The pathobiologic features of carcinomas of type II pneumocytes. An immunocytologic study

Surfactant protein A compared to thyroid transcription factor-1 in identifying metastatic tumors of lung origin in cytopathology

INTRODUCTION

Differentiating primary tumors and metastases of lung origin from other neoplasms often cannot be done on cytomorphology alone. Immunocytochemistry using markers such as thyroid transcription factor-1 (TTF-1) is employed for this purpose. Surfactant protein A (SPA) is a glycoprotein with multiple functions in the lung. There have been limited immunohistochemical studies investigating the diagnostic role of SPA. This study aimed to determine the diagnostic utility of SPA compared with that of TTF-1 in identifying tumors of lung origin in cytology samples.

MATERIALS AND METHODS

A total of 155 consecutive cytology specimens procured outside of the lung were analyzed, in which SPA immunohistochemistry was reported. Cases were reviewed to document final diagnoses, immunostain results (including TTF-1), and histopathology follow-up when available.

RESULTS

Cytoplasmic SPA immunoreactivity was identified primarily in metastatic lung adenocarcinomas (ADC). SPA was also positive in 3 carcinomas of gynecologic/breast origin. SPA and TTF-1 specificity and positive predictive value were high (>90%) with relatively low sensitivity and negative predictive value for identifying metastatic ADC of lung origin. A panel of SPA and TTF-1 correctly identified most (79.7%) lung metastatic adenocarcinomas.

CONCLUSIONS

SPA is a useful cytoplasmic marker to confirm lung origin in metastatic nonmucinous ADC. However, SPA is limited by having low sensitivity and being negative in up to 35% of metastatic ADCs of lung origin, whereas TTF-1 exhibited better sensitivity. SPA may rarely demonstrate false immunoreactivity in a subset of gynecologic/breast carcinomas. Employing a panel of SPA and TTF-1 has better diagnostic utility than either stain alone.

Pseudomesotheliomatous carcinoma of the lung with a distinct morphology, immunohistochemistry, and comparative genomic hybridization profile

We report 4 cases of pseudomesotheliomatous carcinoma of the lung, which has clinical and microscopic features similar to malignant mesothelioma, but with ultrastructural, immunohistochemical, and molecular characteristics suggestive of a histogenesis from type II pneumocytes. Neoplasm grows as a diffuse or solid pattern of large polygonal cells with sharply defined borders. Hale's colloidal iron is positive in the cytoplasm of small groups of cells and, focally, in some intercellular spaces. Ultrastructure showed short microvilli in the surface. Immunohistochemically, tumor cells were positive for thyroid transcription factor-1, podoplanin, mesothelin, pan-cytokeratin, CK-7, CK-19, Ber-EP4, epithelial membrane antigen, apoprotein surfactant A, epidermal growth factor receptor, Leu-M1, carcinoembryonic antigen, E-cadherin, and CD-44 and negative for mesothelioma markers thrombomodulin and calretinin. In some areas, there were small cysts which contained a concentric fibrilar basophilic material apoprotein surfactant A positive. Chromosomal imbalances with comparative genomic hybridization technique were identified with a median of 15 abnormalities per case (range, 1-26): 51 gains, 6 losses, and 1 high-level amplification. The most frequent aberrations among the cases were gains on chromosomes regions 1q, 3q, 5p, 8q, 16p, and 18q and losses in 17p11-13 and 17q 22-q25. High-level amplifications were detected on 7p13-p21. In all cases, there was a characteristic association between the gains on 16p and those on 18q. The 4 cases resulted in death in less than 14 months, in spite of complete surgery and chemotherapy in 2 cases. Our aim is to complement the current understanding of this pseudomesotheliomatous "pneumocytic" carcinoma and alert pathologists to this rare entity to avoid misdiagnosis.

Epidermal growth factor receptor mutations in lung cancers

In 2004, two groups reported somatic mutations in the gene for the epidermal growth factor receptor (EGFR) in patients with non-small cell lung cancer (NSCLC), which were highly correlated with the clinical response to the anticancer drug, gefitinib. Since then, a tremendous amount of knowledge has accumulated, and sheds light on significant oncological properties as well as the clinical relevance of this mutation, which could be applicable to other malignancies. The EGFR mutations are distributed throughout the kinase domain, but a deletion in exon 19 and the point mutation L858R in exon 21 account for approximately 90%, which confer a greater response to gefitinib treatment, compared with other types of EGFR mutations. These EGFR mutations in the tyrosine kinase domain are seldom acquired in cancers of the other organs and the mutations preferentially involve a subset of lung cancers, which are clinicopathologically characterized by female sex, non-smoking, adenocarcinoma histology and East Asian ethnicity. In Japan, the EGFR mutations are detected in approximately 30% of overall NSCLC and approximately 40% of surgically resected adenocarcinomas. The morphological features of adenocarcinomas harboring the mutations were reported to be frequent in those with bronchioloalveolar features, but it is suggested that the cellular lineage of the putative original cells of the cancers refines the subset more clearly. In the present study the current knowledge of EGFR mutations is reviewed, insights from which raise many further questions, and thus suggest new directions for future research.

