Jinliang Xing

Mitochondrial DNA Content: Its Genetic Heritability and Association With Renal Cell Carcinoma

BACKGROUND The extent to which mitochondrial DNA (mtDNA) content (also termed mtDNA copy number) in normal human cells is influenced by genetic factors has yet to be established. In addition, whether inherited variation of mtDNA content in normal cells contributes to cancer susceptibility remains unclear. Renal cell carcinoma accounts for 85% of all renal cancers. No studies have investigated the association between mtDNA content and the risk of renal cell carcinoma. METHODS We first used a classic twin study design to estimate the genetic contribution to the determination of mtDNA content. mtDNA content was measured by quantitative real-time polymerase chain reaction in peripheral blood lymphocytes from 250 monozygotic twins, 92 dizygotic twins, and 33 siblings (ie, individual siblings of a pair of twins). We used biometric genetic modeling to estimate heritability of mtDNA content. We then used a case-control study with 260 case patients with renal cell carcinoma and 281 matched control subjects and multivariable logistic regression analysis to examine the association between mtDNA content in peripheral blood lymphocytes and the risk of renal cell carcinoma. All statistical tests were two-sided. RESULTS The heritability (ie, proportion of phenotypic variation in a population that is attributable to genetic variation among individuals) of mtDNA content was 65% (95% confidence interval [CI] = 50% to 72%; P < .001). Case patients with renal cell carcinoma had a statistically significantly lower mtDNA content (1.18 copies) than control subjects (1.29 copies) (difference = 0.11, 95% CI = 0.03 to 0.17; P = .006). Low mtDNA content (ie, less than the median in control subjects) was associated with a statistically significantly increased risk of renal cell carcinoma, compared with high content (odds ratio = 1.53, 95% CI = 1.07 to 2.19). In a trend analysis, a statistically significant dose-response relationship was detected between lower mtDNA content and increasing risk of renal cell carcinoma (P for trend <.001). CONCLUSIONS mtDNA content appears to have high heritability. Low mtDNA content appears to be associated with increased risk of renal cell carcinoma.

HAb18G/CD147 Functions in Invasion and Metastasis of Hepatocellular Carcinoma

CD147 molecule is reported to be correlated with the malignancy of some cancers; however, it remains unclear whether it is involved in the progression of hepatocellular carcinoma (HCC). Here, we investigated the function of HAb18G/CD147, a member of CD147 family, and its antibodies, HAb18 and LICARTIN, in HCC invasion and metastasis. We observed that HAb18G/CD147 gene silence in HCC cells significantly decreased the secretion of matrix metalloproteinase (MMP) and the invasive potential of HCC cells (P < 0.001). MMP silence in HCC cells also significantly suppressed the invasion of the cells when cocultured with fibroblasts; however, its inhibitory effect was significantly weaker than that of both HAb18G/CD147 silence in HCC cells and that of MMP silence in fibroblasts (P < 0.001). Blocking theHAb18G/CD147 molecule on HCC cells with HAb18 monoclonal antibody resulted in a similar suppressive effect on MMP secretion and cell invasion, but with no significant effects on the cell growth. 131I-labeled HAb18 F(ab′)2 (LICARTIN), however, significantly inhibited the in vitro growth of HCC cells (P < 0.001). In an orthotopic model of HCC in nude mice, HAb18 and LICARTIN treatment effectively reduced the tumor growth and metastasis as well as the expression of three major factors in the HCC microenviroment (MMPs, vascular endothelial growth factor, and fibroblast surface protein) in the paracancer tissues. Overall, these results suggest that HAb18G/CD147 plays an important role in HCC invasion and metastasis mainly via modulating fibroblasts, as well as HCC cells themselves to disrupt the HCC microenviroment. LICARTIN can be used as a drug targeting to HAb18G/CD147 in antimetastasis and recurrence therapy of HCC. (Mol Cancer Res 2007;5(6):605–14)

