Neuroblastoma patient-derived cultures are enriched for a mesenchymal gene signature and reflect individual drug response.

Ex vivo evaluation of personalized models can facilitate individualized treatment selection for patients, and advance the discovery of novel therapeutic options. However, for embryonal malignancies, representative primary cultures have been difficult to establish. We developed patient-derived cell cultures (PDCs) from chemo-naïve and post-treatment neuroblastoma tumors in a consistent and efficient manner, and characterized their in vitro growth dynamics, histomorphology, gene expression, and functional chemo-response. From 34 neuroblastoma tumors, 22 engrafted in vitro to generate 31 individual PDC lines, with higher engraftment seen with metastatic tumors. PDCs displayed characteristic immunohistochemical staining patterns of PHOX2B, TH, and GD2 synthase. Concordance of MYCN amplification, 1p and 11q deletion between PDCs and patient tumors was 83.3%, 72.7%, and 80.0% respectively. PDCs displayed a predominantly mesenchymal-type gene expression signature and showed upregulation of pro-angiogenic factors that were similarly enriched in culture medium and paired patient serum samples. When tested with standard-of-care cytotoxics at human Cmax -equivalent concentrations, MYCN-amplified and non-MYCN-amplified PDCs showed a differential response to cyclophosphamide and topotecan, which mirrored the corresponding patients' responses, and correlated with gene signatures of chemosensitivity. In this translational proof-of-concept study, early-phase neuroblastoma PDCs enriched for the mesenchymal cell subpopulation recapitulated the individual molecular and phenotypic profile of patient tumors, and highlighted their potential as a platform for individualized ex vivo drug-response testing.

Clinicopathological and treatment response characteristics of updated rhabdomyosarcoma histomolecular subtypes: An Asian population-based study.

AIM: New histomolecular subtypes of rhabdomyosarcoma have recently been defined but their corresponding clinical characteristics are not well described. Also, these clinical phenotypes vary greatly by age and ethnicity but have not been profiled in Asian populations. Thus, we sought to determine the landscape of rhabdomyosarcoma subtypes in a national Asian cohort and compare clinical characteristics among age groups and molecular subtypes. METHODS: We performed a retrospective population-based study of all rhabdomyosarcoma patients in Singapore public hospitals from 2004 to 2014 (n = 67), and assigned histomolecular subtypes according to the updated 2020 WHO classification of soft tissue tumors following central pathology review and molecular profiling. RESULTS: Age-specific prevalence followed a tri-modal peak. There were significantly more embryonal and alveolar (p = 0.032) and genitourinary (non-bladder/prostate) tumors (p = 0.033) among children. Older age was associated with complete resection among spindle cell/sclerosing tumors (p = 0.027), with the omission of chemotherapy among embryonal tumors (p = 0.001), and with poorer survival among embryonal and alveolar tumors (p = 0.026, p = 0.022, respectively). Overall survival differed with stage, group, and surgical resection, adjusted for age group (p = 0.004, p = 0.001, p = 0.004, respectively). Spindle-cell/sclerosing tumors showed an indolent phenotype with a significantly lower incidence of nodal metastasis (p = 0.002), but two of 15 patients with MYOD1 mutations had a contrastingly aggressive disease. CONCLUSION: Disease and treatment response profiles of rhabdomyosarcoma subtypes vary significantly between adults and children, especially surgical resectability. In our Asian population, poorer outcomes were observed in adults with embryonal and alveolar tumors, while activating mutations influence the behavior of otherwise favorable spindle cell/sclerosing tumors.

Targeting mutant dicer tumorigenesis in pleuropulmonary blastoma via inhibition of RNA polymerase I.

DICER1 mutations predispose to increased risk for various cancers, particularly pleuropulmonary blastoma (PPB), the commonest lung malignancy of childhood. There is a paucity of directly actionable molecular targets as these tumors are driven by loss-of-function mutations of DICER1. Therapeutic development for PPB is further limited by a lack of biologically and physiologically-representative disease models. Given recent evidence of Dicer's role as a haploinsufficient tumor suppressor regulating RNA polymerase I (Pol I), Pol I inhibition could abrogate mutant Dicer-mediated accumulation of stalled polymerases to trigger apoptosis. Hence, we developed a novel subpleural orthotopic PPB patient-derived xenograft (PDX) model that retained both RNase IIIa and IIIb hotspot mutations and recapitulated the cardiorespiratory physiology of intra-thoracic disease, and with it evaluated the tolerability and efficacy of first-in-class Pol I inhibitor CX-5461. In PDX tumors, CX-5461 significantly reduced H3K9 di-methylation and increased nuclear p53 expression, within 24 hours' exposure. Following treatment at the maximum tolerated dosing regimen (12 doses, 30 mg/kg), tumors were smaller and less hemorrhagic than controls, with significantly decreased cellular proliferation, and increased apoptosis. As demonstrated in a novel intrathoracic tumor model of PPB, Pol I inhibition with CX-5461 could be a tolerable and clinically-feasible therapeutic strategy for mutant Dicer tumors, inducing antitumor effects by decreasing H3K9 methylation and enhancing p53-mediated apoptosis.