Oncogenic ß-catenin stimulation of AKT2-CAD-mediated pyrimidine synthesis is targetable vulnerability in liver cancer.

CTNNB1, encoding ß-catenin protein, is the most frequently altered proto-oncogene in hepatic neoplasms. In this study, we studied the significance and pathological mechanism of CTNNB1 gain-of-function mutations in hepatocarcinogenesis. Activated ß-catenin not only triggered hepatic tumorigenesis but also exacerbated Tp53 deletion or hepatitis B virus infection-mediated liver cancer development in mouse models. Using untargeted metabolomic profiling, we identified boosted de novo pyrimidine synthesis as the major metabolic aberration in ß-catenin mutant cell lines and livers. Oncogenic ß-catenin transcriptionally stimulated AKT2, which then phosphorylated the rate-limiting de novo pyrimidine synthesis enzyme CAD (carbamoyl-phosphate synthetase 2, aspartate transcarbamoylase, dihydroorotase) on S1406 and S1859 to potentiate nucleotide synthesis. Moreover, inhibition of ß-catenin/AKT2-stimulated pyrimidine synthesis axis preferentially repressed ß-catenin mutant cell proliferation and tumor formation. Therefore, ß-catenin active mutations are oncogenic in various preclinical liver cancer models. Stimulation of ß-catenin/AKT2/CAD signaling cascade on pyrimidine synthesis is an essential and druggable vulnerability for ß-catenin mutant liver cancer.

ß-catenin-IRP2-primed iron availability to mitochondrial metabolism is druggable for active ß-catenin-mediated cancer.

BACKGROUND: Although ß-catenin signaling cascade is frequently altered in human cancers, targeting this pathway has not been approved for cancer treatment. METHODS: High-throughput screening of an FDA-approved drug library was conducted to identify therapeutics that selectively inhibited the cells with activated ß-catenin. Efficacy of iron chelator and mitochondrial inhibitor was evaluated for suppression of cell proliferation and tumorigenesis. Cellular chelatable iron levels were measured to gain insight into the potential vulnerability of ß-catenin-activated cells to iron deprivation. Extracellular flux analysis of mitochondrial function was conducted to evaluate the downstream events of iron deprivation. Chromatin immunoprecipitation, real-time quantitative PCR and immunoblotting were performed to identify ß-catenin targets. Depletion of iron-regulatory protein 2 (IRP2), a key regulator of cellular iron homeostasis, was carried out to elucidate its significance in ß-catenin-activated cells. Online databases were analyzed for correlation between ß-catenin activity and IRP2-TfR1 axis in human cancers. RESULTS: Iron chelators were identified as selective inhibitors against ß-catenin-activated cells. Deferoxamine mesylate, an iron chelator, preferentially repressed ß-catenin-activated cell proliferation and tumor formation in mice. Mechanically, ß-catenin stimulated the transcription of IRP2 to increase labile iron level. Depletion of IRP2-sequered iron impaired ß-catenin-invigorated mitochondrial function. Moreover, mitochondrial inhibitor S-Gboxin selectively reduced ß-catenin-associated cell viability and tumor formation. CONCLUSIONS: ß-catenin/IRP2/iron stimulation of mitochondrial energetics is targetable vulnerability of ß-catenin-potentiated cancer.

Oncogenic ß-catenin-driven liver cancer is susceptible to methotrexate-mediated disruption of nucleotide synthesis.

BACKGROUND: Liver cancer is largely resistant to chemotherapy. This study aimed to identify the effective chemotherapeutics for ß-catenin-activated liver cancer which is caused by gain-of-function mutation of catenin beta 1 ( CTNNB1 ), the most frequently altered proto-oncogene in hepatic neoplasms. METHODS: Constitutive ß-catenin-activated mouse embryonic fibroblasts (MEFs) were established by deleting exon 3 ( ß-catenin Δ(ex3)/+ ), the most common mutation site in CTNNB1 gene. A screening of 12 widely used chemotherapy drugs was conducted for the ones that selectively inhibited ß-catenin Δ(ex3)/+ but not for wild-type MEFs. Untargeted metabolomics was carried out to examine the alterations of metabolites in nucleotide synthesis. The efficacy and selectivity of methotrexate (MTX) on ß-catenin-activated human liver cancer cells were determined in vitro . Immuno-deficient nude mice subcutaneously inoculated with ß-catenin wild-type or mutant liver cancer cells and hepatitis B virus ( HBV ); ß-catenin lox(ex3)/+ mice were used, respectively, to evaluate the efficacy of MTX in the treatment of ß-catenin mutant liver cancer. RESULTS: MTX was identified and validated as a preferential agent against the proliferation and tumor formation of ß-catenin-activated cells. Boosted nucleotide synthesis was the major metabolic aberration in ß-catenin-active cells, and this alteration was also the target of MTX. Moreover, MTX abrogated hepatocarcinogenesis of HBV ; ß-catenin lox(ex3)/+ mice, which stimulated concurrent Ctnnb1- activated mutation and HBV infection in liver cancer. CONCLUSION: MTX is a promising chemotherapeutic agent for ß-catenin hyperactive liver cancer. Since repurposing MTX has the advantages of lower risk, shorter timelines, and less investment in drug discovery and development, a clinical trial is warranted to test its efficacy in the treatment of ß-catenin mutant liver cancer.

Overexpressed PKM2 promotes macrophage phagocytosis and atherosclerosis.

BACKGROUND: The expression of pyruvate kinase muscle 2 (PKM2) is augmented in macrophages of patients with atherosclerotic coronary artery disease. The role of PKM2 in atherosclerosis is to be determined. METHODS: Global and myeloid cell-specific PKM2 knock-in mice with ApoE-/- background (ApoE-/- , PKM2KI/KI and Lyz2-cre, ApoE-/- , and PKM2flox/flox ) were produced to evaluate the clinical significance of PKM2 in atherosclerosis development. Wild-type and PKM2 knock-in macrophages were isolated to assess the function of PKM2 in macrophage phagocytosis. Atherosclerotic mice were treated with PKM2 inhibitor shikonin (SKN) to evaluate the therapeutic potential of PKM2 suppression in atherosclerosis. RESULTS: Oxidized low-density lipoprotein (oxLDL) upregulated PKM2 in macrophages. PKM2 in return promoted the uptake of oxLDL by macrophages. Overexpressed PKM2 accelerated atherosclerosis in mice. SKN blocked the progress of mouse atherosclerosis. CONCLUSIONS: PKM2 accelerates macrophage phagocytosis and atherosclerosis. Targeting PKM2 is a potential therapy for atherosclerosis.