Comprehensive Genomic and Transcriptomic Analysis of Sclerosing Pneumocytoma

Sclerosing pneumocytoma is a rare and distinct lung neoplasm whose histogenesis and molecular alterations are the subject of ongoing research. Our recent study revealed that AKT1 internal tandem duplications (ITD), point mutations, and short indels were present in almost all tested sclerosing pneumocytomas, suggesting that AKT1 mutations are a major driving oncogenic event in this tumor. Although the pathogenic role of AKT1 point mutations is well established, the significance of AKT1 ITD in oncogenesis remains largely unexplored. We conducted comprehensive genomic and transcriptomic analyses of sclerosing pneumocytoma to address this knowledge gap. RNA-sequencing data from 23 tumors and whole-exome sequencing data from 44 tumors were used to obtain insights into their genetic and transcriptomic profiles. Our analysis revealed a high degree of genetic and transcriptomic similarity between tumors carrying AKT1 ITD and those with AKT1 point mutations. Mutational signature analysis revealed COSMIC signatures 1 and 5 as the prevailing signatures of sclerosing pneumocytoma, associated with the spontaneous deamination of 5-methylcytosine and an unknown etiology, respectively. RNA-sequencing data analysis revealed that the sclerosing pneumocytoma gene expression profile is characterized by activation of the PI3K/AKT/mTOR pathway, which exhibits significant similarity between tumors harboring AKT1 ITD and those with AKT1 point mutations. Notably, an upregulation of SOX9, a transcription factor known for its involvement in fetal lung development, was observed in sclerosing pneumocytoma. Specifically, SOX9 expression was prominent in the round cell component, whereas it was relatively lower in the surface cell component of the tumor. To the best of our knowledge, this is the first comprehensive investigation of the genomic and transcriptomic characteristics of sclerosing pneumocytoma. Results of the present study provide insights into the molecular attributes of sclerosing pneumocytoma and a basis for future studies of this enigmatic tumor.

Cytogenetic study of a pulmonary sclerosing hemangioma

Pulmonary sclerosing hemangioma (PSH) is an uncommon benign tumor that presents as a solitary asymptomatic and slow-growing nodule. It occurs in both young and old persons; peak incidence is in the fifth decade. Both sexes are affected by this tumor, but women more frequently than men. On histological examination, PSH shows prominent sclerotization and vascularization of the tissue. Recent studies conclude that PSH derives from type II pneumocytes, but the potential for progression and histogenesis remains controversial. We report a case of pulmonary sclerosing hemangioma in a 61-year-old woman with a neoplastic node 1 cm in diameter. The karyotype was 46,XX,t(8;18),der(14;15),+14 in all the cells analyzed. PTEN (10q23) and IgH (14q32) probes were analyzed in interphase nuclei and paraffin-embedded tissues of tumor cells. These chromosome abnormalities could provide information about the relationship of genetic changes to the biological properties of sclerosing hemangioma tumors.

Microsatellite and EGFR, HER2 and K-RAS analyses in sclerosing hemangioma of the lung

Sclerosing hemangioma (SH) is an uncommon pulmonary tumor thought to derive from primitive respiratory epithelium consisting of 2 cell populations (cuboidal surface and polygonal stromal cells) and sharing some clinical characteristics (frequent occurrence in nonsmoking women of Asian ethnicity) with bronchioloalveolar carcinoma with which it has been suggested a possible common origin. We investigated 11 cases of SH by immunohistochemistry, fluorescence in situ hybridization, and polymerase chain reaction-based microsatellite and mutational analyses with particular emphasis on possible alterations of microsatellite loci located at tumor suppressor genes (FHIT, p16, Rb, and p53) involved in lung adenocarcinoma genesis and EGFR, HER2, and K-RAS genes. Although EGFR expression was observed in all tested cases, none showed HER2 immunostaining. Fluorescence in situ hybridization and mutational analysis of EGFR and HER2 and also K-RAS sequencing did not reveal molecular alterations, whereas allelic losses at p16 and Rb loci (4 and 2 out of 9 tested cases, respectively) with an identical microsatellite allelic loss pattern in both cuboidal and polygonal cells were observed. The finding of microsatellite alterations in chromosomal regions related to genes deeply involved in early stage lung adenocarcinoma could suggest a possible link between SH and bronchioloalveolar carcinoma, but tumor pathway promoted by EGFR, HER2, and K-RAS does not represent a common molecular mechanism of tumorigenesis. Microsatellite alterations identified in cuboidal and polygonal cells further confirm the clonal and neoplastic nature of both components of SH.