MicroRNA expression signatures in Barrett's esophagus and esophageal adenocarcinoma

Purpose: Esophageal adenocarcinoma is a highly aggressive malignancy that frequently develops from Barretts esophagus, a premalignant pathologic change occurring in the lower end of the esophagus. Identifying Barretts esophagus patients at high risk of malignant transformation is essential to the prevention of esophageal adenocarcinoma. Although microRNA (miRNA) expression signatures have been associated with the etiology and prognosis of several types of cancers, their roles in the development of esophageal adenocarcinoma have not been extensively evaluated. Experimental Design: In this study, we analyzed the expression patterns of 470 human miRNAs using Agilent miRNA microarray in 32 disease/normal-paired tissues from 16 patients diagnosed with Barretts esophagus of either low- or high-grade dysplasia, or esophageal adenocarcinoma. Results: Using unsupervised hierarchical clustering and class comparison analyses, we found that miRNA expression profiles in tissues of Barretts esophagus with high-grade dysplasia were significantly different from their corresponding normal tissues. Similar findings were observed for esophageal adenocarcinoma, but not for Barretts esophagus with low-grade dysplasia. The expression patterns of selected miRNAs were further validated using quantitative reverse transcription real-time PCR in an independent set of 75 pairs of disease/normal tissues. Finally, we identified several miRNAs that were involved in the progressions from low grade-dysplasia Barretts esophagus to esophageal adenocarcinoma. Conclusions: We showed that miRNAs were involved in the development and progression of esophageal adenocarcinoma. The identified significant miRNAs that may become potential targets for early detection, chemoprevention, and treatment of esophageal cancer. (Clin Cancer Res 2009;15(18):5744–52)

Transcription factor Sp1 regulates expression of cancer-associated molecule CD147 in human lung cancer

CD147 is a novel cancer‐associated biomarker that plays an important role in the invasion and metastasis of human lung cancer. In spite of its many known functions, little is known about CD147 transcriptional regulation. In this study, we explored the regulation of CD147 in human lung cancer tissues. Over 60% of the human lung cancer tissues expressed differential high levels of CD147. We then cloned the 5′‐flanking region of the human CD147 gene and identified a critical promoter region at −108 to –42 which contained one binding site for Sp1, which was essential in up‐regulating CD147 promoter activity. These results were proven by blocking Sp1 using RNAi or mithramycin A treatment and up‐regulating Sp1 using transfection with eukaryotic expression vector. Consistent with the CD147 transcription activation, a high level of Sp1 expression was detected in lung cancer cell lines overexpressing CD147. Chromatin immunoprecipitation assay showed that much more Sp1 could bind to the CD147 promoter in 95‐D with CD147 high expression than in SK‐MES‐1 with CD147 low expression. There was a significant positive correlation between CD147 expression and Sp1 expression level detected by immunohistochemistry (r = 0.831). Collectively, our results suggest that Sp1 is essential for regulating the CD147 gene expression in human lung cancer. (Cancer Sci 2010)

Constitutive Short Telomere Length of Chromosome 17p and 12q but not 11q and 2p Is Associated with an Increased Risk for Esophageal Cancer

Shortened telomere length may cause chromosomal instability in Barretts esophagus and thus promote tumorigenesis. However, whether short telomere length in all chromosomes or just some of them is associated with increased esophageal cancer (EC) risk is largely unknown. To address this question, we examined the overall and chromosome-specific telomere lengths of 17p, 12q, 2p, and 11q and assessed their associations with EC risk. In a case-control study with 94 EC cases and 94 matched controls, the overall telomere length and the chromosome-specific telomere lengths of 17p, 12q, 2p, and 11q in peripheral blood lymphocytes were determined by a real-time PCR and a modified single telomere length analysis assay, respectively. Multivariate logistic regression analysis was used to assess the association between telomere length and EC risk. Compared with controls, EC patients had significantly shorter overall telomere lengths (P = 0.004) and chromosome-specific telomere lengths of 17p (P = 0.003) and 12q (P = 0.006) but not of 11q (P = 0.632) and 2p (P = 0.972). Furthermore, the multivariate logistic regression analysis showed that the short overall telomere length and chromosome-specific telomere lengths of 17p and 12q were associated with a dose-dependent increase in EC risk. Our study provides the first epidemiologic evidence that short telomere length of 17p and 12q plays an important role in esophageal carcinogenesis, suggesting that short telomere length of specific chromosomes is associated with the etiology of different cancer types.

