Engagement of CD99 Activates Distinct Programs in Ewing Sarcoma and Macrophages

Ewing sarcoma (EWS) is the second most common pediatric bone tumor. The EWS tumor microenvironment is largely recognized as immune-cold, with macrophages being the most abundant immune cells and their presence associated with worse patient prognosis. Expression of CD99 is a hallmark of EWS cells, and its targeting induces inhibition of EWS tumor growth through a poorly understood mechanism. In this study, we analyzed CD99 expression and functions on macrophages and investigated whether the concomitant targeting of CD99 on both tumor and macrophages could explain the inhibitory effect of this approach against EWS. Targeting CD99 on EWS cells downregulated expression of the "don't eat-me" CD47 molecule but increased levels of the "eat-me" phosphatidyl serine and calreticulin molecules on the outer leaflet of the tumor cell membrane, triggering phagocytosis and digestion of EWS cells by macrophages. In addition, CD99 ligation induced reprogramming of undifferentiated M0 macrophages and M2-like macrophages toward the inflammatory M1-like phenotype. These events resulted in the inhibition of EWS tumor growth. Thus, this study reveals what we believe to be a previously unrecognized function of CD99, which engenders a virtuous circle that delivers intrinsic cell death signals to EWS cells, favors tumor cell phagocytosis by macrophages, and promotes the expression of various molecules and cytokines, which are pro-inflammatory and usually associated with tumor regression. This raises the possibility that CD99 may be involved in boosting the antitumor activity of macrophages.

CD99 Modulates the Proteomic Landscape of Ewing Sarcoma Cells and Related Extracellular Vesicles

Ewing sarcoma (EWS) is an aggressive pediatric bone tumor characterized by unmet clinical needs and an incompletely understood epigenetic heterogeneity. Here, we considered CD99, a major surface molecule hallmark of EWS malignancy. Fluctuations in CD99 expression strongly impair cell dissemination, differentiation, and death. CD99 is also loaded within extracellular vesicles (EVs), and the delivery of CD99-positive or CD99-negative EVs dynamically exerts oncogenic or oncosuppressive functions to recipient cells, respectively. We undertook mass spectrometry and functional annotation analysis to investigate the consequences of CD99 silencing on the proteomic landscape of EWS cells and related EVs. Our data demonstrate that (i) the decrease in CD99 leads to major changes in the proteomic profile of EWS cells and EVs; (ii) intracellular and extracellular compartments display two distinct signatures of differentially expressed proteins; (iii) proteomic changes converge to the modulation of cell migration and immune-modulation biological processes; and (iv) CD99-silenced cells and related EVs are characterized by a migration-suppressive, pro-immunostimulatory proteomic profile. Overall, our data provide a novel source of CD99-associated protein biomarkers to be considered for further validation as mediators of EWS malignancy and as EWS disease liquid biopsy markers.

ABCA6 affects the malignancy of Ewing sarcoma cells via cholesterol-guided inhibition of the IGF1R/AKT/MDM2 axis

PURPOSE

The relevance of the subfamily A members of ATP-binding cassette (ABCA) transporters as biomarkers of risk and response is emerging in different tumors, but their mechanisms of action have only been partially defined. In this work, we investigated their role in Ewing sarcoma (EWS), a pediatric cancer with unmet clinical issues.

METHODS

The expression of ABC members was evaluated by RT-qPCR in patients with localized EWS. The correlation with clinical outcome was established in different datasets using univariate and multivariate statistical methods. Functional studies were conducted in cell lines from patient-derived xenografts (PDXs) using gain- or loss-of-function approaches. The impact of intracellular cholesterol levels and cholesterol lowering drugs on malignant parameters was considered.

RESULTS

We found that ABCA6, which is usually poorly expressed in EWS, when upregulated became a prognostic factor of a favorable outcome in patients. Mechanistically, high expression of ABCA6 impaired cell migration and increased cell chemosensitivity by diminishing the intracellular levels of cholesterol and by constitutive IGF1R/AKT/mTOR expression/activation. Accordingly, while exposure of cells to exogenous cholesterol increased AKT/mTOR activation, the cholesterol lowering drug simvastatin inhibited IGF1R/AKT/mTOR signaling and prevented Ser166 phosphorylation of MDM2. This, in turn, favored p53 activation and enhanced pro-apoptotic effects of doxorubicin.

CONCLUSIONS

Our study reveals that ABCA6 acts as tumor suppressor in EWS cells via cholesterol-mediated inhibition of IGF1R/AKT/MDM2 signaling, which promotes the pro-apoptotic effects of doxorubicin and reduces cell migration. Our findings also support a role of ABCA6 as biomarker of EWS progression and sustains its assessment for a more rational use of statins as adjuvant drugs.

