HPI-4,Hedgehog Pathway Inhibitor 4

HPI-4 does not directly target Smo. It counteracts the activities of endogenous Gli1 and Gli2 but does not directly act on transcription factor GLIs. HPI-4 significantly inhibited the proliferation of these neuronal progenitors, as measured by histone H3 phosphorylation (pH3) levels, It also reduced cellular levels of cyclin D1 protein and Gli1, Gli2, and N-Myc transcripts in the Cerebellar Granule Neuron Precursors. HPI-4 acts by perturbing ciliogenesis^[1]. Treatment with HH pathway inhibitor-4 (HPI-4) could significantly decrease human chondrosarcoma cell proliferation, invasion and migration ability. Furthermore, HPI-4 could distinctly disturb HH pathway-mediated ciliogenesis and suppress primary cilia-related protein intraflagellar transport protein IFT88 expression. HH downstream effect molecular GLI2 was restrained to block parathyroid hormone-related protein and affect MAPK/ERK-regulated matrix metalloproteinases (MMP2 and MMP9)^[2]. HPI-4(ciliobrevin A) is also a small molecule inhibitor of the catalytic heavy chain subunit of cytoplasmic dynein.