Abstract
RASSF1 gene methylation predicts longer disease-free survival (DFS) and overall survival (OS) in patients with early-stage non-small-cell lung cancer treated using paclitaxel-based neo-adjuvant chemotherapy compared to patients receiving a gemcitabine-based regimen, according to the randomized Phase 3 IFCT (Intergroupe Francophone de Cancérologie Thoracique)-0002 trial. To better understand these results, this study used four human bronchial epithelial cell (HBEC) models (HBEC-3, HBEC-3-RasV12, A549, and H1299) and modulated the expression of RASSF1A or YAP-1. Wound-healing, invasion, proliferation and apoptosis assays were then carried out and the expression of YAP-1 transcriptional targets was quantified using a quantitative polymerase chain reaction. This study reports herein that gemcitabine synergizes with RASSF1A, silencing to increase the IAP-2 expression, which in turn not only interferes with cell proliferation but also promotes cell migration. This contributes to the aggressive behavior of RASSF1A-depleted cells, as confirmed by a combined knockdown of IAP-2 and RASSF1A. Conversely, paclitaxel does not increase the IAP-2 expression but limits the invasiveness of RASSF1A-depleted cells, presumably by rescuing microtubule stabilization. Overall, these data provide a functional insight that supports the prognostic value of RASSF1 gene methylation on survival of early-stage lung cancer patients receiving perioperative paclitaxel-based treatment compared to gemcitabine-based treatment, identifying IAP-2 as a novel biomarker indicative of YAP-1-mediated modulation of chemo-sensitivity in lung cancer.
Highlights
Over the last few years, targeted therapy based on specific predictive biomarkers has improved both the survival rate and quality of life of cancer patients [1,2]
The control cells’ exposure to either paclitaxel or gemcitabine caused a significant increase in caspase 3/7 activities, cytochrome c release and DNA fragmentation after the cells were treated with chemotherapy (HBEC-3: Figure 1A,C,D; human bronchial epithelial cell (HBEC)-3 RasV12: Figure 1B–E; H1299: Figure S2A; and A549: Figure S2B, respectively)
This study showed, for the first time, that RASSF1A depletion reduces the ability of bronchial epithelial or lung cancer cells to undergo apoptosis via increasing IAP-2 protein expression and reducing apoptosis-related proteins
Summary
Over the last few years, targeted therapy based on specific predictive biomarkers has improved both the survival rate and quality of life of cancer patients [1,2]. Among the predictive biomarkers in patients with non-small-cell lung cancer (NSCLC), the promoter hyper-methylation of the tumor suppressor gene RASSF1A is still misused. A worse median OS was observed in patients with methylated RASSF1A treated with gemcitabine (30.3 months) compared to those treated with paclitaxel (70 months) [3]. These prognostic values of RASSF1A gene methylation were supported by data that demonstrated that RASSF1A restricts epithelial-mesenchymal transition (EMT) and cell invasion by controlling Yes-associated protein (YAP) nuclear shuttling and RhoB-regulated cytoskeletal remodeling process [4,5]. To be able to rationally develop enhanced treatment strategies, it is imperative to define whether RASSF1A depletion enhances sensibility to paclitaxel or, to the contrary, increases the patient’s resistance to gemcitabine-induced cell death
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