Ultrastructural study of nuclear inclusions immunohistochemically positive for surfactant protein A in pulmonary adenocarcinoma with special reference to their morphogenesis

To investigate the fine-structural nature of nuclear inclusions immunopositive for surfactant protein A (SP-A) antibody staining, a detailed ultrastructural study was performed, as well as immunohistochemical examination of pulmonary adenocarcinomas. Surgically resected tumor specimens from 31 patients were examined by immunohistochemistry focused on reactivity to SP-A and thyroid transcription factor 1 (TTF-1) antibodies. Only cases with >5% positive nuclear inclusions in cancer cells were considered positive, some of which were examined by electron microscopy. Immunohistochemically, 6 of 31 cases were doubly positive for SP-A and TTF-1 antibodies. On electron microscopy, SP-A-positive nuclei contained diffuse or globular fine granular substance as inclusions. Both types of globular and diffuse inclusions were sometimes connected to the inner nuclear membrane, in association with fragmented or stacked membranous structures. The findings of this study suggested that nuclear inclusions positive for SP-A antibody staining in adenocarcinomas of the lung were derived from accumulated content in the perinuclear cistern resembling pseudoinclusion processes and composed of proteins antigenically cross-reactive with SP-A.

Surfactant Protein A Detection in Large Cell Carcinoma of the Lung

Large cell carcinomas of the lung are undifferentiated malignant epithelial tumors that lack cytologic features of small cell carcinoma, glandular cell carcinoma, or squamous cell differentiation. Lung surfactant protein A (SP-A) is produced by alveolar type II cells and Clara cells. Most bronchioloalveolar carcinomas of the lung react positively for SP-A. Positive SP-A staining of large cell carcinoma of the lung could indicate that at least part of these tumors have the same cellular origin or differentiation as bronchioloalveolar carcinoma. The authors determined the SP-A staining of 63 large cell carcinomas of the lung by IHC. In 20 of the 63 (32%), the tumors stained positive for SP-A. This may imply that about one third of large cell carcinomas of the lung have a similar cellular origin or differentiation as bronchioloalveolar carcinoma. The significance of this finding for prognosis and new forms of treatment remains to be determined.

Surfactant Protein A Detection in Primary Pulmonary Adenocarcinoma without Bronchioloalveolar Pattern

BACKGROUND

Immunohistochemical studies in human lung carcinoma reported positive staining of tumor cells for surfactant protein A (SP-A), especially in peripheral airway cell carcinoma, which include bronchioloalveolar carcinoma and in some reports also papillary subtypes.

OBJECTIVE

The purpose of this study was to determine the SP-A expression in tumor cells of lung adenocarcinoma without a bronchioloalveolar pattern, classified according to the WHO.

METHODS

In total, 169 primary adenocarcinomas of the lung (109 acinar, 32 solid with mucin, 24 papillary and 4 mucinous) were examined by immunohistochemistry for SP-A expression.

RESULTS

Twenty-five percent of acinar, 38% of papillary and 3% of solid adenocarcinoma with mucin showed a positive intracytoplasmic SP-A reaction of the tumor cells. None of the mucinous adenocarcinomas stained for SP-A. This study included the largest number of acinar adenocarcinomas and solid adenocarcinomas with mucin studied for SP-A. We clearly demonstrated that also primary lung adenocarcinoma without a bronchioloalveolar pattern can express SP-A. A positive staining of hyperplastic type II cells surrounding the tumors or entrapped in the tumor could clearly be differentiated from the SP-A-positive stain of tumor cells.

CONCLUSION

These results support the theory that SP-A-producing cells may generate not only bronchioloalveolar and papillary carcinoma, but also other subtypes of lung adenocarcinoma.

