Purpose: The RNA interference effect is an alternative to antisense DNA as an experimental method of downregulating a specific target protein. Although the RNA interference effect, which is mediated by small interfering RNA (siRNA) or micro-RNA, has potential application to human therapy, the hydrodynamic method usually used for rapid administration of oligonucleotides is unsuitable for use in humans. In this study, we have investigated the antitumor activity of a synthetic siRNA, B717, which is sequence specific for the human bcl-2 oncogene, complexed with a novel cationic liposome, LIC-101.Experimental Design: In a mouse model of liver metastasis, we administered B717/LIC-101 by bolus intravenous injection, adjusting the rate and volume of administration to what is feasible in human therapy. In a mouse model bearing prostate cancer in which the cells were inoculated under the skin, B717/LIC-101 was administered subcutaneously around the tumor.Results: The B717/LIC-101 complex inhibited the expression of bcl-2 protein and the growth of tumor cell lines in vitro in a sequence-specific manner in the concentration range of 3 to 100 nmol/L. Furthermore, the complex had a strong antitumor activity when administered intravenously in the mouse model of liver metastasis. B717 (siRNA) was shown to be delivered to tumor cells in the mouse liver, but only when complexed with LIC-101. The complex also inhibited tumor cell growth in the mouse model bearing prostate cancer.Conclusions: By combining siRNA with our cationic liposome, we overcame the difficulty of administering siRNA to animals in ways that can be applied in human therapy. Although our siRNA/liposome complex is not yet in clinical trials, it is expected to provide a novel siRNA therapy for cancer patients.

Small cell lung cancer (SCLC) is one of the most aggressive types of cancers because of its early development of regional and distant metastases. Novel and more effective therapeutic strategies for the treatment of this disease are necessary. Bisphosphonates (BP), originally developed to treat bone disease, have recently been identified as attractive cancer theraptic agents. In this study, we investigated the anti-proliferative effects of zoledronic acid (ZOL) as a single agent and in combination with other agents. ZOL inhibited both farnesylation and geranylgeranylation of RAS related proteins, induced apoptosis and inhibited the growth of eight out of twelve SCLC cell lines examined the in vitro. ZOL also significantly inhibited SCLC tumor growth and SBC-3 cells transplanted subcutaneously into nude mice. Its suppressive effect have not been completed, the addition effect of ZOL with other agents was examined. ZOL augmented the effects of paclitaxel, etoposide, cisplatinum and irinotecan synergistically, and imatinib mesylate additively. These findings indicate that ZOL and combined use of these agents may be promising therapeutic strategies for SCLC.

The mainstay in the management of invasive bladder cancer continues to be radical cystectomy. With regard to improvement of quality of life, however, therapies that preserve the bladder are desirable. We investigated the use of intravesical PLK-1 small interfering RNA (siRNA) against bladder cancer. Patients with bladder cancers expressing high levels of PLK-1 have a poor prognosis compared with patients with low expression. Using siRNA/cationic liposomes, the expression of endogenous PLK-1 could be suppressed in bladder cancer cells in a time-and dose-dependent manner. As a consequence, PLK-1 functions were disrupted. Inhibition of bipolar spindle formation, accumulation of cyclin B1, reduced cell proliferation, and induction of apoptosis were observed. In order to determine the efficacy of the siRNA/liposomes in vivo, we established an orthotopic mouse model using a LUC-labeled bladder cancer cell line, UM-UC-3 LUC . PLK-1 siRNA was successfully transfected into the cells, reduced PLK-1 expression, and prevented the growth of bladder cancer in this mouse model. This is the first demonstration, to our knowledge, of inhibition of cancer growth in the murine bladder by intravesical siRNA/cationic liposomes. We believe intravesical siRNA instillation against bladder cancer will be useful as a therapeutic tool.

Nitrogen containing-bisphosphonates (N-BPs), widely used to treat bone diseases, have direct antitumor effects via the inactivation of Ras proteins. In addition to the direct antitumor activities, N-BPs expand gdT cells, which exhibit major histocompatibility complex-unrestricted lytic activity. BPs accumulate intermediate metabolites which may be tumor antigens in target cells. The purpose of our study was to clarify the cytotoxicity of gd T cells expanded ex vivo by the most potent N-BP, zoledronate (ZOL). Especially, we focused on the importance of pretreatment against target cells also with ZOL; 1 mM ZOL plus IL-2 increased the absolute number of gdT cells 298-768 fold for 14 days incubation. The small cell lung cancer and fibrosarcoma cell lines pretreated with 5 mM ZOL showed a marked increase in sensitivity to lysis by gdT cells. While, untreated cell lines were much less sensitive to lysis by gdT cells. Video microscopy clearly demonstrated that gdT cells killed target cells pre-treated with ZOL within 3 hr. Pretreatment with 80 mg/kg ZOL also significantly enhanced the antitumor activity of gdT cells in mice xenografted with SBC-5 cells. These findings show that ZOL significantly stimulated the proliferation of gdT cells and that gdT cells required pre-treatment with ZOL for cytotoxic activity against target cells. ' 2005 Wiley-Liss, Inc.

