Chlamydia pneumoniae infections and development of lung cancer: systematic review

BACKGROUND: Chlamydia pneumoniae is an obligate intracellular pathogen and is a common cause of human respiratory diseases, including pneumonia. It has been already known to have a causal relationship with some chronic diseases such as chronic obstructive pulmonary disease, asthma, and atherosclerotic cardiovascular diseases. In this review, we aim to find out the association between C. pneumoniae infection and lung cancer. METHODS: This is a systematic review on C. pneumoniae infection and the development of lung cancer, based on published articles consolidated from PubMed and Google Scholar on the topic. RESULTS: Out of 46 articles, 27 were selected and screened through the process. Twenty-four articles positively supported the hypothesis with one animal model, while 3 of them were negatively supportive. Several proposed mechanisms explain the pathogenesis with some knowledge gaps. CONCLUSION: Although some studies showed an association between C. pneumoniae infection and lung cancer, whether the C. pneumoniae infection is an individual risk factor for lung cancer is still debatable. And it needs further experimental studies on both humans and animals with large observational studies to better understand the association between C. pneumoniae infection and lung cancer.