Ubiquitin-tagged substrates are degraded by the 26S proteasome, which is a multisubunit complex comprising a proteolytic 20S core particle capped by 19S regulatory particles. The approval of bortezomib for the treatment of multiple myeloma validated the 20S core particle as an anticancer drug target. Here we describe the small molecule b-AP15 as a previously unidentified class of proteasome inhibitor that abrogates the deubiquitinating activity of the 19S regulatory particle. b-AP15 inhibited the activity of two 19S regulatory-particle-associated deubiquitinases, ubiquitin C-terminal hydrolase 5 (UCHL5) and ubiquitin-specific peptidase 14 (USP14), resulting in accumulation of polyubiquitin. b-AP15 induced tumor cell apoptosis that was insensitive to TP53 status and overexpression of the apoptosis inhibitor BCL2. We show that treatment with b-AP15 inhibited tumor progression in four different in vivo solid tumor models and inhibited organ infiltration in an acute myeloid leukemia model. Our results show that the deubiquitinating activity of the 19S regulatory particle is a new anticancer drug target.

A small library of integrin ligand-paclitaxel conjugates 10-13 was synthesized with the aim of using the tumor-homing cyclo[DKP-RGD] peptidomimetics for site-directed delivery of the cytotoxic drug. All the paclitaxel-RGD constructs 10-13 inhibited biotinylated vitronectin binding to the purified αVβ3 integrin receptor at low nanomolar concentration and showed in vitro cytotoxic activity against a panel of human tumor cell lines similar to that of paclitaxel. Among the cell lines, the cisplatin-resistant IGROV-1/Pt1 cells expressed high levels of integrin αVβ3, making them attractive to be tested in in vivo models. cyclo[DKP-f3-RGD]-PTX 11 displayed sufficient stability in physiological solution and in both human and murine plasma to be a good candidate for in vivo testing. In tumor-targeting experiments against the IGROV-1/Pt1 human ovarian carcinoma xenotransplanted in nude mice, compound 11 exhibited a superior activity compared with paclitaxel, despite the lower (about half) molar dosage used.

The plasma membrane enzyme gamma-glutamyltransferase (GGT) is regarded as critical for the maintenance of intracellular levels of glutathione (GSH). GGT expression has been implicated in drug resistance through elevation of intracellular GSH. The dependence of intracellular GSH on GGT expression was not conclusively ascertained. The present study was designed to investigate the role of GGT and of intracellular GSH levels in modulating proliferation and sensitivity to cisplatin of melanoma cells. GGT transfection resulted in increased growth, both in vitro and in tumour xenografts. In addition, GGT-transfected cells exhibited reduced sensitivity to cisplatin associated with lower DNA platination. A decrease in intracellular GSH levels, rather than an increase, was observed in GGT-transfected cells; moreover, in cysteine-deficient conditions, the expression of GGT did not provide transfected cells with the ability of utilising extracellular GSH. In conclusion, these results indicate that GGT activity confers a growth advantage unrelated with intracellular glutathione supply, and are consistent with the interpretation that cisplatin resistance is the consequence of modifications of cellular pharmacokinetics as a result of extracellular drug inactivation by thiol metabolites originated by GGT-mediated GSH cleavage.

The basement membrane (BM) is a layer of specialized extracellular matrix that surrounds normal prostate glands and preserves tissue integrity. Lack or discontinuity of the BM is a prerequisite for tumor cell invasion into interstitial spaces, thus favoring metastasis. Therefore, BM maintenance represents a barrier against cancer development and progression. In the study, we show that miR-205 participates in a network involving DNp63a, which is essential for maintenance of the BM in prostate epithelium. At the molecular level, DNp63a is able to enhance miR-205 transcription by binding to its promoter, whereas the microRNA can post-transcriptionally limit the amount of DNp63a protein, mostly by affecting DNp63a proteasomal degradation rather than through a canonical miRNA/target interaction. Functionally, miR-205 is able to control the deposition of laminin-332 and its receptor integrin-b4. Hence, pathological loss of miR-205, as widely observed in prostate cancer, may favor tumorigenesis by creating discontinuities in the BM. Here we demonstrate that therapeutic replacement of miR-205 in prostate cancer (PCa) cells can restore BM deposition and 3D organization into normal-like acinar structures, thus hampering cancer progression. MicroRNAs (miRNAs) are short, non-coding RNAs that negatively regulate gene expression at the post-transcriptional level. 1 By hybridizing to at least partially complementary regions on target mRNAs, miRNAs can induce mRNA degradation or translation inhibition, thus finely tuning protein expression in a variety of biological processes. 1 Consequently, aberrant miRNA expression and function have been linked to the pathogenesis of human diseases, including cancer, where specific miRNAs have been proven to act as oncogenes or tumor suppressors. 2 We previously showed that miR-205 is downregulated in prostate cancer (PCa) compared with adjacent non-neoplastic tissue. 3 This finding was then confirmed by several independent studies (reviewed in Gandellini et al. 4 ; Schaefer et al. 5 ), and miR-205 recognized as the best single miRNA able to correctly distinguish prostate tumor from normal tissue. 6 We also reported that miR-205 acts as a tumor suppressor in human prostate, as its reintroduction in PCa cells reverts epithelial-to-mesenchymal transition (EMT), 3 thus suggesting that miR-205 reduction may drive the progression toward a cell phenotype with enhanced invasive properties and favor metastasis. Accordingly, tumors from patients with lymph node dissemination show lower miR-205 expression than those from node-negative patients. 3 However, evidence of a downregulation of the miRNA in clinically localized carcinomas 4 suggests that loss of miR-205 in PCa may anticipate disease progression. To gain insight into this early loss of the miRNA and into the mechanisms of PCa development, we investigated the physiological role of miR-205 in normal prostate.Prostatic epithelium is characterized by three different cell layers: (i) an outer, androgen-independent basal layer, lying on a basement m...