A 3D Collagen-Based Bioprinted Model to Study Osteosarcoma Invasiveness and Drug Response

The biological and therapeutic limits of traditional 2D culture models, which only partially mimic the complexity of cancer, have recently emerged. In this study, we used a 3D bioprinting platform to process a collagen-based hydrogel with embedded osteosarcoma (OS) cells. The human OS U-2 OS cell line and its resistant variant (U-2OS/CDDP 1 μg) were considered. The fabrication parameters were optimized to obtain 3D printed constructs with overall morphology and internal microarchitecture that accurately match the theoretical design, in a reproducible and stable process. The biocompatibility of the 3D bioprinting process and the chosen collagen bioink in supporting OS cell viability and metabolism was confirmed through multiple assays at short- (day 3) and long- (day 10) term follow-ups. In addition, we tested how the 3D collagen-based bioink affects the tumor cell invasive capabilities and chemosensitivity to cisplatin (CDDP). Overall, we developed a new 3D culture model of OS cells that is easy to set up, allows reproducible results, and better mirrors malignant features of OS than flat conditions, thus representing a promising tool for drug screening and OS cell biology research.

Novel Targeting of DNA Methyltransferase Activity Inhibits Ewing Sarcoma Cell Proliferation and Enhances Tumor Cell Sensitivity to DNA Damaging Drugs by Activating the DNA Damage Response

DNA methylation is an important component of the epigenetic machinery that regulates the malignancy of Ewing sarcoma (EWS), the second most common primary bone tumor in children and adolescents. Coordination of DNA methylation and DNA replication is critical for maintaining epigenetic programming and the DNMT1 enzyme has been demonstrated to have an important role in both maintaining the epigenome and controlling cell cycle. Here, we showed that the novel nonnucleoside DNMT inhibitor (DNMTi) MC3343 induces a specific depletion of DNMT1 and affects EWS tumor proliferation through a mechanism that is independent on DNA methylation. Depletion of DNMT1 causes perturbation of the cell cycle, with an accumulation of cells in the G1 phase, and DNA damage, as revealed by the induction of γH2AX foci. These effects elicited activation of p53-dependent signaling and apoptosis in p53wt cells, while in p53 mutated cells, persistent micronuclei and increased DNA instability was observed. Treatment with MC3343 potentiates the efficacy of DNA damaging agents such as doxorubicin and PARP-inhibitors (PARPi). This effect correlates with increased DNA damage and synergistic tumor cytotoxicity, supporting the use of the DNMTi MC3343 as an adjuvant agent in treating EWS.

Therapeutic vulnerability to PARP1,2 inhibition in RB1-mutant osteosarcoma

Loss-of-function mutations in the RB1 tumour suppressor are key drivers in cancer, including osteosarcoma. RB1 loss-of-function compromises genome-maintenance and hence could yield vulnerability to therapeutics targeting such processes. Here we demonstrate selective hypersensitivity to clinically-approved inhibitors of Poly-ADP-Polymerase1,2 inhibitors (PARPi) in RB1-defective cancer cells, including an extended panel of osteosarcoma-derived lines. PARPi treatment results in extensive cell death in RB1-defective backgrounds and prolongs survival of mice carrying human RB1-defective osteosarcoma grafts. PARPi sensitivity is not associated with canonical homologous recombination defect (HRd) signatures that predict PARPi sensitivity in cancers with BRCA1,2 loss, but is accompanied by rapid activation of DNA replication checkpoint signalling, and active DNA replication is a prerequisite for sensitivity. Importantly, sensitivity in backgrounds with natural or engineered RB1 loss surpasses that seen in BRCA-mutated backgrounds where PARPi have established clinical benefit. Our work provides evidence that PARPi sensitivity extends beyond cancers identifiable by HRd and advocates PARP1,2 inhibition as a personalised strategy for RB1-mutated osteosarcoma and other cancers.

ROCK2 deprivation leads to the inhibition of tumor growth and metastatic potential in osteosarcoma cells through the modulation of YAP activity

Background

The treatment of metastatic osteosarcoma (OS) remains a challenge for oncologists, and novel therapeutic strategies are urgently needed. An understanding of the pathways that regulate OS dissemination is required for the design of novel treatment approaches. We recently identified Rho-associated coiled-coil containing protein kinase 2 (ROCK2) as a crucial driver of OS cell migration. In this study, we explored the impact of ROCK2 disruption on the metastatic capabilities of OS cells and analyzed its functional relationship with Yes-associated protein-1 (YAP), the main transcriptional mediator of mechanotransduction signaling.

