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MEK inhibition, alone or in combination with BRAF inhibition, impairs multiple functions of isolated normal human lymphocytes and dendritic cells
  1. Laura J Vella1,
  2. Anupama Pasam1,
  3. Nektaria Dimopoulos1,
  4. Miles Andrews1,
  5. Anne-Laure Puaux2,
  6. Jamila Louahed2,
  7. Ashley Knights1,
  8. Weisan Chan3,
  9. Katherine Woods1 and
  10. Jonathan Cebon1
  1. Aff1 grid.414094.c0000000101627225The Ludwig Institute for Cancer Research Melbourne VIC Australia
  2. Aff2 grid.425090.aGlaxoSmithKline Rixensart Belgium
  3. Aff3 grid.1018.80000000123420938La Trobe University Melbourne VIC Australia

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Meeting abstracts


Combination therapy with BRAF and MEK inhibition is currently in clinical development for the treatment of BRAF mutated malignant melanoma. BRAF inhibitors are associated with enhanced antigen-specific T-lymphocyte recognition in vivo. Consequently BRAF inhibition has been proposed as pro-immunogenic and there has been considerable enthusiasm for combining BRAF inhibition with immunotherapy. MEK inhibitors inhibit ERK phosphorylation regardless of BRAF mutational status and have been reported to impair T-lymphocyte and dendritic cell function. In this study we investigate the effects on isolated T-lymphocytes and monocyte-derived dendritic cells (moDCs) of a MEK and BRAF inhibitor combination currently being evaluated in a randomized controlled clinical trial.

Experimental design

The effects of a BRAF inhibitor and a MEK inhibitor, alone and in combination were studied on isolated normal T-lymphocyte and moDCs. Lymphocyte viability, together with functional assays including proliferation, cytokine production and antigen-specific expansion, were assessed. moDC phenotype in response to lipo-polysaccharide stimulation was evaluated by flow-cytometry, as were effects on antigen crosspresentation.


BRAF inhibition did not have an impact on T-lymphocytes or moDCs, whereas MEK inhibition alone or in combination with BRAF inhibition suppressed T-lymphocyte proliferation, cytokine production and antigen-specific expansion. Similarly, moDC cross-presentation was suppressed in association with enhanced maturation following combined inhibition of MEK and BRAF. However no significant decrease in CD4+ or CD8+ T-lymphocyte viability was observed following kinase inhibition.


MEK inhibition, alone or in combination with BRAF inhibition can suppress immune cell function and further studies in vivo will be required to evaluate the potential clinical impact of these findings.