Epidermal growth factor receptor (EGFR) mutations typically occur in exons 18–21 and are established driver mutations in non-small cell lung cancer (NSCLC)1–3. Targeted therapies are approved for patients with ‘classical’ mutations and a small number of other mutations4–6. However, effective therapies have not been identified for additional EGFR mutations. Furthermore, the frequency and effects of atypical EGFR mutations on drug sensitivity are unknown1,3,7–10. Here we characterize the mutational landscape in 16,715 patients with EGFR-mutant NSCLC, and establish the structure–function relationship of EGFR mutations on drug sensitivity. We found that EGFR mutations can be separated into four distinct subgroups on the basis of sensitivity and structural changes that retrospectively predict patient outcomes following treatment with EGFR inhibitors better than traditional exon-based groups. Together, these data delineate a structure-based approach for defining functional groups of EGFR mutations that can effectively guide treatment and clinical trial choices for patients with EGFR-mutant NSCLC and suggest that a structure–function-based approach may improve the prediction of drug sensitivity to targeted therapies in oncogenes with diverse mutations.

Highlights d ERBB2 mutations occur in at least 25 tumor types with varying patterns of mutations d Mutation-induced changes in drug-binding pocket volume dictate drug sensitivity d Poziotinib inhibits mutant HER2, yielding a 42% response rate in NSCLC patients d Combination of poziotinib with T-DM1 potentiates antitumor activity of both agents

Protein arginine methyltransferase 5 (PRMT5) is an enzyme that catalyzes transfer of methyl groups from S-adenosyl methionine to the arginine residues of histones or nonhistone proteins and is involved in a variety of cellular processes. Although it is highly expressed in some tumors, its direct role in cancer growth has not been fully investigated. In this study, in human lung tissue samples, we found that PRMT5 was highly expressed in lung cancer cells whereas its expression was not detectable in benign lung tissues. Silencing PRMT5 expression strongly inhibited proliferation of lung adenocarcinoma A549 cells in tissue culture, and silencing PRMT5 expression in A549 cells also abolished growth of lung A549 xenografts in mice. In vitro and in vivo studies showed that the cell growth arrest induced by loss of PRMT5 expression was partially attributable to downregulation of fibroblast growth factor receptor signaling. These results suggest that PRMT5 and its methyltransferase activity is essential for proliferation of lung cancer cells and may serve as a novel target for the treatment of lung cancer.

During lung development, cells proliferate for a defined length of time before they begin to differentiate. Factors that control this proliferative process and how this growth process is related to lung cancer are currently unknown. Here, we found that the WD40-containing protein (p44/wdr77) was expressed in growing epithelial cells at the early stages of lung development. In contrast, p44/wdr77 expression was diminished in fully differentiated epithelial cells in the adult lung. Loss of p44/wdr77 gene expression led to cell growth arrest and differentiation. Re-expression of p44/wdr77 caused terminally differentiated cells to re-enter the cell cycle. Our findings suggest that p44/wdr77 is essential and sufficient for proliferation of lung epithelial cells. P44/Wdr77 was re-expressed in lung cancer, and silencing p44/wdr77 expression strongly inhibited growth of lung adenocarcinoma cells in tissue culture and abolished growth of lung adenocarcinoma tumor xenografts in mice. The growth arrest induced by loss of p44/wdr77 expression was partially through the p21-Rb signaling. Our results suggest that p44/wdr77 controls cellular proliferation during lung development and this growth process is re-activated during lung tumorigenesis.

Murine melanomas produce site-specific experimental brain metastases that reflect clinical reality. When injected into the internal carotid artery of mice, K-1735 melanoma cells produce metastatic lesions only in the brain parenchyma, whereas B16 melanoma cells and the somatic hybrid cells of B16 Â K-1735 melanoma cells produce metastatic lesions only in the leptomeninges and ventricles. In the present study, we identified transforming growth factor-B2 (TGF-B2), an isoform of the TGF-B family, as a molecular determinant of melanoma cell growth in the brain parenchyma. We found that the TGF-B2 mRNA was highly expressed by the K-1735 cells, whereas the B16 cells or any B16 Â K-1735 somatic cell-cell fusion hybrids have low expression. Transfection of the TGF-b2 gene into B16 cells resulted in the production of microscopic metastatic lesions in the brain parenchyma, without a decrease in metastasis to the leptomeninges or ventricles. TGF-B2 knockdown in the K-1735 melanoma cells significantly reduced metastasis to the brain parenchyma but did not induce metastasis to the leptomeninges or ventricles. These data show that TGF-B2 expression by murine melanoma cells is necessary for the establishment and growth of metastases in the brain parenchyma. [Cancer Res 2009;69(3):828-35]