MicroRNA-383 acts as a tumor suppressor in colorectal cancer by modulating CREPT/RPRD1B expression.

CREPT (Cell-cycle-related and expression-elevated protein in tumor)/RPRD1B, a novel protein that enhances the transcription of Cyclin D1 to promote cell proliferation during tumorigenesis, was demonstrated highly expressed in most of tumors. However, it remains unclear how CREPT is regulated in colorectal cancers. In this study, we report that miR-383 negatively regulates CREPT expression. We observed that CREPT was up-regulated but the expression of miR-383 was down regulated in both colon cancer cell lines and colon tumor tissues. Intriguingly, we found that enforced expression of miR-383 inhibited the expression of CREPT at both the mRNA and protein level. Using a luciferase reporter, we showed that miR-383 targeted the 3'-UTR of CREPT mRNA directly. Consistently we observed that over expression of miR-383 shortened the half-life of CREPT mRNA in varieties of colorectal cancer cells. Furthermore, restoration of miR-383 inhibited cell growth and colony formation of colon cancer cells accompanied by inhibition of expression of CREPT and related downstream genes. Finally, we demonstrated that stable over expression of miR-383 in colon cancer cells decreased the growth of the tumors. Our results revealed that the abundant expression of CREPT in colorectal cancers is attributed to the decreased level of miR-383. This study shed a new light on the potential therapeutic therapy strategy for colorectal cancers using introduced miRNA.

Natural product derivative Gossypolone inhibits Musashi family of RNA-binding proteins.

BACKGROUND: The Musashi (MSI) family of RNA-binding proteins is best known for the role in post-transcriptional regulation of target mRNAs. Elevated MSI1 levels in a variety of human cancer are associated with up-regulation of Notch/Wnt signaling. MSI1 binds to and negatively regulates translation of Numb and APC (adenomatous polyposis coli), negative regulators of Notch and Wnt signaling respectively. METHODS: Previously, we have shown that the natural product (-)-gossypol as the first known small molecule inhibitor of MSI1 that down-regulates Notch/Wnt signaling and inhibits tumor xenograft growth in vivo. Using a fluorescence polarization (FP) competition assay, we identified gossypolone (Gn) with a > 20-fold increase in Ki value compared to (-)-gossypol. We validated Gn binding to MSI1 using surface plasmon resonance, nuclear magnetic resonance, and cellular thermal shift assay, and tested the effects of Gn on colon cancer cells and colon cancer DLD-1 xenografts in nude mice. RESULTS: In colon cancer cells, Gn reduced Notch/Wnt signaling and induced apoptosis. Compared to (-)-gossypol, the same concentration of Gn is less active in all the cell assays tested. To increase Gn bioavailability, we used PEGylated liposomes in our in vivo studies. Gn-lip via tail vein injection inhibited the growth of human colon cancer DLD-1 xenografts in nude mice, as compared to the untreated control (P < 0.01, n = 10). CONCLUSION: Our data suggest that PEGylation improved the bioavailability of Gn as well as achieved tumor-targeted delivery and controlled release of Gn, which enhanced its overall biocompatibility and drug efficacy in vivo. This provides proof of concept for the development of Gn-lip as a molecular therapy for colon cancer with MSI1/MSI2 overexpression.

Overexpression of 17ß-hydroxysteroid dehydrogenase type 10 increases pheochromocytoma cell growth and resistance to cell death.

BACKGROUND: 17ß-hydroxysteroid dehydrogenase type 10 (HSD10) has been shown to play a protective role in cells undergoing stress. Upregulation of HSD10 under nutrient-limiting conditions leads to recovery of a homeostatic state. Across disease states, increased HSD10 levels can have a profound and varied impact, such as beneficial in Parkinson's disease and harmful in Alzheimer's disease. Recently, HSD10 overexpression has been observed in some prostate and bone cancers, consistently correlating with poor patient prognosis. As the role of HSD10 in cancer remains underexplored, we propose that cancer cells utilize this enzyme to promote cancer cell survival under cell death conditions. METHODS: The proliferative effect of HSD10 was examined in transfected pheochromocytoma cells by growth curve analysis and a xenograft model. Fluctuations in mitochondrial bioenergetics were evaluated by electron transport chain complex enzyme activity assays and energy production. Additionally, the effect of HSD10 on pheochromocytoma resistance to cell death was investigated using TUNEL staining, MTT, and complex IV enzyme activity assays. RESULTS: In this study, we examined the tumor-promoting effect of HSD10 in pheochromocytoma cells. Overexpression of HSD10 increased pheochromocytoma cell growth in both in vitro cell culture and an in vivo xenograft mouse model. The increases in respiratory enzymes and energy generation observed in HSD10-overexpressing cells likely supported the accelerated growth rate observed. Furthermore, cells overexpressing HSD10 were more resistant to oxidative stress-induced perturbation. CONCLUSIONS: Our findings demonstrate that overexpression of HSD10 accelerates pheochromocytoma cell growth, enhances cell respiration, and increases cellular resistance to cell death induction. This suggests that blockade of HSD10 may halt and/or prevent cancer growth, thus providing a promising novel target for cancer patients as a screening or therapeutic option.

