Osteosarcoma PDX-Derived Cell Line Models for Preclinical Drug Evaluation Demonstrate Metastasis Inhibition by Dinaciclib through a Genome-Targeted Approach

PURPOSE

Models to study metastatic disease in rare cancers are needed to advance preclinical therapeutics and to gain insight into disease biology. Osteosarcoma is a rare cancer with a complex genomic landscape in which outcomes for patients with metastatic disease are poor. As osteosarcoma genomes are highly heterogeneous, multiple models are needed to fully elucidate key aspects of disease biology and to recapitulate clinically relevant phenotypes.

EXPERIMENTAL DESIGN

Matched patient samples, patient-derived xenografts (PDX), and PDX-derived cell lines were comprehensively evaluated using whole-genome sequencing and RNA sequencing. The in vivo metastatic phenotype of the PDX-derived cell lines was characterized in both an intravenous and an orthotopic murine model. As a proof-of-concept study, we tested the preclinical effectiveness of a cyclin-dependent kinase inhibitor on the growth of metastatic tumors in an orthotopic amputation model.

RESULTS

PDXs and PDX-derived cell lines largely maintained the expression profiles of the patient from which they were derived despite the emergence of whole-genome duplication in a subset of cell lines. The cell lines were heterogeneous in their metastatic capacity, and heterogeneous tissue tropism was observed in both intravenous and orthotopic models. Single-agent dinaciclib was effective at dramatically reducing the metastatic burden.

CONCLUSIONS

The variation in metastasis predilection sites between osteosarcoma PDX-derived cell lines demonstrates their ability to recapitulate the spectrum of the disease observed in patients. We describe here a panel of new osteosarcoma PDX-derived cell lines that we believe will be of wide use to the osteosarcoma research community.

Development and characterization of new patient-derived xenograft (PDX) models of osteosarcoma with distinct metastatic capacities

Models to study metastatic disease in rare cancers are needed to advance preclinical therapeutics and to gain insight into disease biology, especially for highly aggressive cancers with a propensity for metastatic spread. Osteosarcoma is a rare cancer with a complex genomic landscape in which outcomes for patients with metastatic disease are poor. As osteosarcoma genomes are highly heterogeneous, a large panel of models is needed to fully elucidate key aspects of disease biology and to recapitulate clinically-relevant phenotypes. We describe the development and characterization of osteosarcoma patient-derived xenografts (PDXs) and a panel of PDX-derived cell lines. Matched patient samples, PDXs, and PDX-derived cell lines were comprehensively evaluated using whole genome sequencing and RNA sequencing. PDXs and PDX-derived cell lines largely maintained the expression profiles of the patient from which they were derived despite the emergence of whole-genome duplication (WGD) in a subset of cell lines. These cell line models were heterogeneous in their metastatic capacity and their tissue tropism as observed in both intravenous and orthotopic models. As proof-of-concept study, we used one of these models to test the preclinical effectiveness of a CDK inhibitor on the growth of metastatic tumors in an orthotopic amputation model. Single-agent dinaciclib was effective at dramatically reducing the metastatic burden in this model.

Abstract A51: STING activation overcomes immune escape in osteosarcoma metastasis

Chromosomal instability (CIN) has been known to be a hallmark of cancer for decades, but how CIN influences the tumor microenvironment (TME) and defines the ability of tumors to metastasize is a fundamental question in cancer biology that remains unanswered. Osteosarcoma (OS) is a highly malignant bone tumor characterized by high CIN and an immunosuppressive TME and is thus an excellent model system to address the role of CIN in metastasis and TME programming. The cGAS-STING-ENPP1 pathway links CIN to immune evasion and metastasis, functioning to produce an immune response upon sensing cytoplasmic double-stranded DNA (dsDNA) and transducing this signal via the second messenger cGAMP, which activates interferon gene expression. CIN in cancer cells also results in cytosolic dsDNA which can also activate the STING pathway. However, cGAMP can also be hydrolyzed by ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), which negatively regulates STING activation in the TME, enabling cancer cells to survive CIN and avoid immune surveillance. Our studies of this pathway in human-in-mouse metastasis models of OS indicate that either ENPP1 overexpression (OE) or STING knockout (KO) enhance metastasis, nominating the STING pathway as an important regulator metastasis in OS and suggesting that STING agonists or ENPP1 inhibitors may have therapeutic benefit. Indeed, OS patient-derived xenograft cell lines that are least aggressive in vivo show strong STING activation in response to transfection with dsDNA, while cell lines with a higher metastatic capacity do not, suggesting that metastatic capacity may be directly linked to STING pathway downregulation. Given that a fully competent murine immune system is crucial for evaluation of the STING pathway in mediating antitumor immunity, a major current focus of this work is development and use of syngeneic murine OS models for further in vivo dissection of the role of the STING-ENPP1 axis in OS. Future studies will also evaluate if ENPP1 inhibition constitutes a novel immune-targeted therapeutic that may overcome an immunosuppressive TME and activate the immune system in response to the cell-intrinsic consequences of CIN. Moreover, elucidating the immune cell types that drive STING-mediated anti-tumor immunity will inform new combinatorial approaches together with ENPP1 inhibition. Given the therapeutic relevance of TME reprogramming and the limited success that immunotherapy has garnered in many solid tumors, this line of investigation has broad applicability beyond OS and may enable rational design of novel combination immunotherapies to treat metastatic sarcomas and other CIN-high cancers.

