Development of Novel Models of Aggressive Variants of Castration-resistant Prostate Cancer.

BACKGROUND: Genomic studies have identified new subsets of aggressive prostate cancer (PCa) with poor prognosis (eg, neuroendocrine prostate cancer [NEPC], PCa with DNA damage response [DDR] alterations, or PCa resistant to androgen receptor pathway inhibitors [ARPIs]). Development of novel therapies relies on the availability of relevant preclinical models. OBJECTIVE: To develop new preclinical models (patient-derived xenograft [PDX], PDX-derived organoid [PDXO], and patient-derived organoid [PDO]) representative of the most aggressive variants of PCa and to develop a new drug evaluation strategy. DESIGN, SETTING, AND PARTICIPANTS: NEPC (n = 5), DDR (n = 7), and microsatellite instability (MSI)-high (n = 1) PDXs were established from 51 patients with metastatic PCa; PDXOs (n = 16) and PDOs (n = 6) were developed to perform drug screening. Histopathology and treatment response were characterized. Molecular profiling was performed by whole-exome sequencing (WES; n = 13), RNA sequencing (RNA-seq; n = 13), and single-cell RNA-seq (n = 14). WES and RNA-seq data from patient tumors were compared with the models. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Relationships with outcome were analyzed using the multivariable chi-square test and the tumor growth inhibition test. RESULTS AND LIMITATIONS: Our PDXs captured both common and rare molecular phenotypes and their molecular drivers, including alterations of BRCA2, CDK12, MSI-high status, and NEPC. RNA-seq profiling demonstrated broad representation of PCa subtypes. Single-cell RNA-seq indicates that PDXs reproduce cellular and molecular intratumor heterogeneity. WES of matched patient tumors showed preservation of most genetic driver alterations. PDXOs and PDOs preserve drug sensitivity of the matched tissue and can be used to determine drug sensitivity. CONCLUSIONS: Our models reproduce the phenotypic and genomic features of both common and aggressive PCa variants and capture their molecular heterogeneity. Successfully developed aggressive-variant PCa preclinical models provide an important tool for predicting tumor response to anticancer therapy and studying resistance mechanisms. PATIENT SUMMARY: In this report, we looked at the outcomes of preclinical models from patients with metastatic prostate cancer enrolled in the MATCH-R trial (NCT02517892).

Modelling the impact of liver regeneration on hepatoblastoma patient-derived-xenograft tumor growth.

BACKGROUND: Twenty percent of children with hepatoblastoma (HB) have lung metastasis at diagnosis. Treatment protocols recommend surgical removal of chemotherapy-refractory lung nodules, however no chronological order is established. As hepatectomy is followed by release of growth factors, it has been proposed that partial hepatectomy (PH) could boost local or distant residual tumor growth. METHODS: To evaluate the impact of PH on distant tumor growth, PH was performed in mice subcutaneously implanted with a HB patient-derived xenograft (PDX). The influence of PH on tumor growth at primary site was assessed by performing PH concomitantly to HB PDXs orthotopic implantation. RESULTS: Subcutaneously implanted HB PDX failed to show any influence of hepatectomy on tumor growth. Instead, intrahepatic tumor growth of one of the 4 HB PDXs implanted orthotopically was clearly enhanced. Cells derived from the hepatectomy-sensitive HB PDX exposed to hepatic growth factor (HGF) showed increased proliferation rate compared to cells derived from a hepatectomy-insensitive model, suggesting that the HGF/MET pathway could be one of the effectors of the crosstalk between liver regeneration and HB growth. CONCLUSION: These results suggest that hepatectomy can contribute to HB growth in some patients, further studies will be necessary to identify biomarkers predictive of patient risk of PH-induced HB recurrence. IMPACT: Key message: Cytokines and growth factors secreted following partial hepatectomy can contribute to intrahepatic tumor growth in some hepatoblastoma models. What does it add to the existing literature: It is the first article about the impact of liver regeneration induced by partial hepatectomy on hepatoblastoma local or distant tumoral growth in nude mice. What is the impact: It is important to identify the secreted factors that enhance tumor growth and to define biomarkers predictive of patient risk of partial hepatectomy-induced hepatoblastoma recurrence.

Resistance to Selective FGFR Inhibitors in FGFR-Driven Urothelial Cancer.

