H1299 EGF and Iressa stimulation

Controlled activation of epidermal growth factor receptor (EGFR) is systematically guaranteed at the molecular level, however aberrant activation of EGFR is frequently found in cancer. Transcription induced by EGFR activation often involves coordinated expression of genes that positively and negatively regulate the original signaling pathway, therefore alterations in EGFR kinase activity may reflect changes in gene expression associated with the pathway. In this study, we investigated transcriptional changes following EGF stimulation with or without the EGFR kinase inhibitor Iressa in H1299 human non-small-cell lung cancer cells (parental H1299, H1299 cells which overexpress wild-type: EGFR-WT and mutant EGFR: L858R). Our results clearly showed differences in transcriptional activity in the absence or presence of EGFR kinase activity, and genes sharing the same molecular functions showed distinct expression dynamics. The results showed particular enrichment of EGFR/ErbB signaling-related genes in a differentially expressed gene set, and significant protein expression of MIG6/RALT(ERRFI1), an EGFR negative regulator, was confirmed in L858R. High MIG6 protein expression was correlated with basal EGFR phosphorylation and inversely correlated with EGF-induced ERK phosphorylation levels. Investigation of NCI-60 cell lines showed that ERRFI1 expression was correlated with EGFR expression regardless of tissue type. These results suggest that cells accumulate MIG6 as an inherent negative regulator to suppress excess EGFR activity when basal EGFR kinase activity is considerably high. Taken together, an EGFR mutation can cause transcriptional changes to accommodate the activation potency of the original signaling pathway at the cellular level.

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Nagashima T, Ushikoshi-Nakayama R, Suenaga A, Ide K, Yumoto N, Naruo Y, Takahashi K, Saeki Y, Taiji M, Tanaka H, Tsai SF, Hatakeyama M