Antitumor activity of Lactobacillus casei
YIT 9018 (LC9018) was demonstrated by intralesional (i.l.) or intravenous (i.v.) administration into
tumor-bearing mice which were inoculated with
methylcholanthrene-induced
fibrosarcoma (Meth A) or Kirsten murine sarcoma virus-transformed
tumor (K234) cells. Its activity was significantly superior to the activity of two other species of lactobacilli but was nearly the same as that of Corynebacterium parvum or Mycobacterium bovis Bacille Calmette-Guérin (BCG). I.l. or i.v. administration of LC9018 into the
tumor bearers caused local transient swelling or hepatosplenomegaly but did not cause other pronounced lesions. There was no significant difference in the degree of hepatosplenomegaly in LC9018 and that in other
immunopotentiators. In mice whose
tumors had regressed as a result of administration of LC9018 or the other
immunopotentiators, the
phytohemagglutinin P (
PHA-P) response of the spleen cells was less than that of mice whose
tumors progressed, and approached the normal level. The
PHA-P response of popliteal lymph node cells proximal to the
tumor lesion was fairly low compared with the splenic
PHA-P response and there was no difference between the lymphocytes from mice whose
tumors had regressed or progressed. Adjuvant activity of LC9018 in inducing
tumor immunity was demonstrated by administering a mixture of LC9018 and Meth A cells to mice. This adjuvant activity was of the same efficiency as that of C. parvum and BCG. The presence of the antitumor activity of LC9018 in cell wall components was deduced from fact that removal of its cell wall by
endo-N-acetylmuramidase (M-1 enzyme) abolished the activity. The possible availability of LC9018 for
immunotherapy of
tumors is discussed.