Recurrent somatic mutations in MED12 exon 2 have recently been reported in uterine leiomyomas. The recurrent nature of the mutations strongly suggests that the mutations may play important roles in the pathogenesis of uterine leiomyomas. The aim of our study was to see whether MED12 exon 2 mutations occur in other human tumors besides uterine leiomyomas. We also attempted to confirm occurrence of the MED12 mutations in uterine leiomyomas of Korean patients. For this, we analyzed 1,862 tumor tissues, including a variety of carcinomas, leukemias and stromal tumors by single-strand conformation polymorphism analysis. We found MED12 mutations in 35 uterine leiomyomas (35/67; 52.2%) and one colon carcinoma (0.3%), but none in other tumors. The MED12 mutations consisted of missense (77%) and inframe insertion-deletion (23%) mutations, the pattern of which was similar to the earlier report. Our data indicate that MED12 exon 2 mutations may be tissue-specific to uterine leiomyoma and rare in other tumors. Our study suggests that the MED12 mutations play unique roles in the pathogenesis of uterine leiomyomas and mutated MED12 could be therapeutically targeted in uterine leiomyomas.For a comprehensive elucidation of genetic alterations in uterine leiomyoma, M€ akinen et al. 1 recently examined uterine leiomyoma tissues by exome sequencing. They identified somatic mutations of mediator complex subunit 12 (MED12; MIM *300188) gene in 159 of 225 uterine leiomyomas (71%). Of note, the mutations were clustered in exon 2, and consisted of missense mutations substituting the Gly residue in codon 44 (49%), inframe insertion-deletion mutations to affecting amino acid residues 33-54 (11%), and other missense mutations besides codon 44. A following study using other uterine leiomyomas from South African patients confirmed a similar pattern of the MED12 exon 2 mutations. 2 Another study identified that MED12 mutation in uterine leiomyoma was mostly associated with normal karyotype of the tumors. 3 Also, the tumors with MED12 mutation expressed high levels of WNT4 mRNA, suggesting a possibility that the MED12 mutation might be involved in activation of Wnt pathway. 3 MED12 is a component of the mediator complex that has a regulatory role in RNA polymerase II activity. 4 MED12 has roles in both transcriptional activation and repression, and is involved in many developmental processes. 5 Germline mutations of MED12 have been reported in Opitz-Kaveggia and Lujan-Fryns syndromes that are characterized by congenital anomalies and intellectual disability. 5 However, alterations of MED12 gene in neoplastic diseases except uterine leiomyomas have not been reported. Evidence exists that the Mediator complex performs both general and gene-specific roles to regulate gene expression. 5,6 Moreover, despite the high incidence of MED12 mutation in leiomyomas, functional roles of the mutation in tumorigenesis remain unknown. Together, these data suggest a possibility that mutational events in MED12 exon 2 might be involved in other tumors.One of the ...

Mounting evidence exists that alterations of ubiquitination processes are involved in cancer pathogenesis. Speckle-type POZ protein (SPOP) is a key adaptor for Cul3-based ubiquitination process. Recent studies reported that SPOP may be a tumor suppressor gene (TSG) and somatic mutation of SPOP was detected in prostate cancer (PCA). The aim of this study was to see whether alterations of SPOP protein expression and somatic mutation of SPOP gene are features of cancers. In this study, we analyzed SPOP somatic mutation in 45 gastric (GC), 45 colorectal cancer (CRC) and 45 PCA by single-strand conformation polymorphism (SSCP). Also, we analyzed SPOP protein expression in 60 GC, 60 CRC and 60 PCA by immunohistochemistry. Overall, we detected three somatic missense mutations of SPOP gene in the coding sequences (p.Ser14Leu, p.Tyr87Cys and p.Phe133Leu). The mutations were observed in two PCA and one CRC. Of note, the p.Phe133Leu was a recurrent mutation reported in an earlier study. In the immunohistochemistry, SPOP protein was expressed in normal gastric, colonic and prostate epithelial cells, whereas it was lost in 30% of GC, 20% of CRC and 37% of PCA. Our data indicate that loss of SPOP expression was common in GC, CRC and PCA, but somatic mutation of SPOP in this study was rare in these tumors. Also, the data provide a possibility that loss of expression of SPOP gene might play a role in cancer pathogenesis by altering TSG functions of SPOP.

