Correlation of a unique 220-kDa protein with vitamin D sensitivity in glioma cells

We have investigated the antitumor and apoptotic effects of 1,25-dihydroxyv itamin D-3 (VD3) in glioma cell lines and in primary cultures derived from surgical specimens from patients. Our results showed that certain glioma ce lls underwent apoptosis, whereas others were resistant. In an attempt to se arch for parameters that dictate VD3 sensitivity, we discovered a unique 22 0-kDa protein in glioma cells that were sensitive to VD3. This protein was not a classical vitamin D receptor (VDR), but was recognized by two differe nt anti-VDR monoclonal antibodies. Furthermore, the level of the 220-kDa pr otein was inversely correlated with the IC50 Of VD3 in these glioma cells. This 220-kDa protein was also present in frozen brain tumor samples, and th e level of expression appeared to correlate with their corresponding primar y cultures. Thus, our findings suggest that this 220-kDa protein may play a n important role in determining VD, sensitivity in malignant glioma. (C) 20 00 Elsevier Science Inc.