Expression of mos in astrocytic tumors and its potential role in neoplastic progression

Role of MEK partner-1 in cancer stemness through MEK/ERK pathway in cancerous neural stem cells, expressing EGFRviii

Background

Glioma stem cells (GSCs) are a major cause of the frequent relapse observed in glioma, due to their high drug resistance and their differentiation potential. Therefore, understanding the molecular mechanisms governing the ‘cancer stemness’ of GSCs will be particularly important for improving the prognosis of glioma patients.

Methods

We previously established cancerous neural stem cells (CNSCs) from immortalized human neural stem cells (F3 cells), using the H-Ras oncogene. In this study, we utilized the EGFRviii mutation, which frequently occurs in brain cancers, to establish another CNSC line (F3.EGFRviii), and characterized its stemness under spheroid culture.

Results

The F3.EGFRviii cell line was highly tumorigenic in vitro and showed high ERK1/2 activity as well as expression of a variety of genes associated with cancer stemness, such as SOX2 and NANOG, under spheroid culture conditions. Through meta-analysis, PCR super-array, and subsequent biochemical assays, the induction of MEK partner-1 (MP1, encoded by the LAMTOR3 gene) was shown to play an important role in maintaining ERK1/2 activity during the acquisition of cancer stemness under spheroid culture conditions. High expression of this gene was also closely associated with poor prognosis in brain cancer.

Conclusion

These data suggest that MP1 contributes to cancer stemness in EGFRviii-expressing glioma cells by driving ERK activity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0703-y) contains supplementary material, which is available to authorized users.

DNA-PK target identification reveals novel links between DNA repair signaling and cytoskeletal regulation

The DNA-dependent protein kinase (DNA-PK) may function as a key signaling kinase in various cellular pathways other than DNA repair. Using a two-dimensional gel electrophoresis approach and stable DNA double-strand break-mimicking molecules (Dbait32Hc) to activate DNA-PK in the nucleus and cytoplasm, we identified 26 proteins that were highly phosphorylated following DNA-PK activation. Most of these proteins are involved in protein stability and degradation, cell signaling and the cytoskeleton. We investigated the relationship between DNA-PK and the cytoskeleton and found that the intermediate filament (IF) vimentin was a target of DNA-PK in vitro and in cells. Vimentin was phosphorylated at Ser459, by DNA-PK, in cells transfected with Dbait32Hc. We produced specific antibodies and showed that Ser459-P-vimentin was mostly located at cell protrusions. In migratory cells, the vimentin phosphorylation induced by Dbait32Hc was associated with a lower cellular adhesion and migration capacity. Thus, this approach led to the identification of downstream cytoplasmic targets of DNA-PK and revealed a connection between DNA damage signaling and the cytoskeleton.

Gain of chromosome 8q is a frequent finding in pleuropulmonary blastoma

Pleuropulmonary blastomas are rare malignant intrathoracic tumors of early childhood. They appear as a pulmonary- and/or pleural-based mass and their pathogenesis and relationship to other pediatric solid tumors is not well understood. In this study, paraffin-embedded material of five cases of pleuropulmonary blastoma was analyzed for genetic alterations by comparative genomic hybridization and five genetic loci by fluorescence in situ hybridization. Comparative genomic hybridization identified aberrations in all pleuropulmonary blastomas, including four amplifications in three tumors at chromosomes 5q33-34, 11q22.2-ter, 15q25-ter, and 19q11-13.2. The most frequent DNA gains involved 8q11-22.2 (four cases) and 20q (two cases), whereas the most common losses included 9p21-24 (two cases) and 11p14 (three cases). Chromosome 8 gains were confirmed by fluorescent in situ hybridization, resulting in the detection of up to five copies of chromosome 8 centromeres per nucleus. In the two surviving patients, chromosome 8 gains were the only genetic abnormality, suggesting that this might be an early event in pleuropulmonary blastoma carcinogenesis. The identification of new genetic alterations as well as the confirmation of previously reported ones (especially 8q gains) in pleuropulmonary blastoma should help to improve our understanding of both the molecular mechanisms underlying the tumorigenesis of pleuropulmonary blastoma and the relationship of pleuropulmonary blastoma with other pediatric tumors.

Differences in effects of oncogenes on sensitivity to anticancer drugs

Methods to predict the responsiveness of a particular tumor to a particular anticancer drug are desirable not only for chemotherapy but also for chemoradiotherapy. Here, we examined the effects of viral or activated oncogenes on sensitivity to anticancer drugs by using SHOK (Syrian hamster Osaka-Kanazawa) cells and their transfectants. The IC50 of each transfectant was compared with that of the pSV2Neo transfected control. Cells transfected with the c-myc, v-mos, or v-fgr gene increased their sensitivity to bleomycin, while those transfected with the H-ras gene developed resistance. Resistance to cisplatin was conferred by the introduction of the H-ras or c-cot gene. In the case of adriamycin, the c-myc or c-cot transfectant increased sensitivity and the H-ras transfectant decreased it. Mitomycin C resistance was observed by the introduction of the K-ras gene. Thus, the H-ras gene was found to be involved in the development of resistance to three of the four anticancer drugs. In addition, we have for the first time shown that mos and cot have an effect on sensitivity to three and all of the four anticancer drugs, respectively. These results suggest that the expression of each oncogene would differently affect sensitivity to the four anticancer drugs used in this study, and this property could be a possible marker to predict chemosensitivity.

