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ABSTRACT: Bcl-2 is an essential regulator of programmed cell death (PCD). Overexpression of Bcl-2 is common in pancreatic cancer; the high levels have been shown to correlate with resistance to PCD. This resistance is mediated by binding of Bcl-2 via its BH-3 domain to diverse proteins, including the Bax/Bak family members, various protein kinases, and beclin 1, which are involved in regulation of autophagy (type II PCD). Small molecule inhibitors of BH-3-mediated binding of Bcl-2 have been recently developed, although no investigation has been conducted in pancreatic cancer, a malignancy characterized by extreme resistance to PCD.
The effect of the Bcl-2 binding inhibitor A-779024 on PCD was assessed by fluorescence activated cell sorting; the effect on Bcl-2 and other PCD-related proteins was analyzed by immunoblotting. Induction of autophagy was determined by fluorescence microscopy using a stably transfected GFP-LC3 construct to visualize autophagosome formation. Co-localization of Bcl-2 with binding partners regulating PCD was examined by immunoprecipitation and confocal immunofluorescent microscopy.
A-779024 induced PCD in a dose- and time-dependent fashion. No change was seen in the protein levels of Bcl-2, Bax, Bcl-XL, or Mcl-1. Contrary to prediction, A-779024 was ineffective at inducing autophagy in these cells. Co-localization studies demonstrated that Bcl-2 was not bound to beclin 1 and, therefore, treatment with A-779024 could not induce release of beclin 1 and initiation of autophagy.
Disruption of Bcl-2 activity using the small molecule inhibitor A-779024 induces apoptotic but not autophagic PCD. This approach may be a novel therapy, either alone or in combination with other treatments such as chemotherapy or autophagy modulating agents in pancreatic cancer.
Journal of Surgical Research 03/2010; 163(2):276-81. · 2.25 Impact Factor
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ABSTRACT: Liver dysfunction is a prominent entity in Western medicine that has historically affected patients suffering from chronic viral or alcoholic hepatitis. The incidence of these conditions has not changed dramatically in recent years but the overall number of patients with liver dysfunction has increased considerably with the emergence of the obesity epidemic. Nonalcoholic fatty liver disease (NAFLD) has become increasingly recognized as the most common cause of chronic liver disease in the United States. Although the rate of progression of NAFLD to overt cirrhosis is low, the high prevalence of this condition, combined with the moderate degree of liver dysfunction it engenders, has resulted in a significant increase in the number of patients with liver disease that can be encountered by a surgical practice. Any degree of clinically evident liver disease in a prospective surgical patient should raise concern for the entire surgical team. This particularly applies to intraabdominal surgery whereby the presence of hepatomegaly, portal hypertension, variceal bleeding, and ascites can turn even the most routine operation into a morbid and life-threatening procedure. Nonabdominal surgery avoids some of the technical challenges presented by liver disease but the anesthetic management of a cirrhotic patient still makes any operation potentially more dangerous. In this article, approaches to minimize the risk when surgery becomes necessary in the presence of liver disease are discussed.
Anesthesiology Clinics 12/2009; 27(4):721-37.
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ABSTRACT: The understanding of the barriers to effective treatment of cancer is rapidly expanding. As the molecular path-ways of apoptosis become better understood, the mechanisms by which cancer cells evade the apoptotic effect of standard chemotherapeutic agents are revealed. Protein kinase B/AKT mediates a potent survival/anti-apoptotic signal when acti-vated; many cancers have been observed to harbor constitutive activation. The mechanism of constitutive activation of AKT in cancer is not usually due to mutation or amplification of the gene, but through activation of upstream signaling events. Extensive preliminary data has shown that inhibition of AKT restores apoptotic sensitivity in various cancers to diverse chemotherapeutic agents, yet the optimal mechanism of inhibition of AKT has yet to be clearly defined. Pancre-atic cancer is one of the most difficult to treat given its extreme resistance to the cytotoxic effect of traditional therapy; in-vestigations into therapies to restore apoptotic sensitivity have identified AKT as a potenial target for inhibition. The evolving targeted inhibition of AKT, whether directly or indirectly, is an active area of research with tremendous potential in cancer therapy, and pancreatic cancer specifically, and this field of research is discussed in the current review.
Current Cancer Therapy Reviews 01/2009; 5:288-295.
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ABSTRACT: Human alpha-chymase is an efficient angiotensin (AT) converting enzyme, selectively hydrolyzing AT I at Phe8 to generate bioactive AT II, which can promote cardiac hypertrophy, vascular stenosis, and hypertension. Some related enzymes, such as rat beta-chymase 1, are much less selective, destroying AT by cleaving at Tyr4. Comparisons of chymase structure and activity led to speculation that interaction between AT and the side chain of Lys40 or Arg143 accounts for the human enzyme's marked preference for Phe8 over Tyr4. To test these hypotheses, we compared AT hydrolysis by wild-type chymase with that by mutants changing Lys40 or Arg143 to neutral residues. Lys40 was exchanged for alanine, the residue found in canine alpha- and rat beta-chymase 1, the latter being dramatically less selective for hydrolysis at Phe8. Arg143 was exchanged for glutamine found in rat beta-chymase 1. The Lys40Ala mutant is a dog-like enzyme retaining strong preference for Phe8 but with Tyr4 hydrolytic rates enhanced 16-fold compared to wild-type human enzyme. Thus, of 40 residues mismatched between dog and human enzymes, a single residue accounts for most of the difference in specificity between them. The Arg143Gln mutant, contrary to prediction, remains highly Phe8-selective. Therefore, Lys40, but not Arg143, contributes to human chymase's remarkable preference for AT II generation over destruction.
Biochimica et Biophysica Acta 05/2002; 1596(2):346-56. · 4.66 Impact Factor
