Targeting cytosolic phospholipase A2 α in colorectal cancer cells inhibits constitutively activated protein kinase B (AKT) and cell proliferation

Abstract

// Zhong Zheng 1,* , Xiangyi He 2,* , Chanlu Xie 3,6 , Sheng Hua 3 , Jianfang Li 4 , Tingfeng Wang 5 , Mu Yao 3 , Soma Vignarajan 3 , Ying Teng 3 , Leila Hejazi 3,6 , Bingya Liu 4 and Qihan Dong 3,6 1 Department of Gynecologic Oncology, Fudan University Shanghai Cancer Center, Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China 2 Department of Gastroenterology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China 3 Central Clinical School and Bosch Institute, The University of Sydney and Department of Endocrinology and Sydney Cancer Centre, Royal Prince Alfred Hospital, Sydney, Australia 4 Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, and Gastroenterology, Ruijin Hospital, Jiaotong University School of Medicine, Shanghai, China 5 Department of General Surgery, Nanhui Central Hospital. Shanghai, China 6 School of Science and Health, The University of Western Sydney, Australia * These authors contributed equally to this work Correspondence: Qihan Dong, email: // Bingya Liu, email: // Keywords : Cytosolic phospholipase A 2 α, AKT, Colorectal cancer, Efipladib Received : September 09, 2014 Accepted : October 28, 2014 Published : October 28, 2014 Abstract A constitutive activation of protein kinase B (AKT) in a hyper-phosphorylated status at Ser 473 is one of the hallmarks of anti-EGFR therapy-resistant colorectal cancer (CRC). The aim of this study was to examine the role of cytosolic phospholipase A 2 α (cPLA 2 α) on AKT phosphorylation at Ser 473 and cell proliferation in CRC cells with mutation in phosphoinositide 3-kinase (PI3K). AKT phosphorylation at Ser 473 was resistant to EGF stimulation in CRC cell lines of DLD-1 ( PIK3CA E545K mutation) and HT-29 ( PIK3CA P499T mutation). Over-expression of cPLA 2 α by stable transfection increased basal and EGF-stimulated AKT phosphorylation and proliferation in DLD-1 cells. In contrast, silencing of cPLA 2 α with siRNA or inhibition with Efipladib decreased basal and EGF-stimulated AKT phosphorylation and proliferation in HT-29. Treating animals transplanted with DLD-1 with Efipladib (10 mg/kg, i.p. daily) over 14 days reduced xenograft growth by >90% with a concomitant decrease in AKT phosphorylation. In human CRC tissue, cPLA 2 α expression and phosphorylation were increased in 63% (77/120) compared with adjacent normal mucosa determined by immunohistochemistry. We conclude that cPLA 2 α is required for sustaining AKT phosphorylation at Ser 473 and cell proliferation in CRC cells with PI3K mutation, and may serve as a potential therapeutic target for treatment of CRC resistant to anti-EGFR therapy.