Morphometric Profiling of Lung Cancers—Its Association With Clinicopathologic, Biologic, and Molecular Genetic Features

The nonsmokers' and smokers' pathways in lung adenocarcinoma: Histological progression and molecular bases

There could be two carcinogenetic pathways for lung adenocarcinoma (LADC): the nonsmokers' pathway and the smokers' pathway. This review article describes the two pathways with special reference to potential relationships between histological subtypes, malignant grades, and driver mutations. The lung is composed of two different tissue units, the terminal respiratory unit (TRU) and the central airway compartment (CAC). In the nonsmokers' pathway, LADCs develop from the TRU, and their histological appearances change from lepidic to micropapillary during the progression process. In the smokers' pathway, LADCs develop from either the TRU or the CAC, and their histological appearances vary among cases in the middle of the progression process, but they are likely converged to acinar/solid at the end. On a molecular genetic level, the nonsmokers' pathway is mostly driven by EGFR mutations, whereas in the smokers' pathway, approximately one-quarter of LADCs have KRAS mutations, but the other three-quarters have no known driver mutations. p53 mutations are an important factor triggering the progression of both pathways, with unique molecular alterations associated with each, such as MUC21 expression and chromosome 12p13-21 amplification in the nonsmokers' pathway, and HNF4α expression and TTF1 mutations in the smokers' pathway. However, investigation into the relationship between histological progression and genetic alterations is in its infancy. Tight cooperation between traditional histopathological examinations and recent molecular genetics can provide valuable insight to better understand the nature of LADCs.

Frequent DYRK2 gene amplification in micropapillary element of lung adenocarcinoma - an implication in progression in EGFR-mutated lung adenocarcinoma

The present study aimed to discern the molecular alterations involved in the progression of EGFR-mutated lung adenocarcinoma (LADC). We previously demonstrated that the micropapillary (mPAP) element is the most important histological factor for assessing malignant grades in LADCs. Therefore, mPAP and other elements were separately collected from three cases of EGFR-mutated LADC using laser capture microdissection and subjected to a comprehensive mRNA expression analysis. We focused on DYRK2 in this study because its level showed a substantial increase in EGFR-mutated LADCs with mPAP. We also immunohistochemically examined 130 tumors for the expression of DYRK2. The results confirmed a strong expression of DYRK2 in EGFR-mutated LADC with mPAP. Fluorescent in situ hybridization (FISH) analyses targeting the DYRK2 locus revealed frequent gene amplification in EGFR-mutated LADC, specifically occurring in the high-grade components, like mPAP. In summary, the results of this study suggest that DYRK2 overexpression through gene amplification is one of the molecular mechanisms responsible for promoting the progression of EGFR-mutated LADC.

Mitosis count and number of cancer cells in cases of primary pulmonary adenocarcinoma: Correlations among phosphorylated histone 3, number of cancer cells, nuclear grade, pathologic features and prognosis

Immunohistochemistry findings for the phosphorylated form of histone 3 (pHH3) have been shown to be a reliable mitosis-specific marker. We evaluated the correlation between pHH3-stained mitotic figures (PHMFs) and clinical outcome, and compared the results with findings for numbers of PHMFs and cancer cells. The primary tumor was obtained from 113 patients with pulmonary adenocarcinomas (≤2 cm maximum dimension). All specimens were stained with pHH3, then the number of cancer cells in each was determined. Cases with a cancer-cell index ≥1000 showed worse recurrence-free survival as compared to those with a value <1000 (P < 0.001). Also, cases with a pHH3 index ≥0.27 showed worse recurrence-free survival as compared to <0.27 (P = 0.001) and cases with a pHH3/cancer-cell index ≥0.001 showed worse recurrence-free survival as compared to <0.001 (P = 0.002). Multivariate analysis demonstrated that pHH3/cancer-cell index was significantly correlated with prognosis, but not Ki-67 index. The number of cancer cells was also strongly correlated with progression of Noguchi's classification and WHO pathologic type. pHH3/cancer-cell index was correlated with prognosis, and those were useful for prognostic evaluation of pulmonary adenocarcinoma patients. Furthermore, cancer cell number was correlated with Noguchi's classification and WHO pathologic type.

