Malignant pleural mesothelioma (MPM) is a highly aggressive neoplasm arising from the mesothelial cells lining the parietal pleura and it exhibits poor prognosis. Although there has been significant progress in MPM treatment, development of more efficient therapeutic approaches is needed. BMAL1 is a core component of the circadian clock machinery and its constitutive overexpression in MPM has been reported. Here, we demonstrate that BMAL1 may serve as a molecular target for MPM. The majority of MPM cell lines and a subset of MPM clinical specimens expressed higher levels of BMAL1 compared to a nontumorigenic mesothelial cell line (MeT-5A) and normal parietal pleural specimens, respectively. A serum shock induced a rhythmical BMAL1 expression change in MeT-5A but not in ACC-MESO-1, suggesting that the circadian rhythm pathway is deregulated in MPM cells. BMAL1 knockdown suppressed proliferation and anchorage-dependent and independent clonal growth in two MPM cell lines (ACC-MESO-1 and H290) but not in MeT-5A. Notably, BMAL1 depletion resulted in cell cycle disruption with a substantial increase in apoptotic and polyploidy cell population in association with downregulation of Wee1, cyclin B and p21WAF1/CIP1 and upregulation of cyclin E expression. BMAL1 knockdown induced mitotic catastrophe as denoted by disruption of cell cycle regulators and induction of drastic morphological changes including micronucleation and multiple nuclei in ACC-MESO-1 cells that expressed the highest level of BMAL1. Taken together, these findings indicate that BMAL1 has a critical role in MPM and could serve as an attractive therapeutic target for MPM.
apoptosis; BMAL1; mesothelioma; targeted therapy; mitotic catastrophe
As with other epithelial cancers, lung cancer develops over a period of several years or decades via a series of progressive morphological changes accompanied by molecular alterations that commence in histologically normal epithelium. However the development of lung cancer presents certain unique features that complicates this evaluation. Anatomically the respiratory tree may be divided into central and peripheral compartments having different gross and histological anatomies as well as different functions. In addition, there are three major forms of lung cancer and many minor forms. Many of these forms arise predominantly in either the central or peripheral compartments. Squamous cell and small cell carcinomas predominantly arise in the central compartment, while adenocarcinomas predominantly arise peripherally. Large cell carcinomas are not a single entity but consist of poorly differentiated forms of the other types and, possibly, some truly undifferentiated “stem cell like” tumors. The multistage origin of squamous cell carcinomas, because of their central location, can be followed more closely than the peripherally arising adenocarcinomas. Squamous cell carcinomas arise after a series of reactive, metaplastic, premalignant and preinvasive changes. However, long term observations indicate that not all tumors follow a defined histologic course, and the clinical course, especially of early lesions, is difficult to predict. Peripheral adenocarcinomas are believed to arise from precursor lesions known as atypical adenomatous hyperplasias and may have extensive in situ growth before becoming invasive. Small cell carcinomas are believed to arise from severely molecularly damaged epithelium without going through recognizable preneoplastic changes. The molecular changes that occur prior to the onset on invasive cancers are extensive. As documented in this chapter, they encompass all of the six classic Hallmarks of Cancer other than invasion and metastasis, which by definition occur beyond preneoplasia. A study of preinvasive lung cancer has yielded much valuable biologic information that impacts on clinical management.
Lung cancer; squamous cell carcinoma; adenocarcinomas; small cell lung carcinoma; preneoplasia; carcinoma in situ; atypical adenomatous hyperplasia; tumor suppressor genes; oncogenes; apoptosis; telomerase; angiogenesis
To investigate the frequency of xenotropic murine leukemia virus (MLV) presence in human cell lines established from mouse xenografts and to search for the evidence of horizontal viral spread to other cell lines.
