Testing the utility of biomarkers in detecting micrometastasis in colorectal cancer

Abstract

Early diagnosis provides the best prognosis for colorectal cancer (CRC); current assessment and staging methodologies are reliant on lymph node assessment by pathologist using histochemical staining. It is hoped the development of new immunological and molecular biomarkers will provide sensitive and specific supplementary diagnostic and prognostic tests that will inform clinical treatment and decision making. This thesis reviews the current understanding of colorectal cancer and its treatment. The objective of the study is to test the utility of the protein and mRNA transcript levels of the LMNA and HMGA2 genes as biomarkers in lymph node to reveal the presence of metastasis. Specifically, the aim is to investigate how IHC and qPCR can improve metastasis detection, in comparison with histological assessment and how the approaches might be applied to the 20-30% of (Dukes stage A and B patients) who experience recurrence with 5 years as part of a diagnostic approach for these patients. In pilot studies antibodies to Lamin A/C were used to detect metastasis in IHC experiments. For the main study, the approach was to extract RNA from 198 formalin fixed paraffin embedded (FFPE) tumour and lymph nodes tissue taken from 61 CRC patients who had standard resections. cDNA produced by reverse transcription was assessed by quantitative PCR to assess levels of HMGA2 and Lamin A/C transcripts. Statistically significant differences in levels of HMGA2 mRNA expression were detected [(p-value <0.05) (0.000005194) with 14/22 (64%) of H&E positive lymph nodes showing HMGA2 expression compared with 9/104 (8.6%) of the H&E negative lymph nodes and 10/(52-15), 27% Primary tumours express HMGA2. No significant expression level changes were observed for Lamin A/C mRNA. Interestingly, eight (13%) Dukes Stage A and B patients showed HMGA2 expression. Conclusions: These qPCR assessment of the HMGA2 marker offers the prospect of a potential sentinel lymph node test for colorectal cancer in polyp patients.

Date of Award	Aug 2018
Original language	English
Awarding Institution	University of Portsmouth
Supervisor	Alan Thorne (Supervisor)