The pattern of K-ras mutation in pulmonary adenocarcinoma defines a new pathway of tumour development in the human lung

PKC Is Required for KRAS-Driven Lung Tumorigenesis

Non-small cell lung cancer (NSCLC) is the most frequent subtype of lung cancer and remains a highly lethal malignancy and one of the leading causes of cancer-related deaths worldwide. Mutant KRAS is the prevailing oncogenic driver of lung adenocarcinoma, the most common histologic form of NSCLC. In this study, we examined the role of PKCϵ, an oncogenic kinase highly expressed in NSCLC and other cancers, in KRAS-driven tumorigenesis. Database analysis revealed an association between PKCϵ expression and poor outcome in patients with lung adenocarcinoma specifically harboring KRAS mutations. A PKCϵ-deficient, conditionally activatable allele of oncogenic Kras (LSL-Kras^G12D ;PKCϵ^-/- mice) demonstrated the requirement of PKCϵ for Kras-driven lung tumorigenesis in vivo, which was consistent with impaired transformed growth reported in PKCϵ-deficient KRAS-dependent NSCLC cells. Moreover, PKCϵ-knockout mice were found to be less susceptible to lung tumorigenesis induced by benzo[a]pyrene, a carcinogen that induces mutations in Kras. Mechanistic analysis using RNA sequencing revealed little overlap for PKCϵ and KRAS in the control of genes and biological pathways relevant in NSCLC, suggesting that a permissive role of PKCϵ in KRAS-driven lung tumorigenesis may involve nonredundant mechanisms. Our results thus, highlight the relevance and potential of targeting PKCϵ for lung cancer therapeutics. SIGNIFICANCE: These findings demonstrate that KRAS-mediated tumorigenesis requires PKCϵ expression and highlight the potential for developing PKCϵ-targeted therapies for oncogenic RAS-driven malignancies.

Chronic lung injury by constitutive expression of activation-induced cytidine deaminase leads to focal mucous cell metaplasia and cancer

Activation-induced cytidine deaminase (AID) is an enzyme required for antibody diversification, and it causes DNA mutations and strand breaks. Constitutive AID expression in mice invariably caused lung lesions morphologically similar to human atypical adenomatous hyperplasia (AAH), which can be a precursor of bronchioloalveolar carcinoma. Similar to AAH, mouse AAH-like lesion (MALL) exhibited signs of alveolar differentiation, judging from the expression of alveolar type II (AT2) cell marker surfactant protein C (SP-C). However, electron microscopy indicated that MALL, which possessed certain features of a mucous cell, is distinct from an AAH or AT2 cell. Although MALL developed in all individuals within 30 weeks after birth, lung tumors occurred in only 10%; this suggests that the vast majority of MALLs fail to grow into visible tumors. MALL expressed several recently described markers of lung alveolar regeneration such as p63, keratin 5, keratin 14, leucine-rich repeat containing G protein-coupled receptor 5 (Lgr5), and Lgr6. Increased cell death was observed in the lungs of AID transgenic mice compared with wild-type mice. Based on these observations, we speculate that MALL is a regenerating tissue compensating for cellular loss caused by AID cytotoxicity. AID expression in such regenerating tissue should predispose cells to malignant transformation via its mutagenic activity.

The cell of origin and subtype of K-Ras-induced lung tumors are modified by Notch and Sox2

K-Ras activation with a CC10(Scgb1a1)-CreER driver leads to lung adenocarcinoma in a subset of alveolar type II cells and hyperplasia in the bronchioalveolar duct region. Xu et al. find that Notch inhibition strongly inhibits adenocarcinoma formation but promotes squamous hyperplasia in the alveoli. In contrast, activation of Notch leads to widespread Sox2⁺, Sox9⁺, and CC10⁺ papillary adenocarcinomas throughout the bronchioles. Sox2 binds to NOTCH1 and NOTCH2 regulatory regions and reduces Notch1 and Notch2 transcripts. This study shows that the cell of origin of K-Ras-induced tumors depends on levels of Sox2 expression affecting Notch signaling.

Cell type-specific conditional activation of oncogenic K-Ras is a powerful tool for investigating the cell of origin of adenocarcinomas in the mouse lung. Our previous studies showed that K-Ras activation with a CC10(Scgb1a1)-CreER driver leads to adenocarcinoma in a subset of alveolar type II cells and hyperplasia in the bronchioalveolar duct region. However, no tumors develop in the bronchioles, although recombination occurs throughout this region. To explore underlying mechanisms, we simultaneously modulated either Notch signaling or Sox2 levels in the CC10⁺ cells along with activation of K-Ras. Inhibition of Notch strongly inhibits adenocarcinoma formation but promotes squamous hyperplasia in the alveoli. In contrast, activation of Notch leads to widespread Sox2⁺, Sox9⁺, and CC10⁺ papillary adenocarcinomas throughout the bronchioles. Chromatin immunoprecipitation demonstrates Sox2 binding to NOTCH1 and NOTCH2 regulatory regions. In transgenic mouse models, overexpression of Sox2 leads to a significant reduction of Notch1 and Notch2 transcripts, while a 50% reduction in Sox2 leads to widespread papillary adenocarcinoma in the bronchioles. Taken together, our data demonstrate that the cell of origin of K-Ras-induced tumors in the lung depends on levels of Sox2 expression affecting Notch signaling. In addition, the subtype of tumors arising from type II cells is determined in part by Notch activation or suppression.

Evidence for type II cells as cells of origin of K-Ras-induced distal lung adenocarcinoma

Identifying the cells of origin of lung cancer may lead to new therapeutic strategies. Previous work has focused upon the putative bronchoalveolar stem cell at the bronchioalveolar duct junction as a cancer cell of origin when a codon 12 K-Ras mutant is induced via adenoviral Cre inhalation. In the present study, we use two "knock-in" Cre-estrogen receptor alleles to inducibly express K-RasG12D in CC10(+) epithelial cells and Sftpc(+) type II alveolar cells of the adult mouse lung. Analysis of these mice identifies type II cells, Clara cells in the terminal bronchioles, and putative bronchoalveolar stem cells as cells of origin for K-Ras-induced lung hyperplasia. However, only type II cells appear to progress to adenocarcinoma.

Lung-cancer chemoprevention by induction of synthetic lethality in mutant KRAS premalignant cells in vitro and in vivo

Lung cancer is the leading cause of cancer death in both men and women in the United States, with a low 5-year survival rate despite improved treatment strategies. These data underscore the great need for effective chemoprevention of this cancer. Mutations and activation of KRAS occur frequently in, and are thought to be a primary driver of the development of, non-small cell lung cancers (NSCLC) of the adenocarcinoma subtype. In this study, we developed a new approach for the chemoprevention of NSCLC involving specific targeting of apoptosis in mutant KRAS cells. This approach is based on a synthetic lethal interaction among TNF-related apoptosis-inducing ligand (TRAIL), the second mitochondria-derived activator of caspase Smac/DIABLO (Smac), and KRAS. Mutational activation of KRAS modulated the expression of TRAIL receptors by upregulating death receptors and downregulating decoy receptors. Furthermore, oncogenic KRAS repressed cellular FADD-like interleukin 1β-converting enzyme (FLICE)-like inhibitory protein (c-FLIP) expression through activation of Erk/mitogen-activated protein kinase (MAPK)-mediated activation of c-Myc. Smac overcame KRAS-induced cell-survival signaling by antagonizing X-linked inhibitor of apoptosis protein (XIAP). Therefore, the combination of TRAIL and a small molecule mimic of Smac induced apoptosis specifically in mutant KRAS cells without harming normal cells. We further showed that short-term, intermittent in vivo treatment with TRAIL and Smac mimic induced apoptosis in tumor cells and reduced tumor burden in a murine model of KRAS-induced lung cancer. These results reflect the potential benefit of a selective therapeutic approach for the chemoprevention of NSCLC.

