Human astrocytomas co-expressing Fas and Fas ligand also produce TGFbeta2 and Bcl-2.
Human astrocytomas frequently co-express Fas (APO-1/CD95) and Fas ligand (FasL), yet do not appear to be overly susceptible to suicidal, fratricidal and immune-mediated elimination. This suggests that these gliomas have acquired mechanisms to prevent Fas-mediated apoptosis from occurring. Candidates for such a role include transforming growth factor-beta2 (TGFbeta2) and B-cell lymphoma/leukemia-2 (Bcl-2). TGFbeta2 effectively functions by hiding tumor cells from the immune system. This may potentially prevent the delivery of FasL from cytolytic T cells to Fas bearing astrocytomas. Bcl-2 works by rendering gliomas resistant to Fas-mediated apoptosis. Using immunohistochemistry, we analyzed seventy-six human astrocytomas (11 World Health Organization (WHO) grade I, 17 grade II, 17 grade III, and 31 grade IV) for the expression of Fas, FasL, TGFbeta2 and Bcl-2 in vivo. Positive immunoreactivity was found to significantly increase with increasing tumor grade for Fas (p < 0.0002), FasL (p < 0.0001), TGFbeta2 (p < 0.001) and Bcl-2 (p < 0.01). In addition, Fas/FasL co-expression, a counter-intuitive combination of factors in regards to glioma survival, also increased with WHO grade. Forty-five of 76 (59%) astrocytomas co-expressed Fas and FasL. Of those co-expressing Fas and FasL, 44 of 45 (98%) produced TGFbeta2, and 26 of 45 (58%) expressed Bcl-2. We found a significant positive correlation between Fas/FasL co-expression and TGFbeta2 (p < 0.002) and Bcl-2 (p < 0.005) production. We conclude that Fas and FasL are frequently co-expressed in human astrocytomas and these tumors are likely to produce other immunosuppressive and antiapoptotic factors such as TGFbeta2 and Bcl-2.
Frankel
B
B
Department of Neurosurgery, SUNY Health Science Center at Syracuse, NY 13210, USA. frankelb@vax.cs.hscsyr.edu
Longo
S L
SL
Ryken
T C
TC
D001254:Astrocytoma / Q000378:metabolism* / Q000473:pathology; D053222:Fas Ligand Protein; D005909:Glioblastoma / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D019014:fas Receptor / Q000378:metabolism*
C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016212:Transforming Growth Factor beta; D019014:fas Receptor