Clinical significance of programmed cell death-ligand expression in small bowel adenocarcinoma is determined by the tumor microenvironment

BACKGROUND Comprehensive genomic analysis has shown that small bowel adenocarcinoma(SBA)has different genomic profiles from gastric and colorectal cancers.Hence,it is essential to establish chemotherapeutic regimens based on SBA characteristics.The expression of programmed cell death-ligand 1(PD-L1)and programmed cell death-ligand 2(PD-L2)in SBA is not fully understood.Anti-PD-L1/PD-1 therapy uses tumor-infiltrating lymphocytes(TILs);therefore,the status of TILs in the tumor microenvironment(TME)may influence their efficacy.The ratio of FoxP3+to CD8+T cells has been reported to be useful in predicting the prognosis of digestive system cancers.AIM To investigate the clinicopathological significance of PD-L1/2 expression according to the status of TILs in SBA tissues.METHODS We performed immunohistochemical analysis for PD-L1,PD-L2,CD8,FoxP3,and DNA mismatch repair(MMR)proteins using formalin-fixed,paraffin-embedded tissues from 50 patients diagnosed with primary SBA.The immunoreactivities of PD-L1 and PD-L2 were determined separately in tumor cells and tumor-infiltrating immune cells throughout the tumor center and invasive margins,and finally evaluated using the combined positive score(CPS).We assessed CD8+and FoxP3+T cells in the intratumoral and tumor-surrounding stroma.Subsequently,we calculated and summed the ratio of FoxP3 to CD8+T cell counts.Immune-related cell densities were graded as low or high.Immunohistochemical results were compared with clinicopathological factors and patient prognosis.The distribution of cancer-specific survival(CSS)was estimated using the Kaplan–Meier method,and the log-rank test was used to test for significant differences in CSS.A Cox proportional hazard model was also used to assess the effect of tumor variables on CSS.RESULTS PD-L1 expression was positive in 34%in tumor cells(T-PD-L1)and 54%in tumor-infiltrating immune cells(I-PDL1)of the cases examined.T-PD-L2 was positive in 34%and I-PD-L2 was positive in 42%of the cases.PD-L1 CPS≥10 and PD-L2 CPS≥10 were observed in 50%and 56%of the cases,respectively.Deficient MMR(dMMR)was 14%of the cases.T-PD-L1,I-PD-L1 and PD-L1 CPS≥10 were all significantly associated with dMMR(P=0.037,P=0.009,and P=0.005,respectively).T-PD-L1,I-PD-L1,and PD-L1 CPS≥10 were all associated with deeper depth of invasion(P=0.001,P=0.024,and P=0.002,respectively).I-PD-L2 expression and PD-L2 CPS≥10 were significantly higher in the differentiated histological type(P=0.015 and P=0.030,respectively).The I-PD-L1 and IPD-L2 levels were significantly associated with better CSS(P=0.037 and P=0.015,respectively).CD8-high was significantly associated with less lymph node metastasis(P=0.047),less distant metastasis(P=0.024),less peritoneal dissemination(P=0.034),and earlier TNM stage(P=0.047).The CD8-high group had better prognosis than the CD8-low group(P=0.018).FoxP3 expression was not associated with any clinicopathological factors or prognosis.We found that patients with PD-L2 CPS≥10 tended to have worse prognosis in the FoxP3/CD8-low group(P=0.088).CONCLUSION The clinicopathological significance of PD-L1/2 expression may differ depending on the TME status.Immune checkpoint inhibitors may improve the prognosis of SBA patients with low FoxP3/CD8 ratio and PD-L2 expression.

Risk factors for small intestinal adenocarcinomas that are common in the proximal small intestine

The frequency of primary small intestinal adenocarcinoma is increasing but is still low.Its frequency is approximately 3%of that of colorectal adenocarcinoma.Considering that the small intestine occupies 90%of the surface area of the gastrointestinal tract,small intestinal adenocarcinoma is very rare.The main site of small intestinal adenocarcinoma is the proximal small intestine.Based on this characteristic,dietary animal proteins/lipids and bile concentrations are implicated and reported to be involved in carcinogenesis.Since most nutrients are absorbed in the proximal small intestine,the effect of absorbable intestinal content is a suitable explanation for why small intestinal adenocarcinoma is more common in the proximal small intestine.The proportion of aerobic bacteria is high in the proximal small intestine,but the absolute number of bacteria is low.In addition,the length and density of villi are greater in the proximal small intestine.However,the involvement of villi is considered to be low because the number of small intestinal adenocarcinomas is much smaller than that of colorectal adenocarcinomas.On the other hand,the reason for the low incidence of small intestinal adenocarcinoma in the distal small intestine may be that immune organs reside there.Genetic and disease factors increase the likelihood of small intestinal adenocarcinoma.In carcinogenesis experiments in which the positions of the small and large intestines were exchanged,tumors still occurred in the large intestinal mucosa more often.In other words,the influence of the intestinal contents is small,and there is a large difference in epithelial properties between the small intestine and the large intestine.In conclusion,small intestinal adenocarcinoma is rare compared to large intestinal adenocarcinoma due to the nature of the epithelium.It is reasonable to assume that diet is a trigger for small intestinal adenocarcinoma.