Mycobacteria Treatment Inhibits Bladder Cancer Cell Migration, Invasion, and Anchorage-Independent Growth

Bladder cancer (BC) is a highly recurrent and invasive malignancy, with <i>Mycobacterium bovis</i> BCG serving as the primary immunotherapy, particularly for non-muscle-invasive bladder cancer (NMIBC). However, the mechanisms underlying BCG's antitumor effects and the potential of non-tuberculous mycobacteria like <i>Mycobacterium brumae</i> remain unclear. This study investigates the antitumor effects of <i>M. bovis</i> BCG and <i>M. brumae</i> on BC cell migration, invasion, and anchorage-independent growth. BC cell lines representing different stages of tumor differentiation were treated with either <i>M. bovis</i> BCG or <i>M. brumae</i>. Cell migration was assessed through wound healing and transwell assays, invasiveness by transwell invasion assays, MMP-9 production by gelatin zymography, and anchorage-independent growth via soft agar colony formation. Both mycobacteria inhibited individual cell migration across all BC lines, while collective migration was only reduced in intermediate-grade cells. Both treatments also reduced invasiveness, associated with decreased MMP-9 production. Furthermore, <i>M. brumae</i> inhibited anchorage-independent growth across all BC lines, while <i>M. bovis</i> BCG had a more selective effect, primarily inhibiting growth in high-grade cells. In conclusion, both mycobacteria reduce migration, invasion, and anchorage-independent growth of BC cells, with their effectiveness varying by species and tumor differentiation grade.