Publications by authors named "Charlene M Santos"

6 Publications

  • Page 1 of 1

GSK2801, a BAZ2/BRD9 Bromodomain Inhibitor, Synergizes with BET Inhibitors to Induce Apoptosis in Triple-Negative Breast Cancer.

Mol Cancer Res 2019 07 18;17(7):1503-1518. Epub 2019 Apr 18.

Department of Pharmacology, Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina.

Screening of an inhibitor library targeting kinases and epigenetic regulators identified several molecules having antiproliferative synergy with extraterminal domain (BET) bromodomain (BD) inhibitors (JQ1, OTX015) in triple-negative breast cancer (TNBC). GSK2801, an inhibitor of BAZ2A/B BDs, of the imitation switch chromatin remodeling complexes, and BRD9, of the SWI/SNF complex, demonstrated synergy independent of BRD4 control of P-TEFb-mediated pause-release of RNA polymerase II. GSK2801 or RNAi knockdown of BAZ2A/B with JQ1 selectively displaced BRD2 at promoters/enhancers of ETS-regulated genes. Additional displacement of BRD2 from rDNA in the nucleolus coincided with decreased 45S rRNA, revealing a function of BRD2 in regulating RNA polymerase I transcription. In 2D cultures, enhanced displacement of BRD2 from chromatin by combination drug treatment induced senescence. In spheroid cultures, combination treatment induced cleaved caspase-3 and cleaved PARP characteristic of apoptosis in tumor cells. Thus, GSK2801 blocks BRD2-driven transcription in combination with BET inhibitor and induces apoptosis of TNBC. IMPLICATIONS: Synergistic inhibition of BDs encoded in BAZ2A/B, BRD9, and BET proteins induces apoptosis of TNBC by a combinatorial suppression of ribosomal DNA transcription and ETS-regulated genes.
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http://dx.doi.org/10.1158/1541-7786.MCR-18-1121DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6610760PMC
July 2019

Profiling the relationship between tumor-associated macrophages and pharmacokinetics of liposomal agents in preclinical murine models.

Nanomedicine 2017 02 5;13(2):471-482. Epub 2016 Oct 5.

Division of Pharmacotherapy and Experimental Therapeutics, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; UNC Eshelman School of Pharmacy, Chapel Hill, NC, USA; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. Electronic address:

The mononuclear phagocyte system (MPS) has previously been shown to significantly affect the clearance, tumor delivery, and efficacy of nanoparticles (NPs). This study profiled MPS cell infiltration in murine preclinical tumor models and evaluated how these differences may affect tumor disposition of PEGylated liposomal doxorubicin (PLD) in models sensitive and resistant to PLD. Significant differences in MPS presence existed between tumor types (e.g. ovarian versus endometrial), cell lines within the same tumor type, and location of tumor implantation (i.e. flank versus orthotopic xenografts). Further, the differences in MPS presence of SKOV-3 ovarian and HEC1A endometrial orthotopic cancer models may account for the 2.6-fold greater PLD tumor exposure in SKOV-3, despite similar plasma, liver and spleen exposures. These findings suggest that profiling the presence of MPS cells within and between tumor types is important in tumor model selection and in tumor types and patients likely to respond to NP treatment.
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http://dx.doi.org/10.1016/j.nano.2016.09.015DOI Listing
February 2017

Gulp1 is associated with the pharmacokinetics of PEGylated liposomal doxorubicin (PLD) in inbred mouse strains.

Nanomedicine 2016 10 9;12(7):2007-2017. Epub 2016 Jun 9.

