Hassan Lemjabbar-Alaoui

Sulf-2: an extracellular modulator of cell signaling and a cancer target candidate

Importance of the field: Sulf-1 and Sulf-2 are sulfatases that edit the sulfation status of heparan sulfate proteoglycans (HSPGs) on the outside of cells and regulate a number of critical signaling pathways. The Sulfs are dysregulated in many cancers with Sulf-2 in particular implicated as a driver of carcinogenesis in NSCLC, pancreatic cancer and hepatocellular carcinoma. Areas covered in this review: This review describes the novel activity of the Sulfs in altering the sulfation pattern of HSPG chains on the outside of cells. Thereby, the Sulfs can change the binding of growth factors to these chains and can either promote (e.g., Wnt) or inhibit (e.g., fibroblast growth factor-2) signaling. The review focuses on the widespread upregulation of both Sulfs in cancers and summarizes the evidence that Sulf-2 promotes the transformed behavior of several types of cancer cells in vitro as well as their tumorigenicity in vivo. What the reader will gain: Sulf-2 is a bonafide candidate as a cancer-causing agent in NSCLC and other cancers in which it is upregulated. Take home message: Sulf-2 is an extracellular enzyme and as such would be an attractive therapeutic target for the treatment of NSCLC and other cancers.

Sulf-2, a heparan sulfate endosulfatase, promotes human lung carcinogenesis

Heparan sulfate (HS) proteoglycans (HSPGs) bind to multiple growth factors/morphogens and regulate their signaling. 6-O-sulfation (6S) of glucosamine within HS chains is critical for many of these ligand interactions. Sulf-1 and Sulf-2, which are extracellular neutral-pH sulfatases, provide a novel post-synthetic mechanism for regulation of HSPG function by removing 6S from intact HS chains. The Sulfs can thereby modulate several signaling pathways, including the promotion of Wnt signaling. We found induction of SULF2 transcripts and Sulf-2 protein in human lung adenocarcinoma and squamous cell carcinoma, the two major classes of non-small-cell lung carcinomas (NSCLCs). We confirmed widespread Sulf-2 protein expression in tumor cells of 10/10 surgical specimens of human lung squamous carcinomas. We studied five Sulf-2+ NSCLC cell lines, including two, which were derived by cigarette-smoke transformation of bronchial epithelial cells. shRNA-mediated Sulf-2 knockdown in these lines caused an increase in 6S on their cell surface and in parallel reversed their transformed phenotype in vitro, eliminated autocrine Wnt signaling and strongly blunted xenograft tumor formation in nude mice. Conversely, forced Sulf-2 expression in non-malignant bronchial epithelial cells produced a partially transformed phenotype. Our findings support an essential role for Sulf-2 in lung cancer, the leading cancer killer.

Wnt and Hedgehog Are Critical Mediators of Cigarette Smoke-Induced Lung Cancer

Background Lung cancer is the leading cause of cancer death in the world, and greater than 90% of lung cancers are cigarette smoke-related. Current treatment options are inadequate, because the molecular basis of cigarette-induced lung cancer is poorly understood. Methodology/Principal Findings Here, we show that human primary or immortalized bronchial epithelial cells exposed to cigarette smoke for eight days in culture rapidly proliferate, show anchorage-independent growth, and form tumors in nude mice. Using this model of the early stages of smoke-induced tumorigenesis, we examined the molecular changes leading to lung cancer. We observed that the embryonic signaling pathways mediated by Hedgehog and Wnt are activated by smoke. Pharmacological inhibition of these pathways blocked the transformed phenotype. Conclusions/Significance These experiments provide a model in which the early stages of smoke-induced tumorigenesis can be elicited, and should permit us to identify molecular changes driving this process. Results obtained so far indicate that smoke-induced lung tumors are driven by activation of two embryonic regulatory pathways, Hedgehog (Hh) and Wnt. Based on the current and emerging availability of drugs to inhibit Hh and Wnt signaling, it is possible that an understanding of the role of Hh and Wnt in lung cancer pathogenesis will lead to the development of new therapies.

