Abnormal Abundance of Senescent Fibroblasts in the Tumor Stroma of Non-Small Cell Lung Cancer Patients

Abstract Although permanent cell cycle arrest through senescence has been previously regarded as a protective mechanism against tumor growth, there is growing evidence that the abnormal abundance of senescent cells observed in the stroma of some types of cancer may support cancer progression. However, the presence of senescent cells in the tumor stroma of non-small cell lung cancer (NSCLC), which is a major cause of cancer death in western countries, remains poorly defined. To fill this gap of knowledge, we set up a bank of primary human lung fibroblasts isolated from both tumor-free regions and tumors of NSCLC patients diagnosed with adenocarcinoma (ADC, n=5), squamous cell carcinoma (SCC, n=5) or large cell carcinoma (LCC, n=2) histological subtypes. Tumor-associated fibroblasts (TAFs) or patient-matched control fibroblasts (NTAFs) were seeded in collagen-coated culture dishes in culture media supplemented with 10% serum for 3 days. The presence of senescent cells was assessed by examining senescent associated signatures including increased spreading, decreased proliferation, and the positive response to the beta-galactosidase (beta-gal) assay. The beta-gal assay was negative in >90% of NTAFs (11/12). Likewise, TAFs from either ADC or SCC were negative for beta-gal assay in 80% of the patients examined (4/5), whereas <10% of cells were positive for the beta-gal assay in the remaining 20% of patients. In contrast, beta-gal positive TAFs were observed in 100% of LCC patients (2/2), with an average of ∼50% positive TAFs per patient. In agreement with these findings, LCC TAFs were poorly or non-responsive to serum stimulation in terms of cell cycle progression as assessed by flow cytometry, unlike patient-matched LCC NTAFs. Moreover, LCC TAFs exhibited a high percentage of largely spread fibroblasts, which is commonly associated with the senescent phenotype. These preliminary results strongly suggest that the senescent phenotype is absent in normal fibroblasts, and abnormally and specifically present in lung fibroblasts from the tumor stroma of LCC patients, therefore revealing the presence of NSCLC-subtype specific alterations in the tumor microenvironment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1482. doi:1538-7445.AM2012-1482