Chromosome 4p15.3 is frequently deleted in late-stage lung cancer. We investigated the significance of the SLIT2 gene located in this region to lung cancer progression. SLIT2 encodes an extracellular glycoprotein that can suppress breast cancer by regulating β-catenin. In this study, we examined alterations in the structure or expression of SLIT2, its receptor ROBO1, and β-catenin, along with the AKT/glycogen synthase kinase 3β (GSK3β)/β-transducin repeat-containing protein (βTrCP) pathway in lung cancer cell lines and patients. Low SLIT2 expression correlated with an upward trend of pathological stage and poorer survival in lung cancer patients. Importantly, SLIT2, βTrCP, and β-catenin expression levels predicted postoperative recurrence of lung cancer in patients. Stimulating SLIT2 expression by various methods increased the level of E-cadherin caused by attenuation of its transcriptional repressor SNAI1. Conversely, knocking down SLIT2 expression increased cell migration and reduced cell adhesion through coordinated deregulation of β-catenin and E-cadherin/SNAI1 in the AKT/GSK3β/βTrCP pathway. Our findings indicate that SLIT2 suppresses lung cancer progression, defining it as a novel "theranostic" factor with potential as a therapeutic target and prognostic predictor in lung cancer. Cancer Res; 70(2); 543-51. ©2010 AACR.

Conflict of interest:The authors have declared that no conflict of interest exists. Nonstandard abbreviations used: microsatellite instability (MSI); non-small cell lung cancer (NSCLC); loss of heterozygosity (LOH); squamous cell carcinoma (SQ); adenocarcinoma (AD); methylation-specific PCR (MSP); 5-aza-2′-deoxycytidine (5-aza-dC).

Purpose: Lung cancer cells frequently exhibit marked chromosome instability. We postulated that alterations of the double-strand break repair genes (BRCA1, BRCA2, and XRCC5) might be involved in lung cancer. Patients and Methods: We examined the loss of protein and mRNA expression and the 5 ¶CpG hypermethylation and allelic imbalance of the BRCA1, BRCA2, and XRCC5 genes in 98 non^small cell lung cancer (NSCLC) samples. Anchorage-dependent growth after reexpression of these genes was examined in a lung cancer cell line that originally lacked BRCA1and BRCA2 expression. Results: The data indicated that low protein expression of BRCA1 and BRCA2 was frequent in lung adenocarcinomas (42-44%), whereas low XRCC5 protein expression was more prevalent among squamous cell carcinoma (32%). In addition, low BRCA1 expression was significantly associated with low RB expression, especially in lung adenocarcinoma. Concurrent alterations in XRCC5 and p53 were the most frequent profiles in smoking patients. Importantly, low mRNA and protein expressions of BRCA1, BRCA2, and XRCC5 were significantly associated with their promoter hypermethylation. 5-Aza-2 ¶-deoxycytidine treatment of NSCLC cells showed demethylation and reexpression of the BRCA1 and BRCA2 genes and reduced anchorageindependent growth. Conclusions: Our retrospective study provides compelling evidence that low mRNA and protein expression in the BRCA1/BRCA2 and XRCC5 genes occur in lung adenocarcinoma and squamous cell carcinoma, respectively, and that promoter hypermethylation is the predominant mechanism in deregulation of these genes. Alteration of the double-strand break repair pathway, perhaps by interacting with p53 and RB deregulation, is important in the pathogenesis of a subset of NSCLC.Lung cancer is one of the most common malignancies, making it very important to identify the associated gene(s) involved. We previously did a genome-wide loss of heterozygosity (LOH) study in 71 primary surgically resected non -small cell lung cancer (NSCLC) tumors in which a high mean LOH frequency was reported, indicating the presence of chromosome instability in NSCLC (1). Chromosome instability may be caused by failure in the repair of DNA double-strand breaks (DSB; ref. 2). Interestingly, the chromosome regions at 2q33-35 and 13q12.3, which included gene loci encoding the XRCC5 (Ku80) and BRCA2 (breast cancer 2) DSB repair proteins, respectively, showed a high frequency of LOH in NSCLC tumors (1). We therefore postulated that alterations of genes in chromosomal stability control pathways, such as DSB repair genes (BRCA1, BRCA2, and XRCC5), may be involved in NSCLC tumorigenesis.Two distinct and complementary mechanisms, homologous recombination and nonhomologous end joining, are involved in the repair of detrimental DSBs in mammalian cells (2, 3). The breast tumor suppressors BRCA1 and BRCA2 have been shown to interact with DNA damage -induced Rad51 protein to form foci on DSBs (4, 5). Mouse Brca1-and Brca2-deficient embryonic stem cells show a reduced efficiency ...

No abstract

A HIC1-SIRT1-p53 circular loop in which hypermethylation in cancer 1 (HIC1) represses the transcription of SIRT1 that deacetylates and inactivates p53 thus leading to HIC1 inactivation has been identified in cell and animal models. However, the alteration and prognostic effects of HIC1-SIRT1-p53 circular loop have never been demonstrated in human cancer patients. We examine the HIC1-SIRT1-p53 alterations in 118 lung cancer patients to define their etiological roles in tumorigenesis. We found that patients with lung squamous cell carcinoma with low p53 acetylation and SIRT1 expression mostly showed low HIC1 expression, confirming deregulation of HIC1-SIRT1-p53 circular loop in the clinical model. Interestingly, the expression of deleted in breast cancer 1 (DBC1), which blocks the interaction between SIRT1 deacetylase and p53, led to acetylated p53 in patients with lung adenocarcinoma. However, epigenetic alteration of HIC1 promoter by posttranslational modifications of histones and promoter hypermethylation favoring the compacted chromatin production attenuated the transcriptional induction by acetylated p53. Importantly, lung cancer patients with altered HIC1-SIRT1-p53 circular regulation showed poor prognosis. Our data show the first valid clinical evidence of the deregulation of HIC1-SIRT1-p53 loop in lung tumorigenesis and prognosis. Distinct status of p53 acetylation/deacetylation and HIC1 alteration mechanism result from different SIRT1-DBC1 control and epigenetic alteration in lung squamous cell carcinoma and lung adenocarcinoma.