Murine Metastatic Breast Cancer Research Articles

Discovery of novel 1,8-naphthalimide piperazinamide based benzenesulfonamides derivatives as potent carbonic anhydrase IX inhibitors and ferroptosis inducers for the treatment of triple-negative breast cancer

A novel series of 1,8-naphthalimide piperazinamide based benzenesulfonamides derivatives were designed and synthesized as carbonic anhydrase IX (CA IX) inhibitors and ferroptosis inducers for the treatment of triple-negative breast cancer (TNBC). The representative compound 9o exhibited more potent inhibitory activity and selective against CA IX over off-target CA II, compared with positive control SLC-0111. Molecular docking study was also performed to gain insights into the binding interactions of 9o in the binding pocket of CAIX. Moreover, compound 9o exhibited superior antitumor activities against breast cancer cells under hypoxia than that of normoxia conditions. Mechanism studies revealed that compound 9o could act as DNA intercalator and effectively suppressed cell migration, arrested the cell cycle at G1/S phase and induced apoptosis in MDA-MB-231 cells, while inducing ferroptosis accompanied by the dissipation of MMP and the elevation intracellular levels of ROS. Notably, in vivo studies demonstrated that 9o effectively inhibited tumor growth and metastasis in a highly metastatic murine breast cancer 4 T1 xenograft model. Taken together, this study suggests that compound 9o represents a potent and selective CA IX inhibitor and ferroptosis inducer for the treatment of TNBC.

The anti-breast cancer stem cell properties of gold(i)-non-steroidal anti-inflammatory drug complexes.

The anti-breast cancer stem cell (CSC) properties of a series of gold(i) complexes comprising various non-steroidal anti-inflammatory drugs (NSAIDs) and triphenylphosphine 1-8 are reported. The most effective gold(i)-NSAID complex 1, containing indomethacin, exhibits greater potency for breast CSCs than bulk breast cancer cells (up to 80-fold). Furthermore, 1 reduces mammosphere viability to a better extent than a panel of clinically used breast cancer drugs and salinomycin, an established anti-breast CSC agent. Mechanistic studies suggest 1-induced breast CSC death results from breast CSC entry, cytoplasm localisation, an increase in intracellular reactive oxygen species levels, cyclooxygenase-2 downregulation and inhibition, and apoptosis. Remarkably, 1 also significantly inhibits tumour growth in a murine metastatic triple-negative breast cancer model. To the best of our knowledge, 1 is the first gold complex of any geometry or oxidation state to demonstrate anti-breast CSC properties.

Investigation of the Anticancer Potential of 2-alkoxycarbonylallyl Esters Against Metastatic Murine Breast Cancer Line 4T1 Targeting the EGFR: A Combined Molecular Docking, QSAR, and Machine Learning Approach

Background:The search for novel and potent anticancer drugs is imperative. This present study aims to unravel the mechanisms of action of 2-alkoxyecarbonyl esters using robust model(s) that can accurately predict the bioactivity of novel compounds. Twenty-four potential anticancer 2- alkoxycarbonylallyl ester compounds obtained from the literature were employed in building a 3D-QSAR model.Objectives:The objective of this study is to determine the predictive ability of the GFA-based QSAR models and extreme machine learning models and compare them. The lead compounds and newly designed compounds were docked at the active site of a human epidermal growth factor receptor (EGFR) kinase domain to determine their binding modes and affinity.Methods:QikProp program and Spartan packages were employed for screening compounds for druglikeness and toxicity. QSAR models were equally used to predict the bioactivities of these molecules using the Material Studio package. Molecular docking of the molecules at the active site of an EGFR receptor, 1M17, was done using Auto dock tools.Results:The model of choice, with r2pred (0.857), satisfied the recommended standard for a stable and reliable model. The low value of r2, Q2 for several trials and cRp2 (0.779 ≥ 0.5) and the high value of correlation coefficient r2 for the training set (0.918) and test set (0.849) provide credence to the predictability of the model. The superior inhibition of EGFR displayed by the lead compounds (20 and 21) with binding energies of 6.70 and 7.00 kcalmol-1, respectively, is likely due to the presence of double bonds and α-ester groups. ADMET screening showed that these compounds are highly druggable. The designed compounds (A and B) displayed better inhibition of EGFR.Conclusion:The QSAR model used here performed better than the Random Forest Regression model for predicting the bioactivity of these anticancer compounds, while the designed compounds (A and B) performed better with higher binding affinity than the lead compounds. Implementing the developed model would be helpful in the search for novel anticancer agents.

