Reduced RKIP expression levels are associated with frequent non-small cell lung cancer metastasis and STAT3 phosphorylation and activation

Abstract

Abstract. The current study examined the role of Raf kinase inhibitor protein (RKIP) in non-small cell lung cancer (NSCLC) metastasis. A total of 100 patients with NSCLC were recruited following pathological diagnosis in the First Affiliated Hospital of Bengbu Medical College. The patients were classified and statistically analyzed according to their clinicopathological characteristics and tumor-node-metastasis stage. Paired tumor tissue and adjacent non-tumor tissue samples were subject to pathological diagnosis and western blot analysis. Transient transfection and lentivirus particle vector-mediated RKIP overexpression, small interfering RNA-mediated silencing, Transwell assays and immunocytochemistry methods were employed to elucidate the role and underlying mechanisms of RKIP and the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway in NSCLC metastasis. Furthermore, in order to examine the in vivo effects of RKIP, recombinant lentivirus particles containing the RKIP gene were administrated in a mouse NSCLC tumor model via tail vein injection. The results revealed reduced RKIP expression levels in NSCLC tissue compared with corresponding non-cancer tissue. Additionally, RKIP expression levels were inversely associated with NSCLC intra-lung, lymph node and long-distance metastasis. The results also indicated that RKIP was able to block STAT3 activation via phosphorylation and inhibit NSCLC-cell metastasis in vitro. Furthermore, RKIP knockdown was able to promote STAT3 phosphorylation and cell metastasis in NSCLC cell lines. During in vivo experiments, RKIP overexpression was able to suppress xenograft tumor metastasis in nude mice. Therefore, RKIP may be an important factor in cancer cell metastasis in patients with NSCLC, and RKIP may inhibit NSCLC-cell invasion by blocking the activation of the JAK/STAT3 signaling pathway. IntroductionLung cancer has increased in incidence in the developing world since 2008, from 1.8 to 2 million per year, and this trend is predicted to continue in the future (1). Non-small cell lung cancer (NSCLC) is among the most malignant types of cancer, and has a high mortality rate (2). Approximately 80-90% of lung cancer cases are of NSCLC, and 50-70% of these patients are diagnosed at the advanced stage of disease (1,3). The survival time of patients with lung cancer is 5 years in 10-15% of cases, with the remaining exhibiting poorer survival times (1). Therefore, the early prevention of NSCLC metastasis is a key factor in lung cancer prevention and the development of novel therapeutic agents. A number of studies have investigated the mechanisms underlying NSCLC metastasis (4,5); however, the exact mechanisms underlying this process require further elucidation.Raf kinase inhibitor protein (RKIP) is a small evolutionarily conserved protein, which was initially identified to function as a physiological inhibitor of the Raf/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway (6). RKIP inhib...

RKIP reduction enhances radioresistance by activating the Shh signaling pathway in non-small-cell lung cancer

“… 58 In NSCLC, nude mice loaded with RKIP-overexpressing A549 cells through veil injection showed inhibition of both tumor growth and metastasis. 59 RKIP overexpression also enhanced metastatic ability in colorectal cancer 60 and increased tumor volume in pancreatic cancer. 61 From the evidence above, we can see a strong connection between RKIP expression and malignant tumor behaviors in vivo.…”

MicroRNA-124a inhibits cell proliferation and migration in liver cancer by regulating interleukin-11

“…It has been confirmed that IL-11 plays a significant role in the progression of pancreatic (38), gastric (39), and renal cancers (40) and promotes the BM of liver cancer (41). STAT signalling plays a significant role in the transfer of extracellular signals into the nucleus, resulting in the regulation of transcription, and is essential in the uncontrolled growth, angiogenesis, and metastasis of cancer cells (42,43). STAT3 is a direct target of miR-124 and is overexpressed in most hepatocellular carcinomas with poorer prognosis, however it is not overexpressed in normal liver tissues or in surrounding non-tumour tissues (44,45).…”

RKIP: A Key Regulator in Tumor Metastasis Initiation and Resistance to Apoptosis: Therapeutic Targeting and Impact

“…This interaction impairs the activation of ANXA7 GTPase by a small molecule SEC, which in turn leads to metastasis suppression via the AMPK/mammalian target of rapamycin complex 1 (mTORC1)/STAT3 signaling pathway [144]. The inhibitory role of RKIP on STAT3 signaling and the consequent effects on metastasis initiation in vitro and in vivo have been also validated by additional studies on other tumor models [98,99,145]. …”