EGFR Mutation Is Specific for Terminal Respiratory Unit Type Adenocarcinoma

We have previously reported that terminal-respiratory-unit (TRU) type adenocarcinoma is a distinct subset of lung adenocarcinoma in terms of molecular pathway for carcinogenesis and phenotypic profiles. This type of cancer shows TRU features, characterized by distinct cellular morphology and the expression of TTF-1 and surfactant proteins. Recently, two groups published novel mutations of the epidermal growth factor receptor (EGFR) that are closely associated with clinical response to gefitinib. The clinicopathologic features of gefitinib responders overlap with those of TRU-type adenocarcinoma, and the characteristics of TRU are likely to correspond to the bronchioloalveolar features reported as a predictor of gefitinib response. We therefore examined the characteristics of EGFR-mutated pulmonary adenocarcinomas with special reference to TRU-type adenocarcinoma. EGFR mutation was detected in 97 of 195 adenocarcinomas, 91 of 149 TRU-type adenocarcinomas and 6 of 46 tumors of other types. Conversely, 91 of 97 EGFR-mutated adenocarcinomas were categorized as TRU-type adenocarcinomas. This type-specific involvement was confirmed by logistic regression model. In addition, EGFR mutation was detected in some cases of atypical adenomatous hyperplasia, a preinvasive lesion of TRU-type adenocarcinoma. These findings further confirm that TRU-type-adenocarcinoma is a distinct adenocarcinoma subset in which a particular molecular pathway is involved.

Prognostic significance of frequent acidophilic nuclear inclusions in adenocarcinoma of the lung with immunohistochemical and ultrastructural studies

BACKGROUND

Adenocarcinoma of the lung occasionally has acidophilic nuclear inclusions (ANIs). Some studies have reported that the incidence of ANIs was higher in well differentiated tumor types and have suggested that adenocarcinoma patients with ANIs might have a more favorable prognosis; however, to the authors' knowledge, statistically significant prognostic findings were not reported. The objective of the current study was to assess the prognostic significance of ANI in patients with pulmonary adenocarcinoma and, moreover, to characterize ANI immunohistochemically and ultrastructurally.

METHODS

Surgically resected tumor specimens from 147 patients with primary pure adenocarcinoma of the lung were examined. Only obvious ANIs surrounded by a clear halo on hematoxylin and eosin-stained slides were counted; the authors classified cases with > or = 10 ANIs per 10 high-power fields (/10 HPF) as frequent-ANI cases, cases with < 10 ANIs/10 HPF as infrequent-ANI cases, and cases without ANIs as non-ANI cases in the current study.

RESULTS

Nineteen frequent-ANI cases (12.9%) and 16 infrequent-ANI cases (10.9%) were found; the remaining 112 cases (76.2%) were considered to be non-ANI cases. The majority of ANIs immunohistochemically contained surfactant apoprotein and ultrastructurally corresponded to invagination of the inner nuclear membrane, showing a tubular or amorphous configuration. Frequent-ANI patients showed significantly better prognosis than the other two groups on both overall univariate analysis and univariate analysis limited to patients with International Union Against Cancer Stage I disease (P = 0.0096 and P = 0.0095, respectively). However, on the multivariate analysis only disease stage was shown to be a significant prognostic factor and frequent-ANI showed borderline significance (P = 0.0956).

CONCLUSIONS

Frequent ANIs appear to be of limited value in clarifying the prognosis of patients with lung adenocarcinoma.

Tumor uptake of radioiodinated anti-human pulmonary surfactant-associated protein monoclonal antibody PE10 in nude mice bearing human pulmonary adenocarcinoma in combination with an unlabeled preload

This study assessed the potential use of radioimmunoscintigraphy of pulmonary alveolar Type II cells tumor with the radiolabeled anti-human surfactant-associated protein (SP) monoclonal antibody (MAb) PE 10 in combination with preloads of unlabeled MAb. The in vitro binding of iodine-125 ((125)I)-labeled MAb PE 10 (1 microg), which had a specific radioactivity of 400 MBq/mg, on human pulmonary papillary adenocarcinoma NCI-H441 cells that produced SP was investigated. In NCI-H441 tumor-bearing nude mice, the tumor uptake of (125)I-MAb PE 10 (5 microg) was examined in combination with preloads of unlabeled MAb PE 10 (0, 5, 10, and 50 microg). An isotype-matched unassociated murine MAb was used as a control both in vitro and in vivo. (125)I-MAb PE 10 showed specific cell binding compared with (125)I-control MAb. Tumor uptake of (125)I-MAb PE 10 in vivo reached a peak of 4.97+/-0.33% injected dose per gram (%ID/g) at 48 h postinjection. Preloads of 5 and 10 microg unlabeled MAb PE 10 significantly enhanced tumor uptake at 48 h postinjection ( 5.94+/-0.29% ID/g and 5.72+/-0.29% ID/g, respectively), whereas preload of 50 microg unlabeled MAb PE 10 significantly decreased tumor uptake ( 2.75+/-0.32% ID/g) at 48 h. Preload of 5 microg unlabeled MAb PE 10 significantly increased the tumor-to-blood radioactivity ratio at 48 h ( 2.39+/-0.16). Preloads of unlabeled control MAb did not cause any significant change in tumor uptake. Immunohistochemistry showed the intracellular and pericellular patterns of SP expression in tumor cells. In conclusion, radioimmunoscintigraphy with MAb PE 10 labeled with a gamma-emitting radioiodine such as (123)I might be a useful means of targeting pulmonary alveolar Type II tumor cells in combination with preloading with an optimal dose of the unlabeled MAb.