Six of 23 (26%) mouse DNA free xenograft cultures were strongly positive for MLV and their sequences had greater than 99% homology to known MLV strains. Four of five available supernatant fluids from these viral positive cultures were strongly positive for RT activity. Three of these supernatant fluids were studied to confirm the infectivity of the released virions for other human culture cells. Of the 78 non-xenograft derived cell lines maintained in the xenograft culture-containing facilities, 13 (17%) were positive for MLV, including XMRV, a virus strain first identified in human tissues. By contrast, all 50 cultures maintained in a xenograft culture-free facility were negative for viral sequences.
We examined xenograft tumor cell lines from seven independent laboratories and 128 non-xenografted tumor cell lines. Cell line DNA was examined for mouse DNA contamination, and by 3 Taqman qPCR assays targeting the gag, env or pol regions of MLV. Sequencing was used for viral strain identification. Supernatant fluids were tested for reverse transcriptase (RT) activity.
Human cultures derived after mouse xenografting frequently contain and release highly infectious xenotropic MLV viruses. Laboratories working with xenograft-derived human cultures should be aware of the risk of contamination with potentially biohazardous human-tropic mouse viruses and their horizontal spread to other cultures.
xenograft cultures; xenotropic murine leukemia virus; retrovirus; XMRV virus; cell cultures; lung cancer; prostate cell line
Lung cancer cell lines have made a substantial contribution to lung cancer translational research and biomedical discovery. A systematic approach to initiating and characterizing cell lines from small cell and non–small cell lung carcinomas has led to the current collection of more than 200 lung cancer cell lines, a number that exceeds those for other common epithelial cancers combined. The ready availability and widespread dissemination of the lines to investigators worldwide have resulted in more than 9000 citations, including multiple examples of important biomedical discoveries. The high (but not perfect) genomic similarities between lung cancer cell lines and the lung tumor type from which they were derived provide evidence of the relevance of their use. However, major problems including misidentification or cell line contamination remain. Ongoing studies and new approaches are expected to reveal the full potential of the lung cancer cell line panel.
We investigated the frequency and function of mutations and increased copy number of the PIK3CA gene in lung cancers. PIK3CA mutations are one of the most common gene changes present in human cancers. We analyzed the mutational status of exons 9 and 20 and gene copy number of PIK3CA using 86 non–small cell lung cancer (NSCLC) cell lines, 43 small cell lung cancer (SCLC) cell lines, 3 extrapulmonary small cell cancer (ExPuSC) cell lines, and 691 resected NSCLC tumors and studied the relationship between PIK3CA alterations and mutational status of epidermal growth factor receptor (EGFR) signaling pathway genes (EGFR, KRAS, HER2, and BRAF). We also determined PIK3CA expression and activity and correlated the findings with effects on cell growth. We identified mutations in 4.7% of NSCLC cell lines and 1.6% of tumors of all major histologic types. Mutations in cell lines of small cell origin were limited to two ExPuSC cell lines. PIK3CA copy number gains were more frequent in squamous cell carcinoma (33.1%) than in adenocarcinoma (6.2%) or SCLC lines (4.7%). Mutational status of PIK3CA was not mutually exclusive to EGFR or KRAS. PIK3CA alterations were associated with increased phosphatidylinositol 3-kinase activity and phosphorylated Akt expression. RNA interference–mediated knockdown of PIK3CA inhibited colony formation of cell lines with PIK3CA mutations or gains but was not effective in PIK3CA wild-type cells. PIK3CA mutations or gains are present in a subset of lung cancers and are of functional importance.
Gazdar and Minna discuss the context and implications of a research article that examines the transformation potential and response to inhibitors of specific
EGFR mutations found in lung cancer.
To identify a panel of tumor associated autoantibodies which can potentially be used as biomarkers for the early diagnosis of non-small cell lung cancer (NSCLC). Thirty-five unique and in-frame expressed phage proteins were isolated. Based on the gene expression profiling, four proteins were selected for further study. Both receiver operating characteristic curve analysis and leave-one-out method revealed that combined measurements of four antibodies produced have better predictive accuracies than any single marker alone. Leave-one-out validation also showed significant relevance with all stages of NSCLC patients. The panel of autoantibodies has a high potential for detecting early stage NSCLC.
