Background: Drug resistance remains a major problem in gastric carcinomas. To evaluate the mechanisms involved in this resistance, the authors determined the expression of the MDR1 gene, a multidrug resistance gene, in primary gastric carcinomas.
Methods: MDR1 RNA levels of gastric carcinoma specimens (n = 22) were determined by slot blot analysis. An MDR1 cDNA (probe 5A) was used for the hybridization.
Results: MDR1 RNA was detected in 41% of the gastric carcinomas, with high levels in 18% of the specimens. No expression of the MDR3 gene was observed in these tumors. MDR1 gene expression was independent of patient age, tumor localization, and lymph node involvement. However, MDR1 RNA expression was less frequent in locally advanced tumors and was absent in the primary tumors of all six patients who had distant metastases.
Conclusions: The data indicate that multidrug-resistant cells are present in primary gastric carcinomas and suggest that multidrug resistance might contribute to the clinical drug resistance of these tumors.