Expression of ICAD‐L and ICAD‐S in Human Brain Tumor and Its Cleavage upon Activation of Apoptosis by Anti‐Fas Antibody

ICAD/DFF is a downstream molecule of caspases, participating in nuclear DNA fragmentation during apoptosis. ICAD/DFF binds CAD/DFF40 and inhibits its DNase activity. ICAD/DFF has two alternative isoforms, long isoform (ICAD‐L/DFF45) and short isoform (ICAD‐S/DFF35). We have studied the presence and functional status of ICAD/DFF in human glioma cell lines. All cell lines tested expressed both ICAD‐L and ICAD‐S. When the cultured glioma cells were exposed to anti‐Fas antibody, these isoforms were degraded prior to the fragmentation of the nuclear DNA, indicating that the ICAD/DFF expressed in cultured glioma cells was potentially functional. In primary brain tumors and normal brain tissues, there was a difference in the expression level between ICAD‐L and ICAD‐S. In glioblastomas, ICAD‐S was more abundant than ICAD‐L. In contrast, ICAD‐L was more abundant than ICAD‐S in medulloblastomas. The present findings suggest that primary brain tumors and normal brain constitutively express ICAD/DFF, and that there is a difference between the expression levels of ICAD‐L and ICAD‐S.