Langsch, Stephanie; Baumgartner, Ulrich; Haemmig, Stefan; Schlup, Cornelia; Schäfer, Stephan; Berezowska, Sabina Anna; Rieger, Gregor; Dorn, Patrick; Tschan, Mario; Vassella, Erik (2016). miR-29b Mediates NF-κB Signaling in KRAS-Induced Non-Small Cell Lung Cancers. Cancer research, 76(14), pp. 4160-4169. American Association for Cancer Research AACR 10.1158/0008-5472.CAN-15-2580
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A global understanding of miRNA function in EGFR signaling pathways may provide insights into improving the management of KRAS-mutant lung cancers, which remain relatively recalcitrant to treatment. To identify miRNAs implicated in EGFR signaling, we transduced bronchial epithelial BEAS-2B cells with retroviral vectors expressing KRAS(G12V) and monitored miRNA expression patterns by microarray analysis. Through this approach, we defined miR-29b as an important target for upregulation by mutant KRAS in non-small cell lung cancers. Cell biologic analyses showed that pharmacologic inhibition of EGFR or MEK was sufficient to reduce levels of miR-29b, while PI3K inhibition had no effect. In KRAS(G12V)-transduced BEAS-2B cells, introduction of anti-miR-29b constructs increased the sensitivity to apoptosis, arguing that miR-29b mediated apoptotic resistance conferred by mutant KRAS. Mechanistic investigations traced this effect to the ability of miR-29b to target TNFAIP3/A20, a negative regulator of NF-κB signaling. Accordingly, overexpression of an miR-29b-refractory isoform of TNFAIP3 restored NF-κB and extrinsic apoptosis, confirming that TNFAIP3 is a functionally relevant target of miR-29b. We also noted that miR-29b could confer sensitivity to intrinsic apoptosis triggered by exposure to cisplatin, a drug used widely in lung cancer treatment. Thus, miR-29b expression may tilt cells from extrinsic to intrinsic mechanisms of apoptosis. Overall, our results reveal a complexity in cancer for miR-29b, which can act as either an oncogene or tumor suppressor gene depending on signaling context. Cancer Res; 76(14); 4160-9. ©2016 AACR.