Methods

The effects of ROCK2 depletion on metastasis were studied in NOD Scid gamma (NSG) mice injected with U-2OS cells in which ROCK2 expression had been stably silenced. Functional studies were performed in vitro in human U-2OS cells and in three novel cell lines derived from patient-derived xenografts (PDXs) by using standard methods to evaluate malignancy parameters and signaling transduction. The nuclear immunostaining of YAP and the evaluation of its downstream targets Cysteine Rich Angiogenic Inducer 6, Connective Tissue Growth Factor and Cyclin D1 by quantitative PCR were performed to analyze YAP activity. The effect of the expression and activity of ROCK2 and YAP on tumor progression was analyzed in 175 OS primary tumors.

Results

The silencing of ROCK2 markedly reduced tumor growth and completely abolished the metastatic ability of U-2OS cells. The depletion of ROCK2, either by pharmacological inhibition or silencing, induced a dose- and time-dependent reduction in the nuclear expression and transcriptional activity of YAP. The nuclear expression of YAP was observed in 80/175 (46%) tumor samples and was significantly correlated with worse patient prognosis and a higher likelihood of metastasis and death. The use of verteporfin, a molecule that specifically inhibits the TEAD–YAP association, remarkably impaired the growth and migration of OS cells in vitro. Moreover to inhibiting YAP activity, our findings indicate that verteporfin also affects the ROCK2 protein and its functions.

Conclusions

We describe the functional connection between ROCK2 and YAP in the regulation of OS cell migration and metastasis formation. These data provide support for the use of verteporfin as a possible therapeutic option to prevent OS cell dissemination.

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.

Abstract P2-04-01: Human papillomavirus (HPV) DNA detection in breast cancer by liquid biopsy: Something new on the horizon?

Background The presence of human papillomavirus (HPV) DNA in breast cancer (BC) tissues has been widely investigated in recent years. HPV DNA has been detected in ductal lavage fluids and in serum-derived extracellular vesicles of patients with benign or in situ breast lesions. However, there are no data attesting to its presence in liquid biopsies of different BC subtypes or to its impact on prognosis.

Methods We analyzed a total of 72 serum samples for the presence of circulating HPV DNA, of which 20 were from luminal A BC (5 relapsed, 15 non relapsed), 17 from luminal B BC (5 relapsed, 12 non relapsed), 15 from triple-negative BC (6 relapsed and 9 non relapsed), 12 from HER2-positive BC (3 relapsed, 9 non relapsed) and 8 from healthy subjects. Circulating DNA was extracted and purified from 500 μl of serum by Qiamp DNA minikit (Qiagen, Milan, Italy) according to the manufacturer's instructions. HPV DNA was assessed by a high-throughput MALDI-TOF mass spectrometry-based method (Mass Array Platform, Agena Bioscience, Hamburg, Germany). The DNA target sequence was amplified by a multiplex PCR with HPV E6 or E7 gene-specific primers. A primer for primer extension annealing to the amplified product was extended at its 3′ terminal base for each HPV type.

Results HPV DNA was detected in 5 BC patients but in none of the healthy controls. None of the serum samples analyzed showed HPV DNA types 16 or 18. Four of the 5 BC cases had high-risk HPV DNA (type 39,45,52,59) and one had low-risk HPV DNA (type 73). The 4 patients with high risk HPV DNA had low-grade cervical intraepithelial neoplasia (CIN 1) detected by Pap smear prior to the diagnosis of BC. No relation was found between HPV infection and tumor subtype or prognosis. Our in vitro studies also revealed the active release of HPV DNA into the extracellular vesicle compartment of cervical cancer cells.

Table 1.Features of BC patients positive for circulating HPV DNA.Sample IDAge (years)GradingSubtypeDeathRelapseHPV type, riskCervical lesion17471Luminal A-No59, highCIN 139783Luminal B20/03/2015No45, highCIN 145462Luminal B-No39, highCIN 160583TN03/01/2011Yes73, lowHyperplasia63523HER2-positive-Yes52, highCIN 1TN, triple negative; CIN 1:low-grade cervical intraepithelial neoplasia

Conclusions Our findings support the feasibility of HPV DNA evaluation by liquid biopsy in BC. They also suggest that circulating HPV DNA in BC patients might be of cervical tissue origin and that the presence of HPV DNA in BC may be a consequence of its spreading from virus-infected tissue such as that of the uterine cervix.

Citation Format: Bravaccini S, Ravaioli S, Rocca A, Maltoni R, Cristalli C, Marasco E, De Carolis S, Cricca M, Bonafè M. Human papillomavirus (HPV) DNA detection in breast cancer by liquid biopsy: Something new on the horizon? [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-04-01.

