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1.  Selective Androgen Receptor Modulators (SARMs) Negatively Regulate Triple-Negative Breast Cancer Growth and Epithelial:Mesenchymal Stem Cell Signaling 
PLoS ONE  2014;9(7):e103202.
The androgen receptor (AR) is the most highly expressed steroid receptor in breast cancer with 75–95% of estrogen receptor (ER)-positive and 40–70% of ER-negative breast cancers expressing AR. Though historically breast cancers were treated with steroidal androgens, their use fell from favor because of their virilizing side effects and the emergence of tamoxifen. Nonsteroidal, tissue selective androgen receptor modulators (SARMs) may provide a novel targeted approach to exploit the therapeutic benefits of androgen therapy in breast cancer.
Materials and Methods
Since MDA-MB-453 triple-negative breast cancer cells express mutated AR, PTEN, and p53, MDA-MB-231 triple-negative breast cancer cells stably expressing wildtype AR (MDA-MB-231-AR) were used to evaluate the in vitro and in vivo anti-proliferative effects of SARMs. Microarray analysis and epithelial:mesenchymal stem cell (MSC) co-culture signaling studies were performed to understand the mechanisms of action.
Dihydrotestosterone and SARMs, but not bicalutamide, inhibited the proliferation of MDA-MB-231-AR. The SARMs reduced the MDA-MB-231-AR tumor growth and tumor weight by greater than 90%, compared to vehicle-treated tumors. SARM treatment inhibited the intratumoral expression of genes and pathways that promote breast cancer development through its actions on the AR. SARM treatment also inhibited the metastasis-promoting paracrine factors, IL6 and MMP13, and subsequent migration and invasion of epithelial:MSC co-cultures.
1. AR stimulation inhibits paracrine factors that are important for MSC interactions and breast cancer invasion and metastasis. 2. SARMs may provide promise as novel targeted therapies to treat AR-positive triple-negative breast cancer.
PMCID: PMC4114483  PMID: 25072326
2.  Direct endothelial junction restoration results in significant tumor vascular normalization and metastasis inhibition in mice 
Oncotarget  2014;5(9):2761-2777.
Tumor blood vessels are leaky and immature, which causes inadequate blood supply to tumor tissues resulting in hypoxic microenvironment and promotes metastasis. Here we have explored tumor vessel modulating activity of Sac-1004, a recently developed molecule in our lab, which directly potentiates VE-cadherin-mediated endothelial cell junction. Sac-1004 could enhance vascular junction integrity in tumor vessels and thereby inhibit vascular leakage and enhance vascular perfusion. Improved perfusion enabled Sac-1004 to have synergistic anti-tumor effect on cisplatin-mediated apoptosis of tumor cells. Interestingly, characteristics of normalized blood vessels namely reduced hypoxia, improved pericyte coverage and decreased basement membrane thickness were readily observed in tumors treated with Sac-1004. Remarkably, Sac-1004 was also able to inhibit lung and lymph node metastasis in MMTV and B16BL6 tumor models. This was in correlation with a reduction in epithelial-to-mesenchymal transition of tumor cells with considerable diminution in expression of related transcription factors. Moreover, cancer stem cell population dropped substantially in Sac-1004 treated tumor tissues. Taken together, our results showed that direct restoration of vascular junction could be a significant strategy to induce normalization of tumor blood vessels and reduce metastasis.
PMCID: PMC4058043  PMID: 24811731
Vascular permeability; Hypoxia; Normalization; Epithelial-to-mesenchymal transition; Sac-1004
3.  Discovery of 4-Aryl-2-benzoyl-imidazoles As Tubulin Polymerization Inhibitor with Potent Antiproliferative Properties 
Journal of medicinal chemistry  2013;56(8):3318-3329.
