USP7 and squamous cell lung carcinoma: Treatment with P5091 led to a significant and dose-dependent decrease in PE in the MDA-MB-231 WT and MCF7 cells (Figure 2C,D), which is in line with observations in ovarian cancer cells, lung squamous cell carcinoma cells and colon carcinoma xenograft models after USP7 depletion or inhibition [35,42,47].