NNC 55-0396, a T-type Ca2+ channel inhibitor, inhibits angiogenesis via suppression of hypoxia-inducible factor-1α signal transduction

Mitochondrial respiration is required for hypoxia-inducible factor (HIF)-1α stabilization, which is important for tumor cell survival, proliferation, and angiogenesis. Herein, small molecules that inhibit HIF-1α protein stability by targeting mitochondrial energy production were screened using the Library of Pharmacologically Active Compounds and cell growth assay in galactose or glucose medium. NNC 55-0396, a T-type Ca 2+ channel inhibitor, was selected as a hit from among 1,280 small molecules. NNC 55-0396 suppressed mitochondrial reactive oxygen species-mediated HIF-1α expression as well as stabilization by inhibiting protein synthesis in a dose-dependent manner. NNC 55-0396 inhibited tumor-induced angiogenesis in vitro and in vivo by suppressing HIF-1α stability. Moreover, NNC 55-0396 significantly suppressed glioblastoma tumor growth in a xenograft model. Thus, NNC 55-0396, a small molecule targeting T-type Ca 2+ channel, was identified by the systemic cell-based assay and was shown to have antiangiogenic activity via the suppression of HIF-1α signal transduction. These results provide new insights into the biological network between ion channel and HIF-1α signal transduction. Key message HIF-1α overexpression has been demonstrated in hypoxic cancer cells. NNC 55-0396, a T-type Ca 2+ channel inhibitor, inhibited HIF-1α expression via both proteasomal degradation and protein synthesis pathways. T-type Ca 2+ channel inhibitors block angiogenesis by suppressing HIF-1α stability and synthesis. NNC 55-0396 could be a potential therapeutic drug candidate for cancer treatment.