A series of 4-aryl-2-benzoyl-imidazoles were designed and synthesized based on our previously reported 2-aryl-4-benzoyl-imidazole (ABI) derivatives. The new structures reversed the aryl group and the benzoyl group of previous ABI structures and were named as reverse ABI (RABI) analogs. RABIs were evaluated for biological activity against 8 cancer cell lines including multidrug-resistant cancer cell lines. In vitro assays indicated that several RABI compounds had excellent antiproliferative properties with IC50 values in the low nanomolar range. The average IC50 of the most active compound 12a is 14 nM. In addition, the mechanism of action of these new analogs was investigated by cell cycle analysis, tubulin polymerization assay, competitive mass spectrometry binding assay and molecular docking studies. These studies confirmed that these new RABI analogs maintain their mechanisms of action by disrupting tubulin polymerization, similar to their parental ABI analogs.
PMCID: PMC3668676  PMID: 23547728
4.  Orally Bioavailable Tubulin Antagonists for Paclitaxel-Refractory Cancer 
Pharmaceutical research  2012;29(11):3053-3063.
To evaluate the efficacy and oral activity of two promising indoles, (2-(1H-indol-3-yl)-1H-imidazol-4-yl)(3,4,5-trimethoxyphenyl)methanone [compound II] and (2-(1H-indol-5-ylamino)-thiazol-4-yl)(3,4,5-trimethoxyphenyl)methanone [compound IAT], in paclitaxel- and docetaxel-resistant tumor models in vitro and in vivo.
The in vitro drug-like properties, including potency, solubility, metabolic stability, and drug-drug interactions were examined for our two active compounds. An in vivo pharmacokinetic study and antitumor efficacy study were also completed to compare their efficacy with docetaxel.
Both compounds bound to the colchicine-binding site on tubulin, and inhibited tubulin polymerization, resulting in highly potent cytotoxic activity in vitro. While the potency of paclitaxel and docetaxel was compromised in a multidrug-resistant cell line that overexpresses P-glycoprotein, the potency of compounds II and IATwas maintained. Both compounds had favorable drug-like properties, and acceptable oral bioavailability (21–50%) in mice, rats, and dogs. Tumor growth inhibition of greater than 100% was achieved when immunodeficient mice with rapidly growing paclitaxel-resistant prostate cancer cells were treated orally at doses of 3–30 mg/kg of II or IAT.
These studies highlight the potent and broad anticancer activity of two orally bioavailable compounds, offering significant pharmacologic advantage over existing drugs of this class for multidrug resistant or taxane-refractory cancers.
PMCID: PMC3646298  PMID: 22760659
paclitaxel resistant cancer; P-glycoprotein; pharmacokinetics; tubulin; xenograft
5.  Novel Tubulin Polymerization Inhibitors Overcome Multidrug Resistance and Reduce Melanoma Lung Metastasis 
Pharmaceutical research  2012;29(11):3040-3052.
To evaluate abilities of 2-aryl-4-benzoyl-imidazoles (ABI) to overcome multidrug resistance (MDR), define their cellular target, and assess in vivo antimelanoma efficacy.
MDR cell lines that overexpressed P-glycoprotein, MDR-associated proteins, and breast cancer resistance protein were used to evaluate ABI ability to overcome MDR. Cell cycle analysis, molecular modeling, and microtubule imaging were used to define ABI cellular target. SHO mice bearing A375 human melanoma xenograft were used to evaluate ABI in vivo antitumor activity. B16-F10/C57BL mouse melanoma lung metastasis model was used to test ABI efficacy to inhibit tumor lung metastasis.
ABIs showed similar potency to MDR cells compared to matching parent cells. ABIs were identified to target tubulin on the colchicine binding site. After 31 days of treatment, ABI-288 dosed at 25 mg/kg inhibited melanoma tumor growth by 69%; dacarbazine at 60 mg/kg inhibited growth by 52%. ABI-274 dosed at 25 mg/kg showed better lung metastasis inhibition than dacarbazine at 60 mg/kg.
This new class of antimitotic compounds can overcome several clinically important drug resistant mechanisms in vitro and are effective in inhibiting melanoma lung metastasis in vivo, supporting their further development.
