Antimetastatic effect of Lactobacillus casei YIT9018 (LC 9018) on a highly metastatic variant of B16 melanoma in C57BL/6J mice

Summary The effect of Lactobacillus casei YIT9018 (LC 9018) on a highly metastatic variant of B16 melanoma, B16-BL6, was determined in C57BL/6 mice. Intralesional (i.l.) injection of LC 9018 inhibited tumor growth and prolonged the survival after s.c. inoculation of B16-BL6 into C57BL/6 mice. Injection of LC 9018 i.v. protected the mice against pulmonary metastasis after i.v. inoculation of B16-BL6. Injection of LC 9018 i.l. before surgical excision of the primary tumor inhibited axillary lymph node metastasis and i.v. injection of LC 9018 after surgical excision of the primary tumor inhibited both axillary lymph node and lung metastases. On the other hand, the combination of i.l. and i.v. injections of LC 9018 markedly inhibited both lymph node and lung metastases. Natural killer cell activity of axillary lymph node cells was augmented by the injection of LC 9018 into a front footpad, while the cytolytic activity of axillary lymph node cells was significantly enhanced. However, the cytolytic activity was diminished by depleting whole lymph node cells of the plastic adherent cells. Furthermore, alveolar macrophage-mediated cytotoxic activity was augmented by the i.v. injection of LC 9018.