In an attempt to synthesize potential anticancer agents acting by inhibition of topoisomerase I (Topo I) a new series of oxyiminomethyl derivatives in position 7 of camptothecin (CPT) was prepared. The synthesis relied on the condensation of 20S-CPT-7-aldehyde or 20S-CPT-7-ketones with alkyl, aryl, heteroaryl, arylalkyl, and heteroarylalkyl O-substituted hydroxylamines. The compounds were tested for their cytotoxic activity in vitro against H460 non-small lung carcinoma cell line, the activity being for 24 out of 37 compounds in the 0.01-0.3 microM range. A QSAR analysis indicated that lipophilicity is the main parameter correlated with cytotoxicity. Investigation of the DNA-Topo I-drug cleavable complex showed a rough parallelism between cytotoxicity and inhibition of Topo I. Persistence of the DNA cleavage after NaCl-mediated disruption of the ternary complex suggests that for the most potent compounds, e.g., 15, the cytotoxicity was at least in part related to stabilization of the complex, as also supported by the persistence of the DNA-enzyme complex in drug-treated cells. The in vivo antitumor efficacy of the most potent analogue (15) was evaluated in direct comparison with topotecan using human lung tumor xenograft models. In the range of optimal doses (2-3 mg/kg), the improved efficacy of 15 was documented in terms of inhibition of tumor growth and rate of complete response.

No abstract

Synthetic oligodeoxynucleotides expressing CpG motifs (CpG-ODN) are a Toll-like receptor 9 (TLR9) agonist that can enhance the antitumor activity of DNA-damaging chemotherapy and radiation therapy in preclinical mouse models. We hypothesized that the success of these combinations is related to the ability of CpG-ODN to modulate genes involved in DNA repair. We conducted an in silico analysis of genes implicated in DNA repair in data sets obtained from murine colon carcinoma cells in mice injected intratumorally with CpG-ODN and from splenocytes in mice treated intraperitoneally with CpG-ODN. CpG-ODN treatment caused downregulation of DNA repair genes in tumors. Microarray analyses of human IGROV-1 ovarian carcinoma xenografts in mice treated intraperitoneally with CpG-ODN confirmed in silico findings. When combined with the DNA-damaging drug cisplatin, CpG-ODN significantly increased the life span of mice compared with individual treatments. In contrast, CpG-ODN led to an upregulation of genes involved in DNA repair in immune cells. Cisplatin-treated patients with ovarian carcinoma as well as anthracycline-treated patients with breast cancer who are classified as "CpG-like" for the level of expression of CpG-ODN modulated DNA repair genes have a better outcome than patients classified as "CpG-untreated-like," indicating the relevance of these genes in the tumor cell response to DNA-damaging drugs. Taken together, the findings provide evidence that the tumor microenvironment can sensitize cancer cells to DNA-damaging chemotherapy, thereby expanding the benefits of CpG-ODN therapy beyond induction of a strong immune response. Cancer Res; 71(20); 6382-90. Ó2011 AACR.

Survivin is a member of the inhibitor of apoptosis protein (IAP) family, which has been implicated in inhibition of apoptosis and control of mitotic progression. The finding that survivin is overexpressed in most human tumors but absent in normal adult tissues has led to the proposal of survivin as a promising therapeutic target for anticancer therapies. We decided to evaluate the effects of a ribozyme-based strategy for survivin inhibition in androgen-independent human prostate cancer cells. We constructed a Moloney-based retroviral vector expressing a ribozyme targeting the 3 0 end of the CUA 110 triplet in survivin mRNA, encoded as a chimeric RNA within adenoviral VA1 RNA. Polyclonal cell populations obtained by infection with the retroviral vector of two androgen-independent human prostate cancer cell lines (DU145 and PC-3) were selected for the study. Ribozymeexpressing prostate cancer cells were characterized by a significant reduction of survivin expression compared to parental cells transduced with a control ribozyme; the cells became polyploid, underwent caspase-9-dependent apoptosis and showed an altered pattern of gene expression, as detected by oligonucleotide array analysis. Survivin inhibition also increased the susceptibility of prostate cancer cells to cisplatin-induced apoptosis and prevented tumor formation when cells were xenografted in athymic nude mice. These findings suggest that manipulation of the antiapoptotic survivin pathway may provide a novel approach for the treatment of androgen-independent prostate cancer.