and hormone-related genes and protein expression both in vitro and in vivo models. We then explored intra-tumor histone H3 acetylation under abexinostat in xenograft models. Despite major cytotoxicity of all tested HDAC inhibitors and repression of deactylation-dependent CCND1 gene, neither ERα nor ERß, ESR1 or ESR2 genes respectively, were re-expressed in vitro. In vivo, after administration of abexinostat for three consecutive days, we did not observe any induction of ESR1 or ESR1-related genes and ERα protein expression by RT-qPCR and immunohistochemical methods in PDXs. This observation was concomitant to the fact that in vivo administration of abexinostat increased intra-tumor histone H3 acetylation. These observations do not allow us to confirm previous studies which suggested that HDACis are able to convert ER-negative (ER-) tumors to ER-positive (ER+) tumors, and that a combination of HDAC inhibitors and hormone therapy could be proposed in the management of TNBC patients.

Two-photon microscopy for microrobotics: Visualization of micro-agents below fixed tissue.

Optical microscopy is frequently used to visualize microrobotic agents (i.e., micro-agents) and physical surroundings with a relatively high spatio-temporal resolution. However, the limited penetration depth of optical microscopy techniques used in microrobotics (in the order of 100 µm) reduces the capability of visualizing micro-agents below biological tissue. Two-photon microscopy is a technique that exploits the principle of two-photon absorption, permitting live tissue imaging with sub-micron resolution and optical penetration depths (over 500 µm). The two-photon absorption principle has been widely applied to fabricate sub-millimeter scale components via direct laser writing (DLW). Yet, its use as an imaging tool for microrobotics remains unexplored in the state-of-the-art. This study introduces and reports on two-photon microscopy as an alternative technique for visualizing micro-agents below biological tissue. In order to validate two-photon image acquisition for microrobotics, two-type micro-agents are fabricated and employed: (1) electrospun fibers stained with an exogenous fluorophore and (2) bio-inspired structure printed with autofluorescent resin via DLW. The experiments are devised and conducted to obtain three-dimensional reconstructions of both micro-agents, perform a qualitative study of laser-tissue interaction, and visualize micro-agents along with tissue using second-harmonic generation. We experimentally demonstrate two-photon microscopy of micro-agents below formalin-fixed tissue with a maximum penetration depth of 800 µm and continuous imaging of magnetic electrospun fibers with one frame per second acquisition rate (in a field of view of 135 × 135 µm2). Our results show that two-photon microscopy can be an alternative imaging technique for microrobotics by enabling visualization of micro-agents under in vitro and ex ovo conditions. Furthermore, bridging the gap between two-photon microscopy and the microrobotics field has the potential to facilitate in vivo visualization of micro-agents.

Patient Derived Xenografts (PDX) Models as an Avatar to Assess Personalized Therapy Options in Uveal Melanoma: A Feasibility Study.

Uveal melanoma is the most common primary intraocular malignancy in adults. Up to 50% of UM patients develop metastatic disease, usually in the liver. When metastatic, the prognosis is poor, and few treatment options exist. Here, we investigated the feasibility of establishing patient-derived xenografts (PDXs) from a patient's tumor in order to screen for therapies that the patient could benefit from. Samples obtained from 29 primary tumors and liver metastases of uveal melanoma were grafted into SCID mice. PDX models were successfully established for 35% of primary patient tumors and 67% of liver metastases. The tumor take rate was proportional to the risk of metastases. PDXs showed the same morphology, the same GNAQ/11, BAP1, and SF3B1 mutations, and the same chromosome 3 and 8q status as the corresponding patient samples. Six PDX models were challenged with two compounds for 4 weeks. We show that, for 31% of patients with high or intermediate risk of metastasis, the timing to obtain efficacy results on PDX models derived from their primary tumors was compatible with the selection of the therapy to treat the patient after relapse. PDXs could thus be a valid tool ("avatar") to select the best personalized therapy for one third of patients that are most at risk of relapse.

Molecular profiling of patient-derived breast cancer xenografts.

