In particular, phosphorylation of RtcB at Y306 perturbsits interaction with IRE1, significantly attenuating XBP1 mRNA splicing.11 PTP1B is a well-studied phosphatase involvedin many pathway control mechanisms, such as the downregulation ofinsulin,13 modulation of cell growth andproliferation,14 and regulation of leptinsignaling.15 Moreover, an overexpressionof this protein has been found in breast, prostate, and gastric cancers.16 The overexpression of PTP1B has been consideredan effective prosurvival mechanism of cancer cells by activating theRtcB ligase. This evidence concerns the gene PTPN1 and cancer.