Genotoxicity of the cancer chemopreventive drug candidates CP-31398, SHetA2, and phospho-ibuprofen

Prevention of hypertension-induced renal vascular dysfunction through a p66Shc-targeted mechanism

Renal microvascular injury occurs in most patients with hypertension-induced nephropathy (HN). We have shown that overexpression of adaptor protein p66Shc is implicated in the loss of renal microvascular reactivity in hypertensive rats. Since sulfur heteroarotinoid A2 (SHetA2) modulates p66Shc, we tested whether SHetA2 would restore renal microvascular reactivity and mitigate kidney injury in a rat HN model. Dahl salt sensitive (SS) and p66Shc knockout (p66Shc-KO) rats were used in a well-established rat model of HN, characterized by severe renal vascular dysfunction. SHetA2 was either added acutely to isolated rat afferent arterioles or chronically administrated to rats during HN development. The ability of SHetA2 treatment to restore afferent arteriolar contraction in response to increased perfusion pressure or ATP was evaluated using the perfused juxtamedullary nephron preparation. The progression of renal damage was evaluated by measuring urinary protein excretion and conducting analysis of glomerular injury. Comparison of renal microvascular responses to perfusion pressure in p66Shc-KO rats and parental SS rats, in the presence and absence of acute preincubation with SHetA2, revealed a dose-dependent ability of SHetA2 to restore renal microvascular reactivity in SS rats with little effect upon p66Shc knockouts. Moreover, chronic treatment with SHetA2 prevented loss of renal microvascular responses and decline in renal function. SHetA2 was more potent and effective in males compared with females. Targeting p66Shc with SHetA2 diminishes renal damage and restores renal afferent arteriolar reactivity caused by hypertension. These results justify further translation of these findings to develop SHetA2 for prevention and treatment of hypertension-induced kidney damage.NEW & NOTEWORTHY Acute preincubation with modulator of p66Shc signaling sulfur heteroarotinoid A2 (SHetA2) revealed dose-dependent ability of SHetA2 to restore renal microvascular reactivity in rats with hypertension-induced nephropathy. Moreover, chronic treatment with SHetA2 prevented loss of renal microvascular responses and decline in renal function. Thus, targeting p66Shc with SHetA2 diminishes renal damage and restores renal afferent arteriolar reactivity caused by hypertension.

Targeting HSP70-E7 Interaction With SHetA2: A Novel Therapeutic Strategy for Cervical Cancer

Cervical cancer is predominantly driven by persistent infections with high-risk human papillomavirus and the continuous activity of its E6 and E7 oncoproteins. This study explored the role of heat shock proteins 70 kDa (HSP70s) in enhancing the function of these oncoproteins and examined the impact of SHetA2, an investigational new drug, on this interaction. We found that HSP70 specifically binds to E7, but not E6, protein and that SHetA2 disrupts this binding. This disruption led to a significant reduction in E6 and E7 mRNA and E7 protein levels, while effects on E6 protein levels were minimal. SHetA2 treatment also resulted in altered levels of cell cycle regulatory proteins, reduced cell cycle progression, and decreased metabolic viability in cervical cancer cell lines and xenograft models. These findings support the potential of SHetA2 to impair cervical cancer progression by targeting HSP70/E7 interactions, highlighting its promise as a therapeutic strategy for treating cervical cancer.

Manipulation of metabolic responses enhances SHetA2 efficacy without toxicity in cervical cancer cell lines and xenografts

OBJECTIVE

The high frequency of cervical cancer recurrence after primary therapy necessitates alternative treatments. High-risk human papillomavirus (HR-HPV) causes cervical cancer and it's continued presence supports elevated metabolism, proliferation and survival of cancer cells. The low-to-no toxicity new investigational drug, SHetA2, counteracts high-risk human papillomavirus (HR-HPV) effects on cell proliferation and survival in cervical cancer cells and xenograft tumors by disrupting heat shock protein 70 chaperone protection of oncogenic proteins. Our objective was to study the involvement of metabolism in SHetA2 effects on cervical cancer cells and tumors.

METHODS

SHetA2-mediated proteomic and metabolic effects were measured in HR-HPV-positive CaSKi and SiHa and HR-HPV-negative C-33 A cervical cancer cell lines. Combined treatment with 2-deoxyglucose (2-DG) was evaluated in cell culture and SiHa xenografts.

