CA : A Cancer Journal for Clinicians

Lipids and cancer: Emerging roles in pathogenesis, diagnosis and therapeutic intervention

Tumor genetics guides patient selection for many new therapies, and cell culture studies have demonstrated that specific mutations can promote metabolic phenotypes. However, whether tissue context defines cancer dependence on specific metabolic pathways is unknown. Kras activation and Trp53 deletion in the pancreas or the lung result in pancreatic ductal adenocarinoma (PDAC) or non–small cell lung carcinoma (NSCLC), respectively, but despite the same initiating events, these tumors use branched-chain amino acids (BCAAs) differently. NSCLC tumors incorporate free BCAAs into tissue protein and use BCAAs as a nitrogen source, whereas PDAC tumors have decreased BCAA uptake. These differences are reflected in expression levels of BCAA catabolic enzymes in both mice and humans. Loss of Bcat1 and Bcat2, the enzymes responsible for BCAA use, impairs NSCLC tumor formation, but these enzymes are not required for PDAC tumor formation, arguing that tissue of origin is an important determinant of how cancers satisfy their metabolic requirements.

Tissue of origin dictates branched-chain amino acid metabolism in mutant Kras-driven cancers

A classification is a hierarchy of objects that conforms to the following principles: 1. The classes (groups with members) of the hierarchy have a set of properties or rules that extend to every member of the class and to all of the subclasses of the class, to the exclusion of all other [unrelated] classes. A subclass is itself a type of class wherein the members have the defining class properties of the parent class plus some additional property(ies) specific for the subclass.

What is a Classification

A transmembrane protein (TMEM) is a type of protein that spans biological membranes. Many of them extend through the lipid bilayer of the plasma membrane but others are located to the membrane of organelles. The TMEM family gathers proteins of mostly unknown functions. Many studies showed that TMEM expression can be down- or up-regulated in tumor tissues compared to adjacent healthy tissues. Indeed, some TMEMs such as TMEM48 or TMEM97 are defined as potential prognostic biomarkers for lung cancer. Furthermore, experimental evidence suggests that TMEM proteins can be described as tumor suppressors or oncogenes. TMEMs, such as TMEM45A and TMEM205, have also been implicated in tumor progression and invasion but also in chemoresistance. Thus, a better characterization of these proteins could help to better understand their implication in cancer and to allow the development of improved therapy strategies in the future. This review gives an overview of the implication of TMEM proteins in cancer.

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TMEM Proteins in Cancer: A Review.

Lung cancer (LC) is a leading cause of cancer-related deaths worldwide. Its rapid growth requires hyperactive catabolism of principal metabolic fuels. It is unclear whether fructose, an abundant sugar in current diets, is essential for LC. We demonstrated that, under the condition of coexistence of metabolic fuels in the body, fructose was readily used by LC cells in vivo as a glucose alternative via upregulating GLUT5, a major fructose transporter encoded by solute carrier family 2 member 5 (SLC2A5). Metabolomic profiling coupled with isotope tracing demonstrated that incorporated fructose was catabolized to fuel fatty acid synthesis and palmitoleic acid generation in particular to expedite LC growth in vivo. Both in vitro and in vivo supplement of palmitoleic acid could restore impaired LC propagation caused by SLC2A5 deletion. Furthermore, molecular mechanism investigation revealed that GLUT5-mediated fructose utilization was required to suppress AMPK and consequently activate mTORC1 activity to promote LC growth. As such, pharmacological blockade of in vivo fructose utilization using a GLUT5 inhibitor remarkably curtailed LC growth. Together, this study underscores the importance of in vivo fructose utilization mediated by GLUT5 in governing LC growth and highlights a promising strategy to treat LC by targeting GLUT5 to eliminate those fructose-addicted neoplastic cells.

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GLUT5-mediated fructose utilization drives lung cancer growth by stimulating fatty acid synthesis and AMPK/mTORC1 signaling

Accumulating studies suggest that circular RNAs (circRNAs) function as key regulators in human cancers. We found that hsa_circ_0001869 participated in non-small cell lung cancer (NSCLC) progression. However, its expression and function during NSCLC remain unknown. The data advised that hsa_circ_0001869 expression was increased in NSCLC cell lines and tissues. High hsa_circ_0001869 expression had negatively correlation with the NSCLC patients prognosis. Bioinformatics and luciferase report analyses confirmed that miR-638 and FOSL2 were hsa_circ_0001869 downstream target. hsa_circ_0001869 downregulation decreased tumor proliferation, invasion and migration by promoting miR-638 expression and decreasing FOSL2 expression. As a result of overexpression of FOSL2 or silencing of miR-638, the recovery of proliferation, migration, and invasion after hsa_circ_0001869 silencing. Overexpression of FOSL2 also led to recovery of migration, invasion and proliferation after upregulation of miR-638. In vivo studies confirmed that overexpression of FOSL2 or silencing of miR-638 led to the recovery of tumor growth ability regarding A549 cells after hsa_circ_0001869 knockdown. Present investigation discovered that hsa_circ_0001869 enhanced NSCLC progression via sponging miR-638 and promoting FOSL2 expression. hsa_circ_0001869 downregulation suppressed tumor growth and invasion ability.

