<i>KEAP1</i> silencing by promoter methylation is widely reported in solid tumors as part of the complex regulation of the KEAP1/NRF2 axis, but its prognostic role remains to be addressed in lung cancer.
Although dietary antioxidant supplementation or activation of endogenous antioxidants by NRF2 reduces oxidative stress and promotes early lung tumor progression, little is known about its effect on lung cancer metastasis.
An in vivo study in mice xenotransplanted with A549 cells to further explore the therapeutic potential of K-563 revealed that it also inhibited Keap1/Nrf2 pathway in lung cancer tumors.
As a first step in applying functional genomic analysis to population studies, we have examined the relationship between gene expression variation and genetic variation in a central molecular pathway (NRF2-mediated antioxidant response) associated with smoking exposure and lung cancer.
Association of loss of function with promoter polymorphisms in NRF2 or somatic and epigenetic mutations in KEAP1 and NRF2 has been found in cohorts of patients with acute lung injury/acute respiratory distress syndrome or lung cancer, which further supports the role for NRF2 in these lung diseases.
Expression of the Nrf2-targed genes NQO1 and GCLC tended to be higher (30 to 60%) in lung cancers, but was not significantly different from that in peri-cancer tissues.
Importantly, potential avenues and implications for therapeutic targeting of KEAP1-NRF2 pathway vulnerabilities for lung cancer patients will be highlighted.
In excellent agreement with this finding, we found that minor A/A homozygotes of a single nucleotide polymorphism (SNP) in the human NRF2 upstream promoter region (rs6721961) exhibited significantly diminished NRF2 gene expression and, consequently, an increased risk of lung cancer, especially those who had ever smoked.
Intriguingly, the signalling molecules perturbed by CCRK are divergent and cancer-specific, including the cell cycle regulators CDK2, cyclin D1, cyclin E and RB in glioblastoma, ovarian carcinoma and colorectal cancer, and KEAP1-NRF2 cytoprotective pathway in lung cancer.
Mutations in KEAP1/NFE2L2 genes always cause persistent Nrf2 activation in lung cancer cells that confer therapeutic resistance and aggressive tumorigenic activity, dictating either poor prognosis or short duration of response to chemotherapy in clinical observations.