IMMUNOCYTOCHEMICAL OBSERVATION OF MULTIDRUG-RESISTANCE (MDR) P170 GLYCOPROTEIN EXPRESSION IN HUMAN OSTEOSARCOMA CELLS - THE CLINICAL-SIGNIFICANCE OF MDR PROTEIN OVEREXPRESSION

Resistance to sever al cytotoxic agents (MultiDrug Resistance MDR), in cluding anthracyclines, vinca alkaloids and epipodophylline derivative s can occur in human osteosarcoma (OS) cells, detected by the overexpr ession of a 170 kD glycoprotein (p170), as a result of increased expre ssion of the MDR gene (mdr1). The p170 glycoprotein in no,mal cells is a membrane transport system protein and its quantitative increase res ults in ina eased drug efflux and decreased intracellular drug concent ration. Normal renal epithelial cells express p170 as a function of th eir secretory duties therefore this human tissue was used as a positiv e tissue control in our immunocytochemical study. This partially retro spective immunocytochemical study was carried out on routine, 10% neut ral formalin fixed, decalcified, paraffin embedded tissue sections of 43 OSs, treated between 1981 and 1993 at the Orthopaedic Hospital of L os Angeles. The immunoperoxidase antigen detection protocol, submitted by Hsu et al (1981) was employed. The search for p170 was carried out with three newly developed monoclonal antibodies (MoABs) (JSB-1, C-21 9 and C-494, from Signet Laboratories, Dedham, MA 02026). The initial expression of MDR was not detectable in seven OSs. 36/43 OSs expressed p170 on/in their cells. Heterogenous cellular microenvironment and va rious grades of differentiation features were also determined in the e xamined OSs. In 17/43 OS cases presence of intensive staining (probabl y overexpression) of p170 protein was registered. The 43 OSs exhibited different staining patterns with each MoAB. MoAB JSB-1 reacted with a transmembranic antigen epitope. The long incubation time with C-219 r esulted in heterogeneous cytoplasmic staining MoAB C-494 also produced an intensive staining mainly localized on the cell membrane of the OS cells. These statistically significant immunocytochemical , results s uggest a direct correlation between the quantitative presence of p170 glycoprotein in human OS cells and the efficacy of the employed chemot herapy. Future observations employing the in situ hybridization techni que will allow the quantitative measurement of the primary or secondar y presence of MDR glycoprotein in human OS cells.