METTL3 is frequently up-regulated in human HCC and contributes to HCC progression. METTL3 represses SOCS2 expression in HCC through an m6A-YTHDF2-dependent mechanism. Our findings suggest an important mechanism of epigenetic alteration in liver carcinogenesis. (Hepatology 2018;67:2254-2270).

Most cases of breast cancer mortality are due to vascular metastasis. Breast cancer cells must intravasate through endothelial cells (ECs) to enter a blood vessel in the primary tumor and then adhere to ECs and extravasate at the metastatic site. In this study we demonstrate that inhibition of hypoxia-inducible factor activity (HIF) in breast cancer cells by RNA interference or digoxin treatment inhibits primary tumor growth and also inhibits the metastasis of breast cancer cells to the lungs by blocking the expression of angiopoietin-like 4 (ANGPTL4) and L1 cell adhesion molecule (L1CAM). ANGPTL4 is a secreted factor that inhibits EC-EC interaction, whereas L1CAM increases the adherence of breast cancer cells to ECs. Interference with HIF, ANGPTL4, or L1CAM expression inhibits vascular metastasis of breast cancer cells to the lungs.

Primary tumors facilitate metastasis by directing bone marrowderived cells (BMDCs) to colonize the lungs before the arrival of cancer cells. Here, we demonstrate that hypoxia-inducible factor 1 (HIF-1) is a critical regulator of breast cancer metastatic niche formation through induction of multiple members of the lysyl oxidase (LOX) family, including LOX, LOX-like 2, and LOX-like 4, which catalyze collagen cross-linking in the lungs before BMDC recruitment. Only a subset of LOX family members was expressed in any individual breast cancer, but HIF-1 was required for expression in each case. Knockdown of HIF-1 or hypoxia-induced LOX family members reduced collagen cross-linking, CD11b+ BMDC recruitment, and metastasis formation in the lungs of mice after orthotopic transplantation of human breast cancer cells. Metastatic niche formation is an HIF-1-dependent event during breast cancer progression. extracellular matrix | lung metastasis I ntratumoral hypoxia is a common finding that is attributable to inadequate O 2 delivery to regions of rapidly growing cancers that are distant from functional blood vessels (1). Reduced O 2 availability leads to increased activity of hypoxia-inducible factors (HIFs), which consist of an O 2 -regulated HIF-1α or HIF-2α subunit and the constitutively expressed HIF-1β subunit (2, 3). HIF inhibition blocks tumor xenograft growth (2, 4).Metastasis is responsible for 90% of deaths among patients who have breast cancer and involves multiple steps, including cancer cell invasion through ECM, intravasation, extravasation, and colonization of distant organs (5). Recent studies have reported that prior recruitment of bone marrow-derived cells (BMDCs) to the metastatic site promotes subsequent colonization by cancer cells (6). The primary tumor is responsible for BMDC recruitment to the metastatic site. Breast tumors secrete lysyl oxidase (LOX), which localizes at metastatic sites in the lungs and remodels collagen, thereby facilitating BMDC recruitment (7,8). LOX oxidatively deaminates the ε-amino groups of lysine residues, resulting in intramolecular and intermolecular cross-linking of collagen molecules (9). Crosslinking stabilizes collagen by assembly into fibrils and fibers, which enhance ECM tensile strength, leading to focal adhesion formation and PI3K signaling (10). The LOX family is composed of LOX and LOX-like (LOXL) proteins LOXL1-4. So far, only LOX has been implicated in metastatic niche formation (7). In this study, we demonstrate that HIF-1 regulates metastatic niche formation by activating expression of LOX and LOXL proteins. HIF-1 silencing suppresses metastatic niche formation and metastasis regardless of which LOX family member is involved. ResultsHypoxia-Induced LOX/LOXL Expression in Breast Cancer Cell Lines.Two metastatic breast cancer cell lines, MDA-MB-231 (MDA-231) and MDA-MB-435 (MDA-435), as well as a nonmetastatic line, MCF-7, were cultured under standard, nonhypoxic tissue culture conditions of 95% air/5% CO 2 (vol/vol; 20% O 2 ) and under hypoxic culture conditi...

Metastasis is the leading cause of death among patients with breast cancer. Understanding the role of the extracellular matrix in the metastatic process may lead to the development of improved therapies for cancer patients. Intratumoral hypoxia is found in the majority of breast cancers and is associated with an increased risk of metastasis and patient mortality. Here we demonstrate that hypoxia-inducible factor 1 activates the transcription of genes encoding collagen prolyl hydroxylases that are critical for collagen deposition by breast cancer cells. We show that expression of collagen prolyl hydroxylases promotes cancer cell alignment along collagen fibers, resulting in enhanced invasion and metastasis to lymph nodes and lungs. Lastly, we establish the prognostic significance of collagen prolyl hydroxylase mRNA expression in human breast cancer biopsies, and demonstrate that ethyl 3,4-dihydroxybenzoate, a prolyl hydroxylase inhibitor, decreases tumor fibrosis and metastasis in a mouse model of breast cancer.

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Metastasis is the leading cause of death among patients who have breast cancer. Understanding the role of the extracellular matrix in the metastatic process may lead to the development of improved therapies to treat cancer patients. Intratumoral hypoxia, found in the majority of breast cancers, is associated with an increased risk of metastasis and mortality. We found that in hypoxic breast cancer cells, HIF-1 activates transcription of the PLOD1 and PLOD2 genes encoding procollagen lysyl hydroxylases that are required for the biogenesis of collagen, which is a major constituent of the extracellular matrix. High PLOD2 expression in breast cancer biopsies is associated with increased risk of mortality. We demonstrate that PLOD2 is critical for fibrillar collagen formation by breast cancer cells, increases tumor stiffness, and is required for metastasis to lymph nodes and lungs.

