Down-regulation of long non-coding RNA RP11-708H21.4 is associated with poor prognosis for colorectal cancer and promotes tumorigenesis through regulating AKT/mTOR pathway.

Longci Sun,Hong Zhou,Ye Liu,Lei Gu,Hanbing Xue,Chunjie Xu,Qing Xu,Chunhui Jiang

doi:10.18632/oncotarget.15846

Abstract

Long non-coding RNAs (lncRNAs) serve critical roles in cancer development and progression. Herein, through next generation RNA sequencing and experimental validations, we determined the expression status of RP11-708H21.4 in colorectal cancer (CRC) and explored its clinical significance and biological functions in CRC. Differentially expressed lncRNAs from CRC samples and corresponding normal mucosa tissues was screened through RNA sequencing, and RP11-708H21.4 was selected for further experimental validation. The expression levels of RP11-708H21.4 in CRC tissues and cell lines were determined using qRT-PCR. Also, the relationship between the clinicopathological features and RP11-708H21.4 expression was analyzed. Cell viability was examined by CCK-8 and colony assays; cell migration and invasion were detected by transwell assays; cell cycle and cell apoptosis were analyzed by flow cytometry. The chemosensitivity of CRC cells to 5-Fluorouracil (5-FU) was also determined using CCK-8 assay. CRC xenograft tumor models were established to determine the biological functions of RP11-708H21.4 in vivo. Levels of cell cycle-related proteins and AKT/mTOR pathway-related proteins were detected by western blot assay. RP11-708H21.4 expression was aberrantly decreased in CRC, and its expression was closely associated with aggressive clinicopathologic features and unfavorable prognosis of CRC patients. Overexpressed RP11-708H21.4 suppresses CRC cell proliferation through inducing G1 arrest. Moreover, up-regulation of RP11-708H21.4 inhibits cell migration and invasion, causes cell apoptosis, and enhances 5-FU sensitivity of CRC cells. Finally, increased RP11-708H21.4 expression blocked AKT/mTOR pathway, and repressed in vivo CRC xenograft tumor growth. The results indicated that RP11-708H21.4 might have potential roles as a biomarker and a therapeutic target for CRC.

Highlights

The colon/rectum is one of the most prevailing tumor sites, and colorectal cancer (CRC) ranks the third most frequent cancer and the fourth most leading reason of cancer-associated mortality globally, with approximately 1.2 million new cases and 0.6 million deaths reported each year [1, 2]
RP11-708H21.4 expression was aberrantly decreased in CRC, and its expression was closely associated with aggressive clinicopathologic features and unfavorable prognosis of CRC patients
With P < 0.05 and |log2FC|≥1.0 as the threshold, a total of 39 up-regulated and 78 down-regulated Long non-coding RNAs (lncRNAs) were identified in primary CRC samples compared with adjacent normal mucosa tissues using Student’s t-test method, as depicted in the volcano plot (Figure 1A) and the heat map (Figure 1B)

Summary

Introduction

The colon/rectum (colorectum) is one of the most prevailing tumor sites, and colorectal cancer (CRC) ranks the third most frequent cancer and the fourth most leading reason of cancer-associated mortality globally, with approximately 1.2 million new cases and 0.6 million deaths reported each year [1, 2]. CRC is becoming more prevalent in developing countries, especially in China [3], and its occurrence rate has an elevating trend with the development of economy and living standard [4]. Encouraging progress in diagnosis and cancer therapeutic methods has been made during the past several years, the overall survival rates of CRC patients still remain unfavorable [2]. The underlying molecular mechanisms which modulate the metastasis and recurrence in CRC still remain largely unknown. It is essential to identify some novel molecular markers to raise the efficiency of tumor diagnosis and to predict prognosis of CRC patients or even for therapeutic application

Methods

Results

Conclusion