Division of Pharmacotherapy and Experimental Therapeutics, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Carolina Center of Cancer Nanotechnology Excellence, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Center for Pharmacogenomics and Individualized Therapy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. Electronic address:

Nanoparticles (NP) including liposomes are cleared by phagocytes of the mononuclear phagocyte system. High inter-patient variability in pharmacokinetics of PEGylated liposomal doxorubicin (PLD) has been reported. We hypothesized that genetic factors may be associated with the variable disposition of PLD. We evaluated plasma and tissue disposition of doxorubicin after administration of PLD at 6mg/kg IV ×1 via tail vein in 23 different male inbred mouse strains. An approximately 13-fold difference in plasma clearance of PLD was observed among inbred strains. We identified a correlation between strain-specific differences in PLD clearance and genetic variation within a genomic region encoding GULP1 (PTB domain containing engulfment adapter 1) protein using haplotype associated mapping and the efficient mixed-model association algorithms. Our results also show that Gulp1 expression in adipose tissue was associated with PLD disposition in plasma. Our findings suggest that genetic variants may be associated with inter-individual pharmacokinetic differences in NP clearance.
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http://dx.doi.org/10.1016/j.nano.2016.05.019DOI Listing
October 2016

A sensitive high performance liquid chromatography assay for the quantification of doxorubicin associated with DNA in tumor and tissues.

J Pharm Biomed Anal 2016 Feb 28;119:122-9. Epub 2015 Nov 28.

Division of Pharmacotherapy and Experimental Therapeutics, University of North Carolina at Chapel Hill (UNC) Eshelman School of Pharmacy, CB# 7569, Chapel Hill, NC 27599-7569, United States; UNC Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina at Chapel Hill, CB# 7295, Chapel Hill, NC 27599-7295, United States; UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, CB#7355, Chapel Hill, NC 27599-7355, United States; UNC Center for Pharmacogenomics and Individualized Therapy, 120 Mason Farm Road, CB# 7361, Chapel Hill, NC 27599, United States; Carolina Institute For NanoMedicine, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 1079 Genetic Medicine Building, Chapel Hill, NC 27599-7264, United States. Electronic address:

Doxorubicin, a widely used anticancer agent, exhibits antitumor activity against a wide variety of malignancies. The drug exerts its cytotoxic effects by binding to and intercalating within the DNA of tumor and tissue cells. However, current assays are unable to accurately determine the concentration of the intracellular active form of doxorubicin. Thus, the development of a sample processing method and a high-performance liquid chromatography (HPLC) methodology was performed in order to quantify doxorubicin that is associated with DNA in tumors and tissues, which provided an intracellular cytotoxic measure of doxorubicin exposure after administration of small molecule and nanoparticle formulations of doxorubicin. The assay uses daunorubicin as an internal standard; liquid-liquid phase extraction to isolate drug associated with DNA; a Shimadzu HPLC with fluorescence detection equipped with a Phenomenex Luna C18 (2μm, 2.0×100mm) analytical column and a gradient mobile phase of 0.1% formic acid in water or acetonitrile for separation and quantification. The assay has a lower limit of detection (LLOQ) of 10ng/mL and is shown to be linear up to 3000ng/mL. The intra- and inter-day precision of the assay expressed as a coefficient of variation (CV%) ranged from 4.01 to 8.81%. Furthermore, the suitability of this assay for measuring doxorubicin associated with DNA in vivo was demonstrated by using it to quantify the doxorubicin concentration within tumor samples from SKOV3 and HEC1A mice obtained 72h after administration of PEGylated liposomal doxorubicin (Doxil(®); PLD) at 6mg/kg IV x 1. This HPLC assay allows for sensitive intracellular quantification of doxorubicin and will be an important tool for future studies evaluating intracellular pharmacokinetics of doxorubicin and various nanoparticle formulations of doxorubicin.
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http://dx.doi.org/10.1016/j.jpba.2015.11.035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4703077PMC
February 2016

Roles of chemokines CCL2 and CCL5 in the pharmacokinetics of PEGylated liposomal doxorubicin in vivo and in patients with recurrent epithelial ovarian cancer.

Nanomedicine 2015 Oct 17;11(7):1797-807. Epub 2015 Jun 17.

