Detection and prognostic role of circulating cancer-associated fibroblasts in the blood of melanoma patients

Abstract

Background: Cancer-associated fibroblasts (CAFs), frequently present in many tumor tissues, have received increasing attention over the past decade, while research on CAFs circulating in the blood of cancer patients is still in its infancy. This is the first study to assess the incidence, concentration, and potential prognostic value of cCAFs alone or in combination with other biomarkers such as circulating tumor cells (CTCs) or cancer-associated proteins, in melanoma patients. Methods: CTCs and cCAFs were enriched from whole blood samples of 31 melanoma patients (stage IIB-IV) using the CTCeptor system, which makes use of automated density-based enrichment and CD45-based negative depletion. The isolated cells were stained with DAPI, and antibodies against MART-1, MCAM, alpha-SMA, and CD45. CTCs were defined as DAPI+, MART-1/MCAM+, CD45-cells, while cCAFs were defined as DAPI+, alpha-SMA+, CD45-cells. Results: CTCs and cCAFs were detected in approximately half of the melanoma patients, respectively. On average, more cCAFs (mean: 11 cells, range: 1-60) than CTCs (mean: 4.5 cells, range: 1-20) were found in the patients' blood samples. The median progression-free survival (PFS) for patients with an increased cCAF count (>= 5) was 2.07 months, while for those with a lower cCAF count (<5), it was 10.35 months (p = 0.51). When combined with elevated lactate dehydrogenase (LDH) (>= 245 U/L) or S100B (>= 0.152 mu g/L) levels, high cCAF counts tend to a reduced PFS (high LDH/high cCAF: 1.92 months, high S100B/high cCAF: 1.77 months), compared to patients with low LDH/S100B, indicating improved risk stratification when cCAFs are used alongside established biomarkers. Conclusion: This study demonstrates the possibility of co-detecting CTCs and cCAFs in the blood of melanoma patients for the first time. A higher mean number of cCAFs was detected and showed a trend toward shorter progression-free survival. The encouraging results of this pilot study need to be validated on a larger cohort of melanoma patients.