Immunosuppressive tumor microenvironment of usual interstitial pneumonia-associated squamous cell carcinoma of the lung

Purpose Patients with usual interstitial pneumonia (UIP) often develop lung cancer. However, the biological features of lung cancer associated with UIP remain unknown. The aim of this study was to elucidate the clinicopathological characteristics of UIP-associated squamous cell carcinoma (SqCC). Methods A total of 244 patients with p-stage I lung SqCC who underwent complete surgical resection were enrolled in this study. Clinicopathological differences between UIP-associated SqCC and non-UIP SqCC were examined. Moreover, we performed immunohistochemical studies to clarify the biological differences between these two groups. Results UIP-associated SqCC was detected in 19 patients (6.0%). Patients with UIP-associated SqCC tended to have shorter recurrence-free survival (RFS) (5-year RFS; UIP-associated SqCC 44% vs non-UIP SqCC 62%, p = 0.05). Immunohistochemical analysis revealed that the expression scores of cancer stem cell- and invasion-related molecules in cancer cells were not significantly different between the two groups. However, PD-L1 expression in cancer cells was significantly higher in UIP-associated SqCC (median score; 5.0 vs 0, p < 0.01). In the stroma of UIP-associated SqCC, the number of Foxp3(+) tumor-infiltrating lymphocytes was significantly higher than that in non-UIP SqCC (median number 43/HPF vs 24/HPF, p < 0.01). In addition, CD8(+)/Foxp3(+) T-cell ratio in UIP-associated SqCC was significantly lower than that in non-UIP SqCC (median ratio 1.8 vs 3.4, p < 0.01). Conclusion Our current study clearly revealed that the establishment of an immunosuppressive tumor microenvironment is a characteristic feature of UIP-associated SqCC, which can be correlated with poor prognosis in UIP-associated SqCC.