Common and contrasting genomic profiles among the major human lung cancer subtypes

A role for club cells in smoking-associated lung adenocarcinoma

The cellular origin of lung adenocarcinoma remains a focus of intense research efforts. The marked cellular heterogeneity and plasticity of the lungs, as well as the vast variety of molecular subtypes of lung adenocarcinomas perplex the field and account for the extensive variability of experimental results. While most experts would agree on the cellular origins of other types of thoracic tumours, great controversy exists on the tumour-initiating cells of lung adenocarcinoma, since this histologic subtype of lung cancer arises in the distal pulmonary regions where airways and alveoli converge, occurs in smokers as well as nonsmokers, is likely caused by various environmental agents, and is marked by vast molecular and pathologic heterogeneity. Alveolar type II, club, and their variant cells have all been implicated in lung adenocarcinoma progeny and the lineage hierarchies in the distal lung remain disputed. Here we review the relevant literature in this rapidly expanding field, including results from mouse models and human studies. In addition, we present a case for club cells as cells of origin of lung adenocarcinomas that arise in smokers.

Multiple lung epithelial cells are targets of carcinogenic hits. Club cells are such cells that can metabolically activate tobacco pre-carcinogens, being thus positioned as cells of origin of lung adenocarcinomas in smokers.https://bit.ly/3iOshcy

ICRP Publication 131: Stem Cell Biology with Respect to Carcinogenesis Aspects of Radiological Protection

This report provides a review of stem cells/progenitor cells and their responses to ionising radiation in relation to issues relevant to stochastic effects of radiation that form a major part of the International Commission on Radiological Protection's system of radiological protection. Current information on stem cell characteristics, maintenance and renewal, evolution with age, location in stem cell 'niches', and radiosensitivity to acute and protracted exposures is presented in a series of substantial reviews as annexes concerning haematopoietic tissue, mammary gland, thyroid, digestive tract, lung, skin, and bone. This foundation of knowledge of stem cells is used in the main text of the report to provide a biological insight into issues such as the linear-no-threshold (LNT) model, cancer risk among tissues, dose-rate effects, and changes in the risk of radiation carcinogenesis by age at exposure and attained age. Knowledge of the biology and associated radiation biology of stem cells and progenitor cells is more developed in tissues that renew fairly rapidly, such as haematopoietic tissue, intestinal mucosa, and epidermis, although all the tissues considered here possess stem cell populations. Important features of stem cell maintenance, renewal, and response are the microenvironmental signals operating in the niche residence, for which a well-defined spatial location has been identified in some tissues. The identity of the target cell for carcinogenesis continues to point to the more primitive stem cell population that is mostly quiescent, and hence able to accumulate the protracted sequence of mutations necessary to result in malignancy. In addition, there is some potential for daughter progenitor cells to be target cells in particular cases, such as in haematopoietic tissue and in skin. Several biological processes could contribute to protecting stem cells from mutation accumulation: (a) accurate DNA repair; (b) rapidly induced death of injured stem cells; (c) retention of the DNA parental template strand during divisions in some tissue systems, so that mutations are passed to the daughter differentiating cells and not retained in the parental cell; and (d) stem cell competition, whereby undamaged stem cells outcompete damaged stem cells for residence in the niche. DNA repair mainly occurs within a few days of irradiation, while stem cell competition requires weeks or many months depending on the tissue type. The aforementioned processes may contribute to the differences in carcinogenic radiation risk values between tissues, and may help to explain why a rapidly replicating tissue such as small intestine is less prone to such risk. The processes also provide a mechanistic insight relevant to the LNT model, and the relative and absolute risk models. The radiobiological knowledge also provides a scientific insight into discussions of the dose and dose-rate effectiveness factor currently used in radiological protection guidelines. In addition, the biological information contributes potential reasons for the age-dependent sensitivity to radiation carcinogenesis, including the effects of in-utero exposure.

ICRP Publication 131: Stem cell biology with respect to carcinogenesis aspects of radiological protection

Current knowledge of stem cell characteristics, maintenance and renewal, evolution with age, location in 'niches', and radiosensitivity to acute and protracted exposures is reviewed regarding haematopoietic tissue, mammary gland, thyroid, digestive tract, lung, skin, and bone. The identity of the target cells for carcinogenesis continues to point to the more primitive and mostly quiescent stem cell population (able to accumulate the protracted sequence of mutations necessary to result in malignancy), and, in a few tissues, to daughter progenitor cells. Several biological processes could contribute to the protection of stem cells from mutation accumulation: (1) accurate DNA repair; (2) rapid induced death of injured stem cells; (3) retention of the intact parental strand during divisions in some tissues so that mutations are passed to the daughter differentiating cells; and (4) stem cell competition, whereby undamaged stem cells outcompete damaged stem cells for residence in the vital niche. DNA repair mainly operates within a few days of irradiation, while stem cell replications and competition require weeks or many months depending on the tissue type. This foundation is used to provide a biological insight to protection issues including the linear-non-threshold and relative risk models, differences in cancer risk between tissues, dose-rate effects, and changes in the risk of radiation carcinogenesis by age at exposure and attained age.

