DAX-1 and ap2 beta Are Liable Markers of Translocation Positive Alveolar Rhabdomyosarcoma (ARMS)
Benedetta Di Venosa, Angelo Rosolen, Angelica Zin, Enzo Lalli, Vincenza Guzzardo, Rita Alaggio. Padua University, Padua, Italy; CNRS UMR, Valbonne, France
Background: ARMS are characterized by fusions of FOXO1 gene on chromosome 13 with PAX3 gene on chromosome 2 or PAX7 gene on chromosome 1 in 80% of case. Translocation positive ARMS have a distinctive biological signature on expression array. Among other genes ap2 beta and DAX-1 have been found to be over-expressed in translocation positive ARMS and a strong and diffuse nuclear immunostaining for ap2 beta appears to be predictive of presence of translocation.
Design: We studied a series of 45 ARMS (37 classic and 8 with areas of embryonal rhabdomyosarcoma-ERMS) and 25 ERMS to test the role of ap2 beta and DAX- 1 expression in predicting molecular status of ARMS.Immunostains for desmin, myogenin, ap2 beta and DAX-1 were performed. Ap2 beta and DAX-1 were considered positive when a strong and diffuse nuclear staining was found in the majority of cells.
Results: All tumors were desmin and myogenin positive, with staining for myogenin in more than 50% of cells in 78% of ARMS and 20% of ERMS respectively. Ap2 beta and DAX-1 pattern of expression are summarized in Table 1.
|Diagnosis (70 cases)||Ap2beta+/DAX1+||Ap2beta+/DAX-1-||Ap2beta-/DAX-1+||Ap2beta-/DAX-1-|
|ARMS t+ (32)||25||2||3||2|
|Arms t- (5)||0||1||3||1|
|MIXED (ARMS+ERMS, t-) (8)||2||0||4||2|