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Programmed death (PD)-1/PD-ligand 1 (PD-L1) antibodies have shown an intense clinical effect in some patients with PD-L1

Programmed cell death-1 (PD-1) and PD-1 ligand 1 (PD-L1) are target molecules for immunotherapy in non-small cell lung cancer. PD-L1 is expressed not only in cancer cells, but also on macrophages, and has been suggested to contribute to macrophage-mediated immune suppression. We examined the clinical significance of PD-L1 expression on macrophages in human lung adenocarcinoma. The mechanism of PD-L1 overexpression on macrophages was investigated by means of cell culture studies and animal studies. The results showed that high PD-L1 expression on macrophages was correlated with the presence of EGFR mutation, a lower cancer grade, and a shorter cancer-specific overall survival. In an in vitro study using lung cancer cell lines and human monocyte-derived macrophages, the conditioned medium from cancer cells was found to up-regulate PD-L1 expression on macrophages via STAT3 activation, and a cytokine array revealed that granulocyte-macrophage colony-stimulating factor (GM-CSF) was a candidate factor that induced PD-L1 expression. Culture studies using recombinant GM-CSF, neutralizing antibody, and inhibitors indicated that PD-L1 overexpression was induced via STAT3 activation by GM-CSF derived from cancer cells. In a murine Lewis lung carcinoma model, anti-GM-CSF therapy inhibited cancer development via the suppression of macrophage infiltration and the promotion of lymphocyte infiltration into cancer tissue; however, the PD-L1 expression on macrophages remained unchanged. PD-L1 overexpression on macrophages via the GM-CSF/STAT3 pathway was suggested to promote cancer progression in lung adenocarcinoma. Cancer cell-derived GM-CSF might be a promising target for anti-lung cancer therapy.

CD163 is one of the scavenger receptors expressed on macrophages. However, several immunohistochemical studies have demonstrated that CD163 is also detected on cancer cells, and is associated with a poor prognosis. In the present study, we detected CD163 staining on cancer cells in lung adenocarcinoma and squamous cell carcinoma (SCC), and investigated the relationship between CD163 on cancer cells and the clinical prognosis. CD163 staining was seen in 128 of 342 adenocarcinoma cases and 35 of 103 SCC cases. Among the lung adenocarcinoma cases, the progression-free survival and overall survival were significantly shorter in the CD163 high group than the CD163 low group. A similar trend was observed among the SCC cases, but the difference was not statistically significant. Additionally, a higher number of macrophages was detected in areas with CD163-positive cancer cells when compared to areas with CD163-negative cancer cells. In summary, we found that CD163-positive cancer cells are a predictor of a worse clinical course in lung adenocarcinoma and SCC.

Tumor-associated calcium signal transducer 2 (TROP2) is a cell-surface glycoprotein involved in the high malignant potential of several cancers. Antibody-drug conjugates that target TROP2 represent a promising approach for the treatment of TROP2-expressing cancers including lung cancer and breast cancer. TROP2 expression was tested by immunohistochemistry in lung adenocarcinoma (ADC) and squamous cell carcinoma samples, and its correlation with clinicopathological factors, including survival rate and p53 mutation, was statistically analyzed. We found that increased TROP2 expression was significantly associated with a poor clinical course in patients with ADC, but not in patients with squamous cell carcinoma. A more significant association with poor outcome was seen in ADC cases with a high histological grade as well as those without the epidermal growth factor receptor (EGFR) mutation. A significant correlation between TROP2 expression and abnormal p53 nuclear accumulation/expression was also found in ADC. In the present study, we discovered a significant correlation between TROP2 expression and p53 mutation in ADC, and that TROP2 expression was a prognostic factor in ADC cases with a high histological grade as well as those without the EGFR mutation. Signals mediated by mutated p53 might influence TROP2 expression in ADC.