Characterisation of the melanosphere CD20 sub-population

ABSTRACT: Background: Mutant BRAF targeted therapies remain a standard of care for the treatment of metastatic malignant melanoma (MM); however high initial response rates are tempered by the persistence of residual MM cells that eventually lead to disease recurrence and mortality. Since MM recurrence during targeted therapy can present with the simultaneous occurrence of multiple tumour nodules at the original body sites, we hypothesised the presence of an intrinsically resistant MM cell sub-population. Objectives: Identify an MM cell subpopulation that is intrinsically resistant to targeted therapy and so may be responsible for MM recurrence. Methods: Using melanoma cell lines, we define culture conditions for reproducible 3D growth of melanospheres to investigate putative cancer stem cell populations. We undertook RNA sequencing and bioinformatic analysis to characterise cell populations between adherent and non-adherent culture, and cells expressing or not expressing CD20. Furthermore, we define an in vitro assay to evaluate killing of melanoma cancer stem cells as a therapeutic test using combination therapies targeting driver mutation and CD20 marker. Results: We have described culture conditions that promote MM cells to form melanospheres with a reproducible colony forming efficiency of 0.3% to 1.3%. RNA sequencing of melanosphere versus conventional MM cell cultures (n=6), irrespective of the BRAF mutation status, showed that melanosphere formation was associated with growth and differentiation transcriptional signatures resembling MM tumours. Importantly, melanosphere formation also led to the emergence of a CD20+ MM cell subpopulation, similar to that observed in primary human MM tumours. CD20+ MM cells were resistant to BRAF inhibitor therapy, and consistent with this finding demonstrated a Forkhead box protein M1 (FOXM1) transcriptomic profile (n=6). Combining BRAF inhibitor and anti-CD20 antibody treatment led to the additional killing of previously resistant CD20+ BRAF mutant MM cells. Conclusions: In MM patients that harbour a CD20+ sub-population, combined therapy with BRAF inhibitor and anti-CD20 antibody could potentially kill residual MM cells and so prevent disease recurrence.

ORGANISM(S): Homo sapiens

PROVIDER: GSE248906 | GEO | 2024/02/22

REPOSITORIES: GEO