Involvement of signal transduction pathways in lung cancer biology

Differential transcriptomic analysis of spontaneous lung tumors in B6C3F1 mice: comparison to human non-small cell lung cancer

Lung cancer is the leading cause of cancer-related death in people and is mainly due to environmental factors such as smoking and radon. The National Toxicology Program (NTP) tests various chemicals and mixtures for their carcinogenic hazard potential. In the NTP chronic bioassay using B6C3F1 mice, the incidence of lung tumors in treated and control animals is second only to the liver tumors. In order to study the molecular mechanisms of chemically induced lung tumors, an understanding of the genetic changes that occur in spontaneous lung (SL) tumors from untreated control animals is needed. The authors have evaluated the differential transcriptomic changes within SL tumors compared to normal lungs from untreated age-matched animals. Within SL tumors, several canonical pathways associated with cancer (eukaryotic initiation factor 2 signaling, RhoA signaling, PTEN signaling, and mammalian target of rapamycin signaling), metabolism (Inositol phosphate metabolism, mitochondrial dysfunction, and purine and pyramidine metabolism), and immune responses (FcγR-mediated phagocytosis, clathrin-mediated endocytosis, interleukin 8 signaling, and CXCR4 signaling) were altered. Meta-analysis of murine SL tumors and human non-small cell lung cancer transcriptomic data sets revealed a high concordance. These data provide important information on the differential transcriptomic changes in murine SL tumors that will be critical to our understanding of chemically induced lung tumors and will aid in hazard analysis in the NTP 2-year carcinogenicity bioassays.

Lung cancer preneoplasia

From histological and biological perspectives, lung cancer is a complex neoplasm. Although the sequential preneoplastic changes have been defined for centrally arising squamous carcinomas of the lung, they have been poorly documented for the other major forms of lung cancers, including small cell lung carcinoma and adenocarcinomas. There are three main morphologic forms of preneoplastic lesions recognized in the lung: squamous dysplasias, atypical adenomatous hyperplasia, and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia. However, these lesions account for the development of only a subset of lung cancers. Several studies have provided information regarding the molecular characterization of lung preneoplastic changes, especially for squamous cell carcinoma. These molecular changes have been detected in the histologically normal and abnormal respiratory epithelium of smokers. Two different molecular pathways have been detected in lung adenocarcinoma pathogenesis: smoking-associated activation of RAS signaling, and nonsmoking-associated activation of EGFR signaling; the latter is detected in histologically normal respiratory epithelium.

Phosphorylated extracellular signal-regulated kinases are significantly increased in malignant mesothelioma

Tumorigenesis is associated with the activation of mitogenic signal transduction pathways. The expression of activated extracellular signal-regulated kinase (p-ERK) may play an important role in cell proliferation of malignant mesothelioma (MM). We compare the expression of p-ERK in 50 biopsy specimens of MM, non-small-cell lung cancer (NSCLC), and normal lung tissue. We hypothesized that phosphorylated extracellular signal-regulated kinase is increased in MM. We stained the sections by immunohistochemistry for activated ERK-1 and -2 and performed the quantification of the stained nuclei. Quantitative analysis of p-ERK showed a high percentage score in MM (30.3 +/- 4.6%) as compared with NSCLC (12.2 +/- 2.1%) (p<0.01) and control lung tissue (6.4 +/- 1.3%) (p=0.0002). Furthermore, p-ERK was found significantly higher in poorly differentiated NSCLC (17.7 +/- 3.1%) as compared with well-differentiated NSCLC (5.4 +/- 1.2%) (p<0.01). Our data show that the nuclear quantification of p-ERK is significantly increased in MM and poorly differentiated NSCLC in comparison to well-differentiated NSCLC and normal lung tissue. These results corroborate previous experimental studies that suggest a critical role of p-ERK in cell proliferation of malignant disease and may represent new targets for therapeutic agents.

Lung cancer-derived bombesin-like peptides down-regulate the generation and function of human dendritic cells

Development of tumors is regulated by tumor-derived neuroendocrine factors, including bombesin-like peptides (BLP). We have evaluated neuroendocrine regulation of dendritic cell (DC) maturation and function by both tumor-derived and purified bombesin (BOM), neuromedin B (NMB), gastrin-releasing peptide (GRP), and a BOM antagonist D-Phe-bombesin (DPB). BOM, NMB and GRP dose-dependently inhibited maturation of DC assessed as down-regulation of CD40, CD80 and CD86 expression on DC. BOM and GRP also inhibited interleukin-12 (IL-12) production by DC and their ability to activate T cells. DPB partly abrogated immunosuppressive effect of tumor cells on DC. These data are a first evidence for the role of BLP in the regulation of DC maturation and function, demonstrating that BLP inhibit DC maturation and longevity in the lung cancer microenvironment. This suggests a new mechanism of tumor escape and provides new targets for the immunopharmacological correction of immune effectors in cancer.

