Advanced breast cancer, a prevalent and deadly disease, requires innovative approaches for effective diagnosis and treatment. Mesoporous silica nanoparticles (MSNs) have emerged as a versatile platform for theranostics, a field that integrates therapeutic and diagnostic functions within a single system to enable precise, personalized medical care. MSNs are valued for their high surface area, ordered pore structure, excellent biocompatibility, and customizable particle and pore sizes. These features make MSNs ideally suited to theranostics. This review explores the latest advancements in the application of MSNs in breast cancer theranostics. The unique structural and functional properties of MSNs are mediated by their surface modifications, as well as their role in enhancing drug delivery, improving imaging capabilities, and providing targeted therapies. The integration of specific imaging modalities such as magnetic resonance imaging (MRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), computed tomography (CT), photoluminescence (PL), ultrasound (US), photoacoustic imaging (PAI), and fluorescence imaging (FL), with therapeutic agents, including chemotherapeutic drugs and photosensitizers, is discussed in detail. Additional applications for theranostic MSNs are considered, including the development of targeted delivery systems for primary and metastatic diseases to optimize breast cancer treatment. The challenges and prospects of MSN-based theranostic systems, including biocompatibility and clinical translation, are also addressed. In summary, this review highlights the potential of MSNs as a multifunctional delivery platform, enabling personalized treatment strategies for managing breast cancer.

Advanced breast cancer remains a significant oncological challenge, requiring new approaches to improve clinical outcomes. This study investigated an innovative theranostic agent using the MCM-41-NH2-DTPA-Gd3⁺-MIH nanomaterial, which combined MRI imaging for detection and a novel chemotherapy agent (MIH 2.4Bl) for treatment. The nanomaterial was based on the mesoporous silica type, MCM-41, and was optimized for drug delivery via functionalization with amine groups and conjugation with DTPA and complexation with Gd3+. MRI sensitivity was enhanced by using gadolinium-based contrast agents, which are crucial in identifying early neoplastic lesions. MIH 2.4Bl, with its unique mesoionic structure, allows effective interactions with biomolecules that facilitate its intracellular antitumoral activity. Physicochemical characterization confirmed the nanomaterial synthesis and effective drug incorporation, with 15% of MIH 2.4Bl being adsorbed. Drug release assays indicated that approximately 50% was released within 8 h. MRI phantom studies demonstrated the superior imaging capability of the nanomaterial, with a relaxivity significantly higher than that of the commercial agent Magnevist. In vitro cellular cytotoxicity assays, the effectiveness of the nanomaterial in killing MDA-MB-231 breast cancer cells was demonstrated at an EC50 concentration of 12.6 mg/mL compared to an EC50 concentration of 68.9 mg/mL in normal human mammary epithelial cells (HMECs). In vivo, MRI evaluation in a 4T1 syngeneic mouse model confirmed its efficacy as a contrast agent. This study highlighted the theranostic capabilities of MCM-41-NH2-DTPA-Gd3⁺-MIH and its potential to enhance breast cancer management.

Breast cancer is the most frequently diagnosed cancer in women under 60, and the second most diagnosed cancer in women over 60. While significant progress has been made in developing targeted therapies for breast cancer, advanced breast cancer continues to have high mortality, with poor 5-year survival rates. Thus, current therapies are insufficient in treating advanced stages of breast cancer; new treatments are sorely needed to address the complexity of advanced-stage breast cancer. Oncolytic virotherapy has been explored as a therapeutic approach capable of systemic administration, targeting cancer cells, and sparing normal tissue. In particular, oncolytic adenoviruses have been exploited as viral vectors due to their ease of manipulation, production, and demonstrated clinical safety profile. In this study, we engineered an oncolytic adenovirus to target the chemokine receptors CXCR4 and CXCR7. The overexpression of CXCR4 and CXCR7 is implicated in the initiation, survival, progress, and metastasis of breast cancer. Both receptors bind to the ligand, CXCL12 (SDF-1), which has been identified to play a crucial role in the metastasis of breast cancer cells. This study incorporated a T4 fibritin protein fused to CXCL12 into the tail domain of an adenovirus fiber to retarget the vector to the CXCR4 and CXCR7 chemokine receptors. We showed that the modified virus targets and infects CXCR4- and CXCR7-overexpressing breast cancer cells more efficiently than a wild-type control vector. In addition, the substitution of the wild-type fiber and knob with the modified chimeric fiber did not interfere with oncolytic capability. Overall, the results of this study demonstrate the feasibility of retargeting adenovirus vectors to chemokine receptor-positive tumors.