Smoking history and lung carcinoma: KRAS mutation is an early hit in lung adenocarcinoma development

BACKGROUND

In a European multicenter prospective study patients with lung cancer were interviewed for smoking history and biological samples centrally collected. The aim of this study was to compare KRAS mutation analysis with smoking status at the time of diagnosis.

METHODS

A nested case-study was performed on 233 non-small cell lung carcinomas. Cases were selected on the basis of progressive disease or disease-free post surgery based on specific criteria. KRAS mutation analysis was performed with the point-EXACCT method.

RESULTS

KRAS mutations were found in 39 adenocarcinomas and 1 squamous cell carcinoma in the 233 NSCLC. The median quitting smoking time (QST) for patients with and without KRAS mutations was 9 years, interquartile range [IQR 16-38] and 3 years, IQR [13-50], respectively (p=0.039). No difference was found for age at initiation of smoking, duration of smoking, average tobacco consumption, and smoking status at the time of diagnosis.

CONCLUSION

The QST was longer for patients with KRAS mutations, supporting the notion that the presence of a KRAS mutation is a dominant early effect, supporting its role as a driver oncogen.

Predictive advantage of a cell type classification for pulmonary adenocarcinoma coupled with data for p53, K-ras and EGFR alterations

We analyzed relationships between histological subtypes of pulmonary adenocarcinomas and three gene alterations (p53, K-ras, and epidermal growth factor receptor gene), or thyroid transcription factor-1 (TTF-1) expression, and also studied prognoses by the subtypes, with or without combined multiple gene mutation status. Our purpose was to clearly determine pathogenesis, along with the best predictive value for biology and therapy-related traits. A total of 223 consecutively resected pulmonary adenocarcinomas were sub-classified using either the World Health Organization (WHO) or our five-cell type (FCT) classification system (hobnail, columnar/cuboidal, mixed, polygonal/oval, and goblet cell types). DNAs extracted from frozen samples of the adenocarcinomas were examined for gene alterations, and TTF-1 expressions were determined using immunohistochemistry. Next, relationships among the various data and clinicopathological factors were analyzed. The most striking result was: while almost 70% of adenocarcinomas were sub-classified as a mixed subtype by WHO, the FCT classified many of them as other cell subtypes. The FCT closely reflected differences in etiological factors, cellular lineages, and frequencies of gene mutations; and whether the data from combined gene mutations were used or not, differences among the cell types in postoperative survivals appeared. In contrast, subtypes of WHO did not show any association with the gene alteration or prognosis, and the FCT more suitably indicated sensitivity to gefitinib therapy than did WHO. The FCT combined with multiple gene mutation status appears to be useful in indicating pathogenesis and predicting the biological nature of pulmonary adenocarcinomas, and it could facilitate development of new therapies for each subtype.

Small peripheral lung adenocarcinoma: clinicopathological features and surgical treatment

The clinical use of high-resolution computed tomography (CT) has greatly advanced diagnosis of small peripheral lesions of the lung. In CT images, these lesions often exhibit ground-glass opacity (GGO). Ground-glass opacity is typical of noninvasive bronchioloalveolar carcinoma (BAC), which is characterized by a lepidic pattern of cells that line the alveoli but do not invade neighboring structures. Bronchioloalveolar carcinoma is classified as a subset of lung adenocarcinoma, but has distinct clinical and pathological features and a favorable prognosis. Most small peripheral lung lesions, including BAC, probably originate in the epithelium of the peripheral airway. As with other subsets of non-small cell lung cancer, surgical resection is a potentially curative treatment. However, it is questionable whether a lobectomy is necessary for small lesions that exhibit GGO, particularly when they are <1 cm in diameter. Although several Japanese investigators have suggested that a limited resection, including a wedge resection and a segmentectomy without nodal dissection, is an appropriate treatment for small lung adenocarcinomas, this approach should be validated by clinical trials.

Epistatic interactions govern chemically-induced lung tumor susceptibility and Kras mutation site in murine C57BL/6J-ChrA/J chromosome substitution strains

Cancer susceptibility results from interactions between sensitivity and resistance alleles. We employed murine chromosome substitution strains to study how resistance alleles affected sensitive alleles during chemically-induced lung carcinogenesis. The C57BL/6J-Chr#(A/J) strains, constructed by selectively breeding sensitive A/J and resistant C57BL/6J (B6) mice, each contain one pair of A/J chromosomes within an otherwise B6 genome. Pas1, the major locus responsible for this differential strain response to urethane carcinogenesis, resides on Chr 6, but C57BL/6J-Chr6(A/J) mice (hereafter CSS-6) developed few tumors following a single urethane injection, which demonstrates epistatic interactions with other B6 alleles. CSS6 mice developed dozens of lung tumors after chronic urethane exposure, however, indicating that these epistatic interactions could be overcome by repeated carcinogen administration. Unlike A/J, but similar to B6 mice, CSS6 mice were resistant to lung carcinogenesis induced by 3-methylcholanthrene (MCA). Tumor multiplicity increased if BHT administration followed urethane exposure, showing that a Chr 6 gene(s) regulates sensitivity to chemically-induced tumor promotion. Unlike A/J tumors (predominantly codon 61 A-->T transversions), Kras mutations in tumors induced by urethane in CSS-6 mice were similar to B6 tumors (codon 61 A-->G transitions). DNA repair genes not located on Chr 6 may determine the nature of Kras mutations. CSS-6 mice are a valuable resource for testing the ability of candidate genes to modulate lung carcinogenesis.

Novel Ras pathway inhibitor induces apoptosis and growth inhibition of K-ras-mutated cancer cells in vitro and in vivo

MT477 is a novel quinoline with potential activity in Ras-mutated cancers. In this study, MT477 preferentially inhibited the proliferation of K-ras-mutated human pulmonary (A549) and pancreatic (MiaPaCa-2) adenocarcinoma cell lines, compared with a non-Ras-mutated human lung squamous carcinoma cell line (H226) and normal human lung fibroblasts. MT477 treatment induced apoptosis in A549 cells and was associated with caspase-3 activation. MT477 also induced sub-G1 cell-cycle arrest in A549 cells. Although we found that MT477 partially inhibited protein kinase C (PKC), it inhibited Ras directly followed in time by inhibition of 2 Ras downstream molecules, Erk1/2 and Ral. MT477 also caused a reorganization of the actin cytoskeleton and formation of filopodias in A549 cells; this event may lead to decreased migration and invasion of tumor cells. In a xenograft mouse model, A549 tumor growth was inhibited significantly by MT477 at a dose of 1 mg/kg (P < 0.05 vs vehicle control). Taken together, these results support the conclusion that MT477 acts as a direct Ras inhibitor. This quinoline, therefore, could potentially be active in Ras-mutated cancers and could be developed extensively as an anticancer molecule with this in mind.