Alterations of p63 and p73 in human cancers

p53 and its related genes, p63 and p73 constitute the p53 gene family. While p53 is the most frequently mutated gene in human tumors, p63 and p73 are rarely mutated or deleted in cancers. Many studies have reported p63/p73 overexpression in human cancers while others showed that a loss of p63/p73 is associated with tumor progression and metastasis. Thus, whether p63 or p73 is a tumor suppressor gene or an oncogene has been a matter of debate. This controversy has been attributed to the existence of multiple splicing isoforms with distinct functions; the full-length TA isoform of p63 has structural and functional similarity to wild-type p53, whereas the ΔNp63 acts primarily in dominant-negative fashion against all family members of p53. Differential activities of TA and ΔN isoforms have been shown in vivo by creating isform-specific gene knockout mice. All p53, p63, p73 proteins bind to and activate target genes with p53-response elements; p63 also binds to distinct p63-response elements and regulate expression of specific target genes involved in skin, limb, and craniofacial development. Interestingly, several studies have shown that both p63 and p73 are involved in cellular response to cancer therapy and others have indicated that both of these molecules are required for p53-induced apoptosis, suggesting functional interplay among p53 family proteins. Consistent with these findings, aberrant splicing that result in ΔNp63 or ΔNp73 overexpression are frequently found in human cancers, and is associated with poor clinical outcomes of patients in the latter. Thus immunohistochemical staining of tumor specimen with ΔNp73-specific antibody might have diagnostic values in cancer clinics.

Dysfunction of nucleus accumbens-1 activates cellular senescence and inhibits tumor cell proliferation and oncogenesis

Nucleus accumbens-1 (NAC1), a nuclear factor belonging to the BTB/POZ gene family, has emerging roles in cancer. We report here that NAC1 acts as a negative regulator of cellular senescence in transformed and nontransformed cells, and dysfunction of NAC1 induces senescence and inhibits its oncogenic potential. We show that NAC1 deficiency markedly activates senescence and inhibits proliferation in tumor cells treated with sublethal doses of γ-irradiation. In mouse embryonic fibroblasts from NAC1 knockout mice, following infection with a Ras virus, NAC1-/- cells undergo significantly more senescence and are either nontransformed or less transformed in vitro and less tumorigenic in vivo when compared with NAC1+/+ cells. Furthermore, we show that the NAC1-caused senescence blunting is mediated by ΔNp63, which exerts its effect on senescence through p21, and that NAC1 activates transcription of ΔNp63 under stressful conditions. Our results not only reveal a previously unrecognized function of NAC1, the molecular pathway involved and its impact on pathogenesis of tumor initiation and development, but also identify a novel senescence regulator that may be exploited as a potential target for cancer prevention and treatment.

Aurora Kinase A expression is associated with lung cancer histological-subtypes and with tumor de-differentiation

BACKGROUND

Aurora kinase A (AURKA) is a member of serine/threonine kinase family. Several kinases belonging to this family are activated in the G2/M phase of the cell cycle being involved in mitotic chromosomal segregation. AURKA overexpression is significantly associated with neoplastic transformation in several tumors and deregulated Aurora Kinases expression leads to chromosome instability, thus contributing to cancer progression. The purpose of the present study was to investigate the expression of AURKA in non small cell lung cancer (NSCLC) specimens and to correlate its mRNA or protein expression with patients' clinico-pathological features.

MATERIALS AND METHODS

Quantitative real-time PCR and immunohistochemistry analysis on matched cancer and corresponding normal tissues from surgically resected non-small cell lung cancers (NSCLC) have been performed aiming to explore the expression levels of AURKA gene.

RESULTS

AURKA expression was significantly up-modulated in tumor samples compared to matched lung tissue (p<0.01, mean log2(FC)=1.5). Moreover, AURKA was principally up-modulated in moderately and poorly differentiated lung cancers (p<0.01), as well as in squamous and adenocarcinomas compared to the non-invasive bronchioloalveolar histotype (p=0.029). No correlation with survival was observed.

CONCLUSION

These results indicate that in NSCLC AURKA over-expression is restricted to specific subtypes and poorly differentiated tumors.