Rhabdoid tumour of the lung is a dedifferentiated phenotype of pulmonary adenocarcinoma

AIMS

Primary rhabdoid tumour of the lung is rare, and histological and biological characteristics have not been fully documented. We describe three cases of primary lung rhabdoid tumour, all associated with adenocarcinoma, and investigate the histological features and biological characteristics.

METHODS AND RESULTS

Three cases were obtained from a total 902 cases of surgically removed primary lung tumours between 1986 and 1998. The rhabdoid cells were found to occupy about 50-90% of each tumour. All of the tumours had nonrhabdoid adenocarcinoma foci in the centre of the tumours. Transition between the adenocarcinomatous and rhabdoid components was demonstrated. Detailed immunohistochemical studies were carried out. The epithelial markers, cytokeratins and epithelial membrane antigen (EMA), were strongly expressed in rhabdoid and adenocarcinomatous components. Furthermore, surfactant apoprotein A was positive in both components in one case, but myoglobin, MyoD and HHF35 were not expressed. Vimentin was strongly and diffusely stained in all cases. The neuroendocrine markers, chromogranin A (all cases), neuron-specific antigen (NSE) (two cases) and CD56 (one case) were occasionally positive in only a small number of the rhabdoid tumour cells. GM-CSF was positively stained in one case, and the dedifferentiated characteristics of the rhabdoid cells was suggested. Proliferative cell nuclear antigen (PCNA) was strongly demonstrated in the rhabdoid tumour cells (all cases). To gain better understanding the highly proliferative characteristics of the tumours, p53 gene (exons 5-8) mutation was examined by DNA sequencing analysis; mutation of the p53 DNA was not detected. Overexpression of p53 protein was also not demonstrated in all cases. HPV6 was demonstrated in one case by PCR method and also non-isotopic in-situ hybridization (NISH). Two cases died in a short period of time (3 years and 4 months, respectively).

CONCLUSION

The rhabdoid cells in these three cases were considered to represent the dedifferentiated components of the accompanying adenocarcinoma. Dedifferentiated characteristics (neuroendocrine markers, GM-CSF, vimentin, and the aggressive behaviour) were evident.

Utility of surfactant protein B precursor and thyroid transcription factor 1 in differentiating adenocarcinoma of the lung from malignant mesothelioma

Differentiation of malignant mesothelioma from adenocarcinoma, particularly from a lung primary, remains a difficult diagnostic problem. Surfactant protein B precursor (pro-SP-B) and thyroid transcription factor 1 (ITF-1) are expressed selectively in the normal respiratory epithelium and in adenocarcinomas of the lung. In this study, we evaluated the utility of pro-SP-B and ITF-1 in distinguishing pulmonary adenocarcinomas and malignant mesotheliomas. Immunoreactivity for pro-SP-B and TTF-1 was examined in paraffin sections of 370 primary lung carcinomas (208 adenocarcinomas, 101 squamous cell carcinomas, and 61 large cell carcinomas) and 95 malignant mesotheliomas, using a pro-SP-B antiserum and a monoclonal TTF-1 antibody with a biotin-streptavidin detection system. Immunostaining for pro-SP-B was detected in 57% of adenocarcinomas, and 20% of large cell carcinomas. Immunoreactivity for TTF-1 was shown in 76% of adenocarcinomas and 26% of large cell carcinomas. Malignant mesotheliomas and squamous cell carcinomas did not stain with either antibody. The expression of pro-SP-B and TTF-1 in adenocarcinomas of the lung but not in malignant mesotheliomas shows that pro-SP-B and TTF-1 staining is useful in differentiating these neoplasms.

