A commercially available preparation of Staphylococcus aureus bio-products potently inhibits tumour growth in a murine model of mesothelioma

Background and objective Mesothelioma is an incurable cancer with a rising global incidence. Intrapleural delivery of a commercially available compound made up of proteins produced by Staphylococcus aureus has been used clinically to induce pleurodesis. We investigate if this bacterial compound has anti‐tumoural activities against pleural malignancies, in addition to its pleurodesing effect. Methods The effects of the treatment on mesothelioma cells were evaluated in vitro and further tested in two validated murine models. Results This S. aureus bio‐product mixture effectively kills mesothelioma cells and induces the release of interleukin (IL)‐8, monocyte chemotactic protein (MCP)‐1 and vascular endothelial growth factor from primary human mesothelial cells but not malignant pleural mesothelioma cells in vitro. Intratumoural delivery of the treatment in BALB/c mice induced tumour necrosis and local activation of T cells. Tumour growth was significantly inhibited in the treatment group during and after the treatment period (size of tumour 58.8 ± 10.3 mm2 vs 118.3 ± 6.7 mm2 from saline controls at day 23, n = 9–12 per group), P