INTRODUCTION: Identification of new therapeutic agents for breast cancer (BC) requires preclinical models that reproduce the molecular characteristics of their respective clinical tumors. In this work, we analyzed the genomic and gene expression profiles of human BC xenografts and the corresponding patient tumors. METHODS: Eighteen BC xenografts were obtained by grafting tumor fragments from patients into Swiss nude mice. Molecular characterization of patient tumors and xenografts was performed by DNA copy number analysis and gene expression analysis using Affymetrix Microarrays. RESULTS: Comparison analysis showed that 14/18 pairs of tumors shared more than 56% of copy number alterations (CNA). Unsupervised hierarchical clustering analysis showed that 16/18 pairs segregated together, confirming the similarity between tumor pairs. Analysis of recurrent CNA changes between patient tumors and xenografts showed losses in 176 chromosomal regions and gains in 202 chromosomal regions. Gene expression profile analysis showed that less than 5% of genes had recurrent variations between patient tumors and their respective xenografts; these genes largely corresponded to human stromal compartment genes. Finally, analysis of different passages of the same tumor showed that sequential mouse-to-mouse tumor grafts did not affect genomic rearrangements or gene expression profiles, suggesting genetic stability of these models over time. CONCLUSIONS: This panel of human BC xenografts maintains the overall genomic and gene expression profile of the corresponding patient tumors and remains stable throughout sequential in vivo generations. The observed genomic profile and gene expression differences appear to be due to the loss of human stromal genes. These xenografts, therefore, represent a validated model for preclinical investigation of new therapeutic agents.

[Home treatment of low-risk pulmonary embolism patients : Efficacy and safety of an outpatient program including the general practitioner]. / Prise en charge ambulatoire des embolies pulmonaires à risque faible ; expérience d'une filière centrée sur le lien ville-hôpital.

AIM: Outpatient treatment (OT) of patients with low-risk pulmonary embolisms (PE) is recommended. A multidisciplinary OT program including the general practitioner (GP) has been implemented at Versailles hospital in 2019. The objectives of the study were to assess the feasibility, safety and acceptability of the program. MATERIAL AND METHODS: The feasibility of, and the inclusion criteria for OT were defined from a retrospective cohort study of PE patients carried out in 2018. In the prospective study, consecutive patients consulting in the emergency department between 2019 and 2021 with confirmed PE were eligible for OT if they had sPESI and HESTIA scores equal to 0, normal troponin and NT-pro-BNP levels, and no right ventricular dilation on imaging. PEs associated with COVID were excluded. The OT program included 4 appointments within 3 months, including 2 with the GP. Events (death, recurrence of PE or venous thromboembolism, bleeding, rehospitalisation) were collected at 3-month follow-up. RESULTS: In the retrospective study, 19% of the 138 PE patients seen in the emergency department were eligible for OT. No complication occurred at Day 90. In the prospective study, 313 consecutive patients with confirmed PE in the emergency department were included, 66 (21%) were eligible for OT. Overall, 43 patients (14%) received OT (39 eligible) and 27 patients eligible for OT were hospitalised (92% because of pulmonary infarction). At 3-month follow-up, there were no death, no recurrence of thromboembolism, and one patient has been early hospitalised for COVID; 3 female patients treated with rivaroxaban had minor bleeding (heavy menstrual bleeding). The satisfaction rate of general practitioner was 95%. CONCLUSIONS: This study confirms the feasibility and safety of our OT program for low-risk EP patients, centered on the general practitioner. It reduces the time spent in the emergency department, reduces hospitalisations and strengthens the city-hospital link for care.

Netrin-4 inhibits angiogenesis via binding to neogenin and recruitment of Unc5B.

