Microglia-mediated drug substance transfer promotes chemoresistance in brain tumors: insights from an in vitro co-culture model using GCV/Tk prodrug system.

BACKGROUND: It is well known that tumor-associated macrophages (TAMs) play essential roles in brain tumor resistance to chemotherapy. However, the detailed mechanisms of how TAMs are involved in brain tumor resistance are still unclear and lack a suitable analysis model. METHODS: A BV2 microglial cells with ALTS1C1 astrocytoma cells in vitro co-culture system was used to mimic the microglia dominating tumor stroma in the tumor invasion microenvironment and explore the interaction between microglia and brain tumor cells. RESULTS: Our result suggested that microglia could form colonies with glioma cells under high-density culturing conditions and protect glioma cells from apoptosis induced by chemotherapeutic drugs. Moreover, this study demonstrates that microglia could hijack drug substances from the glioma cells and reduce the drug intensity of ALTS1C1 via direct contact. Inhibition of gap junction protein prevented microglial-glioma colony formation and microglia-mediated chemoresistance. CONCLUSIONS: This study provides novel insights into how glioma cells acquire chemoresistance via microglia-mediated drug substance transferring, providing a new option for treating chemo-resistant brain tumors.

Marginative Delivery-Mediated Extracellular Leakiness and T Cell Infiltration in Lung Metastasis by a Biomimetic Nanoraspberry.

T lymphocytes infiltrate the most devastating metastatic tumors for immunotherapy, allowing the potential for tumor metastasis suppression. However, tumor heterogeneity often restricts the infiltration of immune cells and possesses immune privilege that leads to protection from the immune attack, especially for invading metastatic clusters. Here, an exosome-camouflaged nanoraspberry (RB@Exo) doubling as a metastases-targeting agent and T cell-infiltration inducer that delivers an anticancer drug and energy is reported. The RB@Exo integrated an exosome-derived margination effect, and density-mediated nanoparticle-induced extracellular leakiness (nanoEL) exhibited more than a 70% colocalization of the RB@Exo to metastatic tumors in the lung in vivo. The release of cancer cell-cell interactions at the metastasis via nanoEL also elicited the 10-fold infiltration of T lymphocytes. The synergy of the T cell infiltration and photolytic effects transported by the RB@Exo deep into the metastatic tumors effectively inhibited the tumor in 60 days when treated with a single alternating magnetic field (AMF).

Ablative Radiotherapy Reprograms the Tumor Microenvironment of a Pancreatic Tumor in Favoring the Immune Checkpoint Blockade Therapy.

The low overall survival rate of patients with pancreatic cancer has driven research to seek a new therapeutic protocol. Radiotherapy (RT) is frequently an option in the neoadjuvant or palliative settings for pancreatic cancer treatment. This study explored the effect of RT protocols on the tumor microenvironment (TME) and their consequent impact on anti-programmed cell death ligand-1 (PD-L1) therapy. Using a murine orthotopic pancreatic tumor model, UN-KC-6141, RT-disturbed TME was examined by immunohistochemical staining. The results showed that ablative RT is more effective than fractionated RT at recruiting T cells. On the other hand, fractionated RT induces more myeloid-derived suppressor cell infiltration than ablative RT. The RT-disturbed TME presents a higher perfusion rate per vessel. The increase in vessel perfusion is associated with a higher amount of anti-PD-L1 antibody being delivered to the tumor. Animal survival is increased by anti-PD-L1 therapy after ablative RT, with 67% of treated animals surviving more than 30 days after tumor inoculation compared to a median survival time of 16.5 days for the control group. Splenocytes isolated from surviving animals were specifically cytotoxic for UN-KC-6141 cells. We conclude that the ablative RT-induced TME is more suited than conventional RT-induced TME to combination therapy with immune checkpoint blockade.

Local Interleukin-12 Treatment Enhances the Efficacy of Radiation Therapy by Overcoming Radiation-Induced Immune Suppression.