ΔNp63α is an oncogene that targets chromatin remodeler Lsh to drive skin stem cell proliferation and tumorigenesis

The p53 homolog p63 is essential for development, yet its role in cancer is not clear. We discovered that p63 deficiency evokes the tumor-suppressive mechanism of cellular senescence, causing a striking absence of stratified epithelia such as the skin. Here we identify the predominant p63 isoform, ΔNp63α, as a protein that bypasses oncogene-induced senescence to drive tumorigenesis in vivo. Interestingly, bypass of senescence promotes stem-like proliferation and maintains survival of the keratin 15-positive stem cell population. Furthermore, we identify the chromatin-remodeling protein Lsh as a new target of ΔNp63α that is an essential mediator of senescence bypass. These findings indicate that ΔNp63α is an oncogene that cooperates with Ras to promote tumor-initiating stem-like proliferation and suggest that Lsh-mediated chromatin-remodeling events are critical to this process.

The role of p63 in cancer, stem cells and cancer stem cells

The transcription factor p63 has important functions in tumorigenesis, epidermal differentiation and stem cell self-renewal. The TP63 gene encodes multiple protein isoforms that have different or even antagonistic roles in these processes. The balance of p63 isoforms, together with the presence or absence of the other p53 family members, p73 and p53, has a striking biological impact. There is increasing evidence that interactions between p53-family members, whether cooperative or antagonistic, are involved in various cell processes. This review summarizes the current understanding of the role of p63 in tumorigenesis, metastasis, cell migration and senescence. In particular, recent data indicate important roles in adult stem cell and cancer stem cell regulation and in the response of cancer cells to therapy.

International association for the study of lung cancer/american thoracic society/european respiratory society international multidisciplinary classification of lung adenocarcinoma

INTRODUCTION

Adenocarcinoma is the most common histologic type of lung cancer. To address advances in oncology, molecular biology, pathology, radiology, and surgery of lung adenocarcinoma, an international multidisciplinary classification was sponsored by the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society. This new adenocarcinoma classification is needed to provide uniform terminology and diagnostic criteria, especially for bronchioloalveolar carcinoma (BAC), the overall approach to small nonresection cancer specimens, and for multidisciplinary strategic management of tissue for molecular and immunohistochemical studies.

METHODS

An international core panel of experts representing all three societies was formed with oncologists/pulmonologists, pathologists, radiologists, molecular biologists, and thoracic surgeons. A systematic review was performed under the guidance of the American Thoracic Society Documents Development and Implementation Committee. The search strategy identified 11,368 citations of which 312 articles met specified eligibility criteria and were retrieved for full text review. A series of meetings were held to discuss the development of the new classification, to develop the recommendations, and to write the current document. Recommendations for key questions were graded by strength and quality of the evidence according to the Grades of Recommendation, Assessment, Development, and Evaluation approach.

RESULTS

The classification addresses both resection specimens, and small biopsies and cytology. The terms BAC and mixed subtype adenocarcinoma are no longer used. For resection specimens, new concepts are introduced such as adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA) for small solitary adenocarcinomas with either pure lepidic growth (AIS) or predominant lepidic growth with ≤ 5 mm invasion (MIA) to define patients who, if they undergo complete resection, will have 100% or near 100% disease-specific survival, respectively. AIS and MIA are usually nonmucinous but rarely may be mucinous. Invasive adenocarcinomas are classified by predominant pattern after using comprehensive histologic subtyping with lepidic (formerly most mixed subtype tumors with nonmucinous BAC), acinar, papillary, and solid patterns; micropapillary is added as a new histologic subtype. Variants include invasive mucinous adenocarcinoma (formerly mucinous BAC), colloid, fetal, and enteric adenocarcinoma. This classification provides guidance for small biopsies and cytology specimens, as approximately 70% of lung cancers are diagnosed in such samples. Non-small cell lung carcinomas (NSCLCs), in patients with advanced-stage disease, are to be classified into more specific types such as adenocarcinoma or squamous cell carcinoma, whenever possible for several reasons: (1) adenocarcinoma or NSCLC not otherwise specified should be tested for epidermal growth factor receptor (EGFR) mutations as the presence of these mutations is predictive of responsiveness to EGFR tyrosine kinase inhibitors, (2) adenocarcinoma histology is a strong predictor for improved outcome with pemetrexed therapy compared with squamous cell carcinoma, and (3) potential life-threatening hemorrhage may occur in patients with squamous cell carcinoma who receive bevacizumab. If the tumor cannot be classified based on light microscopy alone, special studies such as immunohistochemistry and/or mucin stains should be applied to classify the tumor further. Use of the term NSCLC not otherwise specified should be minimized.

