Effect of Combined Intrapleural Administration of Lactobacillus casei (LC9018) and Adriamycin on Experimental Malignant Pleurisy in Mice

The combined effect of Lactobacillus casei YIT9018 (LC9018) and adriamycin (ADR) on malignant pleurisy was investigated using an experimental model in BALB/c mice in which Meth A fibrosarcoma cells were intrapleurally implanted. The control mice died from dyspnea due to pleural effusion, before significant growth of tumor nodules could be achieved in the thoracic cavity. Intrapleural (ipl) administration of LC9018 (20–200 μg/head) on days 1 and 5 reduced the effusion volume and induced pleural adhesions in a dose‐related manner. A statistically significant and reproducible prolongation of survival was observed at a dose of LC9018 200 μg/head: increase of lifespan (ILS) values of 15–39% were obtained. An ipl administration of ADR (2–4 mg/kg) on day 1 was also effective in prolonging survival without severe toxicity (ILS values of 100–122%). The combined use of ADR and LC9018 induced a high incidence of pleural adhesions, a delay in effusion accumulation, and an additive prolongation of lifespan (ILS values of 133–178%), compared with ADR monotherapy. In the combination therapy group, a marked and continuous ipl exudation of neutrophils, macrophages, and lymphocytes was observed with a significant decrease in pleural tumor cells. These findings suggest that ipl administration of LC9018 enhances the effect of ADR, probably through both host‐mediated tumoricidal activity and sclerosing effects on the pleura.