7291

TWIST1

twist family bHLH transcription factor 1;TWIST1;twist family bHLH transcription factor 1

B-HLH DNA binding protein|H-twist|TWIST homolog of drosophila|class A basic helix-loop-helix protein 38|twist basic helix-loop-helix transcription factor 1|twist homolog 1|twist-related protein 1

7p21.2

protein-coding

KRAS mutant lung cancers are generally refractory to chemotherapy as well targeted agents. To date, the identification of drugs to therapeutically inhibit K-RAS have been unsuccessful, suggesting that other approaches are required. We demonstrate in both a novel transgenic mutant Kras lung cancer mouse model and in human lung tumors that the inhibition of Twist1 restores a senescence program inducing the loss of a neoplastic phenotype. The Twist1 gene encodes for a transcription factor that is essential during embryogenesis. Twist1 has been suggested to play an important role during tumor progression. However, there is no in vivo evidence that Twist1 plays a role in autochthonous tumorigenesis. Through two novel transgenic mouse models, we show that Twist1 cooperates with Kras(G12D) to markedly accelerate lung tumorigenesis by abrogating cellular senescence programs and promoting the progression from benign adenomas to adenocarcinomas. Moreover, the suppression of Twist1 to physiological levels is sufficient to cause Kras mutant lung tumors to undergo senescence and lose their neoplastic features. Finally, we analyzed more than 500 human tumors to demonstrate that TWIST1 is frequently overexpressed in primary human lung tumors. The suppression of TWIST1 in human lung cancer cells also induced cellular senescence. Hence, TWIST1 is a critical regulator of cellular senescence programs, and the suppression of TWIST1 in human tumors may be an effective example of pro-senescence therapy.

OBJECTIVE: Endothelial progenitor cells (EPCs) can significantly improve tissue repair by providing regeneration potential within injured cardiovascular tissue; however, it is challenging to obtain a sufficient amount of functional EPCs from aged patients for autologous stem cell therapy. To overcome this issue, we aimed to establish adequate ex vivo expansion protocols and identify repair modulators of cellular senescence. The senescence repair circuit of hypoxia-preconditioned senescent EPCs (hyp-old EPCs) was examined in an effort to enhance their regenerative potential. APPROACH AND RESULTS: Long-term culturing of EPCs in normoxic conditions markedly induced the expression of p21, whereas siRNA targeting of p21 in old EPCs significantly enhanced the proliferation potential of cells. Hyp-old EPCs displayed increased hypoxia-inducible factor-1alpha and TWIST expression. siRNA inhibition of TWIST, a target molecule of the hypoxia-inducible factor-1alpha, markedly upregulated the expression of p21 in hyp-old EPCs by reprogramming cell-cycle regulatory proteins. In a hindlimb model of ischemia, the transplantation of hyp-old EPCs enhanced the blood flow ratio and capillary density, improved cellular proliferation and cell survival at ischemic sites, and augmented the secretion of pivotal tissue angiogenic cytokines. It has been previously demonstrated that the restoration of old EPCs from a senescent state by hypoxia preconditioning is tightly mediated by the downregulation of p21 via the hypoxia-inducible factor-1alpha-TWIST axis. CONCLUSIONS: This study introduces ex vivo expansion protocols involving hypoxic preconditioning that are suitable for efficiently expanding old EPCs without senescence through modulation of the hypoxia-induced hypoxia-inducible factor-1alpha-TWIST-p21 axis. In addition, the expanded cells are shown to be useful for therapeutic vasculogenesis.