Surfactant proteins A and D: disease markers

The abundant and restricted expression of surfactant proteins SP-A and SP-D within the lung makes these collectins specific markers for lung diseases. The measurement of SP-A and SP-D in amniotic fluids and tracheal aspirates reflects lung maturity and the production level of the lung surfactant in infants with respiratory distress syndrome (RDS). The SP-A concentrations in bronchoalveolar lavage (BAL) fluids are significantly decreased in patients with acute respiratory distress syndrome (ARDS) and also in patients at risk to develop ARDS. The prominent increase of these proteins in BAL fluids and sputum is diagnostic for pulmonary alveolar proteinosis (PAP). The concentrations of SP-A and SP-D in BAL fluids from patients with idiopathic pulmonary fibrosis (IPF) and interstitial pneumonia with collagen vascular diseases (IPCD) are rather lower than those in healthy controls and the SP-A/phospholipid ratio may be a useful marker of survival prediction. SP-A and SP-D appear in the circulation in specific lung diseases. Their serum concentrations significantly increase in patients with PAP, IPF and IPCD. The successive monitoring of serum levels of SP-A and SP-D may predict the disease activity. The serum SP-A levels increase in patients with ARDS. SP-A is also a marker for lung adenocarcinomas and can be used to differentiate lung adenocarcinomas from other types and metastatic cancers from other origins, and to detect metastasis of lung adenocarcinomas.

Plutonium-induced proliferative lesions and pulmonary epithelial neoplasms in the rat: immunohistochemical and ultrastructural evidence for their origin from type II pneumocytes

Immunohistochemistry and transmission electron microscopy were used to clarify the cellular origin for plutonium-239-induced pulmonary proliferative (preneoplastic) epithelial lesions and epithelial neoplasms in F344 rats. Examples of each histologic type of proliferative lesion and neoplasm were stained by the avidin-biotin complex immunoperoxidase method using antibodies to rat surfactant apoprotein and Clara cell antigen. Rat surfactant apoprotein immunostaining was detected in type II pneumocytes in sections of normal lung, in the cells of the proliferative lesions classified histologically as alveolar epithelial hyperplasia (51) and mixed foci (alveolar epithelial hyperplasia with fibrosis) (30), and in adenomas (2), adenocarcinomas (3), and adenosquamous carcinomas (2). With the exception of one adenosquamous carcinoma, Clara cell antigen immunostaining was not detected in any of the pulmonary lesions but was detected in nonciliated cuboidal epithelial (Clara) cells in normal bronchioles. The epithelial cells of the proliferative lesions and neoplasms had ultrastructural features consistent with type II pneumocytes, i.e., the presence of cytoplasmic lamellar and multivesicular bodies. The results of these studies indicate that the majority of plutonium-induced proliferative epithelial lesions and neoplasms in the rat originate from alveolar type II pneumocytes.

Special subtypes of pulmonary adenocarcinomas indicated by different tumor cell HLA-expression and stromal infiltrates. A light, electron microscopic and immunohistologic study

A total of 31 human peripheral adenocarcinomas (AC) of the lung were subclassified by light and electron microscopy according to their phenotypic characteristics. The expression of HLA-A,B,C and HLA-DR on tumor cells, and the degree of subclassified mononuclear cell infiltration were determined using immunohistologic and morphometric methods. The study shows that pulmonary AC can be subdivided in two main types with different properties. The first type is characterized by mucin production comparable to that of bronchial goblet cells. These mucinous AC of type I show nearly no expression of HLA-DR; the tumor volume fraction with HLA-A,B,C expression is greatest in highly differentiated AC I, and decreases significantly with lower grades of differentiation. The AC of type II, possibly originating from the bronchioloalveolar transitional zone, show properties of Clara cells and of type II-pneumocytes by light and electron microscopy. These features include apically located electron-dense granules and lamellar bodies occurring often simultaneously. Both groups of HLA-antigens, HLA-A,B,C and HLA-DR, are homogeneously distributed in a similar phenotypic fashion to Clara cells and pneumocytes II of the normal lung. The significant differences in mononuclear cell infiltration between the two tumor types are possibly induced by the different HLA-DR expression, which have not been seen in AC from other sites. In AC II with homogeneous HLA-DR expression in the tumor epithelium, the numbers of tumor-infiltrating Langerhans cells, and T- and B-lymphocytes are significantly higher than in AC I, possibly indicating better host immunologic defense mechanisms against these tumors.

Secretory differentiation and cell type identification of a human fetal bronchial epithelial cell line (HFBE)

