Alterations of intracellular proteins during the process of heat stress-induced cell death of a human pancreatic cancer cell line, MIA PaCa-2, were investigated using two-dimensional gel electrophoresis (2-DE), agarose gel electrophoresis, and cell biology techniques. Incubation of MIA PaCa-2 at 45degreesC for 30 min decreased the cell growth rate and cell viability without causing chromosomal DNA fragmentation. Incubation at 51degreesC for 30 min suppressed cell growth and again led to death without DNA fragmentation. The cell death was associated with the loss of an intracellular protein Of A 17500 and pl 5.2 on 2-DE gel. This protein was determined to be eukaryotic initiation factor SA (elF-5A) by microsequencing of the N-terminal region of peptide fragments obtained by cyanogen bromide treatment of the protein blotted onto a polyvinylidene difluoride (PVDF) membrane. The sequences detected were QXSALRKNGFVVLKGRP and STSKTGXHGHAKVHLVGID, which were homologous with the sequence of eIF-5A from Gln 20 to Pro 36 and from Ser 43 to Asp 61, respectively. Furthermore, the result of sequencing suggested that the protein was an active form of hypusinated eIF-5A, because Lys 46 could be detected but not Lys 49, which is the site for hypusination. These results suggest that loss of the active form of eIF-5A is an important factor in the irreversible process of heat stress-induced death of MIA PaCa-2 cells.