Molecular Diagnostics

Detection and prognostic role of heterogeneous populations of melanoma circulating tumour cells



Circulating tumour cells (CTCs) can be assessed through a minimally invasive blood sample with potential utility as a predictive, prognostic and pharmacodynamic biomarker. The large heterogeneity of melanoma CTCs has hindered their detection and clinical application.


Here we compared two microfluidic devices for the recovery of circulating melanoma cells. The presence of CTCs in 43 blood samples from patients with metastatic melanoma was evaluated using a combination of immunocytochemistry and transcript analyses of five genes by RT-PCR and 19 genes by droplet digital PCR (ddPCR), whereby a CTC score was calculated. Circulating tumour DNA (ctDNA) from the same patient blood sample, was assessed by ddPCR targeting tumour-specific mutations.


Our analysis revealed an extraordinary heterogeneity amongst melanoma CTCs, with multiple non-overlapping subpopulations. CTC detection using our multimarker approach was associated with shorter overall and progression-free survival. Finally, we found that CTC scores correlated with plasma ctDNA concentrations and had similar pharmacodynamic changes upon treatment initiation.


Despite the high phenotypic and molecular heterogeneity of melanoma CTCs, multimarker derived CTC scores could serve as viable tools for prognostication and treatment response monitoring in patients with metastatic melanoma.

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Fig. 1: CTC isolation platforms comparison.
Fig. 2: Phenotypic and morphological heterogeneity of melanoma CTCs after microfluidic enrichment.
Fig. 3: Comparison of gene expression profiles of CTC fractions using the five melanoma-specific RT-PCR and the 19 genes ddPCR.
Fig. 4: Association between CTC detection and clinical outcomes.
Fig. 5: CTC scores and ctDNA comparison.


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We thank patients and healthy volunteers for contributing samples to this study. We also acknowledge the clinical, nursing and phlebotomy staff of participating hospitals in the acquisition of blood samples. We thank Pauline Zaenker, Daniele Bartlett, Aaron Beasley, Gabriela Marsavela for their help with blood collection from healthy controls. In particular, we thank Paula Van Miert for helping with sample processing and Michelle Pereira for carrying out ctDNA analysis. We thank Peggy Robinson and Christopher Wagner from Angle plc, for their generous scientific and technical support and deploying the Parsortix platform. We thank Julie Lang (University of Southern California-USC, Los Angeles US) for conceptual advice on this project, and Daniel Haber and Shyamala Maheswaran (Harvard University, Boston US) for their comments on the results and interpretation.

Author information

C.A.B., M.Z., E.S.G., R.J.S. designed the study. C.A.B., M.Mo., J.F., L.C. performed experimental work. X.H. provided protocol details. C.A.B., M.Mo., X.H., L.C. and E.S.G. analysed data and performed statistical analysis. A.C.M., M.A.D., T.M. and M.Mi. enrolled patients into the study, collected and curated clinical data. C.A.B., M.Mo. and E.S.G. wrote the paper. All authors reviewed and approved the final version of the paper.

Correspondence to Elin Solomonovna Gray.

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Ethics approval and consent to participate

Healthy volunteers and melanoma patients signed consent forms approved by the Human Research Ethics Committees at Edith Cowan University (No. 11543) and Sir Charles Gairdner Hospital (No. 2013–246). The study was performed in accordance with the Declaration of Helsinki.

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Data availability

Raw data is available upon request.

Competing interests

The authors declare no competing interests.

Funding infromation

This study was funded by a National Health and Medical Research Council (NHMRC) grant 1013349 to M.Z., a Cancer Council WA (CCWA) grant to E.S.G., M.Z., M.Mi. and C.A.B., a CCWA Suzanne Cavanagh Early Career Investigator (2016) to C.A.B. as well as an Edith Cowan University Early Career Research grant (2016) to C.A.B. E.S.G. was supported by fellowships from the Cancer Research Trust and CCWA. A.C.M. was supported by a Western Australian Health Translation Early Career Fellowship.

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Aya-Bonilla, C.A., Morici, M., Hong, X. et al. Detection and prognostic role of heterogeneous populations of melanoma circulating tumour cells. Br J Cancer (2020).

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