Netrins are secreted molecules with roles in axon guidance and angiogenesis. We identified Netrin-4 as a gene specifically overexpressed in VEGF-stimulated endothelial cells (EC) in vitro as well as in vivo. Knockdown of Netrin-4 expression in EC increased their ability to form tubular structures on Matrigel. To identify which receptor is involved, we showed by quantitative RT-PCR that EC express three of the six Netrin-1 cognate receptors: neogenin, Unc5B, and Unc5C. In contrast to Netrin-1, Netrin-4 bound only to neogenin but not to Unc5B or Unc5C receptors. Neutralization of Netrin-4 binding to neogenin by blocking antibodies abolished the chemotactic effect of Netrin-4. Furthermore, the silencing of either neogenin or Unc5B abolished Netrin-4 inhibitory effect on EC migration, suggesting that both receptors are essential for its function in vitro. Coimmunoprecipitation experiments demonstrated that Netrin-4 increased the association between Unc5B and neogenin on VEGF- or FGF-2-stimulated EC. Finally, we showed that Netrin-4 significantly reduced pathological angiogenesis in Matrigel and laser-induced choroidal neovascularization models. Interestingly, Netrin-4, neogenin, and Unc5B receptor expression was up-regulated in choroidal neovessel EC after laser injury. Moreover, Netrin-4 overexpression delayed tumor angiogenesis in a model of s.c. xenograft. We propose that Netrin-4 acts as an antiangiogenic factor through binding to neogenin and recruitment of Unc5B.

In vitro bone metastasis dwelling in a 3D bioengineered niche.

Bone is the most frequent metastasis site for breast cancer. As well as dramatically increasing disease burden, bone metastases are also an indicator of poor prognosis. One of the main challenges in investigating bone metastasis in breast cancer is engineering in vitro models that replicate the features of in vivo bone environments. Such in vitro models ideally enable the biology of the metastatic cells to mimic their in vivo behavior as closely as possible. Here, taking benefit of cutting-edge technologies both in microfabrication and cancer cell biology, we have developed an in vitro breast cancer bone-metastasis model. To do so we first 3D printed a bone scaffold that reproduces the trabecular architecture and that can be conditioned with osteoblast-like cells, a collagen matrix, and mineralized calcium. We thus demonstrated that this device offers an adequate soil to seed primary breast cancer bone metastatic cells. In particular, patient-derived xenografts being considered as a better approach than cell lines to achieve clinically relevant results, we demonstrate the ability of this biomimetic bone niche model to host patient-derived xenografted metastatic breast cancer cells. These patient-derived xenograft cells show a long-term survival in the bone model and maintain their cycling propensity, and exhibit the same modulated drug response as in vivo. This experimental system enables access to the idiosyncratic features of the bone microenvironment and cancer bone metastasis, which has implications for drug testing.

A preclinical therapeutic schedule optimizing docetaxel plus estramustine administration in prostate cancer.

Androgen-dependent and castration-resistant prostate cancer (PC) is usually sensitive to docetaxel chemotherapy. Nevertheless, docetaxel resistance frequently appears after several cycles of treatment, raising the problem of salvage treatment for docetaxel-resistant PC patients. Although the combination of docetaxel and estramustine prolongs metastasis-free and overall survival of patients with androgen-independent PC, the use of this modality remains limited in elderly patients or patients with several comorbidities, especially vascular disease or gastrointestinal toxicity, because of unacceptable toxicity including venous thrombosis. The aims of this study were therefore (i) to evaluate the in-vivo efficacy of estramustine combined with docetaxel since initial tumor growth and following the appearance of docetaxel resistance in the androgen-dependent human PC xenograft PAC120, and (ii) to evaluate the efficacy of estramustine in six human androgen-independent PC models derived from PAC120. In docetaxel-resistant tumor-bearing mice, estramustine alone induced a TGD2 of 18 days, whereas the combination of docetaxel and estramustine induced a TGD2 of 50 days (P<0.05) with no significantly different overall survival of mice treated by docetaxel and estramustine since day 1 or since the onset of resistance to docetaxel. Among the six human androgen-independent tumors treated with estramustine alone, two highly sensitive models, two intermediate responding tumors, and two resistant models were observed. Altogether, these results suggest that estramustine should be combined with docetaxel in PC patients, but the use of this treatment could be limited, particularly in elderly patients, to docetaxel-resistant cases.

Clinical relevance of human cancer xenografts as a tool for preclinical assessment: example of in-vivo evaluation of topotecan-based chemotherapy in a panel of human small-cell lung cancer xenografts.