Hepatitis C virus infection and hepatic stellate cell activation downregulate miR-29: miR-29 overexpression reduces hepatitis C viral abundance in culture.

BACKGROUND: Chronic hepatitis C virus (HCV)-induced liver fibrosis involves upregulation of transforming growth factor (TGF)-ß and subsequent hepatic stellate cell (HSC) activation. MicroRNAs (miRNAs) regulate HCV infection and HSC activation. METHODS: TaqMan miRNA profiling identified 12 miRNA families differentially expressed between chronically HCV-infected human livers and uninfected controls. To identify pathways affected by miRNAs, we developed a new algorithm (pathway analysis of conserved targets), based on the probability of conserved targeting. RESULTS: This analysis suggested a role for miR-29 during HCV infection. Of interest, miR-29 was downregulated in most HCV-infected patients. miR-29 regulates expression of extracellular matrix proteins. In culture, HCV infection downregulated miR-29, and miR-29 overexpression reduced HCV RNA abundance. miR-29 also appears to play a role in HSCs. Hepatocytes and HSCs contribute similar amounts of miR-29 to whole liver. Both activation of primary HSCs and TGF-ß treatment of immortalized HSCs downregulated miR-29. miR-29 overexpression in LX-2 cells decreased collagen expression and modestly decreased proliferation. miR-29 downregulation by HCV may derepress extracellular matrix synthesis during HSC activation. CONCLUSIONS: HCV infection downregulates miR-29 in hepatocytes and may potentiate collagen synthesis by reducing miR-29 levels in activated HSCs. Treatment with miR-29 mimics in vivo might inhibit HCV while reducing fibrosis.

Correlation between microRNA expression levels and clinical parameters associated with chronic hepatitis C viral infection in humans.

MicroRNAs (miRNAs) are small RNAs that regulate gene expression pathways. Previous studies have shown interactions between hepatitis C virus (HCV) and host miRNAs. We measured miR-122 and miR-21 levels in HCV-infected human liver biopsies relative to uninfected human livers and correlated these with clinical patient data. miR-122 is required for HCV replication in vitro, and miR-21 is involved in cellular proliferation and tumorigenesis. We found that miR-21 expression correlated with viral load, fibrosis and serum liver transaminase levels. miR-122 expression inversely correlated with fibrosis, liver transaminase levels and patient age. miR-21 was induced ∼twofold, and miR-122 was downregulated on infection of cultured cells with the HCV J6/JFH infectious clone, thus establishing a link to HCV. To further examine the relationship between fibrosis and the levels of miR-21 and miR-122, we measured their expression levels in a mouse carbon tetrachloride fibrosis model. As in the HCV-infected patient samples, fibrotic stage positively correlated with miR-21 and negatively correlated with miR-122 levels. Transforming growth factor ß (TGF-ß) is a critical mediator of fibrogenesis. We identified SMAD7 as a novel miR-21 target. SMAD7 is a negative regulator of TGF-ß signaling, and its expression is induced by TGF-ß. To confirm the relationship between miR-21 and the TGF-ß signaling pathway, we measured the effect of miR-21 on a TGF-ß-responsive reporter. We found that miR-21 enhanced TGF-ß signaling, further supporting a relationship between miR-21 and fibrosis. We suggest a model in which miR-21 targeting of SMAD7 could increase TGF-ß signaling, leading to increased fibrogenesis.

MicroRNA-21 is upregulated during the proliferative phase of liver regeneration, targets Pellino-1, and inhibits NF-kappaB signaling.