Discovery of 3-Aminopyrazole Derivatives as New Potent and Orally Bioavailable AXL Inhibitors.

The receptor tyrosine kinase AXL is a promising target for anticancer drug discovery. Herein, we describe the discovery of 3-aminopyrazole derivatives as new potent and selective AXL kinase inhibitors. One of the representative compounds, 6li, potently inhibited AXL enzymatic activity with an IC50 value of 1.6 nM, and tightly bound with AXL protein with a Kd value of 0.26 nM, while was obviously less potent against most of the 403 wild-type kinases evaluated. Cell-based assays demonstrated that compound 6li potently inhibited AXL signaling, suppressed Ba/F3-TEL-AXL cell proliferation, reversed TGF-β1-induced epithelial-mesenchymal transition, and dose-dependently impeded cancer cell migration and invasion. Compound 6li also showed reasonable pharmacokinetic properties in rats and exhibited significant in vivo antitumor efficacy in a xenograft model of highly metastatic murine breast cancer 4T1 cells. Taken together, this study provides a new potent and selective AXL inhibitor for further anticancer drug discovery.

Preclinical evaluation of a microparticle-based transdermal vaccine patch against metastatic breast cancer

Breast cancer is the number one cause of cancer-related deaths among females. Current chemotherapy targets both tumor and normal cells, leading to pronounced side effects. Therefore, therapeutic vaccines acting against specific cancer cells would be the choice of treatment. We prepared microparticles entrapping the antigens obtained from a murine metastatic breast cancer cell line, 4 T1 using the spray drying technology. These microparticles were incorporated into microneedle patches to deliver to the animals for the efficacy study. An antineoplastic drug, cyclophosphamide, in a very low dose has been found to inhibit the immunosuppressive regulatory T cells (Treg) (Le and Jaffee, 2012). In-vivo efficacy of the microparticulate vaccine given along with a low dose of cyclophosphamide was evaluated in a murine breast cancer model. Animals immunized with vaccine microparticles showed considerably slower tumor growth than animals that did not receive the vaccine. The results of the study showed that the Tumor-Associated Antigens (TAAs) within the microparticles were responsible for the delayed tumor growth in vaccinated animals. Vaccinated animals also showed an increase in the population of CD4 and CD8 T cells. Overall, our results demonstrated that immunotherapy with vaccine microparticles encapsulating TAA’s could potentially be an effective treatment for metastatic breast cancer.

Host CLIC4 expression in the tumor microenvironment is essential for breast cancer metastatic competence.

The TGF-β-regulated Chloride Intracellular Channel 4 (CLIC4) is an essential participant in the formation of breast cancer stroma. Here, we used data available from the TCGA and METABRIC datasets to show that CLIC4 expression was higher in breast cancers from younger women and those with early-stage metastatic disease. Elevated CLIC4 predicted poor outcome in breast cancer patients and was linked to the TGF-β pathway. However, these associations did not reveal the underlying biological contribution of CLIC4 to breast cancer progression. Constitutive ablation of host Clic4 in two murine metastatic breast cancer models nearly eliminated lung metastases without reducing primary tumor weight, while tumor cells ablated of Clic4 retained metastatic capability in wildtype hosts. Thus, CLIC4 was required for host metastatic competence. Pre- and post-metastatic proteomic analysis identified circulating pro-metastatic soluble factors that differed in tumor-bearing CLIC4-deficient and wildtype hosts. Vascular abnormalities and necrosis increased in primary tumors from CLIC4-deficient hosts. Transcriptional profiles of both primary tumors and pre-metastatic lungs of tumor-bearing CLIC4-deficient hosts were consistent with a microenvironment where inflammatory pathways were elevated. Altogether, CLIC4 expression in human breast cancers may serve as a prognostic biomarker; therapeutic targeting of CLIC4 could reduce primary tumor viability and host metastatic competence.