Citation Format: Elizabeth "Betsy" P Young, Courtney R Schott, Amanda Koehne, Christine Johnson, E. Alejandro Sweet-Cordero. STING activation overcomes immune escape in osteosarcoma metastasis [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr A51.

Abstract A005: STING activation overcomes immune escape in osteosarcoma metastasis

Chromosomal instability (CIN) has been known to be a hallmark of cancer for decades, but how CIN influences the tumor microenvironment (TME) and defines the ability of tumors to metastasize is a fundamental question in cancer biology that remains unanswered. Osteosarcoma (OS) is a highly malignant bone tumor characterized by high CIN and an immunosuppressive TME and is thus an excellent model system to address the role of CIN in metastasis and TME programming. The cGAS-STING-ENPP1 pathway links CIN to immune evasion and metastasis, functioning to produce an immune response to infection by sensing cytoplasmic double-stranded DNA (dsDNA) and transducing this signal via the second messenger cGAMP, which activates interferon gene expression. CIN in cancer cells also results in cytosolic dsDNA which can also activate the STING pathway. However, cGAMP can also be hydrolyzed by ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), which negatively regulates STING activation in the TME, enabling cancer cells to survive CIN and avoid immune surveillance. Our studies of this pathway in human-in-mouse metastasis models of OS indicate that either ENPP1 overexpression (OE) or STING knockout (KO) enhance metastasis, nominating the STING pathway as an important regulator metastasis in OS and suggesting that STING agonists or ENPP1 inhibitors may have therapeutic benefit. Indeed, OS patient-derived xenograft cell lines that are least aggressive in vivo show strong STING activation in response to transfection with dsDNA, while cell lines with a higher metastatic capacity do not, suggesting that metastatic capacity may be directly linked to STING pathway downregulation. Given that a fully competent murine immune system is crucial for evaluation of the STING pathway in mediating antitumor immunity, a major current focus of this work is development and use of syngeneic murine OS models for further in vivo dissection of the role of the STING-ENPP1 axis in OS. Future studies will also evaluate if ENPP1 inhibition constitutes a novel immune-targeted therapeutic that may overcome an immunosuppressive TME and activate the immune system in response to the cell-intrinsic consequences of CIN. Moreover, elucidating the immune cell types that drive STING-mediated anti-tumor immunity will inform new combinatorial approaches together with ENPP1 inhibition. Given the therapeutic relevance of TME reprogramming and the limited success that immunotherapy has garnered in many solid tumors, this line of investigation has broad applicability beyond OS and may enable rational design of novel combination immunotherapies to treat metastatic sarcomas and other CIN-high cancers.

Citation Format: Elizabeth "Betsy" Young, Courtney R. Schott, E. Alejandro Sweet-Cordero. STING activation overcomes immune escape in osteosarcoma metastasis [abstract]. In: Proceedings of the AACR Special Conference: Sarcomas; 2022 May 9-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(18_Suppl):Abstract nr A005.