During liver regeneration, normally quiescent liver cells reenter the cell cycle, nonparenchymal and parenchymal cells divide, and proper liver architecture is restored. The gene expression programs regulating these transitions are not completely understood. MicroRNAs are a newly discovered class of small regulatory RNAs that silence messenger RNAs by binding to their 3'-untranslated regions (UTRs). A number of microRNAs, including miR-21, have been shown to be involved in regulation of cell proliferation. We performed partial hepatectomies on mice and allowed the liver to regenerate for 1, 6, 12, 24, and 48 h and 4 and 7 days. We compared the expression of miR-21 in the posthepatectomy liver to the prehepatectomy liver by Northern blot and found that miR-21 was upregulated during the early stages of liver regeneration. NF-kappaB signaling is also activated very early during liver regeneration. It has been previously reported that NF-kappaB upregulates the miR-21 precursor transcript. The predicted miR-21 target, Pellino (Peli1), is a ubiquitin ligase involved in activating NF-kappaB signaling. We observed an inverse correlation between miR-21 and Peli1 mRNA levels during liver regeneration. miR-21 overexpression in cultured cells inhibited a Peli1 3'-UTR luciferase reporter. Using NF-kappaB reporter assays, we determined that miR-21 overexpression inhibits NF-kappaB signaling. In conclusion, miR-21 expression was upregulated during early stages of liver regeneration. Targeting of Peli1 by miR-21 could potentially provide the basis for a negative feedback cycle regulating NF-kappaB signaling.

Targeting the interaction between RNA-binding protein HuR and FOXQ1 suppresses breast cancer invasion and metastasis.

Patients diagnosed with metastatic breast cancer have a dismal 5-year survival rate of only 24%. The RNA-binding protein Hu antigen R (HuR) is upregulated in breast cancer, and elevated cytoplasmic HuR correlates with high-grade tumors and poor clinical outcome of breast cancer. HuR promotes tumorigenesis by regulating numerous proto-oncogenes, growth factors, and cytokines that support major tumor hallmarks including invasion and metastasis. Here, we report a HuR inhibitor KH-3, which potently suppresses breast cancer cell growth and invasion. Furthermore, KH-3 inhibits breast cancer experimental lung metastasis, improves mouse survival, and reduces orthotopic tumor growth. Mechanistically, we identify FOXQ1 as a direct target of HuR. KH-3 disrupts HuR-FOXQ1 mRNA interaction, leading to inhibition of breast cancer invasion. Our study suggests that inhibiting HuR is a promising therapeutic strategy for lethal metastatic breast cancer.

A non-intrusive evaluation method for tumor-targeting characteristics of nanomedicines based on in vivo near-infrared fluorescence imaging.

We developed a novel evaluation method for tumor-targeting characteristics of nanomedicines, average tumor-targeting index (average TTI) and "area under the tumor-targeting index-time curve" (AUTC) were established as the indicators for tumor targeting of nanomedicines based on NIR fluorescence imaging, which helps real-time monitoring of targeting ability and tumor changes in vivo without culling animals.

Advances in microRNAs: implications for gene therapists.

MicroRNAs (miRNAs) are a class of small regulatory RNAs that are thought to regulate the expression of as many as one-third of all human messenger RNAs (mRNAs). miRNAs are thought to be involved in diverse biological processes, including tumorigenesis. Analysis of miRNA levels may have diagnostic implications. Evidence shows that numerous viruses interact with the miRNA machinery, and that a number of viruses encode their own miRNAs. It seems likely that miRNAs will be implicated in many human diseases. Manipulation of miRNA levels by gene therapy provides an attractive new approach for therapeutic development. This review focuses on approaches to manipulate miRNA levels in cells and in vivo, and the implications for gene therapy. Furthermore, we discuss the use of endogenous miRNAs as scaffolds for the expression of RNA interference (RNAi) as well as competition between exogenous RNAi triggers and endogenous miRNAs. Because short interfering RNAs can also act as miRNAs, seed matches with the 3' untranslated regions of genes should be avoided to prevent off-target effects. Last, we discuss the use of miRNAs to avoid immune responses to viral vectors.

Patterns of gene expression in different histotypes of epithelial ovarian cancer correlate with those in normal fallopian tube, endometrium, and colon.

