Metabolism in melanoma metastasis

Benserazide is a novel inhibitor targeting PKM2 for melanoma treatment

The M2 splice isoform of pyruvate kinase (PKM2) is a key enzyme for generating pyruvate and ATP in the glycolytic pathway, whereas the role of PKM2 in tumorigenesis remains a subject of debate. In our study, we found PKM2 is highly expressed in melanoma patients and the malignance is positively correlated with high PKM2 activity and glycolytic capability in melanoma cells. Suppression of PKM2 expression by knocking down markedly attenuated malignant phenotype both in vitro and in vivo, and restoration of PKM2 expression in PKM2 depleted cells could rescue melanoma cells proliferation, invasion and metastasis. With the data indicating PKM2 as a potential therapeutic target, we performed screening for PKM2 inhibitors and identified benserazide (Ben), a drug currently in clinical use. We demonstrated that Ben directly binds to and blocks PKM2 enzyme activity, leading to inhibition of aerobic glycolysis concurrent up-regulation of OXPHOS. Of note, despite PKM2 is very similar to PKM1, Ben does not affect PKM1 enzyme activity. We showed that Ben significantly inhibits cell proliferation, colony formation, invasion and migration in vitro and in vivo. The specificity of Ben was demonstrated by the findings that, suppression of PKM2 expression diminishes the efficacy of Ben in inhibition of melanoma cell growth; ectopic PKM2 expression in normal cells sensitizes cells to Ben treatment. Interestingly, PKM2 activity and aerobic glycolysis are upregulated in BRAFi-resistant melanoma cells. As a result, BRAFi-resistant cells exhibit heightened sensitivity to suppression of PKM2 expression or treatment with Ben both in vitro and in vivo.

Recombinant adenovirus expressing a dendritic cell-targeted melanoma surface antigen for tumor-specific immunotherapy in melanoma mice model

Viral vectors represent a potential strategy for the treatment of human malignant tumors. Currently, recombinant adenovirus vectors are commonly used as gene therapy vehicles, as it possesses a proven safety profile in normal human cells. The recombinant adenovirus system has an ability to highly express exogenous genes and increase the stability of the carrier, which is only transiently expressed in the host cell genome, without integrating. Malignant melanoma cells are produced by the skin, and melanocyte tumors that exhibit higher malignant degrees lead to earlier transfer and higher mortality. In the present study, a recombinant adenovirus (rAd) was generated to express Anti-programmed death-1 (rAd-Anti-PD-1) and used to investigate the efficacy in melanoma cells and tumors. The results demonstrated that B16-F10 cell growth was significantly inhibited and the apoptosis incidence rate was markedly promoted following rAd-PD-1 treatment. The present study demonstrated that the production of α and β interferon was increased, which led to the induction of dendritic cell (DCs) maturation in rAd-anti-PD-1-treated mice. The present study indicated that rAd-anti-PD-1 exhibited the ability to generate more cluster of differentiation (CD)4⁺CD8⁺ T cells and induce a PD-1-specific cytotoxic T lymphocyte through DC-targeted surface antigens in mice. This resulted in a further enhanced recognition of melanoma cells due to DCs being targeted by the rAd-anti-PD-1-encoded PD-1. Notably, mice treated with the rAd-anti-PD-1-targeted PD-1 demonstrated an improved protection compared with tumor-bearing mice from the challenge group treated with a recombinant gutless adenovirus and Anti-PD-1. In conclusion, the present study demonstrated that targeting the melanoma surface antigens via the rAd-anti-PD-1-infected tumor cells enhanced the ability of recombinant adenovirus to induce a potent tumor-inhibitory effect and antigen-specific immune response.