GRIM-19 Expression and Function in Human Gliomas

Overexpression of GRIM-19 accelerates radiation-induced osteosarcoma cells apoptosis by p53 stabilization

AIMS

Osteosarcoma is one of the most aggressive types of primary bone cancer that responds poorly to radiotherapy frequently. The gene associated with retinoid-interferon mortality (GRIM-19) is a tumor suppressor that mediates cell apoptosis in multiple cancer types. However, the role of GRIM-19 in osteosarcoma and the underlying mechanism remain unclear. This study was designed to investigate the role and the underlying mechanism of GRIM-19 in osteosarcoma progression.

MATERIALS AND METHODS

Osteosarcoma tissues and cell lines were utilized to analyze the expressions of GRIM-19 in osteosarcoma by qRT-PCR and Western blot. Methods containing flow cytometry, irradiation exposure, cells inoculation, plasmid transfection, and protein immunoprecipitation were used to investigate the underlying mechanisms of GRIM-19 in osteosarcoma progression.

KEY FINDINGS

GRIM-19 is downregulated in osteosarcoma tissues and cell lines. Exposure to radiation induces osteosarcoma cell apoptosis by upregulation of p53 both in U2OS (p53-wt) and exogenous p53-introduced MG-63 (p53-null) osteosarcoma cells. Overexpression of GRIM-19 accelerates radiation-induced osteosarcoma cells apoptosis by p53 stabilization ex vivo and in vivo. Mechanistically, forced expression of GRIM-19 diminishes the activity of E3 ubiquitin-protein ligase mouse double minute 2 homolog (MDM2), a specific p53 protease, results in the accumulation of p53 and activation of p53-mediated apoptosis.

SIGNIFICANCE

GRIM-19 was proved to modulate radiation-induced osteosarcoma cells apoptosis in a p53 dependent manner by mediating MDM2 activity, which sheds light on the development of GRIM-19-based molecular target therapy on osteosarcoma.

GRIM-19: A master regulator of cytokine induced tumor suppression, metastasis and energy metabolism

Cytokines induce cell proliferation or growth suppression depending on the context. It is increasingly becoming clear that success of standard radiotherapy and/or chemotherapeutics to eradicate solid tumors is dependent on IFN signaling. In this review we discuss the molecular mechanisms of tumor growth suppression by a gene product isolated in our laboratory using a genome-wide expression knock-down strategy. Gene associated with retinoid-IFN-induced mortality -19 (GRIM-19) functions as non-canonical tumor suppressor by antagonizing oncoproteins. As a component of mitochondrial respiratory chain, GRIM-19 influences the degree of "Warburg effect" in cancer cells as many advanced and/or aggressive tumors show severely down-regulated GRIM-19 levels. In addition, GRIM-19 appears to regulate innate and acquired immune responses in mouse models. Thus, GRIM-19 is positioned at nodes that favor cell protection and/or prevent aberrant cell growth.

Characterization of a β-1,3-glucan recognition protein from the beet armyworm, Spodoptera exigua (Insecta: Lepidoptera: Noctuidae)

The β-1,3-glucan recognition protein gene from Spodoptera exigua (SeβGRP) was cloned and characterized. The cDNA of this gene is 1 644 nucleotides in length and the predicted polypeptide is 491 amino acids (aa) in length, with a calculated molecular mass of 54.8 kDa. The first 22 aa encode a predicted secretion signal peptide. A BLAST search, multiple sequence alignment, and phylogenetic analysis of the aa sequence of SeβGRP revealed that this protein is most similar to the β-1,3-glucan recognition protein (βGRP) family of pattern recognition proteins. Using reverse-transcription polymerase chain reaction, we detected the presence of SeβGRP transcripts in the egg, larval, pupal, and adult stages of S. exigua. In addition, the SeβGRP transcript was expressed in all the tissues examined including the brain, hemocytes, fat body, intestine, and cuticle. There were no changes in SeβGRP mRNA levels in larvae infected with ultraviolet (UV)-killed Escherichia coli DH5α compared with the control larvae inoculated with the water; however, SeβGRP mRNA levels were markedly elevated 4-8 h after infection and slightly induced 12-24 h after infection in larvae injected with UV-killed Fusarium oxysporum. This may be because β-1,3-glucan is the main component of the cell wall of F. oxysporum, but not E. coli DH5α.

Characterization and expression of attacin, an antibacterial protein-encoding gene, from the beet armyworm, Spodoptera exigua (Hübner) (Insecta: Lepidoptera: Noctuidae)

To isolate antimicrobial-related genes from the beet armyworm, Spodoptera exigua, we performed GeneFishing, a polymerase chain reaction (PCR)-based differential display technique. An attacin-like complementary DNA (cDNA) including a 3'-untranslated region was identified from among 18 over-expressed genes in microbial-infected larvae. The full-length attacin cDNA from S. exigua cDNA (Seattacin) was cloned using rapid amplification of cDNA ends PCR. The attacin-like cDNA transcript was 765 nucleotides in length, and the predicted polypeptide was 254 amino acids in length with a calculated molecular mass of 27.6 kDa and an isoelectric point of 6.44. The protein sequence of the attacin-like cDNA showed high identity to that of Trichoplusia ni (61.2%). The amino acid sequence identity of Seattacin to the orthologous proteins in Bombyx mori, Manduca sexta, Heliothis virescens, Hlicoverpa armigera, Hyphantria cunea, Hyalophora cecropia, and Drosophila melanogaster was 61.2, 46.1, 44.5, 42.2, 39.5, 45.1, and 24.0%, respectively. To examine possible immune functions of the attacin-like cDNA, its expression was investigated by reverse transcriptase PCR analysis after challenging S. exigua with microorganisms. The attacin-like cDNA was expressed at high levels 12 h post-infection, and its expression was slightly induced 4-8 h post-infection compared to control larvae inoculated with sterile water. Furthermore, induced Seattacin showed biological activity against several bacteria including Escherichia coli DH5α, Pseudomonas cichorii, Bacillus subtilis, and Listeria monocytogenes. These results suggest that the attacin-like cDNA of S. exigua codes for antimicrobial peptides.

Clinical significance of GRIM-19 expression in hepatocellular carcinoma

AIM: To investigate the clinical significance of expression of gene associated with retinoid-interferon-induced mortality-19 (GRIM-19) in hepatocellular carcinoma (HCC).

METHODS: The expression of GRIM-19 mRNA and protein in 40 cases of HCC tissues and matched non-cancerous tissues was detected by reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry and Western blot. The correlation between GRIM-19 expression and clinicopathologic features of HCC was analyzed statistically.

RESULTS: The expression of GRIM-19 mRNA was significantly lower in HCC than in matched non-cancerous tissue (0.40 ± 0.31 vs 0.56 ± 0.67, P < 0.05). The positive rate of GRIM-19 protein expression in HCC was significantly lower than that in matched non-cancerous tissue (47.5% vs 80%, P < 0.05). The expression level of GRIM-19 protein was also significantly lower in HCC than in matched non-cancerous tissue (0.30 ± 0.29 vs 0.57 ± 0.10, P < 0.05). GRIM-19 expression differed significantly between patients with stages I + II disease and those with stages III+IV disease (0.57 ± 0.38 vs 0.30 ± 0.20, P < 0.05) as well as between patients with and without portal vein thrombosis (0.04 ± 0.02 vs 0.44 ± 0.32, P < 0.05). The expression of GRIM-19 was negatively correlated with serum AFP (r = -0.352, P < 0.05).

CONCLUSION: Decreased GRIM-19 expression is probably a significant event in the carcinogenesis of HCC and may be associated with tumor development, progression and invasion.