PURPOSE: Epithelial ovarian cancers are thought to arise from flattened epithelial cells that cover the ovarian surface or that line inclusion cysts. During malignant transformation, different histotypes arise that resemble epithelial cells from normal fallopian tube, endometrium, and intestine. This study compares gene expression in serous, endometrioid, clear cell, and mucinous ovarian cancers with that in the normal tissues that they resemble. EXPERIMENTAL DESIGN: Expression of 63,000 probe sets was measured in 50 ovarian cancers, in 5 pools of normal ovarian epithelial brushings, and in mucosal scrapings from 4 normal fallopian tube, 5 endometrium, and 4 colon specimens. Using rank-sum analysis, genes whose expressions best differentiated the ovarian cancer histotypes and normal ovarian epithelium were used to determine whether a correlation based on gene expression existed between ovarian cancer histotypes and the normal tissues they resemble. RESULTS: When compared with normal ovarian epithelial brushings, alterations in serous tumors correlated with those in normal fallopian tube (P = 0.0042) but not in other normal tissues. Similarly, mucinous cancers correlated with those in normal colonic mucosa (P = 0.0003), and both endometrioid and clear cell histotypes correlated with changes in normal endometrium (P = 0.0172 and 0.0002, respectively). Mucinous cancers displayed the greatest number of alterations in gene expression when compared with normal ovarian epithelial cells. CONCLUSION: Studies at a molecular level show distinct expression profiles of different histologies of ovarian cancer and support the long-held belief that histotypes of ovarian cancers come to resemble normal fallopian tube, endometrial, and colonic epithelium. Several potential molecular markers for mucinous ovarian cancers have been identified.

A genetically defined model for human ovarian cancer.

Disruptions of the p53, retinoblastoma (Rb), and RAS signaling pathways and activation of human telomerase reverse transcriptase (hTERT) are common in human ovarian cancer; however, their precise role in ovarian cancer development is not clear. We thus introduced the catalytic subunit of hTERT, the SV40 early genomic region, and the oncogenic alleles of human HRAS or KRAS into human ovarian surface epithelial cells and examined the phenotype and gene expression profile of those cells. Disruption of p53 and Rb pathway by SV40 early genomic region and hTERT immortalized but did not transform the cells. Introduction of HRAS(V12) or KRAS(V12) into the immortalized cells, however, allowed them to form s.c. tumors after injection into immunocompromised mice. Peritoneal injection of the transformed cells produced undifferentiated carcinoma or malignant mixed Mullerian tumor and developed ascites; the tumor cells are focally positive for CA125 and mesothelin. Gene expression profile analysis of transformed cells revealed elevated expression of several cytokines, including interleukin (IL)-1beta, IL-6, and IL-8, that are up-regulated by the nuclear factor-kappaB pathway, which is known to contribute to the tumor growth of naturally ovarian cancer cells. Incubation with antibodies to IL-1beta or IL-8 led to apoptosis in the ras-transformed cells and ovarian cancer cells but not in immortalized cells that had not been transformed. Thus, the transformed human ovarian surface epithelial cells recapitulated many features of natural ovarian cancer including a subtype of ovarian cancer histology, formation of ascites, CA125 expression, and nuclear factor-kappaB-mediated cytokine activation. These cells provide a novel model system to study human ovarian cancer.

Overcoming chemo/radio-resistance of pancreatic cancer by inhibiting STAT3 signaling.

Chemo/radio-therapy resistance to the deadly pancreatic cancer is mainly due to the failure to kill pancreatic cancer stem cells (CSCs). Signal transducer and activator of transcription 3 (STAT3) is activated in pancreatic CSCs and, therefore, may be a valid target for overcoming therapeutic resistance. Here we investigated the potential of STAT3 inhibition in sensitizing pancreatic cancer to chemo/radio-therapy. We found that the levels of nuclear pSTAT3 in pancreatic cancer correlated with advanced tumor grade and poor patient outcome. Liposomal delivery of a STAT3 inhibitor FLLL32 (Lip-FLLL32) inhibited STAT3 phosphorylation and STAT3 target genes in pancreatic cancer cells and tumors. Consequently, Lip-FLLL32 suppressed pancreatic cancer cell growth, and exhibited synergetic effects with gemcitabine and radiation treatment in vitro and in vivo. Furthermore, Lip-FLLL32 reduced ALDH1-positive CSC population and modulated several potential stem cell markers. These results demonstrate that Lip-FLLL32 suppresses pancreatic tumor growth and sensitizes pancreatic cancer cells to radiotherapy through inhibition of CSCs in a STAT3-dependent manner. By targeting pancreatic CSCs, Lip-FLLL32 provides a novel strategy for pancreatic cancer therapy via overcoming radioresistance.

