BACKGROUNDThe incidence and mortality rate of pancreatic cancer have increased dramatically in China over recent decades. Focused ultrasound (FU) has been somewhat successful in treating pancreatic cancer. The purpose of this study was to investigate apoptosis in pancreatic cancer cells induced by FU.

METHODSSuspension of human pancreatic carcinoma cell line PaTu 8988t was radiated by FU, using five doses with different radiation parameters and patterns, including one blank control. Temperature increase of the cell suspension was monitored. Cell apoptosis and death after FU radiation was observed using fluorescence microscopy and was tested by flow cytometer at 3, 6, 12, 24, and 48 hours after ultrasound radiation.

RESULTSThe maximum cell suspension temperatures following five radiation doses were 28°C, (42.20 ± 2.17)°C, (50.80 ± 0.84)°C, (55.80 ± 2.17)°C, and (65.20 ± 3.11)°C; differences between the doses were statistically significant (P < 0.05). The apoptosis rate peaked at 24 hours after radiation, at (0.56 ± 0.15)%, (1.28 ± 0.16)%, (1.84 ± 0.29)%, (5.74 ± 1.15)%, and (2.00 ± 0.84)% for the five doses; differences between the doses were statistically significant (P < 0.05). Between doses 1 - 4, cell apoptosis rates increased as the T(max) increased. In dose 5, as the T(max) was above 60°C, the apoptosis rate decreased.

CONCLUSIONSub-threshold thermal exposures of FU radiation with a continuous radiation pattern could result in higher percentage of apoptosed cells.