Evaluation of metronomic cyclophosphamide chemotherapy as maintenance treatment for dogs with appendicular osteosarcoma following limb amputation and carboplatin chemotherapy

OBJECTIVE To determine the effectiveness of metronomic cyclophosphamide (MC) chemotherapy (primary treatment of interest) with adjuvant meloxicam administration as maintenance treatment for dogs with appendicular osteosarcoma following limb amputation and carboplatin chemotherapy. DESIGN Retrospective case series with nested cohort study. ANIMALS 39 dogs with a histologic diagnosis of appendicular osteosarcoma that underwent limb amputation and completed carboplatin chemotherapy from January 2011 through December 2015. PROCEDURES Dogs were grouped by whether carboplatin chemotherapy had been followed with or without MC chemotherapy (15 mg/m², PO, q 24 h) and meloxicam (0.1 mg/kg [0.045 mg/lb], PO, q 24 h). The Breslow rank test was used to assess whether MC chemotherapy was associated with overall survival time (OST) and disease progression-free time (PFT) after limb amputation. RESULTS 19 dogs received carboplatin and MC chemotherapy, and 20 dogs received only carboplatin chemotherapy. No differences were identified between these groups regarding age, reproductive status, body weight, serum alkaline phosphatase activity, tumor location, or histologic grade or subtype of osteosarcoma. Median duration of MC chemotherapy for dogs in the carboplatin-MC group was 94 days (range, 7 to 586 days); this treatment was discontinued for 11 (58%) dogs when cystitis developed. Overall, 11 (28%) dogs survived to the time of analysis, for a median follow-up period of 450 days (range, 204 to 1,400 days). No difference in median PFT or OST was identified between the 2 groups. CONCLUSIONS AND CLINICAL RELEVANCE Maintenance MC chemotherapy following limb amputation and completed carboplatin chemotherapy was associated with no increase in PFT or OST in dogs with appendicular osteosarcoma. Cystitis was common in MC-treated dogs, and prophylactic treatment such as furosemide administration could be considered to reduce the incidence of cystitis in such dogs.

Cross-species genomic landscape comparison of human mucosal melanoma with canine oral and equine melanoma

Mucosal melanoma is a rare and poorly characterized subtype of human melanoma. Here we perform a cross-species analysis by sequencing tumor-germline pairs from 46 primary human muscosal, 65 primary canine oral and 28 primary equine melanoma cases from mucosal sites. Analysis of these data reveals recurrently mutated driver genes shared between species such as NRAS, FAT4, PTPRJ, TP53 and PTEN, and pathogenic germline alleles of BRCA1, BRCA2 and TP53. We identify a UV mutation signature in a small number of samples, including human cases from the lip and nasal mucosa. A cross-species comparative analysis of recurrent copy number alterations identifies several candidate drivers including MDM2, B2M, KNSTRN and BUB1B. Comparison of somatic mutations in recurrences and metastases to those in the primary tumor suggests pervasive intra-tumor heterogeneity. Collectively, these studies suggest a convergence of some genetic changes in mucosal melanomas between species but also distinctly different paths to tumorigenesis.

An evaluation of TAZ and YAP crosstalk with TGFβ signalling in canine osteosarcoma suggests involvement of hippo signalling in disease progression

Background

Osteosarcoma (OSA) is the most common bone cancer in canines. Both transforming growth factor beta (TGFβ) and Hippo pathway mediators have important roles in bone development, stemness, and cancer progression. The role of Hippo signalling effectors TAZ and YAP has never been addressed in canine OSA. Further, the cooperative role of TGFβ and Hippo signalling has yet to be explored in osteosarcoma. To address these gaps, this study investigated the prognostic value of TAZ and YAP alone and in combination with pSmad2 (a marker of active TGFβ signalling), as well as the involvement of a TGFβ-Hippo signalling crosstalk in tumourigenic properties of OSA cells in vitro. An in-house trial tissue microarray (TMA) which contained 16 canine appendicular OSA cases undergoing standard care and accompanying follow-up was used to explore the prognostic role of TAZ, YAP and pSmad2. Published datasets were used to test associations between TAZ and YAP mRNA levels, metastasis, and disease recurrence. Small interfering RNAs specific to TAZ and YAP were utilized in vitro alone or in combination with TGFβ treatment to determine their role in OSA viability, proliferation and migration.