PMCID: PMC3659804  PMID: 22410804
2-aryl-4-benzoyl-imidazoles (ABI); antimelanoma; melanoma lung metastasis; multidrug resistance; tubulin polymerization inhibitor
6.  Discovery of novel 2-aryl-4-benzoyl-imidazole (ABI–III) analogues targeting tubulin polymerization as antiproliferative agents 
Journal of medicinal chemistry  2012;55(16):7285-7289.
Novel ABI–III compounds were designed and synthesized based on our previously reported ABI-I and ABI–II analogs. ABI–III compounds are highly potent against a panel of melanoma and prostate cancer cell lines, with the best compound having an average IC50 value of 3.8 nM. They are not substrate of Pgp and thus may effectively overcome Pgp mediated multidrug resistance. ABI–III analogs maintain their mechanisms of action by inhibition of tubulin polymerization.
PMCID: PMC3426659  PMID: 22783954
Melanoma; prostate cancer; multidrug resistance; tubulin polymerization inhibitor; antiproliferative activity
7.  Inhibitors of Tubulin Assembly Identified through Screening a Compound Library 
Chemical biology & drug design  2008;72(6):513-524.
Tubulin is the proposed target for drugs against cancer and helminths and is also a validated target in kinetoplastid parasites. With the aim of identifying new lead compounds against Leishmania sp., tubulin isolated from L. tarentolae was used to screen a 10 000 compound library. One compound, Chembridge No. 7992831 (5), displayed an IC50 of 13 μm against Leishmania tubulin in an in vitro assembly assay and showed a greater than threefold selectivity over mammalian tubulin. Another compound, Chembridge No. 9067250 (8), exhibited good activity against mammalian tubulin (IC50 = 5.0 μm). This compound was also toxic to several cancer cell lines with IC50 values in the region of 1 μM. Subsequent testing of analogues of 8 contained within the library identified two compounds with greater potency against mammalian tubulin (IC50 values of 1.1 and 2.8 μM). The more potent antitubulin agent also showed promising activity against cancer cell lines in vitro, with IC50 values ranging from 0.18 to 0.73 μM.
PMCID: PMC3677961  PMID: 19090918
Tubulin; screen; library; Leishmania
8.  Synthesis and antiproliferative activity of novel 2-aryl-4-benzoyl-imidazole derivatives targeting tubulin polymerization 
Bioorganic & medicinal chemistry  2011;19(16):4782-4795.
We previously reported the discovery of 2-aryl-4-benzoyl-imidazoles (ABI-I) as potent antiproliferative agents for melanoma. To further understand the structural requirements for the potency of ABI analogs, gain insight in the structure-activity relationships (SAR), and investigate metabolic stability for these compounds, we report extensive SAR studies on the ABI-I scaffold. Compared with the previous set of ABI-I analogs, the newly synthesized ABI-II analogs have lower potency in general, but some of the new analogs have comparable potency to the most active compounds in the previous set when tested in two melanoma and four prostate cancer cell lines. These SAR studies indicated that the antiproliferative activity was very sensitive to subtle changes in the ligand. Tested compounds 3ab and 8a are equally active against highly paclitaxel resistant cancer cell lines and their parental cell lines, indicating that drugs developed based on ABI-I analogs may have therapeutic advantages over paclitaxel in treating resistant tumors. Metabolic stability studies of compound 3ab revealed that N-methyl imidazole failed to extend stability as literature reported because de-methylation was found as the major metabolic pathway in rat and mouse liver microsomes. However, this sheds light on the possibility for many modifications on imidazole ring for further lead optimization since the modification on imidazole, such as compound 3ab, did not impact the potency.
PMCID: PMC3152597  PMID: 21775150
9.  Biological Activity of 4-Substituted Methoxybenzoyl-Aryl-Thiazole (SMART): An Active Microtubule Inhibitor 
Cancer research  2010;71(1):216-224.
