The significance of arginase I administration on the survival of mice bearing NS-1 myeloma cells.
BACKGROUND
Arginase I blood levels elevate in cancerous patients and correlate with cancer stages and poor prognosis. Since arginase is capable of enhancing cell growth, it is unclear whether its ominous effect on cancer progression is through the inhibition of immunity or through direct enhancement of cancer cell growth. We tried to clarify this question.


METHODS
NS-1 mouse myeloma cells were inoculated intraperitoneally (i.p.) into mice. Purified mouse arginase I was injected daily either intravenously (i.v.) or i.p. for 6 d. A tumor-only control group received i.p. tumor cells without arginase. The survival rates of all mice were recorded.


RESULTS
Survival rates were significantly lower in the i.v. group than in the i.p. group (P=0.017) or in the tumor-only control group (P=0.034). As spleen is readily exposed to i.v. arginase, its natural killer cells were studied and were found to have been significantly suppressed by arginase in vitro (P<0.005).


CONCLUSIONS
Our results indicate that the direct inhibition of the immune system by i.v. arginase is more significant in shortening the survival of tumor-bearing mice than localized (i.p.) arginase promotion of tumor cell growth. Thus, an elevation of arginase in a patient's blood is very harmful to the host immune system, e.g. splenic natural killer cells.
Wang
Soo-Ray
SR
Department of Internal Medicine, Chung Shan Medical University and Chung Shan Medical University Hospital, Taichung, Taiwan. cshy737@csh.org.tw
Hou
Stephen
S
Wang
Amy
A
Chang
Yu-Jun
YJ
Liu
Cheng-Tzu
CT
Tsay
Gregory J
GJ
Wei
Chung-Cheng
CC
D000818:Animals; D001119:Arginase / Q000008:administration & dosage / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D007274:Injections, Intraperitoneal; D007275:Injections, Intravenous; D007694:Killer Cells, Natural / Q000187:drug effects / Q000473:pathology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009101:Multiple Myeloma / Q000097:blood / Q000401:mortality* / Q000473:pathology; D015996:Survival Rate
D001119:Arginase