Recurrent somatic mutations in splicing machinery components, including SF3B1, U2AF1 and SRSF2 genes have recently been reported in myelodysplastic syndromes (MDS). Such a recurrent nature strongly suggests that these mutations play important roles in tumor development. To see whether SF3B1, U2AF1 and SRSF2 mutations occur in other human tumors besides MDS, we analyzed the hotspot mutation regions of these genes in 2,345 tumor tissues from various origins (61 MDS, other 616 hematologic tumors, 1,421 epithelial tumors and 247 non-epithelial stromal tumors) by single-strand conformation polymorphism analysis. We found SF3B1, U2AF1 and SRSF2 mutations in 5 (8.2%), 12 (19.7%) and 8 (13.1%) of 61 MDS, respectively. We also confirmed these mutations in other myeloid neoplasia, including de novo acute myelogenous leukemia (AML), chronic myelomonocytic leukemia and MDS/myeloproliferative disorder. In addition, we discovered that the SRSF2 gene was mutated in two childhood acute lymphoblastic leukemias (childhood ALL) (1.5%). In solid tumors, we found SF3B1 mutations in gastric and prostate cancers, and U2AF1 mutation in a borderline mucinous tumor of ovary, but the overall incidences of the hotspot mutation regions were very low (0.2%). Our data suggest that SF3B1, U2AF1 and SRSF2 mutations occur not only in myeloid lineage tumors but also in lymphoid lineage tumors. The data suggest that the splicing gene mutations play important roles in the pathogenesis of hematologic tumors, but rarely in solid tumors.Myelodysplastic syndromes (MDS) are a diverse collection of hematological conditions that are characterized by ineffective production of blood cells and an increased risk of progression to acute leukemias. MDS is thought to arise from mutations in bone marrow stem cells, but the specific defects responsible for these diseases remain poorly understood. 1,2For a comprehensive elucidation of genetic alterations in MDS, Yoshida et al.3 recently analyzed bone marrows of patients with MDS by a whole-exome sequencing. They identified frequent somatic mutations of genes encoding multiple components of RNA splicing machinery, including splicing factor 3B subunit 1 (SF3B1), serine/arginine-rich splicing factor 2 (SRSF2) and U2 small nuclear RNA auxiliary factor 1 (U2AF1). Mutations in these genes were detected in diverse subtypes of MDS and MDS-related disorders (chronic myelomonocytic leukemia (CMML) and MDS-derived acute myelogenous leukemia (AML)).3 Following studies not only confirmed these mutations in MDS, but also identified them in other hematologic diseases (de novo AML, myeloproliferative disorders and chronic lymphocytic leukemia (CLL)). [3][4][5][6][7] In addition, SF3B1 somatic mutations have been found in some solid tumor tissues (breast, kidney, salivary gland and prostate) although less commonly than in MDS. 4,8,9 Recurrent U2AF1 mutations have been reported in lung adenocarcinomas. 10RNA splicing is a mechanism for gene regulation and proteome diversity, and is ubiquitous to all types of human cells. 11Moreover,...

Cadherins (CDHs) are important in maintenance of cell adhesion and polarity, alterations of which contribute to tumorigenesis. Alterations of E-cadherin, a prototype CDH, have been reported in many cancers. However, alterations of unconventional CDHs, including CDH10, CDH24 and DCHS2 are largely unknown in cancers. Aim of this study was to explore whether CDH10, CDH24 and DCHS2 genes are mutated in gastric (GC) and colorectal cancers (CRC). In a public database, we found that CDH10, CDH24 and DCHS2 genes had mononucleotide repeats in the coding sequences that might be mutation targets in the cancers with microsatellite instability (MSI). We analyzed the mutations in 89 GC and 131 CRC (high MSI (MSI-H) or stable MSI/low MSI (MSS/MSI-L)) by single-strand conformation polymorphism analysis and DNA sequencing. We found six DCHS2, one CDH10 and one CDH24 frameshift mutations in them. All of the mutations were detected in cancers with MSI-H and there was a statistical difference in the frameshift mutation frequencies between the cancers with MSI-H (8/105) and MSS/MSI-L (0/115). The DCHS2 frameshift mutations were found in 8.8% and 4.2% of GC and CRC with MSI-H respectively. Our results show that unconventional CDH10, CDH24 and DCHS2 genes harbored frameshift mutations. These mutations might inactivate the cell adhesion-related functions and could be a feature of GC and CRC with MSI-H.

Recent studies have revealed several recurrent mutations in oncogenes that could not only be underlying mechanisms of tumorigenesis, but also be potential targets for cancer therapies. Compared to carcinomas, genetic alterations of sarcomas are relatively unknown. To see whether recurrent oncogenes discovered in non-sarcomatous malignancies are present in sarcomas as well, we analyzed oncogenes with known mutations in various types of sarcomas. We performed mutational analysis of recurrent mutation sites of PIK3CA (exons 9 and 20), JAK2 (exon 14), BRAF (exon 15), FOXL2 (exon 1), IDH1 (exon 4), AKT1 (exon 3), and EZH2 (exon 16) genes in 108 sarcomas by single- strand conformation polymorphism and DNA sequencing. The sarcomas consisted of malignant fibrous histiocytomas, rhabdomyosarcomas, osteosarcomas, malignant peripheral nerve sheath tumors, leiomyosarcomas, synovial sarcomas, liposarcomas, angiosarcomas, chondrosarcomas, and Ewing sarcomas. Overall, we detected the two PIK3CA mutations and one JAK2 mutation (total: 3/108: 2.8%). Two rhabdomyosarcomas (16.7%) and one angiosarcoma (16.7%) harbored the mutations, whereas other sarcomas harbored none. The PIK3CA mutations were novel missense mutations that had not been detected in other cancers. The JAK2 mutation was an intron mutation. This study demonstrated that the somatic mutations of PIK3CA and JAK2 occurred in a small fraction of the sarcomas and that these mutations may not play a principal role in the development of sarcomas.