Abstract LB532: Bifidobacterium longum RAPO alleviates the risk of immune-related adverse events of anti-PD-1 immunotherapy in a mouse model of triple-negative breast cancer

Abstract Background: Triple negative breast cancer (TNBC) has higher risk of early metastasis and recurrence compared with other types of breast cancer. Although immune checkpoint inhibitors (ICIs) have emerged as a feasible strategy for the treatment of TNBC, its use causes various side effects known as immune-related adverse events (irAEs) including pneumonitis, myocarditis, colitis, hepatitis, and nephritis. Considering severe irAEs could lead to ICIs termination and fatal outcomes, studies into immunotherapy that increases anti-tumor efficacy while reducing side effects are needed. We have previously reported that combination therapy of Bifidobacterium longum RAPO and anti-PD-1 shows a better efficacy compared with monotherapy in mice with TNBC. In the present study, we further investigated whether this combination therapy with probiotics would affect the risk of irAEs induced by anti-PD-1 therapy against TNBC. Methods: BALB/c mice bearing the 4T1 murine metastatic breast cancer cells were randomly assigned to tumor control, Bifidobacterium longum RAPO (RAPO), Anti-PD-1, or Anti-PD-1+RAPO group. Tumor tissues were analyzed by Affymetrix Mouse Gene 2.0 ST Array, and functional analysis of microarray data was performed using Ingenuity Pathway Analysis (IPA®, QIAGEN). Lung, heart, colon, liver, and kidney tissues were analyzed by qRT-PCR to determine expression of pro- and anti-inflammatory cytokines. Colon and liver tissues were also analyzed by a Western blot and immunohistochemistry (IHC), respectively. Results: Functional analysis revealed that inflammation in lung and cardiac lesion was predicted to be reduced in Anti-PD-1+RAPO group compared with Anti-PD-1 group. Indeed, expression of pro-inflammatory cytokines including IL1β, IL6, and TNFα was significantly decreased, while anti-inflammatory cytokine IL10 expression was increased in the lung, liver, and kidney tissues of Anti-PD-1+RAPO group compared with Anti-PD-1 group. Similarly, in the heart tissue, TNFα expression was decreased, whereas IL10 was significantly increased in Anti-PD-1+RAPO group than monotherapy group. In the colon tissue, combination therapy of Anti-PD-1 with RAPO significantly enhanced expression of IL10 and tight junction proteins such as occludin and ZO-1 compared with Anti-PD-1 treatment alone. Colonic expression of pro-inflammatory cytokines tended to be reduced in combination therapy group than Anti-PD-1 group. Furthermore, Anti-PD-1+RAPO group was associated with lower level of myeloperoxidase, a pro-inflammatory enzyme released by activated neutrophils, in the liver than Anti-PD-1 group. Conclusions: Collectively, in addition to the effects on anti-tumor efficacy, combination therapy of anti-PD-1 with B. longum RAPO alleviates the risk of irAEs in mice with TNBC. This study provides evidence that B. longum RAPO supplementation might be a novel therapeutic approach in cancer immunotherapy. [This work was supported by BIFIDO Co. and NRF (2020R1C1C1007553 to S-EK).] Citation Format: Hyeyoon Kim, Rira Oh, Ji-Won Heo, Geun Eog Ji, Myeong Soo Park, Sung-Eun Kim. Bifidobacterium longum RAPO alleviates the risk of immune-related adverse events of anti-PD-1 immunotherapy in a mouse model of triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB532.

