Analysis of circulating cancer associated cells in colorectal cancer

Abstract

Colorectal cancer was considered as the third most commonly diagnosed cancer in Australia in 2017 overall, with estimated all-age incidence rates of 49.4 per 100,000 in females and 67.3 per 100,000 in males. It is hypothesised that cancer associated macrophage like cells (CAMLs) are tumour associated macrophages (TAMs) that have disseminated into the circulation. These TAMs can be present in high abundance in tumours and promote tumorigenesis. It has been shown that TAMs accumulate in colorectal cancer, and this accumulation increases with the advancing stage and may stimulate progression by changing the macrophage balance. The project aimed to optimise a panel of antibodies to identify circulating rare tumour associated cells and to (i) assess the CellSieve system to capture HT29 colorectal cancer cells and differentiated THP-1 cells as a model, and (ii) to determine the prevalence of all cancer associated cells before and after curative intent surgery using the CellSieve system and correlate the cell number with clinicopathological features. In summary, a panel of identification antibodies were validated and the CellSieve platform was assessed for the capture and identification of CTCs and CAMLs at pre-surgical (T0) and post-surgical (T1) time points. Future extended work with more patient samples is required with alternative technology to perform a comparison analysis for CAMLs numbers between microsatellite stable (MSS) and microsatellite instability high (MSI-H) subgroups, and to further phenotypically characterise CAMLs. This research adds additional evidence for the dynamics of CTC and CAML response to curative intent surgery. Baseline CTC and CAML numbers can be applied to as prognostic biomarkers, while enumeration after the treatment has the potential for monitoring treatment response and improve outcomes. Also, future extended work involving patients with MSI-H tumours would enable investigation of CAML numbers between two subgroups of CRC (MSS and MSI-H) and allow the investigation of our hypothesis that MSI-H patients (who also have high TILs) may have greater numbers of CAMLs compared with MSS patients. In addition, future work could involve a more detailed phenotypic characterisation of CAMLs including PD-L1 expression as well as a panel of immune cell markers to better understand the biology of CAMLs. If PD-L1 expression is evident on CAMLs, it is possible that PD-L1 immuno-scoring of CAMLs may potentially be useful in determining if a patient’s tumour is amenable for immunotherapy.

Date of Award	2023
Original language	English
Awarding Institution	Western Sydney University
Supervisor	Kevin Spring (Supervisor)