PFS Progression-free Survival PIK3 Phosphatidylinositide 3-kinase gene PLCB1 Phospholipase-C beta 1 gene PNGase F Peptide N-glycosidase F pNPP Para-nitrophenylphosphate PR Progesterone receptor PRKAR2β cAMP-dependent Protein Kinase A Regulated type II beta gene PSA Prostate Specific Antigen pT Primary Tumour PTEN Phosphatase and Tensin gene homolog r2 Coefficient of determination Retinoic Acid Receptor-β2 gene RASSF1A Ras Association Domain-containing Protein 1 gene REC Research Ethics Committee rEN2 Recombinant Engrailed 2 protein RIPA Radioimmunoprecipitation Assay RMI Risk of Malignancy Index RNA Ribonucleic Acid RNAi Ribonucleic Acid Interference ROC Receiver Operator Characteristic ROX Reference dye RR Relative Risk RSCH The Surrey County Hospital rt-PCR Reverse Transcriptase Polymerase Chain Reaction SCTR Secretin Receptor gene SD Standard Deviation SDS Sodium Dodecyl Sulphate SDS-PAGE Sodium Dodecyl Sulphate-polyacrylamide Gel Electrophoresis SE Standard Error
CA 125 (ovarian cancer) [] AFP, LDH, βHCG (germ cell tumour) [] Monitor for response/progression in metastatic disease CA15-3 and CEA (breast cancer) [] CA 125 (ovarian cancer) [] Predict drug toxicity CYP3A4, CYP3A5, UGT1A1 lymphoblastic leukaemia) [, ] Table 1.6. Potential uses for cancer biomarkers (adapted from []).
improved progression-free survival []. Within chemo-resistant serous EOC ascites specimens, Huang et al identified significantly up-regulated levels of ceruloplasmin, so analysis of ascites may also be able to predict treatment response or help to target treatment []. Autoantibodies Anti-tumour antibodies provide a novel field in diagnostic biomarker research as they allow recognition of tumour antigen at an earlier stage in tumour development because the immune system responds to tumour emergence very early. This enables antigen detection at very low levels, perhaps lower than can be reliably detected by direct protein assay. As well as a potentially useful early diagnostic tool, they may also provide anti-tumour defence. Serum autoantibodies directed against tumour associated antigens have been frequently detected in the sera of patients with different types of cancer []. Antibodies to epithelial cell adhesion molecule (Ep-CAM) [], HSP-90 [, ], HOXA7 [], HER2 and MUC1 [, ] have been identified in ovarian cancer. It is difficult to see how some of these autoantibodies will prove useful in early diagnosis of cancer as they are often identified in more than one tumour type, although combinations of antibodies may hold more promise. The search for diagnostic biomarkers, prognostic factors, as well as an explanation as to why patients develop resistance to drug treatment continue to be a major challenge in ovarian cancer. Intensive research has identified several poor prognostic factors but the causes of chemotherapy resistance, the ways of overcoming this problem and factors related to cancer progression remain a major challenge. THE HOMEOBOX GENE SUPERFAMILY
In pilocytic astrocytomas, which are the most common childhood brain tumours, Lambert et al. observed a strong positive correlation between En2 methylation and expression, along with a number of other key neural developmental genes []. However this methylation frequently involved the gene body rather than the promoter region. Gene body-specific methylation has previously been identified on the active X chromosome in contrast to promoter methylation with corresponding gene silencing of the inactive X chromosome []. It has been hypothesised that such gene body methylation increases levels of transcription via repression of internal gene promoters, suppressing repetitive elements and switching promoter usage within a gene [, ]. Further detailed research involving En2 hypermethylation has been conducted in conditions, such as the autism spectrum disorders. Previous work highlighted genetic linkage of En2 in families with autistic members, along with broad similarities between the neuropathology seen in En2 knockout mice and autistic individuals, resulting in it being considered as an autism susceptibility gene []. James et al. therefore studied En2 promoter region methylation in post-mortem cerebellar cortex specimens from autistic and matched unaffected individuals []. Within the context of global DNA hypermethylation in autistic samples compared with controls, they also demonstrated significant En2 promoter hypermethylation in the autistic examples compared with the control samples (23±4% versus 10±2%; p=0.005), using the McrBC-PCR assay, the same assay that we used in our methylation work. They confirmed these findings using a second assay, MSR-PCR, which demonstrated similar En2 promoter region hypermethylation. The authors were surprised to observe significantly elevated expression levels of En2 mRNA in the autism samples, alongside the promoter region hypermethylation, demonstrating a positive correlation between these variables in the case and control samples (p=0.007). They also confirmed an increased level of EN2 protein in the autism specimens via western blot, consistent with the increase in En2 gene expression. CONCLUSION