Exome sequencing of head and neck squamous cell carcinoma reveals inactivating mutations in NOTCH1

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide. To explore the genetic origins of this cancer, we used whole-exome sequencing and gene copy number analyses to study 32 primary tumors. Tumors from patients with a history of tobacco use had more mutations than did tumors from patients who did not use tobacco, and tumors that were negative for human papillomavirus (HPV) had more mutations than did HPV-positive tumors. Six of the genes that were mutated in multiple tumors were assessed in up to 88 additional HNSCCs. In addition to previously described mutations in TP53, CDKN2A, PIK3CA, and HRAS, we identified mutations in FBXW7 and NOTCH1. Nearly 40% of the 28 mutations identified in NOTCH1 were predicted to truncate the gene product, suggesting that NOTCH1 may function as a tumor suppressor gene rather than an oncogene in this tumor type.     

Glucose-6-phosphate dehydrogenase mosaicism: utilization as a cell marker in the study of leiomyomas

The sex-linked electrophoretic variants A and B of glucose-6-phosphate dehydrogenase were studied in 86 samples of myometrium and 27 leiomyomas from five heterozygous women. All but one sample of myometrium had both A and B bands in equal or nearly equal amounts. In contrast to this, all of the leiomyomas had either an A band or a B band. Both A and B tumors were found in all uteri. These findings are consistent with the hypothesis that these tumors arose from single cells.     

An X chromosome gene, WTX, is commonly inactivated in Wilms tumor

Wilms tumor is a pediatric kidney cancer associated with inactivation of the WT1 tumor-suppressor gene in 5 to 10% of cases. Using a high-resolution screen for DNA copy-number alterations in Wilms tumor, we identified somatic deletions targeting a previously uncharacterized gene on the X chromosome. This gene, which we call WTX, is inactivated in approximately one-third of Wilms tumors (15 of 51 tumors). Tumors with mutations in WTX lack WT1 mutations, and both genes share a restricted temporal and spatial expression pattern in normal renal precursors. In contrast to biallelic inactivation of autosomal tumor-suppressor genes, WTX is inactivated by a monoallelic "single-hit" event targeting the single X chromosome in tumors from males and the active X chromosome in tumors from females.     

Mutations in CIC and FUBP1 contribute to human oligodendroglioma

Oligodendrogliomas are the second most common malignant brain tumor in adults and exhibit characteristic losses of chromosomes 1p and 19q. To identify the molecular genetic basis for this alteration, we performed exomic sequencing of seven tumors. Among other changes, we found that the CIC gene (homolog of the Drosophila gene capicua) on chromosome 19q was somatically mutated in six cases and that the FUBP1 gene [encoding far-upstream element (FUSE) binding protein] on chromosome 1p was somatically mutated in two tumors. Examination of 27 additional oligodendrogliomas revealed 12 and 3 more tumors with mutations of CIC and FUBP1, respectively, 58% of which were predicted to result in truncations of the encoded proteins. These results suggest a critical role for these genes in the biology and pathology of oligodendrocytes.     

ROS-generating mitochondrial DNA mutations can regulate tumor cell metastasis

Mutations in mitochondrial DNA (mtDNA) occur at high frequency in human tumors, but whether these mutations alter tumor cell behavior has been unclear. We used cytoplasmic hybrid (cybrid) technology to replace the endogenous mtDNA in a mouse tumor cell line that was poorly metastatic with mtDNA from a cell line that was highly metastatic, and vice versa. Using assays of metastasis in mice, we found that the recipient tumor cells acquired the metastatic potential of the transferred mtDNA. The mtDNA conferring high metastatic potential contained G13997A and 13885insC mutations in the gene encoding NADH (reduced form of nicotinamide adenine dinucleotide) dehydrogenase subunit 6 (ND6). These mutations produced a deficiency in respiratory complex I activity and were associated with overproduction of reactive oxygen species (ROS). Pretreatment of the highly metastatic tumor cells with ROS scavengers suppressed their metastatic potential in mice. These results indicate that mtDNA mutations can contribute to tumor progression by enhancing the metastatic potential of tumor cells.     

EGFR mutations in lung cancer: correlation with clinical response to gefitinib therapy

Receptor tyrosine kinase genes were sequenced in non-small cell lung cancer (NSCLC) and matched normal tissue. Somatic mutations of the epidermal growth factor receptor gene EGFR were found in 15of 58 unselected tumors from Japan and 1 of 61 from the United States. Treatment with the EGFR kinase inhibitor gefitinib (Iressa) causes tumor regression in some patients with NSCLC, more frequently in Japan. EGFR mutations were found in additional lung cancer samples from U.S. patients who responded to gefitinib therapy and in a lung adenocarcinoma cell line that was hypersensitive to growth inhibition by gefitinib, but not in gefitinib-insensitive tumors or cell lines. These results suggest that EGFR mutations may predict sensitivity to gefitinib.     