Abstract Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death in women worldwide, accounting for approximately 24% of all new cancer cases and is the leading cause of cancer death in over 100 countries. Thus, breast cancer is one of the most critical public health problems in the world facing women. There is a growing interest in studying the biological activity of mesoionic compounds, which possesses a 5-membered heterocyclic aromatic ring associated with a sextet of electrons. Mesoionic compounds have shown promising potential as anti-cancer agents due to their unique structure and reaction properties. We reported the synthesis of a new 1,3-thiazolium-5-thiolate derivative of a mesoionic compound (MIH 2.4Bl) and the characterization of its selective cytotoxicity on a panel of breast cancer cells lines. The results of our studies suggest a possible induction of apoptotic death through mitochondrial dysfunction by the treatment with MIH 2.4Bl. Based on our previous findings, MIH 2.4Bl is a promising candidate for treating breast cancer. However, a major challenge facing cancer therapy is the selective destruction of malignant cells while sparing normal cells to preserve tissue integrity. The development and use of drug delivery systems is a recognized approach to improve the efficacy of chemotherapy agents. Nonetheless, drug delivery systems have been unexplored in the context of mesoionic compounds. Drug delivery based on nanotechnology has flourished as a platform applicable to cancer therapy. Among various types of nanoparticles, mesoporous silica nanoparticles (MSNs) are more attractive nanomaterials for a broad range of functionality including gene/drug delivery, cancer therapy and bioimaging due to their broad surface area, less toxicity, low density, excellent biocompatibility, higher drug loading capacity, and impressive mechanical and thermal stability. In this preliminary work, we present an improved delivery strategy of a newly developed formulation of MIH 2.4BI compound with MSNs as the delivery agent. Also, physico-chemical characterization of the nanoparticles and cytotoxicity analyses using a panel of breast cancer cell lines were performed. These studies support the potential therapeutic use of MIH 2.4Bl in treating breast cancer. Citation Format: Dipti Debnath, Sami Nazzal, Suchismita Acharya, Helivaldo Diógenes da Silva Souza, Petrônio Filgueiras de Athayde Filho, Rafal Fudala, J Michael Mathis. Using mesoporous silica nanoparticles (MSNs) for delivering the mesoionic compound MIH 2.4Bl in treating breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1232.

Abstract Based on data from the World Health Organization, breast cancer is the most common type of cancer among women, accounting for about 15% of all cancer-related deaths. Thus, new treatment options are urgently needed to decrease this mortality rate. In recent years, mesoionic compounds have shown promising potential as anti-cancer agents due to their unique structure and reaction properties. We recently reported that a 1,3-thiazolium-5-thiolate mesoionic compound (MIH 2.4Bl) inhibited oxidative phosphorylation in the MCF-7 breast cancer cell line compared to normal human mammary epithelial cells. Furthermore, MIH 2.4Bl induced cytotoxicity by activating autography-related proteins (Beclin-1 and ATG5) and cell cycle arrest at the G2/M phase. Based on our previous findings, MIH 2.4BI is a promising candidate for treating breast cancer. However, a major challenge facing cancer therapeutics is tumor delivery in vivo for the selective destruction of malignant cells while sparing normal cells to preserve tissue integrity. The development and use of drug delivery systems is a recognized approach to improve the efficacy of chemotherapy agents. Nonetheless, drug delivery systems have been largely unexplored in the context of mesoionic compounds. Lipoproteins are ideal for carrying transporting lipophilic anti-cancer drugs and imaging agents as they circulate in the bloodstream for an extended period. In addition, the hydrophobic core of lipoprotein particles allows the incorporation of lipophilic components (including a number of anti-cancer agents). Reconstituted high-density lipoprotein (rHDL) mimics the structure and function of endogenous (i.e., human plasma) HDL and thus presents a potentially markedly improved therapeutic strategy for cancer drug delivery. Previous studies from our group have shown that a stable reconstituted synthetic rHDL-drug complex could be prepared by combining paclitaxel and other chemotherapy drugs using the natural lipid and protein components of circulating HDL via a novel procedure. In this preliminary work, we present an improved strategy of using a newly developed formulation of MIH 2.4BI compound with rHDL nanoparticles as the delivery agent. Also, physico-chemical characterization of the nanoparticles and cytotoxicity analyses using a panel of breast cancer cell lines were performed. These studies support the potential therapeutic use of MIH 2.4Bl in treating breast cancer. (D. Debnath and R.M. Petty contributed equally to this work) Citation Format: Dipti Debnath, R. Max Petty, Nirupama Sabnis, Jinmin Zhang, Andras G. Lacko, Helivaldo Diógenes Souza, Petrônio Filgueiras Filho, J. Michael Mathis, Rafal Fudala. An improved strategy for delivering the mesoionic compound MIH 2.4Bl utilizing reconstituted high density nanoparticles (rHDL) in treating breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 300.

