Human Cancer Biology Analysis of ErbB Receptors in Pulmonary Carcinoid Tumors Otis B. Rickman, 1 Pawan K. Vohra, 1 Bharati Sanyal, 1 Julie A. Vrana, 2 Marie-Christine Aubry, 2 Dennis A. Wigle, 3 and Charles F. Thomas, Jr. 1 Abstract Purpose: This study aimed to investigate the expression of the ErbB family of receptor tyrosine kinases in pulmonary typical carcinoid and atypical carcinoid tumors and to understand the role of epidermal growth factor receptor (EGFR) signaling in pulmonary carcinoid tumor proliferation. Experimental Design: Surgically resected typical carcinoid (n = 24) and atypical carci- noid (n = 7) tumor tissues were analyzed by immunohistochemical staining for EGFR, ErbB2,ErbB3,andErbB4.SequencingoftumorDNAofexons18to21ofthe EGFR gene and the KRAS gene was carried out. Biochemical analysis of lung carcinoid cell lines was used to investigate EGFR signal transduction and response to erlotinib inhibition. Results: The analysis showed that 45.8% of typical carcinoid and 28.6% of atypical car- cinoid tumors express EGFR, 100% of the tumors lack expression of ErbB2, and 100% have moderate to intense staining for ErbB3 and ErbB4. Sequencing of tumor DNA of exons 18 to 21 of the EGFR gene revealed the absence of tyrosine kinase domain mutations in these tumors. Instead, 80.6% tumors harbored a synonymous single nu- cleotide polymorphism in exon 20. Because EGFR and KRAS mutations tend not to be present at the same time, we sequenced the KRAS gene from pulmonary carcinoid tumor DNA and found that 100% were wild-type. Using a lung carcinoid cell line that expressesEGFR,wefoundthaterlotinibreducedproliferationbyinhibitingEGFRsignal transduction. Conclusions: OurfindingssuggestclinicalpotentialfortheuseofEGFRinhibitorsinthe treatment of patients with pulmonary carcinoid tumors, particularly for patients with EGFR-positive pulmonary carcinoid tumors not amenable to surgical resection. Lung cancer is the leading cause of cancer-related death in the United States (1). Pulmonary carcinoid tumors are ma- lignant neoplasms comprising neuroendocrine cells that ac- count for 2% to 5% of all lung cancers (2). Pulmonary typical carcinoid, which is considered a low-grade tumor, has scarce mitotic figures (<2 per 10 high-powered fields) and absence of necrosis in histologic specimens (3). Pulmo- nary atypical carcinoid, a higher-grade tumor, has 2 to 10 mitotic figures per 10 high-powered fields, and/or areas of focal necrosis (3). Typical carcinoid tumors usually present at an average age of 45 years, whereas atypical carcinoid tu- mors present a decade later. Pulmonary carcinoid tumors can develop without any known risk factors for lung cancer, and in particular less than half of patients are cigarette smo- kers. Epidemiologic data show that pulmonary typical carci- noid tumors are about four times more frequent than atypical carcinoid tumors, and that women are at higher risk than men of developing these tumors. The 5-year survival for pulmonary typical carcinoid tumors averages 88% and ranges from 25% to 56% for atypical car- cinoid tumors (4–6). Surgical resection of the tumor in the affected lung is the standard treatment, but complete surgical excision can be difficult or unattainable depending upon the location of the tumor in the chest and whether it has metas- tasized. Chemotherapy and radiation therapy have limited success in treating pulmonary carcinoid tumors (7–9). Widely metastatic pulmonary carcinoid tumors can result in carci- noid heart disease or the carcinoid syndrome (10). At the time of diagnosis, up to 30% of patients will have the car- cinoid syndrome with symptoms due to excessive production of serotonin from the tumor burden (11). The outcome for patients with widely metastatic disease is poor. A better un- derstanding of the biology of these tumors could lead to the development of novel therapeutic agents to improve patient outcomes. Altered growth factor signaling through cell surface recep- tors is thought to contribute to tumorigenesis through abnor- mal cell proliferation. The ErbB family of receptor tyrosine kinases consists of the epidermal growth factor receptor Authors' Affiliations: 1 Thoracic Diseases Research Unit, Division of Pulmonary, Critical Care and Internal Medicine, Department of Medicine, Departments of 2 Laboratory Medicine and Pathology, and 3 Surgery, Mayo Clinic College of Medicine, Rochester, Minnesota Received 10/2/08; revised 2/6/09; accepted 2/9/09; published online 5/15/09. Grant support: Mayo Foundation. Thecostsofpublicationofthisarticleweredefrayedinpartbythepaymentof page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Requests for reprints: Charles F. Thomas Jr., Thoracic Diseases Research Unit, 826 Stabile Building, Mayo Clinic College of Medicine, Rochester, MN 55905. Phone: 507-284-2494; Fax: 507-284-4521; E-mail: thomas.charles@ mayo.edu. F 2009 American Association for Cancer Research. doi:10.1158/1078-0432.CCR-08-2549 3315 Clin Cancer Res 2009;15(10) May 15, 2009 www.aacrjournals.org Downloaded from http://aacrjournals.org/clincancerres/article-pdf/15/10/3315/1981905/3315.pdf by guest on 14 June 2022