TP53 and cancer: This could be confirmed immunohistochemically based on overexpression of P53 (OT2, 4, 6, and 7) and/or negativity for SMAD4 (OT4, 5, and 7) in tumor cells growing on the tissue surface (Fig. 5B) in cancers that showed aberrant P53 and/or SMAD4 expression in the entirety of the cancer cell population within the tissue slice.