Lung Cancer Risk in Passive Smokers using Salivary Exosome-Derived MicroRNAs

[Synopsis] The objective of this study was to investigate the lung cancer risk in passive smokers using salivary exosome-derived microRNAs (mirs). Individuals were confirmed to be passive smokers by interviewing them using the Kano Test for Social Nicotine Dependence (KTSND) and measuring exhaled breath carbon monoxide (eBCO) level. Unstimulated saliva samples were collected from 25 students, and exosomes were isolated from salivary supernatants. Total RNA was isolated from the isolated exosome and washed and spun repeatedly using a filter cartridge to obtain the total RNA. Digital PCR was performed using mir-22, mir-150, and mir-155, which are related to lung cancer ; mir-191 was used as the endogenous control. Salivary exosome samples considered positive by the carbon monoxide breath analysis monitor exhibited expression of mir-22, mir-150, and mir-155, that reportedly have increased expression in lung cancer. These findings indicate the possibility of investigating lung cancer risk in passive smokers using salivary exosome-derived mirs.