The long road to immunotherapy for childhood rhabdomyosarcoma

Targeted immunotherapy and nanomedicine for rhabdomyosarcoma: The way of the future

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of childhood. Histology separates two main subtypes: embryonal RMS (eRMS; 60%-70%) and alveolar RMS (aRMS; 20%-30%). The aggressive aRMS carry one of two characteristic chromosomal translocations that result in the expression of a PAX3::FOXO1 or PAX7::FOXO1 fusion transcription factor; therefore, aRMS are now classified as fusion-positive (FP) RMS. Embryonal RMS have a better prognosis and are clinically indistinguishable from fusion-negative (FN) RMS. Next to histology and molecular characteristics, RMS risk groupings are now available defining low risk tumors with excellent outcomes and advanced stage disease with poor prognosis, with an overall survival of about only 20% despite intensified multimodal treatment. Therefore, development of novel effective targeted strategies to increase survival and to decrease long-term side effects is urgently needed. Recently, immunotherapies and nanomedicine have been emerging for potent and effective tumor treatments with minimal side effects, raising hopes for effective and safe cures for RMS patients. This review aims to describe the most relevant preclinical and clinical studies in immunotherapy and targeted nanomedicine performed so far in RMS and to provide an insight in future developments.

Macrophage migration inhibitory factor (MIF) is induced by cytotoxic drugs and is involved in immune escape and migration in childhood rhabdomyosarcoma

Macrophage migration inhibitory factor (MIF) is known to be involved in oncogenic transformation, tumour progression, and immunosuppression and is overexpressed in many solid tumours, including paediatric rhabdomyosarcoma (RMS). We investigated the function of MIF in RMS during treatment with cytotoxic drugs. RMS cell lines were analysed by flow cytometry, immunofluorescence staining, and ELISA. We demonstrated the overexpression of MIF in RMS cells and the enhanced expression and secretion after treatment with cytotoxic agents. Migration assays of RMS cells revealed that inhibitors of MIF (ISO-1, Ant.III 4-IPP, Ant.V, sulforaphane (SF)) and blocking antibodies caused reduced migration, indicating a role for MIF in metastatic invasion. Additionally, we investigated the function of MIF in immune escape. The development of a population containing immunosuppressive myeloid-derived suppressor cells was promoted by incubation in conditioned medium of RMS cells comprising MIF and was reversed by MIF inhibitors but not by antibodies. Although most inhibitors may restore immune activity, Ant.III and 10 µM SF disturbed T cell proliferation in a CFSE assay, whereas T cell proliferation was not reduced by 3 µM SF, ISO-1 or antibodies. However, the inhibition of MIF by blocking antibodies did not increase the killing activity of allogenic PBMCs co-cultured with RMS cells. Our results reveal that MIF may be involved in an immune escape mechanism and demonstrate the involvement of MIF in immunogenic cell death during treatment with cytotoxic drugs. Targeting MIF may contribute to the restoration of immune sensitivity and the control of migration and metastatic invasion.

Proof-of-concept rare cancers in drug development: the case for rhabdomyosarcoma

Rare diseases typically affect fewer than 200,000 patients annually, yet because thousands of rare diseases exist, the cumulative impact is millions of patients worldwide. Every form of childhood cancer qualifies as a rare disease-including the childhood muscle cancer, rhabdomyosarcoma (RMS). The next few years promise to be an exceptionally good era of opportunity for public-private collaboration for rare and childhood cancers. Not only do certain governmental regulation advantages exist, but these advantages are being made permanent with special incentives for pediatric orphan drug-product development. Coupled with a growing understanding of sarcoma tumor biology, synergy with pharmaceutical muscle disease drug-development programs, and emerging publically available preclinical and clinical tools, the outlook for academic-community-industry partnerships in RMS drug development looks promising.