Differentially expressed genes in association with in vitro invasiveness of human epithelioid sarcoma

STRIPAK complexes: structure, biological function, and involvement in human diseases

The mammalian striatin family consists of three proteins, striatin, S/G2 nuclear autoantigen, and zinedin. Striatin family members have no intrinsic catalytic activity, but rather function as scaffolding proteins. Remarkably, they organize multiple diverse, large signaling complexes that participate in a variety of cellular processes. Moreover, they appear to be regulatory/targeting subunits for the major eukaryotic serine/threonine protein phosphatase 2A. In addition, striatin family members associate with germinal center kinase III kinases as well as other novel components, earning these assemblies the name striatin-interacting phosphatase and kinase (STRIPAK) complexes. Recently, there has been a great increase in functional and mechanistic studies aimed at identifying and understanding the roles of STRIPAK and STRIPAK-like complexes in cellular processes of multiple organisms. These studies have identified novel STRIPAK and STRIPAK-like complexes and have explored their roles in specific signaling pathways. Together, the results of these studies have sparked increased interest in striatin family complexes because they have revealed roles in signaling, cell cycle control, apoptosis, vesicular trafficking, Golgi assembly, cell polarity, cell migration, neural and vascular development, and cardiac function. Moreover, STRIPAK complexes have been connected to clinical conditions, including cardiac disease, diabetes, autism, and cerebral cavernous malformation. In this review, we discuss the expression, localization, and protein domain structure of striatin family members. Then we consider the diverse complexes these proteins and their homologs form in various organisms, emphasizing what is known regarding function and regulation. Finally, we explore possible roles of striatin family complexes in disease, especially cerebral cavernous malformation.

HFE polymorphisms influence the response to chemotherapeutic agents via induction of p16INK4A

HFE is a protein that impacts cellular iron uptake. HFE gene variants are identified as risk factors or modifiers for multiple diseases. Using HFE stably transfected human neuroblastoma cells, we found that cells carrying the C282Y HFE variant do not differentiate when exposed to retinoic acid. Therefore, we hypothesized HFE variants would impact response to therapeutic agents. Both the human neuroblastoma and glioma cells that express the C282Y HFE variant are resistant to Temodar, geldanamycin and γ-radiation. A gene array analysis revealed that p16INK4A (p16) expression was increased in association with C282Y expression. Decreasing p16 protein by siRNA resulted in increased vulnerability to all of the therapeutic agents suggesting that p16 is responsible for the resistance. Decreasing HFE expression by siRNA resulted in a 85% decrease in p16 expression in the neuroblastoma cells but not the astrocytoma cells. These data suggest a potential direct relationship between HFE and p16 that may be cell specific or mediated by different pathways in the different cell types. In conclusion, the C282Y HFE variant impacts the vulnerability of cancer cells to current treatment strategies apparently by increasing expression of p16. Although best known as a tumor suppressor, there are multiple reports that p16 is elevated in some forms of cancer. Given the frequency of the HFE gene variants, as high as 10% of the Caucasian population, these data provide compelling evidence that the C282Y HFE variant should be part of a pharmacogenetic strategy for evaluating treatment efficacy in cancer cells.

Brain slice invasion model reveals genes differentially regulated in glioma invasion

Invasion of tumor cells into adjacent brain areas is one of the major problems in treatment of glioma patients. To identify genes that might contribute to invasion, fluorescent F98 glioma cells were allowed to invade an organotypic brain slice. Gene expression analysis revealed 5 up-regulated and 14 down-regulated genes in invasive glioma cells as compared to non-invasive glioma cells. Two gene products, ferritin and cyclin B1, were verified in human gliomas by immunohistochemistry. Ferritin exhibited high mRNA levels in migratory F98 cells and also showed higher protein expression in the infiltrating edge of human gliomas. Cyclin B1 with high mRNA expression levels in stationary F98 cells showed marked protein expression in the central portions of gliomas. These findings are compatible with the concept of tumor cells either proliferating or migrating. Our study is the first to apply brain slice cultures for the identification of differentially regulated genes in glioma invasion.

