Hypoxia increases the heterogeneity of melanoma cell populations and affects the response to vemurafenib

Mol Med Rep. 2016 Apr;13(4):3281-8. doi: 10.3892/mmr.2016.4888. Epub 2016 Feb 10.

Abstract

A hypoxic microenvironment is one of the predominant reasons for incomplete response to melanoma treatment. Vemurafenib, which targets the mutated BRAF-V600 kinase, improves melanoma patient survival, however, resistance invariably develops. The present study evaluated the effect of hypoxia on three BRAF-V600E mutant melanoma cell lines, M14, A375 and 518A2, treated with vemurafenib. Compared with the other two cell lines, hypoxic vemurafenib-treated A375 cells exhibited an enhanced cell proliferation rate and migratory capacity compared with normoxic vemurafenib-treated A375 cells. Immunoblotting analyses revealed that the expression levels of hypoxia inducible factor (HIF)1α and carbonic anhydrase IX were reduced in vemurafenib‑treated M14 and 518A2 cells, however, not in A375 cells. The expression levels of the mitogen‑activated protein kinase, Janus kinase-signal transducer and activator of transcription, and phosphatidylinositol-4,5-bisphosphate 3‑kinase signaling pathway proteins revealed a cell‑type specific response to vemurafenib and hypoxia. Knockdown experiments of HIF1α performed in hypoxic A375 cells decreased the expression of phosphorylated (p‑)protein kinase B, which was restored following vemurafenib treatment, and increased the expression of p‑extracellular‑signal‑regulated kinases. Therefore, three melanoma cell lines responded to vemurafenib under hypoxia in a cell type‑specific manner, suggesting that a subset of cells provides a treatment-resistant pool, from which disease relapse may originate. These data confirmed that vemurafenib may be successful in treating the proliferating cells, whereas the non‑proliferating subpopulation must be addressed by a combination of vemurafenib with other treatment strategies.

MeSH terms

  • Antigens, Neoplasm / genetics
  • Antigens, Neoplasm / metabolism
  • Antineoplastic Agents / pharmacology*
  • Carbonic Anhydrase IX / genetics
  • Carbonic Anhydrase IX / metabolism
  • Cell Hypoxia*
  • Cell Line, Tumor
  • Cell Movement
  • Cell Proliferation
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / antagonists & inhibitors
  • Hypoxia-Inducible Factor 1, alpha Subunit / genetics
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism
  • Indoles / pharmacology*
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Melanoma / metabolism
  • Melanoma / pathology
  • Oxygen Consumption
  • Phosphatidylinositol 3-Kinases / metabolism
  • Proto-Oncogene Proteins B-raf / genetics
  • Proto-Oncogene Proteins B-raf / metabolism*
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA Interference
  • RNA, Small Interfering / metabolism
  • Real-Time Polymerase Chain Reaction
  • Signal Transduction / drug effects
  • Sulfonamides / pharmacology*
  • Vemurafenib

Substances

  • Antigens, Neoplasm
  • Antineoplastic Agents
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Indoles
  • RNA, Small Interfering
  • Sulfonamides
  • Vemurafenib
  • Phosphatidylinositol 3-Kinases
  • Proto-Oncogene Proteins B-raf
  • Proto-Oncogene Proteins c-akt
  • Extracellular Signal-Regulated MAP Kinases
  • JNK Mitogen-Activated Protein Kinases
  • CA9 protein, human
  • Carbonic Anhydrase IX