Small-molecule screening yields a compound that inhibits the cancer-associated transcription factor Hes1 via the PHB2 chaperone

Abstract

The transcription factor Hes family basic helix-loop-helix transcription factor 1 (Hes1) is a downstream effector of Notch signaling and plays a crucial role in orchestrating developmental processes during the embryonic stage. However, its aberrant signaling in adulthood is linked to the pathogenesis of cancer. In the present study, we report the discovery of small organic molecules (JI051 and JI130) that impair the ability of Hes1 to repress transcription. Hes1 interacts with the transcriptional corepressor transducing-like enhancer of split 1 (TLE1) via an interaction domain comprising two tryptophan residues, prompting us to search a chemical library of 1,800 small molecules enriched for indole-like π-electron-rich pharmacophores for a compound that blocks Hes1-mediated transcriptional repression. This screening identified a lead compound whose extensive chemical modification to improve potency yielded JI051, which inhibited HEK293 cell proliferation with an EC of 0.3 μm Unexpectedly, using immunomagnetic isolation and nanoscale LC-MS/MS, we found that JI051 does not bind TLE1 but instead interacts with prohibitin 2 (PHB2), a cancer-associated protein chaperone. We also found that JI051 stabilizes PHB2's interaction with Hes1 outside the nucleus, inducing G/M cell-cycle arrest. Of note, JI051 dose-dependently reduced cell growth of the human pancreatic cancer cell line MIA PaCa-2, and JI130 treatment significantly reduced tumor volume in a murine pancreatic tumor xenograft model. These results suggest a previously unrecognized role for PHB2 in the regulation of Hes1 and may inform potential strategies for managing pancreatic cancer.

Hes1 Is Essential in Proliferating Ductal Cell–Mediated Development of Intrahepatic Cholangiocarcinoma

“…(50) In contrast, we previously reported that specific inhibition of Hes1 in mice elicited a tumor-suppressing effect on pancreatic cancer cells without severe adverse events. (20) In this study, liver-specific Hes1 deletion did not affect the healthy liver development. Therefore, targeting a key effector, such as Hes1, rather than the complete blockade of Notch signaling, can provide effective tumor suppression with reduced adverse events in ICC.…”

“…CAN-20-1161 promoted ICC development in mice (16)(17)(18)(19), whereas inhibition of HES1 suppressed the growth of various tumors, including human pancreatic ductal adenocarcinoma. (20,21) These findings suggest that Notch signaling, particularly the Notch/Hes1 axis, contributes to the development of ICC, although it remains unclear whether Hes1 expression directly affects ICC development.…”

The prohibitin-binding compound fluorizoline affects multiple components of the translational machinery and inhibits protein synthesis

“…Compounds FL3, Mel 6, Mel 4, JI130, and FLZ were synthesized following described procedures (26,27,32,56). NAC, ISRIB (57), CHX, thapsigargin, and DMSO were purchased from Merck (Castle Hill, NSW, Australia).…”

Prohibitin ligands: a growing armamentarium to tackle cancers, osteoporosis, inflammatory, cardiac and neurological diseases

“…For example, PHB1 heterodimerizes with MAX and MATα1 to bind to the E-box element and repress its promoter activity [26]. PHBs also trap the transcription factors HES1 and STAT3 outside the nucleus to inhibit their transcriptional activity [29,30]. In the case of STAT3, this interaction takes place in mitochondria to promote cell survival [29,31].…”

“…While they were searching for inhibitors of Hes1 signaling, Uesugi, Kodama and collaborators identified D8C (14, Fig. 11) that significantly blocks Hes1 transcriptional activity and proliferation of HEK293 cells with an EC50 of 1.8 μM [30]. These authors synthesized a series of 130 compounds and identified in particular two improved derivatives, JI051 (15) and JI130 ( 16), the latter one displaying an enhanced solubility in water.…”