Metastatic melanoma is one of the most aggressive and drug-resistant cancers with very poor overall survival. Circulating melanoma cells (CMCs) were first described in 1991. However, there is no general consensus on the clinical utility of CMC detection, largely due to conflicting results linked to the use of heterogeneous patient populations and different detection methods. Here, we developed a new EPithelial ImmunoSPOT (EPISPOT) assay to detect viable CMCs based on their secretion of the S100 protein (S100-EPISPOT). Then, we compared the results obtained with the S100-EPISPOT assay and the CellSearch® CMC kit using blood samples from a homogeneous population of patients with metastatic melanoma. We found that S100-EPISPOT sensitivity was significantly higher than that of CellSearch®. Specifically, the percentage of patients with ≥2 CMCs was significantly higher using S100-EPISPOT than CellSearch® (48% and 21%, respectively; p = 0.0114). Concerning CMC prognostic value, only the CellSearch® results showed a significant association with overall survival (p = 0.006). However, due to the higher sensitivity of the new S100-EPISPOT assay, it would be interesting to determine whether this functional test could be used in patients with non-metastatic melanoma for the early detection of tumor relapse and for monitoring the treatment response.

the incidence of Merkel cell carcinoma (Mcc), a rare and highly metastatic skin malignancy, has sharply increased in the last decade. clinical biomarkers are urgently needed for Mcc prognosis, treatment response monitoring, and early diagnosis of relapse. the clinical interest of circulating tumors cells (ctcs) has been validated in many solid cancers. the aim of this study was to compare ctc detection and characterization in blood samples of patients with Mcc using the cellSearch System and the RosetteSep -DEPArray workflow, an innovative procedure to enrich, detect and isolate single CTCs. In preliminary experiments (using spiked Mcc cell lines) both methods allowed detecting very few Mcc cells. In blood samples from 19 patients with MCC at different stages, CellSearch detected MCC CTCs in 26% of patients, and the R-D workflow in 42% of patients. The detection of CTC-positive patients increased to 52% by the cumulative positivity rate of both methodologies. Moreover, Merkel cell polyomavirus DnA, involved in Mcc oncogenesis, was detected in tumor biopsies, but not in all single CTCs from the same patient, reflecting the tumor heterogeneity. Our data demonstrate the possibility to detect, isolate and characterize ctcs in patients with Mcc using two complementary approaches.Merkel Cell Carcinoma (MCC) is a rare and aggressive neuroendocrine skin cancer, the incidence of which has been steadily increasing over the last decades 1,2 . It is one of the most lethal skin malignancies after melanoma 3 , and more frequently affects fair-skinned men with a median age of 70 years at diagnosis 4 . MCC usually appears as a rapidly growing red or purple nodule mostly located on UV-exposed areas (head, neck or upper limbs). Several risk factors have been identified, such as UV exposure, disease-or treatment-related immunosuppression, notably transplanted and HIV-infected patients 5 . A new virus belonging to the Polyomaviridae family and named Merkel cell polyomavirus (MCPyV) has been identified in some MCC tissue specimens 6 . The clonal integration of the viral DNA in the genome of MCC cells 7 suggests that this phenomenon is an early event occurring before malignant transformation 8 . This virus is present in most MCC (about 80% of patients) and seems to play a direct role in malignant transformation, most notably through the intervention of oncogenic proteins 6 . Indeed, MCPyV expresses the large T antigen and the small T antigen that display a strong oncogenic activity 9,10 . These oncogenic viral proteins are both expressed in MCPyV + MCC and seem to be necessary for the maintenance of MCPyV + MCC cell lines 11 . Conversely, MCPyV − MCC are characterized by higher number of mutations in key genes, a UV-mutational signature, and more chromosomal aberrations compared with MCPyV + tumors 8,12 , suggesting two distinct oncogenic pathways.Circulating tumor cells (CTCs) are considered as the real-time liquid biopsy for patients with cancer, described for the first time in 2010 13,14 . The stem-cell properties and sometimes the...

Background: Platelets are active players in hemostasis, coagulation and also tumorigenesis. The cross-talk between platelets and circulating tumor cells (CTCs) may have various pro-cancer effects, including promoting tumor growth, epithelial-mesenchymal transition (EMT), metastatic cell survival, adhesion, arrest and also pre-metastatic niche and metastasis formation. Interaction with CTCs might alter the platelet transcriptome. However, as CTCs are rare events, the cross-talk between CTCs and platelets is poorly understood. Here, we used our established colon CTC lines to investigate the colon CTC-platelet cross-talk in vitro and its impact on the behavior/phenotype of both cell types.Methods: We exposed platelets isolated from healthy donors to thrombin (positive control) or to conditioned medium from three CTC lines from one patient with colon cancer and then we monitored the morphological and protein expression changes by microscopy and flow cytometry. We then analyzed the transcriptome by RNA-sequencing of platelets indirectly (presence of a Transwell insert) co-cultured with the three CTC lines. We also quantified by reverse transcription-quantitative PCR the expression of genes related to EMT and cancer development in CTCs after direct co-culture (no Transwell insert) with platelets.Results: We observed morphological and transcriptomic changes in platelets upon exposure to CTC conditioned medium and indirect co-culture (secretome). Moreover, the expression levels of genes involved in EMT (p < 0.05) were decreased in CTCs co-cultured with platelets, but not of genes encoding mesenchymal markers (FN1 and SNAI2). The expression levels of genes involved in cancer invasiveness (MYC, VEGFB, IL33, PTGS2, and PTGER2) were increased.Conclusion: For the first time, we studied the CTC-platelet cross-talk using our unique colon CTC lines. Incubation with CTC conditioned medium led to platelet aggregation and activation, supporting the hypothesis that their interaction may contribute to preserve CTC integrity during their journey in the bloodstream. Moreover, co-culture with platelets influenced the expression of several genes involved in invasiveness and EMT maintenance in CTCs.