A Histopathological Feature of EGFR-Mutated Lung Adenocarcinomas with Highly Malignant Potential - An Implication of Micropapillary Element

The purpose of this study was to define histological features determining the malignant potential of EGFR-mutated lung adenocarcinoma (LADC). Surgically resected tumors (EGFR-mutated LADCs with (21) and without (79) lymph node metastasis and EGFR wild-type LADCs with (26) and without (108) lymph node metastasis) and biopsy samples from inoperably advanced tumors (EGFR-mutated LADCs (78) and EGFR wild-type LADCs (99)) were examined. In surgically resected tumors, the EGFR-mutated LADCs with lymph node metastasis had the micropapillary element in a significantly greater proportion than others (Mann-Whitney tests P ≤0.026). The proportion of micropapillary element was higher in the EGFR-mutated LADC at the advanced stage (stage II, III, or IV) than in the tumor at the early stage (stage I) (Mann-Whitney test, P<0.0001). In the biopsy samples from inoperably advanced LADCs (177), EGFR-mutated tumors also had micropapillary element at a higher frequency than EGFR-wild type tumors (53/78 (68%), versus 30/99 (30%), Pearson x2 test, P<0.0001). In stage I EGFR-mutated LADCs (84), the tumors with the micropapillary element (34) exhibited a significantly higher recurrence rate than tumors without micropapillary element (50) (5-year Recurrence-free survival 64.4% versus 93.3%, log-rank test P = 0.028). The micropapillary element may be an exclusive determinant of malignant potential in EGFR-mutated LADC. It is suggested that EGFR-mutated LADC may develop through a distinct histogenesis, in which the micropapillary element is important for promoting progression.

Association of a genetic variant of CYP19A1 with multicentric development of lung adenocarcinomas

BACKGROUND

The detection rate of multiple lung adenocarcinomas, which display multiple ground glass opacity nodules in the peripheral lung, is increasing because of advances in high resolution computed tomography. The genetic backgrounds of multiple nodules and the mechanisms that underlie their multicentric development are unknown. In this study, we examined single nucleotide polymorphisms (SNPs) of the cytochrome P450 19A1 gene to determine if they are associated with multiple adenocarcinomas risk.

METHODS

Fifty-one cases of multiple adenocarcinomas with lepidic growth, 62 cases of a single adenocarcinoma with lepidic growth, and 126 control cases were analyzed. Three SNPs were analyzed by using a 5' nuclease assay with TaqMan minor-groove-binder probe. The expression level of CYP19A1 in the noncancerous lung was quantified by real-time reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

A minor allele of SNP rs3764221, which is located in the CYP19A1 gene, was significantly associated with multiple adenocarcinomas risk (adjusted odds ratio = 3.06; P = 0.006). Other polymorphisms of CYP19A1 were not significantly associated with the risk of multiple adenocarcinomas. A minor allele of SNP rs3764221 was also associated with a higher level of CYP19A1 messenger RNA expression (P = 0.03).

CONCLUSIONS

SNP rs3764221 contributes to the development of multicentric adenocarcinomas in the peripheral lung by causing higher levels of CYP19A1 expression.

An association between nuclear morphology and immunohistochemical expression of p53 and p16INK4A in lung cancer cells

Nuclear atypia is one of the most important morphological features used to diagnose malignant neoplasms. The potential molecular alteration that causes nuclear atypia remains unknown. P53 and p16INK4A play crucial roles in cell cycle checkpoints and repairing DNA damage to maintain integrity of the genome. Thus, inactivation of p53 and p16INK4A has been hypothesized to alter the chromatin structure and result in nuclear atypia. This study examined 201 primary lung cancers for the immunohistochemical expression of p53 and p16INK4A, and analyzed potential associations with the essential elements of nuclear atypia, such as nuclear size, circularity of the outline, and the density and granularity of chromatin. Tumors that expressed high levels of p53 had larger nuclei with higher chromatin density and distorted nuclear outlines. Tumors that expressed low levels of p16INK4 had larger nuclei with distorted nuclear outlines. Thus, alterations in p53 and p16INK4A may be the potential cause of nuclear atypia in neoplastic cells.