Proteome analysis of bladder cancer with narrow-range pH 2-DE has identified a novel protein on chromosome 7 encoded by ORF 24 (C7orf24) as one of the highly expressed proteins in cancer cells. C7orf24 is currently registered in the protein database as a hypothetical protein with unknown function. The homologs of C7orf24 in other animals have also been registered as putative protein genes. Western blot analysis using a mAb against C7orf24 confirmed its higher expression in bladder cancer compared with normal tissue. Several other cancer cell lines were also found to express C7orf24. However, the introduction of C7orf24 into Rat-1 or NIH3T3 cells did not cause malignant transformation. A stable transfectant of NIH3T3 cells with recombinant retrovirus vector was produced for a growth rate assay, and a higher growth rate was observed in C7orf24-expressing cells compared with the controls. Six kinds of small interfering RNAs (siRNAs) were then produced, and C7orf24-siRNA#5 showed a strong knockdown effect on protein expression and significant antiproliferative effects on cancer cell lines were demonstrated by the MTT assay. Therefore, C7orf24 may have an important role in cancer cell proliferation, and may be an appropriate therapeutic target molecule against cancer.

The mainstay in the management of invasive bladder cancer continues to be radical cystectomy. With regard to improvement of quality of life, however, therapies that preserve the bladder are desirable. We investigated the use of intravesical PLK-1 small interfering RNA (siRNA) against bladder cancer. Patients with bladder cancers expressing high levels of PLK-1 have a poor prognosis compared with patients with low expression. Using siRNA/cationic liposomes, the expression of endogenous PLK-1 could be suppressed in bladder cancer cells in a time- and dose-dependent manner. As a consequence, PLK-1 functions were disrupted. Inhibition of bipolar spindle formation, accumulation of cyclin B1, reduced cell proliferation, and induction of apoptosis were observed. In order to determine the efficacy of the siRNA/liposomes in vivo, we established an orthotopic mouse model using a LUC-labeled bladder cancer cell line, UM-UC-3(LUC). PLK-1 siRNA was successfully transfected into the cells, reduced PLK-1 expression, and prevented the growth of bladder cancer in this mouse model. This is the first demonstration, to our knowledge, of inhibition of cancer growth in the murine bladder by intravesical siRNA/cationic liposomes. We believe intravesical siRNA instillation against bladder cancer will be useful as a therapeutic tool.

No abstract

Zoledronic acid (ZOL), a nitrogen-containing bisphosphonate, exerts anti-tumor effects by inhibiting the prenylation of small GTPases. We have also reported that ZOL shows an anti-leukemic effect by inducing apoptosis throughout the S phase to the G 2 /M boundary. Here, we studied the effects of ZOL on various cell cycle regulators, including p53, cyclin-dependent kinases (CDKs), CDK inhibitors and cyclins, using BV173 leukemia and HCT116 colorectal carcinoma cell lines, harboring wild-type (wt-) p53. ZOL induced the accumulation of neither p53 nor p21 WAF1/CIP1 during the execution of apoptosis in BV173 cells. Therefore, we investigated the dependence of ZOL-induced apoptosis on intact p53 by using wt-p53 HCT116 and a p53-degraded HCT116 subline, and observed no significant difference. ne particularly attractive approach in the development of more potent anticancer therapies involves the blockade of deregulated cellular signaling pathways. The use of imatinib mesylate, a competitive inhibitor of ABL tyrosine kinase, on Philadelphia-positive leukemias is the paradigm for this type of tumor-selective targeted therapy, 1) and gefitinib, a selective inhibitor of epidermal growth factor receptor-tyrosine kinase inhibitor, has shown promise in patients with solid tumors. 2)Because Ras signaling pathways are frequently overly active in leukemias and solid tumors, an approach that inhibits the posttranslational prenylation of small GTPases by farnesyl transferase inhibitors or nitrogen-containing bisphosphonates (BPs) is intriguing.3-6) One such nitrogen-containing BP is zoledronic acid (ZOL), and recent studies showed that it has in vitro antiproliferative potency against several types of cancer cell lines.4, 5) Also, in a previous study, we found that ZOL potentially induces apoptosis in leukemic cell lines and also prolongs the survival of mice xenografted with a leukemic cell line. 7)Anticancer drugs generally induce apoptosis by triggering biochemical events involved not only in apoptotic pathways, but also in cell cycle regulation. 8) To characterize the underlying mechanisms of apoptotic induction in cancer cells by ZOL, we assessed its effects on cell cycle regulators, including p53, one of the key regulators targeted by various anticancer agents. By testing cancer cell lines with wild-type (wt-) p53 and p53-degraded cell lines, we reveal for the first time that the anti-tumor effect of ZOL is not reduced by the loss of p53 function, although the contribution of p53 to the anti-tumor effect of