Tumor-targeted therapy with BRAF-inhibitor recruits activated dendritic cells to promote tumor immunity in melanoma.

Abstract

BACKGROUND:

Tumor-targeted therapy causes impressive tumor regression, but the emergence of resistance limits long-term survival benefits in patients. Little information is available on the role of the myeloid cell network, especially dendritic cells (DC) during tumor-targeted therapy.

METHODS:

Here, we investigated therapy-mediated immunological alterations in the tumor microenvironment (TME) and tumor-draining lymph nodes (LN) in the D4M.3A preclinical melanoma mouse model (harboring the V-Raf murine sarcoma viral oncogene homolog B (BRAF)V600E mutation) by using high-dimensional multicolor flow cytometry in combination with multiplex immunohistochemistry. This was complemented with RNA sequencing and cytokine quantification to characterize the immune status of the tumors. The importance of T cells during tumor-targeted therapy was investigated by depleting CD4+ or CD8+ T cells in tumor-bearing mice. Tumor antigen-specific T-cell responses were characterized by performing in vivo T-cell proliferation assays and the contribution of conventional type 1 DC (cDC1) to T-cell immunity during tumor-targeted therapy was assessed using Batf3-/- mice lacking cDC1.

RESULTS:

Our findings reveal that BRAF-inhibitor therapy increased tumor immunogenicity, reflected by an upregulation of genes associated with immune activation. The T cell-inflamed TME contained higher numbers of activated cDC1 and cDC2 but also inflammatory CCR2-expressing monocytes. At the same time, tumor-targeted therapy enhanced the frequency of migratory, activated DC subsets in tumor-draining LN. Even more, we identified a cDC2 population expressing the Fc gamma receptor I (FcγRI)/CD64 in tumors and LN that displayed high levels of CD40 and CCR7 indicating involvement in T cell-mediated tumor immunity. The importance of cDC2 is underlined by just a partial loss of therapy response in a cDC1-deficient mouse model. Both CD4+ and CD8+ T cells were essential for therapy response as their respective depletion impaired therapy success. On resistance development, the tumors reverted to an immunologically inert state with a loss of DC and inflammatory monocytes together with the accumulation of regulatory T cells. Moreover, tumor antigen-specific CD8+ T cells were compromised in proliferation and interferon-γ-production.

CONCLUSION:

Our results give novel insights into the remodeling of the myeloid landscape by tumor-targeted therapy. We demonstrate that the transient immunogenic tumor milieu contains more activated DC. This knowledge has important implications for the development of future combinatorial therapies.

• Authors: Florian Hornsteiner, Janine Vierthaler, Helen Strandt, Antonia Resag, Zhe Fu, Markus Ausserhofer, Christoph H Tripp, Sophie Dieckmann, Markus Kanduth, Kathryn Farrand, Sarah Bregar, Niloofar Nemati, Natascha Hermann-Kleiter, Athanasios Seretis, Sudhir Morla, David Mullins, Francesca Finotello, Zlatko Trajanoski, Guido Wollmann, Franca Ronchese, Marc Schmitz, Ian F Hermans, Patrizia Stoitzner
• Journal: Journal for immunotherapy of cancer (J Immunother Cancer) Vol. 12 Issue 4 (Apr 17 2024) ISSN: 2051-1426 [Electronic] England
• PMID: 38631706 (Publication Type: Journal Article)
• Copyright: © Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ.

Chemical References

• Proto-Oncogene Proteins B-raf
• Antigens, Neoplasm
• BRAF protein, human

Topics

• Humans
• Animals
• Mice
• Melanoma (metabolism)
• CD8-Positive T-Lymphocytes
• Proto-Oncogene Proteins B-raf (genetics)
• Dendritic Cells
• Antigens, Neoplasm
• Tumor Microenvironment