Single Nucleotide Polymorphisms in VTI1A Gene Contribute to the Susceptibility of Chinese Population to Non-Small Cell Lung cancer

The Role of Vti1a in Biological Functions and Its Possible Role in Nervous System Disorders

Vesicle transport through interaction with t-SNAREs 1A (Vti1a), a member of the N-ethylmaleimide-sensitive factor attachment protein receptor protein family, is involved in cell signaling as a vesicular protein and mediates vesicle trafficking. Vti1a appears to have specific roles in neurons, primarily by regulating upstream neurosecretory events that mediate exocytotic proteins and the availability of secretory organelles, as well as regulating spontaneous synaptic transmission and postsynaptic efficacy to control neurosecretion. Vti1a also has essential roles in neural development, autophagy, and unconventional extracellular transport of neurons. Studies have shown that Vti1a dysfunction plays critical roles in pathological mechanisms of Hepatic encephalopathy by influencing spontaneous neurotransmission. It also may have an unknown role in amyotrophic lateral sclerosis. A VTI1A variant is associated with the risk of glioma, and the fusion product of the VTI1A gene and the adjacent TCF7L2 gene is involved in glioma development. This review summarizes Vti1a functions in neurons and highlights the role of Vti1a in the several nervous system disorders.

Cancer-driving mutations and variants of components of the membrane trafficking core machinery

The core machinery for vesicular membrane trafficking broadly comprises of coat proteins, RABs, tethering complexes and SNAREs. As cellular membrane traffic modulates key processes of mitogenic signaling, cell migration, cell death and autophagy, its dysregulation could potentially results in increased cell proliferation and survival, or enhanced migration and invasion. Changes in the levels of some components of the core machinery of vesicular membrane trafficking, likely due to gene amplifications and/or alterations in epigenetic factors (such as DNA methylation and micro RNA) have been extensively associated with human cancers. Here, we provide an overview of association of membrane trafficking with cancer, with a focus on mutations and variants of coat proteins, RABs, tethering complex components and SNAREs that have been uncovered in human cancer cells/tissues. The major cellular and molecular cancer-driving or suppression mechanisms associated with these components of the core membrane trafficking machinery shall be discussed.

Vesicle transport through interaction with t-SNAREs 1a (Vti1a)'s roles in neurons

The Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) family mediates membrane fusion during membrane trafficking and autophagy in all eukaryotic cells, with a number of SNAREs having cell type-specific functions. The endosome-trans-Golgi network (TGN) localized SNARE, Vesicle transport through interaction with t-SNAREs 1A (Vti1a), is unique among SNAREs in that it has numerous neuron-specific functions. These include neurite outgrowth, nervous system development, spontaneous neurotransmission, synaptic vesicle and dense core vesicle secretion, as well as a process of unconventional surface transport of the Kv4 potassium channel. Furthermore, the human VT11A gene is known to form fusion products with neighboring genes in cancer tissues, and VT11A variants are associated with risk in cancers, including glioma. In this review, I highlight VTI1A's known physio-pathological roles in brain neurons, as well as unanswered questions in these regards.

Tobacco smoking and methylation of genes related to lung cancer development

Lung cancer is a leading cause of cancer-related mortality worldwide, and cigarette smoking is the major environmental hazard for its development. This study intended to examine whether smoking could alter methylation of genes at lung cancer risk loci identified by genome-wide association studies (GWASs). By systematic literature review, we selected 75 genomic candidate regions based on 120 single-nucleotide polymorphisms (SNPs). DNA methylation levels of 2854 corresponding cytosine-phosphate-guanine (CpG) candidates in whole blood samples were measured by the Illumina Infinium Human Methylation450 Beadchip array in two independent subsamples of the ESTHER study. After correction for multiple testing, we successfully confirmed associations with smoking for one previously identified CpG site within the KLF6 gene and identified 12 novel sites located in 7 genes: STK32A, TERT, MSH5, ACTA2, GATA3, VTI1A and CHRNA5 (FDR <0.05). Current smoking was linked to a 0.74% to 2.4% decrease of DNA methylation compared to never smoking in 11 loci, and all but one showed significant associations (FDR <0.05) with life-time cumulative smoking (pack-years). In conclusion, our study demonstrates the impact of tobacco smoking on DNA methylation of lung cancer related genes, which may indicate that lung cancer susceptibility genes might be regulated by methylation changes in response to smoking. Nevertheless, this mechanism warrants further exploration in future epigenetic and biomarker studies.

