Winter Meeting 2011 - The Pathological Society of Great Britain ...

P25
MGMT Methylation is Strongly Associated with and May
Precede IDH1/IDH2 Mutations in Adult Astrocytic and
Oligodendroglial Tumours
P SA Mulholland; DS Malley; R Hamoudi; S Kocialkowski;
D Pearson; VP Collins; K Ichimura
University of Cambridge, Cambridge, United Kingdom
Gliomas are the most common group of primary brain tumours. They include astrocytic
(including glioblastoma), oligodendroglial and mixed gliomas. IDH1/IDH2 mutations are
found in more than 50% of astrocytic and oligodendroglial tumours of grade II and III
and considered to be an early change. Presence of MGMT methylation has been shown to
predict a good response to temozolomide and improved survival. A problem for clinical
MGMT methylation testing is the lack of consensus on what area of the MGMT CpG
island (CGI) should be analysed. The aim of this study was to 1) define the optimal target
region for MGMT methylation-testing by bisulfite modification and pyrosequencing
2) profile methylation at each CpG in MGMT CGI in a large cohort of gliomas and 3)
correlate MGMT methylation with other genetic abnormalities including IDH1/IDH2
mutations.
The methylation status of each CpG in MGMT CGI was determined and compared
with MGMT mRNA expression in 22 glioblastoma xenografts, 13 glioma cell lines and
6 normal brain tissues. A luciferase assay was used to investigate selected CpGs for their
role in transcription. The optimised pyrosequencing assay was then used to investigate
406 astrocytic and oligodendroglial tumours of all major types.
We identified a 120 bp region containing 16 CpG sites to be most critical in
transcriptional control. Methylation in this region was present in 58% of 406 gliomas.
We found that MGMT methylation was 100% concordant with IDH1/IDH2 mutations
in astrocytoma grade II and all oligodendrogliomas. All glioblastomas with IDH1/IDH2
mutations also had MGMT methylation, while the majority of glioblastomas with MGMT
methylation did not have IDH1/IDH2 mutations.
We propose a robust pyrosequencing assay to accurately assess MGMT methylation.
Our data suggests that MGMT methylation is the earliest change in the development of
astrocytomas and oligodendrogliomas, preceding IDH1/IDH2 mutations.
P27
The Expression of Growth Hormone Receptors in Colorectal
Carcinoma
P M Kabeer 1 ; AL Widdison 2 ; A Demaine 1 ; J Mathew 2
1 Peninsula College of Medicine and Dentistry, Plymouth, United Kingdom;
2 Royal Cornwall Hospital, Truro, United Kingdom
Background and Aims: Among the aetiological factors of colorectal cancers (CRCs),
hormones have also been known to play a role and growth hormone has been indirectly
linked to the development of CRCs. It exerts its effects through receptors (GHRs) and
previously, upregulation of GHRs has been found. Except for one, these studies did not
use normal controls. The aim of this study was to investigate the expression of GHRs in
CRCs, their normal adjacent bowel and lymph node metastasis. Comparisons were also
made with the cell proliferation markers Ki-67 and PCNA.
Methodology and Results: Standard immunohistochemistry techniques using
commercially available antibodies were used to determine receptor immunoreactivity
(IR). A ‘Modified Quickscore’ technique was used to score the intensity and density
separately and a multiple was obtained. These were statistically evaluated using t-test to
obtain P-values. Comparisons were made by gender of the patients, differentiation and
Dukes’ stage to evaluate if this had any effect on receptor expression.
GHR IR was significantly reduced in tumour and adjacent normal bowel compared to
normal controls (P