Prediction of human tumor response based on preclinical data could reduce the failure rates of subsequent new anticancer drugs clinical development. Human small-cell lung carcinomas (SCLC) are characterized by high initial sensitivity to chemotherapy but a low median survival time because of drug resistance. The aim of this study was to evaluate the therapeutic relevance of a panel of human SCLC xenografts established in our laboratory using one compromising drug in SCLC, topotecan (TPT). Six SCLC xenografts derived from six patients were used: three were sensitive to a combination of etoposide (VP16), cisplatin (CDDP), and ifosfamide (IFO), and three were resistant, as published earlier. Growth inhibition was greater than 84% for five xenografts at doses of 1-2 mg/kg/day. TPT was combined with IFO, etoposide (VP16), and CDDP. IFO improved the efficacy of TPT in three of the five xenografts and complete responses were obtained even with the less TPT-sensitive xenograft. VP16 increased the efficacy of two of four xenografts and complete responses were obtained. The combination of TPT and CDDP did not improve TPT responses for any of the xenografts tested. Semiquantitative reverse transcriptase-PCR of genes involved in drug response, such as topoisomerase I, topoisomerase IIalpha, multidrug resistance 1 (MDR1), multidrug resistance-associated protein (MRP), lung resistance-related protein (LRP), and glutathione S-transferase pi (GSTpi), did not explain the variability in drug sensitivity between SCLC xenografts. In conclusion, these preclinical data mirror those from published clinical studies suggesting that our panel of SCLC xenografts represents a useful tool for preclinical assessment of new treatments.

Establishment of human colon cancer cell lines from fresh tumors versus xenografts: comparison of success rate and cell line features.

Obtaining representative human colon cancer cell lines from fresh tumors is technically difficult. Using 32 tumor fragments from patients with colon cancer, the present study shows that prior xenograft leads to more efficient cell line establishment compared with direct establishment from fresh tumors (P < 0.05). From 26 tumor specimens, we successfully established 20 tumor xenografts in nude mice (77%); among 19 of these xenografts, 9 (47%) led to cell lines, including four from liver metastases. Only 3 of 31 tumor specimens (9.7%) grew immediately in vitro, and all were derived from primary tumors. To compare major phenotypic and genotypic characteristics of human colon cancer cell lines derived from the same tumor fragment using two protocols, the two pairs of cell lines obtained from 2 of 32 tumor fragments were extensively studied. They displayed similar morphology and were able to form compact spheroids. Chemosensitivity to 5-fluorouracil, CPT11, and L-OHP differed between cell lines obtained from patient tumors and those derived from xenografts. Matched cell lines shared a common core of karyotype alterations and distinctive additional chromosomal aberrations. Expression levels of genes selected for their role in oncogenesis evaluated by real-time quantitative PCR were found to be statistically correlated whatever the in vitro culture model used. In conclusion, xenotransplantation in mice of tumor fragments before establishment of cell lines enables generation of more novel human cancer cell lines for investigation of colon cancer cell biology, opening up the opportunity of reproducing the diversity of this disease.

A new model of patient tumor-derived breast cancer xenografts for preclinical assays.

PURPOSE: To establish a panel of human breast cancer (HBC) xenografts in immunodeficient mice suitable for pharmacologic preclinical assays. EXPERIMENTAL DESIGN: 200 samples of HBCs were grafted into Swiss nude mice. Twenty-five transplantable xenografts were established (12.5%). Their characterization included histology, p53 status, genetic analysis by array comparative genomic hybridization, gene expression by Western blotting, and quantitative reverse transcription-PCR. Biological profiles of nine xenografts were compared with those of the corresponding patient's tumor. Chemosensitivities of 17 xenografts to a combination of Adriamycin and cyclophosphamide (AC), docetaxel, trastuzumab, and Degarelix were evaluated. RESULTS: Almost all patient tumors established as xenografts displayed an aggressive phenotype, i.e., high-grade, triple-negative status. The histology of the xenografts recapitulated the features of the original tumors. Mutation of p53 and inactivation of Rb and PTEN proteins were found in 83%, 30%, and 42% of HBC xenografts, respectively. Two HBCx had an ERBB2 (HER2) amplification. Large variations were observed in the expression of HER family receptors and in genomic profiles. Genomic alterations were close to those of original samples in paired tumors. Three xenografts formed lung metastases. A total of 15 of the 17 HBCx (88%) responded to AC, and 8 (47%) responded to docetaxel. One ERBB2-amplified xenograft responded to trastuzumab, whereas the other did not. The drug response of HBC xenografts was concordant with that of the patient's tumor in five of seven analyzable cases. CONCLUSIONS: This panel of breast cancer xenografts includes 15 triple-negative, one ER positive and 2 ERBB2 positive. This panel represents a useful preclinical tool for testing new agents and protocols and for further exploration of the biological basis of drug responses.