Smoking molecular damage in bronchial epithelium

Our understanding of the molecular pathology of lung cancer is advancing rapidly with several specific genes and chromosomal regions being identified. Lung cancer appears to require many mutations in both dominant and recessive oncogenes to possess malignant phenotypes. Several genetic and epigenetic changes are common to all lung cancer histologic types, while others appear to be cell type specific. However, specific roles of the genes undergoing mutations and the order of cumulative molecular changes that lead to the development of each lung tumor histologic type remain to be fully elucidated. Recent findings of molecular abnormalities in normal appearing and preneoplastic bronchial epithelium from patients with lung cancer and chronic smokers suggest that genetic changes may serve as biomarkers for early diagnosis, risk assessment and monitoring response to chemoprevention.

Molecular pathogenesis of lung cancer

Lung cancer is the most common cause of cancer death in the United States, killing more than 156,000 people every year. In the past two decades, significant progress has been made in understanding the molecular and cellular pathogenesis of lung cancer. Abnormalities of proto-oncogenes, genetic and epigenetic changes of tumor suppressor genes, the role of angiogenesis in the multistage development of lung cancer, as well as detection of molecular abnormalities in preinvasive respiratory lesions, have recently come into focus. Efforts are ongoing to translate these findings into new clinical strategies for risk assessment, chemoprevention, early diagnosis, treatment selection, and prognosis and to provide new targets and methods of treatment for lung cancer patients. All these strategies should aid in reducing the number of newly diagnosed lung cancer cases and in increasing the survival and quality of life of patients with lung cancer.

The inhibition of lung cancer cell growth by intracellular immunization with LC-1 ScFv

A monoclonal antibody, LC-1, recognizing lung cancer associated common antigens was obtained in authors' laboratory. Its single chain Fv fragment (ScFv) named LC-1 ScFv was constructed based on recombinant phage displayed techniques. For expression on cell membrane, LC-1 ScFv was cloned into pDisplay vector, which directed the cloned gene to express as cell membrane bound protein. The resulting plasmid was sequenced and then introduced by the lipofectin method into a lung adenocarcinoma cell line SPC-A-1. G418 resistant cells were obtained by G418 selection. After transfection, LC-1 ScFv expression was observed by Western blot analysis and the expression of cognate antigens was down-regulated as shown in ELISA assay. SPC-A-1-pDisplay-ScFv cells grew in vitro at lower speed than the control intact cells and the cells transfected with vacant vector. Flow cytometry analysis detected a substantial increase in G1 phase and decrease in S phase in population of SPC-A-1-pDisplay-ScFv cells compared to SPC-A-1 and SPC-A-1-pDisplay cells. Semi-quantitative RT-PCR analysis showed that c-myc expression was down-regulated in SPC-A-1-pDisplay-ScFv cells. It seems that the antigens recognized by LC-1 may be in some way involved in a growth stimulating pathway and the antibody blocking of the function of the antigens shut down the pathway and thus down-regulate the expression of c-myc and growth of the cells.

c-mos immunoreactivity is an indicator of good prognosis in lung cancer

AIMS

Reports concerning the expression of cytoplasmic components of the mitogen-activating protein kinase (MAPK) pathway in lung cancer are limited. One of the molecules participating in this pathway is the product of the c-mos proto-oncogene. In vitro investigations, in somatic cells, have shown that c-mos expression has opposing effects on cell cycle progression suggesting that it may represent an important determinant of aberrant cell function. In this study we analysed, by immunohistochemical means, its status in a series of lung carcinomas and correlated the findings with clinicopathological parameters and survival of the patients.

METHODS AND RESULTS

Sixty cases of lung carcinomas were included in the study. These comprised 52 non-small (NSCLCs) and eight small cell lung carcinomas (SCLCs). Sections from the carcinomas were immunostained with the polyclonal anti-c-mos antibody P-19. Specificity was tested by using the appropriate control peptide and control cell lines. Expression was observed in 63% of the cases, with NSCLCs showing higher reactivity (67%) than SCLCs (37.5%). Staining was observed mainly to the cytoplasm and membranes of the cancerous cells, but some nuclei reacted as well. An intratumour heterogeneous immunoreactivity was noticed. The most interesting and unexpected finding was that c-mos positive staining was associated with better recurrence-free survival in our series, regardless of histological type (P = 0.035). Furthermore, favourable disease-related and recurrence-free survival was observed in the SqC group with c-mos immunoreactivity (P < 0. 001).

CONCLUSIONS

c-mos proto-oncogene is expressed in a significant proportion of lung carcinomas and may play a role in its development. The fact that its expression is associated with a relatively good prognosis may be indicative of a negative impact on tumour growth.

Progress in understanding the molecular pathogenesis of human lung cancer

We review the molecular pathogenesis of lung cancer including alterations in dominant oncogenes, recessive oncogenes/tumor suppressor genes, alterations in growth regulatory signaling pathways, abnormalities in other pathways, such as apoptosis, autocrine and paracrine growth stimulatory loops, angiogenesis, and host immune responses, other mechanisms of genetic changes, such as microsatellite and methylation alterations, and the potential for inherited predisposition to lung cancer. These changes are related to multistage carcinogenesis involving preneoplastic lesions, and lung development and differentiation. The translational applications of these findings for developing new ways of early detection, prevention, treatment, and prognosis of lung cancer are discussed.