Thomas, Charles F.

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a rare, but increasingly recognized entity that primarily affects middle-aged and elderly women. It is characterized by abnormal proliferation of pulmonary neuroendocrine cells (PNECs) and is considered a preinvasive lesion for carcinoid tumorlets/tumors. Sometimes, DIPNECH is accompanied by constrictive bronchiolitis which usually manifests as chronic cough and/or dyspnea, along with airflow limitation on spirometry. The telltale imaging sign of DIPNECH is the presence of multiple noncalcified pulmonary nodules and mosaic attenuation on CT. However, these clinico-radiologic features of DIPNECH are characteristic but nonspecific; thus, histopathologic confirmation is usually necessary. DIPNECH has an indolent course and only rarely leads to respiratory failure or death; progression to overt neuroendocrine tumor (carcinoid) of the lung occurs in a minority of patients. Of available therapies, somatostatin analogs and mechanistic target of rapamycin inhibitors are the most promising. In this review, we provide an update regarding the diagnosis and management of DIPNECH and describe critical gaps in our understanding of this entity, including the central terms ‘diffuse’ and ‘idiopathic.’ We also summarize the inconsistencies in definitions employed by recent studies and discuss the pitfalls of the DIPNECH definitions proposed by the World Health Organization in 2021. In this context, we propose an objective and reproducible radio-pathologic case definition intended for implementation in the research realm and seeks to enhance homogeneity across cohorts. Furthermore, we discuss aspects of PNECs biology which suggest that PNEC hyperplasia may contribute to the pathogenesis of phenotypes of lung disease aside from constrictive bronchiolitis and carcinoid tumorlets/tumors. Finally, we steer attention to some of the most pressing and impactful research questions awaiting to be unraveled.

Lung cancer is the leading cause of cancer‐related death inthe United States. Pulmonary typical carcinoid (TC) cancers are part of a spectrum of neuroendocrine lung cancers which includes small cell lung cancer (SCLC). Besides surgery, there are limited treatment options available for patients with these cancers, emphasizing the need for the development of new treatments. The c‐erbB family of receptor tyrosine kinases (ErbB1‐4) mediate cellular responses to growth factors and interact with downstream signaling pathways to promote tumorigenesis through abnormal cell proliferation. ErbB1 (EGFR) has received considerable attention in NSCLC since somatic mutations in the tyrosine kinase domain correlated with responsiveness to gefitinib. In NSCLC, breast, and ovarian cancer, ErbB2/ErbB3 heterodimers have been found to be expressed and signal to downstream pathways such as ERK. ErbB4 has been shown to promote proliferation or differentiation of neural tumors (ependymoma, gliomas, and meningiomas), ovarian cancer, and osteosarcoma. We recently examined the expression of ErbB receptors on TC cancers by quantitative real‐time RT‐PCR and immunoblotting. TCs have high expression of ErbB3 with moderate expression of ErbB1 and ErbB4 and lack expression of ErbB2. This contrasts with atypical carcinoids and SCLC which have high expression of ErbB4 with minimal expression of ErbB3 and lack expression of ErbB1 and ErbB2. We believe that investigation of ErbB signaling in pulmonary carcinoids will lead to new insights into the biology of these cancers, the understanding of which could lead to the development of novel treatments. Supported by funds from Mayo Foundation.

The cellular differentiation of Pneumocystis carinii (PC) from the trophic forms to the multinucleated cyst is critical to understand the pathogenesis of this fungus. Still the mechanism of life cycle regulation is not well known. In fungi closely related to PC, a mitogen‐activated protein kinase (MAPK) cascade regulates these processes. Conjugation between two haploid cells occurs after pheromones bind to their respective pheromone receptors on cells of opposite mating types. We previously reported a functional analysis of the PCSTE3 pheromone receptor of PC, and now we report characteristics of the cognate receptor, PCSTE2. We cloned the full‐length 1065‐bp cDNA for PCSTE2, of which the translated open‐reading frame encodes a protein of 354 amino acids with greatest homology to the fungal pheromone receptors from S. cerevisiae Ste2 and S. pombe Mam2. Computer prediction modeling of PCSTE2 reveals seven transmembrane domains characteristic of fungal pheromone receptors. Similar to the S. cerevisiae alpha factor receptor Ste2, PCSTE2 has three extracellular domains implicated in ligand binding. An antibody made against the extracellular domain of PCSTE2 identified PCSTE2 receptor expression on a subpopulation of PC organisms in infected rat lung tissue but not normal uninfected tissue. We expressed PCSTE2 in S. cerevisiae Ste2 knockout yeast for functional characterization. Our identification of both PCSTE2 and PCSTE3 pheromone receptors may help to elucidate mechanisms of PC life cycle regulation and potential new therapeutics for treating PC pneumonia through alterations of MAPK signaling. Supported by NIH grant 2R01 AI‐48409 to CFT.

e19013 Background: Mutation profiling to assess for potentially druggable mutations in NSCLC is being offered at an increasing number of cancer centers throughout North America and internationally. Although data continue to accumulate for the potential value of mutation testing in designing chemotherapeutic regimens, the treatment impact of obtaining information beyond assessment of EGFR and ALK status remains unclear. How best to obtain and clinically utilize these data, including information from exome and whole genome sequencing, also remains unclear. Methods: Patients were reviewed electronically in a multidisciplinary conference regarding indications for testing and results of mutation profiling from various methods, including the mass-spec based LungCarta test, targeted NexGen sequencing, exome, and whole genome sequencing. Outcomes of the multidisciplinary review were communicated back to treating physicians. Results: Mutation testing was performed on 200 patients using a variety of approaches. The majority (>150) were surgically resected stage I and II tumors. Mutations in at least 1 major cancer driver gene, including EGFR, KRAS, MET, BRAF and PIK3CA, were found in 47% of all patients tested. EGFR mutations were present in 14.8% of patients tested, KRAS 21.3%, BRAF 2.6%, PIK3CA 3.2%, and MET 4.5%. A total of 8 patients underwent either exome or whole genome sequencing. A limited number of patients (<10) had mutation results that impacted treatment decisions from this cohort. Conclusions: Mutation profiling can influence treatment decisions in NSCLC, but at a low frequency. The role of exome and or whole genome sequencing for patients with NSCLC is evolving and remains undefined.

