Overexpression of LARP1 predicts poor prognosis of

Authors: Ling Ye Shengtao Lin Yushuai Mi Yuan Liu Yang Ma Huimin Sun Zhihai Peng Junwei Fan

Publish Date: 2016/09/10

Volume: 37, Issue: 11, Pages: 14585-14594

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Abstract

This study investigated the significance of Larelated protein 1 LARP1 in the development and progression of colorectal cancer CRC Quantitative realtime polymerase chain reaction and Western blot analyses were carried out to determine the mRNA and protein expression of LARP1 in CRC tumor tissues and paired adjacent normal mucosa The expression of LARP1 was upregulated in CRC Immunohistochemical analysis using tissue microarray was performed A positive correlation between LARP1 and proliferating cell nuclear antigen PCNA in the area of proliferation was observed using the Spearman’s correlation coefficient test r = 0332 P  001 The elevated expression of LARP1 significantly correlated with T stage P = 002 N stage P = 0006 M stage P  0001 American Joint Committee on Cancer AJCC stage P = 004 differentiation rank P  0001 and PCNA level P  0001 In addition the inhibitory effect of LARP1 knockdown on CRC cell proliferation was demonstrated using Cell Counting Kit8 CCK8 and colonyforming cell CFC assays Multivariate analysis showed that LARP1 was an independent prognostic factor for overall survival OS hazard rate HR = 0244 95  confidence interval CI 0078–0769 P = 0016 and diseasefree survival DFS HR = 0281 95  CI 0086–0917 P = 0035 in CRC patients LARP1 plays an important role in the proliferation of colorectal cancer and represents a new prognostic indicatorColorectal cancer CRC is one of the most common cancers worldwide with a high incidence and mortality 1 In China CRC is the fourth most common cancer and the fifth leading cause of death among all types of human cancer 2 3 Although CRC has a very high cure rate following surgical resection followed by multidisciplinary treatment radiation and systemic chemotherapy in the early stages the high rate of relapse and distant metastasis still threaten a large percentage of patients 4 5 Efforts have been made to elucidate the genetic and molecular characteristics of CRC for prognosis and response to targeted treatment 3 5 Tumor proteins such as P53 KRAS and others have been associated with colorectal cancer progression and prognosis However tumor heterogeneity suggests the need for new markers of CRC 4 6Candidate diagnostic markers in colon cancer were screened by combining experimental and bioinformatics approaches Using laser capture microdissection we obtained purified cell populations from heterogeneous tissues and found that Larelated protein 1 LARP1 an RNAbinding protein RBP was overexpressed in colorectal cancer tissues compared with paired normal specimens 7The LARP subfamilies comprising La LARP1 LARP1b LARP4 LARP4b LARP6 and LARP7 play a significant role in transcription and/or mRNA translation 8 9 The members of the LARP family lack enzymatic domains but carry a La motif and a nearby RNA recognition motif with location varying among the different LARP proteins 8 RBPs are important posttranscriptional regulators with a key role in gene expression in a variety of human tumors 10 11 12 13 LARPs are one of the RBPs that promote cell migration invasion and tumorigenesis in vivo 14 Therefore a comprehensive understanding of LARPs enables early detection of new biomarkers and facilitates the development of a strategy for cancer prevention and therapyLARP1 gene which is located on chromosome 5q34 encodes a 1096amino acid protein 15 LARP1 carries a unique and highly conserved DM15 region with unknown function 16 However DM15 has been suggested to mediate nucleic acid binding which may be associated with oncogenesis 9 17 Recently LARP1 was shown to be overexpressed in cervical and nonsmall cell lung cancers with increased expression correlated with cancer progression and poor prognosis 14 As a promising biomarker the expression of LARP1 is closely related to poor prognosis of earlystage and alphafetoproteinnormal hepatocellular carcinoma HCC patients 18 Recently it has been found that downregulation of LARP1 expression in endometrial cancer and lung cancer cell lines was associated with decreased cell proliferation 19 However the role of LARP1 in the prognosis and cellular proliferation of colorectal cancer has yet to be definedUncontrolled cell proliferation is considered to be an important feature of malignancy and is closely related to cancer progression A previous study demonstrated that LARP1 is associated with the proliferation of endometrial cancer and lung cancer lines 19 In this study we explored the effect of LARP on the proliferation of colorectal cancer cells As the accessory protein of DNA polymerase δ Proliferating cell nuclear antigen PCNA plays an important role in cell proliferation DNA replication and repair 20 In addition PCNA also interacts with proteins involved in cell cycle regulation and checkpoint control 21 The crucial role of PCNA in cellular proliferation supports its frequent use as a marker of tumor cell proliferation 22 23 Therefore we combined PCNA with LARP1 to examine the effect of LARP1 on CRC cell proliferationThis study initially evaluated the expression of LARP1 in CRC tissues and adjacent normal specimens to investigate the significance of LARP1 in the development and progression of CRC Furthermore our study determined the expression of LARP1 and PCNA using immunohistochemical analysis with CRC tissue microarrays TMAs We investigated the relationship with clinic pathological features as well as patient survival to illustrate the possibility of LARP1 as a prognostic marker in CRC The correlation between LARP1 and PCNA in cancer cell proliferation was determined using the Spearman’s correlation coefficient test The influence of LARP1 on CRC cell proliferation was studied after silencing the expression of LARP1 using short hairpin RNA shRNA

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