Transmission characteristics of Tomato chlorosis virus (ToCV) by Bemisia tabaci MED and its effects on host preference of vector whitefly

The epidemiology of Tomato chlorosis virus(ToCV) in China is closely associated with its vector whitefly, Bemisia tabaci(Gennadius) MED. However, the transmission characteristics of ToCV by B. tabaci MED remain poorly understood. In this study, we analyzed: 1) the horizontal and vertical transmission of ToCV by B. tabaci MED whiteflies; 2) the acquisition of ToCV by male and female B. tabaci MED whiteflies after different feeding durations; 3) the transmission efficacy of viruliferous male and female B. tabaci MED whiteflies after different inoculation access periods(IAPs); 4) the retention of ToCV by viruliferous male and female B. tabaci MED whiteflies after a 48 h acquisition access period(AAP); and 5) the effects of ToCV on host choice of healthy or ToCV-infected tomato plant of viruliferous and non-viruliferous B. tabaci MED at different time points. Our results showed that: 1) viruliferous males could not transfer ToCV to non-viruliferous females, and vice versa, viruliferous females could not pass on ToCV to non-viruliferous males. ToCV could not be detected in the F1 generation adults; 2) ToCV could be detected within 4.0% of females or males after a 20 min AAP; 3) ToCV could be detected in 33.3% of tomato plants inoculated by 10 viruliferous males or females with IAPs of 20 or 30 min; 4) the maximum retention time in females was 7 and 5 days in males; and 5) non-viruliferous B. tabaci MED did not show a preference for ToCV-infected tomato plants or healthy tomato plants. However, viruliferous B. tabaci MED whiteflies did prefer to settle on healthy tomato plants over ToCV-infected tomato plants. These findings will be helpful to better understand the epidemiology of the recently emerged plant virus, ToCV, in tomato fields in China.     

First report of field resistance to cyantraniliprole,a new anthranilic diamide insecticide,on Bemisia tabaci MED in China

The Bemisia tabaci (Gennadius) cryptic species complex comprises important insect pests that cause devastating damage to agricultural crops worldwide. In China, the B. tabaci Mediterranean (MED) (or biotype Q) species is threatening agricultural production all over the country as resistance to commonly used insecticides has increased. This situation highlights the need for alternative pest control measures. Cyantraniliprole, a novel anthranilic diamide insecticide, has been widely employed to control Hemipteran pests. To monitor the levels of resistance to cyantraniliprole in B. tabaci field populations in China, bioassays were conducted for 18 field samples from nine provinces over two years. Compared with median lethal concentration (LC₅₀) for the MED susceptible strain, all field samples had significantly higher resistance to cyantraniliprole. Furthermore, resistance factors (RFs) increased significantly in samples from Shanxi (from 5.62 in 2015 to 25.81 in 2016), Hunan (3.30 in 2015 to 20.97 in 2016) and Hubei (from 9.81 in 2015 to 23.91 in 2016) provinces. This study indicates a considerable decrease in the efficacy of cyantraniliprole against B. tabaci and establishes a baseline of susceptibility that could serve as a reference for future monitoring and management of B. tabaci resistance to cyantraniliprole.     

Germ line p53 mutations in a familial syndrome of breast cancer, sarcomas, and other neoplasms

Familial cancer syndromes have helped to define the role of tumor suppressor genes in the development of cancer. The dominantly inherited Li-Fraumeni syndrome (LFS) is of particular interest because of the diversity of childhood and adult tumors that occur in affected individuals. The rarity and high mortality of LFS precluded formal linkage analysis. The alternative approach was to select the most plausible candidate gene. The tumor suppressor gene, p53, was studied because of previous indications that this gene is inactivated in the sporadic (nonfamilial) forms of most cancers that are associated with LFS. Germ line p53 mutations have been detected in all five LFS families analyzed. These mutations do not produce amounts of mutant p53 protein expected to exert a trans-dominant loss of function effect on wild-type p53 protein. The frequency of germ line p53 mutations can now be examined in additional families with LFS, and in other cancer patients and families with clinical features that might be attributed to the mutation.     

PDGFRA activating mutations in gastrointestinal stromal tumors

Most gastrointestinal stromal tumors (GISTs) have activating mutations in the KIT receptor tyrosine kinase, and most patients with GISTs respond well to Gleevec, which inhibits KIT kinase activity. Here we show that approximately 35% (14 of 40) of GISTs lacking KIT mutations have intragenic activation mutations in the related receptor tyrosine kinase, platelet-derived growth factor receptor alpha (PDGFRA). Tumors expressing KIT or PDGFRA oncoproteins were indistinguishable with respect to activation of downstream signaling intermediates and cytogenetic changes associated with tumor progression. Thus, KIT and PDGFRA mutations appear to be alternative and mutually exclusive oncogenic mechanisms in GISTs.     

