De Wilt et al. also found no cross-resistance to a prototypical P-gp substrate (i.e. DNR) and differences in functional P-gp activity between parental and bortezomib resistant cells, suggesting that enhanced drug efflux via MDR transporters does not contribute to bortezomib resistance in NSCLC cells [21]. The gene discussed is PGP; the disease is non-small cell lung carcinoma.