ABCB1 and neoplasm: Thus, quinacrine inhibits heat shock factor-1,33 a major transcriptional regulator of the unfolded protein response and hypoxia inducible factor 1-α, a transcription regulator that promotes tumor cell survival under the conditions of limited oxygen supply.28 Furthermore, quinacrine has been shown to interact with phospholipid bilayers leading to inhibition of phospholipase A2 and C, which in turn may affect many membrane-spanning channels and transporters that require the presence and correct architecture of phospholipids.28 One example is the blockage of P-glycoprotein.34