NSCLC; Tumor-associated autoantibodies; SEREX; Early diagnosis
Acquired resistance to EGF receptor (EGFR) tyrosine kinase inhibitor (TKI) is a critical problem in the treatment of lung cancer. Although several mechanisms have been shown to be responsible for acquired resistance, all mechanisms have not been uncovered. In this study, we investigated the molecular and cellular profiles of the acquired resistant cells to EGFR-TKI in EGFR-mutant lung cancers. Four EGFR-mutant cell lines were exposed to gefitinib by stepwise escalation and high-concentration exposure methods, and resistant sublines to gefitinib were established. The molecular profiles and cellular phenotypes of these resistant sublines were characterized. Although previously reported, alterations including secondary EGFR T790M mutation, MET amplification, and appearance of epithelial-to-mesenchymal transition (EMT) features were observed, these 2 drug-exposure methods revealed different resistance mechanisms. The resistant cells with EMT features exhibited downregulation of miRNA-200c by DNA methylation. Furthermore, the HCC827-derived subline characterized by the high-concentration exposure method exhibited not only EMT features but also stem cell–like properties, including aldehyde dehydrogenase isoform 1 (ALDH1A1) overexpression, increase of side-population, and self-renewal capability. Resistant sublines with stem cell–like properties were resistant to conventional chemotherapeutic agents but equally sensitive to histone deacetylase and proteasome inhibitors, compared with their parental cells. ALDH1A1 was upregulated in clinical samples with acquired resistance to gefitinib. In conclusion, our study indicates that the manner of EGFR-TKI exposure influences the mechanism of acquired resistance and the appearance of stem cell–like property with EGFR-TKI treatment.
Tumor-derived cell lines play an important role in the investigation of tumor biology and genetics. Across a wide array of studies, they have been tools of choice for the discovery of important genes involved in cancer and for the analysis of the cellular pathways that are impaired by diverse oncogenic events. They are also invaluable for screening novel anticancer drugs. The TP53 protein is a major component of multiple pathways that regulate cellular response to various types of stress. Therefore, TP53 status affects the phenotype of tumor cell lines profoundly and must be carefully ascertained for any experimental project. In the present review, we use the 2014 release of the UMD TP53 database to show that TP53 status is still controversial for numerous cell lines, including some widely used lines from the NCI-60 panel. Our analysis clearly confirms that, despite numerous warnings, the misidentification of cell lines is still present as a silent and neglected issue, and that extreme care must be taken when determining the status of p53, because errors may lead to disastrous experimental interpretations. A novel compendium gathering the TP53 status of 2,500 cell lines has been made available (http://p53.fr). A stand-alone application can be used to browse the database and extract pertinent information on cell lines and associated TP53 mutations. It will be updated regularly to minimize any scientific issues associated with the use of misidentified cell lines (http://p53.fr).
TP53; cancer cell line; cross-contamination; misidentification; recommendation
We describe here the existence of a heregulin-HER3 autocrine loop, and the contribution of heregulin-dependent, HER2-mediated HER3 activation to gefitinib insensitivity in non-small cell lung cancer (NSCLC). ADAM17 protein, a major ErbB ligand sheddase, is upregulated in NSCLC and is required not only for heregulin-dependent HER3 signaling, but also for EGFR ligand-dependent signaling in NSCLC cell lines. A selective ADAM inhibitor, INCB3619, prevents the processing and activation of multiple ErbB ligands, including heregulin. In addition, INCB3619 inhibits gefitinib-resistant HER3 signaling and enhances gefitinib inhibition of EGFR signaling in NSCLC. These results show that ADAM inhibition affects multiple ErbB pathways in NSCLC and thus offers an excellent opportunity for pharmacological intervention, either alone or in combination with other drugs.