PKD1 is a potential biomarker and therapeutic target in triple-negative breast cancer.

Protein Kinase D1 (PKD1) is a serine/threonine kinase encoded by the PRKD1 gene. PKD1 has been previously shown to be a prognostic factor in ERα+ tamoxifen-resistant breast tumors and PKD1 overexpression confers estrogen independence to ERα+ MCF7 cells. In the present study, our goal was to determine whether PKD1 is a prognostic factor and/or a relevant therapeutic target in breast cancer. We analyzed PRKD1 mRNA levels in 527 primary breast tumors. We found that high PRKD1 mRNA levels were significantly and independently associated with a low metastasis-free survival in the whole breast cancer population and in the triple-negative breast cancer (TNBC) subtype specifically. High PRKD1 mRNA levels were also associated with a low overall survival in TNBC. We identified novel PKD1 inhibitors and assessed their antitumor activity in vitro in TNBC cell lines and in vivo in a TNBC patient-derived xenograft (PDX) model. Pharmacological inhibition and siRNA-mediated depletion of PKD1 reduced colony formation in MDA-MB-436 TNBC cells. PKD1 inhibition also reduced tumor growth in vivo in a TNBC PDX model. Together, these results establish PKD1 as a poor prognostic factor and a potential therapeutic target in TNBC.

Inhibition of mTOR downregulates expression of DNA repair proteins and is highly efficient against BRCA2-mutated breast cancer in combination to PARP inhibition.

Breast cancer is a complex disease in which each patient could present several genetic alterations that are therapeutically relevant in cancers. Here we explored the therapeutic benefit of combining PARP and mTOR inhibitors in a context of DNA repair deficiency and PI3K pathway activation. The combination of everolimus and olaparib was tested in BRCA2-mutated patient-derived xenografts (PDX) carrying alterations in the PI3K/AKT/mTOR pathway. An RPPA analysis of different signalling pathways was performed in untreated and treated xenografts. Everolimus and olaparib showed marked anti-tumor activities in the monotherapy setting and high efficacy when given in combination with 100% of mice showing tumor regressions. The fraction of P-H2AX positive cells was increased in both monotherapy arms and strongly increased in the combination setting. Everolimus given as monotherapy resulted in downregulation of different proteins involved in DNA damage repair, including FANCD2, RAD50 and SUV39H1. In the combination setting, expression of these proteins was almost completely abolished, suggesting convergence of PARP and mTOR in downregulation of DNA damage repair components. In conclusion, our results suggest that combining mTOR and DNA repair inhibition could be a successful strategy to treat a subset of breast cancer with BRCA2 mutation and alterations in the PI3K/AKT/mTOR pathway.

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.

Combination of Carboplatin and Bevacizumab Is an Efficient Therapeutic Approach in Retinoblastoma Patient-Derived Xenografts.