Colorectal cancer is one of the most significant types of cancer, ranking second in the world's mortality cases. As colorectal cancer is often diagnosed at a late stage of disease progression, effective treatments are necessary. Therefore, radiotherapy has become a fundamental approach in the treatment of colorectal cancer, especially those based on the use of Lu-177. A potential approach to meet this challenge is the use of nanotechnology through the development of radionuclide-based nanomaterials. In this work, we investigated a SiO2-derived class of nanomaterials formed by the insertion of the coordination complex, based on Eu3+ and pyrimidine-2,6-dicarboxylic acid (DPA), into nanoparticles of amino-functionalized mesoporous silica (EuDPA/SiO2-NH2). The properties of the EuDPA/SiO2-NH2 nanoparticles were initially investigated by SEM, FT-IR, TGA, and luminescence. The cellular uptake of EuDPA/SiO2-NH2 nanoparticles into HT-29 cells was confirmed by fluorescence microscopy. Radioactivity was incorporated into the EuDPA/SiO2-NH2 nanoparticles by replacing a tracer quantity of Eu3+ sites with the lanthanide element Lu-177, which resulted in the composition of a dual-modality probe for both SPECT imaging and tumor radiotherapy. Analysis of Lu-177 loading into EuDPA/SiO2-NH2 particles showed efficient incorporation, up to 93% radioactivity into the final compound. The imaging potential of the Lu-177-EuDPA/SiO2-NH2 nanoparticles was investigated by SPECT/CT imaging, a subcutaneous HT-29 mouse model of colorectal cancer. Image analysis showed that tumor localization was maintained after intratumoral administration for up to 48 h. To evaluate the therapeutic potential of Lu-177-EuDPA/SiO2-NH2 nanoparticles, HT-29 xenografts were treated in vivo by direct intratumoral injection. Compared with control (PBS) treatment or treatment with unlabeled EuDPA/SiO2-NH2 nanoparticles, the treatment with Lu-177-EuDPA/SiO2-NH2 nanoparticles resulted in a significantly reduced tumor growth. Together, the results of this study results indicate that Lu-177-EuDPA/SiO2-NH2 is a promising agent for further development in SPECT imaging and clinical treatment of colorectal cancer.

In this work, we report the synthesis of a new 1,3-thiazolium-5-thiolate derivative of a mesoionic compound (MIH 2.4Bl) and the characterization of its selective cytotoxicity on a panel of breast cancer cells lines. The cytotoxic effect of MIH 2.4Bl on breast cancer cell lines was determined by XTT and crystal violet assays, flow cytometry analysis, electron microscopy characterization, and terminal deoxynucleotidyl transferase (TdT) deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) apoptosis assays. As determined using XTT cell growth and survival assays, MIH 2.4Bl exhibited growth inhibition activity on most breast cancer cell lines tested, compared with normal human mammary epithelial cells. Three breast cancer cell lines (MCF-7, T-47D, and ZR-75-1) showed a more potent sensitivity index to growth inhibition by MIH 2.4Bl than the other breast cancer cell lines. Interestingly, these 3 cell lines were derived from tumors of Luminal A origin and have ER (estrogen receptor), PR (progesterone receptor), and HER2 (human epidermal growth factor receptor 2) positive expression. Additional analysis of cytotoxicity mediated by MIH 2.4Bl was performed using the MCF-7 cell line. MCF-7 cells displayed both time- and dose-dependent decreases in cell growth and survival, with a maximum cytotoxic effect observed at 72 and 96 hours. The MCF-7 cells were also characterized for cell cycle changes upon treatment with MIH 2.4Bl. Using flow cytometry analysis of cell cycle distribution, a treatment-dependent effect was observed; treatment of cells with MIH 2.4Bl increased the G2/M population to 34.2% compared with 0.1% in untreated (control) cells. Ultrastructural analysis of MFC-7 cells treated with MIH 2.4Bl at 2 different concentrations (37.5 and 75 μM) was performed by transmission electron microscopy. Cells treated with 37.5 μM MIH 2.4Bl showed morphologic changes beginning at 6 hours after treatment, while cells treated with 75 μM showed changes beginning at 3 hours after treatment. These changes were characterized by an alteration of nuclear morphology and mitochondrial degeneration consistent with apoptotic cell death. Results of a TUNEL assay performed on cells treated for 96 hours with MIH 2.4Bl supported the observation of apoptosis. Together, these results suggest that MIH 2.4Bl is a promising candidate for treating breast cancer and support further in vitro and in vivo investigation.