Radiation therapy (RT) recruits myeloid cells, leading to an immunosuppressive microenvironment that impedes its efficacy against tumors. Combination of immunotherapy with RT is a potential approach to reversing the immunosuppressive condition and enhancing tumor control after RT. This study aimed to assess the effects of local interleukin-12 (IL-12) therapy on improving the efficacy of RT in a murine prostate cancer model. Combined treatment effectively shrunk the radioresistant tumors by inducing a T helper-1 immune response and influx of CD8+ T cells. It also delayed the radiation-induced vascular damage accompanied by increased α-smooth muscle actin-positive pericyte coverage and blood perfusion. Moreover, RT significantly reduced the IL-12-induced levels of alanine aminotransferase in blood. However, it did not further improve the IL-12-induced anti-tumor effect on distant tumors. Upregulated expression of T-cell exhaustion-associated genes was found in tumors treated with IL-12 only and combined treatment, suggesting that T-cell exhaustion is potentially correlated with tumor relapse in combined treatment. In conclusion, this study illustrated that combination of radiation and local IL-12 therapy enhanced the host immune response and promoted vascular maturation and function. Furthermore, combination treatment was associated with less systemic toxicity than IL-12 alone, providing a potential option for tumor therapy in clinical settings.

Graphene Quantum Dots-Mediated Theranostic Penetrative Delivery of Drug and Photolytics in Deep Tumors by Targeted Biomimetic Nanosponges.

Dual-targeted delivery of drugs and energy by nanohybrids can potentially alleviate side effects and improve the unique features required for precision medicine. To realize this aim, however, the hybrids which are often rapidly removed from circulation and the piled up tumors periphery near the blood vessels must address the difficulties in low blood half-lives and tumor penetration. In this study, a sponge-inspired carbon composites-supported red blood cell (RBC) membrane that doubles as a stealth agent and photolytic carrier that transports tumor-penetrative agents (graphene quantum dots and docetaxel (GQD-D)) and heat with irradiation was developed. The RBC-membrane enveloped nanosponge (RBC@NS) integrated to a targeted protein that accumulates in tumor spheroids via high lateral bilayer fluidity exhibits an 8-fold increase in accumulation compared to the NS. Penetrative delivery of GQDs to tumor sites is actuated by near-infrared irradiation through a one-atom-thick structure, facilitating penetration and drug delivery deep into the tumor tissue. The synergy of chemotherapy and photolytic effects was delivered by the theranostic GQDs deep into tumors, which effectively damaged and inhibited the tumor in 21 days when treated with a single irradiation. This targeted RBC@GQD-D/NS with the capabilities of enhanced tumor targeting, NIR-induced drug penetration into tumors, and thermal ablation for photolytic therapy promotes tumor suppression and exhibits potential for other biomedical applications.

Sigma-2 receptor/TMEM97 agonist PB221 as an alternative drug for brain tumor.

BACKGROUND: There are limited effective drugs that can reach the brain to target brain tumors, in particular glioblastoma, which is one of the most difficult cancers to be cured from. Because the overexpression of the sigma-2 receptor is frequently reported in glioma clinical samples and associated with poor prognosis and malignancy, we herein studied the anti-tumor effect of the sigma-2 receptor agonist PB221 (4-cyclohexyl-1-[3-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)propyl]piperidine) on an anaplastic astrocytoma tumor model based on previous encouraging results in pancreatic cancer and neuroblastoma SK-N-SH cells. METHODS: The expression of the sigma-2 receptor, transmembrane protein 97 (TMEM97), in ALTS1C1 and UN-KC6141 cell lines was measured by RT-PCR and quantitative RT-PCR. The binding of sigma-2 receptor fluorescent ligands PB385 (6-[5-[3-(4-cyclohexylpiperazin-1-yl)propyl]-5,6,7,8-tetrahydronaphthalen-5-yloxy]-N-(7-nitro-2,1,3-benzoxadiazol-4-yl)hexanamine) and NO1 (2-{6-[2-(3-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)propyl)-3,4-dihydroisoquinolin-1(2H)-one-5-yloxy]hexyl}-5-(dimethylamino)isoindoline-1,3-dione) was examined by flow cytometry and the fluorescent plate reader. The antitumor activity of PB221 was initially examined in the murine brain tumor cell line ALTS1C1 and then in the murine pancreatic cell line UN-KC6141. The potential therapeutic efficacy of PB221 for murine brain tumors was examined by in vitro migration and invasion assays and in vivo ectopic and orthotopic ALTS1C1 tumor models. RESULTS: The IC50 of PB221 for ALTS1C1 and UN-KC6141 cell lines was 10.61 ± 0.96 and 13.13 ± 1.15 µM, respectively. A low dose of PB221 (1 µM) significantly repressed the migration and invasion of ALTS1C1 cells, and a high dose of PB221 (20 µM) resulted in the apoptotic cell death of ALTS1C1 cells. These effects were reduced by the lipid antioxidant α-tocopherol, but not by the hydrophilic N-acetylcysteine, suggesting mitochondrial oxidative stress is involved. The in vivo study revealed that PB221 effectively retarded tumor growth to 36% of the control tumor volume in the ectopic intramuscular tumor model and increased the overall survival time by 20% (from 26 to 31 days) in the orthotopic intracerebral tumor model. CONCLUSIONS: This study demonstrates that the sigma-2 receptor agonist PB221 has the potential to be an alternative chemotherapeutic drug for brain tumors with comparable side effects as the current standard-of-care drug, temozolomide.

