Search

We have sequenced the genomes of 110 small cell lung cancers (SCLC), one of the deadliest human cancers. In nearly all the tumours analysed we found bi-allelic inactivation of TP53 and RB1, sometimes by complex genomic rearrangements. Two tumours with wild-type RB1 had evidence of chromothripsis leading to overexpression of cyclin D1 (encoded by the CCND1 gene), revealing an alternative mechanism of Rb1 deregulation. Thus, loss of the tumour suppressors TP53 and RB1 is obligatory in SCLC. We discovered somatic genomic rearrangements of TP73 that create an oncogenic version of this gene, TP73Δex2/3. In rare cases, SCLC tumours exhibited kinase gene mutations, providing a possible therapeutic opportunity for individual patients. Finally, we observed inactivating mutations in NOTCH family genes in 25% of human SCLC. Accordingly, activation of Notch signalling in a pre-clinical SCLC mouse model strikingly reduced the number of tumours and extended the survival of the mutant mice. Furthermore, neuroendocrine gene expression was abrogated by Notch activity in SCLC cells. This first comprehensive study of somatic genome alterations in SCLC uncovers several key biological processes and identifies candidate therapeutic targets in this highly lethal form of cancer.

Precision medicine depends on the accurate identification of actionable mutations in a tumor sample. It is unknown how heterogeneous the distribution of such mutations can be in a tumor. Morphological (i.e. histopathological) heterogeneity is well described in lung adenocarcinoma and has been specifically recognized in the most recent official clinico-pathological classification. The most predominant subtype present is now used to classify each lung adenocarcinoma. No molecular profile exists to explain the intratumoral differences in lung adenocarcinoma morphology, despite the consistently observed association between specific predominant subtypes and poorer survival. Given a recent proposal stratifying lung adenocarcinoma into subtypes of differing metastatic potential, we questioned the assumption that major mutations are present uniformly throughout tumors; especially those showing discrete different subtypes. We selected formalin-fixed paraffin embedded lung adenocarcinoma specimens that showed discrete areas of different subtypes, extracted subtype DNA samples from those areas and screened for mutations in hotspot regions of the EGFR, KRAS and BRAF genes using high resolution melting. Sanger sequencing was used to confirm all identified mutations. Chromogenic in situ hybridization (CISH) was used to identify mutant allele specific imbalances in tumors with EGFR mutations. Interestingly, we found that KRAS and BRAF mutations could be confined to morphological domains of higher grade. On the other hand, EGFR mutations were found through all histological subtypes in each tumor consistent with the driver status of this mutation. Intratumoral heterogeneity has major implications for tumorigenesis, chemoresistance and the role of histopathology in molecular screening for precision medicine. This study not only confirms that intratumoral mutational heterogeneity does occur, but also that it is associated with morphologically distinct regions in some tumors. From a practical perspective, small biopsies may not adequately represent a tumor's full mutational profile, particularly for later arising but prognostically important mutations such as those in the KRAS and BRAF genes.

Pulmonary carcinoids are rare neuroendocrine tumours of the lung. The molecular alterations underlying the pathogenesis of these tumours have not been systematically studied so far. Here we perform gene copy number analysis (n=54), genome/exome (n=44) and transcriptome (n=69) sequencing of pulmonary carcinoids and observe frequent mutations in chromatin-remodelling genes. Covalent histone modifiers and subunits of the SWI/SNF complex are mutated in 40 and 22.2% of the cases, respectively, with MEN1, PSIP1 and ARID1A being recurrently affected. In contrast to small-cell lung cancer and large-cell neuroendocrine lung tumours, TP53 and RB1 mutations are rare events, suggesting that pulmonary carcinoids are not early progenitor lesions of the highly aggressive lung neuroendocrine tumours but arise through independent cellular mechanisms. These data also suggest that inactivation of chromatin-remodelling genes is sufficient to drive transformation in pulmonary carcinoids.

Introduction: We investigated the relationship between predominant subtype, according to the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society International Multidisciplinary Lung Adenocarcinoma Classification; mutation status; and patient outcome in stage III (N2) lung adenocarcinoma., Methods: We identified 69 patients with stage III (N2) lung adenocarcinoma operated on with curative intent between 1993 and 2011 who had adequate tumor tissue for molecular analysis and adequate follow-up time for survival analysis. DNA was isolated and tested for mutations using Sequenom's OncoCarta Panel (v1.0; Sequenom, San Diego, CA)., Results: The majority of tumors were acinar (26 of 69 tumors; 38%), solid (24 of 69 tumors; 35%), and micropapillary predominant (13 of 69 tumors; 19%) subtypes. EGFR and KRAS mutations were identified in 17 of 59 tumors (29%) and 13 of 59 tumors (22%), respectively. EGFR mutations occurred most often in acinar (11 of 25 tumors; 44%) and micropapillary predominant tumors (five of 13 tumors; 38%) (p = 0.009), whereas KRAS mutations occurred most often in solid predominant tumors (nine of 21 tumors; 43%) (p = 0.016). Patients with acinar predominant tumors had significantly improved overall survival compared with those with non-acinar predominant tumors (hazard ratio: 0.45; 95% confidence interval: 0.22-0.91; p = 0.026), which remained significant after adjustment for EGFR status, T-stage, sex, and age. Patients with EGFR-mutant micropapillary predominant tumors had similar survival to those with EGFR-mutant acinar predominant tumors. The predominant subtype in the primary tumor was most often seen in the N2 node in micropapillary and solid predominant tumors but not in acinar predominant tumors., Conclusions: The predominant subtype in the primary tumor was associated with overall survival in resected stage III (N2) lung adenocarcinoma and was independent of mutation status. Histologic subtyping provides important prognostic information and potentially molecular correlates.