In the present study, the cytotoxic effects of a 1,3-thiazolium-5-thiolate derivative of a mesoionic compound, MIH 2.4Bl, were assessed in the MCF-7 breast cancer cell line. The cytotoxic effects of MIH 2.4Bl were determined using a crystal violet assay. Using a dose-response curve, the IC50 value of MIH 2.4Bl was determined to be 45.8±0.8 µM. Additionally, the effects of MIH 2.4Bl on mitochondrial respiration were characterized using oxygen consumption rate analysis. Treating MCF-7 cells with increasing concentrations of MIH 2.4Bl resulted in a significant reduction in all mitochondrial respiratory parameters compared with the control cells, indicative of an overall decrease in mitochondrial membrane potential. The induction of autophagy by MIH 2.4Bl was also examined by measuring changes in the expression of protein markers of autophagy. As shown by western blot analysis, treatment of MCF-7 cells with MIH 2.4Bl resulted in increased protein expression levels of Beclin-1 and ATG5, as well as an increase in the microtubule-associated protein 1A/1B light chain 3B (LC3B)-II to LC3B-I ratio compared with the control cells. Microarray analysis of changes in gene expression following MIH 2.4Bl treatment demonstrated 3,659 genes exhibited a fold-change ≥2. Among these genes, 779 were up-regulated, and 2,880 were down-regulated in cells treated with MIH 2.4Bl compared with the control cells. Based on the identity of the transcripts and fold-change of expression, six genes were selected for verification by reverse transcription-quantitative (RT-q)PCR; activating transcription factor 3, acidic repeat-containing protein, heparin-binding EGF-like growth factor, regulator of G-protein signaling 2, Dickkopf WNT signaling pathway inhibitor 1 and adhesion molecule with Ig like domain 2. The results of RT-qPCR analysis of RNA isolated from control and MIH 2.4Bl treated cells were consistent with the expression changes identified by microarray analysis. Together, these results suggest that MIH 2.4Bl may be a promising candidate for treating breast cancer and warrants further in vitro and in vivo investigation.

The near-infrared fluorescent (NIRF) dye, IR780, is recognized as a promising theranostic agent and has been widely investigated for imaging, chemotherapeutic, and phototherapeutic applications. However, its poor photostability and nonselective toxicities toward both cancer and normal cells limit its biological applications. Herein, we introduce the use of GUMBOS (a group of uniform materials based on organic salts) developed through counter-anion exchange with IR780 and subsequent nanomaterials (nanoGUMBOS) formed by complexation with cyclodextrin (CD) for enhanced chemo/photothermal therapy. Such CD-based nanoGUMBOS display improved aqueous stability, photostability, and photothermal effects relative to traditional IR780. The examination of in vitro cytotoxicity reveals that CD-based nano-GUMBOS are selectively toxic toward cancer cells and exhibit synergistically enhanced cytotoxicity toward cancer cells upon NIR laser irradiation. Additionally, in vivo NIRF imaging demonstrated selective accumulation of these nanoGUMBOS within the tumor site, indicating tumor-targeting properties. Further in vivo therapeutic study of these CD-based nanoGUMBOS suggests excellent chemo/photothermal antitumor effects. Using these studies, we herein demonstrate a promising strategy, via conversion of IR780 into nanoGUMBOS, that can be used for improved theranostic cancer treatment.

