Knock-Down of Id1 and Id3 Proteins Induces Apoptosis in Human Colon Carcinoma (HCT116) Cells

Abstract

Id (Inhibitor of differentiation) proteins belong to the Helix-Loop-Helix (HLH) group of transcription factors and they are characterized by the absence of their DNA-binding domain. Id proteins are involved in cellular processes. These biological roles include cell growth, differentiation, senescence, apoptosis, angiogenesis and neoplastic transformation. This work aimed at investigating the consequences of down-regulating Id proteins on growth and pro-apoptotic functions in an in vitro model using HCT116 by siRNA gene knock-down. This objective was achieved by using antisense oligonucleotides complementary to Id1, Id2 and Id3 mRNA on human epithelial colon carcinoma cell line (HCT116). Silencing of Id1 and Id3 in HCT116 resulted in widespread cell death but not S-phase arrest. Interestingly, knock-down of Id2 neither resulted in induction of apoptosis nor cell growth arrest. However, since it was able to reduce viable cell populations of HCT116 at 48 h post-transfection, it may imply that cell death and growth arrest following down-regulation of Id2 may occur via a different mechanism. These observations suggest that Id1 and Id3 could provide some therapeutic opportunities to cure colonic cancers.