PDIA4 and cancer: Among the proteins with reduced abundance in the NGLY1-knockdown cells, several of them (e.g., VCP, PDIA4, HSPA5 and HIST1H4A) have been linked to the survival and drug resistance of cancer cells.22–25 Thus, part of the anti-melanoma responses associated with NGLY1 inhibition may be attributed to the modulation of these gene products.