Objective To explore the changes and significane of USP20 and HIF-α expression in breast cancer.Methods Following transfection of shRNA-USP20 lentivirus into breast cancer MDA-MB-231 cells,the gene and protein expression levels of USP20 were detected using fluorescence quantitative PCR and Western Blot.Subsequently,the overexpression of USP20 was observed to determine its effect on HIF-α expression.Similarly,siRNA-USP20 was used to knock down USP20 in breast cancer MDA-MB-231 cells,followed by detection of gene and protein expression levels using fluorescence quantitative PCR and Western Blot.The subsequent changes in HIF-α expression were then examined.Rusults The positive expression rates of USP20 and HIF-α in breast cancer tissues were 69.6%and 46.83%,respectively,while they were negatively expressed in the adjacent normal tissues,with statistically significant differences(P＜0.01).The positive expressions of USP20 and HIF-α were predomi-nantly observed in the cytoplasm of breast cancer tissue,with a smaller amount present in the nucleus.There was a significant positive correlation between USP20 and HIF-α in breast cancer.Following transfection of shRNA-USP20 lentivirus into MDA-MB-231 cells,both the protein and gene expression levels of USP20 significantly increased(P＜0.01).Over-expression of USP20 did not affect HIF-α mRNA levels but led to a significant increase in HIF-α protein expression(P＜0.01).Conversely,siRNA-USP20 interference resulted in a significant decrease in both the protein and gene expression levels of USP20(P＜0.01),without affecting HIF-α mRNA levels;however,it caused a notable reduction in HIF-α protein expression(P＜0.01).Conclusion The expression of USP20 exhib-ited a significant positive correlation with HIF-α in breast cancer.Overexpression of USP20 led to a substantial increase in HIF-α protein expression,while knock-down of the USP20 gene resulted in a significant decrease in HIF-α protein levels.Therefore,it can be inferred that USP20 may exert its influence on the development of breast cancer through modulation of HIF-α expression,thereby providing crucial experimental evidence for clinical treat-ment,prognosis,and further investigations.