Exploring the role of BRAFV600E in melanoma immune microenvironment and its impact on modulating the IFN-1 pathway for therapeutic response

Abstract

The BRAFV600E mutation, found in approximately 50% of melanoma cases, is associatedwith aggressive tumor behavior and poor prognosis. This study aimed to assess its impact onimmunogenic cell death (ICD), a pivotal cytotoxic process triggering anti-tumor immune responses.Through comprehensive in silico analysis of The Cancer Genome Atlas data, we explored theassociation between the BRAFV600E mutation, immune subtype dynamics, and tumor mutationburden (TMB). Our findings revealed that the mutation correlated with a lower TMB, indicating areduced generation of immunogenic neoantigens. Investigation into immune subtypes reveals anexacerbation of immunosuppression mechanisms in BRAFV600E-mutated tumors. To assess theresponse to ICD inducers, including doxorubicin and Me-ALA-based photodynamic therapy (PDT),compared to the non-ICD inducer cisplatin, we used distinct melanoma cell lines with wild-typeBRAF (SK-MEL-2) and BRAFV600E mutation (SK-MEL-28, A375). We demonstrated a differentialresponse to PDT between the WT and BRAFV600E cell lines. Further transcriptomic analysisrevealed upregulation of IFNAR1, IFNAR2, and CXCL10 genes associated with the BRAFV600Emutation, suggesting their involvement in ICD. Using a gene reporter assay, we showed that PDTrobustly activated the IFN-1 pathway through cGAS-STING signaling. Collectively, our resultsunderscore the complex interplay between the BRAFV600E mutation and immune responses,emphasizing a putative correlation between tumors carrying the mutation and their responsivenessto therapies inducing the IFN-1 pathway, such as the ICD inducer PDT, possibly mediated by theelevated expression of IFNAR1/2 receptors.