Radiotherapy-Controllable Chemotherapy from Reactive Oxygen Species-Responsive Polymeric Nanoparticles for Effective Local Dual Modality Treatment of Malignant Tumors.

Radiotherapy is one of the general approaches to deal with malignant solid tumors in clinical treatment. To improve therapeutic efficacy, chemotherapy is frequently adopted as the adjuvant treatment in combination with radiotherapy. In this work, a reactive oxygen species (ROS)-responsive nanoparticle (NP) drug delivery system was developed to synergistically enhance the antitumor efficacy of radiotherapy by local ROS-activated chemotherapy, taking advantages of the enhanced concentration of reactive oxygen species (ROS) in tumor during X-ray irradiation and/or reoxygenation after X-ray irradiation. The ROS-responsive polymers, poly(thiodiethylene adipate) (PSDEA) and PEG-PSDEA-PEG, were synthesized and employed as the major components assembling in aqueous phase into polymer NPs in which an anticancer camptothecin analogue, SN38, was encapsulated. The drug-loaded NPs underwent structural change including swelling and partial dissociation in response to the ROS activation by virtue of the oxidation of the nonpolar sulfide residues in NPs into the polar sulfoxide units, thus leading to significant drug unloading. The in vitro performance of the chemotherapy from the X-ray irradiation preactivated NPs against BNL 1MEA.7R.1 murine carcinoma cells showed comparable cytotoxicity to free drug and appreciably enhanced effect on killing cancer cells while the X-ray irradiation being incorporated into the treatment. The in vivo tumor growth was fully inhibited with the mice receiving the local dual modality treatment of X-ray irradiation together with SN38-loaded NPs administered by intratumoral injection. The comparable efficacy of the local combinational treatment of X-ray irradiation with SN38-loaded NPs to free SN38/irradiation dual treatment corroborated the effectiveness of ROS-mediated drug release from the irradiated NPs at tumor site. The IHC examination of tumor tissues confirmed the significant reduction of VEGFA and CD31 expression with the tumor receiving the local dual treatment developed in this work, thus accounting for the absence of tumor regrowth compared to other single modality treatment.

Dual roles of tumour cells-derived matrix metalloproteinase 2 on brain tumour growth and invasion.

BACKGROUND: A previous study on a murine astrocytoma cell-line ALTS1C1 showed a highly invasive pattern similar to clinical anaplastic astrocytoma in vivo. This cell-line also expressed a high level of matrix metalloproteinase 2 (MMP2). This study aimed to verify the role of MMP2 in brain tumour progression. METHODS: ALTS1C1 and MMP2 knockdown (MMP2kd) cells were inoculated intracranially, and tumour microenvironment was assessed by immunohistochemistry staining. RESULTS: MMP2 expression was co-localised with CD31-positive cells at invading the tumour front and correlated with an invasive marker GLUT-1. The suppression of MMP2 expression prolonged the survival of tumour-bearing mice associated with tumours having smoother tumour margins, decreased Ki67-proliferating index, and down-regulated GLUT-1 antigen. Although the reduction of MMP2 expression did not alter the vessel density in comparison to parental ALTS1C1 tumours, vessels in MMP2kd tumours were less functional, as evidenced by the low ratio of pericyte coverage and reduction in Hoechst33342 dye perfusion. CONCLUSIONS: This study illustrated that tumour-derived MMP2 has at least two roles in tumour malignancy; to enhance tumour invasiveness by degrading the extracellular matrix and to enhance tumour growth by promoting vessel maturation and function.

