PRKD1 and colorectal carcinoma: However, in contrast to the results in KRAS-positive CRC cell lines, in WI-38 cells KRAS failed to increase ZNF304 protein levels (Figure 8B) or significantly stimulate USP28 and PRKD1 transcription (Figure 8C), explaining at least in part why KRAS expression does not result in INK4-ARF silencing.