We found that fucoidan triggered apoptosis and G1 cell cycle arrest not only in wild-type p53 (p53+/+) HCT116 cells but also in p53 allele-null (p53−/−) HCT116 cells, suggesting that fucoidan could be a possible therapeutic option for CRC regardless of its p53 status. The gene discussed is TP53; the disease is colorectal carcinoma.