NDN is an imprinted tumor suppressor gene that is downregulated in ovarian cancers through genetic and epigenetic mechanisms.

NDN is a maternally imprinted gene consistently expressed in normal ovarian epithelium, is dramatically downregulated in the majority of ovarian cancers. Little or no NDN expression could be detected in 73% of 351 epithelial ovarian cancers. NDN was also downregulated in 10 ovarian cancer cell lines with total loss in 6 of 10. Re-expression of NDN decreased Bcl-2 levels and induced apoptosis, which significantly inhibited ovarian cancer cell growth in cell culture and in xenografts. In addition, re-expression of NDN inhibited cell migration by decreasing actin stress fiber and focal adhesion complex formation through deactivation of Src, FAK and RhoA. Loss of NDN expression in ovarian cancers could be attributed to LOH in 28% of 18 informative cases and to hypermethylation of CpG sites 1 and 2 of NDN promoter in 23% and 30% of 43 ovarian cancers, respectively. Promoter hypermethylation was also found in 5 of 10 ovarian cancer cell lines. Treatment with the demethylating agent 5-aza-2'-deoxycytidine restored NDN expression in 4 of 7 cell lines with enhanced promoter methylation levels. These observations support the conclusion that NDN is an imprinted tumor suppressor gene which affects cancer cell motility, invasion and growth and that its loss of function in ovarian cancer can be caused by both genetic and epigenetic mechanisms.

Selection of potential markers for epithelial ovarian cancer with gene expression arrays and recursive descent partition analysis.

PURPOSE: Advanced-stage epithelial ovarian cancer has a poor prognosis with long-term survival in less than 30% of patients. When the disease is detected in stage I, more than 90% of patients can be cured by conventional therapy. Screening for early-stage disease with individual serum tumor markers, such as CA125, is limited by the fact that no single marker is up-regulated and shed in adequate amounts by all ovarian cancers. Consequently, use of multiple markers in combination might detect a larger fraction of early-stage ovarian cancers. EXPERIMENTAL DESIGN: To identify potential candidates for novel markers, we have used Affymetrix human genome arrays (U95 series) to analyze differences in gene expression of 41,441 known genes and expressed sequence tags between five pools of normal ovarian surface epithelial cells (OSE) and 42 epithelial ovarian cancers of different stages, grades, and histotypes. Recursive descent partition analysis (RDPA) was performed with 102 probe sets representing 86 genes that were up-regulated at least 3-fold in epithelial ovarian cancers when compared with normal OSE. In addition, a panel of 11 genes known to encode potential tumor markers [mucin 1, transmembrane (MUC1), mucin 16 (CA125), mesothelin, WAP four-disulfide core domain 2 (HE4), kallikrein 6, kallikrein 10, matrix metalloproteinase 2, prostasin, osteopontin, tetranectin, and inhibin] were similarly analyzed. RESULTS: The 3-fold up-regulated genes were examined and four genes [Notch homologue 3 (NOTCH3), E2F transcription factor 3 (E2F3), GTPase activating protein (RACGAP1), and hematological and neurological expressed 1 (HN1)] distinguished all tumor samples from normal OSE. The 3-fold up-regulated genes were analyzed using RDPA, and the combination of elevated claudin 3 (CLDN3) and elevated vascular endothelial growth factor (VEGF) distinguished the cancers from normal OSE. The 11 known markers were analyzed using RDPA, and a combination of HE4, CA125, and MUC1 expression could distinguish tumor from normal specimens. Expression at the mRNA level in the candidate markers was examined via semiquantitative reverse transcription-PCR and was found to correlate well with the array data. Immunohistochemistry was performed to identify expression of the genes at the protein level in 158 ovarian cancers of different histotypes. A combination of CLDN3, CA125, and MUC1 stained 157 (99.4%) of 158 cancers, and all of the tumors were detected with a combination of CLDN3, CA125, MUC1, and VEGF. CONCLUSIONS: Our data are consistent with the possibility that a limited number of markers in combination might identify >99% of epithelial ovarian cancers despite the heterogeneity of the disease.