RNA-Seq Analyses Generate Comprehensive Transcriptomic Landscape and Reveal Complex Transcript Patterns in Hepatocellular Carcinoma

RNA-seq is a powerful tool for comprehensive characterization of whole transcriptome at both gene and exon levels and with a unique ability of identifying novel splicing variants. To date, RNA-seq analysis of HBV-related hepatocellular carcinoma (HCC) has not been reported. In this study, we performed transcriptome analyses for 10 matched pairs of cancer and non-cancerous tissues from HCC patients on Solexa/Illumina GAII platform. On average, about 21.6 million sequencing reads and 10.6 million aligned reads were obtained for samples sequenced on each lane, which was able to identify >50% of all the annotated genes for each sample. Furthermore, we identified 1,378 significantly differently expressed genes (DEGs) and 24, 338 differentially expressed exons (DEEs). Comprehensive function analyses indicated that cell growth-related, metabolism-related and immune-related pathways were most significantly enriched by DEGs, pointing to a complex mechanism for HCC carcinogenesis. Positional gene enrichment analysis showed that DEGs were most significantly enriched at chromosome 8q21.3–24.3. The most interesting findings were from the analysis at exon levels where we characterized three major patterns of expression changes between gene and exon levels, implying a much complex landscape of transcript-specific differential expressions in HCC. Finally, we identified a novel highly up-regulated exon-exon junction in ATAD2 gene in HCC tissues. Overall, to our best knowledge, our study represents the most comprehensive characterization of HBV-related HCC transcriptome including exon level expression changes and novel splicing variants, which illustrated the power of RNA-seq and provided important clues for understanding the molecular mechanisms of HCC pathogenesis at system-wide levels.

Genetic Polymorphisms in Pre-microRNA Genes as Prognostic Markers of Colorectal Cancer

Background: Cumulative data have shown that microRNAs (miRNA) are involved in the etiology and prognosis of colorectal cancer (CRC). Genetic polymorphisms in pre-miRNA genes may influence the biogenesis and functions of their host miRNAs. However, whether these polymorphisms are associated with CRC prognosis remains unknown. Methods: We analyzed the effects of seven single-nucleotide polymorphisms (SNP) in pre-miRNA genes on the prognosis of a Chinese population with 408 CRC patients with surgically-resected adenocarcinoma. Results: Two SNPs were identified to be significantly associated with recurrence-free survival and overall survival of the patients. The most significant SNP was rs6505162 in pre-miR-423. Compared with the homozygous wild-type genotype, the variant-containing genotypes of this SNP were significantly associated with both the overall survival (HR = 2.12, 95% CI = 1.34–3.34, P = 0.001) and the recurrence-free survival (HR = 1.59, 95% CI = 1.08–2.36, P = 0.019). Another SNP, rs4919510 in pre-miR-608, was also associated with altered recurrence-free survival (HR = 0.61, 95% CI = 0.41–0.92, P = 0.017). These effects were evident only in patients receiving chemotherapy but not in those without chemotherapy. In addition, the combined analysis of the two SNPs conferred a 2.84-fold (95% CI = 1.50–5.37, P = 0.001) increased risk of recurrence and/or death. Similarly, this effect was only prominent in those receiving chemotherapy (P < 0.001) but not in those without chemotherapy (P = 0.999). Conclusions: Our data suggest that genetic polymorphisms in pre-miRNA genes may impact CRC prognosis especially in patients receiving chemotherapy, a finding that warrants further independent validation. Impact: This is one of the first studies showing a prognostic role of pre-miRNA gene SNPs in CRC. Cancer Epidemiol Biomarkers Prev; 21(1); 217–27. ©2011 AACR.