Colon cancer is one of the world’s most deadly diseases. Because of its internal location, it is necessary to obtain faster and more efficient diagnostic tools for this organ site. In this context, we studied the development of new luminescent nanoprobes (LNPs) as an alternative diagnostic apparatus for detecting this disease. The nanoparticles examined herein are lanthanide-doped sodium yttrium fluoride (NaYF4:Ln) and have shown to be promising as investigative devices. However, significant problems with the use of LNPs are the lack of biocompatibility and the targeting of the system to tumor regions. One of the strategies to bypass these problems is to increase of the particle lipophilicity modifying their surfaces with organic compounds that present high similarity to the biological system. In this work, we synthesized six new materials for use in bioimaging techniques obtained from the combination of nanoparticles of NaYF4:5%Eu with organic aromatic compounds covalently bonded. The materials were characterized structurally and morphologically using XRD and TEM, techniques, which showed the identification of the crystallographic phase β-NaYF4:5%Eu and its nanometric size (particles smaller than 50 nm). The conjugation process was confirmed by FT-IR spectra analysis and from the TGA profile. Excitation and emission spectra allowed the evaluation of the optical properties of the synthesized compounds. The interaction and cellular uptake was confirmed when HT-29 colon cancer cells were exposed to LNPs, indicating that the developed system has promising applications in bioimaging procedures.

An isothiocyanato-functionalized phthalocyanine (Pc) was synthesized in good yield from the corresponding amine-substituted Pc. This Pc reacted with ethanolamine, biotin hydrazine, and biotin diethylamine under mild conditions (room temperature in DMF or DMSO in the presence of TEA) to produce the corresponding thiourea products in 60-75% yields. All Pcs showed intense Q absorptions in DMF around 677 nm, emissions centered at 683 nm, and fluorescence quantum yields in the range 0.18-0.27. The Pcs were phototoxic to human carcinoma HEp2 cells (IC50 ~ 7 at 1.5 J/cm2) and localized in multiple organelles, including the lysosomes, Golgi and ER. One biotin-Pc conjugate was injected via tail vein into nude mice bearing HT-29 tumors and demonstrated selective localization in the tumor tissue.

Breast cancer is the most commonly diagnosed cancer in women, making up nearly 30% of all diagnosed cancer cases each year. While localized breast cancer is easily treated, advanced cases are difficult to treat resulting in poor five-year survival rates. Thus, new therapies capable of increasing treatment efficacy are needed. Oncolytic virotherapy using human adenovirus is a novel therapeutic approach capable of specifically targeting cancer cells while sparing normal tissue. The adenovirus vector is well-characterized and is uniquely suited for oncolytic virotherapy due to its systemic stability, good safety profile and the ability to infect a broad range of dividing and non-dividing cells. Replication of oncolytic adenoviruses within cancer cells causes the lysis of the cells and subsequent spread of progeny virions within the surrounding tumor stroma. One challenge in targeting cancer cells with adenovirus vectors has been the low expression of the endogenous receptor, the Coxsackie and adenovirus receptor (CXADR), prompting the search for new receptor targets. In this study, we engineered an adenovirus to contain the CXCL12 ligand to target the chemokine receptors CXCR4 and CXCR7 overexpressed in a variety of tumors. Altered expression of these receptors drives tumor progression, migration, invasion and metastasis. Previously, we developed a bispecific adaptor molecule containing the CXCL12 ligand to redirect a replication-deficient wild-type adenovirus to breast cancer cells overexpressing CXCR4. In the current study, we engineered a replication-competent oncolytic adenovirus modified with the CXCL12 ligand to target cancer cells overexpressing CXCR4 and CXCR7. A recombinant gene was constructed using the tail domain of the adenovirus fiber gene fused to the trimerization domain of the T4 fibritin gene followed by the mature CXCL12 sequence. After viral production, the presence of a modified fiber and the CXCL12 ligand were confirmed. Subsequently, the vector was tested in a panel of breast cancer cells for infection and cell killing efficacy in vitro. Receptor knock down and overexpression studies confirmed the specificity of the virus. Together, these studies address the hypothesis that constructing a retargeted oncolytic adenovirus using the CXCL12 ligand provides selective infection and killing of breast cancer cells overexpressing CXCR4 and CXCR7. These results support the rationale for further development of retargeted adenovirus vectors for oncolytic virotherapy in patients. Future experiments will be conducted to assess tumor targeting using a xenograft mouse model of human breast cancer. Citation Format: Samia M. O'Bryan, J. Michael Mathis. Characterizing an oncolytic adenovirus modified with the CXCL12 ligand for breast cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4776.

