PPIF and melanoma: Consistent with this, we found that under normoxic conditions, knockdown (KD) of CypD by siRNAs increased HIF1α levels in human (A375P and SK-Mel-28) and mouse (B16F10) melanoma cells (Fig. 2c); however, inhibiting CypD did not affect HIF2α expression or HIF1α mRNA levels (Fig. 2c, d), suggesting specific regulation of HIF1α protein stability.