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The bone morphogenic proteins (BMPs) play a key role in skeletal development and patterning. Using the technique of differential display polymerase chain reaction (ddPCR), we have identified a novel gene whose expression is increased during BMP-2-induced differentiation of the prechondroblastic cell line, MLB13MYC clone 17, to an osteoblastic phenotype. The 6.5-kilobase mRNA recognized by this ddPCR product is increased 10-fold by BMP-2 treatment of the MLB13MYC clone 17 cells. The mRNA recognized by this ddPCR product is also increased as MC3T3-E1 cells recapitulate the program of osteoblast differentiation during prolonged culture. The full-length transcript corresponding to this ddPCR product was cloned from a MLB13MYC clone 17 cell cDNA library. Analysis of the deduced amino acid sequence demonstrated that this gene encodes a novel 126-kDa putative serine/threonine protein kinase containing a nuclear localization signal. The kinase domain, expressed in Escherichia coli, is capable of autophosphorylation as well as phosphorylation of myelin basic protein. The gene was, therefore, named BIKe (BMP-2-Inducible Kinase). The BIKe nuclear localization signal is able to direct green fluorescent protein to the nucleus in transfected COS-7 cells. When stably expressed in MC3T3-E1 cells, BIKe significantly decreases alkaline phosphatase activity and osteocalcin mRNA levels and retards mineral deposition relative to vector control. This novel kinase, therefore, is likely to play an important regulatory role in attenuating the program of osteoblast differentiation.Numerous investigations have been directed at elucidating factors that regulate osteoblast differentiation (1). The bone morphogenetic proteins (BMPs) 1 are potent local factors that promote osteoblast differentiation during development as well as during bone remodeling (2). The molecular events downstream of BMP signaling that result in tissue-specific gene expression and skeletal development have only been partially elucidated. The binding of BMPs to their receptors leads to the assembly of a receptor complex in which the type II receptor phosphorylates and activates the type I receptor. As a result, pathway-restricted SMADs are phosphorylated, leading to interactions with the common mediator SMAD, smad4 (3). This complex is then translocated to the nucleus, where it modulates transcription of target genes. BMP signaling can also interfere with the effects of other growth and differentiation factors. It has been demonstrated that BMP-2 treatment of mesangial cells prevents phosphorylation of a transcription factor, Elk1, in response to platelet-derived growth factor (PDGF) signaling. This effectively inhibits PDGF-induced Elk-1-mediated transcription, and blocks PDGF-induced transcription of c-fos, an Elk-1 target (4). BMP-7 has been shown to be a potent inducer of Cbfa1, a transcription factor belonging to the runt-domain gene family that, in turn, regulates the expression of several genes in the osteoblast (5). Although Cbfa1 expression is necessary, it a...

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 carcinoid (n = 7) tumor tissues were analyzed by immunohistochemical staining for EGFR, ErbB2, ErbB3, and ErbB4. Sequencing of tumor DNA of exons 18 to 21 of the 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 carcinoid 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 nucleotide 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 expresses EGFR, we found that erlotinib reduced proliferation by inhibiting EGFR signal transduction. Conclusions: Our findings suggest clinical potential for the use of EGFR inhibitors in the 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 malignant neoplasms comprising neuroendocrine cells that account 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). Pulmonary 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 tumors 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 smokers. Epidemiologic data show that pulmonary typical carcinoid 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 carcinoid 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...

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