Effects of ultrasound on apoptosis induced by anti-CD20 antibody in CD20-positive B lymphoma cells.
OBJECTIVE
The present study was conducted to examine the thermal and non-thermal effects of ultrasound on apoptosis induced by anti-CD20 monoclonal antibody (rituximab).


METHODS
SU-DHL-4 cells, a CD20-positive cell line derived from B cell lymphomas with a BCL2 gene rearrangement, were exposed to continuous 1 MHz ultrasound for therapeutic use under an air- or CO(2)-saturated condition to control cavitation. Early apoptosis (EA) and secondary necrosis (SN) were examined by flow cytometry. Cavitation was determined by detecting the hydroxyl radicals derived from pyrolysis of water molecules using electron paramagnetic resonance-spin trapping. To assess thermal effects, cells were treated in a temperature-controlled water bath.


RESULTS
There was a significant additive increase in EA and EA+SN observed in cells treated with rituximab combined with heat at 42 degrees C or non-thermal ultrasound at 0.5 W/cm(2) under an air-saturated condition, where heat or ultrasound induced some cell death. A significant synergistic increase in EA and EA+SN was observed in cells treated with rituximab and ultrasound at 2.5 W/cm(2) under CO(2)-saturated conditions, where inertial cavitations were completely suppressed. No enhancement was observed at a temperature less than 40 degrees C or ultrasound at 0.5 W/cm(2) under CO(2)-saturated conditions.


CONCLUSIONS
These results suggest that the immuno-therapeutic application of ultrasound at relatively high-intensities combined with rituximab thus produces synergistic effects under conditions where the non-thermal and non-cavitational effects are predominant.
Danno
Daisuke
D
Department of General Medicine, Nara Medical University School of Medicine, Kashihara, Nara, Japan. Electronic address: ddanno@naramed-u.ac.jp.
Kanno
Masatoshi
M
Department of General Medicine, Nara Medical University School of Medicine, Kashihara, Nara, Japan.
Fujimoto
Shinichi
S
Department of General Medicine, Nara Medical University School of Medicine, Kashihara, Nara, Japan.
Feril
Loreto B
LB
Department of Anatomy, Fukuoka University School of Medicine, Fukuoka, Japan.
Kondo
Takashi
T
Department of Radiological Sciences, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
Nakamura
Shinobu
S
Department of General Medicine, Nara Medical University School of Medicine, Kashihara, Nara, Japan.
D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000276:immunology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006358:Hot Temperature; D006801:Humans; D016393:Lymphoma, B-Cell / Q000276:immunology / Q000473:pathology*; D000069283:Rituximab; D014465:Ultrasonics
D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D000970:Antineoplastic Agents; D005609:Free Radicals; D000069283:Rituximab