| Colorectal cancer(CRC) is the third most common cancer in both male and female and the second cause of death from cancer in Western countries. At the time of diagnosis, synchronous metastases could been found in nearly 20% to 25% of patients, and a majority of patients with stage III disease will likely have a relapse during 5 years of diagnosis. The mainstream drugs used in advanced CRC include the fluoropyrimidines 5-fluorouracil and capecitabine, oxaliplatin and irinotecan, anti-VEGF monoantibody(such as bevacizumab), ani-EGFR monoantibogy(such as cetuximab), which may be used as single agents or in combinations in first or subsequent lines of therapy. However, these therapies are restricted to the toxic and adverse effects. To understand the mechanism of downstream signaling pathways of colorectal cancer, will provide strong support for exploring new drug and individualized treatment in colorectal cancer.Not only four but rather seven different human epidermal growth receptor trosine kinase(RTKs) have been found to be expressed in various normal and malignant cells:HER1(EGFR/Erb B1),HER2(Erb B2/Neu),HER3(Erb B3),and four different HER4 isoforms(JM-a, JM-b, CYT1, CYT2) have been identified. While EGFR and HER2 are well known oncogenes, and medicines targeting EGFR and/or HER2 have been approved for clinical use.Targeted therapy of HER2 in breast cancer in which HER2 is positive not only has made significant achievements, in recent years, more promotion to the treatment of gastric cancer where HER2 is positive. Overexpression or mutation of HER3 has been associated with malignant cellular growth, contributing to enhanced tumor progression and poor patient outcome. However, relatively little is known about the role of HER4 in cancer. In colorectal cancer, only a few studies have investigated the protein expression of HER4. It has been reported that HER4 membranous protein expression could predict for lymph nodes positivity. However, another study showed that, there was no correlation between the HER4 expression and patient prognosis. As a result, the role of HER4 in colorectal cancer remains to be illustrated. Alternative splicing of HER4 yields four major protein, these spliced isoforms differ in the extracelluar juxtamembrane domain(JM-a versus JM-b), and cytoplasmic domain(CYT-1 versus CYT-2). Failure to account for isoform-specific roles in previous studies may leading to confliciting reports on the role of HER4 in cancers. Thus, extended studies are required to ascertain definitively the prognostic value of HER4 isoforms in colorectal cancer. Among HER4 ligands are neureguilins(NRGs), which comprise a large family of EGF-like signaling molecules involved in cell-cell communication during development and disease, have recently been identified and are expressed in a range of normal tissues and in some forms of cancer including colorectal cancer. NRG1 is high affinity ligand of HER4, and is classified into at least three subgroups(type I-III), and has approximately 30 isoforms as a result of its synthesis from different promoters and splicing variants. NRG1 type I and type II are processed at the membrane by metalloproteinase, ADAM17,19 and are cleaved by α-secretase activity. NRG1 III contains a cysteine-rich domain that binds and activate HER3 and HER4. As reported, bone marrow-derived mesenchymal stem cells promote colorectal cancer progression through paracrine neuregulin1/HER3 signaling. The aim of this study was to evalute the expression of HER4 isoforms and its ligand NRG1 and their roles in colorectal cancer progression..The aim of this study is to evaluate the expression and association of the HER4 isoforms and its ligand NRG1 isoforms with the occurrence and progression in patients with primary colorectal cancer(CRC).Objective:1 To investigate the expression of HER4 isoforms JM-a, JM-b,CYT-1, CYT-2 and NRG1 isoforms NRG1 type, typeⅡ, type Ⅲ in colorectal cancer.2 To further explore the role of HER4 and its ligand NRG1 in colorectal cancer.3 To analyze the association of CYT1, CYT2 and NRG1 III.Mehtods:1 Patient’s selection and collection of biopsiesA total of 76 fresh-frozen samples(38 cancer tissues and 38 paired adjacent normal tissues) were obtained from patients treated for colorectal cancer between November 2013 and August 2014 at the Second Department of Surgery, the Forth Hospital of Hebei Medical University. The patients were operated by the same staff, and the samples were collected at the primary surgery before chemotherapy or radiation. The tissues were diagnosed preoperatively by endoscopic biopsy as colorectal cancer, and the normal tissues which were 5cm away from the tumor edge.2 RNA isolation and reverse transciption quantitaive polymerase chain reaction(RT-PCR)To measure the expression of specific transcripts encoding the isoforms JM-a, JM-b, CYT1, CYT2, NRG1 I, II,III, quantitative real-time RT-PCR was performed. HER4 m RNA expression level was normalized by β-actin m RNA, and this ratio(HER4 m RNA as percent of β-actin m RNA) was used in statistical analyses withΔΔCt method. The data was statistically by the software of SPSS13.0.Results:1 The expression of HER4 and NRG1 isoforms in colorectal cancer tissue and adjacent normal tissueThe expression of CYT1(P=0.002), CYT2(P=0.002),NRG1 type Ⅲ(P=0.000)was significantly higher than that in adjacent normal tissue(All P<0.05). The expression of JM-a,JM-b, NRG1 type I, II was not significantly different from adjacent normal tissue.2 Association of HER4 and NRG1 isoforms expression with clinicopathological parameters in colorectal cancerOf the 38 cases colorectal cancer patients, the CYT-1 expression was significantly associated with the depth of invasion(P=0.027) and TNM stage(P=0.033)in colorectal cancer.The median expression of CYT1 of T2-3 was lower than T4, the median were 0.62 and 5.24 respectively, P=0.027. The median expression of CYT1 increased significantly in stage II compared with stage I(0.42 vs 10.25), however, there was no difference between stage II and stage III. The CYT2 expression was associated with T( P=0.018), N( P=0.015), and TNM(P=0.038). The median expression of CYT2 significantly increased from T2-3 to T4, as 5.36 vs 39.48. The CYT2 increased significantly where the lymph node was positive compared with lymph node negative, 5.36 vs 50.59, P=0.015. The CYT2 expression had no difference between stage I and stage II, however CYT2 expression of stage III(median =50.59)was higher than stage I(median =5.9) and stage II(median =3.34), P<0.05. The expression of NRG1 III was correlated with the lymph node metastases, the median expression were higher in the lymph node positive cases, the NRG1 III median expression of lymph node negative and positive were 5.36 and 50.59 respectively, P=0.015.There was no correlation between the expression of CYT-1, CYT-2, NRG1 III and age, sex, tumor size, tumor grade, CEA level.(P>0.05).3 Correlation analysis(Spearman-Rho) between HER4 isoforms(CYT1, CYT2) and NRG1 III expressionCYT1 was associated with CYT-2, r=0.481, P<0.05. CYT2 was associated with NRG1 Ⅲ r=0.691,P<0.01.Conclusion:1 There may have a upregulation of CYT1, CYT2, and NRG1 III expression in colorectal cancer, and they may participate in the progression of colorectal cancer.2 There has no significant correlation beween JMa,JMb, NRG1 I and NRG1 II expression and the clinicopathological parameters of colorectal cancer. |
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