Mutations, chromosomal aberrations, and tumors in insects treated with oncogenic virus

An increased incidence of lethal mutations, visible mutations, chromosomal losses, chromosomal nondisjunctions, and tumors resulted when drosophila were placed in medium containing Rous-sarcoma virus. In the group treated, a few mosaics of the eye and translocations appeared as well. There is a suggestion, from preliminary data, that the size of chromosomal puffs may be reduced by this RNA virus, but the difference is not significant. Tests for the persistence of virus in progeny have been negative so far.     

Defect in vitamin B12 release from lysosomes: newly described inborn error of vitamin B12 metabolism

Cultured diploid fibroblasts from a patient with a previously undescribed inborn error of cobalamin metabolism accumulate unmetabolized, nonprotein-bound vitamin B12 in lysosomes. These cells are able to endocytose the transcobalamin II-B12 complex and to release B12 from transcobalamin II. The freed vitamin B12 is not released from lysosomes into the cytoplasm of the cell. This suggests that there is a specific lysosomal transport mechanism for vitamin B12 in the human.     

Mutations that increase the life span of C. elegans inhibit tumor growth

Mutations in gld-1 cause lethal germline tumors in the nematode Caenorhabditis elegans. We find that a wide variety of mutations that extend C. elegans' life span confer resistance to these tumors. The long life spans of daf-2/insulin-receptor mutants were not shortened at all by gld-1 mutations; we attribute this finding to decreased cell division and increased DAF-16/p53-dependent apoptosis within the tumors. Mutations that increase life span by restricting food intake or inhibiting respiration did not affect apoptosis but reduced tumor cell division. Unexpectedly, none of these longevity mutations affected mitosis in normal germlines; this finding suggests that cellular changes that lead to longevity preferentially antagonize tumor cell growth.     

Signaling pathways for PC12 cell differentiation: making the right connections

A key issue in signal transduction is how signaling pathways common to many systems-so-called canonical signaling cassettes-integrate signals from molecules having a wide spectrum of activities, such as hormones and neurotrophins, to deliver distinct biological outcomes. The neuroendocrine cell line PC12, derived from rat pheochromocytoma, provides an example of how one canonical signaling cassette-the Raf --> mitogen-activated protein kinase kinase (MEK) --> extracellular signal-regulated kinase (ERK) pathway-can promote distinct outcomes, which in this case include neuritogenesis, gene induction, and proliferation. Two growth hormones, epidermal growth factor (EGF) and nerve growth factor (NGF), use the same pathway to cause PC12 proliferation and differentiation, respectively. In addition, pituitary adenylate cyclase-activating polypeptide (PACAP), a neurotransmitter that also causes differentiation, uses the same canonical cassette as NGF but in a different way. The Connections Map for PC12 Cell Differentiation brings into focus the complex array of specific cellular responses that rely on canonical signal transduction systems.     

BRCA1 tumor suppression depends on BRCT phosphoprotein binding, but not its E3 ligase activity

Germline mutations of the breast cancer 1 (BRCA1) gene are a major cause of familial breast and ovarian cancer. The BRCA1 protein displays E3 ubiquitin ligase activity, and this enzymatic function is thought to be required for tumor suppression. To test this hypothesis, we generated mice that express an enzymatically defective Brca1. We found that this mutant Brca1 prevents tumor formation to the same degree as does wild-type Brca1 in three different genetically engineered mouse (GEM) models of cancer. In contrast, a mutation that ablates phosphoprotein recognition by the BRCA C terminus (BRCT) domains of BRCA1 elicits tumors in each of the three GEM models. Thus, BRCT phosphoprotein recognition, but not the E3 ligase activity, is required for BRCA1 tumor suppression.     

Two G protein oncogenes in human endocrine tumors

Somatic mutations in a subset of growth hormone (GH)-secreting pituitary tumors convert the gene for the alpha polypeptide chain (alpha s) of Gs into a putative oncogene, termed gsp. These mutations, which activate alpha s by inhibiting its guanosine triphosphatase (GTPase) activity, are found in codons for either of two amino acids, each of which is completely conserved in all known G protein alpha chains. The likelihood that similar mutations would activate other G proteins prompted a survey of human tumors for mutations that replace either of these two amino acids in other G protein alpha chain genes. The first gene so far tested, which encodes the alpha chain of Gi2, showed mutations that replaced arginine-179 with either cysteine or histidine in 3 of 11 tumors of the adrenal cortex and 3 of 10 endocrine tumors of the ovary. The mutant alpha i2 gene is a putative oncogene, referred to as gip2. In addition, gsp mutations were found in 18 of 42 GH-secreting pituitary tumors and in an autonomously functioning thyroid adenoma. These findings suggest that human tumors may harbor oncogenic mutations in various G protein alpha chain genes.