Abstract
Purpose: :
Uveal melanoma (UM) is the most common primary cancer of the eye and frequently leads to metastatic death. UM is notoriously resistant to chemotherapy and radiation therapy. Cancer stem cells confer treatment resistance in many cancers, and our previous work showed that class 2 UMs (with high metastatic risk) exhibit transcriptional similarity to primitive neural and ectodermal stem cells. Therefore, we wished to isolate the UM stem cells for their further functional characterization.
Methods: :
Flow cytometry of primary and cultured UM cells was performed using Hoechst dye exclusion, ALDH enzymatic activity, and chemotherapy shift assays. Stem cell characteristics were assessed based on mRNA expression of stem cell markers, soft agar clonogenic and self-renewal assays, and differentiation plasticity assays.
Results: :
A sub-population of UM cells ranging from 0.2% to 7.8% of the total cell population was identified that met several criteria for cancer stem cells, including enrichment for stem cell markers such as Oct4, higher self-renewal and clone-forming capacity. This sub-population demonstrated multipotency and lineage plasticity, being able to differentiate along the chondrocyte and neuronal, as well as melanocyte, lineages.
Conclusions: :
This study confirms the presence of cancer stem cells in UM. Since cancer stem cells are highly resistant to chemotherapy and radiation, these cells may be a major cause of treatment resistance of UM, particularly in metastatic disease. Therapeutic strategies that target these stem cells may lead to significant improvements in the ability to treat UM and prolong survival.
Keywords: melanoma • tumors • melanocytes