Gadolinium-doped iron oxide nanoparticles induced magnetic field hyperthermia combined with radiotherapy increases tumour response by vascular disruption and improved oxygenation.

The gadolinium-doped iron oxide nanoparticles (GdIONP) with greater specific power adsorption rate (SAR) than Fe3O4 was developed and its potential application in tumour therapy and particle tracking were demonstrated in transgenic adenocarcinoma of the mouse prostate C1 (TRAMP-C1) tumours. The GdIONPs accumulated in tumour region during the treatment could be clearly tracked and quantified by T2-weighted MR imaging. The therapeutic effects of GdIONP-mediated hyperthermia alone or in combination with radiotherapy (RT) were also evaluated. A significant increase in the tumour growth time was observed following the treatment of thermotherapy (TT) only group (2.5 days), radiation therapy only group (4.5 days), and the combined radio-thermotherapy group (10 days). Immunohistochemical staining revealed a reduced hypoxia region with vascular disruption and extensive tumour necrosis following the combined radio-thermotherapy. These results indicate that GdIONP-mediated hyperthermia can improve the efficacy of RT by its dual functions in high temperature (temperature greater than 45 °C)-mediated thermal ablation and mild-temperature hyperthermia (MTH) (temperature between 39 and 42 °C)-mediated reoxygenation.

Preparation, cytotoxicity and in vivo bioimaging of highly luminescent water-soluble silicon quantum dots.

Designing various inorganic nanomaterials that are cost effective, water soluble, optically photostable, highly fluorescent and biocompatible for bioimaging applications is a challenging task. Similar to semiconducting quantum dots (QDs), silicon QDs are another alternative and are highly fluorescent, but non-water soluble. Several surface modification strategies were adopted to make them water soluble. However, the photoluminescence of Si QDs was seriously quenched in the aqueous environment. In this report, highly luminescent, water-dispersible, blue- and green-emitting Si QDs were prepared with good photostability. In vitro studies in monocytes reveal that Si QDs exhibit good biocompatibility and excellent distribution throughout the cytoplasm region, along with the significant fraction translocated into the nucleus. The in vivo zebrafish studies also reveal that Si QDs can be evenly distributed in the yolk-sac region. Overall, our results demonstrate the applicability of water-soluble and highly fluorescent Si QDs as excellent in vitro and in vivo bioimaging probes.

First demonstration of gold nanorods-mediated photodynamic therapeutic destruction of tumors via near infra-red light activation.

Previously, a large volume of papers reports that gold nanorods (Au NRs) are able to effectively kill cancer cells upon high laser doses (usually 808 nm, 1-48 W/cm²) irradiation, leading to hyperthermia-induced destruction of cancer cells, i.e, photothermal therapy (PTT) effects. Combination of Au NRs-mediated PTT and organic photosensitizers-mediated photodynamic therapy (PDT) were also reported to achieve synergistic PTT and PDT effects on killing cancer cells. Herein, we demonstrate for the first time that Au NRs alone can sensitize formation of singlet oxygen (¹O2) and exert dramatic PDT effects on complete destrcution of tumors in mice under very low LED/laser doses of single photon NIR (915 nm, <130 mW/cm²) light excitation. By changing the NIR light excitation wavelengths, Au NRs-mediated phototherapeutic effects can be switched from PDT to PTT or combination of both. Both PDT and PTT effects were confirmed by measurements of reactive oxygen species (ROS) and heat shock protein (HSP 70), singlet oxygen sensor green (SOSG) sensing, and sodium azide quenching in cellular experiments. In vivo mice experiments further show that the PDT effect via irradiation of Au NRs by 915 nm can destruct the B16F0 melanoma tumor in mice far more effectively than doxorubicin (a clinically used anti-cancer drug) as well as the PTT effect (via irradiation of Au NRs by 780 nm light). In addition, we show that Au NRs can emit single photon-induced fluorescence to illustrate their in vivo locations/distribution.

Power-Doppler-based NH002 microbubble sonoporation with chemotherapy relieves hypoxia and enhances the efficacy of chemotherapy and immunotherapy for pancreatic tumors.

