Transforming activities of Chlamydia pneumoniae in human mesothelial cells

Knowledge in viral oncology has made considerable progress in the field of cancer fight. However, the role of bacteria as mediators of oncogenesis has not yet been elucidated. As cancer still is the leading cause of death in developed countries, understanding the long-term effects of bacteria has become of great importance as a possible means of cancer prevention. This study reports that Chlamydia pneumoniae infection induces transformation of human mesothelial cells. Mes1 cells infected with C. pneumoniae at a multiplicity of infection of 4 inclusion-forming units/cell showed many intracellular inclusion bodies. After a 7-day infection an increased proliferative activity was also observed. Real-time PCR analysis revealed a strong induction of calretinin, Wilms' tumour gene 1, osteopontin, matrix metalloproteinases-2, and membrane-type 1 metalloproteinases gene expression in Mes1 cell, infected for a longer period (14 days). The results were confirmed by western blot analysis. Zymography analysis showed that C. pneumoniae modulated the in-vitro secretion of MMP-2 in Mes1 cells both at 7 and 14 days. Cell invasion, as measured by matrigel-coated filter, increased after 7 and 14 days infection with C. pneumoniae, compared with uninfected Mes1 cells. The results of this study suggest that C. pneumoniae infection might support cellular transformation, thus increasing lung cancer risk.