sPD-1/sPD-L1 proteins in non-small cell lung cancer and esophageal squamous cell carcinoma

Background. Implementation of immunotherapy in clinical oncological practice has significantly improved the results of cancer treatment. It resulted in the need for seeking new markers to assess the effectiveness of therapy and the disease prognosis.

Aim. To analyze the content of soluble forms of PD-1 and PD-L1 immune checkpoint proteins in the blood serum of patients with non-small cell lung cancer and esophageal squamous cell carcinoma and their association with clinical and morphological characteristics of the disease and the disease prognosis.

Materials and methods. The study included tumor samples obtained from 43 patients with non-small cell lung cancer and 21 patients with esophageal squamous cell carcinoma. The concentration of sPD-L1 and sPD-1 in the blood serum was determined using enzyme-linked immunosorbent assay (ELISA). The Mann – Whitney test was used to determine statistically significant differences in independent groups. A correlation analysis was performed using the Spearman’s rank correlation coefficient. Overall survival was analyzed by constructing survival curves using the Kaplan – Meier method and a Cox proportional hazards model. The differences were considered statistically significant at p < 0.05.

Results. The study showed that sPD-1 and sPD-L1 were found in the blood serum of both cancer patients and healthy donors, and their concentrations did not differ significantly. It was shown that the high concentration of sPD-L1 in the blood serum of patients with non-small cell lung cancer was significantly associated with the late stage of the disease and was an independent unfavorable prognostic factor. It should be noted that for patients with esophageal cancer, an unfavorable prognostic marker was the high concentration of the soluble form of PD-1 protein, and not PD-L1 ligand, as in case of lung cancer.

Conclusion. The content of sPD-1 and sPD-L1 in the blood serum can have different prognostic significance for various types of cancer, and further studies are required to confirm their clinical usability.

Clinical and prognostic significance of the soluble form of the VISTA immunity control point in patients with primary bone tumors

The data of a comparative enzyme-linked immunosorbent assay of the content of the soluble form of the immunity checkpoint VISTA in the blood serum of 30 healthy donors (control group), 79 patients with primary malignant (osteosarcoma - 30, chondrosarcoma - 31, chordoma - 14) and 14 borderline (giant cell tumor) bone neoplasms are presented. In the general group of patients with malignant neoplasms of bones, the median sVISTA content in blood serum is statistically significant lower than in the control (p = 0.040). In patients with bone tumors and healthy donors over 18 years of age, there was a decrease with age in serum sVISTA levels. There were no significant differences in sVISTA concentration between patients with osteosarcoma, chondrosarcoma and healthy donors. Only in patients with chordoma were sVISTA levels statistically significant lower than in controls (p = 0.013). In the groups of patients with chondrosarcoma and osteosarcoma of the bone, there were no significant associations between the serum sVISTA content and the main clinical and morphological characteristics of the disease. In patients with osteosarcoma, no relationship was found between sVISTA levels and overall survival rates, while in patients with bone chondrosarcoma, there was a tendency towards a favorable prognosis with a high content of the marker in the blood serum.

Prognostic significance of soluble forms of immune checkpoint PD-1/PDL1 receptor and ligand in blood plasma of gastric cancer patients

Analysis of long-term treatment results of 101 primary gastric cancer patients at various stages of the tumor process followed during 1 - 41 months (median - 6,4 months) from the onset of specific treatment are presented depending on the levels of soluble forms (s) of PD-1 receptor and its ligand PD-L1 in blood plasma. Overall survival assessed by Kaplan-Meyer analysis and with the help of Cox multiparametric regression model was applied as the criterion of prognostic value. It was found that at high (≥ 35 pg/ml) sPD-L1 levels in blood plasma, the overall survival of patients with gastric cancer was statistically significantly lower than at the marker's levels below 35 pg / ml (p <0.045): 1-year survival comprised 78 and 96%, 2-year - 52 and 78%; 3-year - 40 and 61% at high and low sPD-L1 respectively. Median survival of patients with high plasma sPD-L1 comprised 29 months, of those with low sPD-L1 was not achieved during the whole follow-up period. This trend was observed not only in the total group of stage I-IV gastric cancer patients, but also in patients at the early stages of the disease, though sPD-L1 did not show an independent prognostic value in multiparametric model. At the same time, the overall survival of patients with gastric cancer did not depend on the baseline levels sPD-1 in blood plasma. Thus, soluble ligand sPD-L1 can be considered as a potentially valuable factor for prognosis of gastric cancer patients' survival, and, probably, of anti-PD-1/PD-L1 treatment efficiency, but further studies and patients' monitoring are required to prove this statement.

