PD-L1 and B7-H3 are Effective Prognostic Factors and Potential Therapeutic Targets for High-Risk Thyroid Cancer

The prognosis of thyroid cancer in patients varies significantly based on different pathological types or distinct clinical situations. Investigating the expression of immune checkpoint molecules PD-L1 and B7-H3 in high-risk thyroid cancer and their correlation with clinicopathological features and prognosis will contribute to the development of novel therapeutic strategies. A retrospective sample of 202 patients with thyroid cancer who underwent surgery at the Cancer Hospital of the Chinese Academy of Medical Sciences was collected, including 33 cases of anaplastic thyroid cancer (ATC), 21 cases of differentiated thyroid cancer (DTC) with distant metastasis (DM), 7 cases of differentiated high-grade thyroid carcinoma (DHGTC), and 109 cases of aggressive subtypes of papillary thyroid carcinoma (PTC) (including 28 cases of tall cell PTC, 31 cases of diffuse sclerosing PTC, 20 cases of solid PTC, 15 cases of columnar cell PTC, and 15 cases of hobnail PTC). In the control group, there were 32 cases of classic PTC. The differences in protein expression between PD-L1 and B7-H3 in several high-risk thyroid cancers and normal tissues and controls were compared by immunohistochemical staining, and the clinicopathological features and prognostic relevance were statistically analyzed. The expression of PD-L1 in ATC (P < 0.001), tall cell PTC (P = 0.031), and DHGTC (P = 0.003) was significantly higher than that in classic PTC. The expression of B7-H3 in ATC (P < 0.001), DTC with DM (P = 0.001), diffuse sclerosing PTC (P = 0.013), columnar cell PTC (P = 0.007), solid PTC (P < 0.001), hobnail PTC (P < 0.001), and DHGTC (P < 0.001) was significantly higher than that in classic PTC. In ATC, PD-L1 expression correlated significantly with extrathyroidal extension (ETE) (P = 0.027) and B7-H3 expression correlated significantly with male patients (P = 0.031) and lymph node metastasis (LNM) (P = 0.026). The positive expression of B7-H3 (P = 0.041) was an independent risk factor for disease progression in ATC. B7-H3 positive expression (P = 0.049), PD-L1 positive expression (P = 0.015), and tumor diameter ≥ 2 cm (P = 0.038) were independent risk factors for disease progression in patients with DTC with DM. PD-L1 positive expression (P = 0.019) and tumor diameter ≥ 2 cm (P = 0.018) were independent risk factors for disease progression in patients with aggressive subtypes of PTC. B7-H3 and PD-L1 are expected to be effective prognostic indicators for patients with aggressive thyroid cancer, which can help in optimization of individualized treatment strategies. Immunotherapy targeting these two molecules may provide new and complementary ideas for the treatment of high-risk/refractory thyroid cancer.