CMTM6 maintains B cell-intrinsic CD40 expression to regulate anti-tumor immunity

Tumor cell CMTM6 is a novel tumor immunoregulator involved in maintaining membrane levels of several important molecules, such as PD-L1 and CD58. Host CMTM6 may also play a function in the tumor microenvironment. Here, we found that CMTM6 was highly expressed in splenic B cells and tumor-infiltrating B cells. CMTM6 deficiency resulted in impaired splenic development, germinal center B cell differentiation, memory B cell differentiation, and B cell anti-tumor immune responses. Through multi-omics data mining and B-cell agonist screening, we identified that CMTM6 interacted with CD40 and maintained CD40 membrane levels in B cells. CMTM6 regulated CD40 at the post-translational modification stage but not at the transcriptional stage. CMTM6 deficiency led to impaired CD40 signaling-mediated B cell activation, survival, proliferation, and differentiation. In vivo, CMTM6 deficiency leads to a significant decrease in the anti-tumor activity of B cell-dependent CD40 agonists. Collectively, B-cell intrinsic CMTM6 maintains B cell CD40 levels and signaling to promote B cell function and anti-tumor immunity.

Highlights

• B cells participate in anti-tumor immunity by influencing the intratumoral infiltration and function of T cells;

• CMTM6 cis-interacts with CD40 to maintain CD40 cell membrane levels;

• Loss of B cell-intrinsic CMTM6 significantly reduces CD40 signaling-mediated B cell activation, survival, and differentiation;

• CMTM6 deficiency leads to a significant reduction in the anti-tumor activity of B cells and CD40 agonists.

In Brief

Long et al. demonstrate that B-cell intrinsic CMTM6 regulates CD40 signaling and function via maintaining the cell membrane level of B-cell CD40 through a post-translational modification pathway, thereby affecting anti-tumor B-cell immunity and the efficacy of CD40 agonist.