CircMAPK1 promoted CD8 + T cell infiltration in LUAD by improving the IGF2BP1 dependent CCL5 upregulation

Lung adenocarcinoma (LUAD) is the most common pathological subtype of lung cancer and has a poor prognosis. Immune Checkpoint Blockage (ICB) have been shown to improve the survival of LUAD in the last decade. CD8 + T cell infiltration is significantly related to LUAD prognosis and plays a critical role in ICB response efficiency. Chemokines expressed and secreted by tumor and microenvironment cells regulate the recruitment of CD8 + T cells. A cytoplasm-dominant circRNA, termed circMAPK1, was found to be down-regulated in LUAD and dramatically suppressed the growth of LUAD upon circMAPK1 overexpression in immunocompetent mice. Meanwhile, it was found that circMAPK1 significantly promoted the CD8 + T cell intratumoral infiltration in vitro and in vivo. CircMAPK1 was identified as binding IGF2BP1 in the cytoplasm and inducing IGF2BP1 to occupy the 3′UTR of CCL5 mRNA, resulting in retained stability of CCL5 mRNA. In general, circMAPK1 is a microenvironment-associated circRNA that recruits CD8 + T cells in LUAD. CircMAPK1 is an effective microenvironment regulator and a potential nucleic acid drug that can be combined with ICB to improve immunotherapy response efficiency.