Prognostic value of the IASLC/ATS/ERS classification of lung adenocarcinoma in stage I disease of Japanese cases

A new classification of adenocarcinoma (ADC) was proposed by the International Association for the Study of Lung Cancer, the American Thoracic Society, and the European Respiratory Society (IASLC/ATS/ERS) in 2011. The present study evaluates its prognostic value in stage I disease of Japanese cases. One-hundred-and-seventy-nine cases with pathological stage I ADC were classified according to the new classification system and their association with disease recurrence was analyzed. Eighteen (10.1%) and 24 (13.4%) cases were adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA), respectively. One-hundred-and-thirty-seven cases (76.5%) were invasive adenocarcinoma (IVA), in which 43 (24.0%) were lepidic (LEP), 59 (33.0%) were acinar (ACN), 16 (8.9%) were papillary (PAP), 1 (0.6%) was micropapillary (MPAP), 12 (6.7%) were solid predominant subtypes (SOL), and 6 (3.4%) were invasive mucinous adenocarcinoma (MUC). The5-year disease-free survivals (DFS) of patients with AIS and MIA were 100%. Those of LEP, ACN, PAP, SOL and MUC were 93.5%, 83.7%, 75.0%, 44.4% and 62.5%, respectively. Multivariate analysis showed that high-histological grade (SOL, MPAP, MUC) had an independent prognostic value to predict post-operative recurrence (HR 3.661, 95% CI 1.421-9.437, P = 0.007). In conclusion, the present study demonstrates a prognostic value of the 2011 IASLC/ATS/ERS classification of ADC in Japanese cases.

Effective method for the isolation and proliferation of primary lung cancer cells from patient lung tissues

We have developed a technique for isolating and culturing primary lung cancer cells extracted from patient tissue to facilitate anti-cancer drug development. Patient-derived lung cancer tissues were mechanically dissociated to 40-100 μm. Dispase was then used to isolate cultured lung cancer cell populations, which were re-plated on Matrigel-coated dishes containing N2-supplemented medium and growth factors. This method allows pure populations of primary non-small cell lung cancer cells to be grown in vitro. The isolated cells exhibited hallmark cancerous properties such as abnormal chromosomes and in vivo tumor formation. The cell lines generated through this procedure may help to advance our knowledge of certain forms of lung cancer and may also be useful for developing patient-specific anti-cancer drug screening procedures.

A grading system combining architectural features and mitotic count predicts recurrence in stage I lung adenocarcinoma

The International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS) has recently proposed a new lung adenocarcinoma classification. We investigated whether nuclear features can stratify prognostic subsets. Slides of 485 stage I lung adenocarcinoma patients were reviewed. We evaluated nuclear diameter, nuclear atypia, nuclear/cytoplasmic ratio, chromatin pattern, prominence of nucleoli, intranuclear inclusions, mitotic count/10 high-power fields (HPFs) or 2.4 mm(2), and atypical mitoses. Tumors were classified into histologic subtypes according to the IASLC/ATS/ERS classification and grouped by architectural grade into low (adenocarcinoma in situ, minimally invasive adenocarcinoma, or lepidic predominant), intermediate (papillary or acinar), and high (micropapillary or solid). Log-rank tests and Cox regression models evaluated the ability of clinicopathologic factors to predict recurrence-free probability. In univariate analyses, nuclear diameter (P=0.007), nuclear atypia (P=0.006), mitotic count (P<0.001), and atypical mitoses (P<0.001) were significant predictors of recurrence. The recurrence-free probability of patients with high mitotic count (≥5/10 HPF: n=175) was the lowest (5-year recurrence-free probability=73%), followed by intermediate (2-4/10 HPF: n=106, 80%), and low (0-1/10 HPF: n=204, 91%, P<0.001). Combined architectural/mitotic grading system stratified patient outcomes (P<0.001): low grade (low architectural grade with any mitotic count and intermediate architectural grade with low mitotic count: n=201, 5-year recurrence-free probability=92%), intermediate grade (intermediate architectural grade with intermediate-high mitotic counts: n=206, 78%), and high grade (high architectural grade with any mitotic count: n=78, 68%). The advantage of adding mitotic count to architectural grade is in stratifying patients with intermediate architectural grade into two prognostically distinct categories (P=0.001). After adjusting for clinicopathologic factors including sex, stage, pleural/lymphovascular invasion, and necrosis, mitotic count was not an independent predictor of recurrence (P=0.178). However, patients with the high architectural/mitotic grade remained at significantly increased risk of recurrence (high vs low: P=0.005) after adjusting for clinical factors. We proposed this combined architectural/mitotic grade for lung adenocarcinoma as a practical method that can be applied in routine practice.