Abstract 2079: Collection of patient-derived xenografts (PDX) to study the biology and therapy of bone sarcomas

Osteosarcoma (OS) and Ewing's sarcoma (EWS) are the two most common pediatric solid tumors, after brain tumors. Multimodal treatments have significantly improved prognosis in localized disease but outcome is still poor in metastatic patients, for whom therapeutic options are often inadequate. Preclinical drug testing to identify promising treatment options that match the molecular make-up of these tumors is hampered by the lack of appropriate and molecularly well-characterized patient-derived models. To address this need, a panel of patient-derived- xenografts (PDXs) was established by subcutaneous implantation of fresh, surgically resected OS and EWS tumors in NSG mice. Tumors were re-transplanted to next mice generations and fragments were collected for histopathological and molecular characterization. A model was considered established after observing stable histological and molecular features for at least three passages. To evaluate the similarity of the model with primary tumor, we performed a global gene expression profiling and tissue microarrays (TMA), to assess tumor specific biomarkers on tissues from OS/EWS tumors and their PDXs (1st and 3rd passage). Moreover, we verified the feasibility of these models for preclinical drug testing. We implanted 61 OS and 29 EWS samples: 14/38 (37%) primary OS and 9/23 (39%) OS lung metastases successfully engrafted; while among EWS, 5/26 (19%) primary samples and 1/3 (33%) metastases were established. Comparison between patient samples and PDXs, highlighted that histology and genetic characteristics of PDXs were stable and maintained over passages. In particular, correlative analysis between OS and EWS samples and their PDXs was extremely high (Pearson's r range r=0.94-0.96), while patient-derived primary cultures displayed reduced correlation with human samples (r=0.90-0.93), indicating that in vitro adaptation superimpose molecular alterations that create genetic diversion from original tumors. No significant differentially expressed gene profile was observed from the comparison between EWS samples and PDXs (fold change > 2, adjusted p <0.05 at paired t-test). In OS, the comparison between OS patient-derived tumors and PDX indicated differences in 397 genes, mostly belonging to immune system functional category. This is in line with the idea that human immune cells are gradually replaced by murine counterparts upon engraftment in the mouse. As proof-of concept, two EWS PDX and one OS PDX have been treated with conventional and innovated drugs to test their value in terms of drug-sensitivity prediction. Overall, our study indicated that PDX models maintained the histological and genetic markers of the tumor samples and represent reliable models to test sensitivity to novel drug associations. Grants AIRC (IG 18451 to KS; IG15324 to P-LL), Italian Ministry of Health (ER2017 2364984-ERANET. to KS; RF-2013-02357552 to P-LL)

Citation Format: Maria Cristina Manara, Giordano Nicoletti, Manuela Ferracin, Camilla Cristalli, Alberto Righi, Mauro Magnani, Michela Pasello, Piero Picci, Patrizia Nanni, Pier-Luigi Lollini, Katia Scotlandi. Collection of patient-derived xenografts (PDX) to study the biology and therapy of bone sarcomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2079.

Abstract 2946: Effects of two novel quinoline-based non-nucleoside DNA methyltransferase inhibitors against bone sarcomas

Introduction.

Identification of new drugs against sarcomas still represents an urgent clinical need due to the rarity of these diseases. Aberrant DNA methylation of gene promoter regions is recognized to be highly involved in cancer and efforts have been made to synthesize non-nucleoside compounds that can effectively modulate gene expression, with bearable side effects. Two novel DNMT inhibitors (DNMTi), MC3353 and MC3343, were tested in Ewing sarcoma (EWS) and osteosarcoma (OS) cell lines to determine their effects on proliferation, apoptosis/necrosis induction, and cell differentiation.

Methods and Results.

We evaluated specificity on DNMTs inhibition of these compounds together with anticancer activities (cell growth inhibition, cell cycle perturbations, effects on programmed cell death) in a panel of EWS and OS cell lines. Cellular response to DNMTi treatment was assessed also at the molecular level by evaluation of key regulators of cell cycle and apoptosis. Effects on neural differentiation were assessed by β-III tubulin and heavy neurofilament modulation in Ewing sarcoma cells. Concurrently, effects on osteoblastic differentiation were carried out on Saos-2 OS cell line and evaluated by RT-PCR. Both inhibitors determined a significant inhibition of DNMTs activity. In vitro, MC3343 was found to slow cell proliferation by increasing the percentage of cells in G1 or G2/M phases, while MC3353 compound was unable to modulate cell cycle but induced an increase in cell death indicating a cytotoxic rather than a cytostatic effect. Modulation of key regulators of cell cycle and evaluation of PARP cleavage confirmed these results. Both DNMTi induced cell differentiation. In EWS, treatment significantly modulated the expression of neural markers (positivity to β-III tubulin; NF-H; neurite outgrowth). In OS cells, DNMTi increased both matrix mineralization and expression of genes specifically related to osteoblastogenesis.

