Functional inhibition of the RNA-binding protein HuR sensitizes triple-negative breast cancer to chemotherapy

Chemotherapy remains the standard treatment for triple-negative breast cancer (TNBC); however, chemoresistance compromises its efficacy. The RNA-binding protein Hu antigen R (HuR) could be a potential therapeutic target to enhance the chemotherapy efficacy. HuR is known to mainly stabilize its target mRNAs, and/or promote the translation of encoded proteins, which are implicated in multiple cancer hallmarks, including chemoresistance. In this study, a docetaxel-resistant cell subline (231-TR) was established from the human TNBC cell line MDA-MB-231. Both the parental and resistant cell lines exhibited similar sensitivity to the small molecule functional inhibitor of HuR, KH-3. Docetaxel and KH-3 combination therapy synergistically inhibited cell proliferation in TNBC cells and tumor growth in three animal models. KH-3 downregulated the expression levels of HuR targets (e.g., β-Catenin and BCL2) in a time- and dose-dependent manner. Moreover, KH-3 restored docetaxel's effects on activating Caspase-3 and cleaving PARP in 231-TR cells, induced apoptotic cell death, and caused S-phase cell cycle arrest. Together, our findings suggest that HuR is a critical mediator of docetaxel resistance and provide a rationale for combining HuR inhibitors and chemotherapeutic agents to enhance chemotherapy efficacy.

Dose-Dependent Suppression of Human Glioblastoma Xenograft Growth by Accelerator-Based Boron Neutron Capture Therapy with Simultaneous Use of Two Boron-Containing Compounds

Simple Summary

Accelerator-based boron neutron capture therapy (BNCT) has opened up new perspectives in increasing cancer treatment efficacy, including malignant brain tumors and particularly glioblastoma. We studied dosimetry control optimization, neutron beam parameter adjustment, and two boron compound combinations (along with single and double irradiation regimens) to assess safety and increase therapy efficacy, using a U87MG xenotransplant immunodeficient mouse model. In two sets of experiments, we achieved increases in tumor-growth inhibition (to 80–83%), a neutron capture therapy ratio of 2:1 (two times higher neutron capture therapy efficacy than neutron irradiation without boron), and increases in animal life expectancy, from 9 to 107 days, by treatment parameter adjustment. These results will contribute to the development of clinical-trial protocols for accelerator-based BNCT and further innovations in this cancer treatment method.

Abstract

(1) Background: Developments in accelerator-based neutron sources moved boron neutron capture therapy (BNCT) to the next phase, where new neutron radiation parameters had to be studied for the treatment of cancers, including brain tumors. We aimed to further improve accelerator-BNCT efficacy by optimizing dosimetry control, beam parameters, and combinations of boronophenylalanine (BPA) and sodium borocaptate (BSH) administration in U87MG xenograft-bearing immunodeficient mice with two different tumor locations. (2) Methods: The study included two sets of experiments. In Experiment #1, BPA only and single or double irradiation in higher doses were used, while, in Experiment #2, BPA and BSH combinations and single or double irradiation with dosage adjustment were analyzed. Mice without treatment or irradiation after BPA or BPA+BSH injection were used as controls. (3) Results: Irradiation parameter adjustment and BPA and BSH combination led to 80–83% tumor-growth inhibition index scores, irradiation:BNCT ratios of 1:2, and increases in animal life expectancy from 9 to 107 days. (4) Conclusions: Adjustments in dosimetry control, calculation of irradiation doses, and combined use of two ¹⁰B compounds allowed for BNCT optimization that will be useful in the development of clinical-trial protocols for accelerator-based BNCT.