Evaluation of the immunomodulatory activity of thalidomide on tumor-associated macrophages in the 4T1 murine metastatic breast cancer model

ABSTRACT The present work evaluated the immunomodulatory effect of thalidomide (Thal) at different doses on tumor-associated macrophages (TAMs) using a mouse model of human breast cancer. Mice were inoculated with 4T1 cells in the left flank and treated with Thal once a day at concentrations of 50, 100, and 150mg/kg body weight from the 5th day until the 28th day of tumor inoculation. The tumors were sized, proliferation index and TAMs count were evaluated in primary tumors and metastatic lungs. In addition, the metastasis rate was evaluated in the lungs. Thal at 150mg/kg significantly decreased tumor growth, proliferation index, and TAMs infiltration in primary tumors. Conversely, a higher number of TAMs and lower proliferation index were observed in metastatic lungs in mice treated with 150mg/kg of Thal. Furthermore, Thal at 150mg/kg significantly decreased the metastatic nodules in the lungs. Our findings demonstrated that Thal treatment considerably decreased the primary tumor and lung metastasis in mice associated with different TAM infiltration effects in these sites.

Nanoscale Coordination Polymers for Combined Chemotherapy and Photodynamic Therapy of Metastatic Cancer.

Combination therapy enhances anticancer efficacy through synergistic effects of different drugs/modalities and can potentially address the challenges in the treatment of metastatic diseases. Here we report the design of carb/pyro nanoscale coordination polymer nanoparticles that carry carboplatin (carb) in the core and the photosensitizer pyrolipid (pyro) on the shell for the treatment of metastatic triple negative breast cancer. Upon light irradiation, carb/pyro generated reactive oxygen species to cause severe cell apoptosis and early calreticulin exposure. Upon intravenous injection and local light irradiation, carb/pyro significantly regressed tumor growth in the 4T1 murine metastatic breast cancer model. When combined with an anti-CD47 antibody, carb/pyro with light irradiation completely eradicated primary and metastatic 4T1 tumors in 50% mice. The anticancer efficacy of carb/pyro was also demonstrated in the CT26 murine colorectal cancer model.

Abstract 72: Bifidobacterium longum RAPO enhances efficacy of anti-PD-1 immunotherapy in a mouse model of triple-negative breast cancer

