|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1997 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1996 : ¥1,100,000 (Direct Cost : ¥1,100,000)
1) We examined the relationship between the expression of a multidrug resistance-associated protein (MRP) and the biologic factors regarding invasion and metastasis of human gastric cancer. In 75 human gastric cancers, the overexpression of MRP was immunohistochemically investigated and that of mRNA was also detected using reverse transcription PCR (RT-PCR) , and sensitivity to the anticancer agents, cisplatin (CDDP) , doxorubicin (DXR) , etoposide (VP-16) and mitomycin C (MMC) was examined using the MTT assay. The relation between MRP expression and development, invasion, and metastasis of cancer was analyzed and overexpression of the tumor suppressor gene p53 was also investigated, immunohistochemically. Immunohistochemically detected MRP positive tumors were noted in 34 of 75 excised tumors (45%) , which was confirmed by by RT-PCR.There was no significant relation between MRP expression and clinicopathologic features or prognosis. Positive p53 staining was evident in 16 of 34 MRP po
sitive tumors (47%) and 18 of 41 negative ones (44%) , and there was no significant correlation between MRP and abnormal p53 exprerssion. The MTT assay showed that MRP positive gastric cancer tissues were less sensitive to CDDP,DXR,MMC compared to MRP negative noes, and the same tendency was seen with VP-16. Thus MRP expression telates to the chemosensitivity of tumor cells against some anticancer drugs and is independent of known factors related to development, invasion and metastasis of human gastric cancer.
2) To search of a possible relationship between expression of MRP and sensitivity to anti-cancer agents in gastric cancer, 4 gastric cancer cell lines, 43 human gastric carcinomas and 17 adjacent normal gastric tissue samples were analyzed. Expression of MRP mRNA was exaluated using reverse transcription PCR (RT-PCR) and Southern hybridization. Sensitivity of the test samples to the anti-cancer drugs cisplatin (CDDP) , doxorubicin (DXR) , and etoposide (VP-16) was examined using MTT assay. Immunohistochemical staining with the use of the MRP antibody (MRPr1) was done to confirm the findings regarding the expression of mRNA levels. The MRP expression evaluated with RT-PCR and Southern hybridization as well as with immunohistochemical staining revealed that 23 of 43 gastric-cancer tissue (53.5%), 15 of 17 normal gastric tissues (88%) and 3 of 4 gastric-cancer cell lines (75%) were positive. The MTT assay showed that DXR was significantly morre sinsitive (p<0.01) in gastric carcinoma tissues lacking MRP expression than in those with positive expression. The same tendency was seen with the other agents used. Of the cell lines on which showed no MRP expression also had a higher sensitivity to CDDP,DXR and VP-16 than the other positive cases. These results show that MRP expression in involved in MDR of human gastric cancer and is inversely related to the chemosensitivity of tumor cells against some anticanser drugs. Less