Clinical, pathological and thin-section CT features of persistent multiple ground-glass opacity nodules: comparison with solitary ground-glass opacity nodule

PURPOSE

To retrospectively compare the clinical, pathological, and thin-section CT features of persistent multiple ground-glass opacity (GGO) nodules with those of solitary GGO nodules.

MATERIALS AND METHODS

Histopathologic specimens were obtained from 193 GGO nodules in 136 patients (87 women, 49 men; mean age, 57; age range 33-81). The clinical data, pathologic findings, and thin-section CT features of multiple and solitary GGO nodules were compared by using t-test or Fisher's exact test.

RESULTS

Multiple GGO nodules (n=105) included atypical adenomatous hyperplasia (AAH) (n=31), bronchioloalveolar carcinoma (BAC) (n=33), adenocarcinoma (n=34) and focal interstitial fibrosis (n=7). Solitary GGO nodules included AAH (n=8), BAC (n=15), adenocarcinoma (n=55) and focal interstitial fibrosis (n=10). AAH (P=.001) and BAC (P=.029) were more frequent in multiple GGO nodules, whereas adenocarcinoma (P<.001) was more frequent in solitary GGO nodules. Female sex (P<.001), nonsmoker (P=.012) and multiple primary lung cancers (P<.001) were more frequent for multiple GGO nodules, which were smaller (12 mm+/-7.9) than solitary GGO nodules (17 mm+/-8.1) (P<.001). Air-bronchogram (P=.019), bubble-lucency (P=.004), and pleural retraction (P<.001) were more frequent in solitary GGO nodules. There was no postoperative recurrence except for one patient with multiple GGO nodules and one with solitary GGO nodule.

CONCLUSION

Clinical, pathological, and thin-section CT features of persistent multiple GGO nodules were found to differ from those of solitary GGO nodules. Nevertheless, the two nodule types can probably be followed up and managed in a similar manner because their prognoses were found to be similar.

Pathologic and molecular features of screening low-dose computed tomography (LDCT)-detected lung cancer: a baseline and 2-year repeat study

Detailed studies on the pathologic and molecular features of low-dose computed tomography (LDCT)-detected carcinomas and comparison with unscreened tumors are still lacking. We evaluated the histopathologic features of 89 LDCT-detected lung cancers resected between 2004 and 2006. These tumors occurred within a cohort of 5202 volunteers undergoing annual LDCT, aged > or =50 years, and with a minimum 20 pack-year index. In adenocarcinomas, central scar diameter, invasion foci size and K-ras mutations were also assessed. The results were compared with those of 89 consecutive lung carcinomas matched for confounding factors (sex, smoking habit), selected from group of 363 consecutive clinically worked-up lung cancer, surgically resected in the same period and at the same Institution. The tumors were diagnosed in 63 males and 26 females (range 50-79 years), 55 of which diagnosed at the baseline (1.05%) and 34 (including 10 repeat cancers) operated after work-up during the second year (0.72%). LDCT-detected tumors showed high resectability rate (89%), earlier stage (63%) and prevalence of adenocarcinoma nodules (72%), most often of the mixed subtype, in comparison with unscreened tumors. A similar prevalence of K-ras mutations was found in both screened and unscreened adenocarcinomas. Repeat cancers were found in 10 screened patients, and were predominantly stage I adenocarcinomas of mixed subtype exhibiting smaller dimension but greater central scar diameter and stromal invasion size in comparison with the other second-year, slower-growing adenocarcinomas. Multiple tumor nodules were identified in 10 patients exclusively at the baseline, were mostly mixed adenocarcinomas and differed in their K-ras mutation profile. Screening-detected lung cancers shared most of the histologic features of fully malignant tumors, in addition to a similar prevalence of K-ras mutations, despite their earlier detection and less advanced clinical stage. Repeat cancers are potentially aggressive tumors. K-ras mutation analysis supports the impression that multifocal tumors at baseline are separate synchronous primaries.

Mutation of the epidermal growth factor receptor gene in the development of adenocarcinoma of the lung

Recently, a mutation of the epidermal growth factor receptor (EGFR) gene has been reported to be implicated in the development of pulmonary adenocarcinoma. However, the involvement of the mutation in atypical adenomatous hyperplasia (AAH) and multiple adenocarcinomas still remains unclear. We herein examined the EGFR mutations in 9 AAH and 31 adenocarcinoma lesions obtained from 30 Japanese patients. Nine patients had synchronous or metachronous multiple adenocarcinomas and/or AAH. Mutations in exons 18-21 of EGFR gene were analysed using polymerase chain reaction and direct sequence methods. EGFR mutations were detected in 4 (44%) of 9 AAH and in 7 (23%) of 31 adenocarcinomas. A gefitinib-resistant point mutation (T790M) in exon 20 without gefitinib treatment was detected in 1 AAH and 1 adenocarcinoma. The patient with T790M mutated AAH, which also had an exon 19 mutation of D761Y, had synchronous adenocarcinoma, which had only an exon 19 mutation of D761Y. The other exon 19 mutations were all in-frame deletions. In the two patients with synchronous AAH and adenocarcinoma, AAH had mutations at exon 19 although adenocarcinoma did not have any mutations. In the patient with synchronous 2 adenocarcinomas, each had different mutations (exons 19 and 21). In two patients with double adenocarcinomas, 1 adenocarcinoma harbored exon 21 mutations, while the other demonstrated no mutations. Although EGFR mutations appeared to be partially associated with the early steps of adenocarcinoma development, such mutations may possibly occur randomly even in multiple lesions in a single patient.

Epidermal growth factor receptor gene mutations in atypical adenomatous hyperplasias of the lung

Activating epidermal growth factor receptor (EGFR) gene mutations are frequently detected in lung adenocarcinomas, especially adenocarcinomas with a nonmucinous bronchioloalveolar carcinoma component. EGFR-mutated lung adenocarcinomas respond well to EGFR tyrosine kinase inhibitors. We previously found that most (88%) pure nonmucinous bronchioloalveolar carcinomas (adenocarcinoma in situ) already harbor EGFR mutations, indicating that the mutations are an early genetic event in the pathogenesis. We examined 54 atypical adenomatous hyperplasias, precursor lesions of lung adenocarcinomas, obtained from 28 Japanese patients for the hotspot mutations of EGFR exons 19 and 21 and K-ras codon 12. EGFR mutations were observed in 17 of the 54 (32%) atypical adenomatous hyperplasias examined: Ten and seven atypical adenomatous hyperplasias had deletion mutations at exon 19 or point mutations (L858R) at exon 21, respectively. We did not observe apparent histological differences between atypical adenomatous hyperplasias with and without EGFR mutations. K-ras mutation (G12S) was detected in only one atypical adenomatous hyperplasia. As EGFR mutational frequency of atypical adenomatous hyperplasias was much lower than that of nonmucinous bronchioloalveolar carcinomas, we surmise that EGFR-mutated atypical adenomatous hyperplasias, but not atypical adenomatous hyperplasias with wild-type EGFR, are likely to progress to nonmucinous bronchioloalveolar carcinomas.

Controversy about Small Peripheral Lung Adenocarcinomas: How Should We Manage Them?

