An integrated functional genomics and metabolomics approach for defining poor prognosis in human neuroendocrine cancers

Abstract

Human neuroendocrine (NE) cancers range from relatively indolent to highly aggressive. In this study, we combine functional genomics with metabolomics to identify features of NE cancers associated with a poor outcome. Analysis of GeneChip datasets of primary prostate tumors, as well as lymph node and liver metastases from transgenic mice with a NE cell cancer, plus derived NE cell lines yielded a signature of 446 genes whose expression is enriched in neoplastic mouse prostatic NE cells. This signature was used for in silico metabolic reconstructions of NE cell metabolism, directed liquid chromatography͞tandem MS analysis of metabolites in prostatic NE tumors and cell lines, and analysis of GeneChip datasets of human NE tumors with good or poor prognoses. The results indicate that a distinguishing feature of poor-prognosis NE tumors is a glutamic acid decarboxylase-independent pathway for production of GABA and a pathway for production of imidazole-4-acetate that involves dopa decarboxylase and a membraneassociated amine oxidase, amiloride-binding protein 1. Electrophysiological studies disclosed that imidazole-4-acetate can bind and activate GABAA receptors expressed by transformed NE cells, thus providing a previously uncharacterized paradigm for NE tumor cell signaling. Transcriptional, metabolic, and electrophysiologic features of transformed mouse NE cells are also evident in neural progenitor cells.GABA signaling ͉ MS ͉ metastatic neuroendocrine cancers ͉ polyamine metabolism ͉ transcriptome-directed metabolomics H uman neuroendocrine (NE) cancers (NECs) can arise in neuroectodermal tissues or in endoderm-derived epithelia (e.g., pheochromocytomas and small cell lung cancers, respectively). Many types of NECs are aggressive and diagnosed only after metastatic spread (1, 2). In addition, the appearance of NE features in cancers arising from cells that do not normally express neural or endocrine fates is often associated with more aggressive disease (3-5). A panel of biomarkers and mediators of tumorigenesis is needed for better diagnosis and stratification of NECs and new, more efficacious therapeutic approaches. In this report, we present one approach for addressing this issue that uses a combination of transgenic mice with a metastatic cancer arising from their prostatic NE cell lineage, NE cell lines established from this cancer, human NE tumors with varying degrees of aggressiveness, functional genomics, and MS-based metabolomics.The prostate contains three epithelial lineages: secretory, basal, and NE (6). The secretory or luminal cell is the most abundant type and requires continuous exposure to androgens for its survival (7-11). Basal cells represent the primary proliferating epithelial population and are not androgen-dependent (12, 13). NE cells are rare (Ͻ1% of the total), have distinctive projections that allow them to contact epithelial neighbors located several cell diameters away, and secrete a variety of neuropeptides and neurotransmitters (14-17). Conventional adenocarcinoma of the prostate (C...

Linkage between cellular communications, energy utilization, and proliferation in metastatic neuroendocrine cancers

“…1A), validating our previous LC͞MS studies (8). In addition to GABA, 1,2-propanediol (propylene glycol) was identified as another abundant metabolite (Fig.…”

“…The results indicated that a distinguishing feature of poor prognosis NE tumors is a glutamic acid decarboxylase 1 (Gad1)-independent pathway for synthesis of GABA that uses the diamine oxidase, amiloride-binding protein 1 (Abp1). Follow-up GC-MS and LC-MS analyses and electrophysiological studies disclosed that PNEC cells synthesized GABA and expressed functional GABA A receptors on their surface (8). These findings suggested a previously uncharacterized mechanism for cellular signaling in the NE cancer microenvironment.…”

“…Adenocarcinomas originating in non-NE cell lineages in the lung, prostate, stomach, and colon, as well as other organs, can express NE cell-associated gene products. This ''neuroendocrine differentiation'' (NED) correlates with poor prognosis (3)(4)(5)(6)(7)(8), although the underlying mechanisms remain obscure.…”

“…Previously, we combined GeneChip data sets obtained from CR2-TAg prostates and metastases plus PNEC cells to obtain a ''core'' NE transcript profile (8). This profile was used to generate an in silico reconstruction of the NE cell metabolome, and compared with GeneChip data sets from good and poor prognosis human NE tumors.…”

Quantitative expression analysis and prognostic significance of L-DOPA decarboxylase in colorectal adenocarcinoma

“…It is worth mentioning that DDC is regarded as a general biomarker for neuroendocrine tumours (Gazdar et al, 1988;Gilbert et al, 1995;Ippolito et al, 2005). High DDC mRNA expression has been noticed in small-cell lung carcinoma (SCLC), neuroblastoma, and pheochromocytoma (Jensen et al, 1990;Gilbert et al, 1999;Uccella et al, 2006).…”