A nuclear grading system is a strong predictor of survival in epitheloid diffuse malignant pleural mesothelioma

Epithelioid mesothelioma is the most prevalent subtype of diffuse malignant pleural mesothelioma in which only staging is prognostic for survival. In this study of epithelioid diffuse malignant pleural mesothelioma, we investigate the prognostic utility of nuclear features. The slides of 232 epithelioid diffuse malignant pleural mesothelioma patients (14 stage I, 54 stage II, 130 stage III, and 34 stage IV) from a single institution were reviewed for the following seven nuclear features: nuclear atypia, nuclear/cytoplasmic ratio, chromatin pattern, intranuclear inclusions, prominence of nucleoli, mitotic count, and atypical mitoses. MIB-1 immunohistochemistry was performed using tissue microarray, and MIB-1 labeling index was recorded as the percentage of positive tumor cells. Median overall survival of all patients was 16 months and correlated with nuclear atypia (P<0.001), chromatin pattern (P=0.031), prominence of nucleoli (P<0.001), mitotic count (P<0.001), and atypical mitoses (P<0.001) by univariate analysis. Multivariate analysis revealed nuclear atypia (P=0.012) and mitotic count (P<0.001) as independent prognostic factors, and these two factors were utilized to create a three-tier nuclear grade score. The resulting nuclear grade stratified patients into three distinct prognostic groups: grade I (n=107, median overall survival=28 months), grade II (n=91, 14 months), and grade III (n=34, 5 months). Not only was nuclear grade an independent predictor of overall survival (P<0.001), but it was also a stronger discriminator of survival than all currently available factors. Furthermore, nuclear grade was associated with time to recurrence (P=0.004) in patients who underwent complete surgical resection (n=159). MIB-1 labeling index correlated with mitotic count (P<0.001) and nuclear atypia (P=0.037) and stratified overall survival (P<0.001) and time to recurrence (P=0.048), confirming the prognostic value of the nuclear grade. Nuclear grading in epithelioid mesothelioma provides a simple, practical, and cost-effective prognostic tool that better stratifies clinical outcome and time to recurrence than currently available clinicopathologic factors.

Pleomorphic epithelioid diffuse malignant pleural mesothelioma: a clinicopathological review and conceptual proposal to reclassify as biphasic or sarcomatoid mesothelioma

INTRODUCTION

In patients with epithelioid diffuse malignant pleural mesothelioma (DMPM), clinical stage is the current primary prognostic factor. We sought to investigate whether histologic subtyping can prognostically stratify patients with epithelioid DMPM.

METHODS

Hematoxylin and eosin-stained slides of 232 patients with epithelioid DMPM (14 stage I, 54 stage II, 130 stage III, and 34 stage IV) from a single institution were reviewed. We classified the tumors into five subtypes, according to the predominant histological pattern: trabecular, tubulopapillary, micropapillary, solid, and pleomorphic (≥10% of tumor).

RESULTS

Median overall survival (OS) of all patients with epithelioid DMPM was 16.2 months. Patients with pleomorphic subtype (n = 34) had the worst median OS (8.1 months), followed by solid (n = 89, 13.7 months), micropapillary (n = 20, 15.8 months), tubulopapillary (n = 51, 17.9 months), and trabecular (n = 38, 24.9 months). The pleomorphic subtype was associated with lymphatic and vascular invasion (p < 0.001). The micropapillary subtype was associated with lymphatic invasion (p < 0.001). In univariate analyses, pleomorphic subtype was significantly associated with poor OS (p = 0.003). The pleomorphic subtype showed no significant difference on OS compared with biphasic and sarcomatoid DMPM. In a multivariate analysis, the pleomorphic subtype was an independent predictor of poor OS (p = 0.031). In patients who underwent R1 resection, pleomorphic subtype had the shortest median time to recurrence (13.7 months).

CONCLUSION

Our finding that the pleomorphic subtype is a predictor of aggressive behavior in epithelioid DMPM with no survival difference from biphasic or sarcomatoid DMPM suggests that it may be best regarded as a sarcomatoid pattern rather than a subtype of epithelioid DMPM.

