Cancer Letters

Cancer Letters

Volume 407, 28 October 2017, Pages 76-83
Cancer Letters

Original Article
Pseudogene PDIA3P1 promotes cell proliferation, migration and invasion, and suppresses apoptosis in hepatocellular carcinoma by regulating the p53 pathway

https://doi.org/10.1016/j.canlet.2017.07.031Get rights and content

Highlights

  • A novel pseudogene PDIA3P1 is upregulated in HCC and can be used as a prognostic marker for HCC patients.

  • PDIA3P1 promotes the progression of HCC both in vitro and in vivo.

  • PDIA3P1 increases tumor proliferation, and decreases apoptosis by regulating p53 signaling in HCC cells.

Abstract

Pseudogenes are a subclass of long non-coding (lnc) RNAs that arose from protein-coding genes, but have lost the ability to produce proteins. Pseudogenes play an important role in the pathogenesis of various tumors; however, the role of pseudogenes in hepatocellular carcinoma (HCC) is poorly understood. In this study, we investigated a novel pseudogene, PDIA3P1, which was upregulated in HCC tissues compared with paired normal adjacent tissues. The expression of PDIA3P1 was significantly correlated with tumor size, metastasis, TNM stage, and overall stage. Knockdown of PDIA3P1decreased proliferation, migration, and invasion of HCC cells. PDIA3P1 knockdown also promoted cell apoptosis and inhibited tumor growth in vivo. We performed a GeneChip assay to investigate the underlying mechanism of PDIA3P1 action on biological function, and our results suggested that PDIA3P1 may promote proliferation and inhibit apoptosis of liver cancer cells by inhibiting the p53 pathway. Thus, our data suggest that PDIA3P1 acts as an oncogene in HCC and could be a potential prognostic marker and therapeutic target for HCC.

Introduction

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide, with a high prevalence in East and Southeast Asia [1]. In China, liver cancers are common and one of the leading causes of cancer-related death [2]. In 2012, an estimated 782,500 new liver cancer cases and 745,500 liver cancer-related deaths occurred worldwide, with China alone accounting for approximately 50% of the total cases and deaths [1]. These figures emphasize the urgent need for early diagnosis and establishing effective therapeutic targets for patients.

Long non-coding (lnc) RNAs are transcripts of more than 200 nucleotides without a protein-coding function [3]. Over the past several years, remarkable progress has been made in elucidating the function of lncRNAs in many biological processes [4], [5], and lncRNAs have been implicated in tumor formation and metastasis [6], [7], [8]. Pseudogenes are viewed as non-functional genomic relics of evolution [9]. They are a subclass of lncRNAs that arose from protein-coding genes, but have lost the ability to produce proteins [10]. Discovered in the 1970s, pseudogenes were considered non-functional and unimportant [11]. However, over the past two decades, more and more pseudogenes with multiple functions and the ability to modulate gene expression have been identified. In addition, accumulating evidence suggests that pseudogenes have physiological functions [12], [13], and that they may be involved in the pathogenesis of human cancer [14], [15], [16], [17], [18].

In this study, we investigated a novel pseudogene, protein disulfide isomerase family A member 3 pseudogene 1 (PDIA3P1), for the first time. The expression of PDIA3P1 was higher in HCC tissues than in paired adjacent tissues and was associated with worse clinical outcomes. Knockdown of PDIA3P1 in HCC cells inhibited proliferation, migration and invasion, and promoted apoptosis. Xenograft tumors developing from cells transfected with short hairpin RNA targeting PDIA3P1 showed smaller mean volumes and weights and slower growth than did tumors developing from control cells.

Section snippets

Tissue samples

Ninety tissue samples were collected from HCC and normal adjacent tissue samples (>2 cm from the tumor margin) from patients who underwent hepatectomy for HCC at the First Affiliated Hospital, College of Medicine, Zhejiang University from 2010 to 2013. The patients had no other liver diseases and had not received chemotherapy or radiation therapy before surgical resection. All tissues were preserved at −80 °C until use. The study was approved by the Human Research Ethics Committee of The First

PDIA3P1 is upregulated in HCC cell lines and tissues

To evaluate the role of PDIA3P1 in HCC progression, we examined expression levels in HCC cell lines and tissues using qRT-PCR. Our results showed that PDIA3P1 was significantly upregulated in five HCC cell lines (Huh7, SK-Hep1, HepG2, HCCLM3, and SMMC-7721) compared with a normal liver cell line (L02; Fig. 1A). We then detected PDIA3P1 in 90 paired HCC and adjacent normal liver tissues; fifty-one pairs showed (56%) significant upregulation of PDIA3P1 in the HCC tissues (Fig. 1B). In all 90

Discussion

HCC is one of the most malignant tumors in the world [1]. Although massive efforts have been made in clinical and basic research, the mortality rate of HCC remains one of the highest worldwide [19]. This is mainly due to the difficulty of early diagnosis and the lack of effective treatment options. Patients seeking medical help for HCC are often at advanced stages and thus have limited suitability for hepatectomy and liver transplantation [20]. Therefore, there is an urgent need for novel

Acknowledgements

This work was supported by National Natural Science Foundation of China, [grant #81572307(WLW)], Major Project of Medical and Health Technology Development Program in Zhejiang Province, [grant #7211902 (WLW)], National Key Basic Research Development Program (973 Program), [grant #2013CB531403 (WLW)] and Science and Technology Major Project of Zhejiang Province, [grant #2014C13G2010059 (WLW)].

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