| Backgroud and PurposeGlioma is one of the most common cancers in the central nervous system, and continues to be the cause of a disproportionate level of morbidity and mortality across a wide range of individuals. Although there have been considerable advances in the understanding of the basic biology and pathogenesis of glioma, the outcome is still poor. Among them,Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumour in adults and the median survival after diagnosis is shorter than 1 year,no matter Combined Modality Therapy,including operation, radiotherapy and chemotherapy adopted.Mammalian target of rapamycin (mTOR), a 250 kDa protein, regulates multiple cell growth and cellular functions by controlling mRNA translation, ribosome biogenesis, autophagy, and metabolism. Evidence is emerging that mTOR is involved in the pathogenesis of several human cancers, and inhibition of mTOR interrupts the signalling pathways of cancer pathogenesis. Protein kinase B (AKT), which is elevated in some of the malignant gliomas, is known to activate mTOR. The activated mTOR phosphorylates p70 S6 kinase (70S6K), a key regulator for protein synthesis, and induces glioblastoma formation in mice. In mice glioma cells, mTOR is required for the maintenance of astrocytic character, and blockade of mTOR results in regional apoptosis in these tumors. There is limited information about the expression and role of mTOR signalling pathways in human malignant gliomas. The first part of this study was to investigate the expression of three key proteins of mTOR signalling pathway, pAKT,pmTOR,pp70S6K,survivin and Ki-67 in human gliomas, and to explore the relationship between these proteins and malignancy grade of the tumors.Golgi phosphoprotein 3 (GOLPH3), also known as GPP34, GMx33, or MIDAS, is a membrane protein with a molecular weight of 34KD. GOLPH3 is one of the many proteins in trans-Golgi matrix that involved in anterograde and retrograde Golgi traffic, as well as interactions with the cytoskeleton and maintenance of the Golgi structure. GOLPH3 is localized to the cytoplasmic face of the trans-Golgi and is also present in a large cytoplasmic pool. A recent study by Scott et al showed the presence of GOLPH3 as an oncogene in several solid cancers. Although the precise role of GOLPH3 in cancer pathogenesis is still under active investigation, some recent studies suggest that GOLPH3 regulates cell size and enhances growth-factor-induced mammalian target of rapamycin (mTOR) signaling in human cancer cells. The second part of this study was to investigate if GOLPH3 is present in glioma, and to evaluate the relationship between GOLPH3 expression and the malignancy severity of the tumor.Materials and MethodsIn the first part of this study, tumor tissues from 87 Chinese patients (49 males, average age of 51.7±13.0 years, range 15-78) with glioma were prospectively collected. The expression of three key proteins of the mTOR pathway, pAKT,pmTOR and p-p70S6 kinase (p-p70S6K) was measured by semi-quantitative immunohistochemical techniques. Grade I-II, III and IV glioma was pathologically identified in 27(31.0%),24 (27.6%) and 36 (41.4%) patients, respectively.In the second part of this study, Reverse transcription-polymerase chain reaction and Western-blot was used respectively to investigate the expression of GOLPH3 mRNA and protein in 76 patients with glioma. Non-cancerous brain issues and lung cancer cells were used as controls. There were 45 males and 31 females (mean age 50.7±12.8 years). Astrocytoma was found in 65 patients and glioblastoma in 11. Results Of the 87 patients in part one, pAKT,pmTOR and p-p70S6K were found in 63 (72.4%),65(74.7%), and 63 (72.4%) patients, respectively. The expression of all three pAKT,pmTOR and p-p70S6K proteins was found in 42(48.3%) patients, while only one or two of the three proteins were found in the remaining patients (51.7%). The percentage of patients with very strong expression of pAKT, pmTOR and p-p70S6K in grade IV glioma was 13(36.1%),16(44.4%) and 15(41.7%), respectively, which was greater than in grade I or II tumors (0-3.7%, P<0.01).Of the part two, No GOLPH3 expression was found in the non-cancerous brain tissues, but positive GOLPH3 protein was found in lung cancer cells. GOLPH3 mRNA and protein expression was identified in 40 patients with glioma (52.6%). The positive expression rate of GOLPH3 mRNA or protein was similar between patients with astrocytoma grade I to III and glioblastoma (P>0.05). The highest mean value of GOLPH3 mRNA and protein was found in patients with glioblastoma (P< 0.01), whereas the lowest mean values were found in those with grade 1 astrocytoma (P< 0.01).Conclusions1. Expression of mTOR pathway proteins pAKT, pmTOR and p-p70S6K can be found in human glioma of all malignancy grades. However, higher levels of these proteins were associated with advanced malignancy grades of the tumor.2. GOLPH3 expression was present in more than half of the patients with glioma. The amount of GOLPH3 expression in the glioma is associated with the severity of the tumor. Whether positive GOLPH3 gene expression can be used as a predictor for prognosis of the patients, or as a therapeutic target for glioma requires further investigation. |
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