PGE2 Released by Pancreatic Cancer Cells Undergoing ER Stress Transfers the Stress to DCs Impairing Their Immune Function.

This study shows that pancreatic cancer cells undergoing cell death by valproic acid (VPA) treatment activated dendritic cells (DCs) more efficiently than those treated with trichostatin A (TSA), as demonstrated by CD86 and CD80 surface expression. Surprisingly though, DCs cultured in the presence of supernatant derived from VPA-treated cancer cells showed a reduced allostimulatory capacity and an increased release of IL10 and IL8 cytokines in comparison with those exposed to TSA-treated cell culture supernatant. Searching for molecular mechanisms leading to such differences, we found that VPA treatment dysregulated choline metabolism and triggered a stronger endoplasmic reticulum (ER) stress in pancreatic cancer cells than TSA, upregulating CCAAT/enhancer-binding protein homologous protein, and activated cyclooxygenase-2, thus promoting the release of prostaglandin (PG) E2. Interestingly, dysfunctional DCs cultured in the presence of VPA-treated cells culture supernatant showed a higher level of intracellular reactive oxygen species, 4-hydroxy-trans-2-nonenal protein adducts, and ER stress, as evidenced by the upregulation of spliced X-box binding protein 1 (XBP1s), effects that were reduced when DCs were exposed to supernatant of cancer cells treated with Celecoxib before VPA. Celecoxib prevented PGE2 release, restoring the function of DCs exposed to VPA-treated cells culture supernatant, and a similar effect was obtained by silencing XBP1s in DCs treated with VPA-treated cells culture supernatant. These results suggest that PGE2 could be one of the yet unidentified factors able to transfer the stress from cancer cells to DCs, resulting in an impairment of their function.

Impact of chronic exposure to bevacizumab on EpCAM-based detection of circulating tumor cells.

BACKGROUND: Circulating tumor cells (CTCs) are often undetected through the immunomagnetic epithelial cell adhesion molecule (EpCAM)-based CellSearch(®) System in breast and colorectal cancer (CRC) patients treated with bevacizumab (BEV), where low CTC numbers have been reported even in patients with evidence of progression of disease. To date, the reasons for this discrepancy have not been clarified. This study was carried out to investigate the molecular and phenotypic changes in CRC cells after chronic exposure to BEV in vitro. METHODS: The human CRC cell line WiDr was exposed to a clinically relevant dose of BEV for 3 months in vitro. The expression of epithelial and mesenchymal markers and EpCAM isoforms was determined by western blotting and immunofluorescence. To evaluate the impact of EpCAM variant isoforms expression on CTC enumeration by CellSearch(®), untreated and treated colon cancer cells were spiked into 7.5 mL of blood from a healthy donor and enumerated by CellSearch(®). RESULTS: Chronic exposure of CRC cell line to BEV induced decreased expression of EpCAM 40 kDa isoform and increased expression EpCAM 42 kDa isoform, together with a decreased expression of cytokeratins (CK), while no evidence of epithelial to mesenchymal transition (EMT) in treated cells was observed. The recovery rate of cells through CellSearch(®) was gradually reduced in course of treatment with BEV, being 84%, 70% and 40% at 1, 2 and 3 months, respectively. CONCLUSIONS: We hypothesize that BEV may prevent CellSearch(®) from capturing CTCs through altering EpCAM isoforms.

Clopidogrel plus indobufen in acute coronary syndrome patients with hypersensitivity to aspirin undergoing percutaneous coronary intervention.