Lung cancer: Biology and treatment options

Lung cancer remains the leading cause of cancer mortality in men and women in the U.S. and worldwide. About 90% of lung cancer cases are caused by smoking and the use of tobacco products. However, other factors such as radon gas, asbestos, air pollution exposures, and chronic infections can contribute to lung carcinogenesis. In addition, multiple inherited and acquired mechanisms of susceptibility to lung cancer have been proposed. Lung cancer is divided into two broad histologic classes, which grow and spread differently: small-cell lung carcinomas (SCLCs) and non-small cell lung carcinomas (NSCLCs). Treatment options for lung cancer include surgery, radiation therapy, chemotherapy, and targeted therapy. Therapeutic-modalities recommendations depend on several factors, including the type and stage of cancer. Despite the improvements in diagnosis and therapy made during the past 25 years, the prognosis for patients with lung cancer is still unsatisfactory. The responses to current standard therapies are poor except for the most localized cancers. However, a better understanding of the biology pertinent to these challenging malignancies, might lead to the development of more efficacious and perhaps more specific drugs. The purpose of this review is to summarize the recent developments in lung cancer biology and its therapeutic strategies, and discuss the latest treatment advances including therapies currently under clinical investigation.

EMMPRIN regulates the canonical Wnt/β-catenin signaling pathway, a potential role in accelerating lung tumorigenesis

Advances in the field of tumor biology have identified that tumor cells co-opt developmental signaling pathways of embryonic stem cells and thus gain the ability to proliferate, differentiate and alter cell–cell interactions. One such pathway is the Wnt/β-catenin signaling pathway. High levels of EMMPRIN expression have been shown to correlate with poor prognosis and metastasis in a broad range of tumors. Although a variety of functions are attributed to EMMPRIN in tumorigenesis, the specific mechanism(s) through which it can exert its effects have not been elucidated, until now. In this study, we identify EMMPRIN as a novel regulator of the canonical Wnt/β-catenin signaling pathway in lung cancer. Increasing EMMPRIN expression levels in lung cancer epithelial cells upregulated the β-catenin signaling pathway and silencing EMMPRIN inhibited β-catenin signaling, cell migration, proliferation, anchorage-independent growth and tumor growth in a mouse tumor xenograft model. These results provide a compelling rationale for targeting EMMPRIN for anticancer therapies. Understanding the molecular mechanisms driving EMMPRIN-induced lung tumorigenesis will provide enormous benefits in developing new therapeutic treatments for this and other forms of cancer.

TACE/ADAM-17 phosphorylation by PKC-epsilon mediates premalignant changes in tobacco smoke-exposed lung cells.

Background Tobacco smoke predisposes humans and animals to develop lung tumors, but the molecular events responsible for this are poorly understood. We recently showed that signaling mechanisms triggered by smoke in lung cells could lead to the activation of a growth factor signaling pathway, thereby promoting hyperproliferation of lung epithelial cells. Hyperproliferation is considered a premalignant change in the lung, in that increased rates of DNA synthesis are associated with an increased number of DNA copying errors, events that are exacerbated in the presence of tobacco smoke carcinogens. Despite the existence of DNA repair mechanisms, a small percentage of these errors go unrepaired and can lead to tumorigenic mutations. The results of our previous study showed that an early event following smoke exposure was the generation of oxygen radicals through the activation of NADPH oxidase. Although it was clear that these radicals transduced signals through the epidermal growth factor receptor (EGFR), and that this was mediated by TACE-dependent cleavage of amphiregulin, it remained uncertain how oxygen radicals were able to activate TACE. Principal Findings In the present study, we demonstrate for the first time that phosphorylation of TACE at serine/threonine residues by tobacco smoke induces amphiregulin release and EGFR activation. TACE phosphorylation is triggered in smoke-exposed lung cells by the ROS-induced activation of PKC through the action of SRC kinase. Furthermore, we identified PKCε as the PKC isoform involved in smoke-induced TACE activation and hyperproliferation of lung cells. Conclusions Our data elucidate new signaling paradigms by which tobacco smoke promotes TACE activation and hyperproliferation of lung cells.

Glycosylation Alterations in Lung and Brain Cancer

Alterations in glycosylation are common in cancer and are thought to contribute to disease. Lung cancer and primary malignant brain cancer, most commonly glioblastoma, are genetically heterogeneous diseases with extremely poor prognoses. In this review, we summarize the data demonstrating that glycosylation is altered in lung and brain cancer. We then use specific examples to highlight the diverse roles of glycosylation in these two deadly diseases and illustrate shared mechanisms of oncogenesis. In addition to alterations in glycoconjugate biosynthesis, we also discuss mechanisms of postsynthetic glycan modification in cancer. We suggest that alterations in glycosylation in lung and brain cancer provide novel tumor biomarkers and therapeutic targets.