ABSTRACT Pneumocystis carinii is an ascomycete phylogenetically related to Schizosaccharomyces pombe . Little is known about gene regulation in P. carinii . The removal of introns from pre-mRNA requires spliceosomal recognition of the intron-exon boundary. In S. pombe and higher eukaryotes, this boundary and a branch site within the intron are conserved. We recently demonstrated that P. carinii cdc2 cDNA can complement S. pombe containing conditional mutations of cdc2 , an essential gene involved in cell cycle regulation. We next tested whether P. carinii genomic cdc2 (with six introns) could also complement S. pombe cdc2 mutants and found genomic sequences incapable of this activity. Reverse transcriptase PCR confirmed the inability of the S. pombe cdc2 mutants to splice the P. carinii genomic cdc2 . Analysis of 83 introns from 19 P. carinii protein-encoding genes demonstrated that the sequence GTWWDW functions as a donor consensus in P. carinii , whereas YAG serves as an acceptor consensus. These sequences are similar in S. pombe ; however, a branch site sequence was not found in the P. carinii genes studied.

Abstract Purpose: Pulmonary carcinoid tumors account for up to 5% of all lung malignancies in adults, comprise 30% of all carcinoid malignancies, and are defined histologically as typical carcinoid (TC) and atypical carcinoid (AC) tumors. The role of specific genomic alterations in the pathogenesis of pulmonary carcinoid tumors remains poorly understood. We sought to identify genomic alterations and pathways that are deregulated in these tumors to find novel therapeutic targets for pulmonary carcinoid tumors. Experimental Design: We performed integrated genomic analysis of carcinoid tumors comprising whole genome and exome sequencing, mRNA expression profiling and SNP genotyping of specimens from normal lung, TC and AC, and small cell lung carcinoma (SCLC) to fully represent the lung neuroendocrine tumor spectrum. Results: Analysis of sequencing data found recurrent mutations in cancer genes including ATP1A2, CNNM1, MACF1, RAB38, NF1, RAD51C, TAF1L, EPHB2, POLR3B, and AGFG1. The mutated genes are involved in biological processes including cellular metabolism, cell division cycle, cell death, apoptosis, and immune regulation. The top most significantly mutated genes were TMEM41B, DEFB127, WDYHV1, and TBPL1. Pathway analysis of significantly mutated and cancer driver genes implicated MAPK/ERK and amyloid beta precursor protein (APP) pathways whereas analysis of CNV and gene expression data suggested deregulation of the NF-κB and MAPK/ERK pathways. The mutation signature was predominantly C&gt;T and T&gt;C transitions with a minor contribution of T&gt;G transversions. Conclusions: This study identified mutated genes affecting cancer relevant pathways and biological processes that could provide opportunities for developing targeted therapies for pulmonary carcinoid tumors. Clin Cancer Res; 24(7); 1691–704. ©2018 AACR.

The pathogenic fungus Pneumocystis carinii causes severe pneumonia in patients with impaired immunity, particularly patients with acquired immunodeficiency syndrome. The life cycle of P. carinii is poorly understood, and the inability to continuously culture P. carinii is a major limitation in understanding its cell biology. In fungi homologous to P. carinii, pheromone mating factors signal through a mitogen-activated protein kinase (MAPK) signal transduction cascade, resulting in mitotic cell cycle arrest and entry into a pathway of conjugation, cellular differentiation, and proliferation. Using degenerate PCR and library screening, we have identified a MAPK cDNA in P. carinii that is highly homologous to fungal MAPKs involved in the pheromone mating signal transduction cascade, and we demonstrate MAPK activity in P. carinii lysates with a specific antiserum derived from the translated P. carinii MAPK cDNA sequence.

Introduction. We investigated the expression of microRNAs and mRNAs in pleural tissues from patients with either malignant pleural mesothelioma or benign asbestos-related pleural effusion.Methods. Fresh frozen tissues from a total of 18 malignant pleural mesothelioma and 6 benign asbestos-related pleural effusion patients were studied. Expression profiling of mRNA and microRNA was performed using standard protocols.Results. We discovered significant upregulation of multiple microRNAs in malignant pleural mesothelioma compared to benign asbestos-related pleural effusion. Hsa-miR-484, hsa-miR-320, hsa-let-7a, and hsa-miR-125a-5p were able to discriminate malignant from benign disease. Dynamically regulated mRNAs were also identified. MET was the most highly overexpressed gene in malignant pleural mesothelioma compared to benign asbestos-related pleural effusion. Integrated analyses examining microRNA-mRNA interactions suggested multiple altered targets within the Notch signaling pathway.Conclusions. Specific microRNAs and mRNAs may have diagnostic utility in differentiating patients with malignant pleural mesothelioma from benign asbestos-related pleural effusion. These studies may be particularly helpful in patients who reside in a region with a high incidence of mesothelioma.