Although blood monocytes exhibit significant cytotoxic activity against tumor cells, the function of tumor infiltrating macrophages (TIM) is depressed in cancer patients. This study addresses the question of how the antitumor response of human monocytes, assessed by production of cytokines (tumor necrosis factor alpha, TNF; IL-10; IL-12p40) and cytotoxicity, is altered by exposure to cancer cells. Tumor cell--pre-exposed monocytes restimulated with tumor cells showed significantly decreased production of TNF, IL-12, increased IL-10 (mRNA and release) and inhibition of IL-1 receptor-associated kinase-1 (IRAK-1) expression. This down-regulation of cytokine production was selective, as the response of pre-exposed monocytes to lipopolysaccharide (LPS) was unaffected. Treatment of tumor cell--pre-exposed monocytes with hyaluronidase (HAase) improved their depressed production of TNF, while HAase-treated cancer cells did not cause monocyte dysfunction. The response of hyaluronan (HA)--pre-exposed monocytes to stimulation with tumor cells was also inhibited. Cytotoxic activity of monocytes pretreated with cancer cells was also decreased. This study shows that tumor cells selectively deactivate monocytes and suggests that tumor cell-derived HA by blocking CD44 on monocytes inhibits their antitumor response. These observations may provide some explanation for the depressed function of TIM in human malignancy.

BackgroundNeutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), and lymphocyte-monocyte ratio (LMR) may serve as a simple index of the immune function. The aim of this study was to investigate the prognostic significance of NLR, PLR, and LMR in patients with resectable pancreatic ductal adenocarcinoma (PDAC) and to verify whether such biomarkers are associated with changes in populations of lymphoid cells.MethodsThe prognostic implications of blood count parameters were evaluated in a retrospective cohort of 442 subjects undergoing pancreatic resections for PDAC. Subpopulations of lymphocytes and monocytes in peripheral blood were identified by FACS in a prospective cohort of 54 patients.ResultsIn the univariate analysis, NLR < 5 and LMR ≥ 3 were associated with significantly longer median survival of 25.7 vs 12.6 months and 29.2 vs 13.1 months, respectively. PLR did not influence survival. The Cox proportional hazards model showed that high NLR (HR 1.66, 95 % CI 1.12 to 2.46, P = 0.012) and low LMR (HR 1.65, 95 % CI 1.06 to 2.58, P = 0.026) were independent predictors of poor prognosis. NLR ≥ 5 and LMR < 3 correlated with an approximately twofold decrease in counts of helper and cytotoxic T cells, B cells, and NK cells. High NLR was also accompanied with increased neutrophil counts, while low LMR showed increased numbers of monocytes, mostly classical.ConclusionsNLR and LMR may carry important prognostic information for patients with resected PDAC. The unfavorable prognosis likely correlates with reduced numbers of immune cells effective against the tumor and increased populations of cells involved in immune suppression.

SummaryThe present study examined the ability of human monocytes to produce reactive oxygen intermediates after a contact with tumour cells. Monocytes generated oxygen radicals, as measured by luminol-enhanced chemiluminescence and superoxide anion production, after stimulation with the tumour, but not with untransformed, cells. The use of specific oxygen radical scavengers and inhibitors, superoxide dismutase, catalase, dimethyl sulphoxide and deferoxamine as well as the myeloperoxidase inhibitor 4-aminobenzoic acid hydrazide, indicated that chemiluminescence was dependent on the production of superoxide anion and hydroxyl radical and the presence of myeloperoxidase. The tumour cell-induced chemiluminescent response of monocytes showed different kinetics from that seen after activation of monocytes with phorbol ester. These results indicate that human monocytes can be directly stimulated by tumour cells for reactive oxygen intermediate production. Spontaneous monocyte-mediated cytotoxicity towards cancer cells was inhibited by superoxide dismutase, catalase, deferoxamine and hydrazide, implicating the role of superoxide anion, hydrogen peroxide, hydroxyl radical and hypohalite. We wish to suggest that so-called 'spontaneous' tumoricidal capacity of freshly isolated human monocytes may in fact be an inducible event associated with generation of reactive oxygen intermediates and perhaps other toxic mediators, resulting from a contact of monocytes with tumour cells.

Melatonin and L-tryptophan protect the gastric mucosa from damage by stress and ischaemia reperfusion, and this action is mediated, at least in part, by the limitation in the free radicals, the stimulation of mucosal generation of PG and by the increase in gastric blood flow.