FOXD3 Regulates VISTA Expression in Melanoma

Area of Science:

• Immunology
• Oncology
• Cancer Biology

Background:

• Immune checkpoint inhibitors (ICIs) have advanced melanoma treatment, yet intrinsic resistance highlights the need for novel immune targets.
• V-domain Ig suppressor of T cell activation (VISTA) is an immune checkpoint protein with limited characterization, especially regarding its role in cancer cells.

Purpose of the Study:

• To investigate VISTA expression and regulation in melanoma cells.
• To determine the functional impact of VISTA expression on tumor development and the tumor microenvironment.
• To explore the relationship between VISTA, stemness factors, and BRAF inhibition in melanoma.

Main Methods:

• Analysis of VISTA expression in melanoma patient samples and cell lines.
• In vivo studies to assess the effect of tumor cell-specific VISTA expression on tumor onset.
• Evaluation of immune cell infiltration, including T regulatory cells and macrophages, within tumors.
• Assessment of PDL-1 expression on tumor-infiltrating macrophages.
• Investigation of VISTA regulation by the stemness factor FOXD3.
• Analysis of the impact of BRAF inhibition on FOXD3 and VISTA levels.

Main Results:

• VISTA is expressed in melanoma patient samples and cell lines.
• Tumor cell-specific VISTA expression accelerates tumor initiation in vivo.
• VISTA expression correlates with increased intratumoral T regulatory cells and enhanced PDL-1 expression on tumor-infiltrating macrophages.
• VISTA transcript levels are negatively regulated by the stemness factor FOXD3.
• BRAF inhibition leads to increased FOXD3 expression and decreased VISTA expression.

Conclusions:

• Melanoma cells express VISTA, which contributes to tumor progression.
• FOXD3 acts as a regulator of VISTA expression in melanoma.
• These findings support therapeutic strategies combining targeted BRAF inhibitors with immune checkpoint blockade for improved melanoma treatment.