BIRC5 and cancer: In contrast, a significant decrease in HT-29 tumour formation for HT-29 cells treated with the combinatorial regimen was evident, indicating that although survivin knockdown as a mono-treatment is not sufficient to eliminate HT-29 cancer stem cells, the combination with survivin RNAi with classical chemotherapeutic drugs, such as 5-FU, is able to eliminate colorectal cancer stem cells.