From the investigated 17 samples, seven (41%) showed homozygous mutation of MYOD1, indicating a critical role in this rare subtype of adult spindle cell RMS, while no mutations were found in any of the other genes involved in myogenic differentiation.
We investigated 30 cases of MYOD1-mutant rhabdomyosarcoma (12 previously reported and 18 newly diagnosed) with an age range of 2-94 years, including 15 children.
We have performed the RT-PCR assay to analyze RMS for the presence of expression of MyoD1 gene and for the presence of chimeric transcripts PAX3/FKHR or PAX7/FKHR.
Furthermore, the regulatory-gene analyses indicated that these 2 sublines represented 2 distinct differentiation stages of myoblasts, and that MyoD1 and myogenin could serve as the lineage marker and the differentiation marker, respectively, of human rhabdomyosarcoma.
Clinically, a striking correlation was found between MYOD1 mutation and the clinical outcomes available for 15 of 21 cases: 5 of 7 patients with spindle cell and sclerosing rhabdomyosarcomas, harboring MYOD1 mutation, were alive-with-disease and 2 of 8 patients with spindle cell and sclerosing rhabdomyosarcomas, with mutant MYOD1, were free-of-disease.
The expanding morphological and genetic spectrum of MYOD1-mutant spindle cell/sclerosing rhabdomyosarcomas: a clinicopathological and molecular comparison of mutated and non-mutated cases.
A clinicopathologic study of head and neck rhabdomyosarcomas showing FOXO1 fusion-positive alveolar and MYOD1-mutant sclerosing are associated with unfavorable outcome.
We detected the MyoD1 transcript in normal skeletal muscle and in almost all RMSs, whereas no expression was found in non-RMS samples or in normal hematopoietic tissues.
Amongst the transcripts differentially expressed in the RD cells, MYOD and MYOG (2 fold, p<0.05), and six MYOD downstream targets were up-regulated in RD but not C2C12 cells.
Our data suggest that the methylation status of the MyoD1 upstream CpG sites may be related to rhabdomyosarcoma tumorigenesis and may have valuable implications for its differential diagnosis.
Our data support unappreciated and dominant oncogenic roles for MYF5 and MYOD convergence on common transcriptional targets to regulate human RMS growth.
We report here that MyoD1 mRNA is not specific for RMS, but can be amplified from ex vivo samples of many other childhood tumors and some normal tissues.
Transfection of the mouse MyoD1 gene into the human rhabdomyosarcoma cell line RD increased the ability of the tumor cells to differentiate into multinucleated myotubes and enhanced myosin heavy-chain gene expression but did not decrease tumorigenicity in nude mice.
High MyoD1 expression (≥51% tumor cells) was seen in more cases of pure sclerosing, combined with spindle cell/sclerosing RMSs (10/10, 100%), as compared to the other subtypes (91/141, 67.4%) (p = 0.032).
Rhabdomyosarcomas are malignancies associated with a rhabdomyoblastic phenotype which can be demonstrated morphologically or by immunohistochemistry for MYOD1 and myogenin.
Further, these analyses identify two syntenic clusters of muscle-associated genes on the short arm of human chromosome 11, one in the region of rhabdomyosarcoma locus that includes IGF2 and TH and the second the tightly linked MYOD1 and LDHA loci, which have been evolutionarily conserved in homologous regions of both the mouse and the rat genomes.
Although the focal alveolar architecture and the primitive cytologic appearance of these hyalinizing RMS suggest a relationship with ARMS, the presence of abundant strap cells in one case, the predominant expression of MyoD1 rather than myogenin, and the absence of ARMS-associated fusions genes point more strongly toward a variant of ERMS.
Cases were wild type for MYOD1 and no other mutations or rearrangements characteristic of a known subtype of rhabdomyoma or rhabdomyosarcoma were identified.
Polyclonal desmin and muscle-specific actin were variably immunoreactive in UESL and RMS; however, myogenin and myogenic regulatory protein D1 (MyoD1) were uniformly negative in UESL and routinely positive in the majority of biliary tract RMS.