Background and significance: Chondroitin sulfate proteoglycan 4 (CSPG4) is a highly glycosylated cell surface proteoglycan that we are investigating as a potential biomarker for squamous cell carcinoma (SCC). Current data indicates that early diagnosis for SCCs is vital to prevent neoplastic progression and reduce the mortality rate, particularly for susceptible patients such as those with rare genetic disorders such as recessive dystrophic epidermolysis bullosa (RDEB). However, performing excision biopsies on RDEB patients, who suffer from wound-healing defects, can be problematic. Therefore, research has focused on developing methods for diagnosing SCCs that are less invasive than tissue biopsy. One approach is to identify cells that have disseminated from the tumour into the blood, referred to as circulating tumour cells (CTCs). In this project, we have adapted the ScreenCell® filtration protocol for CTC enrichment.
Methodology: We first characterised CSPG4 on RDEB and non-RDEB primary and commercial SCC cell lines using confocal microscopy and FACS analysis. Next, we selected the most malignant cell line to conduct spike-in ScreenCell® protocol to confirm proof-of-principle. Following this, we processed one Stage IV patient sample for analysis.
Results: Following the characterisation of CSPG4 on primary patient-derived and immortalised commercially available SCC cell lines, we observed higher expression in the more aggressive cell lines, including SCCs from general patients, as well as those isolated from the at-risk RDEB population in comparison to matched keratinocytes. Analysis of blood spike-in and patient blood samples processed through the ScreenCell® filters indicate successful enrichment and identification of SCCs using CSPG4 as a marker in association with common CTC markers: pan-cytokeratin+ and CD45- selection.
Conclusion: Taken together, the result of this study provides preliminary evidence suggesting the use of CSPG4 in the early diagnosis of disseminated disease in aggressive SCCs.