RESULTS

SHetA2 inhibited oxidative phosphorylation (OxPhos) and altered levels of proteins involved in metabolism, protein synthesis, and DNA replication and repair. Cervical cancer cells responded by elevating glycolysis. Inhibition of the glycolytic responses using galactose media or 2-DG increased SHetA2 sensitivity of two HR-HPV-positive, but not an HR-HPV-negative cervical cancer cell line. Interaction of 2-DG and SHetA2 was synergistic in HR-HPV positive cell lines in association with augmentation of SHetA2 ATP reduction, but not SHetA2 DNA damage induction. These results were verified in a SiHa xenograft tumor model without evidence of toxicity.

CONCLUSIONS

Compensatory glycolysis counteracts OxPhos inhibition in SHetA2-treated HR-HPV-positive cervical cancer cell lines. Prevention of compensatory glycolysis with 2-DG or another glycolysis inhibitor has the potential to improve SHetA2 therapy without toxicity.

Pharmacodynamics of Cyclin D1 Degradation in Ovarian Cancer Xenografts with Repeated Oral SHetA2 Dosing

SHetA2 is a promising, orally active small molecule with anticancer properties that target heat shock proteins. In this study, we aimed to investigate the pharmacodynamic (PD) effects of SHetA2 using preclinical in vitro and in vivo models of ovarian cancer and establish a physiologically based pharmacokinetic (PBPK)/PD model to describe their relationships with SHetA2 concentrations in mice. We found that daily oral administration of 60 mg/kg SHetA2 for 7 days resulted in consistent plasma PK and tissue distribution, achieving tumor drug concentrations required for growth inhibition in ovarian cancer cell lines. SHetA2 effectively induced cyclin D1 degradation in cancer cells in a dose-dependent manner, with up to 70% reduction observed and an IC50 of 4~5 µM. We identified cyclin D1 as a potential PD marker for SHetA2, based on a well-correlated time profile with SHetA2 PK. Additionally, we examined circulating levels of ccK18 as a non-invasive PD marker for SHetA2-induced apoptotic activity and found it unsuitable due to high variability. Using a PBPK/PD model, we depicted SHetA2 levels and their promoting effects on cyclin D1 degradation in tumors following multiple oral doses. The model suggested that twice-daily dosing regimens would be effective for sustained reduction in cyclin D1 protein. Our study provides valuable insights into the PK/PD of SHetA2, facilitating future clinical trial designs and dosing schedules.

Distinct mechanism of cervical cancer cell death caused by the investigational new drug SHetA2

Drug-targetable vulnerabilities of cancer cells include their dependence on heat shock proteins (HSPs) to support elevated mitochondrial metabolism and counteract cell death factors. The investigational new drug SHetA2 targets these vulnerabilities in ovarian and endometrial cancer cells by disrupting complexes of the mortalin HSP with its client proteins (mitochondrial support proteins, metabolic enzymes, p53) leading to mitochondrial leakage of cytochrome c and apoptosis-inducing factor (AIF), and caspase-dependent apoptosis. Our objective was to evaluate the roles of mitochondrial damage and another SHetA2-target HSP protein, cytoplasmic heat shock cognate 70 (hsc70), in the mechanism of SHetA2 killing of cervical cancer cells. Cervical cancer cells responded to SHetA2 with excessive mitophagy that did not deter AIF leakage into the cytoplasm. Then, hsc70 was unable to prevent cytoplasmic AIF nuclear translocation and promotion of DNA damage and cell death, because SHetA2 disrupted hsc70/AIF complexes. The Cancer Genome Atlas analysis found that overexpression of hsc70, but not mortalin, was associated with worse cervical cancer patient survival. Use of specific inhibitors documented that AIF and mitophagy, but not caspases, contributed to the mechanism of SHetA2-induced cell death in cervical cancer cells. As validation, excessive mitophagy and lack of caspase activation were observed in SHetA2-inhibited xenograft tumors.

SHetA2 Attack on Mortalin and Colleagues in Cancer Therapy and Prevention

Heat Shock Proteins of the 70-kDa family (HSP70s) do not cause cancer by themselves, but instead protect cells as they transform into cancer. These molecular chaperones bind numerous client proteins and utilize ATP hydrolysis to facilitate proper protein folding, formation of functional complexes and cellular localizations, or degradation of irreparably damaged proteins. Their transient upregulation by stressful situations avoids induction of programmed cell death. Continued upregulation of the mortalin, heat shock cognate (hsc70) and glucose regulated protein 78 (Grp78) support cancer development and progression by supporting pro-proliferative and metabolic functions and repressing pro-death functions of oncoproteins and tumor suppressor proteins. This review describes the discovery and development of a lead anti-cancer compound, sulfur heteroarotinoid A2 (SHetA2, NSC726189), which was originally developed to bind retinoic acid receptors, but was subsequently found to work independently of these receptors. The discovery and validation of mortalin, hsc70 and Grp78 as SHetA2 target proteins is summarized. The documented and hypothesized roles of these HSP70 proteins and their clients in the mechanism of SHetA2 inhibition of cancer without toxicity are discussed. Use of this mechanistic data to evaluate drug action in a cancer clinical trial and develop synergistic drug combinations is explained. Knowledge needed to optimize SHetA2 analogs for use in cancer therapy and prevention is proposed as future directions.

