Deficiency of MRPL57 in acute myeloid leukemia patients leads to suboptimal therapeutic outcomes with CAR-T cell therapy

Abstract Background: CAR-T cells therapy has achieved breakthrough success in acute lymphoblastic leukemia (ALL), but its efficacy remains poor in acute myeloid leukemia (AML). Current research efforts are focused on enhancing CAR-T cells persistence, overcoming the immunosuppressive tumor microenvironment (TME), and improving metabolic fitness to boost therapeutic efficacy in AML. Among the components of the TME, serum-derived factors have emerged as critical modulators of CAR-T cells function. Our study investigates serum-derived molecular differences between ALL and AML patients that may account for differential CAR-T cells therapy responses. Methods: This study first investigated the impact of serum-free co-culture conditions and co-culture conditions supplemented with serum from healthy donors (HD), ALL patients, or AML patients on the anti-tumor activity of CD19 CAR-T cells and CD33 CAR-T cells in vitro. Subsequently, secretome analysis was used to identify and compare differences in serum secretory proteins between ALL and AML patients. The effect of targeted intervention of the identified target protein on the anti-tumor function of CD19 CAR-T cells and CD33 CAR-T cells was then assessed. Results:(1) CD19 CAR-T cells exhibited poor killing efficacy against co-cultured ALL cells in serum-free medium or medium supplemented with AML patient serum, but demonstrated potent killing in medium supplemented with HD serum or ALL patient serum. (2) CD33 CAR-T cells exhibited poor killing efficacy against co-cultured AML cells in serum-free medium or medium supplemented with AML patient serum, but demonstrated potent killing in medium supplemented with HD serum or ALL patient serum. (3) Secretome analysis revealed significantly lower expression of mitochondrial ribosomal proteins (MRPs), particularly mitochondrial ribosomal large subunit protein 57 (MRPL57), in AML patient serum compared to ALL patient serum. (4) Inhibiting MRPL57 in serum from ALL patients significantly downregulated the anti-tumor killing ability of CD19 CAR-T cells against ALL cells. (5) Supplementing MRPL57 into serum from AML patients significantly upregulated the anti-tumor killing ability of CD33 CAR-T cells against AML cells. (6) MRPL57 supplementation enhanced the proportion and proliferative potential of stem cell-like central memory T cells in CAR-T populations via mitochondrial translation, and promoted the release of granzyme B and perforin. Conclusion: AML patients exhibit a significant deficiency in endogenous MRPL57 production that leads to suboptimal therapeutic outcomes with CAR-T cells therapy, which highlights a novel metabolic and microenvironmental axis to improve CAR-T cells efficacy in AML.