Results

Patients with low levels of both YAP and pSmad2 when evaluated in combination had a significantly longer time to metastasis (log-rank test, p = 0.0058) and a longer overall survival (log rank test, p = 0.0002). No similar associations were found for TAZ and YAP mRNA levels. In vitro, TAZ knockdown significantly decreased cell viability, proliferation, and migration in metastatic cell lines, while YAP knockdown significantly decreased viability in three cell lines, and migration in two cell lines, derived from either primary tumours or their metastases. The impact of TGFβ signaling activation on these effects was cell line-dependent.

Conclusions

YAP and pSmad2 have potential prognostic value in canine appendicular osteosarcoma. Inhibiting YAP and TAZ function could lead to a decrease in viability, proliferation, and migratory capacity of canine OSA cells. Assessment of YAP and pSmad2 in larger patient cohorts in future studies are needed to further elucidate the role of TGFβ-Hippo signalling crosstalk in canine OSA progression.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1651-5) contains supplementary material, which is available to authorized users.

The autophagy inhibitor spautin-1, either alone or combined with doxorubicin, decreases cell survival and colony formation in canine appendicular osteosarcoma cells

Dogs diagnosed with appendicular osteosarcoma typically succumb to metastatic disease within a year of diagnosis. The current standard of care for curative intent, amputation followed by adjuvant chemotherapy, increases survival time but chemoresistance is a major contributor to mortality. Unfortunately, the mechanisms driving the progression of metastatic disease and the development of chemoresistance are unknown. One theory is that autophagy may contribute to chemoresistance by providing neoplastic cells with a mechanism to survive chemotherapy treatment. Our objective was to evaluate the effect of combining an autophagy inhibitor with a standard chemotherapeutic drug on response to chemotherapy in canine appendicular osteosarcoma cells. We hypothesized that combining the autophagy inhibitor spautin-1 with doxorubicin treatment would enhance chemoresponsiveness. Using commercial (D17) and primary cell lines derived from 1° and 2° sites of osteosarcoma, we showed that this combination treatment enhances cell killing and inhibits colony formation. Our findings support the theory that autophagy contributes to chemoresistance in canine appendicular osteosarcoma and indicate that adding an autophagy inhibitor to the standard of care has the potential to improve outcome.

Histologic Grade Does Not Predict Outcome in Dogs with Appendicular Osteosarcoma Receiving the Standard of Care

Canine appendicular osteosarcoma is an aggressive bone neoplasm that imposes a short survival time. There are several published histologic grading systems for canine osteosarcoma but no universally accepted system. Location within the skeleton and therapy received are both correlated with survival time, but these factors were not always considered when the prognostic value of published grading systems was determined. Our objective was to compare 2 published histologic grading systems in a population of dogs with appendicular osteosarcoma treated with the standard of care for curative intent. Three evaluators graded 85 tumors using 2 histologic grading systems. The relationships between histologic grade as well as individual histologic features and outcome (survival time and disease-free interval) were evaluated using Kaplan-Meier survival functions and a univariate Cox proportional hazards model. Histologic grade, as assigned by any evaluator, did not correlate with outcome. Increased number of mitotic figures per 3 randomly selected 400× microscope fields, as assessed by 1 evaluator, was correlated with both survival time and disease-free interval; this was the only individual histologic feature that was significantly correlated with outcome for any evaluator. These findings cast doubt on the predictive value of routine histologic grading in dogs with appendicular osteosarcoma who receive amputation followed by adjuvant chemotherapy and highlight the need for better tools to predict outcome in canine appendicular osteosarcoma.

Mitral annular calcification. Clinical and echocardiographic correlations

Clinical, echocardiographic, and radiographic findings in 41 patients with mital annular calcification are presented. Clinical diagnosis included rheumatic heart disease (32%), noninflammatory calcific disease (34%), and chronic renal failure (32%). Mitral annular calcification is recognized echocardiographically as a dense echo band beneath the posterior mitral leaflet with motion paralleling that of the free left ventricular wall. Only two patients of 41 (5%) with mitral annular calcification had calcification on routine x-ray films, and six of 16 (38%) on cinefluoroscopy. The left atrial size is enlarged, and the mitral leaflets are thickened, with reduced motion (D-E) in rheumatic heart disease, but the leaflet motion is well preserved in the nonrheumatic patients. The association of mitral annular calcification with idiopathic hypertrophic subaortic stenosis, chronic renal failure, and bacterial endocarditis is discussed. Echocardiography appears to be a sensitive method of detecting mitral annular calcification and may be helpful in differentiating rheumatic and nonrheumatic etiologies.