Integrative analysis identifies activated anti-tumor immune microenvironment in lung metastasis of pancreatic cancer.

BACKGROUND

Although the prognosis of patients experiencing recurrences after surgery for pancreatic cancer is extremely poor, patients who develop recurrence in the lung have a better prognosis compared to other types of recurrence. We performed a histo-immunological analysis of the metastatic specimens to identify specific features of this patient subgroup.

METHODS

We performed immunohistochemistry for CD4+, CD8+, CD45RO+, Foxp3, and PD-L1 in the lung (n = 22), peritoneal (n = 18), and liver (n = 6) metastases of pancreatic cancer. As microenvironmental and immunonutritional investigations, the tumor-stroma ratio and prognostic nutritional index (PNI) were utilized in the integrative analysis of immunological features.

RESULTS

We identified significantly increased tumor-infiltrating CD4+, CD8+, and CD45RO+ cells in lung metastasis, compared with peritoneal and liver metastases (lung vs. peritoneum/liver, CD4: P < 0.001/P = 0.015, CD8: P < 0.001/P = 0.038, CD45RO: P = 0.022/P = 0.012). The CD8/Foxp3 ratio was higher in the lung than in the liver (P = 0.024). PD-L1 expression was significantly higher in lung metastasis than in peritoneal metastasis (P = 0.010). Furthermore, we found that lung metastasis had fewer cancer stroma than peritoneal metastasis (P < 0.001). A higher PNI was observed in patients with lung metastasis, and PNI was positively correlated with tumor-infiltrating lymphocytes in metastatic sites.

CONCLUSION

We identified that lung metastasis revealed an immunologically "hot" tumor with increased TILs and PD-L1 expression. This specific feature suggests that patients with lung metastasis can be candidates for immunotherapy, such as immune checkpoint inhibitors; therefore, our study provides a framework for developing individualized treatment strategies for this patient subgroup.