CCNA2 and colorectal cancer: Sun et al. (2009) studied the effect of Spermidine/spermine N1-acetyltransferase (SSAT) on the cell cycle of colorectal cancer cells. SSAT expressing recombinant adenovirus, Ad-SSAT was reported to cause a surge in the enzyme expression, where it limited the growth of HT-29 cells by arresting the cell cycle in S-phase. As seen from the reporter gene assay, Ad-SSAT suppressed the expression of nuclear factor E2F-1 and cyclin A in Lovo cells and HT-29 cells (Sun et al., 2008a).