Correlation Between PD-L1 Protein Expression And Gene Amplification And Clinicopathological Features In Gastric Cancer

Objective:To investigate the correlation between PD-L1 protein expression and gene amplification and clinicopathological features in gastric cancer.Methods:247 gastric cancer patients with complete follow-up and clinicopathological data from Shanxi Cancer Hospital in 2011 were selected.At the same time,30 paracancerous tissues were selected as controls.Immunohistochemistry(IHC)and fluorescence in situ hybridization(FISH)were used to detect PD-L1 protein expression and gene amplification.Results:(1)pTNM stage(?~2=39.937,P<0.001),tumor diameter(?~2=16.239,P<0.001),vascular tumor thrombus(?~2=13.029,P<0.001),depth of invasion(?~2=31.668,P<0.001)and lymph node metastasis(?~2=56.698,P<0.001)were all adverse prognostic factors of gastric cancer.Multivariate analysis showed that pTNM stage(95%CI 2.297-5.290,P<0.001),the depth of invasion(95%CI 1.259-2.247,P<0.001)and lymph node metastasis(95%CI 1.345-1.920,P<0.001)were independent risk factors for gastric cancer.(2)The positive rate of PD-L1 protein on tumor cells(TC)in 247 gastric cancer patients was 25.9%(64/247).The positive rate on tumor infiltrating immune cells(IC)was 26.7%(66/247).There was a correlation between the two(P<0.001).There was a correlation between the expression of PD-L1 protein on TC and the degree of differentiation(?~2=8.016,P=0.018)and tumor diameter(?~2=5.241,P=0.022).There was a correlation between the expression of PD-L1 protein on IC and vascular cancer thrombi(?~2=5.885,P=0.015).The 3-year overall survival rate was 39.0%(25/64)for PD-L1 protein on TC positive patients and 60.1%(110/183)for PD-L1 protein negative patients.The 5-year overall survival rate was 20.3%(13/64)for PD-L1 protein on TC positive patients and 42.1%(77/183)for PD-L1 protein negative patients.PD-L1 protein on TC had a negative correlation with prognosis(3-year OS:?~2=14.116,P<0.001,5-yeas OS:?~2=13.486,P<0.001).The 3-year and 5-year overall survival rates with positive PD-L1 protein expression on TC were lower than those with negative PD-L1 protein expression.There was no correlation between PD-L1 protein expression on IC and prognosis(P>0.05).Multivariate analysis showed that PD-L1 protein expression was an independent risk factor for gastric cancer.(3)The PD-L1 gene amplification rate was 19.0%(47/247)in 247 gastric cancer patients.The PD-L1 gene amplification was associated with the age(?~2=5.745,P=0.017),stomach curvature(?~2=6.486,P=0.039),tumor location(?~2=6.700,P=0.035),tumor diameter(?~2=3.897,P=0.048)and lymph node metastasis(?~2=8.839,P=0.032).The3-year overall survival rate was 68.1%(32/47)in PD-L1 gene amplification group,while the 3-year overall survival rate was 51.5%(103/200)without PD-L1 gene amplification.The 5-year overall survival rate was 40.4%(19/47)in PD-L1 gene amplification group,while the 5-year overall survival rate was 35.5%(71/200)without PD-L1 gene amplification.Univariate analysis showed that:There was no significant correlation between PD-L1 gene amplification and prognosis(P>0.05).(4)The positive coincidence rate of the two methods was 24.4%(21/86)and the negative coincidence rate was 83.9%(135/161).The total coincidence rate was 63.2%(156/247).The consistency between IHC and FISH was poor(Kappa=0.092,P=0.115).The positive rate of IHC was higher than that of FISH.Conclusion:(1)pTNM stage,vascular tumor thrombus,tumor diameter,depth of invasion and lymph node metastasis were all adverse prognostic factors for gastric cancer.Multivariate analysis showed that pTNM stage,depth of invasion and lymph node metastasis were independent risk factors for gastric cancer.(2)PD-L1 protein positive expression on TC is a poor prognostic factor for gastric cancer.(3)PD-L1 gene amplification was not significantly correlated with prognosis of gastric cancer.(4)The consistency of PD-L1 protein expression and gene amplification was poor,and PD-L1 protein expression positive rate was higher.