As Notch signaling plays an essential role in cancer stem cells, we detected downregulation of Notch1 and Notch2 in USP1-KO cells by qRT-PCR; however, we did not detect any difference in ubiquitination of proteins involved in Notch signaling between USP1-KO and wild-type cells using label-free quantification LC-MS/MS. This evidence concerns the gene NOTCH2 and cancer.