Targeted Therapy Given after Anti-PD-1 Leads to Prolonged Responses in Mouse Melanoma Models through Sustained Antitumor Immunity

Cancer Immunol Res. 2021 May;9(5):554-567. doi: 10.1158/2326-6066.CIR-20-0905. Epub 2021 Mar 2.


Immunotherapy (IT) and targeted therapy (TT) are both effective against melanoma, but their combination is frequently toxic. Here, we investigated whether the sequence of IT (anti-PD-1)→ TT (ceritinib-trametinib or dabrafenib-trametinib) was associated with improved antitumor responses in mouse models of BRAF- and NRAS-mutant melanoma. Mice with NRAS-mutant (SW1) or BRAF-mutant (SM1) mouse melanomas were treated with either IT, TT, or the sequence of IT→TT. Tumor volumes were measured, and samples from the NRAS-mutant melanomas were collected for immune-cell analysis, single-cell RNA sequencing (scRNA-seq), and reverse phase protein analysis (RPPA). scRNA-seq demonstrated that the IT→TT sequence modulated the immune environment, leading to increased infiltration of T cells, monocytes, dendritic cells and natural killer cells, and decreased numbers of tumor-associated macrophages, myeloid-derived suppressor cells, and regulatory T cells. Durable responses to the IT→TT sequence were dependent on T-cell activity, with depletion of CD8+, but not CD4+, T cells abrogating the therapeutic response. An analysis of transcriptional heterogeneity in the melanoma compartment showed the sequence of IT→TT enriched for a population of melanoma cells with increased expression of MHC class I and melanoma antigens. RPPA analysis demonstrated that the sustained immune response induced by IT→TT suppressed tumor-intrinsic signaling pathways required for therapeutic escape. These studies establish that upfront IT improves the responses to TT in BRAF- and NRAS-mutant melanoma models.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Antineoplastic Agents / chemistry
  • Antineoplastic Agents / therapeutic use*
  • CD8-Positive T-Lymphocytes / immunology
  • Cell Line, Tumor
  • Disease Models, Animal
  • Female
  • Imidazoles / chemistry
  • Immunotherapy
  • Melanoma / drug therapy*
  • Melanoma / genetics
  • Melanoma / immunology
  • Mice
  • Mice, Inbred C3H
  • Mice, Inbred C57BL
  • Molecular Targeted Therapy
  • Monomeric GTP-Binding Proteins / antagonists & inhibitors*
  • Monomeric GTP-Binding Proteins / genetics
  • Mutation
  • Oximes / chemistry
  • Programmed Cell Death 1 Receptor / antagonists & inhibitors
  • Proto-Oncogene Proteins B-raf / antagonists & inhibitors*
  • Proto-Oncogene Proteins B-raf / genetics
  • Pyridones / chemistry
  • Pyrimidines / chemistry
  • Pyrimidinones / chemistry
  • Skin Neoplasms / drug therapy*
  • Skin Neoplasms / genetics
  • Skin Neoplasms / immunology
  • Sulfones / chemistry
  • T-Lymphocytes, Regulatory / immunology


  • Antineoplastic Agents
  • Imidazoles
  • Oximes
  • Programmed Cell Death 1 Receptor
  • Pyridones
  • Pyrimidines
  • Pyrimidinones
  • Sulfones
  • trametinib
  • Braf protein, mouse
  • Proto-Oncogene Proteins B-raf
  • Monomeric GTP-Binding Proteins
  • Nras protein, mouse
  • ceritinib
  • dabrafenib