Utility and Mechanism of SHetA2 and Paclitaxel for Treatment of Endometrial Cancer

Simple Summary

Incidence and death rates for endometrial cancer are steadily rising world-wide. Endometrial cancer patients at high risk for recurrence are treated with chemotherapy, which causes significant toxicity. Molecularly targeted drugs have been found to cause less toxicity than chemotherapy. We studied a low-toxicity drug, called SHetA2, which targets three heat shock A proteins that are highly mutated in endometrial cancers. Our results demonstrated that SHetA2 inhibits endometrial cancer cells and tumors, and enhances therapeutic effects of paclitaxel without increasing toxicity. This information supports development of clinical trials to test if combining SHetA2 with paclitaxel can increase the paclitaxel therapeutic effect without increasing toxicity, or allows a lowered paclitaxel dose to achieve the same level of therapeutic effect, but with reduced toxicity. Our new knowledge about how SHetA2 works can be translated into development of biomarkers to predict with patients would most likely benefit from SHetA2-based therapy.

Abstract

Endometrial cancer patients with advanced disease or high recurrence risk are treated with chemotherapy. Our objective was to evaluate the utility and mechanism of a novel drug, SHetA2, alone and in combination with paclitaxel, in endometrial cancer. SHetA2 targets the HSPA chaperone proteins, Grp78, hsc70, and mortalin, which have high mutation rates in endometrial cancer. SHetA2 effects on cancerous phenotypes, mitochondria, metabolism, protein expression, mortalin/client protein complexes, and cell death were evaluated in AN3CA, Hec13b, and Ishikawa endometrial cancer cell lines, and on growth of Ishikawa xenografts. In all three cell lines, SHetA2 inhibited anchorage-independent growth, migration, invasion, and ATP production, and induced G1 cell cycle arrest, mitochondrial damage, and caspase- and apoptosis inducing factor (AIF)-mediated apoptosis. These effects were associated with altered levels of proteins involved in cell cycle regulation, mitochondrial function, protein synthesis, endoplasmic reticulum stress, and metabolism; disruption of mortalin complexes with mitochondrial and metabolism proteins; and inhibition of oxidative phosphorylation and glycolysis. SHetA2 and paclitaxel exhibited synergistic combination indices in all cell lines and exerted greater xenograft tumor growth inhibition than either drug alone. SHetA2 is active against endometrial cancer cell lines in culture and in vivo and acts synergistically with paclitaxel.

Complementary Targeting of Rb Phosphorylation and Growth in Cervical Cancer Cell Cultures and a Xenograft Mouse Model by SHetA2 and Palbociclib

Cervical cancer is caused by high-risk human papillomavirus (HPV) types and treated with conventional chemotherapy with surgery and/or radiation. HPV E6 and E7 proteins increase phosphorylation of retinoblastoma (Rb) by cyclin D1/cyclin dependent kinase (CDK)4/6 complexes. We hypothesized that cyclin D1 degradation by the SHetA2 drug in combination with palbociclib inhibition of CDK4/6 activity synergistically reduces phosphorylated Rb (phospho-Rb) and inhibits cervical cancer growth. The effects of these drugs, alone, and in combination, were evaluated in SiHa and CaSki HPV-positive and C33A HPV-negative cervical cancer cell lines using cell culture, western blots and ELISA, and in a SiHa xenograft model. Endpoints were compared by isobolograms, ANOVA, and Chi-Square. In all cell lines, combination indexes documented synergistic interaction of SHetA2 and palbociclib in association SHetA2 reduction of cyclin D1 and phospho-Rb, palbociclib reduction of phospho-Rb, and enhanced phospho-Rb reduction upon drug combination. Both drugs significantly reduced phospho-Rb and growth of SiHa xenograft tumors as single agents and acted additively when combined, with no evidence of toxicity. Dilated CD31-negative blood vessels adjacent to, or within, areas of necrosis and apoptosis were observed in all drug-treated tumors. These results justify development of the SHetA2 and palbociclib combination for targeting phospho-Rb in cervical cancer treatment.