A human fetal bronchial epithelial cell line (HFBE) grew in an undifferentiated pattern under conventional culture conditions. Despite a somewhat fibroblastic shape the cells maintained immunoreactivity to cytokeratin, carcinoembryonic antigen and epithelial membrane antigen. When grown on a collagen gel in a growth-hormone-supplemented medium, their spindle shape became more conspicuous. With an additional supplement of vitamin A (6 micrograms/ml), most of the cells underwent differentiation by producing many bright inclusion bodies which proved to be strongly positive with periodic acid-Schiff and weakly positive with alcian blue staining. Electron microscopy revealed a well-developed rough endoplasmic reticulum, an enlarged Golgi apparatus and many highly electron-dense secretory granules resembling those of Clara cells. Biochemical analysis demonstrated that HFBE cells cultured on collagen gel with vitamin A secreted hyaluronic acid and neutral glycoproteins containing mainly N-linked glycoproteins whose glycans were of a complex type. A monoclonal antibody (SEC-41) generated against the neutral glycoproteins detected a glycoprotein of approximately 52 kDa in the spent culture medium of differentiated HFBE cells. This antibody also reacted with the intracytoplasmic secretory granules in these cells. When tested on frozen sections of lung tissue, the immunohistochemical reactivity of the SEC-41 antibody was confined to Clara cells, some type II pneumocytes in the adult lung, and respiratory epithelial cells in the fetal lung. Moreover, this antibody could detect secretory glycoprotein in broncho-alveolar lavages from two patients. This paper clearly demonstrates that cells derived from human fetal bronchial epithelium can be cultivated in an undifferentiated precursor state and, under appropriate culture conditions, can be stimulated to undergo differentiation into a Clara cell type.

Differentiation of Clara cell (distal type) antigen in human fetal bronchial epithelial cell line (HFBE)

A human fetal bronchial cell line (HFBE) grew in an undifferentiated pattern under conventional culture conditions. Despite a somewhat fibroblastic shape, however, they still maintained an immuno-reactivity to cytokeratin, carcinoembryonic antigen (CEA) and epithelial membrane antigen (EMA). When grown on a collagen gel in a growth hormone-supplemented medium, their spindle shape became more conspicuous. With the additional supplement of 6 micrograms/ml vitamin A, most of the cells underwent differentiation by producing many bright inclusion bodies which proved to be strongly positive to periodic acid Schiff (PAS) and barely positive to alcian-blue (AB) staining. Electron microscopy revealed well-developed rough endoplasmic reticulum (rER), enlarged Golgi apparatus and many highly electron-dense secretory granules resembling those of Clara cells. Biochemical analysis demonstrated that HFBE cells cultured on collagen gel with vitamin A secreted products containing glycoconjugates of two different molecular weights. The higher molecular weight-product was identified as hyaluronic acid and the lower molecular weight-product as a mixture of neutral glycoproteins containing mainly N-linked glycoproteins whose glycans were of a complex type. While the secretion of hyaluronic acid was inhibited by vitamin A in a dose-dependent manner, that of the neutral glycoproteins was most enhanced by vitamin A in the range from the physiological concentration of 600 ng/ml to 6 micrograms/ml. A monoclonal antibody (SEC-41) generated against the secretory products with the lower molecular weight detected a glycoprotein of approximately 52 kd in the spent culture medium of differentiated HFBE cells. This antibody also reacted with the intra-cytoplasmic secretory granules in these cells. When tested on freeze-sectioned lung tissue, immunohistochemical reactivity of SEC-41 antibody was confined to Clara cells, some type II pneumocytes in the adult lung and respiratory epithelial cells of the fetal lung tissue. Moreover, this antibody could detect the secretory glycoproteins in the broncho-alveolar lavages (BAL) of two human cases. This paper has clearly demonstrated that cells derived from human fetal bronchial epithelium can be cultivated in an undifferentiated precursor state and under appropriate culture conditions they can be stimulated to undergo differentiation into a Clara cell type.

Pulmonary surfactant protein A in pleural effusions

Pulmonary surfactant protein A (SP-A) is known to be a major phospholipid-associated glycoprotein in pulmonary surfactant, which is specific to the lung. Immunohistochemically, expression of SP-A in tumor tissues is found in approximately 50% of patients with lung adenocarcinoma but not in the other histologic types of lung cancer of metastatic lung tumors. In this study, the SP-A content of pleural effusions was determined using an enzyme-linked immunosorbent assay. These results showed that approximately 40% of patients with lung adenocarcinomas (27 of 67) had high levels of SP-A (greater than 500 ng/ml) in their pleural effusions. By contrast, patients with other histologic types of lung cancers, adenocarcinomas of different primary sites, and tuberculosis had low levels of SP-A in their pleural effusions. The determination of SP-A in malignant effusions will contribute to distinguishing primary lung adenocarcinoma from adenocarcinomas of miscellaneous origin.