Tumor suppressive microRNA-137 negatively regulates Musashi-1 and colorectal cancer progression.

Stem cell marker, Musashi-1 (MSI1) is over-expressed in many cancer types; however the molecular mechanisms involved in MSI1 over-expression are not well understood. We investigated the microRNA (miRNA) regulation of MSI1 and the implications this regulation plays in colorectal cancer. MicroRNA miR-137 was identified as a MSI1-targeting microRNA by immunoblotting and luciferase reporter assays. MSI1 protein was found to be highly expressed in 79% of primary rectal tumors (n=146), while miR-137 expression was decreased in 84% of the rectal tumor tissues (n=68) compared to paired normal mucosal samples. In addition to reduced MSI1 protein, exogenous expression of miR-137 inhibited cell growth, colony formation, and tumorsphere growth of colon cancer cells. Finally, in vivo studies demonstrated that induction of miR-137 can decrease growth of human colon cancer xenografts. Our results demonstrate that miR-137 acts as a tumor-suppressive miRNA in colorectal cancers and negatively regulates oncogenic MSI1.

Natural product (-)-gossypol inhibits colon cancer cell growth by targeting RNA-binding protein Musashi-1.

Musashi-1 (MSI1) is an RNA-binding protein that acts as a translation activator or repressor of target mRNAs. The best-characterized MSI1 target is Numb mRNA, whose encoded protein negatively regulates Notch signaling. Additional MSI1 targets include the mRNAs for the tumor suppressor protein APC that regulates Wnt signaling and the cyclin-dependent kinase inhibitor P21(WAF-1). We hypothesized that increased expression of NUMB, P21 and APC, through inhibition of MSI1 RNA-binding activity might be an effective way to simultaneously downregulate Wnt and Notch signaling, thus blocking the growth of a broad range of cancer cells. We used a fluorescence polarization assay to screen for small molecules that disrupt the binding of MSI1 to its consensus RNA binding site. One of the top hits was (-)-gossypol (Ki = 476 ± 273 nM), a natural product from cottonseed, known to have potent anti-tumor activity and which has recently completed Phase IIb clinical trials for prostate cancer. Surface plasmon resonance and nuclear magnetic resonance studies demonstrate a direct interaction of (-)-gossypol with the RNA binding pocket of MSI1. We further showed that (-)-gossypol reduces Notch/Wnt signaling in several colon cancer cell lines having high levels of MSI1, with reduced SURVIVIN expression and increased apoptosis/autophagy. Finally, we showed that orally administered (-)-gossypol inhibits colon cancer growth in a mouse xenograft model. Our study identifies (-)-gossypol as a potential small molecule inhibitor of MSI1-RNA interaction, and suggests that inhibition of MSI1's RNA binding activity may be an effective anti-cancer strategy.

Identification and validation of novel small molecule disruptors of HuR-mRNA interaction.

HuR, an RNA binding protein, binds to adenine- and uridine-rich elements (ARE) in the 3'-untranslated region (UTR) of target mRNAs, regulating their stability and translation. HuR is highly abundant in many types of cancer, and it promotes tumorigenesis by interacting with cancer-associated mRNAs, which encode proteins that are implicated in different tumor processes including cell proliferation, cell survival, angiogenesis, invasion, and metastasis. Drugs that disrupt the stabilizing effect of HuR upon mRNA targets could have dramatic effects on inhibiting cancer growth and persistence. In order to identify small molecules that directly disrupt the HuR-ARE interaction, we established a fluorescence polarization (FP) assay optimized for high throughput screening (HTS) using HuR protein and an ARE oligo from Musashi RNA-binding protein 1 (Msi1) mRNA, a HuR target. Following the performance of an HTS of ∼6000 compounds, we discovered a cluster of potential disruptors, which were then validated by AlphaLISA (Amplified Luminescent Proximity Homogeneous Assay), surface plasmon resonance (SPR), ribonucleoprotein immunoprecipitation (RNP IP) assay, and luciferase reporter functional studies. These compounds disrupted HuR-ARE interactions at the nanomolar level and blocked HuR function by competitive binding to HuR. These results support future studies toward chemical probes for a HuR function study and possibly a novel therapy for HuR-overexpressing cancers.