Abstract Background: Triple negative breast cancer (TNBC) represents approximately 15-20% of all breast cancers and 35% of breast cancer death. TNBC has a highly aggressive behavior with the increased risk of early metastasis and relapse and poor survival rate. Given that TNBC is associated with higher levels of tumor-infiltrating lymphocytes and programmed cell death ligand 1 (PD-L1), immune checkpoint inhibitors (ICI) are considered as the appropriate treatment of patients with TNBC. However, it has been reported that ICI monotherapy is less effective compared with combination therapy. Recent several studies suggest that gut microbiome plays a critical role in the efficacy of ICI therapy. Thus, we investigated the effects of Bifidobacterium longum RAPO supplementation on anti-PD-1 therapy against TNBC and the underlying mechanisms in vivo. Methods: The 4T1 murine metastatic breast cancer cells were injected s.c into the flank of female BALB/c mice. When tumors reached 50-150 mm3, mice were randomly assigned to one of four groups; tumor control (TC), Anti-PD-1, B. longum RAPO (RAPO), or Anti-PD-1+RAPO (n=10 per group). Anti-PD-1 antibody was injected i.p. 5 times at 3 day intervals. B. longum RAPO was orally administered daily from 2 days before the first injection of anti-PD-1. Spleen and tumor tissues were analyzed by flow cytometry, qRT-PCR, and immunohistochemistry, and fecal samples were collected for 16S rRNA gene sequencing. Results: On day 12, tumor volume was significantly inhibited in Anti-PD-1+RAPO group compared with TC and Anti-PD-1 groups. Higher levels of PD-L1 IHC score and PD-L1 mRNA expression were observed in tumor tissues of Anti-PD-1+RAPO group. Anti-PD-1+RAPO group was also associated with the increased levels of spleen NKT cells and tumor NK cells. The proportion of pro-tumor M2 macrophages and M2/M1 ratio were significantly decreased in tumor tissues of Anti-PD-1+RAPO group than those of Anti-PD-1 group. Similarly, combination therapy of Anti-PD-1 with RAPO significantly reduced mRNA expression of M2 markers such as IL10 and Arg1, while it augmented that of anti-tumor cytokines including IFNγ and TNFα compared with Anti-PD-1 treatment alone. In addition, the relative abundance of the genus Bifidobacterium was remarkably enriched in Anti-PD-1+RAPO group compared with other groups. In Anti-PD-1+RAPO group, the relative abundance of the genus Akkermansia and Lachnospiraceae NK4A136 group were significantly increased after administration for 2 weeks. Conclusions: Our data suggests that combination therapy of B. longum RAPO with anti-PD-1 modulates anti-tumor immunity and gut microbiota, contributing to the better response to anti-PD-1 immunotherapy in mice with TNBC. This study provides evidence that B. longum RAPO might be a potential candidate for immunomodulatory pharmabiotics in cancer immunotherapy. Citation Format: Hyeyoon Kim, Rira Oh, Sangjun Park, Geun Eog Ji, Myeong Soo Park, Sung-Eun Kim. Bifidobacterium longum RAPO enhances efficacy of anti-PD-1 immunotherapy in a mouse model of triple-negative 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 72.

Advanced Nanosystems for Clinical Translation

Advanced Nanosystems for Clinical Translation

Synthesis, in vitro, and in vivo evaluation of novel N-phenylindazolyl diarylureas as potential anti-cancer agents

Novel N-phenylindazole based diarylureas have been designed, synthesized and evaluated as potential anticancer agents. In vitro cell viability studies of these derivatives illustrate good potency with IC50 values in the range of 0.4–50 μM in several cancer cell lines including murine metastatic breast cancer 4T1, murine glioblastoma GL261, human triple negative breast cancer MDA-MB-231, human pancreatic cancer MIAPaCa-2, and human colorectal cancer cell line WiDr. The ester group in the lead compound 8i was modified to incorporate amino-amides to increase solubility and stability while retaining biological activity. Further in vitro studies reveal that lead candidates inhibit tube length in HUVEC cells. In vivo systemic toxicity studies indicate that these candidate compounds are well tolerated in mice without any significant side effects. Anticancer efficacy studies in WiDr tumor xenograft and 4T1 tumor syngraft models demonstrate that the lead candidate 11 exhibits significant antitumor properties as a single agent in these tumor models.

A bilateral tumor model identifies transcriptional programs associated with patient response to immune checkpoint blockade

Immune checkpoint blockade (ICB) is efficacious in many diverse cancer types, but not all patients respond. It is important to understand the mechanisms driving resistance to these treatments and to identify predictive biomarkers of response to provide best treatment options for all patients. Here we introduce a resection and response-assessment approach for studying the tumor microenvironment before or shortly after treatment initiation to identify predictive biomarkers differentiating responders from nonresponders. Our approach builds on a bilateral tumor implantation technique in a murine metastatic breast cancer model (E0771) coupled with anti-PD-1 therapy. Using our model, we show that tumors from mice responding to ICB therapy had significantly higher CD8+ T cells and fewer Gr1+CD11b+ myeloid-derived suppressor cells (MDSCs) at early time points following therapy initiation. RNA sequencing on the intratumoral CD8+ T cells identified the presence of T cell exhaustion pathways in nonresponding tumors and T cell activation in responding tumors. Strikingly, we showed that our derived response and resistance signatures significantly segregate patients by survival and associate with patient response to ICB. Furthermore, we identified decreased expression of CXCR3 in nonresponding mice and showed that tumors grown in Cxcr3-/- mice had an elevated resistance rate to anti-PD-1 treatment. Our findings suggest that the resection and response tumor model can be used to identify response and resistance biomarkers to ICB therapy and guide the use of combination therapy to further boost the antitumor efficacy of ICB.