Pancreatic ductal adenocarcinoma (PDAC) poses challenges due to late-stage diagnosis and limited treatment response, often attributed to the hypoxic tumor microenvironment (TME). Sonoporation, combining ultrasound and microbubbles, holds promise for enhancing therapy. However, additional preclinical research utilizing commercially available ultrasound equipment for PDAC treatment while delving into the TME's intricacies is necessary. This study investigated the potential of using a clinically available ultrasound system and phase 2-proven microbubbles to relieve tumor hypoxia and enhance the efficacy of chemotherapy and immunotherapy in a murine PDAC model. This approach enables early PDAC detection and blood-flow-sensitive Power-Doppler sonoporation in combination with chemotherapy. It significantly extended treated mice's median survival compared to chemotherapy alone. Mechanistically, this combination therapy enhanced tumor perfusion and substantially reduced tumor hypoxia (77% and 67%, 1- and 3-days post-treatment). Additionally, cluster of differentiation 8 (CD8) T-cell infiltration increased four-fold afterward. The combined treatment demonstrated a strengthening of the anti-programmed death-ligand 1(αPDL1) therapy against PDAC. Our study illustrates the feasibility of using a clinically available ultrasound system with NH-002 microbubbles for early tumor detection, alleviating hypoxic TME, and improving chemotherapy and immunotherapy. It suggests the development of an adjuvant theragnostic protocol incorporating Power-Doppler sonoporation for pancreatic tumor treatment.

A Self-Cascade Penetrating Brain Tumor Immunotherapy Mediated by Near-Infrared II Cell Membrane-Disrupting Nanoflakes via Detained Dendritic Cells.

Immunotherapy can potentially suppress the highly aggressive glioblastoma (GBM) by promoting T lymphocyte infiltration. Nevertheless, the immune privilege phenomenon, coupled with the generally low immunogenicity of vaccines, frequently hampers the presence of lymphocytes within brain tumors, particularly in brain tumors. In this study, the membrane-disrupted polymer-wrapped CuS nanoflakes that can penetrate delivery to deep brain tumors via releasing the cell-cell interactions, facilitating the near-infrared II (NIR II) photothermal therapy, and detaining dendritic cells for a self-cascading immunotherapy are developed. By convection-enhanced delivery, membrane-disrupted amphiphilic polymer micelles (poly(methoxypoly(ethylene glycol)-benzoic imine-octadecane, mPEG-b-C18) with CuS nanoflakes enhances tumor permeability and resides in deep brain tumors. Under low-power NIR II irradiation (0.8 W/cm2), the intense heat generated by well-distributed CuS nanoflakes actuates the thermolytic efficacy, facilitating cell apoptosis and the subsequent antigen release. Then, the positively charged polymer after hydrolysis of the benzoic-imine bond serves as an antigen depot, detaining autologous tumor-associated antigens and presenting them to dendritic cells, ensuring sustained immune stimulation. This self-cascading penetrative immunotherapy amplifies the immune response to postoperative brain tumors but also enhances survival outcomes through effective brain immunotherapy.

Revealing intact neuronal circuitry in centimeter-sized formalin-fixed paraffin-embedded brain.

Tissue-clearing and labeling techniques have revolutionized brain-wide imaging and analysis, yet their application to clinical formalin-fixed paraffin-embedded (FFPE) blocks remains challenging. We introduce HIF-Clear, a novel method for efficiently clearing and labeling centimeter-thick FFPE specimens using elevated temperature and concentrated detergents. HIF-Clear with multi-round immunolabeling reveals neuron circuitry regulating multiple neurotransmitter systems in a whole FFPE mouse brain and is able to be used as the evaluation of disease treatment efficiency. HIF-Clear also supports expansion microscopy and can be performed on a non-sectioned 15-year-old FFPE specimen, as well as a 3-month formalin-fixed mouse brain. Thus, HIF-Clear represents a feasible approach for researching archived FFPE specimens for future neuroscientific and 3D neuropathological analyses.

Photosensitization of singlet oxygen and in vivo photodynamic therapeutic effects mediated by PEGylated W(18)O(49) nanowires.

