eEF1A2 promotes PTEN-GSK3ß-SCF complex-dependent degradation of Aurora kinase A and is inactivated in breast cancer.

The translation elongation factor eEF1A promotes protein synthesis. Its methylation by METTL13 increases its activity, supporting tumor growth. However, in some cancers, a high abundance of eEF1A isoforms is associated with a good prognosis. Here, we found that eEF1A2 exhibited oncogenic or tumor-suppressor functions depending on its interaction with METTL13 or the phosphatase PTEN, respectively. METTL13 and PTEN competed for interaction with eEF1A2 in the same structural domain. PTEN-bound eEF1A2 promoted the ubiquitination and degradation of the mitosis-promoting Aurora kinase A in the S and G2 phases of the cell cycle. eEF1A2 bridged the interactions between the SKP1-CUL1-FBXW7 (SCF) ubiquitin ligase complex, the kinase GSK3ß, and Aurora-A, thereby facilitating the phosphorylation of Aurora-A in a degron site that was recognized by FBXW7. Genetic ablation of Eef1a2 or Pten in mice resulted in a greater abundance of Aurora-A and increased cell cycling in mammary tumors, which was corroborated in breast cancer tissues from patients. Reactivating this pathway using fimepinostat, which relieves inhibitory signaling directed at PTEN and increases FBXW7 expression, combined with inhibiting Aurora-A with alisertib, suppressed breast cancer cell proliferation in culture and tumor growth in vivo. The findings demonstrate a therapeutically exploitable, tumor-suppressive role for eEF1A2 in breast cancer.

CACNA1A variants may modify the epileptic phenotype of Dravet syndrome.

Dravet syndrome is an intractable epileptic syndrome beginning in the first year of life. De novo mutations of SCN1A, which encode the Na(v)1.1 neuronal voltage-gated sodium channel, are considered the major cause of Dravet syndrome. In this study, we investigated genetic modifiers of this syndrome. We performed a mutational analysis of all coding exons of CACNA1A in 48 subjects with Dravet syndrome. To assess the effects of CACNA1A variants on the epileptic phenotypes of Dravet syndrome, we compared clinical features in two genotype groups: 1) subjects harboring SCN1A mutations but no CACNA1A variants (n=20) and 2) subjects with SCN1A mutations plus CACNA1A variants (n=20). CACNA1A variants detected in patients were studied using heterologous expression of recombinant human Ca(v)2.1 in HEK 293 cells and whole-cell patch-clamp recording. Nine CACNA1A variants, including six novel ones, were detected in 21 of the 48 subjects (43.8%). Based on the incidence of variants in healthy controls, most of the variants seemed to be common polymorphisms. However, the subjects harboring SCN1A mutations and CACNA1A variants had absence seizures more frequently than the patients with only SCN1A mutations (8/20 vs. 0/20, p=0.002). Moreover, the former group of subjects exhibited earlier onset of seizures and more frequent prolonged seizures before one year of age, compared to the latter group of subjects. The electrophysiological properties of four of the five novel Ca(v)2.1 variants exhibited biophysical changes consistent with gain-of-function. We conclude that CACNA1A variants in some persons with Dravet syndrome may modify the epileptic phenotypes.

Identification of direct targets for the miR-17-92 cluster by proteomic analysis.

MicroRNAs (miRNAs) are small non-coding RNAs that post-transcriptionally repress the expression of target genes. Many miRNAs have been implicated in a number of diseases, including cancers. The miR-17-92 miRNA cluster is known as a body of oncogenic miRNAs, and has been shown to be overexpressed in several cancers, including lung cancer. Although the overexpression of miR-17-92 is clearly implicated in the development of lung cancer, only a few direct targets for the miR-17-92 cluster have been identified thus far. In this study, we examined miR-17-92 target profiles in SBC-3 small-cell lung cancer cells using a quantitative proteomic strategy to identify direct targets of the miR-17-92 cluster. By knocking down the expression of endogenous miR-19a, miR-20a and miR-92-1, which are contained in the cluster, 112 up-regulated proteins were detected and also identified as potential targets of these miRNAs. Among these candidate targets, we validated one direct target, RAB14. In conclusion, these findings suggest that proteomic approaches are valuable for identifying direct miRNA targets, and we were able to identify a novel direct target for the miR-92-1 using our proteomic strategy.

Human NINEIN polymorphism at codon 1111 is associated with the risk of colorectal cancer.

NINEIN serves an essential role in centrosome function as a microtubule organizing center, and in the reformation of the interphase centrosome architecture following mitosis. In the present study, the association between NINEIN Pro1111Ala (rs2236316), a missense single nucleotide polymorphism, and the risk of colorectal cancer (CRC), related to smoking and alcohol consumption habits in 200 patients with CRC and 1,141 cancer-free control participants were assessed in a case-control study performed in Japan. The results showed that the NINEIN Ala/Ala genotype compared with the Pro/Pro genotype was significantly more associated with an increased risk of CRC, and the males with the Ala/Ala genotype exhibited a significantly increased risk of CRC compared with those with Pro/Pro and Pro/Ala genotypes. Stratified analyses of the Ala/Ala genotype with CRC risk further showed an increased association in never/light drinkers (<23 g of ethanol/day), in male never/light drinkers and in male patients with rectal cancer. These findings suggest that the genetic variant of the NINEIN Pro1111Ala polymorphism has a significant effect on CRC susceptibility in the Japanese population.