Formation of microtubules is a dynamic process that involves polymerization and depolymerization of αβ-tubulin heterodimers. Drugs that enhance or inhibit tubulin polymerization can destroy this dynamic process, arresting cells in the G2/M phase of the cell cycle. Although drugs that target tubulin generally demonstrate cytotoxic potency in the sub-nanomolar range, resistance due to drug efflux is a common phenomenon among the antitubulin agents. We recently reported a class of 4-Substituted Methoxybenzoyl-Aryl-Thiazoles (SMART) that exhibited great in vitro potency and broad spectrum cellular cytotoxicity. Evaluation of the in vitro and in vivo anti-cancer activities of three SMART compounds, SMART-H (H), SMART-F (F) and SMART-OH (OH) with varying substituents at the 4-position of aryl ring, demonstrated that they bind potently to the colchicine binding site in tubulin, inhibit tubulin polymerization, arrest cancer cells in G2/M phase of the cell cycle, and induce their apoptosis.
The SMART compounds also equi-potently inhibit the growth of parental and MDR-over-expressing cells in vitro, indicating that they can overcome multidrug resistance. In vivo anti-tumor efficacy studies in human prostate (PC-3) and melanoma (A375) cancer xenograft models demonstrated that SMART-H and SMART-F treatments resulted in %T/C values ranging from 4–30%. In addition, in vivo SMART-H treatment for 21 days at the higher dose (15 mg/kg) failed to produce any apparent neurotoxicity. These studies provide the first in vivo evidence and proof-of-concept that SMART compounds are similarly efficacious to currently FDA approved antitubulin drugs for cancer treatment, but they can circumvent P-glycoprotein-mediated drug resistance.
PMCID: PMC3039446  PMID: 21084278
tubulin; P-glycoprotein; pharmacokinetics; xenograft
10.  Flavopiridol Pharmacogenetics: Clinical and Functional Evidence for the Role of SLCO1B1/OATP1B1 in Flavopiridol Disposition 
PLoS ONE  2010;5(11):e13792.
Flavopiridol is a cyclin-dependent kinase inhibitor in phase II clinical development for treatment of various forms of cancer. When administered with a pharmacokinetically (PK)-directed dosing schedule, flavopiridol exhibited striking activity in patients with refractory chronic lymphocytic leukemia. This study aimed to evaluate pharmacogenetic factors associated with inter-individual variability in pharmacokinetics and outcomes associated with flavopiridol therapy.
Methodology/Principal Findings
Thirty-five patients who received single-agent flavopiridol via the PK-directed schedule were genotyped for 189 polymorphisms in genes encoding 56 drug metabolizing enzymes and transporters. Genotypes were evaluated in univariate and multivariate analyses as covariates in a population PK model. Transport of flavopiridol and its glucuronide metabolite was evaluated in uptake assays in HEK-293 and MDCK-II cells transiently transfected with SLCO1B1. Polymorphisms in ABCC2, ABCG2, UGT1A1, UGT1A9, and SLCO1B1 were found to significantly correlate with flavopiridol PK in univariate analysis. Transport assay results indicated both flavopiridol and flavopiridol-glucuronide are substrates of the SLCO1B1/OATP1B1 transporter. Covariates incorporated into the final population PK model included bilirubin, SLCO1B1 rs11045819 and ABCC2 rs8187710. Associations were also observed between genotype and response. To validate these findings, a second set of data with 51 patients was evaluated, and overall trends for associations between PK and PGx were found to be consistent.
Polymorphisms in transport genes were found to be associated with flavopiridol disposition and outcomes. Observed clinical associations with SLCO1B1 were functionally validated indicating for the first time its relevance as a transporter of flavopiridol and its glucuronide metabolite. A second 51-patient dataset indicated similar trends between genotype in the SLCO1B1 and other candidate genes, thus providing support for these findings. Further study in larger patient populations will be necessary to fully characterize and validate the clinical impact of polymorphisms in SLCO1B1 and other transporter and metabolizing enzyme genes on outcomes from flavopiridol therapy.
PMCID: PMC2967470  PMID: 21072184

Results 1-10 (10)