Function of HAb18G/CD147 in Invasion of Host Cells by Severe Acute Respiratory Syndrome Coronavirus

Abstract To identify the function of HAb18G/CD147 in invasion of host cells by severe acute respiratory syndrome (SARS) coronavirus (CoV), we analyzed the protein-protein interaction among HAb18G/CD147, cyclophilin A (CyPA), and SARS-CoV structural proteins by coimmunoprecipitation and surface plasmon resonance analysis. Although none of the SARS-CoV proteins was found to be directly bound to HAb18G/CD147, the nucleocapsid (N) protein of SARS-CoV was bound to CyPA, which interacted with HAb18G/CD147. Further research showed that HAb18G/CD147, a transmembrane molecule, was highly expressed on 293 cells and that CyPA was integrated with SARS-CoV. HAb18G/CD147–antagonistic peptide (AP)–9, an AP of HAb18G/CD147, had a high rate of binding to 293 cells and an inhibitory effect on SARS-CoV. These results show that HAb18G/CD147, mediated by CyPA bound to SARS-CoV N protein, plays a functional role in facilitating invasion of host cells by SARS-CoV. Our findings provide some evidence for the cytologic mechanism of invasion by SARS-CoV and provide a molecular basis for screening anti-SARS drugs

Association between mitochondrial DNA content in leukocytes and colorectal cancer risk: a case-control analysis.

Compelling epidemiological evidence indicated that alterations of mitochondrial DNA (mtDNA), including mutations and abnormal content of mtDNA, were implicated in the tumorigenesis of several malignancies in a tumor‐specific manner, such as lung cancer, breast cancer, and non‐Hodgkin lymphoma. This study was undertaken to investigate whether mtDNA content in peripheral blood lymphocytes (PBLs) could be used as a risk predictor for colorectal cancer (CRC).

Hypoxia upregulates CD147 through a combined effect of HIF-1α and Sp1 to promote glycolysis and tumor progression in epithelial solid tumors

Hypoxia is one of the most pervasive physiological stresses within tumors. Hypoxia signaling contributes to the aggressive tumor behaviors through promoting tumor cells to undergo the fundamental metabolism adaptation. A series of evidence indicates that this process is mainly mediated by hypoxia-inducible factor (HIF). However, key molecules involved in tumor hypoxia adaptation remain to be characterized. In this study, we investigated the functional role of CD147, a transmembrane glycoprotein highly overexpressed on the surface of tumor cells, in hypoxic microenvironment using in vitro and in vivo assays. Immunohistochemical staining showed that CD147 expression was upregulated in hypoxic region of epithelial solid tumor tissues. In addition, our data indicated that hypoxia induced the upregulation of CD147 expression at both mRNA and protein levels in epithelial carcinoma cells in a time- and dose-dependent manner. Moreover, we demonstrated that hypoxia-induced CD147 upregulation was mainly mediated by a combined effect of transcription factors HIF-1 and specificity protein 1 (Sp1) on the activation of CD147 promoter. We also explored the metabolic functions of hypoxia-induced CD147 and found that upregulated CD147 promoted glycolysis in both tumor cell lines and nude mice tumor xenograft model, partially through the functional cooperation with MCT-1 and MCT-4. Finally, we observed that CD147 promoted tumor growth, inhibited tumor cell apoptosis and enhanced their invasion ability under hypoxia. In conclusion, our findings reveal a novel mechanism of hypoxia adaptation mediated by CD147 in epithelial solid tumors and suggest that CD147 may be a promising therapeutic target in cancer treatment.