XBP1 and cancer: Second, targeting RtcB ligase activity will have an impact on not just the XBP1 pathway but also on tRNA maturation and other unidentified RtcB RNA substrates, potentially leading to unexpected side effects such as the production of tRNA-derived stress-induced RNAs (tiRNAs) [79] which have been demonstrated to prevent apoptosis and are considered as promising biomarkers for cancer [80].