Vaginal Suppositories Containing SHetA2 to Treat Cervical Dysplasia: Pharmacokinetics of Daily Doses and Preliminary Safety Profile

SHetA2 is a new drug with potential to treat cervical dysplasia, but only 0.02% of the dose is absorbed into the cervix after oral administration. By contrast, 23.9% of the dose is absorbed into the cervix after vaginal administration. This study determines the pharmacokinetic and pharmacodynamic parameters after daily vaginal doses of SHetA2 in suppositories and assesses its safety. Daily dosed mice maintained therapeutic concentrations of SHetA2 in the cervix for 65 h. The steady-state area under the curve concentration versus time (AUC_cervix) after the last dose was similar to that after a single dose indicating that there was no drug accumulation in the cervix. By contrast, the maximum drug concentration (C_max-cervix) was smaller in the daily dosed group (52.19 μg/g) than after a single dose (121.84 μg/g), whereas the half-life (t_1/2-cervix) was also shorter in the daily dosed group (9.94 h) than after a single dose (23.32 h). Notably, daily vaginal doses of SHetA2 reduced the levels of cyclin D1 (the pharmacodynamic endpoint) to a larger extent (∼45%) than after the administration of a single dose (∼26%). No adverse effects were observed in the mice for the duration of the study; thus, daily vaginal doses of SHetA2 appear to be safe.

Physiologically Based Pharmacokinetic Modeling and Tissue Distribution Characteristics of SHetA2 in Tumor-Bearing Mice

The orally available novel small molecule SHetA2 is the lead sulfur-containing heteroarotinoid that selectively inhibits cancer cells over normal cells, and is currently under clinical development for anticancer treatment and cancer prevention. The objective of this study was to assess and characterize the tissue distribution of SHetA2 in tumor-bearing mice by developing a physiologically based pharmacokinetic (PBPK) model. An orthotopic SKOV3 ovarian cancer xenograft mouse model was used to most accurately mimic the ovarian cancer tumor microenvironment in the peritoneal cavity. SHetA2 concentrations in plasma and 14 different tissues were measured at various time points after a single intravenous dose of 10 mg/kg and oral dose of 60 mg/kg, and these data were used to develop a whole-body PBPK model. SHetA2 exhibited a multi-exponential plasma concentration decline with an elimination half-life of 4.5 h. Rapid and extensive tissue distribution, which was best described by a perfusion rate-limited model, was observed with the tissue-to-plasma partition coefficients (k_p = 1.4-21.2). The PBPK modeling estimated the systemic clearance (76.4 mL/h) from circulation as a main elimination pathway of SHetA2. It also indicated that the amount absorbed into intestine was the major determining factor for the oral bioavailability (22.3%), while the first-pass loss from liver and intestine contributed minimally (< 1%). Our results provide an insight into SHetA2 tissue distribution characteristics. The developed PBPK model can be used to predict the drug exposure at tumors or local sites of action for different dosing regimens and scaled up to humans to correlate with efficacy.

Novel ovarian cancer maintenance therapy targeted at mortalin and mutant p53

Current ovarian cancer maintenance therapy is limited by toxicity and no proven impact on overall survival. To study a maintenance strategy targeted at missense mutant p53, we hypothesized that the release of mutant p53 from mortalin inhibition by the SHetA2 drug combined with reactivation of mutant p53 with the PRIMA-1^MET drug inhibits growth and tumor establishment synergistically in a mutant-p53 dependent manner. The Cancer Genome Atlas (TCGA) data and serous ovarian tumors were evaluated for TP53 and HSPA9/mortalin status. SHetA2 and PRIMA-1^MET were tested in ovarian cancer cell lines and fallopian tube secretory epithelial cells using isobolograms, fluorescent cytometry, Western blots and ELISAs. Drugs were administered to mice after peritoneal injection of MESOV mutant p53 ovarian cancer cells and prior to tumor establishment, which was evaluated by logistic regression. Fifty-eight percent of TP53 mutations were missense and there were no mortalin mutations in TCGA high-grade serous ovarian cancers. Mortalin levels were sequentially increased in serous benign, borderline and carcinoma tumors. SHetA2 caused p53 nuclear and mitochondrial accumulation in cancer, but not in healthy, cells. Endogenous or exogenous mutant p53 increased SHetA2 resistance. PRIMA-1^MET decreased this resistance and interacted synergistically with SHetA2 in mutant and wild type p53-expressing cell lines in association with elevated reactive oxygen species/ATP ratios. Tumor-free rates in animals were 0% (controls), 25% (PRIMA1^MET ), 42% (SHetA2) and 67% (combination). SHetA2 (p = 0.004) and PRIMA1^MET (p = 0.048) functioned additively in preventing tumor development with no observed toxicity. These results justify the development of SHetA2 and PRIMA-1^MET alone and in combination for ovarian cancer maintenance therapy.

