Intriguingly, we detected a profound deficit in Myc-induced beta-cell proliferation in CTSL-deficient animals after 2-weeks of MycERTAM activation (0.19% of proliferating tumor cells in the CTSLKO mice compared to 21.6% in the CTSL WT lesions) (Fig 4B) that was not apparent in the early premalignant stages of Myc-induced tumorigenesis in the MycERTAM;Bcl-xL;CTSLKO mice (Fig 3A). The gene discussed is MYC; the disease is neoplasm.