1650P - Analysis of CD40 Expression on Circulating Colorectal Cancer Cells

Abstract

ABSTRACT Background In colorectal cancer circulating tumor cells (CTCs) can be clinically relevant as: prognostic factor and predictive biomarker for treatment efficacy. The detecting and the carachterization of CTCs remains technically challenging. The cell surface costimulatory molecule CD40, widely expressed by lymphoid cells and by various tumour types, has been indicated as prognostic/predictive biomarker and as a potential target for therapy. In the present study we wanted to demonstrate the value of a multiparameter flow cytometry (FCM) approach for the detection and the characterization of circulating colorectal cancer cells in vivo. Methods SW48 and HCT116 human colorectal cancer cells (highly positive for CD40) were serially diluted in normal whole blood to evaluate the sensitivity of the method in both the cancer cell identification and characterization for CD40 expression. Then, we analyzed PB samples from 10 patients with advanced colorectal cancer to identify CTCs; PB from normal subjects was utilized as negative control. Analyses were performed using a Navios FCM (Beckman Coulter ®) equipped with a dedicated software for multidimensional analyses. Results The method was found to have a sensitivity limit of 10(-5). The specificity was 100%. In 8 patients we were able to differentiate in vivo CTCs from normal mononuclear cells based on increased light scatter parameters, cell marker expression (EpCAM+ CD45-) and nuclear stain with 4'6-diamidino-2-phenylindole. In half of the patients the simultaneous analysis of the CD40 expression revealed significant high levels. Conclusions Multiparameter FCM can detect CTCs in colorectal cancer patients and allows simultaneous immunophenotype analysis. CTC identification and characterization represent emerging applications of FCM in solid tumor biology. Disclosure All authors have declared no conflicts of interest.