Multiple molecular alterations in mouse lung tumors

Twenty-five mouse lung tumors induced by a single urethan treatment in female A/J, BALB/c, and (A/J x C3H/He)F1 (AC3) mice were analyzed for the presence of mutations at codon 61 of the Ki-ras gene and for the expression of the surfactant protein A (SP-A), retinoblastoma (Rb), growth arrest-specific-3 (gas-3), p53, c-myc, and thymidylate synthase (TS) genes. Ki-ras codon 61 mutations were detected in 22 of 25 tumor samples without differences among strains. In comparison with normal lungs, all the tumors showed increased SP-A mRNA levels, indicating their derivation from alveolar type II pneumocytes or Clara cells. Rb and gas-3 transcripts were instead found in all tumors at about tenfold and about 20-fold reduced levels, respectively. No apparent structural alterations or loss of heterozygosity at the Rb locus was detected in any tumors. The p53 mRNA was observed without variation in quantity or size in lung tumors and normal tissue. A threefold to fivefold c-myc overexpression was observed, without amplification of the gene. TS expression was only slightly increased, indicating no great differences in cell proliferation between lung tumors and normal tissue. Our data suggest that the pathogenesis of urethan-induced lung tumors in mice involves specific and recurrent molecular alterations (Ki-ras mutations, decrease of Rb and gas-3 expression, and increase of c-myc expression) that could represent different steps in lung carcinogenesis.

Pseudomesotheliomatous carcinoma of the lung. An immunohistochemical and ultrastructural study of three cases

The authors report immunohistochemical and electron microscopic studies on three new cases of pseudomesotheliomatous carcinoma of the lung. Although the distinct clinical and histopathologic features of this peripheral lung cancer were described many years ago, its recognition as a distinct variety of lung carcinoma has not gained wide acceptance. Little is known of its incidence and only few cases have been reported until now. In the current study the authors demonstrate the epithelial nature of this tumor by its positive immunohistochemical reactions for epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA), Leu-M1, B 72.3, and surfactant apoprotein. The ultrastructural features and staining of nuclear inclusions with surfactant apoprotein indicate differentiation into type II cells as found in other forms of peripheral lung adenocarcinoma. Despite these morphologic similarities, pseudomesotheliomatous carcinoma is characterized by extensive invasion of the pleura and rapidly fatal course. Because of this biologic behavior it deserves recognition as a distinct variant of peripheral lung carcinoma.

New functional cell-culture approach to pulmonary carcinogenesis and toxicology

Modern pulmonary toxicology (including lung carcinogenesis) has, to assist its rapid development, constantly incorporated the knowledge obtained through cell and tissue-culture studies. While this has been carried out in rather a passive manner until quite recently, the currently necessary multi-disciplinary approach increasingly requires more active involvement of cell/tissue-culture techniques in this area. Our understanding in this regard is that one of such requirements is to establish a cell-culture system consisting of a single population of possible target cells for certain classes of hazardous inhalants. In addition, such target cells in culture should be able to function in a manner as closely resembling the situation in vivo as possible. In view of the culture techniques presently available, this requirement is probably too ideal to be met immediately. Nevertheless, efforts have been made in the last decade to achieve functioning cultures of Clara cells, type II pneumocytes or small mucus granule cells (SMGC), using undifferentiated cells obtained from animal and human fetuses. This attempt forms a sharp contrast to the usual approach, in that while the latter tries to keep the functions of adult cells in an already differentiated state, the former aims at inducing functional differentiation in undifferentiated cells by manipulating culture conditions. In carrying out these efforts, we have shown clear evidence that the type II pneumocytes and Clara cells induced in vitro are closely cognate and share a common precursor cell in culture, and that SMGC are at a pre-stage of differentiation to Clara cells. We have also shown an induced capacity for xenobiotic activation and conjugation in SMGC in culture. Our next plan is to prove similar activity (of mixed-function oxidase) in Clara cells and type II pneumocytes induced to differentiate in culture.

Comparison of glycoconjugates at the surface of developing type II pneumocytes and Clara cells

The apical surface coat of type II pneumocytes and Clara cells in pre- and post-natal rat lung was examined with lectin histochemical methods. Lectins from Helix pomatia (HPA), peanut (PNA) and Maclura pomifera (MPA) were conjugated with horseradish peroxidase and used to stain paraffin sections of fixed lung with or without certain pre-treatments. HPA and MPA were observed to react with almost all type II pneumocytes at postnatal day 1. Type II pneumocytes that stained with a sialidase-PNA sequence increased from a few positive cells at postnatal day 5 to many in the adult. It has been reported that the surface coat of type II pneumocytes closely resembles that of Clara cells in its staining with histochemical methods employing cationic dyes or lectins including MPA and PNA. However, staining with HPA, especially after periodic acid oxidation, revealed many type II pneumocytes with strong reactivity but showed only a few Clara cells that were faintly positive. HPA also stained alveolar macrophages. The HPA affinity of macrophages, however, was labile to oxidation with periodic acid or galactose oxidase unlike that of type II pneumocytes. This difference suggests that HPA recognizes more than one type of sugar structure.