Gene expression and clonality analysis of the androgen receptor and phosphoglycerate kinase genes in polygonal cells and cuboidal cells in so-called pulmonary sclerosing hemangioma

The histogenesis of polygonal cells and cuboidal cells in so-called pulmonary sclerosing hemangioma remains unclear. To understand their histogenesis, polygonal and cuboidal cells were obtained from pulmonary sclerosing hemangioma tissue using a laser capture microdissection technique. Genomic DNA and total RNA were extracted and mRNA levels of cytokeratin, epithelial membrane antigen, vimentin, surfactant protein B, thyroid transcription factor-1, synaptophysin, and chromogranin-A were analyzed by RT-PCR. DNA was digested with the methylation-sensitive enzymes HhaI or HpaII, followed by nested PCR of the androgen receptor and phosphoglycerate kinase genes. Samples with polymorphisms were identified and a clonality analysis was performed. The cytokeratin, epithelial membrane antigen, and surfactant protein B genes were clearly expressed in cuboidal cells, while the vimentin and synaptophysin genes were clearly expressed and the epithelial membrane antigen gene was weakly expressed in polygonal cells. Thyroid transcription factor-1 was expressed in both cell types, while neither cell type expressed chromogranin-A. Clonality analysis showed the same loss of allele in both cell types (clonality ratio=0) or an unbalanced methylation pattern (clonality ratio<0.25). Polygonal and cuboidal cells in pulmonary sclerosing hemangioma exhibited a uniform pattern of monoclonality, indicating that both cell types are highly likely to originate from a common precursor. The differences in their morphological phenotype might result from their different mature status.

p53 protein expression and genetic mutation in two primary cell types in pulmonary sclerosing haemangioma

AIMS

To investigate the significance of p53 protein expression and genetic mutations in two primary cell types in pulmonary sclerosing haemangioma (PSH).

METHODS

p53 protein expression in polygonal cells and cuboidal cells in 19 patients with PSH was detected using immunohistochemistry. The two major cell types were captured using laser capture microdissection technology. Mutations in the p53 gene (exons 5-8) were examined using single-stranded conformation polymorphism and DNA sequencing analysis.

RESULTS

p53 protein expression and gene mutations were observed in 15.8% (3/19) of cases. In these cases, p53 protein was expressed in the nucleus of both cell types, with higher expression levels and mutation rates in polygonal cells than in surface cuboidal cells. Two cases showed mutation only in the polygonal cells, while one case showed double (separate) mutations in both the polygonal and cuboidal cells.

CONCLUSIONS

p53 mutation was exhibited in PSH. The mutation rate in polygonal cells was higher than that in surface cuboidal cells.

Frequent nuclear expression of beta-catenin protein but rare beta-catenin mutation in pulmonary sclerosing haemangioma

BACKGROUND

Pulmonary sclerosing haemangioma (PSH) is an uncommon tumour that is composed of glandular/papillary lining cells and polygonal cells. The biological behaviour of this tumour has been investigated; however, the molecular pathogenesis of PSH remains unknown.

AIMS

To characterise the role of the Wnt/beta-catenin pathway in the genesis of PSH.

METHODS

37 PSH samples were investigated immunohistochemically for detection of the beta-catenin protein and direct sequencing of exon 3 of the beta-catenin gene.

RESULTS

Nuclear expression of beta-catenin was found in the lining component of 23 tumours (62%) and in the polygonal component of 11 tumours (30%). The expression of beta-catenin was stronger in the lining component, but weaker in the polygonal component. Interestingly, all the tumours with expression of beta-catenin in the polygonal component also expressed beta-catenin in the lining component. However, mutation of exon 3 of the beta-catenin gene was detected in only one tumour that expressed nuclear beta-catenin in lining and polygonal components.

CONCLUSIONS

The Wnt/beta-catenin pathway is involved in the genesis of PSH, but mutation of exon 3 of the beta-catenin gene rarely contributes to the activation of the Wnt/beta-catenin pathway in PSH.

[Study of androgen receptor and phosphoglycerate kinase gene polymorphism in major cellular components of the so-called pulmonary sclerosing hemangioma]

OBJECTIVE

To study the clonality of polygonal cells and surface cuboidal cells in the so-called pulmonary sclerosing hemangioma (PSH).

METHODS

17 female surgically resected PSH were found. The polygonal cells and surface cuboidal cells of the 17 PSH cases were microdissected from routine hematoxylin and eosin-stained sections. Genomic DNA was extracted, pretreated through incubation with methylation-sensitive restrictive endonuclease HhaI or HpaII, and amplified by nested polymerase chain reaction for X chromosome-linked androgen receptor (AR) and phosphoglycerate kinase (PGK) genes. The length polymorphism of AR gene was demonstrated by denaturing polyacrylamide gel electrophoresis and silver staining. The PGK gene products were treated with Bst XI and resolved on agarose gel.

