Abstract 2202: Contiguous airway sampling for basal cell isolation

Abstract

Abstract Introduction: Airway basal cells isolated from histologically normal epithelium in current and former smokers demonstrate a significantly higher mutation burden than those in never-smokers. However, a proportion of basal cells with lower (“near normal”) mutation burden are observed, which show preferential expansion in response to smoking cessation(1). We believe this expansion represents a “cancer protective” process, reducing the risk of future malignancy. However, mechanisms determining the dynamic balance of high versus low mutant basal cells throughout the bronchial tree are unclear. We have developed protocols that enable systematic scanning of airway epithelium in resected lung specimens, through which we aim to elucidate the mutation burden and spatial clonal architecture across contiguous regions of normal epithelium through the bronchial tree. Study design: 5-10 current or former smokers undergoing curative lobectomy for peripheral lung cancer with histologically normal airways will be consented to the study. To date, two participants have donated their samples. Fresh lobectomies were collected at the point of resection and kept on wet ice until pathological examination. All samples undergo examination within 1 hour of resection. The lobe is orientated, and the tumour and segmental bronchi identified. A sterile metal cannula is inserted through the airway lumen and sterile pathology scissors are used to carefully isolate the airways from the surrounding parenchyma. Upon macro-dissection, airway branches are immediately placed into transport media containing antibiotics. Samples are gently washed using transport media to remove residual blood, then sectioned into 1 cm3 segments, which are orientated, embedded and frozen in room-temperature Optimal Cutting Temperature compound. An 8 μM section is cut and stained with haematoxylin and eosin from each block immediately after a “full-face” tissue confirmation is observed.These will be used as guiding slides for laser capture microdissection of the regions of epithelium prior to downstream sequencing pathway. Conclusion: We have developed a pathological approach in which we can define somatic mutations in normal epithelium along the bronchial tree. We will use these data to determine basal cell clonal relationships and interpret these in a spatial context, creating a more detailed map of the smoking-induced changes that occur in the airway epithelium and how these may contribute to early carcinogenesis.