Differential expression of β1, β3 and β4 integrins in sarcomas of the small, round, blue cell category

Abstract

Integrins are a large and complex family of membrane spanning αβ heterodimeric cell surface glycoproteins mediating cell/cell and cell/matrix interactions. Small, round, blue cell sarcomas (SRBCS) are a group of poorly differentiated tumours of various and in part uncertain histogenesis displaying similar cytomorphology. Among them are rhabdomyosarcomas (RMS), ganglioneuroblastomas [(G)NB], primitive peripheral neuroectodermal tumours (pPNET) and Ewing's sarcomas (ES). Thirty-two SRBCS were studied immunohistochemically for the distribution of β1, β3 and β4 integrins in situ. We found complex and to some extent differential patterns of β1, β3 and β4 integrin subunit expression in different types of SRBCS: all of the sarcomas studied were consistently β1⁺, β4⁻, α2⁻. Four of nine RMS were completely negative for all other integrin subunits studied while one RMS was α5⁺ throughout and three RMS were focally α5⁺. Three RMS expressed the α6 and αv chains. In contrast to RMS, pPNET and ES, all of which were α1⁻, α3⁻, (G)NB were α3⁺ and frequently co-expressed α1. The eight pPNET and seven ES studied showed a similarily restricted integrin profile that was limited to the expression of β1 and α5 in nearly all cases. In summary, RMS were β1⁺, α1⁻, α3⁻ and heterogeneously expressed α5 and α6. (G)NB were generally β1⁺, α1⁺, α3⁺, α5⁻, α6⁻. pPNET and ES were β1⁺, α1⁻, α3⁻, α5⁺, α6⁻. The data illustrate a complex expression pattern of various integrins in SRBCS, a differential expression pattern of some of the integrin subunits among different types of SRBCS and almost identical integrin profiles in pPNET and ES.