In recent years, the clinical use of high-resolution computed tomography has greatly advanced the diagnosis of small lesions of the peripheral lung. Such small lesions are often associated with ground-glass opacity in computed tomography findings. The noninvasive bronchioloalveolar carcinoma component with a replacement growth pattern of alveolar lining cells manifests as ground-glass opacity. Bronchioloalveolar carcinoma is classified as a subset of lung adenocarcinoma, but has a distinct clinical presentation, tumor biology, and favorable prognosis. Most small peripheral lung lesions including bronchioloalveolar carcinoma putatively originate from the peripheral airway epithelium, in which the epidermal growth factor receptor gene is frequently mutated. As with other subsets of non-small cell lung cancer, surgical resection is a potentially curative treatment. For the ground-glass opacity type of tiny lesions, particularly those less than 1 cm in their greatest dimension, the question has been raised whether lobectomy is really needed. Although several authors in Japan suggest the suitability of limited resection including segmentectomy and wedge resection without any nodal dissections for these small lung adenocarcinomas, this procedure should be validated in future clinical trials.

WWOX expression in different histologic types and subtypes of non-small cell lung cancer

PURPOSE

Non-small cell lung cancer (NSCLC) has heterogeneous histopathologic classification and clinical behavior and very low survival rate. WWOX (WW domain-containing oxidoreductase) is a tumor suppressor gene, and its expression is altered in several cancers. The purpose of this study is to better define the role of WWOX in NSCLC tumorigenesis and progression by determining its pathogenetic and prognostic significance.

EXPERIMENTAL DESIGN

WWOX protein expression was evaluated by immunohistochemistry in 170 patients with NSCLC (101 squamous cell carcinomas, 66 adenocarcinomas, 3 large cell carcinomas) and was correlated with histopathologic (histotype, subtype, grade, tumor-node-metastasis, stage, index of cell proliferation Ki67/MIB1) and clinical (age, gender, local recurrences, distant metastases, overall survival, and disease-free survival) characteristics.

RESULTS

WWOX expression was absent/reduced in 84.9% of NSCLCs, whereas it was normal in 80.5% of adjacent normal lung tissues. WWOX expression was strongly associated with tumor histology (P=1.1x10(-5)) and histologic grade (P=0.0081): the percentage of cases with absent/strongly reduced WWOX expression was higher in squamous cell carcinomas and in poorly differentiated tumors. Regarding adenocarcinoma, bronchioloalveolar pattern showed normal WWOX expression in 62.5% of the cases, whereas in solid and acinar patterns, a prevalence of cases with absent/very low WWOX expression was observed (79.2% and 50%, respectively). Finally, weak WWOX staining intensity was related to the high index of cell proliferation (P=0.0012).

CONCLUSIONS

Our results suggest that the loss of WWOX expression plays different roles in tumorigenesis of distinct histotypes and subtypes of NSCLC and is related to high aggressiveness (G3; high proliferating activity) of tumors.

Genetic relationship among atypical adenomatous hyperplasia, bronchioloalveolar carcinoma and adenocarcinoma of the lung

Atypical adenomatous hyperplasia (AAH) has been recently defined by WHO as a small lesion, not exceeding 5mm in major axis, composed of slightly enlarged alveolar septa lined by pneumocytes with plump, atypical nuclei. AAH is frequently found in tissue surrounding lung adenocarcinoma and is considered a precursor of this subtype of lung cancer by many Authors. However, the genetic relationship between adenocarcinoma and the associated foci of AAH is not well defined. In particular, it is not clear whether multiple foci of AAH and of adenocarcinoma in the same patients are clonally related to each other or represent independent neoplastic foci. To clarify if AAH and the associated cancer are clonally related, we evaluated the genetic distance between these two lesions in 16 patients, using direct sequencing of mitochondrial DNA (D-loop region). Furthermore, LOH analysis for 7 microsatellites (D3S1478 at 3p21, D3S1300 at 3p14.2, D9S942 at 9p21, D5S346 at 5q21, D17S261 at 17p13.1, D18S46 at 18q21, D19S246 at 19q13.2) was also performed. Our results indicate that, in at least 9 out of 13 informative cases (69.2%), AAH and the associated cancer were not clonally related as they showed a different mutation pattern in the mitochondrial D-loop region. These findings were also in agreement with the LOH data which showed losses in different loci in at least three cases. On the contrary an identical LOH pattern between BAC and AAH was found in one case. Similar but not identical LOH pattern between AAH and related tumors was found in other three cases. Therefore, our results suggest that AAH and the associated cancer are genetically independent in agreement with the concept of cancerization field. Less frequently AAH foci could represent an early spread of cells from the main tumor, rather than a precursor lesion.

Overview of the molecular carcinogenesis of mouse lung tumor models of human lung cancer

Lung cancer is the leading cause of cancer death worldwide, and the need to develop better diagnostic techniques and therapies is urgent. Mouse models have been utilized for studying carcinogenesis of human lung cancers, and many of the major genetic alterations detected in human lung cancers have also been identified in mouse lung tumors. The importance of mouse models for understanding human lung carcinogenic processes and in developing early diagnostic techniques, preventive measures and therapies cannot be overstated. In this report, the major known molecular alterations in lung tumorigenesis of mice are reviewed and compared to those in humans.

Growth regulation via insulin-like growth factor binding protein-4 and -2 in association with mutant K-ras in lung epithelia

Gain-of-function point mutations in K-ras affect early events in pulmonary bronchioloalveolar carcinoma. We investigated altered mRNA expression on K-Ras activation in human peripheral lung epithelial cells (HPL1A) using oligonucleotide microarrays. Mutated K-Ras stably expressed in HPL1A accelerated cell growth and induced the expression of insulin-like growth factor (IGF)-binding protein (IGFBP)-4 and IGFBP-2, which modulate cell growth via IGF. Other lung epithelial cell lines (NHBE and HPL1D) revealed the same phenomena as HPL1A by mutated K-ras transgene. Lung cancer cell growth was also accelerated by mutated K-ras gene transduction, whereas IGFBP-4/2 induction was weaker compared with mutated K-Ras-expressing lung epithelial cells. To understand the differences in IGFBP-4/2 inducibility via K-Ras-activated signaling between nonneoplastic lung epithelia and lung carcinoma, we addressed the mechanisms of IGFBP-4/2 transcriptional activation. Our results revealed that Egr-1, which is induced on activation of Ras-mitogen-activated protein kinase signaling, is crucial for transactivation of IGFBP-4/2. Furthermore, IGFBP-4 and IGFBP-2 promoters were often hypermethylated in lung carcinoma, yielding low basal expression/weak induction of IGFBP-4/2. These findings suggest that continuous K-Ras activation accelerates cell growth and evokes a feedback system through IGFBP-4/2 to prevent excessive growth. Moreover, this growth regulation is disrupted in lung cancers because of promoter hypermethylation of IGFBP-4/2 genes.

Genetic alterations in cancer knowledge system: analysis of gene mutations in mouse and human liver and lung tumors

Mutational incidence and spectra for genes examined in both human and mouse lung and liver tumors were analyzed using the National Institute of Environmental Health Sciences (NIEHS) Genetic Alterations in Cancer (GAC) knowledge system. GAC is a publicly available, web-based system for evaluating data obtained from peer-reviewed studies of genetic changes in tumors associated with exposure to chemical, physical, or biological agents, as well as spontaneous tumors. In mice, mutations in Kras2 and Hras-1 were the most common events reported for lung and liver tumors, respectively, whether chemically induced or spontaneous. There was a significant difference in Kras2 mutation incidence for spontaneous versus induced mouse lung tumors and in Hras-1 mutation incidence and spectrum for spontaneous versus induced mouse liver tumors. The major gene changes reported for human lung and liver tumors were in KRAS2 (lung only) and TP53. The KRAS2 mutation incidence was similar for spontaneous and asbestos-induced human lung tumors, while the TP53 mutation incidence differed significantly. Aflatoxin B1, hepatitis B virus, hepatitis C virus, and vinyl chloride all caused TP53 mutations in human liver tumors, but the mutation spectrum for each agent differed. The incidence of KRAS2 mutations in human compared to mouse lung tumors differed significantly, as did the incidence of Hras and p53 gene mutations in human compared to mouse liver tumors. Differences observed in the mutation spectra for agent-induced compared to spontaneous tumors and similarities in spectra for structurally similar agents support the concept that mutation spectra can serve as a "fingerprint" of exposure based on chemical structure.