Conclusions.

Non-nucleoside DNMTi may represent a possible new therapeutic approach to bone sarcoma.

Grants from: Association for Cancer Research (IG2013_14049; to KS); 5 per mille contributions to Rizzoli Institute. FIRB RBFR10ZJQT, IIT-Sapienza Project, and FP7 Projects BLUEPRINT/282510 and A-ParaDDise/602080 to AM. CC is a recipient of a fellowship from the Associazione Onlus “il Pensatore: Matteo Amitrano”

Citation Format: Maria Cristina Manara, Sergio Valente, Camilla Cristalli, Cristina Baricordi, Clemens Zwergel, Paola B Arimondo, Piero Picci, Antonello Mai, Katia Scotlandi. Effects of two novel quinoline-based non-nucleoside DNA methyltransferase inhibitors against bone sarcomas. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2946. doi:10.1158/1538-7445.AM2015-2946

A mathematical study of some biomechanical factors affecting the oscillometric blood pressure measurement

A mathematical lumped parameter model of the oscillometric technique for indirect blood pressure measurement is presented. The model includes cuff compliance, pressure transmission from the cuff to the brachial artery through the soft tissue of the arm, and the biomechanics of the brachial artery both at positive and negative transmural pressure values. The main aspects of oscillometry are simulated i.e., the increase in cuff pressure pulsatility during cuff deflation maneuvers, the existence of a point of maximum pulsations (about 1.5 mmHg) at a cuff pressure close to mean arterial pressure, and the characteristic ratios for cuff pressure pulsatility at systole and diastole (0.52 and 0.70, respectively, with this model, using basal parameters and an individual set of data for the arterial pressure waveform). Subsequently, the model is used to examine how alterations in some biomechanical factors may prejudice the accuracy of pressure measurement. Numerical simulations indicate that alterations in wall viscoelastic properties and in arterial pressure pulse amplitude may significantly affect the accuracy of pressure estimates, leading to errors as great as 15-20% in the computation of diastolic and systolic arterial pressure. By contrast, changes in arterial pressure mean value and cuff compliance do not seem to have significant influence on the measurement. Evaluation of mean arterial pressure through a characteristic ratio is not robust and may lead to misleading results. Mean arterial pressure may be better evaluated as the lowest pressure at which cuff pulse amplitude reaches a plateau. The obtained results may help to explain the nature of errors which usually limit the reliability of arterial pressure measurement (for instance in the elderly).

Mathematical modeling of noninvasive blood pressure estimation techniques--Part I: Pressure transmission across the arm tissue

A mathematical model of the arm tissue mechanical behavior under the effect of external pressure loads is presented. The model has been used to study stress and strain distribution across the tissue, and pressure transmission to the brachial artery, when the arm is compressed by two adjacent cuffs independently inflated. Using this configuration, the tissue elastic parameters (Young modulus and Poisson ratio) can be individually identified using a simple and noninvasive experimental procedure. Model validation has been achieved by comparing its results with data obtained experimentally on 10 subjects. These comparisons demonstrate that the proposed model may constitute a simple but valid new tool able to describe tissue behavior, subjected to external pressures, with sufficient accuracy. Joined with a model of brachial hemodynamics, it might contribute to improve our understanding of noninvasive blood pressure estimation techniques.

Mathematical modeling of noninvasive blood pressure estimation techniques--Part II: Brachial hemodynamics

The main biomechanical factors which may affect the accuracy of the oscillometric method for indirect blood pressure measurement are analyzed using a new model of brachial hemodynamics. In a first stage of this work, the model has been used to reproduce some well-known responses of collapsing arteries, such as the sharp increase in compliance, and the nonlinear pressure-flow characteristic with negative dynamic resistance. In a second stage the model has been linked to the arm tissue mechanics description presented in a previous work. The final model so obtained has then been employed to analyze the pattern of the main hemodynamic quantities (pressure pulsations in the cuffs, blood volume changes, blood flow upstream and downstream of the cuffs) during deflation manoeuvres. The simulation results agree with those found in the recent literature quite well. Results indicate that the cuff pressure value for maximum pulsations exhibits a large plateau, located approximately around the mean arterial pressure. However, stiffness of wall artery, or stretching of the cuff internal surface, may significantly alter the obtained results causing a phenomena of "pseudo-hypertension."