MKI67 and neoplasm: By immunohistochemical staining of tumor-free mucosa with antibodies detecting Ki67 and cl.PARP, we found the proliferative capacity of nontransformed intestinal epithelial cells to be marginally decreased and the viability to be unaltered in mice after treatment with 5FU, the BCL-XL inhibitor or the combination of both (Fig. 5a and for quantification Fig. S3b).