Distribution of vitamin B12 R-binder in lung tumors. Implications for cell differentiation

Expression of vitamin B12 R-binder, a specific binding protein for vitamin B12, was studied immunohistochemically in normal lung tissues and 107 lung tumors of various types. In normal tissues, vitamin B12 R-binder (R-binder) expression was restricted to the mucous cells of bronchial or bronchiolar epithelium and submucosal glands as well as to nonciliated bronchiolar (Clara) cells. Among lung carcinomas, 38% of squamous cell carcinomas, 42% of adenocarcinomas and 23% of large cell carcinomas showed positive staining for R-binder whereas small cell carcinomas did not. These findings offer the possibility that a majority of the histologic types of lung carcinoma have common histogenetical characteristics with mucous or Clara cells. Of the bronchial gland tumors, R-binder could be detected in a mucoepidermoid carcinoma but not in adenoid cystic carcinomas. Epithelial components in both pulmonary blastomas and hamartomas showed a reactivity for R-binder, suggesting that these tumors contained components composed of cells with bronchiolar cell differentiation. The immunohistochemical examination of lung tumors, using anti-R-binder antibody, may have some implications in the cell differentiation of lung tumors.

Differential effects of glucocorticoid on expression of surfactant proteins in a human lung adenocarcinoma cell line

Synthesis of pulmonary surfactant-associated glycoproteins of Mr 28,000-36,000 (SP-A) and Mr 42,000-46,000 (proSP-B) has been identified in a continuous cell line derived from a human lung adenocarcinoma. SP-A was detected by immunoblot analysis, ELISA assay and by [35S]methionine labelling of the cells. SP-A was secreted into the media as an endoglycosidase F sensitive glycoprotein which co-migrated with the isoforms of SP-A identified in human lavage fluid by 2D-IEF-SDS-PAGE. Hybridization of cellular RNA with SP-A-specific cDNA identified an abundant 2.2 kb mRNA species, identical to that observed in human lung. SP-A RNA and protein content were markedly inhibited by dexamethasone in a dose-dependent fashion. Under identical culture conditions, synthesis of a distinct surfactant protein, SP-B, was markedly stimulated by the glucocorticoid. The SP-B precursor was secreted into the media as heterogeneous Mr 42,000-46,000 protein, pI 4.6-5.1, and was sensitive to endoglycosidase F. Synthesis of proSP-B was enhanced by the glucocorticoid in a dose-dependent fashion and was associated with increased SP-B mRNA of 2.0 kb detected by Northern blot analysis. The cell line secreted proSP-B as Mr 42,000-46,000 glycosylated protein and did not process the precursor to the Mr 7000-8000 surfactant peptide. In summary, a human adenocarcinoma cell line has been identified which synthesizes and secretes two surfactant-associated proteins, SP-A and proSP-B. Glucocorticoid enhanced SP-B but inhibited SP-A expression in this cell line. The identification of a continuous cell line secreting surfactant proteins may be useful in the study of synthesis and secretion of these important proteins and for production of the proteins for clinical uses.

Immunohistochemical localization of pulmonary surfactant apoproteins in various lung tumors. Special reference to nonmucus producing lung adenocarcinomas

Eighty-nine primary lung carcinomas and 23 metastatic lung tumors were immunohistochemically studied for the expression of pulmonary surfactant apoproteins, by using monoclonal (PE-10) and polyclonal antibodies. Surfactant apoprotein was demonstrated in the cytoplasm and/or nuclear inclusion bodies of only primary lung adenocarcinomas (36 of 75 cases), not in any other histologic type of primary lung carcinoma or in metastatic lung tumors. In primary lung adenocarcinoma, although typical type II pneumocyte type adenocarcinoma was not included in the current series, the majority of surfactant apoprotein-positive single cell type tumors were of the Clara cell type, with a single bronchial surface epithelial cell type, according to the light microscopic subclassification of adenocarcinoma cells. The Clara cell type adenocarcinomas could at times be distinguished only with difficulty from adenocarcinoma of type II pneumocyte type. Normal and hyperplastic type II pneumocytes were of course positive for surfactant apoprotein in the cytoplasm. However, none of the positive cells could definitely be identified as Clara cells in non-neoplastic lungs. The findings obtained in this study indicate that surfactant apoprotein is a good marker to distinguish adenocarcinoma of the lung from other histologic types of lung cancer and from neoplasms metastatic to the lung, and that type II pneumocytes and Clara cells, non-neoplastic and neoplastic, are morphologically and functionally closely related and might belong to the same cell lineage.