Several fibroblast growth factor receptor (FGFR) inhibitors are approved or in clinical development for the treatment of FGFR-driven urothelial cancer, and molecular mechanisms of resistance leading to patient relapses have not been fully explored. We identified 21 patients with FGFR-driven urothelial cancer treated with selective FGFR inhibitors and analyzed postprogression tissue and/or circulating tumor DNA (ctDNA). We detected single mutations in the FGFR tyrosine kinase domain in seven (33%) patients (FGFR3 N540K, V553L/M, V555L/M, E587Q; FGFR2 L551F) and multiple mutations in one (5%) case (FGFR3 N540K, V555L, and L608V). Using Ba/F3 cells, we defined their spectrum of resistance/sensitivity to multiple selective FGFR inhibitors. Eleven (52%) patients harbored alterations in the PI3K-mTOR pathway (n = 4 TSC1/2, n = 4 PIK3CA, n = 1 TSC1 and PIK3CA, n = 1 NF2, n = 1 PTEN). In patient-derived models, erdafitinib was synergistic with pictilisib in the presence of PIK3CA E545K, whereas erdafitinib-gefitinib combination was able to overcome bypass resistance mediated by EGFR activation. SIGNIFICANCE: In the largest study on the topic thus far, we detected a high frequency of FGFR kinase domain mutations responsible for resistance to FGFR inhibitors in urothelial cancer. Off-target resistance mechanisms involved primarily the PI3K-mTOR pathway. Our findings provide preclinical evidence sustaining combinatorial treatment strategies to overcome bypass resistance. See related commentary by Tripathi et al., p. 1964. This article is featured in Selected Articles from This Issue, p. 1949.

Targeting genome integrity dysfunctions impedes metastatic potency in non-small cell lung cancer circulating tumor cell-derived explants.

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

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

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

High in vitro and in vivo synergistic activity between mTORC1 and PLK1 inhibition in adenocarcinoma NSCLC.

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

Feasibility and first reports of the MATCH-R repeated biopsy trial at Gustave Roussy.

Unravelling the biological processes driving tumour resistance is necessary to support the development of innovative treatment strategies. We report the design and feasibility of the MATCH-R prospective trial led by Gustave Roussy with the primary objective of characterizing the molecular mechanisms of resistance to cancer treatments. The primary clinical endpoints consist of analyzing the type and frequency of molecular alterations in resistant tumours and compare these to samples prior to treatment. Patients experiencing disease progression after an initial partial response or stable disease for at least 24 weeks underwent a tumour biopsy guided by CT or ultrasound. Molecular profiling of tumours was performed using whole exome sequencing, RNA sequencing and panel sequencing. At data cut-off for feasibility analysis, out of 333 inclusions, tumour biopsies were obtained in 303 cases (91%). From these biopsies, 278 (83%) had sufficient quality for analysis by high-throughput next generation sequencing (NGS). All 278 samples underwent targeted NGS, 215 (70.9%) RNA sequencing and 222 (73.2%) whole exome sequencing. In total, 163 tumours were implanted in NOD scid gamma (NSG) or nude mice and 54 patient-derived xenograft (PDX) models were established, with a success rate of 33%. Adverse events secondary to invasive tumour sampling occurred in 24 patients (7.6%). Study recruitment is still ongoing. Systematic molecular profiling of tumours and the development of patient-derived models of acquired resistance to targeted agents and immunotherapy is feasible and can drive the selection of the next therapeutic strategy.

Genetic characterization of a unique neuroendocrine transdifferentiation prostate circulating tumor cell-derived eXplant model.

Transformation of castration-resistant prostate cancer (CRPC) into an aggressive neuroendocrine disease (CRPC-NE) represents a major clinical challenge and experimental models are lacking. A CTC-derived eXplant (CDX) and a CDX-derived cell line are established using circulating tumor cells (CTCs) obtained by diagnostic leukapheresis from a CRPC patient resistant to enzalutamide. The CDX and the derived-cell line conserve 16% of primary tumor (PT) and 56% of CTC mutations, as well as 83% of PT copy-number aberrations including clonal TMPRSS2-ERG fusion and NKX3.1 loss. Both harbor an androgen receptor-null neuroendocrine phenotype, TP53, PTEN and RB1 loss. While PTEN and RB1 loss are acquired in CTCs, evolutionary analysis suggest that a PT subclone harboring TP53 loss is the driver of the metastatic event leading to the CDX. This CDX model provides insights on the sequential acquisition of key drivers of neuroendocrine transdifferentiation and offers a unique tool for effective drug screening in CRPC-NE management.