Multiple splicing variants of Naf1/ABIN-1 transcripts and their alterations in hematopoietic tumors.

Naf1 (Nef-associated factor 1)/TNIP1/ABIN-1 (A20-binding inhibitor of NF-kappaB activation) is a cellular protein that interacts and cooperates with the NFkappaB inhibiting protein A20. It is reported that Naf1 attenuates epidermal growth factor (EGF)/extracellular-signal-regulated kinase2 (ERK2) nuclear signaling. Naf1 also binds to Nef, which plays a key role in acquired immunodeficiency syndrome pathogenesis and HIV-1 virus replication. Naf1 mRNA consists of 18 exons and multiple splice variants have been reported; two isoforms for exon 1, deletion of exon 2 and isoforms alpha and beta for exon 18. Using specimens from 29 acute myeloid leukemia (AML) patients, we detected a high frequency of allelic loss on DNA at STS marker D5S2014 near the Naf1 gene. We therefore performed mutation and expression analyses using leukemia-lymphoma lines and 6 pairs of clinical AML samples. There was no mutation in the Naf1 coding region of any sample. As a result of expression analysis, we identified novel splice variants of the Naf1 gene; deletion of exon 16 (Naf1 alpha2, Naf1 beta2), deletion of exon 16 with an insertion (Naf1 alpha3, Naf1 beta3) and deletion of exons 16 and 17 (Naf1 alpha4). Naf1 alpha3 and beta3 showed premature termination. In peripheral blood mononucleocytes (PBMNCs) from healthy adults, almost no expression of full-length Naf1 (Naf1FL), Naf1 alpha3 and beta3 were observed. In contrast, their expression was clear in AML blasts and in the majority of leukemia-lymphoma lines investigated. Naf1 alpha2 was widely expressed in PBMNCs from healthy adults, AML blasts and cell lines, suggesting it is the main transcript of the Naf1 gene. Luciferase assay revealed that Naf1 alpha2 had equal NF-kappaB inhibitory effect to that of Naf1FL, while Naf1 alpha4 was less effective. In clinical AML patients, the expression of Naf1 alpha3 was much higher at diagnosis than on remission after chemotherapy, suggesting the possible dominant negative effect of Naf1 alpha3.

Highly frequent allelic loss of chromosome 6q16-23 in osteosarcoma: involvement of cyclin C in osteosarcoma.

The molecular pathogenesis of osteosarcoma is very complicated and associated with chaotic abnormalities on many chromosomal arms. We analyzed 12 cases of osteosarcomas with comparative genomic hybridization (CGH) to identify chromosomal imbalances, and detected highly frequent chromosomal alterations in chromosome 6q, 8p, 10p and 10q. To define the narrow rearranged region on chromosome 6 with higher resolution, loss of heterozygosity (LOH) analysis was performed with 21 microsatellite markers. Out of 31 cases, 23 cases (74%) showed allelic loss at least with one marker on chromosome 6q. We identified two distinct commonly deleted regions on chromosome 6 using markers D6S1565 located at 6q16 and 6q23MS1 at 6q23. The expression analysis of genes located at the deleted region was performed, and the decreased mRNA expression of the CCNC gene, one of the regulators of cell cycle, was detected. Growth of osteosarcoma cell line was significantly suppressed after the CCNC cDNA transfection. Fine mapping of the deleted region containing a possible tumor suppressor gene and the transfection assay suggest that the CCNC is a candidate tumor suppressor gene.

Allelic loss and reduced expression of the ING3, a candidate tumor suppressor gene at 7q31, in human head and neck cancers.

Loss of heterozygosity (LOH) has been frequently detected at chromosome 7q31 region in human head and neck squamous cell carcinomas (HNSCC) and many other cancers, suggesting the existence of tumor suppressor genes (TSG). We analysed LOH at 7q31 region in 49 HNSCC by using six polymorphic microsatellite markers and found allelic deletion in 48% (22/46) of the informative cases. We detected two preferentially deleted regions, one is around D7S643 and the other around D7S486. When we redefined the map of 7q31 region according to the contiguous sequences, a recently identified gene, ING3, was found in the proximity of D7S643. ING3 protein harbors the PHD domain highly homologous among ING family proteins, in which we previously found mutations in a related gene, ING1. As only one missense mutation of the ING3 gene was found in HNSCC, we examined the expression level. Reverse-transcription-PCR analysis demonstrated decreased or no expression of ING3 mRNA in 50% of primary tumors as compared with that of matched normal samples. Especially, about 63% of tongue and larynx tumors showed the decrease and a tendency of higher mortality was observed in cases with decreased ING3 expression. All these findings suggest a possibility that the ING3 gene functions as a TSG in a subset of HNSCC.