The Expression Profile of mRNA and tRNA Genes in Splenocytes and Neutrophils after In Vivo Delivery of Antitumor Short Hairpin RNA of Indoleamine 2,3- Dioxygenase

RNA-based therapeutics are considered as novel treatments for human diseases. Our previous study demonstrated that treatment with short-hairpin RNA against Ido1 (IDO shRNA) suppresses tumor growth, detects Th1-bias immune responses, and elevates expression of tryptophan transfer RNA (tRNA^Trp) in total splenocytes. In addition, depletion of Ly6g⁺ neutrophils attenuates the effect of IDO shRNA. The aim of this study was to investigate the regulatory network and the expression profile of tRNAs and other non-coding RNAs in IDO shRNA-treated spleens. The total splenocytes and magnetic bead-enriched splenic neutrophils were collected from the lung tumor bearing mice, which were treated with IDO shRNA or scramble IDO shRNA, and the collected cells were subsequently subjected to RNA sequencing. The gene ontology analysis revealed the different enrichment pathways in total splenocytes and splenic neutrophils. Furthermore, the expression of tRNA genes was identified and validated. Six isoacceptors of tRNA, with different expression patterns between total splenocytes and splenic neutrophils, were observed. In summary, our findings not only revealed novel biological processes in IDO shRNA-treated total splenocytes and splenic neutrophils, but the identified tRNAs and other non-coding RNAs may contribute to developing a novel biomarker gene set for evaluating the clinical efficiency of RNA-based cancer immunotherapies.

Antitumor effect of combination of hyperthermotherapy and 5-aminolevulinic acid (ALA)

BACKGROUND

5-Aminolevulinic acid (ALA) is a precursor of heme. ALA is used as a photosensitive substance in photodynamic diagnosis (PDD) and photodynamic therapy (PDT) because heme metabolism is abnormal in tumor cells and a photosensitive metabolite of heme synthesis from ALA, protoporphyrin IX (PpIX), specifically accumulates in tumors. We investigated the enhancement of the antitumor effect by combination of ALA and hyperthermotherapy (HT) using a transplanted tumor model with Lewis lung carcinoma cells (3LL) in mice.

MATERIALS AND METHODS

Animals were divided into four test groups: control (untreated), HT, and HT plus ALA (100 or 300 mg/kg) groups, and HT by bathing at 43°C for 20 min was performed at five days after transplantation. ALA was administered once at the above doses three hours before HT by intraperitoneal injection.

RESULTS

The tumor sizes at five days after HT were 5.2- and 2.6-times greater than those at the time of HT in the control and HT groups, respectively. In contrast, PpIX accumulation in the tumor region was noted three hours after ALA administration, the HT+ALA group given at 100 or 300 mg/kg of ALA inhibited tumor growth to 1.3- and 1.1-times increases in the tumor size.

CONCLUSION

Therefore, ALA administration markedly enhanced the tumor growth-inhibitory effect of HT.

PDGF and PDGF receptors in glioma

The family of platelet-derived growth factors (PDGFs) plays a number of critical roles in normal embryonic development, cellular differentiation, and response to tissue damage. Not surprisingly, as it is a multi-faceted regulatory system, numerous pathological conditions are associated with aberrant activity of the PDGFs and their receptors. As we and others have shown, human gliomas, especially glioblastoma, express all PDGF ligands and both the two cell surface receptors, PDGFR-α and -β. The cellular distribution of these proteins in tumors indicates that glial tumor cells are stimulated via PDGF/PDGFR-α autocrine and paracrine loops, while tumor vessels are stimulated via the PDGFR-β. Here we summarize the initial discoveries on the role of PDGF and PDGF receptors in gliomas and provide a brief overview of what is known in this field.

SDF1/CXCL12 is involved in recruitment of stem-like progenitor cells to orthotopic murine malignant mesothelioma spheroids

BACKGROUND/AIM

Tumor progression is influenced by the microenvironment. We found stem cells are recruited to malignant mesothelioma spheroids. We aimed to determine if stem cell recruitment depends on the chemokine SDF1, and if inhibition of the cognate receptor CXCR4 affects tumor growth.

MATERIALS AND METHODS

The kinetics of stem cell recruitment was determined using immunofluorescence staining, BrdU incorporation and eGFP transgenic mice. Chemokines were identified using PCR array. Inhibitors of CXCR4 were used to determine the effect on cell migration and tumor progression.

RESULTS

The increasing number of stem cells found in tumor spheroids over time is attributed to cell recruitment. Stem cell migration in vitro was enhanced by exogenous SDF1 and abrogated by CXCR4 inhibition and. CXCR4 inhibition reduced tumor burden in vivo.

CONCLUSION

SDF1 is a candidate chemokine for recruitment of stem cells to malignant peritoneal mesothelioma and a potential target for therapy.