No abstract

Recent studies have suggested that dysregulation of autophagy plays a pivotal role in tumorigenesis. Here, we determined the prognostic value of autophagy-related protein Beclin 1 in gastric cancer. A total of 153 primary gastric cancer patients were subjected to analysis of Beclin 1 expression and survival prognosis. Among them, 68 patients were assigned randomly and used as a training set to generate a cutoff score for Beclin 1 expression by receive operating characteristic (ROC) curve analysis. The ROC-generated cutoff score was subjected to analyze the association of Beclin 1 with clinical characteristics and patient outcome. In a testing set (n = 85) and overall patients (n = 153), both univariate and multivariate analysis found that low expression of Beclin 1 predicted adverse overall survival and progression-free survival for gastric cancer patients. Furthermore, in each stage of gastric cancer patients, Beclin 1 expression was a prognostic indicator in patients with stage II, III and IV. Importantly, a reverse relationship between Beclin 1 and Bcl-xL expression was demonstrated. In patients of elevated Bcl-xL expression, a subset with lower Beclin 1 expression displayed an inferior overall survival and progression-free survival than those with higher Beclin 1 expression. Thus, our data demonstrated that low expression of Beclin 1, associated with high Bcl-xL, played as an independent biomarker, contributing to a more aggressive cancer cell phenotype and poor prognosis for gastric tumor.

Cisplatin was shown to strongly inhibit the decatenation and relaxation activity of isolated human DNA topoisomerase II␣. This inhibition was not accompanied by stabilization of a covalent topoisomerase II␣-DNA intermediate. Pretreatment of kinetoplast plasmid DNA (kDNA) or pBR322 DNA with submicromolar concentrations of cisplatin quickly rendered these substrates incompetent in the topoisomerase II␣ catalytic assay. Cisplatin nearly equally inhibited growth of a parental K562 and an etoposide-resistant K/VP.5 cell line that contained decreased topoisomerase II␣ levels, a result consistent with isolated enzyme experiments demonstrating that cisplatin was not a topoisomerase II␣ poison. Because cisplatin is known to react with protein sulfhydryl groups, the 13 cysteine groups in the topoisomerase II␣ monomer were evaluated by mass spectrometry to determine which cysteines were free and disulfide-bonded to identify possible sites of cisplatin adduction. High-pressure liquid chromatographymatrix-assisted laser desorption ionization mass spectrometry showed that topoisomerase II␣ contained at least five free cysteines (170, 216, 300, 392, and 405) and two disulfide-bonded cysteine pairs (427-455 and 997-1008). Cysteine 733 was also disulfide-bonded, but its partner cysteine could not be identified. Cisplatin antagonized the formation of a fluorescence adduct between topoisomerase II␣ and the sulfhydryl-reactive maleimide reagent 10-(2,5-dihydro-2,5-dioxo-1H-pyrrol-1-yl)-9-methoxy-3-oxo-3H-naphtho[2,1-b]pyran-2-carboxylic acid methyl ester (ThioGlo-1). Dithiothreitol, which was shown by spectrophotometry to react rapidly with cisplatin (6-min half-time), diminished the capacity of cisplatin to interfere with ThioGlo-1 binding to topoisomerase II␣. The results of this study suggest that cisplatin may exert some of its cell growth inhibitory and antitumor activity by inhibition of topoisomerase II␣ through reaction with critical enzyme sulfhydryl groups and/or by forming DNA adducts that render the DNA substrate refractory to topoisomerase II␣.Cisplatin is widely used for the treatment of cancer and is thought to act by forming intrastrand and interstrand crosslinks with DNA (Waud, 1995;Reedijk, 1996). A variety of other biomolecules have also been shown to react with cisplatin because of its electrophilicity toward sulfhydryl, methionine, histidine, and other amino acids with nitrogencontaining side chains (Waud, 1995;Reedijk, 1996;Ivanov et al., 1998;Hagrman et al., 2003). In a study of the topoisomerase II inhibitory effects of a platinum(II) complex of the catalytic topoisomerase II inhibitor dexrazoxane, we showed that cisplatin strongly inhibited the decatenation activity of topoisomerase II (Hasinoff et al., 2004). Topoisomerase II alters DNA topology by catalyzing the passing of an intact DNA double helix through a transient double-stranded break made in a second helix and is critical for relieving torsional Article, publication date, and citation information can be found at http://molpharm.aspetjournal...

Triple negative breast cancer (TNBC) acquires an unfavorable prognosis, emerging as a major challenge for the treatment of breast cancer. In the present study, 122 TNBC patients were subjected to analysis of Aurora-A (Aur-A) expression and survival prognosis. We found that Aur-A high expression was positively associated with initial clinical stage (P = 0.025), the proliferation marker Ki-67 (P = 0.001), and the recurrence rate of TNBC patients (P<0.001). In TNBC patients with Aur-A high expression, the risk of distant recurrence peaked at the first 3 years and declined rapidly thereafter, whereas patients with Aur-A low expression showed a relatively constant risk of recurrence during the entire follow-up period. Univariate and multivariate analysis showed that overexpression of Aur-A predicted poor overall survival (P = 0.002) and progression-free survival (P = 0.012) in TNBC. Furthermore, overexpression of Aur-A, associated with high Ki-67, predicted an inferior prognosis compared with low expression of both Aur-A and Ki-67. Importantly, we further found that Aur-A was overexpressed in TNBC cells, and inhibition of this kinase inhibited cell proliferation and prevented cell migration in TNBC. Our findings demonstrated that Aur-A was a potential therapeutic target for TNBC and inhibition of Aur-A kinase was a promising regimen for TNBC cancer therapy.