Abstract: Objective To investigate serum and hepatic tissue microRNAlet-7 （let-7a and let-7b） levels and its clinical implication in patients with hepatocellular carcinoma （HCC）. Methods 54 patients with HCC and 52 healthy persons were recruited in our hospital between April 2015 and June 2016,and all the patients were confirmed by histopathological examination. Real-time fluorescence quantitative reverse transcriptase polymerase chain reaction（qRT-PCR） was applied to detect let-7a and let-7b in sera,cancerous tissues and its adjacent liver tissues. Results The results of qRT-PCR detection showed that serum let-7a level in patients with HCC was （0.6±0.4）,much lower than [（1.1±0.4）,P<0.05],and serum let-7b level was （0.3±0.1）,also significant lower than [（0.7±0.2）,P<0.05] in healthy persons;hepatic cancerous tissue let-7a level in patients with HCC was（0.3±0.1）,much lower than [（0.6±0.1）,P<0.05] in its adjacent liver tissues,and the cancerous let-7a level decreased by 2.17 times lower than in the adjacent liver tissues;hepatic cancerous let-7b level in patients with HCC was （0.4±0.2）,also much lower than[（1.3±0.4）,P<0.05] in its adjacent liver tissues,and the cancerous let-7b level decreased by 3.33 lower than in its adjacent liver tissues;serum let-7a level in 20 HCC patients with portal tumor thrombus formation was（0.4±0.2）,much lower than[（0.8±0.5）,P<0.05] in 34 HCC patients without, and serum let-7b level was（0.1±0.1）,also significantly lower than [（0.5±0.1）,P<0.05] in patients without,while serum let-7a and let-7b levels in patients with different age,gender,serum AFP levels,sizes of tumor, tumor differentiations,TNM stages and with or without tumor invasion were not significantly different（P>0.05）;cancerous tissue let-7a and let-7b levels in patients with different age,gender,serum AFP levels,sizes of tumor,tumor differentiations,TNM stages,with or without tumor invasion and portal tumor thrombus formation were not significantly different（P>0.05）. Conclusion sSerum and tumor tissue let-7a and let-7b levels decrease,and tumor tissue let-7a and let-7b levels are even lower than in its adjacent liver tissues,which hints what is still a problem and warrants further investigations in the future.

Key words: Hepatocellular carcinoma, Cancerous tissues, Pathology, MicroRNA let-7