Upon excitation with near-infrared light (980 nm), PEGylated W18 O49 nanowires can sensitize the formation of singlet oxygen and thus reactive oxygen species (ROS). The resulting photodynamic therapy (PDT) effect can cause the destruction of tumors in the absence of organic photosensitizers. PEG=poly(ethylene glycol), PTT=photothermal therapy.

1550 nm light activatable photothermal therapy on multifunctional CuBi2O4 bimetallic particles for treating drug resistance bacteria-infected skin in the NIR-III biological window.

Nanomaterial mediated phototherapies are believed to be promising candidates to overcome the bacterial drug resistance crisis. However, due to the lack of nanomaterials able to absorb long NIR light, especially in the NIR-III (1500-1850 nm) and -IV (2100-2300 nm) regimes, it was never investigated the utilization of NIR-III and NIR-IV light for in vivo treatments of cancer or bacterial infections. To this end, plasmonic metal-doped transition metal oxides (TMO) are attracting a great attention due to their tunable surface plasmon resonance absorption to the NIR region. Unique features with extendable NIR light absorption of plasmonic metal-doped transition metal oxides make their applications very attractive in several fields, but their utilization for bacterial infection treatments was not yet reported. Moreover, up-to-date bacterial eradication was limited to phototherapies in the NIR-I (700-950 nm) and NIR-II (1000-1350 nm) biological windows (BWs) and has not yet been studied in the NIR-III (1500-1870 nm) BW. To overcome these literature limitations, we engineered NIR-III (1550 nm) light activatable multifunctional plasmonic CuBi2O4 bimetallic particles (i.e., CBO bMPs) with very high molar extinction coefficients (2.75 × 1011 M-1cm-1 @ 808 nm, 2.75 × 1011 M-1cm-1 @ 980 nm, and 3.5 × 1011 M-1cm-1 @1550 nm), able to absorb and convert long NIR (980 and 1550 nm) light energy to thermal heat and generate cytotoxic reactive oxygen species (ROS) for in vivo treatment of drug resistant bacterial infections. Our in vitro and in vivo results reveal that NIR-III (1550 nm) light irradiation of CBO bMPs exerts a remarkable in vivo antibacterial activity via NIR-III photothermal therapy (NIR-III PTT), which is superior than its corresponding NIR-I (808 nm) PTT and NIR-II photodynamic therapy (NIR-II PDT, 980 nm). We observed that hyperthermia-based photothermal therapy is more effective than ROS-based photodynamic therapy in killing multi-drug resistant bacteria. We also show that CBO bMPs also show an enzyme oxidase and peroxidase like activity, which is an additional asset to enhance the therapeutic efficiency.

Combined Gadolinium and Boron Neutron Capture Therapies for Eradication of Head-and-Neck Tumor Using Gd10B6 Nanoparticles under MRI/CT Image Guidance.

Eradication of head-and-neck (H&N) tumors is very difficult and challenging because of the characteristic feature of frequent recurrence and the difficulty in killing cancer stem cells. Neutron capture therapy (NCT) is emerging as a noninvasive potential modality for treatments of various types of tumors. Herein, we report that 98.5% 10B-enriched anti-EGFR-Gd10B6 nanoparticles can not only deliver large doses of 158 µg 10B/g tumor tissues as well as 56.8 µg 157Gd/g tumor tissues with a very high tumor-to-blood (T/B) 10B ratio of 4.18, but also exert very effective CT/MRI image-guided combined GdBNCT effects on killing cancer stem cells and eradication of recurrent head-and-neck (H&N) tumors. This leads to a long average half-lifespan of 81 days for H&N tumor-bearing mice, which is a record-making result, and surpasses the best result reported in the literature using combined radiotherapy and T cell-mediated immunotherapy (70 d).

Engineering a potent boron-10-enriched polymeric nanoparticle for boron neutron capture therapy.

Background: Boron neutron capture therapy (BNCT) is a promising cancer treatment that eliminates tumor cells by triggering high-energy radiation within cancer cells. Aim: In vivo evaluation of poly(vinyl alcohol)/boric acid crosslinked nanoparticles (PVA/BA NPs) for BNCT. Materials & methods: PVA/BA NPs were synthesized and intravenously injected into tumor-bearing mice for BNCT. Results: The in vitro boron uptake of PVA/BA NPs in tumor cells was 70-fold higher than the required boron uptake for successful BNCT. In an in vivo study, PVA/BA NPs showed a 44.29% reduction in tumor size compared with clinically used boronophenylalanine for oral cancer in a murine model. Conclusion: PVA/BA NPs exhibited effective therapeutic results for oral cancer treatments in BNCT.

