Functions And Significance Of Lactate Dehydrogenase A For Proliferation And Invasion Of Gastroenteropancreatic Neuroendocrine Tumors

Objective To investigate the expression and clinicopathological significance of lactate dehydrogenase A in different grades of gastroenteropancreatic neuroendocrine tumors(GEP-NETs).We aimed to explore the correlation between LDHA and GEP-NETs,and to clarify the relationship between LDHA and both of serum lactate dehydrogenase(LDH)and classical markers of GEP-NETs.And we discussed its clinical significance as a new therapeutic and prognostic target.Furthermore,we performed cell function experiment to verify the effect of LDHA on the proliferation and invasion abilities of GEP-NETs cell line,and further enrich the genetic studies of GEP-NETs.Methods Totally,112 patients with GEP-NETs,who underwent endoscopic and surgical resection from January 2013 to December 2018,were recruited at the Affiliated Hospital of Qingdao University.The patients were designated as grade 1(G1)(n=43),grade 2(G2)(n=17),grade 3(G3)(n=52)according to Ki-67 index and mitotic rate.LDHA expression in different grades of GEP-NETs tissue was determined by immunohistochemical.The correlation between LDHA expression in GEP-NETs tissue and clinicopathological characteristics,in addition to survival time,was analyzed.The data were also analyzed for correlations between LDHA expression and both serum LDH and classic neuroendocrine markers.Small interfering RNA was used to inhibit the expression level of LDHA in neuroendocrine tumor cells STC-1.LDHA mRNA expression level was detected by Quantitative Real Time Polymerase Chain Reaction(qRT-PCR)and the expression of protein was examined by Western Blot.The effect of reduced LDHA expression in STC-1 on proliferation,migration and invasion was verified by cell function experiments.All data was analyzed by SPSS 22.0.The t-test was performed for different group,Pearson Chi-square or Fisher’s was performed for counting data and Pearson Chi-square or Spearman was performed for the correlation analysis.The Kaplan-Meier curve was used for univariate survival analysis,Cox for multi-factor survival analysis.And the log-rank test was used for comparison between groups of survival assess.P<0.05 indicated the difference was statistically significant.Results The expression of LDHA in GEP-NETs tissues were different for three grades,and the higher the grade was,the higher the positive expression rate was,the positive expression rate of G1 was 48.8%(21/43),G2 was 70.6%(12/17)and G3 was90.4%(47/52).Clinicopathological analysis showed that LDHA expression in GEP-NETs was correlated with gender,tumor size,TNM staging,infiltration depth and lymph node metastasis(all P<0.05).LDHA expression levels in GEP-NETs tissues had no significant correlation with age,primary site and distant metastasis(all P>0.05).LDHA expressed in tissues was independent of classic neuroendocrine markers and serum LDH(all P>0.05).Univariate survival analysis showed that pathological grade,lymph node metastasis,distant metastasis,serum LDH and TNM stages were associated with poor survival outcomes(all P<0.001).Cox regression analysis showed that pathological grade(P=0.001,HR=0.064,95%CI:0.013-0.307),distant metastasis(P=0.006,HR=0.326,95%CI:0.146-0.729)and serum LDH expression(P<0.001,HR=0.106,95%CI:0.035-0.325)were independent prognostic factors for poor prognosis.Kaplan-Meier curve and log-rank test showed that the survival rate of patients with high LDHA expression was significantly lower than that of the low-expression group(χ~2=7.544,P=0.006).The levels of mRNA and protein in LDHA knockdown STC-1 cell were decreased significantly.Cell function experiments uncovered that low expression of LDHA was negatively regulated STC-1 cell proliferation,migration and invasion.Conclusion 1.The LDHA positive expression rate increased with the increase of the GEP-NETs grade.2.LDHA expression in GEP-NETs tissues was correlated with gender,tumor size,invasion depth,TNM stage and lymph node metastasis.3.The high expression of LDHA in tumor tissues predicted a poor prognosis in patients,and combination of serum LDH and tissue LDHA could predict prognosis in patients with GEP-NETs.4.LDHA promotes the proliferation,migration,and invasion of STC-1,may be a promising candidate for the treatment of GEP-NETs.