Dysregulation in lipid metabolism is among the most prominent metabolic alterations in cancer. Cancer cells harness lipid metabolism to obtain energy, components for biological membranes, and signaling molecules needed for proliferation, survival, invasion, metastasis, and response to the tumor microenvironment impact and cancer therapy. Here, we summarize and discuss current knowledge about the advances made in understanding the regulation of lipid metabolism in cancer cells and introduce different approaches that have been clinically used to disrupt lipid metabolism in cancer therapy.

Autophagy is linked to cell death, yet the associated mechanisms are largely undercharacterized. We discovered that melanoma, which is generally resistant to drug-induced apoptosis, can undergo autophagic cell death with the participation of orphan nuclear receptor TR3. A sequence of molecular events leading to cellular demise is launched by a specific chemical compound, 1-(3,4,5-trihydroxyphenyl)nonan-1-one, newly acquired from screening a library of TR3-targeting compounds. The autophagic cascade comprises TR3 translocation to mitochondria through interaction with the mitochondrial outer membrane protein Nix, crossing into the mitochondrial inner membrane through Tom40 and Tom70 channel proteins, dissipation of mitochondrial membrane potential by the permeability transition pore complex ANT1-VDAC1 and induction of autophagy. This process leads to excessive mitochondria clearance and irreversible cell death. It implicates a new approach to melanoma therapy through activation of a mitochondrial signaling pathway that integrates a nuclear receptor with autophagy for cell death.

Highlights d HCC-cell-derived ectosomal PKM2 induces monocyte-tomacrophage differentiation d Remodeling tumor microenvironment by ectosomal PKM2 promotes HCC progression d Sumoylation facilitates PKM2 sorting into ectosomes in an ARRDC1-dependent manner d Macrophage-secreted CCL1 reinforces PKM2 ectosomal excretion in a feedforward loop

Gluconeogenesis, an essential metabolic process for hepatocytes, is downregulated in hepatocellular carcinoma (HCC). Here we show that the nuclear receptor Nur77 is a tumour suppressor for HCC that regulates gluconeogenesis. Low Nur77 expression in clinical HCC samples correlates with poor prognosis, and a Nur77 deficiency in mice promotes HCC development. Nur77 interacts with phosphoenolpyruvate carboxykinase (PEPCK1), the rate-limiting enzyme in gluconeogenesis, to increase gluconeogenesis and suppress glycolysis, resulting in ATP depletion and cell growth arrest. However, PEPCK1 becomes labile after sumoylation and is degraded via ubiquitination, which is augmented by the p300 acetylation of ubiquitin-conjugating enzyme 9 (Ubc9). Although Nur77 attenuates sumoylation and stabilizes PEPCK1 via impairing p300 activity and preventing the Ubc9-PEPCK1 interaction, Nur77 is silenced in HCC samples due to Snail-mediated DNA methylation of the Nur77 promoter. Our study reveals a unique mechanism to suppress HCC by switching from glycolysis to gluconeogenesis through Nur77 antagonism of PEPCK1 degradation.

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Apoptotic resistance is becoming a significant obstacle for cancer therapy as the majority of treatment takes the route of apoptotic induction. It is of great importance to develop an alternative strategy to induce cancer cell death. We previously reported that autophagic cell death mediated by nuclear receptor TR3 and driven by a chemical agonist, 1-(3,4,5-trihydroxyphenyl)nonan-1-one (THPN), is highly effective in the therapy of melanoma but not any other cancer types. Here, we discovered that the insensitivity of cancer cells to THPN originated from a high cellular Akt2 activity. Akt2 phosphorylation interferes with TR3 export to cytoplasm and targeting to mitochondria, which lead to the autophagic induction. Therefore, the TR3-mediated autophagy could be effectively induced in the otherwise insensitive cells by downregulating Akt2 activity. Highly effective antineoplastic compounds are developed through optimizing the structure of THPN. This study implicates a general strategy for cancer therapy by the induction of autophagic cell death.