Cumulative evidence for relationships between multiple variants in the VTI1A and TCF7L2 genes and cancer incidence

Genetic studies have linked the VTI1A-TCF7L2 region with risk of multiple cancers. However, findings from these studies were generally inconclusive. We aimed to provide a synopsis of current understanding of associations between variants in the VTI1A-TCF7L2 region and cancer susceptibility. We conducted a comprehensive research synopsis and meta-analysis to evaluate associations between 17 variants in this region and risk of seven cancers using data from 32 eligible articles totaling 224,656 cancer cases and 324,845 controls. We graded cumulative evidence of significant associations using Venice criteria and false-positive report probability tests. We also conducted analyses to evaluate potential function of these variants using data from the Encyclopedia of DNA Elements (ENCODE) Project. Eight variants showed a nominally significant association with risk of individual cancer (p < 0.05). Cumulative epidemiological evidence of an association was graded as strong for rs7903146 [odds ratio (OR) = 1.05, p = 4.13 × 10^-5 ] and rs7904519 (OR = 1.07, p = 2.02 × 10^-14 ) in breast cancer, rs11196172 (OR = 1.11, p = 2.22 × 10^-16 ), rs12241008 (OR = 1.13, p = 1.36 × 10^-10 ) and rs10506868 (OR = 1.10, p = 3.98 × 10^-9 ) in colorectal cancer, rs7086803 in lung cancer (OR = 1.30, p = 3.54 × 10^-18 ) and rs11196067 (OR = 1.18, p = 3.59 × 10^-13 ) in glioma, moderate for rs12255372 (OR = 1.12, p = 2.52 × 10^-4 ) in breast cancer and weak for rs7903146 (OR = 1.11, p = 0.007) in colorectal cancer. Data from ENCODE suggested that seven variants with strong evidence and other correlated variants might fall within putative functional regions. Collectively, our study provides summary evidence that common variants in the VTI1A and TCF7L2 genes are associated with risk of breast, colorectal, lung cancer and glioma and highlights the significant role of the VTI1A-TCF7L2 region in the pathogenesis of human cancers.

SNARE proteins in membrane trafficking

SNAREs are the core machinery mediating membrane fusion. In this review, we provide an update on the recent progress on SNAREs regulating membrane fusion events, especially the more detailed fusion processes dissected by well-developed biophysical methods and in vitro single molecule analysis approaches. We also briefly summarize the relevant research from Chinese laboratories and highlight the significant contributions on our understanding of SNARE-mediated membrane trafficking from scientists in China.

Adiponectin down-regulates CREB and inhibits proliferation of A549 lung cancer cells

INTRODUCTION

Adipokines are known to play a relevant role in a number of cancer related molecular pathways. Adiponectin is a major adipokine with anti-inflammatory and beneficial metabolic actions. Furthermore, it has been shown to exert anti-carcinogenic effects in various tumor models and some clinical studies suggested an inverse relationship between circulating levels of adiponectin and an increased risk for development of malignancies. On the other hand, the cyclic AMP response element binding (CREB) transcription factor has been clearly linked to lung cancer.

METHODS

we analyzed cell proliferation, cell cycle of A549 cells treated with adiponectin as well as CREB activation status in human lung adenocarcinoma A549 cells and in non-small cell lung cancer (NSCLC) samples.

RESULTS

adiponectin treatment, at concentrations ranging between 5 and 50 μg/ml mimicking human serum levels, has a significant effect on reducing tumor cell proliferation of A549 cells, mainly by altering cell cycle progression. Importantly, we provide evidence that adiponectin clearly inhibits in a dose- and time-dependent manner CREB phosphorylation (activation) and, at least in part, also the level of CREB protein itself, preceding and accompanying the anti-proliferative effects in response to adiponectin. Moreover, in agreement with previous studies demonstrating that CREB over-expression occurs in many tumors, we also show by western-blotting from lung specimen that CREB is significantly up-regulated in NSCLC samples compared to adjacent normal tissues from six patients.

CONCLUSIONS

Overall, our results represent the first evidence of CREB inhibition by adiponectin and may provide new insight into therapeutic strategies for lung cancer.