Ferritin contributes to melanoma progression by modulating cell growth and sensitivity to oxidative stress

PURPOSE

Employing an in vitro model system of human melanoma progression, we previously reported ferritin light chain (L-ferritin) gene overexpression in the metastatic phenotype. Here, we attempted to characterize the role of ferritin in the biology of human melanoma and in the progression of this disease.

EXPERIMENTAL DESIGN

Starting from the LM human metastatic melanoma cell line, we engineered cell clones in which L-ferritin gene expression was down-regulated by the stable expression of a specific antisense construct. These cells were then assayed for their growth capabilities, chemoinvasive properties, and sensitivity to oxidative stress. Additionally, ferritin protein content in primary and metastatic human melanomas was determined by immunohistochemistry.

RESULTS

Artificial L-ferritin down-regulation in the LM cells strongly inhibited proliferation and chemoinvasion in vitro and cell growth in vivo. In addition, L-ferritin down-regulated cells displayed enhanced sensitivity to oxidative stress and to apoptosis. Concurrently, immunohistochemical analysis of a human melanoma tissue array revealed that ferritin expression level in metastatic lesions was significantly higher (P < 0.0001) than in primary melanomas. Furthermore, ferritin expression was constantly up-regulated in autologous lymph node melanoma metastases when compared with the respective primary tumors in a cohort of 11 patients.

CONCLUSIONS

These data suggest that high ferritin expression can enhance cell growth and improve resistance to oxidative stress in metastatic melanoma cells by interfering with their cellular antioxidant system. The potential significance of these findings deserves to be validated in a clinical setting.

Identification of multiple differentially expressed messenger RNAs in normal and pathological trophoblast

In an attempt to assess the molecular basis of phenotypic alterations present in the gestational trophoblastic diseases (GTDs) and to identify genes whose expression is specifically associated to these placental proliferative disorders we performed differential display techniques. Initially 19 candidate gene fragments were identified and differential expression was confirmed in eight of these fragments by Northern blot analysis. At the mRNA level ribosomal L26 (rL26), ribosomal L27 (rL27), a new Krüppel type zinc finger protein and TIS11d were preferentially expressed in normal early placenta (NEP) relative to complete hydatidiform mole (CHM), persistent gestational trophoblastic disease (PGTD) and choriocarcinoma JEG-3 cell line. In contrast, heterogeneous ribonucleoprotein A1 (hnRNPA1), the ferritin light chain mRNA, and the uncharacterized protein KIAA0992 were predominantly expressed in JEG-3 cell line. Finally, decorin, a prototype member of an expanding family of small leucine-rich proteoglycans, showed high expression in CHM. In addition we demonstrated by immunohistochemistry analysis that increased decorin mRNA in CHM reflected a genuine augmentation in average steady state mRNA levels within cells. Taken together, these findings provide several interesting candidates for regulation of tumorigenic expression as well as early placentation development, including those involved in protein synthesis (rL26 and rL27), metabolism (ferritin light chain), intercellular communication (decorin) and regulation of gene expression (Krüppel-like zinc finger, TIS11d and hnRNPA1). Information about such alterations in gene expression could be useful for elucidating the genetic events associated to gestational trophoblastic pathogenesis, developing new diagnostic markers, or determining novel therapeutic targets.

Screening and expression of associated genes in gastric dysplasia

AIM: To explore molecular mechanism of gastric carcinogenesis, we screened associated genes of gastric dysplasia and further investigated their expression in gastric carcinomas with different stages.

METHODS: Relatively pure dysplasia and normal tissue were procured by manual microdissection, amplified by cDNA-PCR, and then used to carry out forward(dysplasia as tester, normal tissue as driver) and reverse(normal tissue as tester, dysplasia as driver) SSH. Subtracted cDNA fragments were cloned into vector, screened, sequenced, and made homologous analysis. The expression of differentially expressed fragments was detected and verified by Dot hybridization and reverse transcription-PCR.

RESULTS: Two subtracted cDNA libraries were constructed. Twenty-one of 26 sequenced clones were verified to be expressed differentially. It was noted that differentiall expressions of 4 genes(P125, cytochrome c oxidase subunit I, meprin A, acidic calponin)were detected simultaneously in dysplasia, early cancer and advanced cancer.

CONCLUSION: Four new associated genes have been identified in dysplasia. Further studies are necessary to determine their roles in gastric carcinogenesis.