RESULTS

Amongst the 17 female cases of PSH, 15 samples were successfully amplified for AR and PGK genes. The rates of polymorphism were 53% (8/15) and 27% (4/15) for AR and PGK genes respectively. Polygonal cells and surface cuboidal cells of 10 cases which were suitable for clonality study, showed the same loss of alleles (clonality ratio = 0) or unbalanced methylation pattern (clonality ratio < 0.25).

CONCLUSIONS

The polygonal cells and surface cuboidal cells in PSH demonstrate patterns of monoclonal proliferation, indicating that both represent true neoplastic cells.

Expression of the estrogen receptor β in 37 surgically treated pulmonary sclerosing hemangiomas in comparison with non–small cell lung carcinomas

Sclerosing hemangioma (SH) of the lung is an uncommon tumor with a predilection for middle-aged women. This special phenomenon prompted us to examine SH for the expression of ERalpha (human estrogen receptor) and ERbeta (a second isoform of estrogen receptor). To investigate the staining pattern of these tumors, we also stained lung tissues from patients with non-small cell lung carcinomas and nonneoplastic type II pneumocytes for comparison. Thirty-seven pulmonary SHs and 301 non-small cell lung cancers specimens were explored. Expression of ERalpha and ERbeta was immunohistochemically measured. The overall frequency of overexpression for ERbeta was 91.9%. It was detected in both female (in 91.4% of 35 cases) and male (in 100.0% of 2 tumors from men) patients. There was ERbeta overexpression in all 9 tumors of solid pattern, 6 of 7 tumors of papillary pattern, all 4 tumors of sclerotic pattern, 12 of 13 tumors of hemorrhagic pattern, and 3 of 4 tumors of mixed pattern. The staining pattern of the neoplastic cells of the SH was similar to that of type II pneumocytes adjacent to the tumor rather than that of non-small cell lung cancers, in which the frequency of ERbeta overexpression was 45.8%. However, there was no ERalpha detectable in these neoplasms. Estrogen receptor beta overexpression is very frequent in pulmonary SHs, which is similar to that of alveolar cells but quite different from non-small cell carcinoma.

["Pneumocytoma" or "sclerosing hemangioma": histogenetic aspects of a rare tumor of the lung]

Aspects of histogenesis and nomenclature of so called "sclerosing hemangioma" of the lung (WHO 1999) are discussed and compared with immunohistochemical findings in eight examined operation specimen. The lesion is characterised by the presence of typical surface cells, which can be related to type II pneumocytes. Progesterone-receptor positive stromal cells may derive from primitive mesenchymal cells. Endothelial proveniance of tumor cells could not be confirmed by immunohistochemistry. Therefore, this rare usually benign pulmonary neoplasm should be entitled "pneumocytoma" analogous to the suggestion of several other authors.

Loss of heterozygosity patterns of sclerosing hemangioma of the lung and bronchioloalveolar carcinoma indicate a similar molecular pathogenesis

CONTEXT

The histogenesis and origin of sclerosing hemangioma (SH) of lung were uncertain for many years. Many immunohistochemical, ultrastructural, and recent molecular studies support the hypothesis that SH is a neoplasm originating from the cells of the terminal lobular unit, similar to the nonmucinous variant of bronchioloalveolar carcinoma (BAC). Most cases of SH are benign, but they can metastasize to the regional lymph nodes.

OBJECTIVE

To compare the patterns of allelic loss of tumor suppressor genes in SH and BAC by microdissection-based genotypic analysis.

DESIGN

Microdissection-based loss of heterozygosity analysis of 9 cases of SH and 14 cases of BAC, using a panel of 7 polymorphic microsatellite markers located on 1p, 5q, 9p, 10q, and 17p. Microsatellite marker and chromosomal arm-based fractional allelic loss (FAL) were calculated in each case.

RESULTS

Our results showed similar patterns of allelic loss between the 2 groups of tumors on an individual case basis. Chromosomal arms 5q and 10q showed frequent allelic loss in SH (66.7% and 62.5%, respectively), whereas in BAC, chromosomal arm 17p (52.6%) was frequently affected. A statistically significant difference in allelic loss between SH and BAC was located only on chromosomal arm 5q (P =.04). Microsatellite marker D5S615 was significantly more frequently affected in SH than in BAC (66.7% vs 28.6%; P =.04).

CONCLUSION

Our molecular data support the hypothesis of common origin of SH and BAC. A putative tumor suppressor gene that might play a role in tumorigenesis of SH may be located on the chromosomal arm 5q.