Poor prognosis of cancers, including hepatocellular carcinoma (HCC), is mainly associated with metastasis; however, the underlying mechanisms remain poorly understood. This article investigates the role of lysyl oxidase-like 2 (LOXL-2) in the biology of HCC metastasis. First, we showed that HCC metastasis relies on a collagen-modifying enzyme, LOXL2, which was significantly overexpressed in tumorous tissues and sera of HCC patients, indicating that LOXL2 may be a good diagnostic marker for HCC patients. Second, we delineated a complex, interlinked signaling network that involves multiple regulators, including hypoxia, transforming growth factor beta (TGF-b), and microRNAs (miRNAs), converging to control the expression of LOXL2. We found not only that LOXL2 was regulated by hypoxia/hypoxia-inducible factor 1 alpha (HIF-1a), but also that TGF-b activated LOXL2 transcription through mothers against decapentaplegic homolog 4 (Smad4), whereas two frequently underexpressed miRNA families, miR-26 and miR-29, cooperatively suppressed LOXL2 transcription through interacting with the 3' untranslated region of LOXL2. Third, we demonstrated the imperative roles of LOXL2 in modifying the extracellular matrix components in the tumor microenvironment and metastatic niche of HCC. LOXL2 promoted intrahepatic metastasis by increasing tissue stiffness, thereby enhancing the cytoskeletal reorganization of HCC cells. Furthermore, LOXL2 facilitated extrahepatic metastasis by enhancing recruitment of bone-marrow-derived cells to the metastatic site. Conclusion: These findings integrate the clinical relevance, molecular regulation, and functional implications of LOXL2 in HCC metastasis. (HEPATOLOGY 2014;60:1645-1658 H epatocellular carcinoma (HCC) is the most common form of primary liver cancer. HCC is the fifth-most prevalent cancer and ranked the second-most common lethal cancer.1 It claims more than 600,000 lives globally every year. 1 The high mortality rate in HCC is mainly attributable to metastasis for at least three reasons. First, it is a major cause of liver and organ failure. Second, patients diagnosed

Cancer cells experience an increase in oxidative stress. The pentose phosphate pathway (PPP) is a major biochemical pathway that generates antioxidant NADPH. Here, we show that transketolase (TKT), an enzyme in the PPP, is required for cancer growth because of its ability to affect the production of NAPDH to counteract oxidative stress. We show that TKT expression is tightly regulated by the Nuclear Factor, Erythroid 2-Like 2 (NRF2)/Kelch-Like ECHAssociated Protein 1 (KEAP1)/BTB and CNC Homolog 1 (BACH1) oxidative stress sensor pathway in cancers. Disturbing the redox homeostasis of cancer cells by genetic knockdown or pharmacologic inhibition of TKT sensitizes cancer cells to existing targeted therapy (Sorafenib). Our study strengthens the notion that antioxidants are beneficial to cancer growth and highlights the therapeutic benefits of targeting pathways that generate antioxidants.M etabolic reprogramming has recently been recognized as a hallmark of cancer (1). Cancer cells preferentially use glycolysis instead of oxidative phosphorylation to generate energy even in the presence of oxygen (O 2 ). This metabolic shift, named the Warburg Effect, channels glucose intermediates for macromolecule and antioxidant synthesis. A very important metabolic pathway that connects with glycolysis is the pentose phosphate pathway (PPP). The major goal of the PPP is the production of ribose-5-phosphate (R5P) and NADPH. R5P is the major backbone of RNA and is critical to nucleotide synthesis. NADPH is the major antioxidant that maintains the two major redox molecules, glutathione and thioredoxin, in the reduced state. NADPH therefore counteracts reactive oxygen species (ROS), enabling cancer cells to survive oxidative stress.The PPP is composed of the oxidative and nonoxidative arms. The oxidative arm of the PPP produces NADPH and ribose by three irreversible steps. First, glucose-6-phosphate dehydrogenase (G6PD) converts glucose-6-phosphate (G6P) to 6-phospho-gluconolactone and NAPDH. Second, phosphogluconolactonase converts 6-phospho-gluconolactone to 6-phosphogluconate. Third, 6-phosphogluconate dehydrogenase converts 6-phosphogluconate to ribulose-5-phosphate (Ru5P) and NAPDH. Ru5P then enters the nonoxidative arm of the PPP. Ru5P is converted to xylulose-5-phosphate (X5P) and Ru5P by epimerase and isomerase, respectively. The transketolase (TKT) family [transketolase-like 1 (TKTL1) and TKTL2] transfers two-carbon groups from X5P to R5P to generate sedoheptulose-7-phosphate (S7P) to glyceraldehyde-3-phosphate (G3P). Transaldolase (TALDO) transfers three-carbon groups from S7P to G3P to generate erythrose-4-phosphate (E4P) and fructose-6-phosphate (F6P). Finally, TKT transfers two-carbon groups from X5P to E4P to generate G3P and F6P, which reenter glycolysis. All enzymes in the nonoxidative arm of the PPP are reversible, allowing cells to adapt to the dynamic metabolic demands. When cells experience high oxidative stress, metabolites from the nonoxidative arm are rechanneled into glycolysis to refill the oxidative arm for...