PAQR3 suppresses the growth of non-small cell lung cancer cells via modulation of EGFR-mediated autophagy.

ABSTRACT

Macroautophagy/autophagy is an evolutionarily conserved intracellular process that recycles and degrades intracellular components to sustain homeostasis in response to deficiency of nutrients or growth factors. PAQR3 is a newly discovered tumor suppressor that also regulates autophagy induced by nutrient starvation via AMPK and MTORC1 signaling pathways. In this study, we investigated whether PAQR3 modulates EGFR-mediated autophagy and whether such regulation is associated with the tumor suppressive activity of PAQR3. PAQR3 is able to inhibit the in vitro and in vivo growth of non-small cell lung cancer (NSCLC) cells. PAQR3 potentiates autophagy induced by EGFR inhibitor erlotinib. Knockdown of PAQR3 abrogates erlotinib-mediated reduction of BECN1 interaction with autophagy inhibitory proteins RUBCN/Rubicon and BCL2. PAQR3 blocks the interaction of BECN1 with the activated form of EGFR and inhibits tyrosine phosphorylation of BECN1. Furthermore, inhibition of autophagy by knocking down ATG7 abrogates the tumor suppressive activity of PAQR3 in NSCLC cells. Collectively, these data indicate that PAQR3 suppresses tumor progression of NSCLC cells through modulating EGFR-regulated autophagy. ABBREVIATIONS AKT thymoma viral proto-oncogene; ATG5 autophagy related 5; ATG7 autophagy related 7; ATG14 autophagy related 14; BCL2 B cell leukemia/lymphoma 2; BECN1 beclin 1; CCK-8 cell counting kit-8; CQ chloroquine diphosphate; DMEM Dulbecco's modified Eagle's medium; EdU 5-ethynyl-2'-deoxyuridine; EGFR epidermal growth factor receptor; FBS fetal bovine serum; GAPDH glyceraldehyde-3-phosphate dehydrogenase; IgG Immunoglobulin G; MAP1LC3B/LC3B microtubule-associated protein 1 light chain 3 beta; MTOR mechanistic target of rapamycin kinase; MTORC1 mechanistic target of rapamycin kinase complex 1; MTT thiazolyl blue tetrazolium bromide; NSCLC Non-small cell lung cancer; MAP2K/MEK mitogen-activated protein kinase kinase; MAPK/ERK mitogen-activated protein kinase; PAQR3 progestin and adipoQ receptor family member 3; PI3K phosphatidylinositol-4,5-bisphosphate 3-kinase; PIK3C3/VPS34 phosphatidylinositol 3-kinase catalytic subunit type 3; PIK3R4/VPS15 phosphoinositide-3-kinase regulatory subunit 4; PRKAA/AMPK protein kinase, AMP-activated alpha catalytic; RUBCN rubicon autophagy regulator; RPS6 ribosomal protein S6; RAS Ras proto-oncogene; RAF Raf proto-oncogene; TKI tyrosine kinase inhibitor; TUBA4A tubulin alpha 4a; UVRAG UV radiation resistance associated.