Chemically induced rhabdomyosarcomas in rats - Ultrastructural, immunohistochemical, biochemical features and expression of α-actin isoforms


A series of 14 primary and two metastatic rat rhabdomyosarcomas (RMS) induced with nickel sulfide was studied by light microscopy, transmission electron microscopy, indirect immuno-fluorescence, avidin-biotin-peroxidase immuno-histochemistry and two-dimensional gel electrophoresis. Monoclonal or affinity-purified polyclonal antibodies were used for the immunohistochemical demonstration of vimentin, desmin, a-smooth muscle (α-sm) actin and α-sarcomeric (α-sr) actin. By histological and ultrastructural studies, four categories of RMS were diagnosed on the basis of the neoplastic cell types. These were: (1) well-differentiated RMS (n = 2), (2) pleomorphic RMS (n = 8), (3) embryonal RMS (n = 4), and (4) embryonal myosarcomas (n = 2). Immuno-histochemically, all these neoplasms expressed desmin and α-sr actin, reflecting their rhabdomyoblastic origin. Two dimensional gel electrophoresis performed on five neoplasms demonstrated α, β and γ actins spots in all cases. This study demonstrates that the α-sr actin antibody represents a good marker for rhabdomyoblastic differentiation is useful in the diagnosis of RMS since it was present in all morphologically confirmed RMS and in two ultrastructurally undifferentiated sarcomas positive for desmin. Neoplastic cells positive for α-sm actin were noted in 11 confirmed RMS. Double indirect immunofluorescence showed that all α-sm and α-sr positive cells also contained desmin. Co-expression of α-sr and α-sm actins was studied in serial sections of formalinfixed, paraffin-embedded tumor tissue. Both α-sm and α-sr actins were localized in some rhabdomyoblasts. This study confirms our previous observations in human tumors and shows, for the first time, that α-sr and α-sm actins can be present in the same neoplastic cell in vivo. © 1988 Springer-Verlag.

Publication Title

Virchows Archiv B