Diverse Resistance Mechanisms to the Third-Generation ALK Inhibitor Lorlatinib in ALK-Rearranged Lung Cancer.

PURPOSE: Lorlatinib is a third-generation anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitor with proven efficacy in patients with ALK-rearranged lung cancer previously treated with first- and second-generation ALK inhibitors. Beside compound mutations in the ALK kinase domain, other resistance mechanisms driving lorlatinib resistance remain unknown. We aimed to characterize the mechanisms of resistance to lorlatinib occurring in patients with ALK-rearranged lung cancer and design new therapeutic strategies in this setting. EXPERIMENTAL DESIGN: Resistance mechanisms were investigated in 5 patients resistant to lorlatinib. Longitudinal tumor biopsies were studied using high-throughput next-generation sequencing. Patient-derived models were developed to characterize the acquired resistance mechanisms, and Ba/F3 cell mutants were generated to study the effect of novel ALK compound mutations. Drug combinatory strategies were evaluated in vitro and in vivo to overcome lorlatinib resistance. RESULTS: Diverse biological mechanisms leading to lorlatinib resistance were identified. Epithelial-mesenchymal transition (EMT) mediated resistance in two patient-derived cell lines and was susceptible to dual SRC and ALK inhibition. We characterized three ALK kinase domain compound mutations occurring in patients, L1196M/D1203N, F1174L/G1202R, and C1156Y/G1269A, with differential susceptibility to ALK inhibition by lorlatinib. We identified a novel bypass mechanism of resistance caused by NF2 loss-of-function mutations, conferring sensitivity to treatment with mTOR inhibitors. CONCLUSIONS: This study shows that mechanisms of resistance to lorlatinib are diverse and complex, requiring new therapeutic strategies to tailor treatment upon disease progression.

N6-methyladenosine modification of circNSUN2 facilitates cytoplasmic export and stabilizes HMGA2 to promote colorectal liver metastasis.

Circular RNAs (circRNAs) have been implicated in cancer progression through largely unknown mechanisms. Herein, we identify an N6-methyladenosine (m6A) modified circRNA, circNSUN2, frequently upregulated in tumor tissues and serum samples from colorectal carcinoma (CRC) patients with liver metastasis (LM) and predicts poorer patient survival. The upregulated expression of circNSUN2 promotes LM in PDX metastasis models in vivo and accelerates cancer cells invasion in vitro. Importantly, N6-methyladenosine modification of circNSUN2 increases export to the cytoplasm. By forming a circNSUN2/IGF2BP2/HMGA2 RNA-protein ternary complex in the cytoplasm, circNSUN2 enhances the stability of HMGA2 mRNA to promote CRC metastasis progression. Clinically, the upregulated expressions of circNSUN2 and HMGA2 are more prevalent in LM tissues than in primary CRC tissues. These findings elucidate that N6-methyladenosine modification of circNSUN2 modulates cytoplasmic export and stabilizes HMGA2 to promote CRC LM, and suggest that circNSUN2 could represent a critical prognostic marker and/or therapeutic target for the disease.

Correction: Intracellular STING inactivation sensitizes breast cancer cells to genotoxic agents.

[This corrects the article DOI: 10.18632/oncotarget.12858.].

A RAD51 assay feasible in routine tumor samples calls PARP inhibitor response beyond BRCA mutation.

Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) are effective in cancers with defective homologous recombination DNA repair (HRR), including BRCA1/2-related cancers. A test to identify additional HRR-deficient tumors will help to extend their use in new indications. We evaluated the activity of the PARPi olaparib in patient-derived tumor xenografts (PDXs) from breast cancer (BC) patients and investigated mechanisms of sensitivity through exome sequencing, BRCA1 promoter methylation analysis, and immunostaining of HRR proteins, including RAD51 nuclear foci. In an independent BC PDX panel, the predictive capacity of the RAD51 score and the homologous recombination deficiency (HRD) score were compared. To examine the clinical feasibility of the RAD51 assay, we scored archival breast tumor samples, including PALB2-related hereditary cancers. The RAD51 score was highly discriminative of PARPi sensitivity versus PARPi resistance in BC PDXs and outperformed the genomic test. In clinical samples, all PALB2-related tumors were classified as HRR-deficient by the RAD51 score. The functional biomarker RAD51 enables the identification of PARPi-sensitive BC and broadens the population who may benefit from this therapy beyond BRCA1/2-related cancers.

