Absence of the MGMT protein as well as methylation of the MGMT promoter predict the sensitivity for temozolomide

The DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT) can cause resistance to the alkylating drug temozolomide (TMZ). The purpose of this study was to determine the relationship between the MGMT status, determined by means of several techniques and methods, and the cytotoxic response to TMZ in 11 glioblastoma multiforme (GBM) cell lines and 5 human tumour cell lines of other origins. Cell survival was analysed by clonogenic assay. The MGMT protein levels were assessed by western blot analysis. The MGMT promoter methylation levels were determined using methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) and quantitative real-time methylation-specific PCR (qMSP). On the basis of the results of these techniques, six GBM cell lines were selected and subjected to bisulphite sequencing. The MGMT protein was detected in all TMZ-resistant cell lines, whereas no MGMT protein could be detected in cell lines that were TMZ sensitive. The MS-MLPA results were able to predict TMZ sensitivity in 9 out of 16 cell lines (56%). The qMSP results matched well with TMZ sensitivity in 11 out of 12 (92%) glioma cell lines. In addition, methylation as detected by bisulphite sequencing seemed to be predictive of TMZ sensitivity in all six cell lines analysed (100%). The MGMT protein expression more than MGMT promoter methylation status predicts the response to TMZ in human tumour cell line

O6-Methylguanine-DNA methyltransferase protein expression by immunohistochemistry in brain and non-brain systemic tumours: systematic review and meta-analysis of correlation with methylation-specific polymerase chain reaction

Background: The DNA repair protein O6-Methylguanine-DNA methyltransferase (MGMT) confers resistance to alkylating agents. Several methods have been applied to its analysis, with methylation-specific polymerase chain reaction (MSP) the most commonly used for promoter methylation study, while immunohistochemistry (IHC) has become the most frequently used for the detection of MGMT protein expression. Agreement on the best and most reliable technique for evaluating MGMT status remains unsettled. The aim of this study was to perform a systematic review and meta-analysis of the correlation between IHC and MSP. Methods A computer-aided search of MEDLINE (1950-October 2009), EBSCO (1966-October 2009) and EMBASE (1974-October 2009) was performed for relevant publications. Studies meeting inclusion criteria were those comparing MGMT protein expression by IHC with MGMT promoter methylation by MSP in the same cohort of patients. Methodological quality was assessed by using the QUADAS and STARD instruments. Previously published guidelines were followed for meta-analysis performance. Results Of 254 studies identified as eligible for full-text review, 52 (20.5%) met the inclusion criteria. The review showed that results of MGMT protein expression by IHC are not in close agreement with those obtained with MSP. Moreover, type of tumour (primary brain tumour vs others) was an independent covariate of accuracy estimates in the meta-regression analysis beyond the cut-off value. Conclusions Protein expression assessed by IHC alone fails to reflect the promoter methylation status of MGMT. Thus, in attempts at clinical diagnosis the two methods seem to select different groups of patients and should not be used interchangeably

How useful are plant community studies for coastal dune restoration?

International audienc

Etude des communautés des dunes embryonnaires de l’étang de Berre en vue de leur restauration.

National audienc

SO-26 Identification and quantification of the microbiome in colorectal cancer metastases

Background: Recent research has identified the existence of living bacteria in the tumor microenvironment, as well as cancer-specific bacteria in blood of patients. Early evidence suggested a role of the gut and tissue microbiome in the development of colorectal cancer (CRC). However, the part of this intra-tumor microbiome in promoting or aiding metastasis to distant organs remains unexplored. Interestingly, similar bacterial strains from CRC primary tumors have been identified in patientmatched liver metastases. Few mechanistic hypotheses have been proposed of how bacterial translocation to distant sites occurs, or whether the tumor-resident microbiome can influence the spreading or the behavior of metastases and their local immune response. Methods: We aimed to characterize the intra-tumor bacterial signature of metastatic colorectal cancer (mCRC) through a large-scale study with different cohorts from several biobanks in Belgium. We collected 378 frozen samples from 99 patients composed by 104 primary colorectal tumors (PT) and 99 patient-matched liver metastases (LMT), both associated with normal adjacent tissue (NAT) as control (n ¼ 83 and 58, respectively). We added primary liver tumors (hepatocellular carcinoma (HCC, n¼28) and cholangiocarcinoma (CGC, n¼6)) from 27 patients as comparative cohort for LMT. The V4 region of the bacterial 16S rRNA gene was sequenced. The computational DADA2 pipeline was used to process the sequencing data and determine the abundance of amplicon sequence variants (ASV). We strictly applied sterile conditions from sample collection to sequencing, with negative and positive controls along the process to minimize contamination and misinterpretation of the results. Potential contaminants were removed bioinformatically by applying a series of stringent filters. Results: Bacterial sequences were identified in all tissue types. Based on preliminary results, the principal component analysis based on bacterial composition of the samples revealed significant sample grouping (PERMANOVA, p-value ¼ 1e-04) per tissue type (PT, LMT and HCC-CGC). The read number and bacterial composition of associated NAT were similar to their associated tumor tissue. PT, as expected by their colonic origin, presented higher bacterial biomass than LMT, yet the patient-specific microbiome composition in LMT was partially overlapping with PT, consisting with previously reported prevalent taxa. The number of shared ASVs between PT and LMT was significantly higher within than between patients (linear regression model with pvalue ¼ 4,22e-10), suggesting an individual bacterial transfer. This transfer appeared to be a probabilistic event, as it correlated with taxa abundance, and this transfer was more likely for the most abundant bacteria in the PT. Conclusions: Our preliminary results suggest the presence of a low bacterial biomass in LMT with characteristics closer to PT compared to primary tumors of the liver, suggesting a “per-tumor type” rather than “per-organ” bacterial signature and abundance. A within-patient bacterial transfer from PT to LMT seems to be observed for the most abundant taxa. These preliminary results are currently in a validation process. If our results are confirmed, this multicentric large-scale study would allow us to characterize and classify tumor tissue bacterial signature in mCRC to compare it with genomic and immune tumor features