Previously, we showed that the peroxisome proliferatoractivated receptor ; (PPAR;) agonist troglitazone at high doses was able to suppress androgen receptor (AR) expression in LNCaP prostate cancer cells independently of PPAR;. Pharmacologic exploitation of this finding led to STG28, a PPAR;-inactive analogue of troglitazone with substantially higher potency in AR repression. Considering the pivotal role of AR in prostate tumorigenesis, this study investigates the mechanism by which troglitazone and derivatives suppress AR expression in LNCaP cells. Reverse transcription-PCR and reporter gene assays indicate that this drug-induced AR repression occurs at both mRNA and protein levels. Evidence suggests that troglitazone and derivatives mediate the transcriptional repression of AR by facilitating the ubiquitindependent proteasomal degradation of the transcriptional factor Sp1. These agents also cause the proteolysis of two proteins that regulate Sp1-mediated transcription (i.e., the TATA-binding protein-associated factor TAF II 250 and cyclin D1). However, their involvement in the transcriptional repression of AR is refuted by the finding that small interfering RNA knockdown of these two regulatory proteins does not cause AR down-regulation. STG28 does not cause significant reduction in Sp1 or AR expression in normal prostate epithelial cells. This discriminatory effect underscores the differential susceptibility of malignant versus normal cells to the inhibitory effect of STG28 on cell viability. From a translational perspective, STG28 provides a proof of principle that potent AR-ablative agents could be developed through structural modifications of troglitazone. Moreover, as the control of Sp1 degradation remains unclear, STG28 represents a unique pharmacologic probe to investigate the ubiquitin-proteasome system that regulates Sp1 proteolysis.

ZBRK1, named after its structure of Zinc finger and BRCA1-interacting protein with KRAB domain-1 (ZBRK1), is a transcriptional repressor modulated by BRCA1. Recent evidence also indicated that ZBRK1 collaborated with BRCA1/CtIP to repress angiopoietin-1 expression in preventing over enlargement of blood vessels in tumors, suggesting that ZBRK1 may exert a critical role during tumor progression. However, a direct role of ZBRK1 in tumorigenesis and tumor progression remains obscure. Here we found that ZBRK1 expression was significantly lower in highly malignant cervical cancer cells than the counterpart normal tissue. Ectopic expression of ZBRK1 in HeLa cells significantly inhibits its neoplastic phenotypes including cell proliferation, soft-agar colony formation and tumor growth in nude mice. To explore its mechanisms, analyses of gene expression patterns of these cells revealed groups of genes not only critical for cell proliferation but also for cell motility being down regulated. Consistently, ectopic expression of ZBRK1 inhibits HeLa cells migration in cell migration and invasion assays in culture and metastatic assay in mice. Importantly, ZBRK1 directly represses transcription of the metastatic gene, MMP9, and the loss of ZBRK1 expression is inversely correlated to the elevated expression of MMP9 in cervical cancer specimens. Taken together, these results indicate that ZBRK1 may have a critical role as a tumor suppressor, especially in metastasis, through directly modulating metastatic genes such as MMP9.

ZBRK1, a zinc finger protein that interacts with breast cancer 1 (BRCA1) and KRAB-ZFP-associated protein 1 (KAP1), has been suggested to serve as a tumor suppressor via repression of tumor metastasis/invasion. To date, the detailed molecular mechanisms for how BRCA1 and KAP1 participate in ZBRK1-mediated transcriptional repression, metastasis and invasion as well as the associated clinical relevance remain unclear. In this study, we demonstrated that both the N- and C-terminal domains of ZBRK1 are important for inhibiting cell proliferation and anchorage-independent growth in cervical cancer. Specifically, the N-terminal KRAB domain of ZBRK1 displayed a more crucial role in inhibiting metastasis and invasion through modulation of KAP1 function in a transcriptionally dependent manner. The loss of ZBRK1 results in an increase of KAP1 expression, which enhanced migration and invasion of cervical cancer cells both the in vitro and in vivo. Moreover, an inverse correlation of expression levels was observed between ZBRK1 and KAP1 following tumor progression from in situ carcinoma to invasive/metastatic cervical cancer specimens. Taken together, the current results indicate that a loss of ZBRK1 contributes to the increased expression of KAP1, potentiating its role to enhance metastasis and invasion.

Considering the role of aberrant ␤-catenin signaling in tumorigenesis, we investigated the mechanism by which the peroxisome proliferator-activated receptor ␥ (PPAR␥) agonist troglitazone facilitated ␤-catenin down-regulation. We demonstrate that troglitazone and its more potent PPAR␥-inactive analogs ⌬2TG and STG28 mediated the proteasomal degradation of ␤-catenin in prostate cancer cells by up-regulating the expression of ␤-transducin repeat-containing protein (␤-TrCP), an F-box component of the Skp1-Cul1-F-box protein E3 ubiquitin ligase. Evidence indicates that although small interfering RNA-mediated ␤-TrCP knockdown protected cells against STG28-facilitated ␤-catenin ablation, ectopic ␤-TrCP expression enhanced the degradation. The involvement of ␤-TrCP in ␤-catenin degradation was also corroborated by the pull-down analysis and the concurrent down-regulation of known ␤-TrCP substrates examined, including Wee1, I␤␣, cdc25A, and nuclear factor-B/p105. Furthermore, glycogen synthase kinase-3␤ represented a key regulator in the effect of these thiazolidinedione derivatives on ␤-catenin proteolysis even though these agents increased its phosphorylation level. It is noteworthy that this drug-induced ␤-TrCP up-regulation was accompanied by the concomitant down-regulation of Skp2 and Fbw7, thereby affecting many of the target proteins of these two F-box proteins (such as p27 and cyclin E). As a consequence, the ability of troglitazone to target these F-box proteins provides a molecular basis to account for its reported effect on modulating the expression of aforementioned cell-cycle regulatory proteins. Despite this complicated mode of pharmacological actions, normal prostate epithelial cells, relative to LNCaP cells, were less susceptible to the effects of STG28 on modulating the expression of ␤-catenin and ␤-TrCP, suggesting the translation potential of using STG28 as a scaffold to develop more potent chemopreventive agents.Substituted thiazolidinediones such as troglitazone, ciglitazone, and rosiglitazone belong to a family of oral antidiabetic drugs that increase insulin sensitivity in adipose tissue, muscle, and liver primarily through the activation of peroxisome proliferator-activated receptor ␥ (PPAR␥) (Day, 1999). It is well-documented that ligand activation of PPAR␥ can regulate multiple crucial biological processes including growth, differentiation, and apoptosis through the transcriptional expression of insulin-sensitive genes involved in glucose metabolism and energy balance. It is noteworthy that these agents at high doses exhibit in vitro and in vivo antitumor effects against many types of cancers, including colon, breast, and prostate (Koeffler, 2003;Weng et al., 2006). However, recent evidence indicates that the effect of thiazo-

