Significance Expression Of EML4-ALK Fusion Gene And ALK Protein In Non-small Cell Lung Cancer

【Objective】To evaluate the expression of EML4-ALK fusion gene by Amplification refractory mutation system (ARMS) and level of ALK protein by immunohistochemistry (IHC) in non-small cell lung cancer(NSCLC).To analysis the clinicopathological characteristics of EML4-ALK fusion NSCLC,and compare the consistency of two methods to detect EML4-ALK fusion gene in NSCLC.【Methods】1.Part1:The level of ALK protein was detected by EliVisionTM plus immunohistochemical staining methods in specimens of280cases of NSCLC,analyze its correlation with clinicopathological features.2.Part2:The expression of EML4-ALK fusion gene was detected by ARMS in all ALK immunohistochemical positive cases and some random selected negative cases in Part1.We also analyze its correlation with clinicopathological features,and compare the consistency of two methods to detect EML4-ALK fusion gene in NSCLC.【Results】1. Of280non-small cell lung cancer specimen,44(15.7%)showed ALK protein expression by IHC. Expression of ALK protein was closely correlated with age,sex,smoking history, clinical stage and tumor histological type(P<0.05),but not related to tumor size(P>0.05).2.29EML4-ALK gene fusion NSCLC were detected in90cases that test EML4-ALK fusion gene by PCR,25(86.2%) was E6;A20、E13;A20、E20;A20variants,1(3.4%) was E2;A20、E3;A20、E17;A20、E18;A20variants,and3(10.4%)was concurrent E6;A20、E13;A20、E20;A20and E2;A20、E3;A20、E17;A20、E18;A20variants. EML4-ALK fusion NSCLC had significant correlation with age,smoking history,tumor histological type/subtype and EGFR mutation status(P＜0.05),while not with sex,tumor size and clinical stage(P＞0.05).3.65.9%(29/44) of ALK protein positive cases were observed EML4-ALK fusion gene.High consistency results were detected between ALK protein IHC3+(21/90)and PCR(100%),the sensitivity and specificity of IHC to detect EML4-ALK fusion gene was100%and78.9%;44(48.9%)gross specimen and46(51.1%)biopsy specimen were included in90cases that detect EML4-ALK fusion gene, in gross specimen，the coincidence rate of IHC3+、2+、1+with PCR were100%、57.1%、0%，in biopsy specimen，the coincidence rate of IHC3+、2+、1+with PCR were100%、100%、20%，the sensitivity and specificity of IHC to detect EML4-ALK fusion gene in gross specimen and biopsy specimen were100%、72.2%and100%、80%.【Conclusions】EML4-ALK gene fusion NSCLC as a unique subtype of lung cancer,has a certain clinicopathologic features，for example are commonly seen in young，no/less smoking adenocarcinoma patients.The variants of EML4-ALK fusion are diversity and complexity,which suggest that we should pay more attention to screen all the variants in clinical molecular tests to improve the detection rates. The IHC use ALK D5F3monoclonal antibody to detect ALK fusion gene provides good sensitivity,but the specificity is not satisfying.There is high concordance between ALK protein detected by IHC and EML4-ALK fusion gene detected by PCR both in biopsy and gross specimen.ALK protein may provide a simple,exact and cheap way to evaluate the occurrence of EML4-ALK fusion gene.