Analysis of Antitumor Properties of Effector Cells Stimulated with a Cell Wall Preparation (WPG) of Bifidobacterium Infantis

Abstract

Intestinal Bifidobacterium species are thought to be beneficial in animal and human intestines. We studied the mechanisms of Bifidobacteria in antitumor activity using a cell wall preparation (WPG) of B. infantis (Cancer Res., 45, 1300, (1985)). WPG enhanced the in vitro antitumor activities of mouse peritoneal exudate cells elicited with proteose-peptone (P-PEC) and thioglycollate broth (TG-PEC), determined by cytostatic ([3H] thymidine uptake inhibition) and cytolytic ([3H] uridine release) assays. Tumor necrosis factor-α (TNF-α) and reactive nitrogen intermediates (RNI) play a role in such augmented cytotoxicity, because anti-TNF-α antibody almost completely blocked the increased cytolytic activity of P-PEC in the presence of WPG. Moreover, WPG induced RNI in the supernatant of TG-PEC in a dose-dependent manner. The mRNA expression of several cytokines (IL-1β, IL-6, IL-10, IFN-α and TNF-α) was induced in BALB/c mouse peritoneal cells 3 h after an intraperitoneal injection of WPG (3 h WPG-PEC). However, this expression disappeared from 24 h WPG-PEC, except for that of IFN-α. IFN-γ was not induced. Kinetic studies of the tumor neutralizing activities of the WPG-PECs by means of the in vivo Winn assay revealed that the activity emerged at 1.5 h, became maximal at 3 h and disappeared at 24 h. These results indicated that Bifidobacterial WPG is a Biological Response Modifier (BRM) with characteristics similar to those of other bacterial BRMs. © 1995, The Pharmaceutical Society of Japan. All rights reserved.