A series of five boron dipyrromethene (BODIPY) bioconjugates containing an epidermal growth factor receptor (EGFR)-targeted pegylated LARLLT peptide and/or a glucose or biotin ethylene diamine group were synthesized, and the binding capability of the new conjugates to the extracellular domain of EGFR was investigated using molecular modeling, surface plasmon resonance, fluorescence microscopy, competitive binding assays, and animal studies. The BODIPY conjugates with a LARLLT peptide were found to bind specifically to EGFR, whereas those lacking the peptide bound weakly and nonspecifically. All BODIPY conjugates showed low cytotoxicity (IC50 > 94 μM) in HT-29 cells, both in the dark and upon light activation (1.5 J/cm2). Studies of nude mice bearing subcutaneous human HT-29 xenografts revealed that only BODIPY conjugates bearing the LARLLT peptide showed tumor localization 24 h after intravenous administration. The results of our studies demonstrate that BODIPY bioconjugates bearing the EGFR-targeting peptide 3PEG-LARLLT show promise as near-IR fluorescent imaging agents for colon cancers overexpressing EGFR.

Abstract Breast cancer is the most commonly diagnosed cancer in women under 60. Localized breast cancer is easily treated, resulting in high survival rates. However, treatments for advanced disease are inadequate, resulting in poor five-year survival rates at less 24%. Thus, there is a great need for new therapies capable of increasing treatment efficacy. Oncolytic virotherapy using the human adenovirus is a novel therapeutic approach designed to specifically target cancer cells while sparing normal tissues. As a well-characterized vector, adenovirus is easily manipulated and results in high gene transfer efficiency. Combined with systemic stability, low pathogenicity and the ability to infect a broad range of dividing and non-dividing cells, this vector is uniquely suited for oncolytic virotherapy. Used as an oncolytic therapy, replication of the vector within cancer cells causes the lysis of the cells and subsequent spread of progeny virions within the surrounding tumor stroma. One challenge to targeting cancer cells with adenovirus has been the low expression of the endogenous adenovirus receptor, the Coxsackie and adenovirus receptor (CAR), prompting the search for new targets. This study engineered an adenovirus vector to target CXCR4, a seven-membrane spanning G-protein-coupled receptor, whose role is implicated in a wide variety of tumors, including breast cancer. Altered expression of CXCR4 drives cancer cell migration and invasion, which has been associated with metastasis. Previously, we developed a bispecific adaptor molecule targeting CXCR4 to retarget a replication-deficient adenovirus to breast cancer cells overexpressing CXCR4. In the current study, we have engineered a replication-competent oncolytic adenovirus targeting CXCR4, by replacing the adenovirus fiber gene with a modified fiber containing the SDF-1 ligand of CXCR4. The modified fiber was constructed using the T4 fibritin protein fused to the tail of the adenovirus fiber and attached to the CXCL12 ligand via a spacer protein. Also, the red fluorescent protein (RFP) sequence was fused to the capsid protein IX (pIX) gene for visual tracking. The virus was then rescued and amplified in HEK-293 cells for characterization and downstream applications. We confirmed the presence of a modified fiber and the specificity of CXCR4 binding. Subsequently, the vector was tested in a panel of breast cancer cells for infection and cell killing efficiency. Together these studies addressed the hypothesis that constructing a retargeted oncolytic adenovirus using the CXCL12 ligand provide selective infection and killing of breast cancer cells overexpressing CXCR4. These results provide a strong rationale for further developing the retargeted vector for oncolytic virotherapy in patients. Citation Format: Samia M. O'Bryan, J. Michael Mathis. Engineering an oncolytic adenovirus targeted to the CXCR4 chemokine receptor for breast cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5916.

Herein, we report on the role of endocytosis in the selective chemotherpeutic toxicity of rhodamine 6G (R6G) based nanomaterials, i.e., nanoGUMBOS, that are derived from a group of uniform materials based on organic salts (GUMBOS). Evaluation of cellular uptake in the presence and absence of endocytosis inhibitors suggests nanoGUMBOS internalization via clathrin-mediated endocytosis in cancer cells and reveals lack of endocytic internalization in normal cells. Results from characterization of these nanomaterials suggest that endocytic internalization in cancer cells leads to nanoGUMBOS dissociation within the endosomal environment. This ultimately results in selective cytotoxicity of the nanoGUMBOS for cancer cells with no toxicity toward normal cells under examined conditions. Following examination of the selectivity mechanism, in vivo investigations were performed to examine potential therapeutic properties of these nanoparticles. Remarkably, nanoGUMBOS treatment using a mouse xenograft model reduced the tumor volume by 50% suggesting retention of in vitro therapeutic properties in vivo. These results corroborate the selective behavior of nanoGUMBOS and demonstrate their in vivo therapeutic effects, providing further insight into the possible use of these nanomaterials as potential chemotherapeutic agents.

