Xuejian Zhao

Down-regulation of signal transducer and activator of transcription 3 expression using vector-based small interfering RNAs suppresses growth of human prostate tumor in vivo.

Purpose: Signal transducer and activator of transcription 3 (Stat3) is constitutively activated in a variety of cancers and it is a common feature of prostate cancer. Thus, Stat3 represents a promising molecular target for tumor therapy. We applied a DNA vector–based Stat3-specific RNA interference approach to block Stat3 signaling and to evaluate the biological consequences of Stat3 down-modulation on tumor growth using a mouse model. Experimental Design: To investigate the therapeutic potential of blocking Stat3 in cancer cells, three small interfering RNAs (siRNA; Stat3-1, Stat3-2, and Stat3-3) specific for different target sites on Stat3 mRNA were designed and used with a DNA vector–based RNA interference approach expressing short hairpin RNAs to knockdown Stat3 expression in human prostate cancer cells in vitro as well as in vivo. Results: Of the three equivalently expressed siRNAs, only Stat3-3 and Stat3-2, which target the region coding for the SH2 domain and the coiled-coil domain, respectively, strongly suppressed the expression of Stat3 in PC3 and LNCaP cells. The Stat3-1 siRNA, which targeted the DNA-binding domain, exerted no effect on Stat3 expression, indicating that the gene silencing efficiency of siRNA may be dependent on the local structure of Stat3 mRNA. The Stat3 siRNAs down-regulated the expression of Bcl-2 (an antiapoptotic protein), and cyclin D1 and c-Myc (cell growth activators) in prostate cancer cells. Inhibition of Stat3 and its related genes was accompanied by growth suppression and induction of apoptosis in cancer cells in vitro and in tumors implanted in nude mice. Conclusions: These data indicate that Stat3 signaling is a promising molecular target for prostate cancer therapy and that vector-based Stat3 siRNA may be useful as a therapeutic agent for treatment of prostate cancer.

Intratumoral Delivery and Suppression of Prostate Tumor Growth by Attenuated Salmonella enterica serovar typhimurium Carrying Plasmid-Based Small Interfering RNAs

The facultative anaerobic, invasive Salmonella enterica serovar typhimurium (S. typhimurium) has been shown to retard the growth of established tumors. We wondered if a more effective antitumor response could be achieved in vivo if these bacteria were used as tools for delivering specific molecular antitumor therapeutics. Constitutively activated transcription factor signal transducer and activator of transcription 3 (STAT3) promotes the survival of a number of human tumors. In this study, we investigated the relative efficacies of attenuated S. typhimurium alone or combined with Stat3-specific small interfering RNA (siRNA) in terms of tumor growth and metastasis. The bacteria preferentially homed into tumors over normal liver and spleen tissues in vivo. S. typhimurium expressing plasmid-based Stat3-specific siRNAs significantly inhibited tumor growth, reduced the number of metastastic organs, and extended the life time for C57BL6 mice bearing an implanted prostate tumor, versus bacterial treatment alone. These results suggest that attenuated S. typhimurium combined with an RNA interference approach might be more effective for the treatment of primary as well as metastatic cancer.

A proteomic analysis reveals the loss of expression of the cell death regulatory gene GRIM-19 in human renal cell carcinomas.

Gene associated with retinoid interferon-induced mortality (GRIM)-19, an inhibitor of transcription factor STAT3, was originally identified as a critical regulatory protein in a genetic screen that was designed to identify the gene products necessary for Interferon (IFN)-β- and retinoic acid-induced cell death. Over expression of GRIM-19 activates cell death. Conversely, inactivation of its expression promotes cell growth. STAT3 is a transcription factor that regulates gene expression in response to multiple extra cellular growth factors. In contrast to its normal feedback inhibition, a constitutive activation of STAT3 has been documented in several tumors. Although many STAT3-inhibitors are described, their relevance to human cancer is unclear. In an attempt to define the molecular alterations associated with human renal cell carcinoma (RCC) using mass spectrometry, we have discovered that expression of GRIM-19 is lost or severely depressed in a number of primary RCC and in some urinogenital tumors. Using an RCC cell line, we show that down regulation of GRIM-19 promotes tumor growth via an augmentation of STAT3-dependent gene expression. These studies for the first time show a tumor-suppressor like activity of GRIM-19.

