plasma exosomes isolated from two small cell lung cancer patients. RNA from plasma exosomes was isolated using the Qiagen miRNeasy Serum Plasma Kit. The minimum requirement for detection of Agilent 2100 is 1μL 10 ng/μL sample miRNAs libraries Starts from the RNA that has passed the quality inspection, the 3' -end adaptor is linked, the reverse primer is hybridized, the 5' -end adaptor is linked, the reverse transcription is made into DNA, and then PCR amplification is performed