Soluble forms of immune checkpoints in ovarian cancer

The data of a complex immunoassay comparative study of the content of soluble forms of sPD-1, sPD-L1, sNKG2D, sNKG2DL1, sB7-H3 and sHLA-G in the blood plasma of 75 patients with epithelial ovarian cancer and 20 healthy donors of the control group are presented. The diagnostic significance of the studied proteins was determined. The study showed that the profile of soluble immunity checkpoints differs when malignant ovarian pathology occurs. There was a statistically significant decrease in the content of sPD-L1, sNKG2DL1, sB7-H3, and sHLA-G in the blood plasma of patients compared with the control group. Differences were found in the content of the studied markers depending on the histological type of tumors. Correlations between the soluble forms of some of the studied proteins are shown, indicating the presence of independent mechanisms of immune regulation in ovarian cancer, which may explain the insufficient effectiveness of the existing immunotherapy for this type of tumor. The results obtained will undoubtedly facilitate the development of new effective methods for the diagnostics and therapy of ovarian cancer.

Comparative analysis of the levels of soluble forms of receptor and ligand of the immunity control point PD-1/PD-L1 in the blood serum of patients with typical bone osteosarcoma and chondrosarcoma

Results of ELISA investigation of the pretreatment sPD-1 and sPD-L1 content in blood serum of 133 bone neoplasms patients aged 6-70 years and 57 practically healthy control persons aged 12-70 years are described. In 14 patients the neoplasms were of a benign character, in 16 - borderline giant-cell bone tumor was diagnosed, and in 103 - malignant bone lesions including 39 osteosarcomas and 42 chondrosarcomas were revealed. The sPD-1 receptor concentrations in blood serum did not differ between control healthy persons and primary bone tumor patients, while serum sPD-L1 level in bone tumor patients was statistically significantly increased (p<0.0000001). By means of ROC curve construction a cut-off sPD-L1 level of 16.5 pg/ml was found that imposed 75,9% sensitivity and 75,4% specificity in relation to healthy control. However, the frequency of sPD-L1 levels exceeding 16.5 pg/ml was approximately similar in benign, borderline and malignant bone tumor patients. Analysis of the pattern of sPD-1 and sPD-L1 circulation in the peripheral blood of patients with the most prevalent malignant bone tumors - osteosarcoma and chondrosarcoma - demonstrated that in both sarcoma types sPD-L1 level was significantly higher than in control, but in patients with chondrogenic tumors the soluble ligand sPD-L1 dominates in the circulation, while in those with osteogenic tumors - sPD-1 receptor prevails. In particular, sPD-1 level is statistically significantly higher in patients with typical osteosarcoma than in those with typical chondrosarcoma (p=0.002437), and sPD-L1/sPD-1 concentration ratio in chondrosarcoma is highly significantly more than 2-fold higher than in osteosarcoma (0.81 and 0.35 respectively; p=0.000284). The sensitivity of sPD-L1 ≥16.5 pg/ml test in typical osteosarcoma patients' group comprised only 70.2%, and in those with typical chondrosarcoma - 84.6%. Serum sPD-1 and sPD-L1 concentrations in osteosarcoma and chondrosarcoma patients were not associated with the indices of tumor advancement, its histological grade, localization in the osseous system, and type of affected bone. Thus, it can be concluded that the ratio between circulating soluble forms of the receptor and the ligand of PD-1/PD-L signaling pathway differs between patients with chondrogenic and those with osteogenic tumors, sPD-L1 being diagnostically valuable mostly for chondrogenic bone neoplasms.

[The content of the soluble forms PD-1 and PD-L1 in blood serum of patients with gastric cancer and their relationship with clinical and morphological characteristics of the disease.]

Results of comparative ELISA investigation of pretreatment sPD-1 and sPD-L1 content in blood plasma of 100 gastric cancer patients at various disease stages aged 25 to 81 years are presented. Control group included 60 practically healthy donors aged 18 - 68 years. Plasma sPD-L1 concentrations did not differ between gastric cancer patients and control group, and sPD-1 levels were statistically significantly lower in patients than in healthy donors (p<0.0001). Positive correlation (R=0.38; p=0.003) was revealed between plasma sPD-1 и sPD-L1 levels in control group and negative (R= -0.26; p=0,009) - in gastric cancer patients. ROC curve revealed the best sPD-1 cut-off level (< 21 pg/ml) with 77% sensitivity and 63.3% specificity, which is not sufficient for its application as diagnostic marker. Statistically significant increase of plasma sPD-L1 from stage I to stage IIIC (R=0.50; p=0.000011) was found. Analysis of associations between the evaluated markers' levels and indices of gastric cancer expansion according to TNM system revealed statistically significant positive associations of plasma sPD -L1 levels with T (tumor invasiondepth) and N (number of affected lymph nodes) indices: R=0.33; p=0.00093, and R=0.27; p=0.0099 respectively. sPD-L1 level was significantly increased in patients with low differentiated adenocarcinoma and cricoid-cell cancer as compared to highly differentiated adenocarcinoma (p=0.02 and p=0.004 respectively); in patients with cricoid-cell cancer it was also higher than in those with moderately differentiated adenocarcinoma (p=0.043) and undifferentiated cancer (p=0.049). Plasma sPD-1 level did not depend on disease stage, TNM system indices and tumor histological structure. Thus, soluble ligand sPD-L1, but not its receptor sPD-1, plasma level is increased in patients with unfavorable clinical and morphological characteristics, may be regarded as potentially valuable prognostic factor for gastric cancer patients' survival, and probably as a predictor of anti - PD-1/PD-L1 treatment efficiency.