Platelet-Activating Factor-Receptor Signaling Mediates Targeted Therapies-Induced Microvesicle Particles Release in Lung Cancer Cells.

Shreepa J Chauhan,Anita Thyagarajan,Yanfang Chen,Ravi P Sahu,Jeffrey B Travers

doi:10.3390/ijms21228517

Shreepa J Chauhan, Anita Thyagarajan + Show 3 more

Open Access

https://doi.org/10.3390/ijms21228517

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Abstract

Microvesicle particles (MVP) secreted by a variety of cell types in response to reactive oxygen species (ROS)-generating pro-oxidative stressors have been implicated in modifying the cellular responses including the sensitivity to therapeutic agents. Our previous studies have shown that expression of a G-protein coupled, platelet-activating factor-receptor (PAFR) pathway plays critical roles in pro-oxidative stressors-mediated cancer growth and MVP release. As most therapeutic agents act as pro-oxidative stressors, the current studies were designed to determine the role of the PAFR signaling in targeted therapies (i.e., gefitinib and erlotinib)-mediated MVP release and underlying mechanisms using PAFR-expressing human A549 and H1299 non-small cell lung cancer (NSCLC) cell lines. Our studies demonstrate that both gefitinib and erlotinib generate ROS in a dose-dependent manner in a process blocked by antioxidant and PAFR antagonist, verifying their pro-oxidative stressor’s ability, and the role of the PAFR in this effect. We observed that these targeted therapies induce MVP release in a dose- and time-dependent manner, similar to a PAFR-agonist, carbamoyl-PAF (CPAF), and PAFR-independent agonist, phorbol myristate acetate (PMA), used as positive controls. To confirm the PAFR dependency, we demonstrate that siRNA-mediated PAFR knockdown or PAFR antagonist significantly blocked only targeted therapies- and CPAF-mediated but not PMA-induced MVP release. The use of pharmacologic inhibitor strategy suggested the involvement of the lipid ceramide-generating enzyme, acid sphingomyelinase (aSMase) in MVP biogenesis, and observed that regardless of the stimuli used, aSMase inhibition significantly blocked MVP release. As mitogen-activated protein kinase (MAPK; ERK1/2 and p38) pathways crosstalk with PAFR, their inhibition also significantly attenuated targeted therapies-mediated MVP release. These findings indicate that PAFR signaling could be targeted to modify cellular responses of targeted therapies in lung cancer cells.

Highlights

Lung cancer is currently the second most prevalent type of cancer in both men and women in the United States, which continues to be a major health and socioeconomic issues [1,2,3]
Our studies demonstrate that targeted therapies-induced reactive oxygen species (ROS) generation is significantly reduced by NAC and WEB2086 compounds, similar to as observed by CPAF treatment (Figure 1B)
These studies confirmed that targeted therapies induce ROS generation, and suggest the role of the platelet-activating factor-receptor (PAFR) signaling in mediating this effect

Summary

Introduction

Lung cancer is currently the second most prevalent type of cancer in both men and women in the United States, which continues to be a major health and socioeconomic issues [1,2,3]. Several risk factors have been known to be associated with lung carcinogenesis, including environmental factors and pollutants such as smoking and arsenic exposure, etc., as well as genetic factors [4,5,6]. While lung cancer cases have been documented in non-smoking patients, smoking remains the most common contributing factor as long-term exposure to smoking has been shown to induce dysregulation and disruption in healthy lungs [7,8,9]. Non-small cell lung carcinoma (NSCLC) accounts for the majority of the cases diagnosed compared to a less prevent small cell lung carcinoma (SCLC) [10,11]. Depending upon the lung cancer stages, the treatment options include surgical resection, chemotherapy, radiation therapy, targeted and immune-based approaches, as well as a combination of two or more therapeutic agents [15,16,17,18,19]

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