c-mos Immunoreactivity Aids in the Diagnosis of Gestational Trophoblastic Lesions

C-mos is an important proto-oncogene involved in the mitogen-activating protein kinase pathway. This study was designed to explore c-mos immunoreactivity in gestational trophoblastic lesions and compare it with immunoreactivity in normal placentas as well as other gynecological lesions and germ cell tumors using antibody P-19. The immunohistochemical distribution of c-mos in 159 cases of gynecological lesions and 26 germ cell tumors using formalin-fixed, paraffin-embedded tissues was evaluated. The lesions included 45 (32 complete and 13 partial) hydatidiform moles, 17 choriocarcinomas, 5 placental site trophoblastic tumors, 18 squamous cell carcinomas and 5 adenocarcinomas of the cervix, 11 endometrial carcinomas, 9 ovarian carcinomas, 4 primary peritoneal papillary serous carcinomas, 9 low-grade endometrial stromal sarcomas, 4 epithelioid leiomyomas, 6 leiomyosarcomas, and 26 gem cell tumors (3 embryonal carcinomas, 5 yolk sac tumors, 6 immature teratomas, and 3 mature teratomas from the ovary; 9 testicular seminomas). Twenty-six normal placentas also were included for comparison. Among cases of gestational trophoblastic diseases, c-mos immunoreactivity was found in all hydatidiform moles and choriocarcinomas, but in none of the placental site trophoblastic tumors. The c-mos staining pattern was similar in trophoblastic diseases and normal placentas with strong expression in syncytiotrophoblast, moderate expression in villous intermediate trophoblast, and predominantly negative expression in implantation site intermediate trophoblast, chorionic-type intermediate trophoblast, and villous cytotrophoblast. All the nontrophoblastic tumors, including carcinomas, sarcomas, and germ cell tumors, were negative for c-mos expression. Immunohistochemical detection of c-mos is useful in differentiating choriocarcinoma from placental site trophoblastic tumor and nontrophoblastic tumors of the female genital tract that may sometimes cause problems in differential diagnosis.

Neuronal expression of cell cycle-related proteins after brain ischaemia in man

The death of neurons after brain ischaemia may be associated with activation of cyclin-dependent kinases (CDKs) and upregulation of cyclins, reflecting aberrant entry of neurons into the cell cycle. Little has been published on the expression of cell cycle proteins after brain ischaemia in man. Well-characterized antisera were therefore used to examine the neuronal expression of CDK2, CDK4 and cyclins A, D1 and E in sections of brain from patients who had experienced cardiac arrest or focal brain infarction, and died 3.5 h to 9 days later. Scattered neurons contained elevated levels of cyclin D1, CDK2 and, to a lesser extent, CDK4, but little or no cyclin A or E. Present findings indicate that brain ischaemia induces the entry of some neurons from G0 into the G1 phase of the cell cycle, and suggest a potential therapeutic role for CDK inhibitors in ischaemic stroke.

Medulloblastoma sensitivity to 17-allylamino-17-demethoxygeldanamycin requires MEK/ERKM

ERBB2 increases the sensitivity of breast cancer cells to the HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG). This has been attributed to the disruption of ERBB3/ERBB2 heterodimers that maintain a crucial cell survival signal via phosphatidylinositol 3-kinase/AKT. ERBB2 confers a poor clinical outcome in medulloblastoma, the most common malignant pediatric brain tumor. Here, we show that medulloblastoma cell sensitivity to 17-AAG is directly related to ERBB2 expression level. Furthermore, overexpression of exogenous ERBB2 in these cells induces spontaneous homodimerization, further enhancing cell sensitivity to 17-AAG. In contrast to breast cancer cells, this increased sensitivity to 17-AAG does not result from cell dependence on AKT1 activity. Rather, we show that 17-AAG generates a dose- and time-dependent increase in MEK/ERK signaling that is required for the drug to inhibit the proliferation of medulloblastoma cells and that ERBB2 sensitizes medulloblastoma cells to 17-AAG by up-regulating basal MEK/ERK signaling. We further show that down-regulation of MEK1 activity markedly reduces the sensitivity of medulloblastoma, breast, and ovarian cancer cells to 17-AAG, whereas expression of a constitutively active MEK1 potentiates the activity of 17-AAG against these cells. Therefore, intact MEK/ERK signaling may be required for optimal 17AAG activity against a variety of tumor cell types. These data identify a new mechanism by which 17-AAG inhibits the proliferation of cancer cells. Defining the precise mode of action of these agents within specific tumor cell types will be crucial if this class of drugs is to be efficiently developed in the clinic.