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Gastric cancer is the fifth most common type of malignancy in the world (over one million cases in 2018) and the third leading cause of cancer-related deaths worldwide (783 000 deaths in 2018). 1 In Spain, expected figures are 7963 estimated new cases in 2020 and 5809 deaths. Clinical symptoms of gastric cancer appear late in the evolution of the disease, and this may limit the early detection of the pathology and the patients' therapeutic options; thus, upon diagnosis of gastric cancer, prognosis is poor (5-year survival rate below 29%). The need for early diagnosis and prognosis criteria has led recent research to focus on the investigation of novel biomarkers which could help identify patients at risk of developing more threatening

We have taken advantage of a recently described technique of transformation and immortalization of T lymphocytes using the lymphotropic Herpesvirus saimiri, to achieve long-lasting T-cell lines from gastric cancer patients and healthy volunteers. Blood samples were drawn and T lymphocytes were transformed. Once sustained growth was observed, lines were subjected to phenotypic and functional analyses, and the results compared with freshly isolated peripheral blood mononuclear cells. Cytofluorometric analysis revealed that CD3 and CD45 were found at lower proportion in primary cells from patients than from control individuals (54% vs 75%, p<0.001, 90% vs 96%, p<0.05, respectively), and in HVS-derived T-cell lines (90% vs 98%, p<0.05, 97% vs 100%, p<0.05, respectively). Proliferative analyses showed that primary isolated cells were unable to respond adequately to CD3-, CD2-, and PHA-mediated stimulation, as compared to controls. Similarly, T-cell lines from patients proliferated to a lesser extent when CD3- and CD2-mediated stimuli were considered, especially when simultaneous stimulation via CD3 and CD2 molecules was carried out (47,824 counts per minute [cpm] vs 121,478 cpm, p<0.05). Altogether these results show that the defects reported in T cells from patients with cancer are not exclusively due to tumour-derived factors, since the alterations persist in long-lasting, HVS-transformed, T-cell lines, suggesting that this model seems a suitable one to disclose them.

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Background. Reduced TCRζ chain surface has been reported in T cells from patients with different inflammatory conditions and cancer. However, the causes of this diminished expression in cancer remain elusive. Methods. T cell-enriched populations of blood or tissue (tumoral and nontumoral) origin from 44 patients with gastric adenocarcinoma and 33 healthy subjects were obtained. Samples were subjected to cytofluorimetry, Western blot analysis, TCRζ cDNA sequencing experiments, measurement of TCRζ mRNA levels, and caspase-3 activity assays. Results. Cytofluorimetry revealed a decreased TCRζ expression in T cells of patients, assessed either as percentage of cells expressing this chain (blood: control subjects 99.8 ± 0.1 % , patients 98.8 ± 1.1 % P < 0.001 ; tissue: control subjects 96.7 ± 0.9 % , patients tumoral tissue 67.9 ± 27.0 % , patients nontumoral tissue 82.8 ± 12.6 % , P = 0.019 ) or mean fluorescence intensity (MFI) value (blood: control subjects 102.2 ± 26.0 ; patients 58.0 ± 12.3 , P = 0.001 ; tissue: control subjects 99.4 ± 21.4 ; patients tumoral tissue 41.6 ± 21.4 ; patients nontumoral tissue 62.3 ± 16.6 , P = 0.001 ). Other chains pertaining to the TCR-CD3 complex (CD3ε) showed no significant differences (MFI values). Subsequent TCRζ cDNA sequencing experiments or measurements of TCRζ mRNA levels disclosed no differences between patients and control subjects. Evaluation of caspase-3 activity showed higher levels in T cell extracts of patients, and this activity could be decreased by 70% with the use of the inhibitor Ac-DEVD-FMK, although CD3ζ expression levels did not recover. Conclusions. These results further place the defect responsible for the low TCRζ expression in cancer at the posttranscriptional level and suggests contrary to what has been proposed in other pathologies that elevated caspase-3 activity is not the causative agent.