Development and validation of a reverse phase HPLC method for SHetA2, a novel anti-cancer drug, in mouse biological samples

SHetA2 is a flexible heteroarotinoid that has the potential to prevent and treat lung, ovarian and cervical cancer without significant toxicity. A simple and reliable high performance liquid chromatographic (HPLC) method was developed to determine SHetA2 concentrations in the lungs, reproductive organs and plasma of mice. SHetA2 was extracted from these biological matrices by solid phase and liquid-liquid extraction in the presence of 4% H₃PO₄ and acetonitrile followed by filtration through a Captiva^® filtration plate. Drug concentrations in the filtrates were quantified by a Waters HPLC Alliance system coupled with XBridge^® C₁₈ column, guard column and UV detection at 361 nm. The mobile phase consisted of methanol and 0.25 N sodium acetate buffer (80:20, v/v) at pH: 3. SHetA2 was eluted after 5.35 and 6.14 min for tissues and plasma, respectively. Recovery of SHetA2 from biological samples was more than 95% of the spiked amount in tissues and more than 80% of the spiked amount in plasma. The limit of detection (LOD) was 0.005 μg/mL and the limit of quantitation (LOQ) was 0.025 μg/mL, which were 280 and 56 times lower than the predicted therapeutic concentration of SHetA2, respectively. The method was suitable to quantify SHetA2 concentrations in biological matrices from animal studies administering the drug by the vaginal, pulmonary and oral routes that had the purpose of determining the pharmacokinetic parameters of drug disposition. The HPLC method developed meets the ICH Harmonized Tripartite Guideline of a reliable, sensitive, reproducible and accurate method to be used in the determination of drug concentrations in biological samples.

Novel flexible heteroarotinoid, SL-1-39, inhibits HER2-positive breast cancer cell proliferation by promoting lysosomal degradation of HER2

SL-1-39 [1-(4-chloro-3-methylphenyl)-3-(4-nitrophenyl)thiourea] is a new flexible heteroarotinoid (Flex-Het) analog derived from the parental compound, SHetA2, previously shown to inhibit cell growth across multiple cancer types. The current study aims to determine growth inhibitory effects of SL-1-39 across the different subtypes of breast cancer cells and delineate its molecular mechanism. Our results demonstrate that while SL-1-39 blocks cell proliferation of all breast cancer subtypes tested, it has the highest efficacy against HER2+ breast cancer cells. Molecular analyses suggest that SL-1-39 prevents S phase progression of HER2+ breast cancer cells (SKBR3 and MDA-MB-453), which is consistent with reduced expression of key cell-cycle regulators at both the protein and transcriptional levels. SL-1-39 treatment also decreases the protein levels of HER2 and pHER2 as well as its downstream effectors, pMAPK and pAKT. Reduction of HER2 and pHER2 at the protein level is attributed to increased lysosomal degradation of total HER2 levels. This is the first study to show that a flexible heteroarotinoid analog modulates the HER2 signaling pathway through lysosomal degradation, and thus further warrants the development of SL-1-39 as a therapeutic option for HER2+ breast cancer.

Pharmacokinetics and Pharmacodynamics of Escalating Doses of SHetA2 After Vaginal Administration to Mice

SHetA2 is a novel compound with strong potential to treat cervical dysplasia, but its low aqueous solubility limits its oral bioavailability. A vaginal suppository achieved SHetA2 cervix concentrations that were severalfold above the predicted therapeutic levels. Thus, we aimed at determining the minimum dose that would achieve SHetA2 therapeutic levels while reducing cyclin D1 levels, the pharmacodynamic end point. The disposition of SHetA2 after vaginal administration of escalating SHetA2 doses and the corresponding reduction in cyclin D1 levels was compared to that after the conventional oral treatment. Vaginal administration of a 15-mg/kg dose achieved an area under the cervix concentration versus time curve (AUCcervix) that was ∼120 times larger than that after a 60 mg/kg administered orally. AUCcervix and Cmax-cervix did not increase proportionally with respect to the dose, with the 30-mg/kg dose resulting in higher AUCcervix and Cmax-cervix (1368.53 μg.mL/h and 155.38 μg/g, respectively) compared to the 15 mg/kg (334.98 μg.mL/h and 121.78 μg/g, respectively) or 60 mg/kg (1178.55 μg.mL/h and 410.38 μg/g, respectively). Likewise, the 30-mg/kg dose caused a larger reduction in cyclin D1 levels than the other doses. Thus, the 30-mg/kg dose was selected for future efficacy studies in a mouse model of cervical neoplasia.

