P14.02 Expression and Significance of Indoleamine 2,3 Dioxygenase on Tumor Cell and Tumor Stroma Compartments of Lung Squamous Cell Carcinoma

Abstract

Indoleamine 2,3 dioxygenase (IDO), a human immune escape factor, especially in pregnant women, is a immune suppressor that protects the fetus from maternal immune rejection. IDO, the tryptophan-metabolizing enzyme, is an important regulator of tumor immune suppression through inhibiting lymphocytic functions, and is frequently increased expression in solid tumor. This aimed to expound expression and significance of indoleamine 2,3 dioxygenase (IDO) on tumor cell (TC) and tumor stroma compartments (TSC) of lung squamous cell carcinoma (LSCC). Patients with resected specimen from 2015 to 2018 in Taizhou Hospital of Zhejiang Province were enrolled included in this study. The expressions of IDO (ab211017) in on TC and TSC of tumor tissue and adjacent tissue were evaluated by immunohistochemistry (IHC). The results of staining were scored according to the intensity of staining with Fourtier system (level 0–3: negative = 0, weakest = 1, moderate = 2, strong = 3) and staining positive rate score: 0 (negative), 1 (1-25%), 2 (26-50%), 3 (51-75%), 4 (76-100%). Total score was the product of "intensity score" and "positive rate score". And grouping was divided into that < 6 was low expression group, while ≥ 6 was divided into high expression group. Three pathologists, who were blind to all clinical and biological data, performed and analyzed IHC. A total of 86 patients with resected tissue specimen available for IHC analysis were studied. The high and low expression of IDO were identified in 37(43.02%), 49(56.98%) and 12(13.95%), 74(86.05%) on TC of tumor tissue and adjacent tissue from LSCC patients, respective. And, the high and low expression of IDO were identified in 20(23.26%), 66(76.74%) and 45(52.33%), 41(47.67%) in TSC of tumor tissue and adjacent tissue from LSCC patients, respective. Patients with high expression of IDO showed significantly poorer overall survival than those with low expression of IDO (not reached months versus 57 months respectively) (p = 0.025) on TC of tumor tissue. In the same way, the high IDO expression were showed significantly poorer overall survival than those with low expression of IDO (not reached months versus 29 months respectively) (p = 0.025) on TSC of tumor tissue. IDO expression was higher in tumor tissues than in adjacent tissues. IDO expression not only on TC but also on TSC of tumor tissue may be useful for predicting the prognosis in LSCC patients. Further studies on the correlation between IDO and PDL1 and co-expression rates need to be carried out.