Glutathione S-transferase pi immunostaining of cisplatin-resistant ovariancancer cells in ascites

OBJECTIVE: To clarify immunohistochemically the correlation between glutath ione S-transferase pi (GST pi) expression of surgically resected specimens and clinical response in ovarian cancer and to evaluate ascites cytology us ing GST pi staining. STUDY DESIGN: Eighty-seven patients with ovarian cancer underwent initial d ebulking surgery and received cisplatin-based chemotherapy after surgery. I mmunostaining for GST pi was performed on formalin-fixed sections of the pa tients' tumors. The cytologic slides of 24 RESULTS: Of 87 surgically resected specimens, 55 (63.2%) were GST pi positi ve. Twenty-five of 28 patients (89.3%) who showed no response to chemothera py had GST pi-positive tumor cells. The predictive value of positive GST pi staining for drug resistance was 75.8% (25/33). Of 18 cases that were GST pi positive in surgically resected specimens, 17 were positive in ascites c ytology. Five cases were negative in both resected specimens and ascites cy tology. There teas a significant correlation in the GST pi labelling index between resected specimen and ascites cytology from the same case; the corr elation coefficient was .701 and P value <.001. CONCLUSION: Overexpression of GST pi is related to resistance to cisplatin, and GST pi staining of ascites cytology can be used in pretherapeutic asse ssment of patients with ovarian cancer.