The prescription of aspirin (acetylsalicylic acid (ASA)) to patients with a history of hypersensitivity to this drug could prove harmful. The aim of the study was to assess the antiplatelet activity and safety of a combined antiplatelet treatment with indobufen and clopidogrel in acute coronary syndrome (ACS) patients with hypersensitivity to aspirin, undergoing coronary stenting. Forty-two consecutive ACS patients treated with stent implantation were randomly assigned to receive clopidogrel 75 mg daily (loading dose 300 mg) plus indobufen 100 mg twice a day (group A), or clopidogrel 75 mg daily, after 300 mg of loading dose (group B). Platelet activity and safety were monitored in both groups at 1, 3, 6, 12, and 18 months with laboratory and clinical evaluation. A lower value of max % platelet aggregation to arachidonic acid and collagen was found in group A compared to group B (31.79 ± 27.33 vs. 73.67 ± 19.92; p < 0.0001 and 28.53 ± 21.32 vs. 73.58 ± 17.71; p < 0.0001, respectively). There was no difference in max % of platelet inhibition to adenosine diphosphate between the two groups (14.23 ± 18.92 vs. 10.30 ± 18.97; p = 0.23). In the population that was under indobufen treatment, the serum thromboxane B2 (TXB2) production at 1 week and 1 month was very low (2.6 ± 1.6 ng/ml and 3.0 ± 2.7 ng/ml, respectively; p = 0.82). The combined treatment was well tolerated in group A patients. This study suggests that the combined antiplatelet treatment with clopidogrel and indobufen could be a good option in ACS patients with hypersensitivity to aspirin undergoing coronary stenting.

Reduction of cAMP and cGMP inhibitory effects in human platelets by MRP4-mediated transport.

Cyclic nucleotide-dependent inhibition of platelets represents the most important physiological way to limit thrombus formation. cAMP and cGMP increase in platelets as a consequence of prostacyclin and nitric oxide production by endothelial cells and act through PKA and PKG, respectively. The cytosolic concentration of cyclic nucleotides in platelets is regulated by AC- and GC-dependent synthesis and PDE-dependent degradation. In some cells cyclic nucleotides are eliminated also through MRP4/5/8-dependent efflux. As only MRP4 is expressed in platelets, at high levels in dense granules, we determined its role in the elimination of cyclic nucleotides from platelet cytosol. We studied the effects of MRP4 inhibition on cAMP/cGMP effects in platelets. Cyclic nucleotide inhibitory effects triggered by cAMP and cGMP-elevating agents on platelet aggregation are strongly enhanced by MRP4 inhibition and so is cyclic nucleotide-dependent phosphorylation of the common substrate VASP. MRP4 inhibition decreases cAMP concentration in platelet granules and both cAMP and cGMP compete with an established substrate of MRP4 (fluo-cAMP) for entrance in granules. Here we provide the first evidence of the transport of cyclic nucleotides mediated by MRP4 as part of their physiological mechanism of elimination in human platelets, which might represent a novel target to increase cyclic nucleotide-dependent inhibition.

Predictors of thromboxane levels in patients with non-ST-elevation acute coronary syndromes on chronic aspirin therapy.

High levels of thromboxane A2 (TxA2), a key mediator of platelet activation and aggregation, are associated with an increased risk of cardiovascular events. We aimed at assessing the predictors of higher plasma levels of TxB2, the stable metabolite of TxA2, in consecutive patients presenting with non-ST-elevation acute coronary syndrome (NSTE-ACS) on previous aspirin (ASA) treatment undergoing coronary angiography. Ninety-eight consecutive patients (age 61 ± 11, 75% males) with NSTE-ACS, on previous chronic ASA treatment, were prospectively enrolled in this study. Coronary disease extent was assessed by angiography according to the Bogaty score. In all patients, admission plasma levels of TxB2 (pg/ml) were measured by enzyme-linked immunosorbent assay, and patients showing TxB2 levels in the fourth quartile were compared to patients showing TxB2 levels in the lower quartiles. Multivariable logistic regression analysis showed that platelet count (odds ratio [OR] 1.18, 95% confidence interval [CI] 1.02-1.63, p=0.04), multivessel coronary disease (OR 1.37, 95% CI 1.13-3.67, p=0.03), and coronary atherosclerosis extent index (OR 1.91, 95% CI 1.45-6.79, p=0.001) were independent predictors of TxB2 level upper quartile. Of note, C-reactive protein serum levels were similar in patients with TxB2 levels in the upper quartile as compared to those in the lower quartiles (p=0.49). In conclusion, NSTE-ACS patients with severe coronary atherosclerosis may have incomplete suppression of TxA2 production despite chronic ASA therapy. This finding suggests that additional efforts should be made to lower TxA2 levels in patients with widespread coronary artery disease.