CONCLUSIONS

This new classification strategy is based on a multidisciplinary approach to diagnosis of lung adenocarcinoma that incorporates clinical, molecular, radiologic, and surgical issues, but it is primarily based on histology. This classification is intended to support clinical practice, and research investigation and clinical trials. As EGFR mutation is a validated predictive marker for response and progression-free survival with EGFR tyrosine kinase inhibitors in advanced lung adenocarcinoma, we recommend that patients with advanced adenocarcinomas be tested for EGFR mutation. This has implications for strategic management of tissue, particularly for small biopsies and cytology samples, to maximize high-quality tissue available for molecular studies. Potential impact for tumor, node, and metastasis staging include adjustment of the size T factor according to only the invasive component (1) pathologically in invasive tumors with lepidic areas or (2) radiologically by measuring the solid component of part-solid nodules.

Frequent loss of heterozygosity on chromosome 12q in non-small-cell lung carcinomas

Chromosomal aberrations in non-small-cell lung carcinomas (NSCLCs) are common events. In our study, the lung cancer cell lines (NCI-H446 and SPC-A-1) displayed numerous numerical and structural alterations in their chromosomes by G-banded karyotypic analysis, and abnormalities of chromosome 12 by fluorescence in situ hybridization. Sequentially, we used 14 microsatellite markers within 12q to analyze loss of heterozygosity (LOH) in lung cancer cell lines and NSCLCs. Possible LOH on 12q were statistically inferred to occur in five lung cell lines. Importantly, 17 out of 25 NSCLCs (68%) showed LOH at chromosome 12q. Frequencies of LOH for individual markers ranged from 18% to 44%. Several deletions which were marked with D12S1301, D12S2196, D12S398, D12S90, D12S1056, D12S1713, D12S375, D12S1040, D12S326, and D12S106 were newly detected. Allelic loss on 12q15-q21 detected with D12S1040 occurred at the later stages of NSCLC progression (p < 0.05, Fisher's exact test). LOH on 12q marked with D12S2196, D12S398, D12S326, and D12S106 were frequently found in NSCLCs from the patients without smoking history (p < 0.05, Fisher's exact test). These findings indicated that allelic loss on 12q is commonly involved in NSCLCs, and new tumor suppressor genes may occur within 12q.

Regulation of p53 family member isoform DeltaNp63alpha by the nuclear factor-kappaB targeting kinase IkappaB kinase beta

The p53 family gene p63 plays an instrumental role in cellular stress responses including responses to DNA damage. In addition to encoding a full-length transcriptional activator, p63 also encodes several dominant inhibitory isoforms including the isoform DeltaNp63alpha, the function of which is not fully understood. DeltaNp63alpha is degraded in response to DNA damage, thereby enabling an effective cellular response to genotoxic agents. Here, we identify a key molecular mechanism underlying regulation of DeltaNp63alpha expression in response to chemotherapeutic agents or tumor necrosis factor-alpha. We found that DeltaNp63alpha interacts with IkappaB kinase (IKK), a multisubunit protein kinase that consists of two catalytic subunits, IKKalpha and IKKbeta, and a regulatory subunit, IKKgamma. The IKKbeta kinase promotes ubiquitin-mediated proteasomal degradation of DeltaNp63alpha, whereas a kinase-deficient mutant IKKbeta-K44A fails to do so. Cytokine- or chemotherapy-induced stimulation of IKKbeta caused degradation of DeltaNp63alpha and augmented transactivation of p53 family-induced genes involved in the cellular response to DNA damage. Conversely, IKKbeta inhibition attenuated cytokine- or chemotherapy-induced degradation of DeltaNp63alpha. Our findings show that IKKbeta plays an essential role in regulating DeltaNp63alpha in response to extrinsic stimuli. IKK activation represents one mechanism by which levels of DeltaNp63alpha can be reduced, thereby rendering cells susceptible to cell death in the face of cellular stress or DNA damage.

Amplification of chromosomal segment 4q12 in non-small cell lung cancer

In cancer, proto-oncogenes are often altered by genomic amplification. Here we report recurrent focal amplifications of chromosomal segment 4q12 overlapping the proto-oncogenes PDGFRA and KIT in non-small cell lung cancer (NSCLC). Single nucleotide polymorphism (SNP) array and fluorescent in situ hybridization (FISH) analysis indicate that 4q12 is amplified in 3-7% of lung adenocarcinomas and 8-10% of lung squamous cell carcinomas. In addition, we demonstrate that the NSCLC cell line NCI-H1703 exhibits focal amplification of PDGFRA and is dependent on PDGFRalpha activity for cell growth. Treatment of NCI-H1703 cells with PDGFRA-specific shRNAs or with the PDGFRalpha/KIT small molecule inhibitors imatinib or sunitinib leads to cell growth inhibition. However, these observations do not extend to NSCLC cell lines with lower-amplitude and broader gains of chromosome 4q. Together these observations implicate PDGFRA and KIT as potential oncogenes in NSCLC, but further study is needed to define the specific characteristics of those tumors that could respond to PDGFRalpha/KIT inhibitors.