p53 is commonly mutated in lung adenocarcinoma. Mutant p53 loses wild-type function and some missense mutations further acquire oncogenic functions, while p53 wild-type may also induce pro-survival signaling. Therefore identification of signatures based on p53 mutational status has relevance to our understanding of p53 signaling pathways in cancer and identification of new therapeutic targets. To this end, we compared proteomic profiles of three cellular compartments (whole cell extract (WCE), cell surface, and media) from 28 human lung adenocarcinoma cell lines that differ based on p53 mutational status. In total, 11,598, 11,569, and 9,090 protein forms were identified in WCE, cell surface, and media, respectively. Bioinformatic analysis revealed that representative pathways associated with epithelial adhesion, immune and stromal cells, and mitochondrial function were highly significant in p53 missense mutations, p53 loss and wild-type p53 cell lines, respectively. Of note, mRNA levels of PGC1-α, a transcription co-activator that promotes mitochondrial oxidative phosphorylation and mitochondrial biogenesis, was substantially higher in p53 wild-type cell lines compared to either cell lines with p53 loss or with missense mutation. siRNA targeting PGC1-α inhibited cell proliferation in p53 wild-type cell lines, indicative of PGC1-α and its downstream molecules as potential therapeutic targets in p53 wild-type lung adenocarcinoma.
lung adenocarcinoma; p53; PGC-1α; proteomics; transcriptomics
Cancer/testis (CT) antigens are potential immunotherapeutic targets in cancer. However, the expression of particular antigens is limited to a subset of tumors of a given type. Thus, there is a need to identify antigens with complementary expression patterns for effective therapeutic intervention. In this study, we searched for genes that were distinctly expressed at a higher level in lung tumor tissue and the testes compared to other non-tumor tissues and identified members of the VCX/Y gene family as novel CT antigens. VCX3A, a member of the VCX/Y gene family, was expressed at the protein level in approximately 20% of lung adenocarcinomas and 35% of squamous cell carcinomas, but not expressed in normal lung tissues. Among CT antigens with concordant mRNA and protein expression levels, four CT antigens, XAGE1, VCX, IL13RA2, and SYCE1, were expressed, alone or in combination, in about 80% of lung adenocarcinoma tumors. The CT antigen VCX/Y gene family broadens the spectrum of CT antigens expressed in lung adenocarcinomas for clinical applications.
Cancer/testis antigen; VCX/Y; lung cancer; immunotherapy
The recently identified RASSF1 locus is located within a 120-kilobase region of chromosome 3p21.3 that frequently undergoes allele loss in lung and breast cancers. We explored the hypothesis that RASSF1 encodes a tumor suppressor gene for lung and breast cancers.
We assessed expression of two RASSF1 gene products, RASSF1A and RASSF1C, and the methylation status of their respective promoters in 27 non-small-cell lung cancer (NSCLC) cell lines, in 107 resected NSCLCs, in 47 small-cell lung cancer (SCLC) cell lines, in 22 breast cancer cell lines, in 39 resected breast cancers, in 104 nonmalignant lung samples, and in three breast and lung epithelial cultures. We also transfected a lung cancer cell line that lacks RASSF1A expression with vectors containing RASSF1A complementary DNA to determine whether exogenous expression of RASSF1A would affect in vitro growth and in vivo tumorigenicity of this cell line. All statistical tests were two-sided.
RASSF1A messenger RNA was expressed in nonmalignant epithelial cultures but not in 100% of the SCLC, in 65% of the NSCLC, or in 60% of the breast cancer lines. By contrast, RASSF1C was expressed in all nonmalignant cell cultures and in nearly all cancer cell lines. RASSF1A promoter hypermethylation was detected in 100% of SCLC, in 63% of NSCLC, in 64% of breast cancer lines, in 30% of primary NSCLCs, and in 49% of primary breast tumors but in none of the nonmalignant lung tissues. RASSF1A promoter hypermethylation in resected NSCLCs was associated with impaired patient survival (P = .046). Exogenous expression of RASSF1A in a cell line lacking expression decreased in vitro colony formation and in vivo tumorigenicity.
