Effects of Proteus mirabilis on tumor growth of rats
Bay, M.L.; Comba, J.O.; Amerio, N.; Morini, J.C.
Medicina 42(5): 507-512
1982
ISSN/ISBN: 0025-7680 PMID: 6763128 Document Number: 5236
The effect of Proteus mirabilis (Pm) on a rat transplantable sarcoma (S-E 100) was studied in 3 different models: 1) subcutaneous (sc) injection of Pm together with the tumoral cell suspension; 2) sc injection of Pm in the contralateral flank (fcl); 3) intraperitoneal (ip) injection of Pm 7 days before tumor challenge. These studies were carried out in rats without any previous manipulation or in animals in whicha glass cilinder (GC) was implanted sc 2 days before the in situ tumor challenge. Such procedure is known to enhance tumor growth. Two types of measurements were used to evaluate tumor growth at different intervals after challenge: a) size of the tumor, estimated as the area of tumor mass, and b) growing rate, estimated as the slope of the regression line. In model one, the growth rate was similar to that of the controls, but the size of the tumor was significantly smaller in the interval 10 to 15 days (F,=8.14; p<0.01) as well as between 15 to 25 days (F3=11.87; p<0.01). In all cases, rats hearing a glass cylinder had tumor areas significantly larger than that of the corresponding controls (i.e: 1.5-25 clays, VII: y 659.27±64.2; n=26; 2155.37 66.38; n=30; p<0.001; Figs. 1 and 2). In the group of animals with GC + Pm (Fig 2 e) the rate of tumor growth was reduced (b=60.67) when compared with that of their controls (b=174.2) (F,=27.58; p<0.001) as well as the tumor area. The kinetics of tumor growth in these groups was modified after day 15, hut the size of the tumor remained smaller (F,=35.6; p<0.01). The inoculation of Pm on the fcl did not modify the evolution of the tumor (Figs. 3 and 4). On the contrary, the inoculation of Pm 7 days before 11. tumor challenge (Fig. 5) showed tumors significantly larger than that of the controls, on the interval 10 to 1.5 days (F, 17.29; p<0.01) as well as in the period 15-25 days (F,=21.03; p<0.01). This effect was not seen in rats bearing a glass cylinder (Fig. 6) where tumor growth was not affected. The observed protective effect of Pm (model 1) could be the consequence of the in situ non specific activation of macrophages and/or NK cells. The enhancing effect of Pm on tumor growth (model 3) could be due to modulatory factors related to the immune response induced by the bacteria, injected 7 days before, which could have inhibited the antitumoral reaction.
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