Plasminogen kringle 5 suppresses gastric cancer via regulating HIF-1\u03b1 and GRP78

Shuhuan Fang,Weibin Cai,Jianxing Ma,Shaoyuan Zuo,Xia Yang,Guoquan Gao,Lei Li,Qiyuan Wu,Zumin Xu,Chunkui Shao,Honghai Hong,Dan He,Zhiyu Dai,Jing Han

doi:10.1038/cddis.2017.528

Abstract

Inhibition of tumour angiogenesis has an important role in antitumour therapy. However, a recent study indicates that antiangiogenesis therapy may lead to glucose-related protein 78 (GRP78) associated antiapoptotic resistance. The present study aims to elucidate the dual effects of plasminogen kringle 5 (K5) on tumour angiogenesis and apoptosis induction by targeting hypoxia-inducible factor 1α (HIF-1α) and GRP78. Co-immunoprecipitation and western blotting were used for examining the ubiquitination of HIF-1α and analysing angiogenesis and apoptosis-associated proteins. K5 promoted the sumo/ubiquitin-mediated proteasomal degradation of HIF-1α by upregulating von Hippel-Lindau protein under hypoxia, resulting in the reduction of vascular endothelial growth factor and thus suppressing tumour angiogenesis. Furthermore, K5 decreased GRP78 expression via downregulation of phosphorylated extracellular-regulated protein kinase, leading to caspase-7 cleavage and tumour cell apoptosis. Blocking voltage-dependent anion channel abrogated the effects of K5 on both HIF-1α and GRP78. K5 significantly inhibited the growth of gastric carcinoma xenografts by inhibiting both angiogenesis and apoptosis. The dual effects suggest that K5 might be a promising bio-therapeutic agent in the treatment of gastric cancer, particularly in patients who exhibit the induction of GRP78.

Highlights

Gastric cancer is an aggressive malignancy that is frequently diagnosed at an advanced stage with poor prognosis
Our results showed that voltage-dependent anion channel (VDAC), as a critical signalling receptor of K5, mediated the dual effects of antiangiogenesis and pro-apoptosis of K5
hypoxia-inducible factor 1α (HIF-1α) is hydroxylated by the oxygen-sensitive PHDs, which leads to the binding of E3 ubiquitin ligase, von Hippel-Lindau protein (VHL), to HIF-1α in a complex with elongin B, elongin C, and Cul2.22,23,26 When cells are exposed to a hypoxic microenvironment, this hydroxylation-mediated degradation pathway is blocked and results in HIF-1α translocation and accumulation in the nucleus, where it binds to the constitutively expressed HIF-1β to form a heterodimer and activates hypoxia-responsive genes, such as vascular endothelial growth factor (VEGF) and Glu-1.27,28 Consistent with previous results, HIF-1α accumulated under hypoxia (Figure 3d)

Summary

Introduction

Gastric cancer is an aggressive malignancy that is frequently diagnosed at an advanced stage with poor prognosis. VEGF-neutralizing antibody Avastin (bevacizumab) and VEGF receptor tyrosine kinase inhibitors (sorafenib and sunitinib) inhibit primary tumour growth in clinical applications and have been used as anticancer treatments in several tumour types.[8] clinical observations indicate that these therapies may have limited efficacy because the response has been mostly transient, in addition to the development of drug resistance.[9] Glucoserelated protein 78 (GRP78) could be induced by severe glucose and oxygen deprivation resulting from antivascular and antiangiogenesis therapies, which could lead to drug resistance in an HIF-1α-independent manner.[10] In conditions of stress or hypoxia associated with oncogenesis, GRP78, a major endoplasmic reticulum chaperone, has an essential role in counteracting the apoptosis, which promotes cancer cell proliferation, survival, metastasis, and resistance to a wide variety of therapies.[11,12]. The present study was designed to investigate the effects and the mechanism underlying these effects of K5 on both HIF-1α-induced angiogenesis and GRP78-dependent apoptosis resistance in gastric cancer cells

Methods

Results

Conclusion