Mutations of the epidermal growth factor receptor gene in atypical adenomatous hyperplasia and bronchioloalveolar carcinoma of the lung

A hypothesis of multistep carcinogenesis of lung adenocarcinoma from atypical adenomatous hyperplasia (AAH) to invasive adenocarcinoma through bronchioloalveolar carcinoma (BAC) has been proposed. However, the genetic alterations that play a role during these processes are not yet clear. Recently, somatic mutations of the epidermal growth factor receptor (EGFR) gene were found in lung adenocarcinoma. We examined the status of EGFR mutations in AAH and BAC to elucidate the role they play during multistage of lung adenocarcinoma. We found somatic EGFR mutations in 3% (1/35) of AAH, 10.8% (4/37) of BAC and 41.9% (13/31) of invasive adenocarcinoma. Sixteen of 18 EGFR mutations were found in exon 19 and two were in exon 21. Among the 16 EGFR mutations in exon 19, 13 were deletions of 15bp and one was an insertion/duplication of 18bp. Mutations of the K-ras gene were detected in 26.7% (8/30) of AAH, 16.7% (5/30) of BAC and 10% (3/30) of invasive adenocarcinoma. None of the tumors with EGFR mutations had K-ras mutation simultaneously. Patients who had invasive adenocarcinoma with EGFR mutations were younger than those without mutations (60.6 versus 67.4 years, p=0.03). These results suggest that tumors with EGFR mutations may progress more rapidly and develop into invasive cancer faster than those without mutations. Alternatively it is also possible that some invasive adenocarcinomas with EGFR mutations may not follow the AAH-adenocarcinoma sequence. We analyzed 24 patients with multiple lung lesions and 13 patients had at least one lesion that had either an EGFR or K-ras mutation. In all cases each lesion had a different mutation status. This finding suggests that the genetic alterations responsible for the development of lung adenocarcinoma occur randomly even under exposure to the same carcinogen.

TP53 and KRAS mutation load and types in lung cancers in relation to tobacco smoke: distinct patterns in never, former, and current smokers

TP53 mutations are common in lung cancers of smokers, with high prevalence of G:C-to-T:A transversions generally interpreted as mutagen fingerprints of tobacco smoke. In this study, TP53 (exons 5-9) and KRAS (codon 12) were analyzed in primary lung tumors of never (n = 40), former (n = 27), and current smokers (n = 64; mainly heavy smokers). Expression of p53, cyclooxygenase-2 (Cox-2), and nitrotyrosine (N-Tyr), a marker of protein damage by nitric oxide, were analyzed by immunohistochemistry. TP53 mutations were detected in 47.5% never, 55.6% former, and 77.4% current smokers. The relative risk for mutation increased with tobacco consumption (P(linear trend) < 0.0001). G:C-to-T:A transversions (P = 0.06, current versus never smokers) and A:T-to-G:C transitions (P = 0.03, former versus never smokers) were consistently associated with smoking. In contrast, G:C-to-A:T transitions were associated with never smoking (P = 0.02). About half of mutations in current smokers fell within a particular domain of p53 protein, suggesting a common structural effect. KRAS mutations, detected in 20 of 131 (15.3%) cases, were rare in squamous cell carcinoma compared with adenocarcinoma [relative risk (RR), 0.2; 95% confidence interval (95% CI), 0.07-1] and were more frequent in former smokers than in other categories. No significant differences in Cox-2 expression were found between ever and never smokers. However, high levels of N-Tyr were more common in never than ever smokers (RR, 10; 95% CI, 1.6-50). These results support the notion that lung tumorigenesis proceeds through different molecular mechanisms according to smoking status. In never smokers, accumulation of N-Tyr suggests an etiology involving severe inflammation.

Difference of caveolin-1 expression pattern in human lung neoplastic tissue. Atypical adenomatous hyperplasia, adenocarcinoma and squamous cell carcinoma

Caveolin-1 has been implicated in cellular transformation and tumorigenesis. We assessed lung cancer specimens for caveolin-1 expression immunohistochemistry. A majority of the cell types in the lung and the bronchial epithelium normally exhibited positive staining for caveolin-1. In adenocarcinomas (ADs) of positive staining for caveolin-1, pT1 tumors exhibited significantly higher staining than pT2-pT4 tumors (P=0.0240). In squamous cell carcinomas (SCCs), pT1-pT2 tumors expressed significantly lower expression levels than pT3-pT4 tumors (P=0.0175). In AD, loss of caveolin-1 may be essential for tumor extension and dedifferentiation. In contrast, caveolin-1 overexpression may be correlated with tumor extension in SCC.

Thyroid transcription factor 1 in pulmonary adenocarcinoma

AIMS

To discover whether variations in thyroid transcription factor 1 (TTF-1) staining in different subtypes and patterns of pulmonary adenocarcinoma are related to the putative origin of the tumour. In addition, to confirm the specificity of TTF-1 for pulmonary (as opposed to other sites) adenocarcinoma, to examine the possible prognostic relevance of TTF-1 positivity in lung cancer, and to review this laboratory's experience of TTF-1 in diagnostic practice.

MATERIALS/METHODS

In total, 128 primary lung adenocarcinomas, 106 primary non-pulmonary adenocarcinomas, and 37 pulmonary non-adenocarcinoma tumours were studied. In addition, 100 cases where TTF-1 was used in routine surgical pathology practice were investigated. Immunoperoxidase staining was performed on formalin fixed, paraffin wax embedded sections using anti-TTF-1 antibody. Staining was evaluated semiquantitatively using the frequency and intensity of nuclear positivity.

RESULTS

None of the 106 non-pulmonary adenocarcinomas expressed TTF-1 and only three of the 37 non-adenocarcinoma lung cancers, all neuroendocrine carcinomas, were positive. Of the pulmonary adenocarcinomas, 75% were strongly positive for TTF-1. Mucinous (two of six) and poorly differentiated adenocarcinomas (four of 10) were less likely to stain. Of the peripheral adenocarcinomas, 33 of 37 were positive, whereas only seven of 14 of those of bronchial origin stained strongly. Atypical adenomatous hyperplasia strongly expressed TTF-1. No "false positives" were encountered in the 100 routine diagnostic cases.

CONCLUSION

Positive TTF-1 staining is useful in the differential diagnosis of pulmonary adenocarcinomas. TTF-1 may be a lineage marker for tumours arising from the peripheral airway or alveolar epithelium and has no prognostic relevance.