KRAS gene mutations in lung cancer: particulars established and issues unresolved

Lung cancer, like other cancers, is considered to develop through the accumulation of genetic alterations. Mutation of the KRAS gene is one of the most important events in carcinogenesis of the lung. The KRAS gene, belonging to the RAS gene family, encodes a membrane-bound 21-kd guanosine triphosphate (GTP)-binding protein. Single point mutations in this protein result in continuous activation to transmit excessive signals, promoting a variety of biological events. In lung cancers, the mutations concentrate at codon 12 and mostly affect adenocarcinomas (ADCs). They also affect atypical adenomatous hyperplasia, the precursor of ADCs. Therefore, mutation of the KRAS gene is suggested to confer a growth advantage to airway epithelial cells enabling them to expand clonally early in the development of ADCs. The mutation is also a reliable marker of an unfavorable response to certain molecular-targeting therapies. Furthermore, patients with ADCs affected by mutations have been reported to exhibit a significantly higher risk of postoperative disease recurrence. Thus, the significance of KRAS gene mutations has been investigated extensively. However, not all the details emerged. In this review, particulars that have been established are introduced, and important issues remaining to be resolved are discussed, with special reference to carcinogenesis of the lung.

Early growth response-1 induces and enhances vascular endothelial growth factor-A expression in lung cancer cells

Vascular endothelial growth factor-A (VEGF-A) is crucial for angiogenesis, vascular permeability, and metastasis during tumor development. We demonstrate here that early growth response-1 (EGR-1), which is induced by the extracellular signal-regulated kinase (ERK) pathway activation, activates VEGF-A in lung cancer cells. Increased EGR-1 expression was found in adenocarcinoma cells carrying mutant K-RAS or EGFR genes. Hypoxic culture, siRNA experiment, luciferase assays, chromatin immunoprecipitation, electrophoretic mobility shift assays, and quantitative RT-PCR using EGR-1-inducible lung cancer cells demonstrated that EGR-1 binds to the proximal region of the VEGF-A promoter, activates VEGF-A expression, and enhances hypoxia inducible factor 1alpha (HIF-1alpha)-mediated VEGF-A expression. The EGR-1 modulator, NAB-2, was rapidly induced by increased levels of EGR-1. Pathology samples of human lung adenocarcinomas revealed correlations between EGR-1/HIF-1alpha and VEGF-A expressions and relative elevation of EGR-1 and VEGF-A expression in mutant K-RAS- or EGFR-carrying adenocarcinomas. Both EGR-1 and VEGF-A expression increased as tumors dedifferentiated, whereas HIF-1alpha expression did not. Although weak correlation was found between EGR-1 and NAB-2 expressions on the whole, NAB-2 expression decreased as tumors dedifferentiated, and inhibition of DNA methyltransferase/histone deacetylase increased NAB-2 expression in lung cancer cells despite no epigenetic alteration in the NAB-2 promoter. These findings suggest that EGR-1 plays important roles on VEGF-A expression in lung cancer cells, and epigenetic silencing of transactivator(s) associated with NAB-2 expression might also contribute to upregulate VEGF-A expression.

Proposal of an improved histological sub-typing system for lung adenocarcinoma - significant prognostic values for stage I disease

We have established a concise sub-typing system suitable for predicting the postoperative outcome in cases of stage I lung adenocarcinoma (ADC), using morphometric profiling. The association between postoperative disease recurrence and a variety of morphological features including histological architecture, cell type, cytoplasmic color/internal structure, nuclear shape/size, chromatin pattern, and nucleoli count/remarkableness, was analyzed. Histological architecture had the most prognostic value and could be subdivided into low-grade (bronchioloalveolar, papillary and tubular: "tubular" in this paper is defined as a tubular or glandular structure lined with single-layered neoplastic cells) and high-grade (acinar and solid: "acinar" is defined as a tubular or glandular structure lined with poly-layered neoplastic cells or as a fused glandular structure such as the cribriform pattern) components. The subgroups separated based on a cut-off value, 71.5% of the high-grade component comprised by a tumor, which was calculated according to a relative operating characteristic curve, exhibited a significant difference in disease recurrence [estimated 5-year disease-free survival rate, 95.3% in the low-grade group versus 66.7% in the high-grade group, hazard ratio 7.35, Log-rank test p = 0.002]. The sub-grouping system is concise and suitable for practical use. It will improve the histological classification of ADC.