Effects of KEAP1 Silencing on the Regulation of NRF2 Activity in Neuroendocrine Lung Tumors.

Background: The KEAP1/NRF2 pathway has been widely investigated in tumors since it was implicated in cancer cells survival and therapies resistance. In lung tumors the deregulation of this pathway is mainly related to point mutations of and genes and promoter hypermethylation, but these two genes have been rarely investigated in low/intermediate grade neuroendocrine tumors of the lung.

Methods: The effects of silencing on NRF2 activity was investigated in H720 and H727 carcinoid cell lines and results were compared with those obtained by molecular profiling of KEAP1 and in a collection of 47 lung carcinoids. The correlation between methylation and transcript levels was assessed by 5-aza-dC treatment.

Results: We demonstrated that in carcinoid cell lines, the silencing induces an upregulation of NRF2 and some of its targets and that there is a direct correlation between methylation and its mRNA levels. A hypermethylation and Loss of Heterozygosity at gene locus was also observed in nearly half of lung carcinoids.

Conclusions: This is the first study that has described the effects of silencing on the regulation of NRF2 activity in lung carcinoids cells. The epigenetic deregulation of the KEAP1/NRF2 by a KEAP1 promoter hypermethylation system appears to be a frequent event in lung carcinoids.