Nanostring nCounter Myeloid Innate Immunity analysis of CD8 T cells cultured with conditioned media

However, the precise factors that shape the immune contexture of the TME remain elusive. Here, we report that Single-Stranded DNA Binding Protein 4 (SSBP4), a previously uncharacterized protein, suppresses intratumoral T-cell activation by promoting excessive cholesteryl ester production in tumor cells.

Overexpression of SSBP4 in tumor cells decreased T-cell infiltration and accelerated tumor growth in murine syngeneic tumor models. Conversely, genetic ablation of SSBP4 in tumor cells enhanced T-cell infiltration and inhibited tumor growth in a CD8+ T cell–-dependent manner. Mechanistically, SSBP4 upregulated cholesterol synthesis genes, leading to increased production of cholesterol and cholesteryl esters in tumor cells, which directly suppressed CD8+ T-cell activation and function.