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Introduction: MNNG HOS Transforming gene (MET) amplification and MET exon 14 (METex14) alterations in lung cancers affect sensitivity to MET proto-oncogene, receptor tyrosine kinase (MET [also known by the alias hepatocyte growth factor receptor]) inhibitors. Fluorescence in situ hybridization (FISH), next-generation sequencing (NGS), and immunohistochemistry (IHC) have been used to evaluate MET dependency. Here, we have determined the association of MET IHC with METex14 mutations and MET amplification. Methods: We collected data on a tri-institutional cohort from the Lung Cancer Mutation Consortium. All patients had metastatic lung adenocarcinomas and no prior targeted therapies. MET IHC positivity was defined by an H-score of 200 or higher using SP44 antibody. MET amplification was defined by copy number fold change of 1.8x or more with use of NGS or a MET-to-centromere of chromosome 7 ratio greater than 2.2 with use of FISH. Results: We tested tissue from 181 patients for MET IHC, MET amplification, and METex14 mutations. Overall, 71 of 181 patients (39%) were MET IHC-positive, three of 181 (2%) were MET-amplified, and two of 181 (1%) harbored METex14 mutations. Of the MET-amplified cases, two were FISH positive with MET-to-centromere of chromosome 7

Ribonucleotide reductase small subunit p53R2 was identified as a p53 target gene that provides dNTP for DNA damage repair. However, the slow transcriptional induction of p53R2 in RNA may not be rapid enough for prompt DNA damage repair, which has to occur within a few hours of damage. Here, we demonstrate that p53R2 becomes rapidly phosphorylated at Ser 72 by ataxia telangiectasia mutated (ATM) within 30 min after genotoxic stress. p53R2, as well as its heterodimeric partner RRM1, are associated with ATM in vivo. Mutational studies further indicate that ATM-mediated Ser 72 phosphorylation is essential for maintaining p53R2 protein stability and conferring resistance to DNA damage. The mutation of Ser 72 on p53R2 to alanine results in the hyperubiquitination of p53R2 and reduces p53R2 stability. MDM2, a ubiquitin ligase for p53, interacts and facilitates ubiquitination of the S72A-p53R2 mutant more efficiently than WT-p53R2 after DNA damage in vivo. Our results strongly suggest a novel mechanism for the regulation of p53R2 activity via ATM-mediated phosphorylation at Ser 72 and MDM2-dependent turnover of p53R2 dephosphorylated at the same residue.DNA damage stress ͉ protein stability ͉ signal transduction ͉ kinase D NA is surprisingly reactive and is under continuous assault from daily environmental agents such as UV light, reactive chemicals, and metabolic byproducts such as reactive oxygen species. Defects in DNA damage signaling and repair can lead to mutations, ultimately resulting in cancer (1). In addition to a potential role in cancer development, damage to cellular DNA has been used for cancer therapy and is responsible for most of the toxic effects of such therapy (1, 2). Therefore, the study of genes involved in DNA damage responses could lead to a deeper understanding of cancer development and more effective treatments of malignancies.Ribonucleotide reductase (RR) is a rate-limiting enzyme responsible for providing a balanced dNTP supply for DNA synthesis and repair (3). Unbalanced dNTP supply can lead to genetic abnormalities and cell death, underscoring the importance of the mechanisms that regulate RR activity. RR is composed of two nonidentical subunits, RRM1 and RRM2. p53R2, an analogue of RRM2 in mammalian cells, can substitute for RRM2 to interact with RRM1 and plays an important role in DNA damage induced by genotoxic stress (4, 5). p53R2 has been identified as a transcriptional target of p53 (4), whereas RRM2 is transcriptionally regulated by cell cycle associated factors, such as nuclear factor Y and E2F (6). However, the mechanism by which p53R2 activity is induced by p53 may not be rapid enough to supply dNTPs for prompt DNA repair, which can be completed within a few hours after DNA damage (1, 3). More than 90% of damaged DNA can be repaired within 8 h after non-lethal UV irradiation in HeLa cells. Yet, the p53R2 mRNA is not fully induced until 12 h after ␥-irradiation in many of p53 WT cells including normal dermal fibroblast, MCF-7, LoVo, and HCT116 cell lines (4). Additionally, we have ...

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