MiR-205 as predictive biomarker and adjuvant therapeutic tool in combination with trastuzumab.

Trastuzumab is the standard treatment for HER2+ breast cancer (BC) patients, and even though it significantly improved their clinical outcome, 50% of them do not benefit from this drug and disease recurs, underlining the need of reliable predictive biomarkers and new therapeutic strategies. Strikingly, despite all the molecular analyses performed to identify the escape mechanisms behind this resistance, it still represents a question point. MiRNAs have been correlated with occurrence and progression of human cancer, and their potential as clinical tools has emerged in the last years. We previously reported that oncosuppressive miR-205 targets HER3, thus increasing the responsiveness to TKIs lapatinib and gefitinib in preclinical models. Here we demonstrate that HER3 inhibition by miR-205 ectopic expression or siRNA-mediated silencing improves the responsiveness to Trastuzumab in vitro in HER2+ BC cell lines, and that this effect is exerted through impairment of AKT-mediated pathway. Moreover, evaluating a series of 52 HER2+ BC patients treated with adjuvant Trastuzumab, we observed that higher miR-205 expression is significantly associated with better outcome (disease-free survival). In summary, our data indicate that miR-205 could predict Trastuzumab efficacy and that its modulation might be useful as adjuvant treatment to improve the response to the drug.

An NF90/NF110-mediated feedback amplification loop regulates dicer expression and controls ovarian carcinoma progression.

Reduced expression of DICER, a key enzyme in the miRNA pathway, is frequently associated with aggressive, invasive disease, and poor survival in various malignancies. Regulation of DICER expression is, however, poorly understood. Here, we show that NF90/NF110 facilitates DICER expression by controlling the processing of a miRNA, miR-3173, which is embedded in DICER pre-mRNA. As miR-3173 in turn targets NF90, a feedback amplification loop controlling DICER expression is established. In a nude mouse model, NF90 overexpression reduced proliferation of ovarian cancer cells and significantly reduced tumor size and metastasis, whereas overexpression of miR-3173 dramatically increased metastasis in an NF90- and DICER-dependent manner. Clinically, low NF90 expression and high miR-3173-3p expression were found to be independent prognostic markers of poor survival in a cohort of ovarian carcinoma patients. These findings suggest that, by facilitating DICER expression, NF90 can act as a suppressor of ovarian carcinoma.

Association of FGFR1 with ERα Maintains Ligand-Independent ER Transcription and Mediates Resistance to Estrogen Deprivation in ER+ Breast Cancer.

Purpose:FGFR1 amplification occurs in approximately 15% of estrogen receptor-positive (ER+) human breast cancers. We investigated mechanisms by which FGFR1 amplification confers antiestrogen resistance to ER+ breast cancer.Experimental Design: ER+ tumors from patients treated with letrozole before surgery were subjected to Ki67 IHC, FGFR1 FISH, and RNA sequencing (RNA-seq). ER+/FGFR1-amplified breast cancer cells, and patient-derived xenografts (PDX) were treated with FGFR1 siRNA or the FGFR tyrosine kinase inhibitor lucitanib. Endpoints were cell/xenograft growth, FGFR1/ERα association by coimmunoprecipitation and proximity ligation, ER genomic activity by ChIP sequencing, and gene expression by RT-PCR.Results: ER+/FGFR1-amplified tumors in patients treated with letrozole maintained cell proliferation (Ki67). Estrogen deprivation increased total and nuclear FGFR1 and FGF ligands expression in ER+/FGFR1-amplified primary tumors and breast cancer cells. In estrogen-free conditions, FGFR1 associated with ERα in tumor cell nuclei and regulated the transcription of ER-dependent genes. This association was inhibited by a kinase-dead FGFR1 mutant and by treatment with lucitanib. ChIP-seq analysis of estrogen-deprived ER+/FGFR1-amplified cells showed binding of FGFR1 and ERα to DNA. Treatment with fulvestrant and/or lucitanib reduced FGFR1 and ERα binding to DNA. RNA-seq data from FGFR1-amplified patients' tumors treated with letrozole showed enrichment of estrogen response and E2F target genes. Finally, growth of ER+/FGFR1-amplified cells and PDXs was more potently inhibited by fulvestrant and lucitanib combined than each drug alone.Conclusions: These data suggest the ERα pathway remains active in estrogen-deprived ER+/FGFR1-amplified breast cancers. Therefore, these tumors are endocrine resistant and should be candidates for treatment with combinations of ER and FGFR antagonists. Clin Cancer Res; 23(20); 6138-50. ©2017 AACR.

