Gemcitabine/cannabinoid combination triggers autophagy in pancreatic cancer cells through a ROS-mediated mechanism

Gemcitabine (GEM, 2′,2′-difluorodeoxycytidine) is currently used in advanced pancreatic adenocarcinoma, with a response rate of < 20%. The purpose of our work was to improve GEM activity by addition of cannabinoids. Here, we show that GEM induces both cannabinoid receptor-1 (CB1) and cannabinoid receptor-2 (CB2) receptors by an NF-κB-dependent mechanism and that its association with cannabinoids synergistically inhibits pancreatic adenocarcinoma cell growth and increases reactive oxygen species (ROS) induced by single treatments. The antiproliferative synergism is prevented by the radical scavenger N-acetyl--cysteine and by the specific NF-κB inhibitor BAY 11-7085, demonstrating that the induction of ROS by GEM/cannabinoids and of NF-κB by GEM is required for this effect. In addition, we report that neither apoptotic nor cytostatic mechanisms are responsible for the synergistic cell growth inhibition, which is strictly associated with the enhancement of endoplasmic reticulum stress and autophagic cell death. Noteworthy, the antiproliferative synergism is stronger in GEM-resistant pancreatic cancer cell lines compared with GEM-sensitive pancreatic cancer cell lines. The combined treatment strongly inhibits growth of human pancreatic tumor cells xenografted in nude mice without apparent toxic effects. These findings support a key role of the ROS-dependent activation of an autophagic program in the synergistic growth inhibition induced by GEM/cannabinoid combination in human pancreatic cancer cells.

Intracellular zinc increase inhibits p53(-/-) pancreatic adenocarcinoma cell growth by ROS/AIF-mediated apoptosis

We show that treatment with non-toxic doses of zinc in association to the ionophore compound pyrrolidine dithiocarbamate (PDTC) inhibits p53(-/-) pancreatic cancer cell growth much more efficiently than gemcitabine, the gold standard chemotherapeutic agent for pancreatic cancer. Both the metal chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine and the radical scavenger N-acetyl-l-cysteine are able to recover cell growth inhibition by Zn/PDTC, demonstrating that this effect depends on the increased levels of intracellular zinc and of reactive oxygen species (ROS). Zn/PDTC treatment induces a strong apoptotic cell death that is associated to ROS-dependent nuclear translocation of the mitochondrial factor AIF, but not to the regulation of apoptotic genes and caspase activation. Primary fibroblasts are more resistant than pancreatic cancer cells to Zn/PDTC treatment and exhibit a lower basal and Zn/PDTC-induced enhancement of intracellular zinc. We show that Zn/PDTC induces p53 proteasomal degradation and that the proteasome inhibitor MG132 further increases fibroblast growth inhibition by Zn/PDTC, suggesting that p53 degradation plays an important role in fibroblast resistance to Zn/PDTC.

Zinc depletion efficiently inhibits pancreatic cancer cell growth by increasing the ratio of antiproliferative/proliferative genes

We investigated the ability of the zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) to reduce pancreatic cancer cell viability. TPEN was much more efficient to inhibit pancreatic adenocarcinoma cell growth than a panel of anti-cancer drugs, including 5-fluorouracil, irinotecan, cisplatin, edelfosine, trichostatin A, mitomycin C, and gemcitabine, the gold standard chemotherapeutic agent for pancreatic cancer. Moreover, TPEN showed a dose- and time-dependent anti-proliferative effect significantly higher on pancreatic cancer cells than on normal primary fibroblasts. This effect may be explained by a significantly higher zinc depletion by TPEN in pancreatic cancer cells as compared to fibroblasts. Cell viability reduction by TPEN was associated to both G1-phase cell cycle arrest and apoptosis, and to the increased ratio of the expression level of cyclin-Cdk inhibitor versus cyclin genes and apoptotic versus anti-apoptotic genes. Finally, we show that apoptotic cell death induced by TPEN involved mitochondrial injury and caspase 3 and caspase 8 activation. In this study, we suggest that zinc depletion may be an efficient strategy in the treatment of pancreatic cancer because of its reduced antiproliferative effect on normal cells.

Investigation of a Q-fever outbreak in northern Italy

OBJECTIVES

A study was conducted to evaluate the extent of a Q-fever epidemic through active case finding in the area of Vicenza (north-eastern Italy), and to identify risk factors for Q-fever in this outbreak.

METHODS

1) Descriptive epidemiology; 2) Seroepidemiological survey; 3) Case-control study. 1) Epidemic curve and maps with the location of cases. Identification of the road followed by the flocks of sheep. 2) Cross-sectional study on humans and flocks of sheep tested for anti-Coxiella burnetii antibodies. 3) Cases were defined by the presence of fever > 38 degrees C plus serological confirmation. Controls were 94 apparently healthy individuals attending outpatient facilities for control visits or certification, group-matched by geographical area, age and gender. A standardized questionnaire was administered by trained interviewers. Odds ratio and 95% confidence intervals (CI) were used to evaluate risk factors for Q-fever.

RESULTS

A total 58 cases were identified in a 5-month period. Male to female ratio was 2.8:1; mean age was 42 years (range: 20-65 years). Twenty-eight patients (48%) were hospitalized. Fever was accompanied by asthenia (81%), headache (76%), chills (72%), and myalgia and arthralgia (53%); cough was present in 47% of patients. Rx abnormalities were found in 81% of the patients undergoing chest X-ray. Among 111 apparently healthy family members who underwent serological testing, four (3.6%) had antibodies to Coxiella burnetii. Three flocks which passed through the outbreak area between late May and early June were shown to be infected, with prevalence of antibodies ranging between 45 and 53%. The case-control study showed a significant association with exposure to flocks of sheep (Odds ratio = 6.1; 95% CI 2.5, 16.3). Other potential risk factors were not more commonly reported by cases with respect to controls.

CONCLUSIONS

Indirect exposure to flocks of sheep was a determinant of this outbreak of Q-fever. This finding suggests that transmission occurred through inhalation of contaminated airborne particles. The importance of control measures should be stressed in areas traversed by flocks of sheep.