Determination of lung microbiota in bronchoalveolar lavage fluids of patients with lung cancer

Lung cancer, which causes high morbidity and mortality all over the world, is responsible for approximately 20% of cancer-related deaths. Nowadays, despite the very important developments in oncology, cancer is still not in the category of completely curable diseases. It has been shown that microorganisms colonizing the human body from birth, or opportunistic pathogenic microorganisms acquired from the hospital or the environment, play a role in complex carcinogenesis stages, including personal responses to cancer treatment and toxicity. Therefore, we aimed to investigate the presence of microorganisms that can be found in the lung microbiota of patients with and without lung cancer, and to compare the compositions of these microbiota in this study. Bronchoalveolar lavage (BAL) samples were collected from 31 patients diagnosed with lung cancer and 13 controls with pulmonary nodules but not diagnosed with lung cancer at Balcali Hospital of the Faculty of Medicine of Cukurova University between December 2019 and October 2020. After DNA isolation from the samples, lung microbiome analysis was performed by next generation sequencing (NGS) by targeting the 16S rRNA gene region. In addition, bacteria were identified from the samples using conventional culture methods. In our study, Neisseria and Streptococcus species in the patient group, Haemophilus and Streptococcus species in the control group were dominantly isolated in the culture when anaerobic bacteria such as Prevotella and Veillonella were found be dominant in both groups in microbiome analysis by NGS. Lactococcus, Pediococcus, Anaerobacillus and Friedmanniella were found to be closely related to the development of lung cancer. Our study is the first in our country to examine the lung microbiota of patients with lung cancer. In addition, our study is one of the few studies in the world in which lung microbiome analysis by using NGS was evaluated together with isolation in culture. Therefore, our study will shed light on studies aimed at illuminating the relationship between lung cancer and microbiota. In studies conducted to determine the relationship of microbiota with diseases, we are of the opinion that it would be more beneficial to support microbiome analysis by using NGS with conventional culture methods using appropriate media, if necessary, and to examine gut microbiota together with lung microbiota.