Intracellular STING inactivation sensitizes breast cancer cells to genotoxic agents.

Activation of the IFN/STAT1 pathway is closely associated with drug response and recurrence of breast cancer treated by chemotherapy. The aim of the current study was to elucidate the molecular mechanisms involved upstream and downstream of this pathway in order to identify distinct entities that might be manipulated to improve treatment efficacy. Four breast cancer cell lines (T-47D, MCF7, MDA-MB-231 and HBCx-19 established from the eponymous PDX) were treated in vitro with mafosfamide, a DNA damage inducer. In two of these cell lines (MCF7 and HBCx-19), genotoxic treatment upregulated type I IFN expression leading to paracrine activation of IFN/STAT1 signaling pathway after 6-8 days. We show that STING, a well-characterized inducer of IFN in immune cells, is rapidly triggered in MCF7 cells under genotoxic stress and forms nuclear foci that co-localize with phosphorylated IRF-3 and γH2AX. STING silencing abrogated chemotherapy-induced type I IFN production and signaling and potentiated genotoxic treatment efficacy as it promoted cell death extent and delayed cell colony regrowth. Similar results were obtained after silencing PARP12, one selected gene of the IFN/STAT1 pathway fingerprint. In summary, this study provides the first demonstration of STING activation in breast cancer cells. Our data suggest that genotoxic-induced, STING-mediated type I IFN signaling is a cell-intrinsic mechanism of breast cancer cell survival and regrowth.

Patient-derived mouse xenografts from pediatric liver cancer predict tumor recurrence and advise clinical management.

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

Activation of IFN/STAT1 signalling predicts response to chemotherapy in oestrogen receptor-negative breast cancer.

BACKGROUND: Oestrogen receptor-negative (ER-) breast cancer is intrinsically sensitive to chemotherapy. However, tumour response is often incomplete, and relapse occurs with high frequency. The aim of this work was to analyse the molecular characteristics of residual tumours and early response to chemotherapy in patient-derived xenografts (PDXs) of breast cancer. METHODS: Gene and protein expression profiles were analysed in a panel of ER- breast cancer PDXs before and after chemotherapy treatment. Tumour and stromal interferon-gamma expression was measured in xenografts lysates by human and mouse cytokine arrays, respectively. RESULTS: The analysis of residual tumour cells in chemo-responder PDX revealed a strong overexpression of IFN-inducible genes, induced early after AC treatment and associated with increased STAT1 phosphorylation, DNA-damage and apoptosis. No increase in IFN-inducible gene expression was observed in chemo-resistant PDXs upon chemotherapy. Overexpression of IFN-related genes was associated with human IFN-γ secretion by tumour cells. CONCLUSIONS: Treatment-induced activation of the IFN/STAT1 pathway in tumour cells is associated with chemotherapy response in ER- breast cancer. Further validations in prospective clinical trials will aim to evaluate the usefulness of this signature to assist therapeutic strategies in the clinical setting.

Murine model of hepatic breast cancer.

BACKGROUND AND AIMS: Breast cancer is the most common cancer in women and the second leading cause of cancer-related deaths in this population. Breast cancer related deaths have declined due to screening and adjuvant therapies, yet a driving clinical need exists to better understand the cause of the deadliest aspect of breast cancer, metastatic disease. Breast cancer metastasizes to several distant organs, the liver being the third most common site. To date, very few murine models of hepatic breast cancer exist. METHODS: In this study, a novel murine model of liver breast cancer using the MDA-MB-231 cell line is introduced as an experimental (preclinical) model. RESULTS: Histological typing revealed consistent hepatic breast cancer tumor foci. Common features of the murine model were vascular invasion, lung metastasis and peritoneal seeding. CONCLUSIONS: The novel murine model of hepatic breast cancer established in this study provides a tool to be used to investigate mechanisms of hepatic metastasis and to test potential therapeutic interventions.