Initial assessment of Id protein antagonist (aHLH) shows anti-proliferative activity on HEK293T, LS174T and HCT116 cells

Abstract

Id proteins (1–4) which are dominant-negative antagonists of the basic helix-loop-helix (bHLH) family of transcription factors function in a variety of cellular processes. They bind to the ubiquitously expressed ‘E box’ protein of the class A bHLH proteins (E12, E47, E2–2, and HEB). Each Id protein has distinct preferences and specificities for their E protein targets. A mutant version of E47 protein, an Id protein antagonist known as aHLH which is defective in DNA binding functions is known to suppress growth in human carcinoma cell lines. This work investigates the effects of the Id protein antagonist aHLH on growth and on pro-apoptotic functions in vitro using immortalized (highly tumorigenic) transformed human embryonic kidney cells (HEK293T), human epithelial colon adenocarcinoma cell line (LS174T) and human epithelial colon carcinoma cell line (HCT116). Plasmid encoding the aHLH proteins was transiently over-expressed in cultured HEK293T, LS174T and HCT116. Cell viability assay with MTT (3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) was performed. Apoptotic and cell cycle assays were also performed on the transfected cells thereafter. Here, the results demonstrate that Id inhibition by aHLH impairs cell viability, inhibits cell proliferation and induces apoptosis in HEK293T, LS174T and HCT116 cell lines. These findings on the role of aHLH in cell growth and survival could help manipulate their functions as targets for developing anti-cancer agents and could also serve as molecular markers of human cancers.