Division of Pharmacotherapy and Experimental Therapeutics, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Carolina Center of Cancer Nanotechnology Excellence, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Center for Pharmacogenomics and Individualized Therapy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. Electronic address:

Unlabelled: Nanoparticles (NPs) are cleared by monocytes and macrophages. Chemokines CCL2 and CCL5 are key mediators for recruitment of these immune cells into tumors and tissues. The purpose of this study was to investigate effects of CCL2 and CCL5 on the pharmacokinetics (PKs) of NPs. Mice deficient in CCL2 or CCL5 demonstrated altered clearance and tissue distribution of polyethylene glycol tagged liposomal doxorubicin (PLD) compared to control mice. The PK studies using mice bearing SKOV3 ovarian cancer xenografts revealed that the presence of tumor cells and higher expression of chemokines were significantly associated with greater clearance of PLD compared to non-tumor bearing mice. Plasma exposure of encapsulated liposomal doxorubicin positively correlated with the total exposure of plasma CCL2 and CCL5 in patients with recurrent epithelial ovarian cancer treated with PLD. These data emphasize that the interplay between PLD and chemokines may have an important role in optimizing PLD therapy.

From The Clinical Editor: The use of nanoparticles as drug delivery carriers is gaining widespread acceptance in the clinical setting. However, the underlying pharmacokinetics of these novel drugs has not really been elucidated. In this interesting article, the authors carried out experiments using mice deficient in CCL2 or CCL5 to study the clearance of liposomal system. They showed the important role the immune system played and would enable better designs of future drug delivery systems.
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http://dx.doi.org/10.1016/j.nano.2015.05.007DOI Listing
October 2015

Effects of tumor microenvironment heterogeneity on nanoparticle disposition and efficacy in breast cancer tumor models.

Clin Cancer Res 2014 Dec 17;20(23):6083-95. Epub 2014 Sep 17.

Division of Pharmacotherapy and Experimental Therapeutics, Eshelman School of Pharmacy, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina. Lineberger Comprehensive Cancer Center, UNC at Chapel Hill, Chapel Hill, North Carolina. Carolina Center of Cancer Nanotechnology Excellence, UNC at Chapel Hill, Chapel Hill, North Carolina. Center for Pharmacogenomics and Individualized Therapy, UNC at Chapel Hill, Chapel Hill, North Carolina.

Purpose: Tumor cells are surrounded by a complex microenvironment. The purpose of our study was to evaluate the role of heterogeneity of the tumor microenvironment in the variability of nanoparticle (NP) delivery and efficacy.

Experimental Designs: C3(1)-T-Antigen genetically engineered mouse model (C3-TAg) and T11/TP53(Null) orthotopic syngeneic murine transplant model (T11) representing human breast tumor subtypes basal-like and claudin-low, respectively, were evaluated. For the pharmacokinetic studies, non-liposomal doxorubicin (NL-doxo) or polyethylene glycol tagged (PEGylated) liposomal doxorubicin (PLD) was administered at 6 mg/kg i.v. x1. Area under the concentration versus time curve (AUC) of doxorubicin was calculated. Macrophages, collagen, and the amount of vasculature were assessed by IHC. Chemokines and cytokines were measured by multiplex immunochemistry. NL-doxo or PLD was administered at 6 mg/kg i.v. weekly x6 in efficacy studies. Analyses of intermediary tumor response and overall survival were performed.

Results: Plasma AUC of NL-doxo and PLD encapsulated and released doxorubicin was similar between two models. However, tumor sum total AUC of PLD was 2-fold greater in C3-TAg compared with T11 (P < 0.05). T11 tumors showed significantly higher expression of CC chemokine ligand (CCL) 2 and VEGF-a, greater vascular quantity, and decreased expression of VEGF-c compared with C3-TAg (P < 0.05). PLD was more efficacious compared with NL-doxo in both models.

Conclusion: The tumor microenvironment and/or tumor cell features of breast cancer affected NP tumor delivery and efficacy, but not the small-molecule drug. Our findings reveal the role of the tumor microenvironment in variability of NP delivery and therapeutic outcomes.
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http://dx.doi.org/10.1158/1078-0432.CCR-14-0493DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4565518PMC
December 2014