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Peptides genetically selected for NF-κB activation cooperate with oncogene Ras and model carcinogenic role of inflammation

Natarajan, Venkatesh, Komarov, Andrei P., Ippolito, Thomas, Bonneau, Kyle, Chenchik, Alex A., Gudkov, Andrei V.
Proceedings of the National Academy of Sciences of the United States of America 2014 v.111 no.4 pp. E474
carcinogenesis, polypeptides, risk, screening, transcription factor NF-kappa B, phenotype, humans, neoplasms, transcriptional activation, inflammation, models, oligomerization, mice, tumor necrosis factors, fibroblasts, oncogenes, rats
Chronic inflammation is associated with increased cancer risk. Furthermore, the transcription factor NF-κB, a central regulator of inflammatory responses, is constitutively active in most tumors. To determine whether active NF-κB inherently contributes to malignant transformation, we isolated a set of NF-κB–activating genetic elements and tested their oncogenic potential in rodent cell transformation models. Genetic elements with desired properties were isolated using biologically active selectable peptide technology, which involves functional screening of lentiviral libraries encoding 20 or 50 amino acid-long polypeptides supplemented with endoplasmic reticulum-targeting and oligomerization domains. Twelve NF-κB–activating selectable peptides (NASPs) representing specific fragments of six proteins, none of which was previously associated with NF-κB activation, were isolated from libraries of 200,000 peptides derived from 500 human extracellular proteins. Using selective knockdown of distinct components of the NF-κB pathway, we showed that the isolated NASPs act either via or upstream of TNF receptor-associated factor 6. Transduction of NASPs into mouse and rat embryo fibroblasts did not, in itself, alter their growth. However, when coexpressed with oncogenic Ras (H-Ras ⱽ¹²), NASPs allowed rodent fibroblasts to overcome H-Ras ⱽ¹²–mediated p53-dependent senescence and acquire a transformed tumorigenic phenotype. Consistent with their ability to cooperate with oncogenic Ras in cell transformation, NASP expression reduced the transactivation activity of p53. This system provides an in vitro model of NF-κB–driven carcinogenesis and suggests that the known carcinogenic effects of inflammation may be at least partially due to NF-κB–mediated abrogation of oncogene-induced senescence.