Pharmacokinetics and interspecies scaling of a novel, orally-bioavailable anti-cancer drug, SHetA2

SHetA2 is a small molecule drug with promising cancer prevention and therapeutic activity and a high preclinical safety profile. The study objectives were to perform interspecies scaling and pharmacokinetic (PK) modeling of SHetA2 for human PK prediction. The PK data obtained from mice, rats, and dogs after intravenous and oral doses were used for simultaneous fitting to PK models. The disposition of SHetA2 was best described by a two-compartment model. The absorption kinetics was well characterized with a first-order absorption model for mice and rats, and a gastrointestinal transit model for dogs. Oral administration of SHetA2 showed a relatively fast absorption in mice, prolonged absorption (i.e., flip-flop kinetics) toward high doses in rats, and an early peak followed by a secondary peak at high doses in dogs. The oral bioavailability was 17.7-19.5% at 20-60 mg/kg doses in mice, <1.6% at 100-2000 mg/kg in rats, and 11.2% at 100 mg/kg decreasing to 3.45% at 400 mg/kg and 1.11% at 1500 mg/kg in dogs. The disposition parameters were well correlated with the body weight for all species using the allometric equation, which predicted values of CL (17.3 L/h), V1 (36.2 L), V2 (68.5 L) and CLD (15.2 L/h) for a 70-kg human. The oral absorption rate and bioavailability of SHetA2 was highly dependent on species, doses, formulations, and possibly other factors. The limited bioavailability at high doses was taken into consideration for the suggested first-in-human dose, which was much lower than the dose estimated based on toxicology studies. In summary, the present study provided the PK model for SHetA2 that depicted the disposition and absorption kinetics in preclinical species, and computational tools for human PK prediction.

Development of a dietary formulation of the SHetA2 chemoprevention drug for mice

Development of cancer chemoprevention compounds requires enhanced consideration for toxicity and route of administration because the target population is healthy. The small molecule drug, SHetA2 (NSC 726189), exhibited in vivo chemoprevention activity and lack of toxicity when administered by oral gavage. Our objective was to determine if a dietary formulation of SHetA2 could achieve effective tissue drug levels without toxicity. C57bl/6 J mice were monitored on modified American Institute of Nutrition (AIN)76A diet mixed with SHetA2 in a 3:1 ratio with Kolliphor HS15, a self-emulsifying drug delivery system (SEDDS) to deliver 37.5, 62.5, 125, 187 or 250 mg SHetA2/kg/day. Blood and tissues were evaluated after 1, 3 and 6 weeks. The 187 mg/kg/day dose was identified as optimal based on achievement of maximum blood and tissue drug levels in the effective micromolar range without evidence of toxicity. The 250 mg/kg/day group exhibited lower drug levels and the highest intestinal drug content suggesting that an upper limit of intestinal absorption had been surpassed. Only this highest dose resulted in liver and kidney function tests that were outside of the normal range, and significant reduction of cyclin D1 protein in normal cervical tissue. SHetA2 reduced cyclin D1 to greater extents in cancer compared to non-cancer cell cultures. Given this differential effect, optimal chemoprevention without toxicity would be expected to occur at doses that reduced cyclin D1 in neoplastic, but not in normal tissues. These findings support further development of SHetA2 as a chemoprevention agent and potential food additive.

Novel flexible heteroarotinoid, SL-1-18, promotes ERα degradation to inhibit breast cancer cell growth

SL-1-18 (1-(chrysen-6-yl)-3-(4-nitrophenyl)thiourea) is new flexible heteroarotinoid (Flex-Het) analog derived from the parent compound, SHetA2, and our previous study showed comparable activity to SHetA2 in terms of inhibiting ER+ breast cancer cell growth. This current study aims to determine the molecular mechanism underlying SL-1-18's effect on breast cancer cell growth. Our results indicate that SL-1-18 inhibits cell proliferation of ER+ breast cancer cells (MCF-7 and T-47D) by preventing cell cycle progression. SL-1-18 treatment correlated positively with decreased expression of key cell-cycle regulators, such as cyclin D1, as well as other ERα-target genes at both the transcript and protein levels. Interestingly, decreased expression of ERα was also observed, with a significant reduction at the protein level within 2 h of SL-1-18 treatment, while the decrease in mRNA occurred at a later time point. ERα degradation was shown to be mediated by the ubiquitination-proteasome pathway. In summary, this is the first study to show that a Flex-Het- SL-1-18- can promote the degradation of ERα via the ubiquitin-proteasome pathway and should be further developed as a therapeutic option for ER+ breast cancer.