RASSF1A is a potential tumor suppressor gene that undergoes epigenetic inactivation in lung and breast cancers through hypermethylation of its promoter region.
Carcinogenesis is an adaptive process between nascent tumor cells and their microenvironment including the modification of inflammatory responses from anti-tumorigenic to pro-tumorigenic. Radiation exposure can stimulate inflammatory responses that inhibit or promote carcinogenesis. The purpose of this study is to determine the impact of radiation exposure on lung cancer progression in vivo and assess the relevance of this knowledge to human carcinogenesis.
K-rasLA1 mice were irradiated with various doses and dose regimens and then monitored till death. Microarray analyses were performed using Illumina® BeadChips on whole lung tissue 70 days post-irradiation with a fractionated or acute dose of radiation and compared to age-matched unirradiated controls. Unique group classifiers were derived by comparative genomic analysis of three experimental cohorts. Survival analyses were performed using principal component analysis and k-means clustering on three lung adenocarcinoma, three breast adenocarcinoma, and two lung squamous carcinoma annotated microarray datasets.
Radiation exposure accelerates lung cancer progression in the K-rasLA1 lung cancer mouse model with dose fractionation being more permissive for cancer progression. A non-random inflammatory signature associated with this progression was elicited from whole lung tissue containing only benign lesions and predicts human lung and breast cancer patient survival across multiple datasets. Immunohistochemical analyses suggest that tumor cells drive predictive signature.
These results demonstrate that radiation exposure can cooperate with benign lesions in a transgenic model of cancer by impacting inflammatory pathways, and that clinically relevant similarities exist between human lung and breast carcinogenesis.
Radiation; Lung Cancer; Progression; Mouse models; Genomics
Genetic analyses of lung cancer have helped found new treatments in this disease. We conducted an integrative analysis of gene expression and copy number in 261 non-small cell lung cancers (NSCLC) relative to matched normal tissues to define novel candidate oncogenes, identifying 12q13-15 and more specifically the YEATS4 gene as amplified and overexpressed in ~20% of the NSCLC cases examined. Overexpression of YEATS4 abrogated senescence in human bronchial epithelial cells (HBECs). Conversely, RNAi-mediated attenuation of YEATS4 in human lung cancer cells reduced their proliferation and tumor growth, impairing colony formation and inducing cellular senescence. These effects were associated with increased levels of p21WAF1 and p53 and cleavage of PARP, implicating YEATS4 as a negative regulator of the p21-p53 pathway. We also found that YEATS4 expression affected cellular responses to cisplastin, with increased levels associated with resistance and decreased levels with sensitivity. Taken together, our findings reveal YEATS4 as a candidate oncogene amplified in NSCLC, and a novel mechanism contributing to NSCLC pathogenesis.
YEATS4; NSCLC; oncogene; p53; integrative analysis
Context-specific molecular vulnerabilities that arise during tumor evolution represent an attractive intervention target class. However, the frequency and diversity of somatic lesions detected among lung tumors can confound efforts to identify these targets. To confront this challenge, we have applied parallel screening of chemical and genetic perturbations within a panel of molecularly annotated NSCLC lines to identify intervention opportunities tightly linked to molecular response indicators predictive of target sensitivity. Anchoring this analysis on a matched tumor/normal cell model from a lung adenocarcinoma patient identified three distinct target/response-indicator pairings that are represented with significant frequencies (6–16%) in the patient population. These include NLRP3 mutation/inflammasome activation-dependent FLIP addiction, co-occuring KRAS and LKB1 mutation-driven COPI addiction, and selective sensitivity to a synthetic indolotriazine that is specified by a 7-gene expression signature. Target efficacies were validated in vivo, and mechanism of action studies uncovered new cancer cell biology.
