Cloning, sequence, and developmental expression analysis of C4-2, a potential brain tumor-suppressor gene

Transcriptional basis of KRAS oncogene-mediated cellular transformation in ovarian epithelial cells

To understand the relationship between oncogenic signaling and the reprogramming of gene expression, we performed transcriptional profiling in rat ovarian surface epithelial cells (ROSE), in which neoplastic transformation is driven by a mutated KRAS oncogene. We identified >200 genes whose expression was elevated or reduced following permanent KRAS expression. Deregulated KRAS-responsive genes encode transcriptional regulators, signaling effectors, proteases, extracellular matrix and adhesion proteins, transformation-suppressing proteins and negative growth regulators. Many of them have not been previously identified in cells expressing oncogenic RAS genes or in other well-studied models of oncogenic signaling. The number of critical genes related to the execution of anchorage-independent proliferation and epithelial-mesenchymal transition was narrowed down to 79 by selectively inhibiting the mitogen-activated protein kinase (MAPK/ERK) and phosphatidylinositol 3-kinase (PI3K) pathways. Blocking MAPK/ERK-signaling caused reversion to the normal epithelial phenotype in conjunction with the reversal of deregulated target transcription to pretransformation levels. In addition, silencing of the overexpressed transcriptional regulator Fra-1 by RNA interference resulted in growth reduction, suggesting that this factor partially contributes to, but is not sufficient for the proliferative capacity of KRAS-transformed epithelial cells.

Molecular characterization of CXCR-4: a potential brain tumor-associated gene

BACKGROUND AND OBJECTIVES

We have previously reported the isolation of a G protein-coupled receptor, CXCR-4, that is overexpressed in glioblastoma multiforme tumor tissue (GMTT), as compared to normal brain tissue (NBT).

METHODS

Gene-specific RT-PCR, Northern blotting, and in situ hybridization techniques were used to study its expression in a variety of normal tissues, tumor tissues, and cell lines, as well as during development. Antisense CXCR-4 was overexpressed in glioblastoma cells to study its effect on cell proliferation.

RESULTS

Gene-specific RT-PCR analysis indicated that the CXCR-4 gene is overexpressed in several malignant glioma tissues, breast tumor tissues and cell lines. Northern blot analysis indicated that CXCR-4 is expressed at high levels in certain leukemias, uterine cancer, and Burkitt's lymphoma cell line. The occipital and temporal lobe showed high levels of CXCR4 in normal human brain. The CXCR-4 gene was expressed in all organs in the early stages of development (days 8-10). In adult mouse, CXCR-4 is expressed only in brain, spinal cord, bone marrow, and pituitary gland. Antisense CXCR-4 overexpression in glioblastoma cells caused inhibition of cell proliferation and induction of cellular differentiation in vitro. This suggests that CXCR-4 expression may play an important role during embryonic development and also in the genesis of human gliomas.

CONCLUSIONS

On the basis of CXCR4 expression data and antisense overexpression data, we conclude that CXCR-4 plays an important role in the tumorigenic properties of brain, breast, and other tumor types. On the basis of its unique expression during mouse development, we conclude that it may play an important role in the normal functioning of brain, spinal cord, and bone marrow during development.

Molecular changes during the genesis of human gliomas

Neoplastic transformation in the normal human brain occurs as a result of the accumulation of a series of genetic alterations. These genetic alterations include the loss, gain or amplification of different chromosomes which lead to altered expression of proteins that play important roles in the regulation of cell proliferation. Several common genetic alterations at the chromosomal level (loss of 17p, 13q, 9p, 19, 10, 22q, 18q and amplification of 7 and 12q) have been observed. These alterations lead to changes in the expression of several genes; protein 53 (p53), retinoblastoma (RB), interferon (INF) alpha/beta, cyclic AMP dependent kinase number 2 (CDKN2), mutated in multiple advanced cancers 1 (MMAC1), deleted-in-colon carcinoma (DCC), epidermal growth factor receptor (EGFR), platelet derived growth factor (PDGF), platelet derived growth factor receptor (PDGFR), MDM2, GL1, CDK4 and SAS during the genesis and progression of human gliomas. Recent studies suggest that altered expression of several other genes [MET; MYC; transforming growth factor beta (TGF beta); CD44; vascular endothelial growth factor (VEGF); human neurological-related cell adhesion molecule (hNr-CAM); neuroglial cell adhesion molecule (NCAM L1); p21waf1/Cip1; TRKA; mismatch repair genes (MMR); C4-2; D2-2] and proteins [e.g., cathepsins, tenascin, matrix metalloproteases, tissue inhibitors of metalloproteases, nitric oxide synthase, integrins, interleukin-13 receptor (IL-13R), Connexin43, urokinase-type plasminogen activator receptors (uPARs), extracellular matrix proteins and heat shock proteins] are associated with the genesis of human gliomas. Taken together, these findings point to the accumulation of multiple genetic mutations coupled with extensive changes in gene expression in the etiology of human gliomas.