Preclinical and clinical impact of the GLI2 transcription factor in non-small cell lung cancer (NSCLC).

Abstract

e18537 Background: Components of the Hedgehog (Hh) signaling pathway are over-expressed in NSCLC. Hh signaling contributes to tumorigenesis in lung cancer and is under investigation as a therapeutic target. We assessed in vitro characteristics of the GLI2 transcription factor, a primary mediator of Hh signaling, in NSCLC tumorigenesis, and its prognostic impact in early stage NSCLC. Methods: Colony formation, growth in soft agar, and measurement of GLI2 RNA were assayed in A549 NSCLC cells. Changes in tumor growth and proliferation were evaluated using a two-sample t-test. The automated quantitative analysis system (AQUA) was used to assess protein expression of GLI2 in NSCLC specimens from 88 deceased patients (pts) with resected stages I and II NSCLC. Pts did not receive additional pre- or post-operative anti-cancer therapies. Pt age, sex, smoking history, histology, TNM stage, and type of resection were also collected. Progression-free survival (PFS) and overall survival (OS) were estimated per Kaplan-Meier; multivariate Cox proportional hazard analyses were used to determine if the GLI2 AQUA score was an independent prognostic factor. Results: GLI2 knockdown in A549 NSCLC cells using GLI2 shRNA resulted in inhibition of colony formation and in the anchorage-independent growth, compared to A549 cells with intact GLI2 function. Characteristics of our population included median age 73 (43-96), males 62.5%, smokers 96%, adenocarcinoma 46.6%, squamous cell histology 40.9%, and stage I 62.5%. GLI2 AQUA score was not associated with any clinical variable per Wilcoxon analyses. High GLI2 AQUA score was associated with shorter PFS (median PFS 8.6 mo [95% CI 7.0-10.7 mo]) compared to low GLI2 AQUA score (median PFS 17.2 mo [95% CI 15.8-22.6 mo], p=0.001), and with shorter OS (median OS 14.8 mo [95% CI 10.5-23.0 mo]), compared to low GLI2 score (median 25.9 mo [95% CI 20.2-35.7 mo], p<0.001), independent of clinical variables. Conclusions: The GLI2 transcription factor of Hh signaling impacts in vitro models of NSCLC tumorigenicity and is an independent negative prognostic factor in early stage disease. Hh signaling remains a worthwhile investigational therapeutic target in NSCLC.