IMMUNOHISTOCHEMICAL DETECTION OF MULTIDRUG RESISTANCE ASSOCIATED P-GLYCOPROTEIN IN STROMAL CELLS OF MALIGNANT-LYMPHOMAS

We examined the distribution of the P-glycoprotein by immunohistochemistry in 25 malignant lymphomas (15 CHOP-derived regimen resistant non-Hodgkin's lymphomas and 10 Hodgkin's diseases). The study was performed on both cryostat and ModAMeX sections; the latter method preserves fixation-sensitive antigens and allows a more precise morphologic identification of neoplastic and non-neoplastic cell populations in contrast to cryostat sections. In both non-Hodgkin's lymphomas and Hodgkin's diseases, cells that were stained on cryostat sections were identified as macrophages and endothelial cells and not neoplastic lymphoid cells, by the ModAMeX technique. These findings suggest that the quantitative assessment of the multidrug resistance gene RNA by Northern blotting performed on fresh homogenates may overestimate the RNA content of neoplastic cells in a number of lymphoid tumors. In addition, the mechanism of chemoresistance in non-Hodgin's lymphomas is less likely to be associated with the P-glycoprotein expression.