Targeted degradation of hexokinase 2 by a novel engineered bispecific chimeric liposome-based Nano-PROTACs for enhancing tumor chemotherapy

Aerobic glycolysis is critical for tumor development and metastasis. Regulating the activity of vital metabolic enzymes in the tumor glycolysis process, such as hexokinase 2 (HK-2), is expected for tumor treatment. However, conventional small molecule inhibitors only block the activity of proteases with consistently high doses via occupation-driven pattern, leading to off-target effects which limit their clinical application. Herein, we reported a novel engineered bispecific chimeric liposome-based Nano-proteolysis targeting chimeras (LIPOTAC) for HK-2 degradation. LIPOTAC consisted of three parts containing HK-2 binding moiety, E3 ubiquitin ligase binder and liposome vehicle. It was worth noting that in this system, on the one hand, liposomes played a role similar to linker in proteolysis targeting chimeras (PROTACs), achieving flexible regulation of targeting probes ratio, and on the other hand, liposomes could enhance tumor accumulation and cellular uptake compared to traditional small molecule PROTACs. Then, LIPOTAC could bind to HK-2, hijack cereblon (CRBN) to induce HK-2 ubiquitination, and efficiently degrade HK-2 with proteasomes in the cytoplasm of tumor cell. More than 91 % or 82 % of HK-2 in B16F10 or 4T1 tumor cells could be degraded by LIPOTAC, respectively. Moreover, doxorubicin (DOX) was remote-loaded into LIPOTAC vesicle via an ammonium sulfate gradient method for enhancing the anti-tumor effect of LIPOTAC, named DOX@LIPOTAC. DOX@LIPOTAC effectively induced tumor cell apoptosis in vitro, triggered targeted proteolysis of HK-2 and inhibited the growth of B16F10 and 4T1 cell-derived xenograft tumors and prevented lung metastasis in the orthotopic 4T1-luciferase tumor-bearing mouse model, while minimized systemic side effects. The persistent HK-2 degradation strategy boosted tumor aerobic glycolysis inhibition for synergistic enhancement of tumor chemotherapy. Therefore, our study offers new insights into how to regulate tumor glucose metabolism through an innovative protein degradation strategy for cancer treatment.