Effects of Plasmid-Based Stat3-Specific Short Hairpin RNA and GRIM-19 on PC-3M Tumor Cell Growth

Purpose: Persistent activation of signal transducers and activators of transcription 3 (Stat3) and its overexpression contribute to the progression and metastasis of several different tumor types. For this reason, Stat3 is a reasonable target for RNA interference–mediated growth inhibition. Blockade of Stat3 using specific short hairpin RNAs (shRNA) can significantly reduce prostate tumor growth in mice. However, RNA interference does not fully ablate target gene expression in vivo, owing to the idiosyncrasies associated with shRNAs and their targets. To enhance the therapeutic efficacy of Stat3-specific shRNA, we applied a combination treatment involving gene associated with retinoid-IFN–induced mortality 19 (GRIM-19), another inhibitor of STAT3, along with shRNA. Experimental Design: The coding sequences for GRIM-19, a cellular STAT3-specific inhibitor, and Stat3-specific shRNAs were used to create a dual expression plasmid vector and used for prostate cancer therapy in vitro and in mouse xenograft models in vivo. Results: The coexpressed Stat3-specific shRNA and GRIM-19 synergistically and more effectively suppressed prostate tumor growth and metastases when compared with treatment with either single agent alone. Conclusion: The simultaneous use of two specific, but mechanistically different, inhibitors of STAT3 activity exerts enhanced antitumor effects.

β-Catenin/TCF pathway upregulates STAT3 expression in human esophageal squamous cell carcinoma

Precise roles of beta-catenin/TCF pathway involved in esophageal tumorigenesis remain elusive. Here we found STAT3 overexpression in esophageal cancer cells and tissues, and its overexpression in esophageal squamous cell carcinoma (ESCC) tissues correlated with beta-catenin cytoplasmic/nuclear accumulation. A functional TCF binding element was detected in STAT3 promoter which specifically bound to TCF4. Transfected beta-catenin induced STAT3 transcriptional activity dose-dependently, and also enhanced STAT3 mRNA and protein levels. These inductions were specifically abolished by dominant-negative TCF4. These results suggest that STAT3 is a target of beta-catenin/TCF pathway and might participate in esophageal tumorigenesis.

Prostate cancer： an emerging threat to the health of aging men in Asia

The aim of this study was to determine and examine the possible reasons for the difference in prostate cancer incidence between Asian men and North American men by literature review. Data regarding cancer incidence and mortality were obtained from the database of the International Agency for Research on Cancer (IARC). A literature review was conducted by studying related articles published in peer-reviewed journals such as the The New England Journal of Medicine, Journal of Clinical Oncology, A Cancer Journal for Clinicians and Asian Journal of Andrology. To evaluate the early diagnosis and survival rates, the mortality-to-incidence rate ratio (MR/IR) was calculated from the IARC data. By comparing prostate cancer data between Asian men and North American men, we found that differences in the incidence rate and MR/IR could be attributed largely to a lack of annual prostate cancer screening with serum prostate-specific antigen (PSA) in most Asian countries. It is likely that PSA screening also contributes significantly to the differences in prostate cancer mortality rates. Prostate cancer has the highest incidence rate among five common malignancies in Asian Americans. However, the MR/IR ratio of prostate cancer is the lowest among cancers. These data seem to further support the usefulness of PSA screening, even though the percentage of low risk cancers is greater in prostate cancer than in other cancers. The low incidence rate of prostate cancer does not reflect the actual statistics of this disease in Asia. The data from limited institutions in many Asian countries seem to bias the true incidence and mortality rates. To improve this situation, incorporating PSA screening for prostate cancer, as well as constructing a nationwide cancer registration system, will be helpful.

Functional graphene oxide as a plasmid-based Stat3 siRNA carrier inhibits mouse malignant melanoma growth in vivo

Graphene oxide (GO) has attracted intensive interest in the biomedical field in recent years. We investigate whether the use of functional graphene oxide as an efficient delivery system for delivering specific molecular antitumor therapeutics in vivo could achieve a more excellent antitumor effect. Constitutive activation of signal transducer and activator of transcription 3 (Stat3) promotes survival in a wide spectrum of human cancers. In this paper, we study the in vivo behavior of graphene oxide chemically functionalized with polyethylenimine and polyethylene glycol (GO-PEI-PEG) as a plasmid-based Stat3-specific small interfering RNA (siRNA) carrier in mouse malignant melanoma. The in vivo results indicate significant regression in tumor growth and tumor weight after plasmid-based Stat3 siRNA delivered by GO-PEI-PEG treatment. Moreover, there was no significant side effect from GO-PEI-PEG treatment according to histological examination and blood chemistry analysis in mice. Thus, our work is the first success of using GO-PEI-PEG as a promising carrier for plasmid Stat3 siRNA delivery and down-regulation of Stat3 by a polymer-mediated vehicle and suggests the great promise of graphene in biomedical applications such as cancer treatment.