Targeting M-MDSCs enhances the therapeutic effect of BNCT in the 4-NQO-induced murine head and neck squamous cell carcinoma model.

Purpose: Malignant head and neck squamous cell carcinoma (HNSCC) is characterized by a poor prognosis and resistance to conventional radiotherapy. Infiltrating myeloid-derived suppressive cells (MDSCs) is prominent in HNSCC and is linked to immune suppression and tumor aggressiveness. This study aimed to investigate the impact of boron neutron capture therapy (BNCT) on the MDSCs in the tumor microenvironment and peripheral blood and to explore the potential for MDSCs depletion combined with BNCT to reactivate antitumor immunity. Methods and materials: Carcinogen, 4-NQO, -induced oral tumors were irradiated with a total physical dose of 2 Gy BNCT in Tsing Hua Open Reactor (THOR). Flow cytometry and immunohistochemistry accessed the dynamics of peripheral MDSCs and infiltrated MDSCs within the tumor microenvironment. Mice were injected with an inhibitor of CSF-1 receptor (CSF-1R), PLX3397, to determine whether modulating M-MDSCs could affect mice survival after BNCT. Results: Peripheral CD11b+Ly6ChighLy6G- monocytic-MDSCs (M-MDSCs), but not CD11b+Ly6CloLy6Ghigh polymorphonuclear-MDSCs (PMN-MDSCs), increased as tumor progression. After BNCT treatment, there were temporarily decreased and persistent increases of M-MDSCs thereafter, either in peripheral blood or in tumors. The administration of PLX-3397 hindered BNCT-caused M-MDSCs infiltration, prolonged mice survival, and activated tumor immunity by decreasing tumor-associated macrophages (TAMs) and increasing CD8+ T cells. Conclusion: M-MDSCs were recruited into 4-NQO-induced tumors after BNCT, and their number was also increased in peripheral blood. Assessment of M-MDSCs levels in peripheral blood could be an index to determine the optimal intervention window. Their temporal alteration suggests an association with tumor recurrence after BNCT, making M-MDSCs a potential intervention target. Our preliminary results showed that PLX-3397 had strong M-MDSCs, TAMs, and TIL (tumor-infiltrating lymphocyte) modulating effects that could synergize tumor control when combined with BNCT.

Tumor-secreted SDF-1 promotes glioma invasiveness and TAM tropism toward hypoxia in a murine astrocytoma model.

A distinguishing feature of high-grade gliomas is the infiltration of neoplastic cells into adjacent brain tissues that mark most of these tumors surgically incurable. To study the factors associated with tumor invasion, we established a new murine brain tumor model, ALTS1C1 derived from SV40 large T antigen-transfected astrocytes. This new brain tumor model recapitulates several histopathological features of human high-grade glioma including increased cellularity, prominent cellular pleomorphism, geographic necrosis, active mitosis, and extensive invasion of tumor cells into adjacent brain tissues. More importantly, ALTS1C1 expressed a relatively high level of stromal-derived factor-1 (SDF-1/CXCL12) in vitro and in vivo and higher microvascular density (MVD) in vivo. To define the roles of SDF-1 in this tumor model, the expression of SDF-1 in ALTS1C1 cells was inhibited by specific siRNA. SDF-knockdown ALTS1C1 (SDF(kd)) cells took longer than parental ALTS1C1 cells to form tumors and in contrast to the wild-type tumors they had well-defined regular borders and lacked infiltration tracts. The SDF(kd) tumors were also associated with a lower MVD and more hypoxic areas. In contrast to parental tumors, the density of F4/80-positive tumor-associated macrophages (TAMs) in SDF(kd) tumor was higher in non-hypoxic than in hypoxic regions. SDF-1 production by tumor cells therefore seems critical for the aggregation of TAMs into areas of hypoxia and tumor invasiveness. This study not only provides new insight into the role of SDF-1 in brain tumor invasion and the relationship between TAMs and hypoxia, but also provides a new preclinical brain tumor model for designing new treatment options for invasive cases.