Each Mycobacterium Requires a Specific Culture Medium Composition for Triggering an Optimized Immunomodulatory and Antitumoral Effect

Marina Luquin,Víctor Campo-Pérez,Esther Julián,Alejandro Sánchez-Chardi,Sandra Guallar-Garrido

doi:10.3390/microorganisms8050734

Abstract

Mycobacterium bovis bacillus Calmette-Guérin (BCG) remains the first treatment option for non-muscle-invasive bladder cancer (BC) patients. In research laboratories, M. bovis BCG is mainly grown in commercially available media supplemented with animal-derived agents that favor its growth, while biomass production for patient treatment is performed in Sauton medium which lacks animal-derived components. However, there is not a standardized formulation of Sauton medium, which could affect mycobacterial characteristics. Here, the impact of culture composition on the immunomodulatory and antitumor capacity of M. bovis BCG and Mycolicibacterium brumae, recently described as efficacious for BC treatment, has been addressed. Both mycobacteria grown in Middlebrook and different Sauton formulations, differing in the source of nitrogen and amount of carbon source, were studied. Our results indicate the relevance of culture medium composition on the antitumor effect triggered by mycobacteria, indicating that the most productive culture medium is not necessarily the formulation that provides the most favorable immunomodulatory profile and the highest capacity to inhibit BC cell growth. Strikingly, each mycobacterial species requires a specific culture medium composition to provide the best profile as an immunotherapeutic agent for BC treatment. Our results highlight the relevance of meticulousness in mycobacteria production, providing insight into the application of these bacteria in BC research.

Highlights

The bacterium Mycobacterium bovis bacillus Calmette-Guérin (BCG) has been produced as an immunotherapeutic agent for almost 100 years
Based on previously described formulations for M. bovis BCG production, different Sauton formulations were designed to study for the first time the growth of M. brumae in animal-component-free culture media
M. brumae pellicle became rough, robust, and densely folded when mycobacteria grew in culture medium with ZnSO4, showing increasing features when high glycerol concentration is present

Summary

Introduction

The bacterium Mycobacterium bovis bacillus Calmette-Guérin (BCG) has been produced as an immunotherapeutic agent for almost 100 years. M. bovis BCG has two main therapeutic uses: as a preventive vaccine for tuberculosis and as a therapeutic agent for non-muscle invasive bladder cancer (NMIBC) patients. For both uses, M. bovis BCG production is relevant. In the case of bladder cancer (BC) treatment, M. bovis BCG is the preferred treatment option in NMIBC patients [3]. 75% of the diagnosed cases of BC are NMIBC. For these patients, weekly intravesical instillations of M. bovis BCG after transurethral resection of the tumor are carried out to prevent recurrence and progression of the disease. Recent shortages in M. bovis BCG production have highlighted the crucial role of mycobacteria in the treatment of these patients

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