Identification of Las2, a major modifier gene affecting the Pas1 mouse lung tumor susceptibility locus

Lung cancer is the leading cause of cancer death worldwide. Here, we describe a genome-wide association study of chemically induced lung tumorigenesis on 593 mice from 21 inbred strains using 115,904 genotyped and 1,952,918 imputed single nucleotide polymorphisms (SNPs). Using a genetic background-controlled genome search, we identified a novel lung tumor susceptibility gene Las2 (Lung adenoma susceptibility 2) on distal chromosome 18. Las2 showed strong association with resistance to tumor induction (rs30245983; P = 1.87 x 10(-9)) as well as epistatic interactions (P = 1.71 x 10(-3)) with the pulmonary adenoma susceptibility 1 locus, a major locus affecting mouse lung tumor development (rs13459098, P = 5.64 x 10(-27)). Sequencing analysis revealed four nonsynonymous SNPs and two insertions/deletions in the susceptible allele of Las2, resulting in the loss of tumor suppressor activities in both cell colony formation and nude mouse tumorigenicity assays. Deletion of LAS2 was observed in approximately 40% of human lung adenocarcinomas, implying that loss of function of LAS2 may be a key step for lung tumorigenesis.

Copy-number variation: the end of the human genome?

Copy-number variation (CNV)--the presence of additional or missing segments of chromosomes in some individuals--has been found to be abundant in humans and adds another dimension of variation to the genome. Copy-number variants have already been associated with some diseases and disease susceptibilities and are likely to prove as significant as sequence polymorphisms in this respect. Changes in copy number of parts of the genome are known to be a feature of many cancers, and their analysis is expected to reveal genes involved in carcinogenesis. This article will present a somewhat biased and occasionally speculative discussion of the current and future significance of CNV with a particular focus on the potential of molecular copy-number counting in the analysis of small, damaged or heterogeneous samples.

SELDI-TOF proteomic profiling of breast carcinomas identifies clinicopathologically relevant groups of patients similar to previously defined clusters from cDNA expression

Expression profiling and biomarker(s) discovery aim to provide means for tumour diagnosis, classification, therapy response and prognosis. The identification of novel markers could potentially lead to the building of robust early detection strategies and personalized, effective breast cancer therapies that would improve patient outcome. Recent evidence supports the hypothesis that genomic expression profiling using microarray analysis is a reliable method for breast cancer classification and prognostication. However, genes clearly do not act by themselves, or indeed they do not have catalytic or signalling capabilities. Hence, genetic biomarker information alone cannot perfectly predict cancer and its response to treatment. Genes clearly exert their effect after transcription through translation into active proteins. Consequently, postgenomic projects correlating protein expression profiles with tumour classification have led to some established biomarkers. In this regard, these biomarkers associate with disease prediction and can be associated with treatment response. Recently, Brozokova and colleagues demonstrated that surface-enhanced laser desorption ionization time of flight mass spectrometry (SELDI-TOF MS) profiling of breast cancer tissue proteomes can potentially expand the biomarker repertoire and our knowledge of breast cancer behaviour.

Screening of microsatellite markers in penile cancer reveals differences between metastatic and nonmetastatic carcinomas

Penile cancer, observed only rarely in the western world, represents a carcinoma that may be cured by resection of primary lesion and in case of lymph node metastasis by early lymph node dissection. This early inguinal lymphadenectomy bares a significant better survival even in cases of nonpalpable lymph nodes, but carries also a high risk of overtreatment, especially in lower tumor stages. Due to the low incidence, only few data are available on the molecular genetic background of this tumor, especially concerning tumor progression and metastasis. Therefore, we studied 62 microsatellite markers in 28 penile carcinomas searching for markers predicting progression or outcome. LOH in more than 25% of primary tumors was found on six different chromosomes, including 2q, 6p, 8q, 9p, 12q and 17p13. Statistically significant correlations could be established in D6S260 to clinical outcome and in markers from chromosomes 6, 9 and 12 to tumor stage and metastasis. These regions are worthy for further analysis concerning tumor suppressor genes and metastasis suppressor genes.