Abstract 3020: Tumor pharmacokinetics of the metastatic cancer inhibitor MBQ-167 in mice

Abstract The Rho GTPases Rac and Cdc42 are potential targets against metastatic disease. Our group characterized the small molecule MBQ-167 as an effective dual Rac/Cdc42 inhibitor that reduces HER2 positive and triple negative tumor growth and metastasis in mice by ~90%. To continue validating this drug for FDA approval, we recently elucidated the plasma pharmacokinetics and the tissue distribution of MBQ-167 in mice (Maldonado et al., 2019). However, further studies are needed to characterize the tumor pharmacokinetics of MBQ-167 to determine drug exposure, time-to-peak, and the length of time that MBQ-167 remains in tumors after administration. The purpose of this study was to determine the tumor pharmacokinetics of MBQ-167 in a single dose input scheme (10 mg/kg BW) following intraperitoneal (IP) administration. Thirty-five female BALB/c mice (5 mice/group) were injected with 2.5 × 105 4T1 murine metastatic breast cancer cells at the mammary fat pad. After tumor establishment, a single dose of MBQ-167 (10 mg/kg BW) was administered via IP. Tumors were collected at 0.5, 1, 3, 6, 9,12, and 24 hours following drug administration. We used a validated bioanalytical method using supercritical fluid chromatography coupled with tandem mass spectrometry (SFC-MS/MS) to quantify MBQ-167 in tumors. Pharmacokinetic parameters were obtained by non-compartmental analysis using WinNolin® software. Pharmacokinetic analysis revealed that MBQ-167 has an elimination half-life (t1/2) of 8.64 hours in tumors, which is much longer than its half-life in plasma (2.17 hours), indicating preferential absorption and retention of this lipophilic small molecule in tumor tissues. The area under the curve (AUC0-t) was 4.39 %ID⋅hr/g with a maximum concentration (Cmax) of 1268.9 ng/g in tumors. Moreover, the time-to-peak concentration in tumors was 0.5 hours. Hence, this study supports the continued development of MBQ-167 as a potential anti-cancer therapeutic. Citation Format: Maria Del Mar Maldonado, Ailed M. Cruz-Collazo, Luis D. Borrero-García, Gabriela T. Rosado-González, Jean F. Ruiz-Calderon, Jorge Duconge, Suranganie Dharmawardhane. Tumor pharmacokinetics of the metastatic cancer inhibitor MBQ-167 in mice [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3020.

Immunostimulatory and anti-tumor metronomic cyclophosphamide regimens assessed in primary orthotopic and metastatic murine breast cancer