Significant growth suppression of synovial sarcomas by the histone deacetylase inhibitor FK228 in vitro and in vivo.

About 97% of synovial sarcomas harbor the SYT-SSX fusion gene by chromosomal translocation. We found that the histone deacetylase (HDAC) inhibitor FK228 significantly suppressed the growth of synovial sarcoma cells as compared with that of osteosarcoma. The 50% growth inhibition IC50 value we obtained for FK228 was 0.02-0.2 nM, and it indicates that its suppression effect on synovial sarcoma cells is the highest of any of the HDAC inhibitors yet reported. It was not likely that the growth suppression of FK228 depends on the doubling time of these cells. Introduction of SYT-SSX cDNA into HEK293 cells enhanced the sensitivity of the cells for FK228. Immunostaining of the FK228-treated cells using an anti-acetyl-histone H3 antibody showed that FK228 inhibits deacetylation of histone. In a mice assay, the growth of synovial sarcoma cells was markedly inhibited by FK228 treatment, and the invasion of tumors into surrounding tissues was suppressed. These results suggest that FK228 may be useful in developing therapeutic strategies to treat synovial sarcoma.

Novel direct targets of miR-19a identified in breast cancer cells by a quantitative proteomic approach.

The miR-17-92 cluster encodes 7 miRNAs inside a single polycistronic transcript, and is known as a group of oncogenic miRNAs that contribute to tumorigenesis in several cancers. However, their direct targets remain unclear, and it has been suggested that a single miRNA is capable of reducing the production of hundreds of proteins. The majority of reports on the identification of miRNA targets are based on computational approaches or the detection of altered mRNA levels, despite the fact that most miRNAs are thought to regulate their targets primarily by translational inhibition in higher organisms. In this study, we examined the target profiles of miR-19a, miR-20a and miR-92-1 in MCF-7 breast cancer cells by a quantitative proteomic strategy to identify their direct targets. A total of 123 proteins were significantly increased after the endogenous miR-19a, miR-20a and miR-92-1 were knocked down, and were identified as potential targets by two-dimensional electrophoresis and a mass spectrometric analysis. Among the upregulated proteins, four (PPP2R2A, ARHGAP1, IMPDH1 and NPEPL1) were shown to have miR-19a or miR-20a binding sites on their mRNAs. The luciferase activity of the plasmids with each binding site was observed to decrease, and an increased luciferase activity was observed in the presence of the specific anti-miRNA-LNA. A Western blot analysis showed the expression levels of IMPDH1 and NPEPL1 to increase after treatment with anti-miR-19a, while the expression levels of PPP2R2A and ARHGAP1 did not change. The expression levels of IMPDH1 and NPEPL1 did not significantly change by anti-miR-19a-LNA at the mRNA level. These results suggest that the IMPDH1 and NPEPL1 genes are direct targets of miR-19a in breast cancer, while the exogenous expression of these genes is not associated with the growth suppression of MCF-7 cells. Furthermore, our proteomic approaches were shown to be valuable for identifying direct miRNA targets.

Rasmussen encephalitis associated with SCN 1 A mutation.

Mutations in the SCN 1 A gene, encoding the neuronal voltage-gated sodium channel alpha1 subunit, cause SMEI, GEFS+, and related epileptic syndromes. We herein report the R1575C-SCN 1 A mutation identified in a patient with Rasmussen encephalitis. R1575C were constructed in a recombinant human SCN 1 A and then heterologously expressed in HEK293 cells along with the human beta1 and beta2 sodium channel accessory subunits. Whole-cell patch-clamp recording was used to define biophysical properties. The R1575C channels exhibited increased channel availability and an increased persistent sodium current in comparison to the wild-type. These defects of electrophysiological properties can result in neuronal hyperexitability. The seizure susceptibility allele may influence the pathogenesis of Rasmussen encephalitis in this case.

SYT, a partner of SYT-SSX oncoprotein in synovial sarcomas, interacts with mSin3A, a component of histone deacetylase complex.

Synovial sarcomas are soft-tissue tumors predominantly affecting children and young adults. They are molecular-genetically characterized by the SYT-SSX fusion gene generated from chromosomal translocation t(X; 18) (p11.2; q11.2). When we screened new gene products that interact with SYT or SSX proteins by yeast two-hybrid assay, we found that mSin3A, a component of the histone deacetylase complex, interacts with SYT but not with SSX. These results were confirmed by mammalian two-hybrid and pull-down assays. Analyses with sequential truncated proteins revealed a main mSin3A-interaction region on the SYT amino-terminal 93 amino acids, and another one on the region between 187th amino acid and break point. In luciferase assay, mSin3A repressed the transcriptional activity of reporter promoter mediated by SYT and hBRM/BRG1. Our results suggest that the histone deacetylase complex containing mSin3A may regulate the transcriptional activation mediated by SYT.