Pediatric Anaplastic Embryonal Rhabdomyosarcoma: Targeted Therapy Guided by Genetic Analysis and a Patient-Derived Xenograft Study

Abstract

Therapy for rhabdomyosarcoma (RMS) has generally been limited to combinations of conventional cytotoxic agents similar to regimens originally developed in the late 1960s. Recently, identification of molecular alterations through next-generation sequencing of individual tumor specimens has facilitated the use of more targeted therapeutic approaches for various malignancies. Such targeted therapies have revolutionized treatment for some cancer types. However, malignancies common in children, thus far, have been less amenable to such targeted therapies. This report describes the clinical course of an 8-year-old female with embryonal RMS having anaplastic features. This patient experienced multiple relapses after receiving various established and experimental therapies. Genomic testing of this RMS subtype revealed mutations in BCOR, ARID1A, and SETD2 genes, each of which contributes to epigenetic regulation and interacts with or modifies the activity of histone deacetylases (HDAC). Based on these findings, the patient was treated with the HDAC inhibitor vorinostat as a single agent. The tumor responded transiently followed by subsequent disease progression. We also examined the efficacy of vorinostat in a patient-derived xenograft (PDX) model developed using tumor tissue obtained from the patient’s most recent tumor resection. The antitumor activity of vorinostat observed with the PDX model reflected clinical observations in that obvious areas of tumor necrosis were evident following exposure to vorinostat. Histologic sections of tumors harvested from PDX tumor-bearing mice treated with vorinostat demonstrated induction of necrosis by this agent. We propose that the evaluation of clinical efficacy in this type of preclinical model merits further evaluation to determine if PDX models predict tumor sensitivity to specific agents and/or combination therapies.

The genetic changes of Wilms tumour

“…With the recent identification of mutations in epigenetic remodelers in WT, and their interaction with histone deacetylases (HDAC), inhibitors of the latter might be another promising avenue. Transient response to single agent vorinostat, an HDAC inhibitor, was demonstrated in a child with refractory anaplastic embryonal rhabdomyosarcoma harboring mutations in BCOR and ARID1A (142). A further potential target is TP53, given the prevalence of TP53 mutants in both anaplastic and non anaplastic fatal tumours (41).…”

BCOR Involvement in Cancer

“…The embryonal RMS subtype typically affects younger children and is generally comprised of PAX-negative tumors. A rare subtype of RMS is anaplastic, where a single case was recently reported to carry a BCOR alteration, together with mutation in ARID1A , a member of the SWI/SNF family, and of SETD2 , a histone methyl-transferase [61]. Two studies [131,132] confirmed that BCOR mutations in RMS recur in about 7–8% of total cases, with an apparent major involvement in PAX-negative RMS, for which the percentage nears 10% of cases (Table 2).…”

Embryonal rhabdomyosarcoma of the biliary tree in a paediatric patient – A rare cause of obstructive jaundice

“…5 In the paediatric population, the two main histological subtypes of RMS are embryonal and alveolar, with embryonal RMS accounting for nearly 70% of all cases and usually affecting children less than 8 years of age. 1,6 Histopathologically, RMS is characterised by myoblastic differentiation and expression of skeletal muscle markers, such as desmin, myogenin and/or myoD1. 6…”

“…1,6 Histopathologically, RMS is characterised by myoblastic differentiation and expression of skeletal muscle markers, such as desmin, myogenin and/or myoD1. 6…”