CTPS2 and cancer: Interestingly, although the CTPS2 Chronos guide depletion scores were close to 0 (mean = −0.038), highlighting its non-essentiality in cancer cell survival and proliferation, we observed a CTPS1 guide depletion (high negative scores towards −1) in most of the 1,070 cell lines (Chronos score mean = −0.579), indicative of its essentiality (Fig 7).