TP53 and malignant colon neoplasm: This suggests that p53 status is not a dominant factor in the radiosensitising effect of gemcitabine and this is supported by previous reports by Robinson and Shewach (2001) using MCF-7 and MCF-7/Adr breast cancer cell lines and Chen et al (2000) using RKO-P and RKO-E6 colon cancer cell lines.