A series of bis(hydroxymethyl)indolizino[6,7-b]indoles and their bis(alkylcarbamates) were synthesized for antitumor studies. These agents were designed as hybrid molecules of β-carboline (topoisomerase inhibition moiety) and bis(hydroxymethyl)pyrrole (DNA cross-linking moiety). The preliminary antitumor studies indicated that these agents exhibited significant cytotoxicity against a variety of human tumor cells in vitro. Treatment of human breast carcinoma MX-1 xenograft-bearing nude mice with compounds 18b and 28c achieved more than 99% tumor remission. We also observed that 18a displayed potent therapeutic efficacy against human lung adenocarcinoma A549 and colon cancer HT-29 xenografts. These results revealed that compound 18a was more potent than irinotecan against HT-29 cells and was as potent as irinotecan against A549 cells in xenograft models. Furthermore, we demonstrated that these derivatives possess multiple modes of action, such as induction of DNA cross-linking, inhibition of topoisomerase I and II, and cell-cycle arrest at the S-phase.

Granulysin, a cationic protein expressed by human natural killer cells and cytotoxic T lymphocytes, is a mediator for drug-induced Stevens-Johnson syndrome and graft-versus-host disease. Some 15 kDa granulysin are processed into 9 kDa forms and sequestered in cytolytic granules, while others are constitutively secreted into body fluids. Both 9 and 15 kDa granulysin have been shown to be a serum marker for cell-mediated immunity. Furthermore, 15 kDa is able to activate monocyte differentiation. However, its antimicrobial properties have not been clearly addressed. Here, we report a novel method to prepare both the soluble 9 and 15 kDa granulysin and show that the 15 kDa form is more effective than the 9 kDa form in exerting specific antimicrobial activity against Pseudomonas aeruginosa within a range of few micromolars. We also show that the 15 kDa granulysin is able to hyperpolarize the membrane potential and increase membrane permeability of treated bacteria. Interestingly, the bactericidal activity and membrane permeability of the granulysins were markedly reduced at lower pH (pH 5.4) as a result of probable increase in hydrophobicity of the granulysins. Additionally, we’ve also shown the granulysin to inhibit biofilm formation by P. aeruginosa. These results suggest that the 15 kDa granulysin exhibits a novel mechanism in bacteria killing in a way that’s different from most antimicrobial peptides. Our novel granulysin preparation methodology will be useful for further study of action mechanisms of other antimicrobial, cytotoxic and immunomodulating properties in granulysin-mediated diseases.

This work shows that loss of RUNX3 expression is highly associated with lymph node metastasis and poor prognosis of gastric cancer. The re-expression of RUNX3 may induce apoptosis and inhibit the growth as well as invasion/migration of cancer cells. These results indicate that the targeting of the RUNX3 pathway could represent a potential modality for treating gastric cancer.

Galectine-4 (gal-4), encoded by the LGALS4 gene, was recently shown to exhibit a tumor suppressive effect in colorectal carcinoma and pancreatic adenocarcinoma, although how the expression of this gene is regulated remains unknown. No reports describe the significance of gal-4 in the malignant potential of urothelial tumors. Thus, we analyzed LGALS4 methylation and gene expression and their clinical relevance and biological function in urothelial carcinoma (UC).LGALS4 methylation was initially identified as a progression biomarker for UC patients through genomewide DNA methylation profiling of 16 tumor samples. Bisulfite sequencing PCR and immunohistochemistry were performed to validate the promoter methylation and expression of LGALS4. We used quantitative methylation-specific PCR to determine the methylation levels of LGALS4 normalized to ACTB in the tumor samples of 79 UC patients and compared the levels between patients with different clinicopathological characteristics. The association with survival probability was analyzed with the Kaplan-Meier method and Cox regression analysis. The ectopic expression of gal-4 in cancer cell lines was used to address its biological function in UC in vitro. The promoter hypermethylation of LGALS4 (>2.51, log 10 scale) revealed a positive correlation with high levels of both histological grade and tumor T category and with lymph node metastasis (all P≤0.001). In addition, LGALS4 hypermethylation was an independent predictor of inferior survival in UC patients (P<0.05). The ectopic expression studies demonstrated that gal-4 suppressed urothelial cancer cell growth, migration, and invasion. Thus, LGALS4 may function as a tumor suppressor gene in UC progression. Our findings provide evidence that methylation-mediated LGALS4 gene repression may be involved in urothelial tumor progression.