Cell death sensitization of leukemia cells by opioid receptor activation

Cyclic AMP (cAMP) regulates a number of cellular processes and modulates cell death induction. cAMP levels are altered upon stimulation of specific G-protein-coupled receptors inhibiting or activating adenylyl cyclases. Opioid receptor stimulation can activate inhibitory Gi-proteins which in turn block adenylyl cyclase activity reducing cAMP. Opioids such as D,L-methadone induce cell death in leukemia cells. However, the mechanism how opioids trigger apoptosis and activate caspases in leukemia cells is not understood. In this study, we demonstrate that downregulation of cAMP induced by opioid receptor activation using the opioid D,L-methadone kills and sensitizes leukemia cells for doxorubicin treatment. Enhancing cAMP levels by blocking opioid-receptor signaling strongly reduced D,L-methadone-induced apoptosis, caspase activation and doxorubicin-sensitivity. Induction of cell death in leukemia cells by activation of opioid receptors using the opioid D,L-methadone depends on critical levels of opioid receptor expression on the cell surface. Doxorubicin increased opioid receptor expression in leukemia cells. In addition, the opioid D,L-methadone increased doxorubicin uptake and decreased doxorubicin efflux in leukemia cells, suggesting that the opioid D,L-methadone as well as doxorubicin mutually increase their cytotoxic potential. Furthermore, we found that opioid receptor activation using D,L-methadone alone or in addition to doxorubicin inhibits tumor growth significantly in vivo. These results demonstrate that opioid receptor activation via triggering the downregulation of cAMP induces apoptosis, activates caspases and sensitizes leukemia cells for doxorubicin treatment. Hence, opioid receptor activation seems to be a promising strategy to improve anticancer therapies

Oxaliplatin-DNA adduct formation in white blood cells of cancer patients

In this study, we investigated the kinetics of oxaliplatin-DNA adduct formation in white blood cells of cancer patients in relation to efficacy as well as oxaliplatin-associated neurotoxicity. Thirty-seven patients with various solid tumours received 130 mg m−2 oxaliplatin as a 2-h infusion. Oxaliplatin-DNA adduct levels were measured in the first cycle using adsorptive stripping voltammetry. Platinum concentrations were measured in ultrafiltrate and plasma using a validated flameless atomic absorption spectrometry method. DNA adduct levels showed a characteristic time course, but were not correlated to platinum pharmacokinetics and varied considerably among individuals. In patients showing tumour response, adduct levels after 24 and 48 h were significantly higher than in nonresponders. Oxaliplatin-induced neurotoxicity was more pronounced but was not significantly different in patients with high adduct levels. The potential of oxaliplatin-DNA adduct measurements as pharmacodynamic end point should be further investigated in future trials

Liver Dysfunction and Phosphatidylinositol-3-Kinase Signalling in Early Sepsis: Experimental Studies in Rodent Models of Peritonitis

Background: Hepatic dysfunction and jaundice are traditionally viewed as late features of sepsis and portend poor outcomes. We hypothesized that changes in liver function occur early in the onset of sepsis, yet pass undetected by standard laboratory tests. Methods and Findings: In a long-term rat model of faecal peritonitis, biotransformation and hepatobiliary transport were impaired, depending on subsequent disease severity, as early as 6 h after peritoneal contamination. Phosphatidylinositol-3-kinase (PI3K) signalling was simultaneously induced at this time point. At 15 h there was hepatocellular accumulation of bilirubin, bile acids, and xenobiotics, with disturbed bile acid conjugation and drug metabolism. Cholestasis was preceded by disruption of the bile acid and organic anion transport machinery at the canalicular pole. Inhibitors of PI3K partially prevented cytokine-induced loss of villi in cultured HepG2 cells. Notably, mice lacking the PI3Kγ gene were protected against cholestasis and impaired bile acid conjugation. This was partially confirmed by an increase in plasma bile acids (e.g., chenodeoxycholic acid [CDCA] and taurodeoxycholic acid [TDCA]) observed in 48 patients on the day severe sepsis was diagnosed; unlike bilirubin (area under the receiver-operating curve: 0.59), these bile acids predicted 28-d mortality with high sensitivity and specificity (area under the receiver-operating curve: CDCA: 0.77; TDCA: 0.72; CDCA+TDCA: 0.87). Conclusions: Liver dysfunction is an early and commonplace event in the rat model of sepsis studied here; PI3K signalling seems to play a crucial role. All aspects of hepatic biotransformation are affected, with severity relating to subsequent prognosis. Detected changes significantly precede conventional markers and are reflected by early alterations in plasma bile acids. These observations carry important implications for the diagnosis of liver dysfunction and pharmacotherapy in the critically ill. Further clinical work is necessary to extend these concepts into clinical practice. Please see later in the article for the Editors' Summary

Improved treatment of MT-3 breast cancer and brain metastases in a mouse xenograft by LRP-targeted oxaliplatin liposomes

The anti-cancer drug oxaliplatin (OxP) has rarely been used to treat breast carcinoma, as it cannot cross the BBB to treat the frequently subsequent brain metastases. Here, we encapsulated OxP in liposomes prepared to reduce side effects and to simultaneously treat primary tumor and brain metastasis. The angiopep LRP-receptor ligand was bound to the vesicular surface for targeting. Targeted and non-targeted OxP liposomes were tested in vitro (binding, uptake, and transcytosis) and in vivo. Liposomes contained 0.65 mg OxP/mL, their mean diameter was 165 nm, and they released 50% of OxP within 8 days at 4 °lC and within 22 h at 36 °C. MDCK cells were used for uptake and transcytosis quantification. Compared to non-targeted liposomes, targeted liposomes showed 12-fold greater uptake, and 2.25-fold higher transcytosis. In vivo efficacy was tested using human MT-3 breast cancer cells transplanted subcutaneously and intracerebrally into female nude mice, and tumor growth inhibition was measured. OxP was injected (6 mg OxP/kg) four times. The best results were obtained with targeted liposomes (T/C: 21% for subcutaneous and 50% for intracerebral). OxP liposomes with a fluid membrane all inhibited MT-3 tumors significantly better than free OxP, with no significant difference between targeted and non-targeted liposomes. The therapeutic effect was accompanied with strong leukopenia and mild thrombocytopenia with all formulations. The newly developed OxP liposomes significantly improved the treatment of subcutaneously and intracerebrally growing breast cancer, but the targeted angiopep-equipped liposomes showed no superior effect in vivo