Molecular classification and molecular genetics of human lung cancers

Recent advances in the molecular classification of lung carcinomas and the identification of causative genetic alterations will likely lead to improvements in the diagnosis and treatment of patients with lung cancer. It is now possible to identify gene expression profiles that associate with patient outcome in lung carcinomas, in particular adenocarcinoma. Furthermore, patient survival has been shown to correlate with lung cancer oligonucleotide microarray expression profiles. Large-scale microarray technology may allow for the identification of useful biomarkers for early cancer detection. Oligonucleotide microarray data can be optimized by relating them to protein expression levels in tissue microarrays, by annotation with mutational data, and with results of testing for post-translational modification of cellular proteins. These data may be useful in tailoring chemotherapeutic protocols to individual tumors and identifying new targets for therapeutic intervention.

K-ras gene mutation enhances motility of immortalized airway cells and lung adenocarcinoma cells via Akt activation: possible contribution to non-invasive expansion of lung adenocarcinoma

Point mutations of the K-ras gene, which are found in 10 to 30% of lung adenocarcinomas, are regarded as being an early event during the carcinogenesis. Autonomous vigorous motility of neoplastic cells, as well as growth and survival advantages, are considered to be necessary for cancer development and progression. The present study describes the contributions of the K-ras gene mutation and its downstream pathway via phosphatidylinositol 3-OH kinase (PI3K)-Akt to the cell motility in an immortalized human peripheral airway epithelial cell (HPL1D) and lung adenocarcinoma cells (A549, H820, TKB6, and TKB14). We have also evaluated the relationship between pathological events and the K-ras-Akt pathway using surgically resected lung tumors. The HPL1D cells transfected with the mutated K-ras gene (HPL-V12) showed a significant increase in cell motility compared to those transfected with empty vector (HPL-E) or wild-type K-ras gene (HPL-K). The enhanced motility in the HPL-V12 cells was markedly reduced by either treatment with inhibitors of ras, PI3K, and/or MEK, or by transfection with the dominant-negative mutant Akt (dnAkt). The lung adenocarcinoma cells bearing the K-ras gene mutation (A549 and H820) showed consistently higher levels of cell motilities than those without the mutation (TKB6 and TKB14), and the motility of A549 and H820 cells were significantly inhibited by dnAkt transfection. These results suggest that the K-ras gene mutation could enhance the motility of neoplastic cells through a pathway involving PI3K-Akt. Actually, among the surgically resected lung tumors, the adenocarcinomas with the K-ras gene mutation tended to show a higher frequency and intensity of immunoreactivity for phosphorylated Akt (p-ser473Akt) than those without the mutation, supporting the in vitro observation that the mutated K-ras can activate the PI3K-Akt pathway. Immunoreactivity for p-ser473Akt was also seen in the pre-malignant and early lesions at a frequency similar to that in the advanced lung adenocarcinomas,. No correlation was seen between p-ser473Akt immunoreactivity and lymphatic/organ metastasis or prognosis. These results taken together suggest that the K-ras-Akt pathway might facilitate the motility of neoplastic cells during the early period of carcinogenesis in lung adenocarcinomas, and may contribute to their non-invasive expansion along the alveolar septa, rather than invasion or metastasis.

Lung adenocarcinoma associated with atypical adenomatous hyperplasia. A clinicopathological study with special reference to smoking and cancer multiplicity

Atypical adenomatous hyperplasia (AAH) of the lung has been proposed as a possible precursor lesion of adenocarcinoma of the lung. In the present study, we sought to clarify the clinicopathological characteristics of lung adenocarcinoma cases associated with AAH, with special reference to tobacco smoking and the presence of multiple primary carcinomas of pulmonary and extrapulmonary organs. We examined 123 surgically resected lung adenocarcinomas and conducted histopathological diagnoses for AAH and multiple primary pulmonary carcinomas. Clinicopathological characteristics such as age, sex, smoking index, survival, and the presence of extrapulmonary primary carcinomas were obtained from clinical records, and the associations among these factors were examined statistically. Sixteen lung adenocarcinoma patients had accompanying AAH (the AAH group) and 107 cases did not (the NAAH group). The incidence of primary carcinomas in extrapulmonary organs was higher in the AAH group (37.5%; 6/16) than in the NAAH group (12.5%; 13/107) (P = 0.01). Multiple primary lung cancers tended to be more frequent in the AAH group, but the difference was not statistically significant (P = 0.07). Although there was no difference in tobacco smoking between the two groups, all eight cases with multiple primary lung carcinomas were smokers. Furthermore, multiple primary lung carcinomas were found more frequently in smokers of the AAH group (37.5%; 3/8) than in the smokers of the NAAH group (7.2%; 5/69) (P = 0.04). The results suggested that constitutional or genetic factors might predispose patients to the development of AAH together with extrapulmonary primary carcinomas, and that smoking might contribute to the development of multiple primary lung adenocarcinomas, especially in patients with pre-existing AAH.

The molecular basis of lung cancer: molecular abnormalities and therapeutic implications

Lung cancer is the number one cause of cancer-related death in the western world. Its incidence is highly correlated with cigarette smoking, and about 10% of long-term smokers will eventually be diagnosed with lung cancer, underscoring the need for strengthened anti-tobacco policies. Among the 10% of patients who develop lung cancer without a smoking history, the environmental or inherited causes of lung cancer are usually unclear. There is no validated screening method for lung cancer even in high-risk populations and the overall five-year survival has not changed significantly in the last 20 years. However, major progress has been made in the understanding of the disease and we are beginning to see this knowledge translated into the clinic.

In this review, we will summarize the current state of knowledge regarding the cascade of events associated with lung cancer development. From subclinical DNA damage to overt invasive disease, the mechanisms leading to clinically and molecularly heterogeneous tumors are being unraveled. These lesions allow cells to escape the normal regulation of cell division, apoptosis and invasion. While all subtypes of non-small cell lung cancer have historically been treated the same, stage-for-stage, recent technological advances have allowed a better understanding of the molecular classification of the disease and provide hypotheses for molecular early detection and targeted therapeutic strategies.

Genetic alterations of multiple tumor suppressors and oncogenes in the carcinogenesis and progression of lung cancer

Lung cancer has become the leading cause of cancer death in many economically well-developed countries. Recent molecular biological studies have revealed that overt lung cancers frequently develop through sequential morphological steps, with the accumulation of multiple genetic and epigenetic alterations affecting both tumor suppressor genes and dominant oncogenes. Cell cycle progression needs to be properly regulated, while cells have built-in complex and minute mechanisms such as cell cycle checkpoints to maintain genomic integrity. Genes in the p16INK4A-RB and p14ARF-p53 pathways appear to be a major target for genetic alterations involved in the pathogenesis of lung cancer. Several oncogenes are also known to be altered in lung cancer, leading to the stimulation of autocrine/paracrine loops and activation of multiple signaling pathways. It is widely acknowledged that carcinogens in cigarette smoke are deeply involved in these multiple genetic alterations, mainly through the formation of DNA adducts. A current understanding of the molecular mechanisms of lung cancer pathogenesis and progression is presented in relation to cigarette smoking, an absolute major risk factor for lung cancer development, by reviewing genetic alterations of various tumor suppressor genes and oncogenes thus far identified in lung cancer, with brief summaries of their functions and regulation.

