CDKN1A and thyroid cancer: However, both CDKN1A (p21 coding gene) mRNA level and p21 protein expression levels were remarkably up-regulated by NVP-BEZ235 in all the four cell lines regardless of TP53 status and independent of p53 expression levels (Figure 4B and 4C, for 4C, representative results in the upper panel, and statistical analysis in the bottom), suggesting the inhibitory effect of NVP-BEZ235 on thyroid cancer cell growth is related to transcriptional increase of p21.