In 58 human gastric cancers, the expression of P‐glycoprotein (P‐gp) was evaluated immunohistochemically and chemosensitivity was determined using the in vitro succinate dehydrogenase inhibition (SDI) test. Tumors which contained over 75% stained cells were scored as positive, and 14 of 58 cases (24%) were positive. There was no significant correlation between P‐gp expression and clinicopathologic features. The succinate dehydrogenase (SD) activity for each drug of P‐gp positive and negative tumors was as follows: 81.8 ± 15.2% vs. 66.3 ± 16.1% for Adriamycin (ADM), 75.5 ± 14.2% vs. 59.1 ± 17.6% for aclacinomycin A (ACR), 71.7 ± 15.0% vs. 61.1 ± 14.0% for mitomycin C (MMC), and 57.5 ± 18.4% vs. 47.0 ± 16.7% for cisplatin (CDDP). The increase in SD activity was evident in P‐gp positive tumors compared with negative ones in cases of ADM (P = 0.0044), ACR (P = 0.0105), and MMC (P = 0.0353). We suggested that P‐gp expression is closely related to chemosensitivities of human gastric cancers to anthracyclines. © 1994 Wiley‐Liss, Inc.
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