SYNOVIAL SARCOMA - IMMUNOHISTOCHEMICAL EXPRESSION OF P-GLYCOPROTEIN AND GLUTATHIONE-S-TRANSFERASE-PI AND CLINICAL DRUG-RESISTANCE

Our purpose was to study the role of the expression of P-glycoprotein (Pgp) and glutatione S transferase-pi (GST-pi) in predicting the respo nse to chemotherapy, relapse-free interval, and survival of patients w ith synovial sarcoma (SS). Thirty-seven cases of primary SS, without r egional lymph node or distant metastases, were studied. There were 17 females and 20 males, ranging in age from 7 to 81 years (median, 31 ye ars) with tumors located in the lower extremity (n = 24) upper extremi ty (n = 5) and trunchus (n = 8). The cases were retrospectively studie d without knowledge of clinical course to compare the immunohistochemi cal expression of Pgp and GST-pi, flow cytometry parameters (ploidy an d % of cells in S+G2 phases), and PCNA and Ki-67 labeling of primary t umors before any therapy, with that observed in local recurrences and metastases after chemotherapy. The relationship of the aforementioned parameters with clinicopathological features (gender, age, and histobl ood group of the patients, size, location, histological subtype, TNM s tage, and clinical response to chemotherapy of the tumors) was also ev aluated. Results revealed that Pgp and GST-pi were expressed in 29.7% and 40.5% of the cases, respectively. In 48.6% of the tumors there was expression of at least one of the drug resistance markers. The marker s were coexpressed in 25.0% Of the tumors. The prevalence of Pgp expre ssion was lower, but not significantly, in stage I-II (17.6%) than in stage III (40.0%) tumors, and also in cases without clinical progressi on (16.7%), than in cases with (36.0%). No such differences were obser ved for GST-pi expression. Pgp and GST-pi expressions were significant ly associated with biphasic SS and were particularly noticeable in sol id/glandular areas of biphasic SS. The expression of the drug resistan ce markers was not significantly associated with gender, age, and hist o-blood group of the patients, dimension, location, and proliferative activity of the tumors; it was also not significantly related to relap se-free interval and survival of the patients. The expression of Pgp a nd GST-pi was not significantly associated either to response to chemo therapy or influenced by chemotherapy. We conclude that Pgp and GST-pi expressions are not good predictors response to of the chemotherapy i n patients with localized SS. Other drug resistance mechanisms may be active in SS.