Abstract Breast cancer is the most commonly diagnosed cancer in women under 60. Localized breast cancer is easily treated, resulting in high survival rates. However, treatment for advanced disease is inadequate, with a five-year survival rate of less than 24%. Thus, there is a great need for new therapies capable of increasing therapeutic efficacy. Synthetic mesoionic compounds, belonging to the 1,3-thiazolium-5-thiolate group, are recognized for their broad spectrum of biological activities including antibiotic, antiparasitic, antiviral, anticonvulsant, antidepressant, antioxidant, analgesic, anti-inflammatory, and more recently for their potential antitumor activity. These compounds have the ability to cross cell membranes; the characteristic of mesoionic structures having distinct regions of positive and negative charge associated with a poly-heterocyclic aromatic ring system, indicates the capability of strong interactions with biomolecules such as DNA and proteins. In this study, the cytotoxic effects of mesoionic compound MI H 2.4 alone and in combination with zinc was examined in breast cancer cell lines (4TI, BT-20, BT-549, MCF7, MDA-MB-231, MDA-MB-436, MM2MT, T-47D, and ZR-75-1) and normal breast cell lineages (HuMEC, MCF-10A, and MCF-12A) were evaluated. The effect of this agent on cell cycle was also investigated. Different concentrations of mesoionic compound MI H 2.4 (MI H 2.4 free) and in combination with zinc (MI H 2.4 Zinc) were added to the cultured cells and incubated for 24, 48, 72 and 96 h. Cell survival and cytotoxicity were evaluated using crystal violet and MTT assays. Cell cycle analysis was performed using MCF7 cells that were stained with propidium iodide and analyzed by flow cytometry. The cytotoxic effects of mesoionic compounds (MI H 2.4 free and MI H 2.4 Zinc) were highest at72 and 96 h. The MI H 2.4 free and MI H 2.4 Zinc showed a similar inhibitory effect on breast cancer cell growth in the μM range. In contrast, the normal breast cell lineages showed low cytotoxicity to treatment with the mesoionic compounds. Treatment of MCF7 cells cultured with MI H 2.4 free blocked cell cycle progression at the G2 phase of the cell cycle after 24 h of treatment. Mitochondrial function of MCF7 cells was determined using a Seahorse XF-24 Extracellular Flux Analyzer. Treatment with MI H 2.4 free and MI H 2.4 Zinc for 24 h resulted in a decreased basal and maximal mitochondrial respiration. In summary, mesoionic compound MI H 2.4 may offer a novel therapeutic strategy in the treatment of breast cancer, considering that it has significant antitumoral activity in breast cancer cell lines and low cytotoxicity in normal cells. Citation Format: Luciana Amaral de Mascena Costa, Filipe Cássio Silva de Lima, Rodrigo da Silva Viana, Silvany de Sousa Araujo, Aurea Wischral, Helivaldo Diógenes da Silva Souza, Petrônio Filgueiras de Athayde-Filhoa, Leandro Araújo de Azevedo, Severino Alves Júnior, Manoel Adrião, J. Michael Mathis. Antitumor activity of the mesoionic compound MI H 2.4 on breast cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5877.

Breast cancer continues to be a leading cause of mortality among women. While at an early stage, localized breast cancer is easily treated; however, advanced stages of disease continue to carry a high mortality rate. The discrepancy in treatment success highlights that current treatments are insufficient to treat advanced-stage breast cancer. As new and improved treatments have been sought, one therapeutic approach has gained considerable attention. Oncolytic viruses are uniquely capable of targeting cancer cells through intrinsic or engineered means. They come in many forms, mainly from four major virus groups as defined by the Baltimore classification system. These vectors can target and kill cancer cells, and even stimulate immunotherapeutic effects in patients. This review discusses not only individual oncolytic viruses pursued in the context of breast cancer treatment but also the emergence of combination therapies with current or new therapies, which has become a particularly promising strategy for treatment of breast cancer. Overall, oncolytic virotherapy is a promising strategy for increased treatment efficacy for advanced breast cancer and consequently provides a unique platform for personalized treatments in patients.