The impressive successes of immune checkpoint blockade antibodies to treat various types of cancer are limited to minor subsets of patients. Combination therapy strategies, including with chemotherapy, are being explored to possibly improve the efficacy of immunotherapies. Here we report results regarding the use of an immunostimulatory regimen of metronomic cyclophosphamide (CTX). We show that in orthotopic models of syngeneic murine triple-negative breast cancer (EMT6), CTX administered at 140 mg/kg every 6 days (CTX140 1q6d) is superior at inhibiting primary tumor growth when compared to maximum tolerated dose or daily oral (continuous) low-dose CTX. In SCID or SCID beige mice, anti-tumor effects of CTX140 1q6d are reduced, reinforcing the therapeutic contribution of the adaptive and innate immune systems. In a second breast cancer model (SP1-AC2M2), CTX140 1q6d again showed clear superiority in anti-tumor effects, causing complete tumor regressions; however, these mice were not protected from subsequent tumor re-challenge, suggesting absence of immune memory. We also show that in an aggressive and metastatic cisplatin-resistant variant (EMT6-CDDP), CTX140 1q6d is superior and invokes an influx of intra-tumoral CD4+ and CD8+ T cells. CTX increases expression of tumor cell PD-L1; however, when combined with concomitant PD-L1 antibody therapy none of the CTX regimens showed increased benefit. This work sheds light on the potential use of metronomic CTX for the treatment of breast cancer, in particular using the quasi-weekly regimen, but also underscores the complexity of the anti-tumor mechanisms and potential to improve immune checkpoint therapy efficacy.

Hesperetin alleviates doxorubicin-induced migration in 4T1 breast cancer cells

BackgroundHesperetin (Hst), a citrus flavanone, is widely distributed among citrus fruits, including lemons. Hst has been shown to possess bioactivity as an antioxidant, anti-inflammatory, anti-allergic, hypolipidemic, vasoprotector, and anticancer agent. This study aimed to identify potential combinations of Hst and the chemotherapeutic agent doxorubicin (Dox) as co-chemotherapy agents against 4T1 murine metastatic breast cancer cells.ResultsMTT assay results showed that Hst exhibited cytotoxic effect in 4T1 cells, and its combination with Dox showed a synergistic effect based on the CI value. The combination of Hst and Dox increased G2/M phase cell cycle arrest and apoptosis induction. The combination of Hst and Dox inhibited migration and decreased MMP-9 expression in 4T1 cells.ConclusionIn conclusion, the results of this study show that Hst has potential as a Dox co-chemotherapy against 4T1 cells by inducing G2/M phase cell cycle arrest and apoptosis. More importantly, Hst reduces Dox-induced migration and decreases MMP-9 expression.

Postablation Modulation after Single High-Dose Radiation Therapy Improves Tumor Control via Enhanced Immunomodulation.

Radiotherapy (RT) is frequently used for local control of solid tumors using equal dose per fraction. Recently, single high-dose radiation has been used for ablation of solid tumors. In this report, we provide a novel immunological basis for radiation dose fractionation consisting of a single high-dose radiotherapy, followed by postablation modulation (PAM) with four daily low-dose fractions (22 Gy + 0.5 Gy × 4) to reprogram the tumor microenvironment by diminishing immune suppression, enabling infiltration of effector cells and increasing efficacy of tumor control. Palpable 3LL and 4T1 tumors in C57Bl/6 and Balb/c mice were irradiated with the Small-Animal Radiation Research Platform irradiator, and tumor growth and survival were monitored. Immunomodulation of tumor and immune cells in vitro and in vivo characterization of tumor-infiltrating immune effector cells were performed by FACS. For systemic application of PAM-RT, whole-lung irradiation was administered in 4T1-bearing Balb/c mice. We report significant tumor growth delays and increased survival in 3LL tumor-bearing mice with PAM. Primary tumor PAM-RT increased infiltration of immune effector cells and decreased Treg in irradiated tumors and secondary lymphoid organs. In a model of murine metastatic breast cancer (4T1), we demonstrated that systemic PAM-RT to the whole lung, 12 days after primary tumor ablative radiotherapy, increased survival with suppression of pulmonary metastases. We provide a novel immunologic basis for radiation dose fractionation consisting of a single high dose of radiotherapy followed by daily low-dose PAM-RT fractionation to improve the immunogenic potential of ablative radiotherapy.

MicroRNA-710 regulates multiple pathways of carcinogenesis in murine metastatic breast cancer.

