Perturbed zinc homeostasis in rural 3-5-y-old Malawian children is associated with abnormalities in intestinal permeability attributed to tropical enteropathy.

Tropical enteropathy and zinc deficiency are major public health problems worldwide. Tropical enteropathy is characterized by reduced mannitol absorption with normal or increased lactulose absorption when a dual sugar absorption test is administered, the results of which are reported as the lactulose:mannitol ratio (L:M). Zinc homeostasis is quantified with a dual stable isotope test. This study tested the hypothesis that endogenous fecal zinc (EFZ) was correlated with the L:M. A dual sugar absorption test and dual stable isotope test were performed on 25 asymptomatic Malawian children aged 3-5 y at risk for tropical enteropathy and zinc deficiency. EFZ and net zinc retention were estimated and correlated with the L:M. Twenty-two children (88%) had an abnormal L:M (L:M>0.10), and the L:M was 0.24+/-0.10 (mean+/-SD). EFZ was 1.68+/-1.06 mg/d, a quantity greater than is seen in healthy populations from the developed world. EFZ was positively correlated with the L:M (r=0.62, p<0.001). Net zinc retention (0.67+/-1.6 mg/d) was negatively correlated with the L:M (r=-0.47, p=0.02). This suggests that perturbed zinc homeostasis is associated with subclinical enteropathy in these children.

Bortezomib pre-treatment prolongs interferon-alpha-induced STAT1 phosphorylation in melanoma cells.

Bortezomib is a proteasome inhibitor that can synergize with interferon-alpha (IFN-alpha) to induce apoptosis in melanoma cells in vitro and inhibit tumor growth in vivo. We hypothesized that proteasome inhibition may be an effective means to sensitize melanoma cells to the direct effects of IFN-alpha. Pre-treatment of human melanoma cells with bortezomib led to significantly increased transcription of interferon-stimulated genes as determined by real-time PCR. Flow cytometric and immunoblot analyses indicated that the enhanced direct actions of IFN-alpha on melanoma cells were the result of prolonged phosphorylation of STAT1 (P-STAT1) on both the Tyrosine(701) and Serine(727) residues. In contrast, the enhanced IFN-alpha-induced P-STAT1 was not observed in peripheral blood mononuclear cells that were pre-treated with bortezomib. These data suggest that proteasome inhibition represents a mechanism to enhance the direct effects of IFN-alpha on melanoma cells thereby complementing its immunostimulatory properties.

IFN-alpha and bortezomib overcome Bcl-2 and Mcl-1 overexpression in melanoma cells by stimulating the extrinsic pathway of apoptosis.

We hypothesized that IFN-alpha would enhance the apoptotic activity of bortezomib on melanoma cells. Combined treatment with bortezomib and IFN-alpha induced synergistic apoptosis in melanoma and other solid tumor cell lines. Apoptosis was associated with processing of procaspase-3, procaspase-7, procaspase-8, and procaspase-9 and with cleavage of Bid and poly(ADP-ribose) polymerase. Bortezomib plus IFN-alpha was effective at inducing apoptosis in melanoma cells that overexpressed Bcl-2 or Mcl-1, suggesting that this treatment combination can overcome mitochondrial pathways of cell survival and resistance to apoptosis. The proapoptotic effects of this treatment combination were abrogated by a caspase-8 inhibitor, led to increased association of Fas and FADD before the onset of cell death, and were significantly reduced in cells transfected with a dominant-negative FADD construct or small interfering RNA targeting Fas. These data suggest that bortezomib and IFN-alpha act through the extrinsic pathway of apoptosis via FADD-induced caspase-8 activation to initiate cell death. Finally, bortezomib and IFN-alpha displayed statistically significant antitumor activity compared with either agent alone in both the B16 murine model of melanoma and in athymic mice bearing human A375 xenografts. These data support the future clinical development of bortezomib and IFN-alpha for malignant melanoma.