Lung adenocarcinoma with bronchioloalveolar carcinoma component is frequently associated with foci of high-grade atypical adenomatous hyperplasia

We assessed the occurrence of atypical adenomatous hyperplasia (AAH) in whole lung lobes with primary cancer lesions. Following surgical resection, tissue specimens were sliced to a thickness of 4 mm (3,641 specimens from 61 cases; mean = 59.7 specimens per case). A total of 119 AAH foci were found and an association was evident in 25 (57%) of 44 adenocarcinomas, 3 (30%) of 10 squamous cell carcinomas, and 2 (29%) of 7 other lung cancers. Histologic evaluation showed that 108 AAH foci were categorized as low-grade and the other 11 as high-grade AAH. These 11 foci of high-grade AAH were present in 7 patients with adenocarcinoma, and in 1 patient there was a synchronous double primary lung adenocarcinoma. High-grade AAH was closely associated with bronchioloalveolar carcinoma (BAC) type adenocarcinoma, and low-grade AAH with non-BAC adenocarcinoma. The mean +/- SD Ki-67 labeling index in high-grade AAH (3.5%+/-2.9%) was significantly higher than for the low-grade index (1.4%+/-1.6%). We propose that foci of high- but not low-grade AAH may be potential precursor lesions of lung adenocarcinoma, especially with the BAC component.

Molecular biology of lung cancer: clinical implications

This review summarizes the rapidly expanding knowledge of the molecular pathogenesis of lung cancer. It is clear that respiratory epithelial cells require many genetic alterations to become invasive and metastatic cancer. Much more is to be learned, but with modern technology. Clinicians can detect "field cancerized" regions and preneoplastic and malignant cells, therefore offering the opportunity to intercede with biomarker-monitored prevention and early detection efforts. Such molecular screening and detection efforts will likely be coupled to advances in low-dose computed tomographic imaging, positron emission tomography scans, and other imaging modalities. Although this molecular marker approach has great potential, there is not yet a molecular marker validated in large prospective trials that has major independent predictive prognostic value. There is an urgent need for large, adequately powered, carefully designed prospective studies to identify clinically useful new biomarkers. Finally, new therapeutic strategies with genetic manipulation, small molecules, antibodies, vaccines, and, particularly, new drugs targeting specific biologic pathways found to be abnormal in lung provide for future optimism. Researchers need to define their individual value, especially when integrated with standard therapies.

Preneoplastic lesions of the lung

Lung cancer is the leading cause of cancer deaths worldwide. If we can define and detect preneoplastic lesions, we might have a chance of improving survival. The World Health Organization has defined three preneoplastic lesions of the bronchial epithelium: squamous dysplasia/carcinoma in situ; atypical adenomatous hyperplasia; and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia. These lesions are believed to progress to squamous cell carcinoma, adenocarcinoma and carcinoid tumors, respectively. In this review we summarize the data supporting the preneoplastic nature of these lesions, and delve into some of the genetic changes found in atypical adenomatous hyperplasia and squamous dysplasia/carcinoma in situ.

Loss of heterozygosity on chromosomes 9q and 16p in atypical adenomatous hyperplasia concomitant with adenocarcinoma of the lung

Atypical adenomatous hyperplasia (AAH) has recently been implicated as a precursor to lung adenocarcinoma. We previously reported loss of heterozygosity (LOH) in tuberous sclerosis (TSC) gene-associated regions to frequently be observed in lung adenocarcinoma with multiple AAHs. In this study, we analyzed LOH in four microsatellite loci on 9q, including the TSC1 gene-associated region, and four loci on 16p, including the TSC2 gene-associated region, in both 18 AAHs and 17 concomitant lung adenocarcinomas from 11 patients. Seven of 18 (39%) AAHs and 9 of 17 (53%) adenocarcinomas displayed LOH on 9q. Five (28%) AAHs and seven (41%) adenocarcinomas harbored LOH at loci adjacent to the TSC1 gene. Four of 18 (22%) AAHs and 6 of 17 (35%) adenocarcinomas displayed LOH on 16p. One (6%) AAH and five (29%) adenocarcinomas harbored LOH at loci adjacent to the TSC2 gene. These findings may indicate a causal relationship of LOH on 9q and 16p in a fraction of AAH lesions and adenocarcinomas of the lung. Especially, the frequencies of LOH on 9q and at the TSC1 gene-associated region were high. The TSC1 gene or another neighboring tumor suppressor gene on 9q might be involved in an early stage of the pathogenesis of lung adenocarcinoma.

Mouse model for lung tumorigenesis through Cre/lox controlled sporadic activation of the K-Ras oncogene

The onset of human lung cancer occurs through sequential mutations in oncogenes and tumor suppressor genes. Mutations in K-Ras play a prominent role in human non-small cell lung cancer. We have developed a mouse lung tumor model in which K-Ras can be sporadically activated through Cre-lox mediated somatic recombination. Adenoviral mediated delivery of Cre recombinase in lung epithelial cells gave rise to rapid onset of tumorigenesis, yielding pulmonary adenocarcinomas with 100% incidence after a short latency. The lung tumor lesions shared many features with human non-small cell lung cancer. Our data show that sporadic expression of the K-Ras oncogene is sufficient to elicit lung tumorigenesis. Therefore this model has many advantages over conventional transgenic models used thus far.

Atypical adenomatous hyperplasia of the lung: a clinicopathological study of 118 cases including cases with multiple atypical adenomatous hyperplasia

BACKGROUND

Atypical adenomatous hyperplasia (AAH) of the lung is a putative precursor lesion of adenocarcinoma, according to many immunohistochemical and genetical studies, but few clinicopathological studies on a large number of cases have been reported. The aim of this study was to clarify the clinicopathological characteristics of lung cancer patients with AAH lesions.

METHODS

A retrospective study was carried out on 508 consecutive primary lung cancer patients operated on at National Cancer Center Hospital East. The relationship between the number and location of AAH lesions and the clinicopathological features of the lung cancer patients was analysed statistically.

RESULTS

A total of 311 AAH lesions were found in 118 (23.2%) of the 508 cases. AAH lesions were detected in 121 of 572 lobes examined, usually in both upper lobes, and occurred most frequently in patients with adenocarcinoma (OR 2.97; 95% CI 1.82 to 4.85). AAH lesions were more frequently detected in patients with multiple primary carcinomas than in those with a single carcinoma (OR 3.06; 95% CI 1.56 to 6.00). The presence of AAH lesions was not significantly correlated with sex, age, smoking status, familial history of malignancy, or preceding malignancy. Patients with multiple AAH lesions were found to have a significantly higher frequency of preceding malignancies.

CONCLUSIONS

The present study highlights the clinicopathological characteristics of AAH lesions, showing them to be significantly associated with both adenocarcinoma and multiple primary carcinoma of the lung and suggesting common factors in the histogenesis of multiple AAH lesions and preceding malignancy.