A systematic SAR study of C10 modified paclitaxel analogues using a combinatorial approach.

A library with 63 paclitaxel analogues modified at the C10 position of paclitaxel has been prepared using parallel solution phase synthesis. Most of the C10 analogues were slightly less active than paclitaxel in the tubulin assembly assay and had reduced potency in the B16 melanoma and MCF-7 cell line cytotoxicity assays. These modifications at C10, however, did not lead to the total loss of activity, indicating that the C10 moiety of paclitaxel may not be directly involved in the drug-microtubule interactions, but could influence its binding affinity to P-glycoprotein. Approximately 50% of the analogues demonstrated better activity against the drug resistant cell line MCF7-ADR. However, the increase in activity was 10-fold at most. This result demonstrates that the cytotoxicity against this drug resistant cancer cell line is sensitive to structural changes at the C10 position of paclitaxel. It was also found that the presence of a nitrogen atom in the C10 substituent might play a role in the interaction of analogues with microtubules.

A PEG-Fmoc conjugate as a nanocarrier for paclitaxel.

We report here that a simple, well-defined, and easy-to-scale up nanocarrier, PEG5000-lysyl-(α-Fmoc-ε-t-Boc-lysine)2 conjugate (PEG-Fmoc), provides high loading capacity, excellent formulation stability and low systemic toxicity for paclitaxel (PTX), a first-line chemotherapeutic agent for various types of cancers. 9-Fluorenylmethoxycarbonyl (Fmoc) was incorporated into the nanocarrier as a functional building block to interact with drug molecules. PEG-Fmoc was synthesized via a three-step synthetic route, and it readily interacted with PTX to form mixed nanomicelles of small particle size (25-30 nm). The PTX loading capacity was about 36%, which stands well among the reported micellar systems. PTX entrapment in this micellar system is achieved largely via an Fmoc/PTX π-π stacking interaction, which was demonstrated by fluorescence quenching studies and (13)C NMR. PTX formulated in PEG-Fmoc micelles demonstrated sustained release kinetics, and in vivo distribution study via near infrared fluorescence imaging demonstrated an effective delivery of Cy5.5-labled PTX to tumor sites. The maximal tolerated dose for PTX/PEG-Fmoc (MTD > 120 mg PTX/kg) is higher than those for most reported PTX formulations, and in vivo therapeutic study exhibited a significantly improved antitumor activity than Taxol, a clinically used formulation of PTX. Our system may hold promise as a simple, safe, and effective delivery system for PTX with a potential for rapid translation into clinical study.

PEG-derivatized embelin as a nanomicellar carrier for delivery of paclitaxel to breast and prostate cancers.

Paclitaxel (PTX) is one of the most effective chemotherapeutic agents for a wide spectrum of cancers, but its therapeutic benefit is often limited by severe side effects. We have developed a micelle-based PTX formulation based on a simple conjugate derived from polyethylene glycol 5000 (PEG(5K)) and embelin (EB). Embelin is a natural product and exhibits antitumor activity through blocking the activity of X-linked inhibitor of apoptosis protein (XIAP). PEG(5K)-EB2 conjugate self-assembles to form stable micelles in aqueous solution and efficiently encapsulates hydrophobic drugs such as PTX. PEG(5K)-EB2 micelles have a relatively low CMC of 0.002 mg/mL (0.35 µM) with sizes in the range of 20 ∼ 30 nm with or without loaded PTX. In vitro cell uptake study showed that the PEG(5K)-EB2 micelles were efficiently taken up by tumor cells. In vitro release study showed that PTX formulated in PEG(5K)-EB2 micelles was slowly released over 5 days with much slower release kinetics than that of Taxol formulation. PTX formulated in PEG(5K)-EB2 micelles exhibited more potent cytotoxicity than Taxol in several cultured tumor cell lines. Total body near infrared fluorescence (NIRF) imaging showed that PEG(5K)-EB2 micelles were selectively accumulated at tumor site with minimal uptake in major organs including liver and spleen. PTX-loaded PEG(5K)-EB2 micelles demonstrated an excellent safety profile with a maximum tolerated dose (MTD) of 100-120 mg PTX/kg in mice, which was significantly higher than that for Taxol (15-20 mg PTX/kg). Finally, PTX formulated in PEG(5K)-EB2 micelles showed superior antitumor activity compared to Taxol in murine models of breast and prostate cancers.