SULF2 expression by immunohistochemistry and overall survival in oesophageal cancer: a cohort study

Objectives Oesophageal cancer is the eighth most commonly diagnosed cancer worldwide, and there is a need for biomarkers to improve diagnosis, prognosis and treatment. Sulfatases 2 (SULF2) is an extracellular endosulphatase that regulates several signalling pathways in carcinogenesis and has been associated with poor prognosis. This study evaluates the relationship between SULF2 expression by immunohistochemistry and overall survival in patients with oesophageal cancer. Design Cohort study. Setting Single tertiary care centre. Participants We included patients who underwent esophagectomy for invasive oesophageal adenocarcinoma and squamous cell carcinoma at a tertiary care centre from 1997 to 2006. We excluded patients with recurrent oesophageal cancer or less than 3 mm invasive tumour on H&E stained slide. A section from each paraffin-embedded tissue specimen was stained with an anti-SULF2 monoclonal antibody. Outcome measures A pathologist blinded to overall survival determined the percentage and intensity of tumour cells staining. Vital status was obtained through the Social Security Death Master File, and overall survival was calculated from the date of surgery. Results One-hundred patients with invasive oesophageal cancer were identified, including 75 patients with adenocarcinoma and 25 patients with squamous cell carcinoma. The squamous cell carcinoma samples had a higher mean percentage and intensity of tumour cells staining compared with the adenocarcinoma samples. After adjusting for age, sex, race, histological type, stage and neoadjuvant therapy, for every 10% increase in percentage of tumour cells staining for SULF2, the HR for death increased by 13% (95% CI 1.01 to 1.25; p=0.03). Conclusions The majority of adenocarcinoma samples and all of the squamous cell carcinoma samples had SULF2 staining. The percentage of tumour cells staining for SULF2 was significantly associated with overall survival. Thus, SULF2 is a potential biomarker in oesophageal cancer and may have an important role in the management of patients with this disease.

Use of a phage display antibody to measure the enzymatic activity of the Sulfs.

Sulf-1 and Sulf-2 are extracellular endoglucosamine 6-sulfatases, which selectively liberate the 6-O-sulfate groups on glucosamines present in N, 6-O, and 2-O trisulfated disaccharides of intact heparan sulfate (HS)/heparin chains. The Sulfs are known to regulate signaling of heparin/HS-binding protein ligands, such as morphogens and growth factors, presumably through their ability to decrease the association between the ligands and HS proteoglycans. These enzymes serve important roles in development and are dysregulated in many cancers. We previously described arylsulfatase and endoglucosamine 6-sulfatase assays for the Sulfs. RB4CD12 is a phage display anti-HS antibody. N-sulfation, 2-O-sulfation, and 6-O-sulfation are involved in its binding. In this chapter, we describe the application of RB4CD12 in ELISA, flow cytometry, and immunohistochemistry assays to measure the enzymatic activity of the Sulfs. These newly established methods should facilitate further investigation of the Sulfs in vitro and in vivo.

Endosulfatases SULF1 and SULF2 limit Chlamydia muridarum infection.

The first step in attachment of Chlamydia to host cells is thought to involve reversible binding to host heparan sulfate proteoglycans (HSPGs), polymers of variably sulfated repeating disaccharide units coupled to diverse protein backbones. However, the key determinants of HSPG structure that are involved in Chlamydia binding are incompletely defined. A previous genome‐wide Drosophila RNAi screen suggested that the level of HSPG 6‐O sulfation rather than the identity of the proteoglycan backbone maybe a critical determinant for binding. Here, we tested in mammalian cells whether SULF1 or SULF2, human endosulfatases, which remove 6‐O sulfates from HSPGs, modulate Chlamydia infection. Ectopic expression of SULF1 or SULF2 in HeLa cells, which decreases cell surface HSPG sulfation, diminished C. muridarum binding and decreased vacuole formation. ShRNA depletion of endogenous SULF2 in a cell line that primarily expresses SULF2 augmented binding and increased vacuole formation. C. muridarum infection of diverse cell lines resulted indownregulation of SULF2 mRNA. In a murine model of acute pneumonia, mice genetically deficient in both endosulfatases or in SULF2 alone demonstrated increased susceptibility to C. muridarum lung infection. Collectively, these studies demonstrate that the level of HSPG 6‐O sulfation is a critical determinant of C. muridarum infection in vivo and that 6‐O endosulfatases are previously unappreciated modulators of microbial pathogenesis.