BIRC5 and breast cancer: In addition, Western blot analysis revealed that SAHA did not affect the expression of p53, which is a survivin gene transcription negative regulator, in the wild-type p53 expressing MCF7 cells, further indicating that SAHA exhibits its anti-breast cancer effect, at least at the transcriptional level, through a p53-independent mechanism (Figure 3C; Mirza et al., 2002).