Prior research has shown that critical differences between non-metastatic and metastatic tumor cells are at the level of microRNA. Consequently, harnessing these molecules for the treatment of metastatic cancer could have significant clinical impact. In the present study, we set out to identify metastasis-specific microRNAs which drive metastatic colonization of distant organs. Using a murine model of metastatic breast cancer, we employed a directed approach in which we screened for microRNAs that are differentially expressed between the primary tumors and metastatic lesions but concordantly expressed in all of the metastatic lesions irrespective of the tissue that is colonized. Of the identified targets, we focused on miR-710, which was consistently and significantly downregulated in the metastatic lesions relative to the primary tumors. The level of downregulation was independent of the distant organ that is involved, suggesting that miR-710 plays a fundamental role in metastatic colonization. Computational target prediction suggested a pleiotropic role for miR-710 in apoptosis, migration and invasion, and stemness. Using a previously validated oligonucleotide delivery system, we introduced miR-710 mimics into 4T1 metastatic breast adenocarcinoma cells and assessed the resultant phenotypic effects. We demonstrated significant inhibition of cell viability, migration, and invasion. We also showed that the treatment profoundly enhanced cell senescence, reduced stemness, and influenced markers of epithelial to mesenchymal transition, as evidenced by enhanced E-cadherin and reduced vimentin expression. This knowledge represents a first step towards harnessing a similar approach to discover novel microRNA targets with therapeutic potential in metastasis.

Dexamethasone Increases Cisplatin-Loaded Nanocarrier Delivery and Efficacy in Metastatic Breast Cancer by Normalizing the Tumor Microenvironment.

Dexamethasone is a glucocorticoid steroid with anti-inflammatory properties used to treat many diseases, including cancer, in which it helps manage various side effects of chemo-, radio-, and immunotherapies. Here, we investigate the tumor microenvironment (TME)-normalizing effects of dexamethasone in metastatic murine breast cancer (BC). Dexamethasone normalizes vessels and the extracellular matrix, thereby reducing interstitial fluid pressure, tissue stiffness, and solid stress. In turn, the penetration of 13 and 32 nm dextrans, which represent nanocarriers (NCs), is increased. A mechanistic model of fluid and macromolecule transport in tumors predicts that dexamethasone increases NC penetration by increasing interstitial hydraulic conductivity without significantly reducing the effective pore diameter of the vessel wall. Also, dexamethasone increases the tumor accumulation and efficacy of ∼30 nm polymeric micelles containing cisplatin (CDDP/m) against murine models of primary BC and spontaneous BC lung metastasis, which also feature a TME with abnormal mechanical properties. These results suggest that pretreatment with dexamethasone before NC administration could increase efficacy against primary tumors and metastases.

Magnetophoretic Delivery of a Tumor-Priming Agent for Chemotherapy of Metastatic Murine Breast Cancer.

Tumor microenvironment is a significant physical barrier to the effective delivery of chemotherapy into solid tumors. To overcome this challenge, tumors are pretreated with an agent that reduces cellular and extracellular matrix densities prior to chemotherapy. However, it also comes with a concern that metastasis may increase due to the loss of protective containment. We hypothesize that timely priming at the early stage of primary tumors will help control metastasis. To test this, we primed orthotopic 4T1 breast tumors with a paclitaxel (PTX)-loaded iron-oxide-decorated poly(lactic- co-glycolic acid) nanoparticle (NP) composite (PTX@PINC), which can be quickly concentrated in target tissues with the aid of an external magnet, and monitored its effect on the delivery of subsequently administered NPs. Magnetic resonance imaging and optical whole-body imaging confirmed that PTX@PINC was efficiently delivered to tumors by the external magnet and help loosen the tumors to accommodate subsequently delivered NPs. Consistently, the primed tumors responded to Doxil better than nonprimed tumors. In addition, lung metastasis was significantly reduced in the animals PINC-primed prior to Doxil administration. These results support that PINC combined with magnetophoresis can facilitate the timely management of primary tumors with a favorable secondary effect on metastasis.