Promotion of cellular senescence by THG-1/TSC22D4 knockout through activation of JUNB.

Induction of cellular senescence in cancerous cells is an important strategy which is used in the treatment of cancer. However, cancer cells are capable of exhibiting resistance to cellular senescence through inactivation of tumor suppressors. Because of this, establishment of a route to cellular senescence induction in cancer cells is a crucial direction for developing future cancer therapies. In this study, we demonstrate the involvement of TSC-22 homologous gene-1 (THG-1, also called TSC22D4) in the suppression of cellular senescence. CRISPR/Cas9 gene editing was used to establish THG-1 knockout (KO) cells in a THG-1 positive esophageal tumor cell line. It was found that THG-1 KO cells exhibited delayed cell proliferation as well as cellular senescence. The elevated expression of the CDK inhibitor P21(CDKN1A) was also identified in senescent cells. Through the investigation of the upstream pathway for induction of P21(CDKN1A), the JUNB pathway was identified to play a critical role in P21(CDKN1A) transcription; in fact, the siRNA-mediated knockdown of JUNB reduced the abundance of P21(CDKN1A) mRNA and cellular senescence in THG-1 KO cells. These findings provide a novel insight into the induction of cellular senescence in THG-1 positive cancer cells.