We used CDK4/hTERT-immortalized normal human bronchial epithelial cells (HBECs) from several individuals to study lung cancer pathogenesis by introducing combinations of common lung cancer oncogenic changes (p53, KRAS, MYC) and followed the stepwise transformation of HBECs to full malignancy. This model demonstrated that: 1) the combination of five genetic alterations (CDK4, hTERT, sh-p53, KRASV12, and c-MYC) is sufficient for full tumorigenic conversion of HBECs; 2) genetically-identical clones of transformed HBECs exhibit pronounced differences in tumor growth, histology, and differentiation; 3) HBECs from different individuals vary in their sensitivity to transformation by these oncogenic manipulations; 4) high levels of KRASV12 are required for full malignant transformation of HBECs, however prior loss of p53 function is required to prevent oncogene-induced senescence; 5) over-expression of c-MYC greatly enhances malignancy but only in the context of sh-p53+KRASV12; 6) growth of parental HBECs in serum-containing medium induces differentiation while growth of oncogenically manipulated HBECs in serum increases in vivo tumorigenicity, decreases tumor latency, produces more undifferentiated tumors, and induces epithelial-to-mesenchymal transition (EMT); 7) oncogenic transformation of HBECs leads to increased sensitivity to standard chemotherapy doublets; 8) an mRNA signature derived by comparing tumorigenic vs. non-tumorigenic clones was predictive of outcome in lung cancer patients. Collectively, our findings demonstrate this HBEC model system can be used to study the effect of oncogenic mutations, their expression levels, and serum-derived environmental effects in malignant transformation, while also providing clinically translatable applications such as development of prognostic signatures and drug response phenotypes.
p53; KRAS; c-MYC; immortalized human bronchial epithelial cell; in vitro transformation model of lung cancer; epithelial mesenchymal transition
The last decade has seen significant advances in our understanding of lung cancer biology and management. Identification of key driver events in lung carcinogenesis has contributed to the development of targeted lung cancer therapies, heralding the era of personalised medicine for lung cancer. As a result, histological subtyping and molecular testing has become of paramount importance, placing increasing demands on often small diagnostic specimens. This has triggered the review and development of the first structured classification of lung cancer in small biopsy/cytology specimens and a new classification of lung adenocarcinoma from the IASLC/ATS/ERS. These have enhanced the clinical relevance of pathological diagnosis, and emphasise the role of the modern surgical pathologist as an integral member of the multidisciplinary team, playing a crucial role in clinical trials and determining appropriate and timely management for patients with lung cancer.
Lung Neoplasms; pathology; non-small-cell lung carcinoma (NSCLC); small cell lung carcinoma (SCLC)
Small cell lung cancer (SCLC) is a highly aggressive lung neoplasm with extremely poor clinical outcomes and no approved targeted treatments. To elucidate the mechanisms responsible for driving the SCLC phenotype in hopes of revealing novel therapeutic targets, we studied copy number and methylation profiles of SCLC. We found disruption of the E2F/Rb pathway was a prominent feature deregulated in 96% of the SCLC samples investigated and was strongly associated with increased expression of EZH2, an oncogene and core member of the polycomb repressive complex 2 (PRC2). Through its catalytic role in the PRC2 complex, EZH2 normally functions to epigenetically silence genes during development, however, it aberrantly silences genes in human cancers. We provide evidence to support that EZH2 is functionally active in SCLC tumours, exerts pro-tumourigenic functions in vitro, and is associated with aberrant methylation profiles of PRC2 target genes indicative of a “stem-cell like” hypermethylator profile in SCLC tumours. Furthermore, lentiviral-mediated knockdown of EZH2 demonstrated a significant reduction in the growth of SCLC cell lines, suggesting EZH2 has a key role in driving SCLC biology. In conclusion, our data confirm the role of EZH2 as a critical oncogene in SCLC, and lend support to the prioritization of EZH2 as a potential therapeutic target in clinical disease.
