Melanoma spheroids grown under neural crest cell conditions are highly plastic migratory/invasive tumor cells endowed with immunomodulator function

PLoS One. 2011 Apr 15;6(4):e18784. doi: 10.1371/journal.pone.0018784.

Abstract

Background: The aggressiveness of melanoma tumors is likely to rely on their well-recognized heterogeneity and plasticity. Melanoma comprises multi-subpopulations of cancer cells some of which may possess stem cell-like properties. Although useful, the sphere-formation assay to identify stem cell-like or tumor initiating cell subpopulations in melanoma has been challenged, and it is unclear if this model can predict a functional phenotype associated with aggressive tumor cells.

Methodology/principal findings: We analyzed the molecular and functional phenotypes of melanoma spheroids formed in neural crest cell medium. Whether from metastatic or advanced primary tumors, spheroid cells expressed melanoma-associated markers. They displayed higher capacity to differentiate along mesenchymal lineages and enhanced expression of SOX2, NANOG, KLF4, and/or OCT4 transcription factors, but not enhanced self-renewal or tumorigenicity when compared to their adherent counterparts. Gene expression profiling attributed a neural crest cell signature to these spheroids and indicated that a migratory/invasive and immune-function modulating program could be associated with these cells. In vitro assays confirmed that spheroids display enhanced migratory/invasive capacities. In immune activation assays, spheroid cells elicited a poorer allogenic response from immune cells and inhibited mitogen-dependent T cells activation and proliferation more efficiently than their adherent counterparts. Our findings reveal a novel immune-modulator function of melanoma spheroids and suggest specific roles for spheroids in invasion and in evasion of antitumor immunity.

Conclusion/significance: The association of a more plastic, invasive and evasive, thus a more aggressive tumor phenotype with melanoma spheroids reveals a previously unrecognized aspect of tumor cells expanded as spheroid cultures. While of limited efficiency for melanoma initiating cell identification, our melanoma spheroid model predicted aggressive phenotype and suggested that aggressiveness and heterogeneity of melanoma tumors can be supported by subpopulations other than cancer stem cells. Therefore, it could be constructive to investigate melanoma aggressiveness, relevant to patients and clinical transferability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Differentiation / drug effects
  • Cell Lineage / drug effects
  • Cell Movement* / drug effects
  • Cell Proliferation / drug effects
  • Culture Media / pharmacology
  • Embryonic Stem Cells / drug effects
  • Embryonic Stem Cells / metabolism
  • Gene Expression Profiling
  • Gene Expression Regulation, Neoplastic / drug effects
  • Genes, Neoplasm
  • Humans
  • Immunomodulation* / drug effects
  • Melanoma / genetics
  • Melanoma / immunology*
  • Melanoma / pathology*
  • Neoplasm Invasiveness
  • Neoplastic Stem Cells / drug effects
  • Neoplastic Stem Cells / metabolism
  • Neoplastic Stem Cells / pathology
  • Neural Crest / drug effects
  • Neural Crest / metabolism
  • Neural Crest / pathology*
  • Phenotype
  • Pluripotent Stem Cells / drug effects
  • Pluripotent Stem Cells / metabolism
  • Spheroids, Cellular / drug effects
  • Spheroids, Cellular / metabolism
  • Spheroids, Cellular / pathology*
  • Transcription Factors / metabolism
  • Transcription, Genetic / drug effects
  • Tumor Cells, Cultured

Substances

  • Culture Media
  • Transcription Factors