Project description:The BRAFV600E mutant melanoma cell line M14 responds to the BRAF inhibitor vemurafenib, however, the differences in response between individual cells are underlying resistance. To highlight the underlying mechanisms, we performed treatment of M14 cells with vemurafenib, followed by Drop-seq. We were able to clearly distinguish cells that were treated with the drug from untreated cells, and we discovered different cell populations within the treated cells, likely reflecting heterogeneity of drug resistant cells. We were able to identify specific biomarkers, as preferentially expressed genes, for each cell population. The results of our study will address preexisting and acquired drug resistance that limits clinical usefulness of targeted strategies.
Project description: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.
Project description:Microarrays were used to examine gene expression differences in four different sub-populations of mammary epithelial cells obtained through flow cytometry of stem cell markers for H2BGFP, CD24, and CD29. The present study aims to find the specific differences between these populations that influence their ability to repopulate mammary structures in vivo during transplantation assays. H2GFP+/CD24+/CD29lo cells were found to be multipotent and able to give rise to mammary structures capable of lactation, and this ability increased dramatically if the recipient mice were pregnant. Total RNA obtained from sorted sub-populations of mammary epithelial cells.