Knockdown of Stat3 expression using RNAi inhibits growth of laryngeal tumors in vivo

AbstractAim:To study the effect of pSilencer 1.0-U6-siRNA-stat3 on the growth of human laryngeal tumors in nude mice.Methods:Hep2 cells were transplanted into nude mice, then at the time of tumor formation, growth rates were observed. After the tumor formed, pSilencer 1.0-U6-siRNA-stat3 was injected. Tumor volumes were calculated, and growth curves were plotted. Representative histological sections were taken from mice bearing transplantation tumors in both treated and control groups, and start3, pTyr-stat3, Bcl-2, cyclin D1, and survivin expression were detected by Western blotting. survivin mRNA levels were detected by Northern blotting, hematoxylin and eosin staining and terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labeling (TUNEL) assay to confirm the apoptosis of tumors.Results:In nude mice, pSilencer 1.0-U6-siRNA-stat3 significantly suppressed the growth of tumors compared with controls (P<0.01). In suppressed stat3 expression, and downregulated BcL2, cyclin D1, and survivin expression within the tumor. This significantly induced apoptosis of the tumors.Conclusion:pSilencer 1.0-U6-siRNA-stat3 was able to inhibit the growth of transplanted human laryngeal tumors in nude mice and induce apoptosis.

Role of thin descending limb urea transport in renal urea handling and the urine concentrating mechanism

Urea transporters UT-A2 and UT-B are expressed in epithelia of thin descending limb of Henles loop and in descending vasa recta, respectively. To study their role and possible interaction in the context of the urine concentration mechanism, a UT-A2 and UT-B double knockout (UT-A2/B knockout) mouse model was generated by targeted deletion of the UT-A2 promoter in embryonic stem cells with UT-B gene knockout. The UT-A2/B knockout mice lacked detectable UT-A2 and UT-B transcripts and proteins and showed normal survival and growth. Daily urine output was significantly higher in UT-A2/B knockout mice than that in wild-type mice and lower than that in UT-B knockout mice. Urine osmolality in UT-A2/B knockout mice was intermediate between that in UT-B knockout and wild-type mice. The changes in urine osmolality and flow rate, plasma and urine urea concentration, as well as non-urea solute concentration after an acute urea load or chronic changes in protein intake suggested that UT-A2 plays a role in the progressive accumulation of urea in the inner medulla. These results suggest that in wild-type mice UT-A2 facilitates urea absorption by urea efflux from the thin descending limb of short loops of Henle. Moreover, UT-A2 deletion in UT-B knockout mice partially remedies the urine concentrating defect caused by UT-B deletion, by reducing urea loss from the descending limbs to the peripheral circulation; instead, urea is returned to the inner medulla through the loops of Henle and the collecting ducts.

Diagnostic strategies and the incidence of prostate cancer: reasons for the low reported incidence of prostate cancer in China.

We have analysed the reasons for the low reported incidence of prostate cancer in China and argue for early diagnosis and treatment of this disease. According to the 2002 database of the International Agency for Research on Cancer (IARC), the age-standardized incidence of prostate cancer in China is 1.6/10(5) person years (PY), with a mortality rate of 1.0/10(5) PY and mortality-to-incidence rate ratio (MR/IR) = 0.63. The MR/IR ratio of prostate cancer in China was found to be higher than the average in Asia (MR/IR = 0.57) and much higher than that in North America (MR/IR = 0.13). These data indicate that in China most prostate cancers were in the advanced stages at the time of diagnosis, and that patients had a short survival time thereafter. In 2004, Stamey et al. reported a retrospective American study of prostate cancer for the years 1983-2003. It was shown that most cases of prostate cancer detected by prostate-specific antigen (PSA) screening were in the advanced stage at the start of this 20-year period. These early follow-up data are quite similar to the results obtained from mass PSA screening of elderly men in Changchun, China. However, after the American programmes for early diagnosis and treatment of prostate cancer were accepted, tumours were diagnosed at earlier stages. On the basis of these findings, mass screening should be performed in the whole of China using serum PSA to facilitate early diagnosis and treatment of prostate cancer.