Effect of amplification of xenobiotic detoxification pathways genes on survival in lung adenocarcinoma versus squamous cell carcinoma bases on the Cancer Genome Atlas provisional database.

Abstract

e14093 Background: Ral interacting protein (RLIP76) is a stress-responsive anti-apoptotic efflux transporter of the mercapturic acid pathway (MPy). The MPy enzymes are an essential component of the broader xenobiotic detoxification pathways (XDP) that are regulated by p53 (TP53) in response to xenobiotic/oxidative stress. Homozygous Rlip knockout (Rlip-/-) mice are resistant to benzopyrene induced adenocarcinoma and have constitutive activation of p53. The cancer-resistant phenotype of Rlip-/- mice is the diametric opposite of p53 homozygous knockout mice (p53-/-) mice, which die before the age of 24 weeks of spontaneous malignancy. Methods: Our preliminary studies show that creating Rlip deficiency through pharmacological or genetic methods caused all p53-/- mice to remain cancer-free at an unprecedented age of 32 weeks. This degree of cancer prevention has never been observed with any previous pharmacological or genetic intervention in p53-/- mice. Transcriptomic and epigenomic profiling of the cancer-free p53-/- mice revealed that the direction of change in expression of a network of Rlip-linked XDP enzymes and signaling proteins was identical to that in the cancer-resistant Rlip-/- mice. Results: We hypothesized that the activity of this Rlip-linked subset of the XDP enzymes/signaling proteins (designated XMN1) is a determinant of carcinogenic susceptibility caused by p53 loss. To examine this possibility, we queried the TCGA (The Cancer Genome Atlas) database to determine whether components of XMN1 were differentially expressed in human malignancy, and whether this was associated with overall survival. We focused on non-small cell lung cancer because of the high incidence of p53 mutations in these cancers. To our surprise, we found amplification or upregulation of XMN1 components conferred a reduced survival in lung adenocarcinoma but prolonged survival in squamous cell carcinoma. Conclusions: The mechanisms underlying this remarkable diametrically opposite effect on prognosis of are unknown and suggest opposed functions of XMN1 in Squamous verses Adenocarcinoma.