Molecular biology of lung cancer

Background: The 2013 American Thoracic Society/European Respiratory Society Statement on the classification of the idiopathic interstitial pneumonias described 6 major and 2 rare subtypes of idiopathic interstitial pneumonia, as well as recognising unclassifiable disease. Objective: The objective of this statement is to update the 2013 classification of interstitial pneumonia. Methods: Five co-chairs identified a committee of 32 experts in the field as well as two individuals with lived experience. Creation of the document was supported by a series of video meetings, first including the full committee and then subgroups assigned to draft specific sections of the document. The classification scheme was developed by consensus. Results: The multidisciplinary committee of experts identified four major advances to the classification of interstitial pneumonia: (1) expansion beyond idiopathic interstitial pneumonias to also include secondary causes; (2) identification of new subcategories and updated terms, including addition of bronchiolocentric interstitial pneumonia as a major pattern as well as changing from acute interstitial pneumonia to idiopathic diffuse alveolar damage and desquamative interstitial pneumonia to alveolar macrophage pneumonia; (3) subclassification of interstitial and alveolar filling disorders, with interstitial disorders further subclassified as fibrotic versus non-fibrotic; and (4) consideration of diagnostic confidence in patient evaluation and management. The committee also provided a comprehensive update on the status of potential molecular tools and identified future research priorities. Conclusions: This update builds upon the previous classification approach by describing major advances in the classification of interstitial pneumonia over the last decade.

Purpose: Reliable and reproducible methods for identifying PD-L1 expression on tumor cells are necessary to identify responders to anti–PD-1 therapy. We tested the reproducibility of the assessment of PD-L1 expression in non–small cell lung cancer (NSCLC) tissue samples by pathologists. Experimental Design: NSCLC samples were stained with PD-L1 22C3 pharmDx kit using the Dako Autostainer Link 48 Platform. Two sample sets of 60 samples each were designed to assess inter- and intraobserver reproducibility considering two cut points for positivity: 1% or 50% of PD-L1 stained tumor cells. A randomization process was used to obtain equal distribution of PD-L1 positive and negative samples within each sample set. Ten pathologists were randomly assigned to two subgroups. Subgroup 1 analyzed all samples on two consecutive days. Subgroup 2 performed the same assessments, except they received a 1-hour training session prior to the second assessment. Results: For intraobserver reproducibility, the overall percent agreement (OPA) was 89.7% [95% confidence interval (CI), 85.7–92.6] for the 1% cut point and 91.3% (95% CI, 87.6–94.0) for the 50% cut point. For interobserver reproducibility, OPA was 84.2% (95% CI, 82.8–85.5) for the 1% cut point and 81.9% (95% CI, 80.4–83.3) for the 50% cut point, and Cohen's κ coefficients were 0.68 (95% CI, 0.65–0.71) and 0.58 (95% CI, 0.55–0.62), respectively. The training was found to have no or very little impact on intra- or interobserver reproducibility. Conclusions: Pathologists reported good reproducibility at both 1% and 50% cut points. More adapted training could potentially increase reliability, in particular for samples with PD-L1 proportion, scores around 50%. Clin Cancer Res; 23(16); 4569–77. ©2017 AACR.

Rearrangements of anaplastic lymphoma kinase (ALK) gene in non-small cell lung cancer (NSCLC) define a molecular subgroup of tumors characterized clinically by sensitivity to ALK tyrosine kinase inhibitors such as crizotinib. Although ALK rearrangements may be detected by reverse transcriptase-PCR, immunohistochemistry or fluorescence in situ hybridization (FISH), the optimal clinical strategy for identifying ALK rearrangements in clinical samples remains to be determined. We evaluated immunohistochemistry using three different antibodies (ALK1, 5A4 and D5F3 clones) to detect ALK rearrangements and compared those with FISH. We report the frequency and clinicopathologic features of lung cancers harboring ALK translocations in 594 resected NSCLCs (470 adenocarcinomas; 83 squamous carcinomas, 26 large cell carcinomas and 15 other histological subtypes) using a tissue microarray approach. We identified an ALK gene rearrangement in 7/594 cases (1%) by FISH and all anti-ALK antibodies correctly identified the seven ALK-positive cases (100% sensitivity), although the intensity of staining was weak in some cases. These data indicate that the use of antibodies with high sensitivity and avidity to ALK may provide an effective pre-screening technique to complement the more expensive and labor-intensive approach of ALK FISH testing.

In this review, we summarise the function and structure of telomerase reverse transcriptase (TERT) in humans, including its regulation. The dysregulation of telomerase through TERT promoter mutations across a range of cancers is discussed. The molecular mechanism activated by TERT promoter mutations is outlined. Finally, the timing of TERT promoter mutations during carcinogenesis is reviewed in the context of their potential utility as clinical biomarkers of malignant transformation.