Comprehensive Analysis of Stromal and Serum Markers in Gastric Cancer.

A comprehensive analysis of the cell phenotype of the inflammatory infiltrate of the tumor stroma represents a promising area of molecular oncology. The study of not only soluble forms of various immunoregulatory molecules, but also their membrane-bound forms is also considered highly relevant. We performed a comprehensive analysis of tissue and circulating forms of the PD-1 and PD-L1 proteins, as well as macrophage and B-cell markers in the tumor stroma of gastric cancer, to assess their clinical and prognostic significance. The tumor and blood plasma samples from 63 gastric cancer patients were studied using ELISA and immunohistochemistry. Malignant gastric tumors were shown to be strongly infiltrated by B-cells, and their number was comparable to that of macrophages. For PU.1 expression, an association with tumor size was observed; i.e., larger tumors were characterized by fewer PU.1+ infiltrating cells (p = 0.005). No clinical significance was found for CD20 and CD163, but their numbers were higher at earlier stages of the disease and in the absence of metastases. It was also demonstrated that the PD-L1 content in tumor cells was not associated with the clinical and morphological characteristics of GC. At the same time, PD-L1 expression in tumor stromal cells was associated with the presence of distant metastases. The analysis of the prognostic significance of all the markers studied demonstrated that CD163 was statistically significantly associated with a poor prognosis for the disease (p = 0.019). In addition, PD-L1 expression in tumor cells tended to indicate a favorable prognosis (p = 0.122). The results obtained in this work indicate that the study of soluble and tissue markers of tumor stroma is promising in prognosticating the course of GC. The search for combinations of markers seems to be highly promising, with their comprehensive analysis capable of helping personalize advanced antitumor therapy.

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.

[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.

Clinical Significance of Matrix Metalloproteinases in Blood Plasma of Patients with Gastric Cancer.

Plasma levels of MMP-2, MMP-7, and MMP-9 and their tissue inhibitor TIMP-2 were measured in 89 patients with gastric cancer and the relationship between these parameters and the main clinical morphological characteristics of the disease was analyzed. Plasma levels of the proteins were measured using standard direct ELISA kits. The level of MMP-7 in patients with gastric cancer was significantly higher than in the control group (medians 2.7 and 1.2 ng/ml, respectively; p<0.01), but only in 51% patients this parameter surpassed the upper threshold normal value (2.35 ng/ml; 95% percentile of control). The level of MMP-9 in gastric cancer patients was lower than in control group by 1.6 times (medians 167 and 267 ng/ml, respectively; p<0.01). Plasma levels of MMP-2 and TIMP-2 in patients with gastric cancer and healthy subjects were similar. No appreciable associations of plasma matrixins and TIMP-2 with the main clinical morphological characteristics of the disease were detected. The patients were followed up for 8 to 85 months (median 70.8 months). Low level of MMP-2 and high level of MMP-7 in the plasma proved to be unfavorable prognostic factors for overall survival. At MMP-2<268 ng/ml, the 5-year overall survival was 32% vs. 60% for patients with the marker level higher than this threshold value (p=0.016). The differences in overall survival in relation to their MMP-7 levels for 5-year observation did not surpass 16% (39% at marker level >2.7 ng/ml and 55% at lower level; p=0.048). Plasma levels of MMP-2 and TIMP-2 were not significantly associated with overall survival. Multivariate analysis showed that only T index (p=0.034) and plasma MMP-7 level (p=0.007) were essential for overall survival. The increase in plasma or serum MMP-7 levels is a universal phenomenon in tumors of different histogenesis, which precluded the use of this parameter as a specific diagnostic marker of gastric cancer. At the same time, it could be useful for monitoring the treatment efficiency and detection of relapses. In addition, high plasma level of MMP-7 remained an independent factor of unfavorable prognosis for overall survival of patients with gastric cancer.