Bioanalytical method development and validation of HPLCUV assay for the quantification of SHetA2 in mouse and human plasma: Application to pharmacokinetics study

Background

SHetA2 is an oral anticancer agent being investigated for cancer treatment and prevention. The aim of this study was to develop and validate a simple, cost-effective, and sensitive HPLC-UV method for the quantification of SHetA2 in biological samples and to apply the method to pharmacokinetic studies of the drug.

Methods

Sample preparation for mouse and human plasmas involved liquid-liquid precipitation and extraction using chilled acetonitrile with 2, 3-Diphenylquinoxaline as an internal standard. The separation of SHetA2 and internal standard was achieved via Waters XBridge™ BEH 130 C18 (3.5 μm, 2.1×150 mm) column coupled with a Waters XBridge™ C-18 (3.5 μm, 2.1×10 mm) guard column using 65% v/v acetonitrile: distilled water as a mobile phase in an isocratic mode with a flow rate of 0.18 ml/min. The analytes were eluted at a detection wavelength of 341 nm at a column temperature of 25°C.

Results

The method was validated across a range of 5-1000 ng/ml for SHetA2 in plasma, with a lower limit of quantification of 5 ng/ml. The method showed high recovery in human (79.9-81.8%) and mouse (95.4-109.2%) plasma with no matrix effect. The intra- and inter-day accuracy and precision studies demonstrated that the method was specific, sensitive, and reliable. Stability studies showed that SHetA2 is stable for 20 h postoperatively in the auto sampler, and for six weeks at -80°C in plasma. Repetitive freezing and thawing may be avoided by preparing the aliquots and storing them at -80°C. The developed method was successfully applied to study the plasma pharmacokinetics of SHetA2 in tumor-bearing nude mice after intravenous and oral administration.

Conclusion

A novel method for quantifying SHetA2 in mouse and human plasmas has been validated and is being applied for pharmacokinetic evaluation of SHetA2 in tumor-bearing mice. The developed method will be utilized for the quantification of SHetA2 in clinical studies.

Effects of anti-inflammatory drugs in primary kidney cell culture of a freshwater fish

The non-steroidal anti-inflammatory drugs are emerging contaminants in aquatic ecosystems. This study aimed to evaluate toxic effects of some representative drugs of this pharmaceutical group on primary culture of monocytic lineage of Hoplias malabaricus anterior kidney. The effects of diclofenac, acetaminophen and ibuprofen in cell viability, lipopolysaccharide (LPS)-induced NO production and genotoxicity were evaluated. Cytometry analysis CD11b(+) cells showed 71.5% of stem cells, 19.5% of macrophages and 9% of monocytes. Cell viability was lower in the ficoll compared to percoll separation. LPS-induced NO production by these cells was blocked after treatment with dexamethasone and NG-Methyl-L-Arginine (L-NMMA). Exposure of the cells to diclofenac (0.2-200 ng/mL), acetaminophen (0.025-250 ng/mL) ibuprofen (10-1000 ng/mL) reduced basal NO production and inhibited LPS-induced NO production at all concentrations after 24 h of exposure. Genotoxicity occurred at the highest concentration of diclofenac and at the intermediary concentration of acetaminophen. Genotoxicity was also observed by ibuprofen. In summary, the pharmaceuticals influenced NO production and caused DNA damage in monocytic cells suggesting that these drugs can induce immunosuppression and genotoxicity in fish.

