Detection of FOXO1 (FKHR) gene break-apart by fluorescence in situ hybridization in formalin-fixed, paraffin-embedded alveolar rhabdomyosarcomas and its clinicopathologic correlation.
Chromosomal translocations of t(2;13)(q35;q14) and t(1;13)(p36;q14), resulting in PAX3-FOXO1 (FKHR) and PAX7-FOXO1 (FKHR) gene fusions, have been found to be specific molecular markers for alveolar rhabdomyosarcomas (ARMS) and can be identified in approximately 80% cases. As the prognosis of ARMS is worse than that of embryonal rhabdomyosarcomas (ERMS), it is important to accurately distinguish between these 2 subtypes. This distinction may be difficult on the basis of morphology alone. To detect the genetic alterations, reverse transcriptase polymerase chain reaction (RT-PCR) or dual-color dual-fusion fluorescence in situ hybridization (FISH) have been used in most studies so far. In this study, we used FOXO1 (FKHR) gene break-apart FISH probe, which can detect both of the translocations involving the FOXO1 gene, and tested 20 cases of rhabdomyosarcoma (RMS) including 6 cases of ARMS, 8 ERMS, 1 pleomorphic type, 5 not otherwise specified (RMS-NOS), and 10 non-RMS sarcomas. A home-brew RT-PCR that could detect both PAX3-FOXO1 and PAX7-FOXO1 was also performed. Four pathologists independently reviewed all RMS and a consensus diagnosis was also reached in discrepant cases. Histologic and molecular findings were correlated with clinical outcomes with an average of a 49-month follow-up. FOXO1 break-apart by FISH was positive in 4 of 6 (66%) ARMS and 2 of 5 (40%) RMS-NOS cases. All other cases, including all ERMS, were negative. RT-PCR assay confirmed all FISH results. While 2 of 6 (33%) RMS patients with a FOXO1 break-apart died of the disease, there were no deaths among the patients with negative result. The FOXO1 gene break-apart FISH probe is a simple and accurate tool to detect the translocations associated with ARMS. As characteristic genetic alterations of ARMS can be identified in 40% of RMS-NOS cases in our study, the FISH assay would provide an additional useful tool in the diagnosis and prognosis of ARMS, and an alternative to RT-PCR.
Mehra
Shveta
S
Department of Pathology, SUNY Upstate Medical University, Syracuse, NY, USA.
de la Roza
Gustavo
G
Tull
Jamie
J
Shrimpton
Antony
A
Valente
Alfredo
A
Zhang
Shengle
S
D000293:Adolescent; D000328:Adult; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D019457:Chromosome Breakage; D002878:Chromosomes, Human, Pair 1; D002882:Chromosomes, Human, Pair 13; D002889:Chromosomes, Human, Pair 2; D005260:Female; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000235:genetics*; D005557:Formaldehyde / Q000494:pharmacology*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D019042:Muscle Neoplasms / Q000175:diagnosis* / Q000235:genetics*; D015514:Oncogene Proteins, Fusion / Q000235:genetics; D016612:Paraffin Embedding; D011379:Prognosis; D018232:Rhabdomyosarcoma, Alveolar / Q000175:diagnosis* / Q000235:genetics*; D014178:Translocation, Genetic; D014407:Tumor Cells, Cultured
C085126:FOXO1 protein, human; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D015514:Oncogene Proteins, Fusion; D005557:Formaldehyde