Sirt3 restricts tumor initiation via promoting LONP1 deacetylation and K63 ubiquitination.

BACKGROUND: Sirtuin 3 (Sirt3) is a controversial regulator of carcinogenesis. It residents in the mitochondria and gradually decays during aging. In this study, we tried to investigate the role of Sirt3 in carcinogenesis and to explore its involvement in metabolic alteration. METHODS: We generated conditional intestinal epithelium Sirt3-knockout mice by crossing ApcMin/+; Villin-Cre with Sirt3fl/fl (AVS) mice. The deacetylation site of Lon protease-1 (LONP1) was identified with Mass spectrometry. The metabolic flux phenotype was determined by Seahorse bioanalyzer. RESULTS: We found that intestinal epithelial cell-specific ablation of Sirt3 promotes primary tumor growth via stabilizing mitochondrial LONP1. Notably, we newly identified that Sirt3 deacetylates human oncogene LONP1 at N terminal residue lysine 145 (K145). The LONP1 hyperacetylation-mutant K145Q enhances oxidative phosphorylation to accelerate tumor growth, whereas the deacetylation-mutant K145R produces calorie-restriction like phenotype to restrain tumorigenesis. Sirt3 deacetylates LONP1 at K145 and subsequently facilitates the ESCRT0 complex sorting and K63-ubiquitination that resulted in the degradation of LONP1. Our results sustain the notion that Sirt3 is a tumor-suppressor to maintain the appropriate ubiquitination and degradation of oncogene LONP1. CONCLUSION: Sirt3 represents a targetable metabolic checkpoint of oncogenesis, which produces energy restriction effects via maintaining LONP1 K145 deacetylation and subsequent K63 ubiquitination.

Dahuang Fuzi Baijiang decoction restricts progenitor to terminally exhausted T cell differentiation in colorectal cancer.

Obesity increases the risk of colorectal cancer (CRC) by 30%. The obese tumor microenvironment compromises antitumor immunity by eliciting exhausted T cells (Tex). Hypothesizing that Dahuang Fuzi Baijiang decoction (DFB) is a combined classical prescription from the "Synopsis of Prescriptions of the Golden Chamber". We first determined that DFB regresses tumor growth in high-fat diet-induced obese mice by expanding the TIM3- subset with intermediate expression of programmed cell death-1 (PD-1int TIM3- ) and restricting the PD-1hi TIM3+ subset. Transcription factor 1 (TCF1) is highly expressed in the PD-1int TIM3- subset but is absent in PD-1hi TIM3+ cells. We next confirmed that progenitor PD-1int TCF+ cells robustly produce tumor necrosis factor-α (TNFα) and interferon-γ, whereas terminally differentiated PD-1int TCF+ cells have defects in generating TNFα. With transgenic ob/ob mice, we found that DFB produces cooperative efficacy with anti-PD-1 (αPD-1) by limiting the PD-1hi Tim3+ subset and amplifying the PD-1int TCF+ population. Finally, we defined the recombinant chemokine C-C-motif receptor 2 (CCR2)+ CD8+ subset as terminal Tex and identified that the differentiation from progenitor to terminal Tex is driven, at least in part, by the chemokine (C-C motif) ligand 2 (CCL2)/CCR2 axis. The CCR2 inhibitor enhances the response to αPD-1 by promoting the counts of progenitor Tex. Altogether, DFB dampens CCL2 and preserves progenitor Tex in the obese microenvironment to restrain CRC progression. These findings provide unambiguous evidence that the traditional Chinese formula DFB can prevent tumor progression by modulating adaptive immunity and establish a strong rationale for further clinical verification.