The purpose of this study was to identify key genetic pathways involved in non-small cell lung cancer (NSCLC) and understand their role in tumor progression. We performed a genome wide scanning using paired tumors and corresponding 16 mucosal biopsies from four follow-up lung cancer patients on Affymetrix 250K-NSpI array platform. We found that a single gene SH3GL2 located on human chromosome 9p22 was most frequently deleted in all the tumors and corresponding mucosal biopsies. We further validated the alteration pattern of SH3GL2 in a substantial number of primary NSCLC tumors at DNA and protein level. We also overexpressed wild-type SH3GL2 in three NSCLC cell lines to understand its role in NSCLC progression. Validation in 116 primary NSCLC tumors confirmed frequent loss of heterozygosity of SH3GL2 in overall 51 % (49/97) of the informative cases. We found significantly low (p=0.0015) SH3GL2 protein expression in 71 % (43/60) primary tumors. Forced over-expression of wild-type (wt) SH3GL2 in three NSCLC cell lines resulted in a marked reduction of active epidermal growth factor receptor (EGFR) expression and an increase in EGFR internalization and degradation. Significantly decreased in vitro (p=0.0015–0.030) and in vivo (p=0.016) cellular growth, invasion (p=0.029–0.049), and colony formation (p=0.023–0.039) were also evident in the wt-SH3GL2-transfected cells accompanied by markedly low expression of activated AKT(Ser473), STAT3 (Tyr705), and PI3K. Downregulation of SH3GL2 interactor USP9X and activated β-catenin was also evident in the SH3GL2-transfected cells. Our results indicate that SH3GL2 is frequently deleted in NSCLC and regulates cellular growth and invasion by modulating EGFR function.
Single nucleotide polymorphism array; Lung cancer; SH3GL2; Deletion
Pheochromocytomas are rare tumors generally arising in the medullary region of the adrenal gland. These tumors release excessive epinephrine and norepinephrine resulting in hypertension and cardiovascular crises for which surgery is the only definitive treatment. Molecular mechanisms that control tumor development and hormone production are poorly understood, and progress has been hampered by the lack of human cellular model systems. To study pheochromocytomas, we developed a stable progenitor pheochromocytoma cell line derived from a primary human tumor.
After IRB approval and written informed consent, human pheochromocytoma tissue was excised, minced, dispersed enzymatically, and cultured in vitro. Primary pheochromocytoma cells were infected with a lentivirus vector carrying the catalytic subunit of human telomerase reverse transcriptase (hTERT). The hTERT immortalized cells (hPheo1) have been passaged >300 population doublings. The resulting cell line was characterized morphologically, biochemically and for expression of neuroendocrine properties. The expression of marker enzymes and proteins was assessed by immunofluorescence staining and immunoblotting. Telomerase activity was determined by using the telomeric repeat amplification protocol (TRAP) assay.
We have established a human pheochromocytoma precursor cell line that expresses the neuroendocrine marker, chromogranin A, when differentiated in the presence of bone morphogenic protein 4 (BMP4), nerve growth factor (NGF), and dexamethasone. Phenylethanolamine N-methyltransferase (PNMT) expression is also detected with this differentiation regimen. CD-56 (also known as NCAM, neural cell adhesion molecule) is expressed in these cells, but CD31 (also known as PECAM-1, a marker of endothelial cells) is negative.
We have maintained hTERT-immortalized progenitor cells derived from a pheochromocytoma (hPheo1) in culture for over 300 population doublings. This progenitor human cell line is normal diploid except for a deletion in the p16 region and has inducible neuroendocrine biomarkers. These cells should be a valuable reagent for studying mechanisms of tumor development and for testing novel therapeutic approaches.