Hsa_circ_0001869 promotes NSCLC progression via sponging miR-638 and enhancing FOSL2 expression.

Background Non-small cell lung cancer (NSCLC) accounts for a significant proportion of cancer-related deaths and lacks an effective treatment strategy. NSCLC tissues are generally found in a low oxygen environment. The NDUFA4L2 protein, located in the mitochondria, is encoded by the nucleus genome and is considered a crucial mediator that regulates cell survival. A better understanding of the mechanism of NDUFA4L2 in NSCLC survival in hypoxic environments is essential to design new therapeutic methods. Methods Twenty NSCLC and corresponding paired non-tumorous lung tissue samples were collected. NSCLC cell lines were cultured in hypoxic conditions to investigate the mechanism of NDUFA4L2 in NSCLC. The role of NDUFA4L2 was confirmed by using Western blotting, reactive oxygen species measurement, flow cytometry, immunofluorescence analysis, and wound healing and colony formation assays. Results The expression of HIF-1α and mitochondrial NDUFA4L2 increased in NSCLC cell lines cultured in hypoxic conditions (1% O2 ). NDUFA4L2 was drastically overexpressed in human NSCLC tissues and cell lines cultured in hypoxic conditions. HIF-1α regulated the expression of NDUFA4L2. Knockdown of NDUFA4L2 notably increased mitochondrial reactive oxygen species production, which suppressed the viability of NSCLC. Conclusion In conclusion, overexpression of NDUFA4L2 is a key factor for maintaining NSCLC growth, suggesting that mitochondrial NDUFA4L2 may be a potential target for the treatment of lung cancer.

Mitochondrial NDUFA4L2 protein promotes the vitality of lung cancer cells by repressing oxidative stress.

Activated cdc42-associated tyrosine kinase 1 (ACK1) has been reported to be implicated in non-small-cell lung cancer (NSCLC). However, the expression pattern and biological functions of ACK1 in the progression of NSCLC are not fully understood. In this study, it was found that the expression of ACK1 was significantly up-regulated in NSCLC samples compared to their adjacent normal tissues. Meanwhile, the expression of ACK1 was inversely correlated with the survival of NSCLC patients. Moreover, in the biological function studies, ACK1 was further validated to promote the growth, migration, and metastasis of NSCLC cells in vitro and in vivo. Mechanistically, ACK1 bind with FGFR1 and was essential for the phosphorylation of AKT induced by FGF. Our study demonstrated that ACK1 played an oncogenic role in the progression of NSCLC and ACK1 might be a promising target for the treatment of NSCLC. © 2015 Wiley Periodicals, Inc.

Activated cdc42-associated kinase is up-regulated in non-small-cell lung cancer and necessary for FGFR-mediated AKT activation.

Transmembrane protein 45B (TMEM45B) is a member of TMEMs. Altered expression of TMEMs is frequently observed in a variety of human cancers, but the expression and functional roles of TMEM45B in lung cancer is not reported. In the present study, levels of mRNA expression of TMEM45B in lung cancer tissues were assessed using re-analyzing expression data of The Cancer Genome Atlas (TCGA) lung cancer cohort and real-time PCR analysis on our own cohort. Lung cancer cells, A549 and NCI-H1975, infected with TMEM45B short hairpin RNA were examined in cell proliferation, cell cycle, cell apoptosis, wound-healing, and cell invasion assays as well as mouse xenograft models. Here, we demonstrated that TMEM45B was overexpressed in lung cancer and its expression correlated with overall survival of patients. In addition, silencing of TMEM45B expression reduced cell proliferation in vitro and in vivo, induced cell cycle arrest and cell apoptosis, and blocked cell migration and invasion. Moreover, knockdown of TMEM45B significantly suppressed G1/S transition, induced cell apoptosis, and inhibited cell invasion via regulating the expression of cell cycle-related proteins (CDK2, CDC25A, and PCNA), cell apoptosis-related proteins (Bcl2, Bax, and Cleaved Caspase 3), and metastasis-related proteins (MMP-9, Twist, and Snail), respectively. Thus, TMEM45B is a potential prognostic marker and cancer-selective therapeutic target in lung cancer.

Xiao Xie

Papers

GLUT5-mediated fructose utilization drives lung cancer growth by stimulating fatty acid synthesis and AMPK/mTORC1 signaling

Hsa_circ_0001869 promotes NSCLC progression via sponging miR-638 and enhancing FOSL2 expression.

Mitochondrial NDUFA4L2 protein promotes the vitality of lung cancer cells by repressing oxidative stress.

Activated cdc42-associated kinase is up-regulated in non-small-cell lung cancer and necessary for FGFR-mediated AKT activation.

TMEM45B, up-regulated in human lung cancer, enhances tumorigenicity of lung cancer cells