PURPOSE: Retinoblastoma (Rb) is a rare childhood cancer of the retina with a survival rate of 95% in children living in high-income countries, after appropriate therapies such as chemotherapy, local ophthalmologic treatment, and radiotherapy. However, due to inactivation of the RB1 gene, all bilateral and almost 15% of unilateral retinoblastoma patients have a higher risk of s econdary cancers, especially sarcomas. Hence, new nonmutagen treatments are warranted. Therefore, we investigated the efficacy of therapy using anti-VEGF antibody bevacizumab, either alone or with carboplatin, in well-characterized Rb patient-derived xenografts (PDXs). METHODS: Three Rb PDXs previously established and characterized, RB102, RB111, and RB200, have been treated using carboplatin, bevacizumab, or carboplatin + bevacizumab. In order to define antitumor responses, various quantitative PCR and histopathologic analyses have then been performed on tumors collected at the end of experiments. RESULTS: In all treated PDX models, we have observed a high and significant improvement of chemotherapy-induced in vivo efficacy by the antiangiogenic antibody. The overall response rate, lower than -0.5, was 48%, 27%, and 86% after carboplatin, bevacizumab, and carboplatin + bevacizumab, respectively (carboplatin versus carboplatin + bevacizumab; P < 10-2; bevacizumab versus carboplatin + bevacizumab; P < 10-3). In the Rb200 PDX, such a result was also observed when bevacizumab was combined with lower doses of carboplatin. Quantitative PCR and histopathologic analyses have been performed and confirmed the impact of the bevacizumab-based treatments on various angiogenic markers. CONCLUSIONS: Overall, our in vivo results confirm the interest in antiangiogenic therapy for the treatment of Rb in combination with carboplatin and provide a robust rationale for testing this combination in the clinical setting for Rb patients.

Combination of COX-2 expression and PIK3CA mutation as prognostic and predictive markers for celecoxib treatment in breast cancer.

COX-2 expression level and prognostic value are still a matter of debate in breast cancer (BC). We addressed these points in the context of PIK3CA mutational status. Based on an interesting study of aspirin efficacy in colorectal cancer, we hypothesized that celecoxib antitumoral activity may be restricted to PIK3CA mutated BC.COX-2 mRNA expression was analyzed in 446 BC samples and in 61 BC patient-derived xenografts (PDX) using quantitative RT-PCR. The prognostic impact of COX-2 expression level was assessed independently and according to PIK3CA mutational status in our cohort and in a validation set of 817 BC. The antitumoral activity of celecoxib was tested in two triple-negative (TN) PDX with a PIK3CA wild-type (wt) or mutated genotype.COX-2 mRNA was overexpressed in 2% of BC and significantly associated with TN subtype. Metastasis-free survival (MFS) was significantly better in patients with high COX-2 expression level, the prognosis of whom was similar to patients with PIK3CA mutations. TCGA validation cohort confirmed that patients with low COX-2 expression PIK3CA wt tumors had the worse disease-free survival (DFS) compared to all other subgroups. Celecoxib had a significant antitumoral effect in PIK3CA mutated PDX only. Celecoxib antitumoral activity involved S6 ribosomal protein and AKT phosphorylation.Low expression of COX-2 has a significant negative impact on the MFS/DFS of BC patients. Antitumoral effect of celecoxib is restricted to PIK3CA mutated PDX. These results suggest that PIK3CA mutation may be a new predictive biomarker for celecoxib efficacy.

Targeting mTOR pathway inhibits tumor growth in different molecular subtypes of triple-negative breast cancers.

Triple-negative breast cancers (TNBC) are characterized by frequent alterations in the PI3K/AKT/mTOR signaling pathway. In this study, we analyzed PI3K pathway activation in 67 patient-derived xenografts (PDX) of breast cancer and investigated the anti-tumor activity of the mTOR inhibitor everolimus in 15 TNBC PDX with different expression and mutational status of PI3K pathway markers. Expression of the tumor suppressors PTEN and INPP4B was lost in 55% and 76% of TNBC PDX, respectively, while mutations in PIK3CA and AKT1 genes were rare. In 7 PDX treatment with everolimus resulted in a tumor growth inhibition higher than 50%, while 8 models were classified as low responder or resistant. Basal-like, LAR (Luminal AR), mesenchymal and HER2-enriched tumors were present in both responder and resistant groups, suggesting that tumor response to everolimus is not restricted to a specific TNBC subtype. Analysis of treated tumors showed a correlation between tumor response and post-treatment phosphorylation of AKT, increased in responder PDX, while PI3K pathway markers at baseline were not sufficient to predict everolimus response. In conclusion, targeting mTOR decreased tumor growth in 7 out of 15 TNBC PDX tested. Response to everolimus occurred in different TNBC subtypes and was associated with post-treatment increase of P-AKT.