Autophagy is an evolutionarily-conserved catabolic process initiated by the engulfment of cytosolic components in a crescent-shaped structure, called the phagophore, that expands and fuses to form a closed double-membrane vesicle, the autophagosome. Autophagosomes are subsequently targeted to the lysosome/vacuole with which they fuse to degrade their content. The formation of the autophagosome is carried out by a set of autophagy-related proteins (Atg), highly conserved from yeast to mammals. The Atg8s are Ubl (ubiquitin-like) proteins that play an essential role in autophagosome biogenesis. This family of proteins comprises a single member in yeast and several mammalian homologues grouped into three subfamilies: LC3 (light-chain 3), GABARAP (γ-aminobutyric acid receptor-associated protein) and GATE-16 (Golgi-associated ATPase enhancer of 16 kDa). The Atg8s are synthesized as cytosolic precursors, but can undergo a series of post-translational modifications leading to their tight association with autophagosomal structures following autophagy induction. Owing to this feature, the Atg8 proteins have been widely served as key molecules to monitor autophagosomes and autophagic activity. Studies in both yeast and mammalian systems have demonstrated that Atg8s play a dual role in the autophagosome formation process, coupling between selective incorporation of autophagy cargo and promoting autophagosome membrane expansion and closure. The membrane-remodelling activity of the Atg8 proteins is associated with their capacity to promote tethering and hemifusion of liposomes in vitro.

Chimeric antigen receptor (CAR) T-cell therapy has shown remarkable successes in fighting B-cell leukemias/lymphomas. Promising response rates are reported in patients treated with B-cell maturation antigen (BCMA) CAR T cells for multiple myeloma. However, responses appear to be nondurable, highlighting the need to expand the repertoire of multiple myeloma–specific targets for immunotherapy and to generate new CAR T cells. Here, we developed a “dual-CAR” targeting two multiple myeloma–associated antigens and explored its safety and efficacy. To reduce the “off-target” toxicity, we used the recognition of paired antigens that were coexpressed by the tumor to induce efficient CAR T-cell activation. The dual-CAR construct presented here was carefully designed to target the multiple myeloma–associated antigens, taking into consideration the distribution of both antigens on normal human tissues. Our results showed that the CD138/CD38-targeted dual CAR (dCAR138-38) elicited a potent anti–multiple myeloma response both in vitro and in vivo. NSG mice transplanted with a multiple myeloma cell line and treated with dCAR138-38 showed median survival of 97 days compared with 31 days in the control group treated with mock-lymphocytes. The dCAR138-38 showed increased specificity toward cells expressing both targeted antigens compared with single-antigen–expressing cells and low activity toward primary cells from healthy tissues. Our findings indicated that the dCAR138-38 may provide a potent and safe alternative therapy for patients with multiple myeloma.