Pulmonary preinvasive neoplasia

Advances in molecular biology have increased our knowledge of the biology of preneoplastic lesions in the human lung. The recently published WHO lung tumour classification defines three separate lesions that are regarded as preinvasive neoplasia. These are (1) squamous dysplasia and carcinoma in situ (SD/CIS), (2) atypical adenomatous hyperplasia (AAH), and (3) diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIP-NECH). SD/CIS is graded in four stages (mild, moderate, severe, and CIS), based upon the distribution of atypical cells and mitotic figures. Most airways showing SD/CIS demonstrate a range of grades; many epithelia are hard to assess and the reproducibility of this complex system remains to be established. Detailed criteria are, however, welcome and provide an objective framework on which to compare various molecular changes. Alterations in gene expression and chromosome structure known to be associated with malignant transformation can be demonstrated in CIS, less so in dysplasias, but also in morphologically normal epithelium. The changes might be sequential, and their frequency and number increase with atypia. Less is known of the "risk of progression" of SD/CIS to invasive "central" bronchial carcinoma. It may take between one and 10 years for invasion to occur, yet the lesion(s) may be reversible if carcinogen exposure ceases. AAH may be an important precursor lesion for peripheral "parenchymal" adenocarcinoma of the lung: the "adenoma" in an adenoma-carcinoma sequence. There is good morphological evidence that AAH may progress from low to high grade to bronchioloalveolar carcinoma (BAC; a non-invasive lesion by definition). Invasion then develops within BAC and peripheral lung adenocarcinoma evolves. The molecular events associated with this progression are not well understood and studies are hampered by a lack of clear criteria to distinguish high grade AAH from BAC. Nonetheless, as with SD/CIS, the patterns of expression of tumour associated genes are consistent with neoplastic progression. We have little idea of the incidence of AAH in the normal or "smoking" populations. It is found more frequently in cancer bearing lungs, especially in those with adenocarcinoma, and is more common in women. No data are available on the risk of progression of AAH. DIPNECH is an exceptionally rare lesion associated with the development of multiple carcinoid tumours. Almost nothing is known of its biology. Knowledge of these lesions will be crucial in the design and understanding of lung cancer screening programmes, where it is likely that the morphological and, more importantly perhaps, the molecular characteristics of these lesions will provide useful targets for detection and possibly even treatment.

The association between atypical adenomatous hyperplasia and primary lung cancer

Atypical adenomatous hyperplasia (AAH) has been suggested as the adenoma in an adenoma-carcinoma sequence in the lung periphery. From 1989-1998, we undertook a systematic, prospective search for AAH in lungs resected for cancer. AAH was found in 67 of 554 patients (12. 1%) with primary lung carcinoma (9.2% in male patients and 19.0% in females). AAH was found in lungs bearing adenocarcinoma (23.2%) more frequently than with large cell undifferentiated carcinoma (12.5%) or squamous carcinoma (3.3%). A greater percentage of females with adenocarcinoma had AAH (30.2%) than did males with adenocarcinoma (18.8%). Numbers of AAH ranged from 1-42 per patient and more patients had small numbers of AAH, although 12 patients had 6 or more AAH foci. Larger numbers of AAH tended to be found in adenocarcinoma-bearing lungs. Ten of the 67 patients with AAH and primary lung carcinoma (15%) had multiple primary cancers (range 2-6), all of which were adenocarcinoma. Synchronous cancers were rare in lung tumour-bearing resections without AAH. Patients with AAH show no difference in post-operative survival to those without, for all stages of carcinoma and for Stage I disease alone. This study provides evidence for a strong association between atypical adenomatous hyperplasia and primary lung adenocarcinoma and lends weight to the AAH/adenoma-carcinoma hypothesis.

Aneuploidy of chromosome 7 can be detected in invasive lung cancer and associated premalignant lesions of the lung by fluorescence in situ hybridisation

In the present study the chromosomal status of seven invasive non small cell lung cancer specimens and associated premalignant lesions was investigated. By fluorescence in situ hybridisation (FISH) with centromere specific probes, an increase in the percentage of aneuploid cells from pre-invasive to invasive lesions could be demonstrated (mean 8.5 and 59%, respectively, for chromosome 7). Furthermore, mean chromosome copy numbers were higher in invasive carcinomas as compared to premalignant lesions, indicating polyploidization during tumor development. Increasing evidence suggests that aberrations of chromosome 7 occur early in the development of lung cancer. Whether these aberrations can be used as a biomarker for future neoplastic progression remains to be determined.

Early glandular neoplasia of the lung

Although bronchogenic carcinomas progress through a very well defined sequence of metaplasia, dysplasia and carcinoma in situ, very little is known about the early progression of glandular neoplasms of the lung. In particular, the early precursor lesion from which fully malignant adenocarcinomas arise has effectively eluded recognition, at least until recently. Several lines of evidence now implicate atypical adenomatous hyperplasia (AAH) as an initial morphologic stage in multistep lung tumorigenesis. Despite its small size, AAH can be appreciated at the light microscopic level and characterized at the molecular genetic level. Indeed, the genetic characterization of AAH promises to further our understanding of lung cancer development and might facilitate the design of novel strategies for early detection of lung cancer.

Molecular pathogenesis of lung cancer

Lung cancer is the largest cancer killer of men and women in the united states. In addition to the progress made from antismoking primary prevention measures, new tools to help treat patients with lung cancer are emerging from the rapid advances in knowledge of the molecular pathogenesis of lung cancer. These tools include molecular and cellular biology and are starting to provide an insight into how the tumor cell, by altering oncogenes and tumor suppressor genes, achieves growth advantage, uncontrolled proliferation and metastatic behavior via disruption of key cell-cycle regulators and signal transduction cascades. Moreover, new knowledge is being developed in terms of the molecular definition of individual susceptibility to tobacco smoke carcinogens. These tools are being translated into clinical strategies to complement surgery, radiotherapy, and chemotherapy and also to assist in primary and secondary prevention efforts. This review summarizes current knowledge of the molecular pathogenesis of lung cancer. From this we know that respiratory epithelial cells require many genetic alterations to become invasive and metastatic cancer. We can detect cells with a few such changes in current and former smokers, offering the opportunity to intercede with a biomarker-monitored prevention and early detection effort. This will be coupled with new advances in computed tomography-based screening. Finally, because the molecular alterations are known, new mechanism-based therapies are being developed and brought to the clinic, including new drugs, vaccines, and gene therapy, which also must be integrated with standard therapies.

Primary signet-ring cell carcinoma of the lung: histochemical and immunohistochemical characterization

To establish criteria for differential diagnosis and to clarify the histogenesis of primary signet-ring cell carcinoma (SRCC) of the lung, five cases were studied by mucin-histochemical and immunohistochemical analyses and compared with SRCC of the gastrointestinal tract and mucus-producing adenocarcinoma of the lung. The proportion of signet-ring cell component varied from 10% to 90% in four cases, and the remaining tumor was a pure SRCC. Mucin-histochemistry showed a close similarity between lung SRCC and goblet cell-type or bronchial gland cell-type adenocarcinoma of the lung. Eighty percent of SRCCs showed positive immunoreactions for lactoferrin, a marker of bronchial gland cell differentiation, the results being consistent with the conclusions in previous studies that lung SRCC is closely related to bronchial gland cell-type adenocarcinoma. The incidence of K-ras mutation detected by the restriction fragment length polymorphism method was relatively high in lung SRCC (three of five) and goblet cell-type adenocarcinoma of the lung (four of four). Mucin-histochemistry indicated that lung SRCC has mucin production similar to that of the colon and colorectal-type SRCCs of the stomach but not to that of gastroduodenal-type SRCC of the stomach. Immunohistochemical staining for MUC-1 and MUC-2 glycoproteins showed a distinct difference; lung SRCC was positive for MUC-1 but negative for MUC-2, whereas colon SRCC and colorectal-type gastric SRCC were negative for MUC-1 but positive for MUC-2.Thus, by a combination of mucin-histochemistry and MUC-1 and MUC-2 immunohistochemistry, primary lung SRCC can be distinguished from metastatic lung SRCC originating in the gastrointestinal tract.