Exploiting NRF2-ARE pathway activation in papillary renal cell carcinoma.

Papillary renal cell carcinoma (pRCC) is the second most frequent renal cancer subtype but has no indicated targeted treatments. MET inhibition may be a treatment for MET-driven pRCC, but there is a large group of non-MET-driven pRCC without targeted therapy. Activation of NRF2-ARE pathway has been suggested to be involved in pRCC. To study the relevance of the NRF2-ARE pathway, we characterized 60 pRCCs by copy number analysis and Whole Exome Sequencing. Because stabilisation of NRF2 results in enhanced expression of NQO1, a reductase that prevents production of reactive oxygen species, protein expression of NQO1 was analysed by immunohistochemistry (IHC) from tissue microarrays (TMAs) and by enzymatic activity assay. Finally, patient-derived pRCC cells (PDCs) were applied for drug profiling with 18 NRF2-ARE pathway inhibitors. We identified MET mutations in 5%, and mutations in four genes of NRF2-ARE pathway (NFE2L2, KEAP1, CUL3 and BACH1) in 10% of 60 pRCC samples. IHC analysis of TMAs of 638 renal cancers showed the correlation of the expression of NQO1 with poor survival outcome (p < .001) and high tumour grade (p < .001) and stage (p < .001) in pRCC. NQO1 mRNA, protein levels and enzymatic activity were increased in 56% of matched pRCC tissue samples and patient-derived cells (PDCs, n = 9). Drug screening revealed that Brusatol and Convallatoxin are potential novel drugs for pRCC. Inhibition of NRF2 represents a novel therapeutic approach for MET-independent pRCC patients.