Genetic alterations of the tumor suppressor gene PTEN/MMAC1 in human brain metastases.
ABSTRACT The high mutation rate in advanced brain tumors, recent functional studies, and the high frequency of mutations in prostate metastases all strongly suggest that PTEN/MMAC1 alterations are involved in the formation of metastases. We searched for genetic alterations in the PTEN/MMAC1 gene in 56 consecutive brain metastases from various primary tumors by loss of heterozygosity (LOH), direct sequence analysis, and differential PCR analysis. The highest LOH rates were detected in metastases deriving from lung (67%) and breast (64%) cancers. Three (25%) of the eight detected inactivating mutations (one nonsense mutation, one splice-site mutation, one 11-bp deletion, and five homozygous deletions) were found in metastases originating from 12 different lung carcinomas, suggesting that PTEN/MMAC1 alterations may play a role in the progression of this tumor. With the exception of lung carcinomas, our findings indicate that genetic abnormalities of the PTENM/MMAC1 gene are only involved in a relatively small subset of brain metastases. However, the discrepancy between the high overall LOH rate (50%) and the low frequency of PTEN/MMAC1 mutation detection rate (14%) suggests the presence of one or more additional tumor suppressor genes on chromosome 10q.
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ABSTRACT: Glioblastoma is the most frequent and malignant human brain tumor. High level of genomic instability detected in glioma cells implies that numerous genetic alterations accumulate during glioma pathogenesis. We investigated alterations in AP-PCR DNA profiles of 30 glioma patients, and detected specific changes in 11 genes not previously associated with this disease: LHFPL3, SGCG, HTR4, ITGB1, CPS1, PROS1, GP2, KCNG2, PDE4D, KIR3DL3, and INPP5A. Further correlations revealed that 8 genes might play important role in pathogenesis of glial tumors, while changes in GP2, KCNG2 and KIR3DL3 should be considered as passenger mutations, consequence of high level of genomic instability. Identified genes have a significant role in signal transduction or cell adhesion, which are important processes for cancer development and progression. According to our results, LHFPL3 might be characteristic of primary glioblastoma, SGCG, HTR4, ITGB1, CPS1, PROS1 and INPP5A were detected predominantly in anaplastic astrocytoma, suggesting their role in progression of secondary glioblastoma, while alterations of PDE4D seem to have important role in development of both glioblastoma subtypes. Some of the identified genes showed significant association with p53, p16, and EGFR, but there was no significant correlation between loss of PTEN and any of identified genes. In conclusion our study revealed genetic alterations that were not previously associated with glioma pathogenesis and could be potentially used as molecular markers of different glioblastoma subtypes.PLoS ONE 01/2013; 8(12):e82108. · 3.53 Impact Factor
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ABSTRACT: Multi-drug resistance (MDR) is a major obstacle to successful cancer treatment. Therefore, in vitro models are necessary for the investigation of the phenotypic changes provoked by cytotoxic agents and more importantly for preclinical testing of new anticancer drugs. We analyzed chromosomal, numerical, and structural changes after development of MDR, alterations in p53 and PTEN, single nucleotide polymorphisms (SNPs) in the mdr1 gene and corresponding protein expression of P-glycoprotein (P-gp) in three human MDR cancer cell lines: non-small cell lung carcinoma NCI-H460/R, colorectal carcinoma DLD1-TxR, and glioma U87-TxR. In addition, we explored how these molecular and phenotypic alterations influence the anticancer effect of new drugs. Cytogenetic analysis showed polyploidy reduction after development of MDR in U87-TxR. Losses of 6q in all resistant cancer cell lines and inactivation of p53 in U87-TxR and PTEN in DLD1-TxR were also revealed. Overexpression of P-gp was observed in all MDR cancer cell lines. We evaluated the anticancer activities and MDR reversal potential of Akt inhibitor GSK690693, Ras inhibitor Tipifarnib, and two P-gp inhibitors (jatrophane diterpenoids). Their effects vary due to the cell-type differences, existence of MDR phenotype, presence of mdr1 SNP, and tumor suppressors' alterations. Tipifarnib and jatrophane diterpenoids significantly sensitized MDR cancer cells to paclitaxel. In conclusion, investigated MDR cancer cells obtained new molecular and cytogenetic characteristics that may serve as potential clinical prognostic markers. In addition, these MDR cancer cell lines present a valuable model for preclinical evaluation of new anticancer agents.Cancer Chemotherapy and Pharmacology 08/2013; · 2.80 Impact Factor
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ABSTRACT: Zusammenfassung Die Inaktivierung von p16 und p14ARF wird als bedeutender Schritt der Tumorgenese des Oropharynxkarzinoms angesehen. Allelverluste in der Region dieser Gene werden in Mundschleimhautkarzinomen und deren Vorläuferläsionen angetroffen. Die vorliegende Studie sollte prüfen, in welchem Umfang Allelverluste bereits in Mundschleimhautleukoplakien auftreten und ob es anhand dieser Veränderungen möglich ist, Leukoplakien mit und ohne maligne Entartung zu unterscheiden. Darüber hinaus sollten geklärt werden, ob betroffene Leukoplakien Sequenzveränderungen der Gene p16 und p14ARF tragen, die eine Beeinträchtigung der Genfunktion bewirken können. Die Ergebnisse zeigten, dass „LOH“ (loss of heterozygosity) in Region der Gene p16 und p14ARF sowohl in Leukoplakien mit maligner Entartung als auch in klinisch entartungsfreien Leukoplakien auftreten, wobei sich die Allelverlusthäufigkeiten nicht signifikant unterscheiden. Insgesamt wurden in Leukoplakien seltener Allelverluste angetroffen als in den resultierenden Mundschleimhautkarzinomen (pMund- Kiefer- und Gesichtschirurgie 11/2007; 11(6):317-326.