ABCC1 and cancer: With this respect, by comparing cancer cell lines with different sensitivities to ER stress, Salaroglio and coworkers have shown that the ER-resistant cells also acquire a multidrug-resistant (MDR) phenotype due to higher expression of the UPR (unfolded protein response) sensor protein kinase RNA-like endoplasmic reticulum kinase (PERK) that in turn promotes NRF2-dependent MRP1 (multidrug resistance-associated protein 1) transcription.