K-ras point mutation occurs in >80% of pancreatic cancer. We reported previously that the transduction of an antisense K-ras RNA expression vector suppressed the growth of pancreatic cancer cells with K-ras point mutations in vitro and in vivo. The RNA differential display method (DD) was used to compare the mRNA expression profile of the pancreatic cancer cell line AsPC-1 and that of the antisense K-ras-transduced, growth-retarded AsPC-1 cells. cDNA fragments were isolated from 20 bands on the DD gel, and their differential expression between the two cell lines was confirmed. A sequence analysis revealed that all of the 11 clones up-regulated in the antisense-transduced cells were mitochondrial genes. The other nine cDNA clones that were down-regulated in the antisense-transduced AsPC-1 cells included an oncogene PTI-1 (prostate tumor inducing gene-1), matrix metalloproteinase (MMP)-7, the β3 chain of laminin-5, lysosome-associated membrane protein-2, the H chain of apoferritin, ribosomal protein S6, proteasome subunit XAPC7, and two cDNA fragments with no homology to the GenBank database. In addition to the AsPC-1 cells, reverse transcription-PCR analysis on surgical specimens of pancreatic cancer revealed that the PTI-1 and MMP-7 genes were overexpressed in three and four cases, respectively, of five cases examined. This method offers a unique opportunity to identify a set of genes that may be modulated by K-ras activation, at least in a subset of the pancreatic cancer. The information on such genes may facilitate our understanding of the spectrum of the functional genetic changes in pancreatic cancer.