Advanced Cancer Starvation Therapy by Simultaneous Deprivation of Lactate and Glucose Using a MOF Nanoplatform

Abstract

Recent investigations reveal that lactate is not a waste product but a major energy source for cells, especially in the mitochondria, which can support cellular survival under glucose shortage. Accordingly, the new understanding of lactate prompts to target it together with glucose to pursue a more efficient cancer starvation therapy. Herein, zeolitic imidazolate framework-8 (ZIF-8) nanoplatforms are used to co-deliver α-cyano-4-hydroxycinnamate (CHC) and glucose oxidase (GOx) and fulfill the task of simultaneous depriving of lactate and glucose, resulting in a new nanomedicine CHC/GOx@ZIF-8. The synthesis conditions are carefully optimized in order to yield monodisperse and uniform nanomedicines, which will ensure reliable and steady therapeutic properties. Compared with the strategies aiming at a single carbon source, improved starvation therapy efficacy is observed. Besides, more than boosting the energy shortage, CHC/GOx@ZIF-8 can block the lactate-fueled respiration and relieve solid tumor hypoxia, which will enhance GOx catalysis activity, depleting extra glucose, and producing more cytotoxic H₂ O₂ . By the synergistically enhanced anti-tumor effect, both in vitro and in vivo cancer-killing efficacies of CHC/GOx@ZIF-8 show twice enhancements than the GOx mediated therapy. The results demonstrate that the dual-depriving of lactate and glucose is a more advanced strategy for strengthening cancer starvation therapy.

Keywords: glucose; lactate; metal-organic frameworks; monocarboxylate transporter 1; starvation therapy.

Scheme 1

The intracellular therapeutic mechanisms of A) GOx mediated cancer starvation therapy and B) dual‐depriving cancer starvation therapy (glucose is depleted by GOx and the cellular influx of exogenous lactate is blocked by MCT1 inhibitor, CHC). Both therapies are conducted by the ZIF‐8 nanoplatforms.

Figure 1

Lactate can preserve cellular survival under glucose starvation. A) Cell proliferation after incubation with different concentrations of lactate for different periods. B) Lactate concentration of the cell culture medium after different incubation periods. C–F) Cell proliferation after incubation with different concentrations of GOx@ZIF‐8 for 24, 48, 72, and 96 h in media containing glucose (10 mm) or glucose (10 mm) + lactate (5 mm). Data are presented as mean ± SD, n = 3, *p < 0.05, **p < 0.01, and ***p < 0.001. Cells without any treatment were set as the control group and cell proliferation of the control group was set as 100%.

Figure 2

Fine‐tune the crystal morphology of CHC@ZIF‐8 by increasing the usage of DMF and 2‐MIM. SEM images of A) CHC@ZIF‐8 crystals synthesized at Zn²⁺:2‐MIM:H₂O molar ratio of 1:70:1245 with increasing dosages of CHC from a) to c). B) CHC@ZIF‐8 crystals synthesized at Zn²⁺:CHC:2‐MIM:H₂O molar ratio of 1:0.36:70:1245 with increasing dosages of DMF from a) to c) and C) CHC@ZIF‐8 crystals synthesized at Zn²⁺:CHC:H₂O:DMF molar ratio of 1:0.36:1245:50 with increasing dosages of 2‐MIM from a) to c). D) Illustration of the a) crystallization process of ZIF‐8 crystals in aqueous, b) strengthened protonation of 2‐MIM by CHC, and c) promoted deprotonation of 2‐MIM by DMF. Scale bar: 1 µm.

Figure 3

Synthesis and characterization of CHC/GOx@ZIF‐8 crystals. A) Illustration of the one‐pot synthesis of CHC/GOx@ZIF‐8. B) TEM images with size distribution and C) SEM images of CHC/GOx@ZIF‐8 crystals. D) Hydrodynamic size distribution, E) zeta potential, F) FT‐IR absorption spectra, G) PXRD, H) BET, and I) TGA absorption spectra of ZIF‐8, CHC@ZIF‐8, and CHC/GOx@ZIF‐8. J) SDS‐PAGE analysis of GOx loading efficiency in GOx@ZIF‐8 and CHC/GOx@ZIF‐8. K) Kinetics of TMB oxidation catalyzed by free GOx and GOx released from CHC/GOx@ZIF‐8. L) The pH‐dependent release profile of CHC/GOx@ZIF‐8. Scale bar in Figure 3B,C: 1 µm. Scale bar in the inserts of Figure 3B,C: 100 nm.

Figure 4

A–C) Cell proliferation and D–F) metabolism profiles of cells incubated with CHC@ZIF‐8 (A,D), GOx@ZIF‐8 (B,E), and CHC/GOx@ZIF‐8 (C,F) in medium containing glucose (10 mm) and lactate (10 mm). Data are presented as mean ± SD, n = 3. Cells without any treatment were set as the control group and cell proliferation of the control group was set as 100%.

Figure 5

A) Lactate and B) O₂ consumption profile of cells after different treatment. C) LSCM images and D) FCM analysis of cells stained with DCFH‐DA after incubation with CHC@ZIF‐8, GOx@ZIF‐8, and CHC/GOx@ZIF‐8 for 6 h. E) FCM analysis of cellular apoptosis and F) LSCM images of live/dead cells stained with calcein‐AM (green)/PI (red) after incubation with CHC@ZIF‐8, GOx@ZIF‐8, and CHC/GOx@ZIF‐8 for 24 h. Cell culturing media for this part are DMEM with 10% FBS, glucose (10 mm), and lactate (10 mm). Scale bar in Figure 5C,F: 100 µm.

Figure 6

Efficient cancer starvation therapy by CHC/GOx@ZIF‐8 in vivo. A) Tumor growth curves and B) mice bodyweights after different treatment. C) Tumor weight and D) the corresponding photograph 16 days after different treatment. E) Lactate content in fresh tumors 24 h after different treatment. F) Immune fluorescence analysis of HIF‐1α of tumors 24 h after treatment with PBS and CHC/GOx@ZIF‐8. G) H&E staining, H) TUNEL analysis, and I) immune‐fluorescence analysis of caspase‐3 of tumors 24 h after the treatment with a) PBS, b) CHC@ZIF‐8, c) GOx@ZIF‐8, d) and CHC/GOx@ZIF‐8. Scale bar: 200 µm. Data are presented as mean ± SD, n = 3, p < 0.05, *p < 0.01.