SHetA2 interference with mortalin binding to p66shc and p53 identified using drug-conjugated magnetic microspheres

SHetA2 is a small molecule flexible heteroarotinoid (Flex-Het) with promising cancer prevention and therapeutic activity. Extensive preclinical testing documented lack of SHetA2 toxicity at doses 25 to 150 fold above effective doses. Knowledge of the SHetA2 molecular target(s) that mediate(s) the mechanism of SHetA2 action is critical to appropriate design of clinical trials and improved analogs. The aim of this study was to develop a method to identify SHetA2 binding proteins in cancer cells. A known metabolite of SHetA2 that has a hydroxyl group available for attachment was synthesized and conjugated to a linker for attachment to a magnetic microsphere. SHetA2-conjugated magnetic microspheres and unconjugated magnetic microspheres were separately incubated with aliquots of a whole cell protein extract from the A2780 human ovarian cancer cell line. After washing away non-specifically bound proteins with the protein extraction buffer, SHetA2-binding proteins were eluted with an excess of free SHetA2. In two independent experiments, an SDS gel band of about 72 kDa was present at differential levels in wells of eluent from SHetA2-microspheres in comparison to wells of eluent from unconjugated microspheres. Mass spectrometry analysis of the bands (QStar) and straight eluents (Orbitrap) identified mortalin (HSPA9) to be present in the eluent from SHetA2-microspheres and not in eluent from unconjugated microspheres. Co-immunoprecipitation experiments demonstrated that SHetA2 interfered with mortalin binding to p53 and p66 Src homologous-collagen homologue (p66shc) inside cancer cells. Mortalin and SHetA2 conflictingly regulate the same molecules involved in mitochondria-mediated intrinsic apoptosis. The results validate the power of this protocol for revealing drug targets.

Chemoprevention of colon and small intestinal tumorigenesis in APC(min/+) mice by SHetA2 (NSC721689) without toxicity

The occurrence of intestinal polyps in people at high risk for developing colorectal cancer provides an opportunity to test the efficacy of chemoprevention agents. In this situation of treating otherwise healthy people, the potential for toxicity must be minimal. The small-molecule flexible heteroarotinoid (Flex-Het), called SHetA2, has chemoprevention activity in organotypic cultures in vitro and lack of toxicity at doses capable of inhibiting xenograft tumor growth in vivo. The objective of this study was to evaluate SHetA2 chemoprevention activity and toxicity in the APC(min/+) murine model. Oral administration of SHetA2 at 30 and 60 mg/kg five days per week for 12 weeks significantly reduced development of intestinal polyps by 40% to 60% depending on the dose and sex of the treatment group. Immunohistochemical and Western blot analysis of polyps showed reduced levels of cyclin D1 and proliferating cell nuclear antigen in both SHetA2 treatment groups. Western blot analysis also showed SHetA2 induction of E-cadherin, Bax, and caspase-3 cleavage along with reduction in Bcl-2, COX-2, and VEGF, consistent with SHetA2 regulation of apoptosis, inflammation, and angiogenesis. Neither dose caused weight loss nor gross toxicity in APC(min/+) or wild-type littermates. Magnetic resonance imaging (MRI) of cardiac function showed no evidence of SHetA2 toxicity. SHetA2 did not alter left ventricular wall thickness. In summary, SHetA2 exerts chemoprevention activity without overt or cardiac toxicity in the APC(min/+) model. SHetA2 modulation of biomarkers in colon polyps identifies potential pharmacodynamic endpoints for SHetA2 clinical trials.

Dose-dependent efficacy and safety toxicology of hydroxypyridinonate actinide decorporation agents in rodents: towards a safe and effective human dosing regimen

Two hydroxypyridinone-containing actinide decorporation agents, 3,4,3-LI(1,2-HOPO) and 5-LIO(Me-3,2-HOPO), are being developed for the treatment of internal actinide contamination by chelation therapy. Dose-response efficacy profiles in mice were established for the removal of intravenously injected (238)Pu and (241)Am after parenteral and oral treatment with these chelators. In both cases, presumed efficacious doses promoted substantially greater actinide elimination rates than the currently approved agent, diethylenetriamine-pentaacetic acid, considering two different interspecies scaling methods for the conversion of human doses to equivalent rodent dose levels. In addition, genotoxicity of both ligands was assessed using the Salmonella/ Escherichia coli /microsome plate incorporation test and the Chinese hamster ovary cell chromosome aberration assay, showing that neither ligand is genotoxic, in the presence and absence of metabolic activation. Finally, maximum tolerated dose studies were performed in rats for seven consecutive daily oral administrations with the chelators, confirming the safety of the presumed efficacious doses for 3,4,3-LI(1,2-HOPO) and 5-LIO(Me-3,2-HOPO). The results of these studies add to the growing body of evidence that both decorporation agents have remarkable decorporation efficacy properties and promising safety toxicology profiles. These results are necessary components of the regulatory approval process and will help determine the optimal human dosing regimens for the treatment of internal radionuclide contamination.