Targeted radiotherapy potentiates the cytotoxicity of a novel anti-human DR5 monoclonal antibody and the adenovirus encoding soluble TRAIL in prostate cancer

Significance of TRAIL/Apo-2 ligand and its death receptors in apoptosis and necroptosis signalling: Implications for cancer-targeted therapeutics

The human immune defensesystem routinely expresses the tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), which is the most prevalent element for antitumor immunity. TRAIL associates with its death receptors (DRs), DR4 (TRAIL-R1), and DR5 (TRAIL-R2), in cancer cells to initiate the intracellular apoptosis cascade. Accordingly, numerous academic institutions and pharmaceutical companies havetried to exploreTRAIL's capacity to kill tumourcells by producing recombinant versions of it (rhTRAIL) or TRAIL receptor agonists (TRAs) [monoclonal antibody (mAb), synthetic and natural compounds, etc.] and molecules that sensitize TRAIL signalling pathway for therapeutic applications. Recently, several microRNAs (miRs) have been found to activate or inhibit death receptor signalling. Therefore, pharmacological regulation of these miRs may activate or resensitize the TRAIL DRs signal, and this is a novel approach for developing anticancer therapeutics. In this article, we will discuss TRAIL and its receptors and molecular pathways by which it induces various cell death events. We will unravel potential innovative applications of TRAIL-based therapeutics, and other investigated therapeutics targeting TRAIL-DRs and summarize the current preclinical pharmacological studies and clinical trials. Moreover, we will also emphasizea few situations where future efforts may be addressed to modulate the TRAIL signalling pathway.

Potential of Gold Nanoparticle in Current Radiotherapy Using a Co-Culture Model of Cancer Cells and Cancer Associated Fibroblast Cells

Simple Summary

Many cancer therapeutics do not account for the complexity of the tumor microenvironment (TME), which may result in failure when applied clinically. In this paper we utilized a simple tumor model made of two types of pancreatic cancer cells that contribute to the tumor environment, i.e., cancer cells and cancer associated fibroblasts. Herein, radiotherapy along with radiosensitizing gold nanoparticles were used to test the efficacy of a co-culture vs. monoculture model. The results show that the co-culture model exhibited heightened resistance to radiation. Furthermore, we found that the combination of gold radiosensitizers with radiotherapy reduced the radioresistance of the co-culture model compared to radiotherapy alone. This study demonstrates the potential of using nanotherapeutics in targeting the complex tumor microenvironment.

Abstract

Many cancer therapeutics are tested in vitro using only tumour cells. However, the tumour promoting effect of cancer associated fibroblasts (CAFs) within the tumour microenvironment (TME) is thought to reduce cancer therapeutics’ efficacy. We have chosen pancreatic ductal adenocarcinoma (PDAC) as our tumor model. Our goal is to create a co-culture of CAFs and tumour cells to model the interaction between cancer and stromal cells in the TME and allow for better testing of therapeutic combinations. To test the proposed co-culture model, a gold nanoparticle (GNP) mediated-radiation response was used. Cells were grown in co-culture with different ratios of CAFs to cancer cells. MIA PaCa-2 was used as our PDAC cancer cell line. Co-cultured cells were treated with 2 Gy of radiation following GNP incubation. DNA damage and cell proliferation were examined to assess the combined effect of radiation and GNPs. Cancer cells in co-culture exhibited up to a 23% decrease in DNA double strand breaks (DSB) and up to a 35% increase in proliferation compared to monocultures. GNP/Radiotherapy (RT) induced up to a 25% increase in DNA DSBs and up to a 15% decrease in proliferation compared to RT alone in both monocultured and co-cultured cells. The observed resistance in the co-culture system may be attributed to the role of CAFs in supporting cancer cells. Moreover, we were able to reduce the activity of CAFs using GNPs during radiation treatment. Indeed, CAFs internalize a significantly higher number of GNPs, which may have led to the reduction in their activity. One reason experimental therapeutics fail in clinical trials relates to limitations in the pre-clinical models that lack a true representation of the TME. We have demonstrated a co-culture platform to test GNP/RT in a clinically relevant environment.

First-in-human DR5 PET reveals insufficient DR5 expression in patients with gastrointestinal cancer

BACKGROUND

Death receptor 5 (DR5) is a promising therapeutic target for cancer therapy. However, many clinical trials of DR5 agonists failed to show significant therapeutic efficacy in patients with cancer. The study aimed to investigate the feasibility of using ⁸⁹Zr-CTB006 positron emission tomography (PET) for noninvasive imaging of DR5 expression in preclinical models and patients with gastrointestinal (GI) cancers.

METHODS

Balb/c, Sp2/0 xenograft and patient-derived tumor xenograft were employed for micro-PET/CT imaging in vivo. In the clinical study, patients with GI cancers planning to undergo surgical operation were enrolled and underwent ¹⁸F-FDG and ⁸⁹Zr-CTB006 PET/CT. The tumor tissues were obtained through surgical operation and DR5 expression levels were confirmed by RNAscope.

RESULTS

Preclinical studies showed that ⁸⁹Zr-CTB006 PET could specifically detect DR5 expression levels in vivo. Twenty-one patients, including nine gastric cancers and 12 colorectal cancers, were enrolled. The biodistribution showed high uptake in the liver and spleen and low uptake in the brain, lung and muscle with an acceptable whole-body dosimetry of 0.349 mSv/MBq. Strikingly, the adrenal glands maintained stable high uptake over the entire examination in all patients. The tumor lesions showed different levels of uptake of ⁸⁹Zr-CTB006 with a mean maximum standardized uptake value (SUV_max) of 6.63±3.29 (range 1.8-13.8). Tumor tissue was obtained from 18 patients, and ⁸⁹Zr-CTB006 uptake in patients with RNAscope scores of 3-4 was significantly higher than that in patients with scores of 0-2. An SUV_max of 9.3 at 48 hours and 6.3 at 72 hours could be used to discriminate the DR5 expression status of tumors both with a sensitivity and specificity of 100% and 92.9%, respectively.

CONCLUSIONS

⁸⁹Zr-CTB006 PET/CT is capable of detecting DR5 expression in cancer patients and is a promising approach to screen patients with DR5 overexpression.

Atorvastatin Enhances Inhibitory Effects of Irradiation on Tumor Growth by Reducing MSH2 Expression both in Prostate Cancer Cells and Xenograft Tumor Models

BACKGROUND

Prostate cancer (PCa) is the fourth most common tumor in males.

OBJECTIVE

To investigate effects of atorvastatin (AS) on PCa cells proliferation and clarify the associated mechanisms.

METHODS

PCa cell lines were cultured and treated with irradiation (IR) (4 Gy), AS (6 μg/ml), transfected with Bcl-2 siRNA, and then divided into different groups. Xenograft tumor mouse model was established. Bcl-2 and MSH2 gene transcription and protein expression were evaluated using RT-PCR assay and western blot assay. Plate clone formation assay was employed to examine colony formation. MTT assay was used to detect cell viabilities. Flow cytometry analysis was utilized to verify apoptosis. Co-immunoprecipitation and immuno-fluorescence assay were used to identify interaction between Bcl-2 and MSH2.

RESULTS

IR significantly reduced colony formation, enhanced Bcl-2 and reduced MSH2 gene transcription in PCa cells compared to un-treated cells (p<0.05). AS significantly strengthened radio-therapeutic effects of IR on colony formation, decreased cell apoptosis and increased Bcl-2 gene transcription/protein expression in PCa cells compared to single IR treatment cells (p<0.05). AS combining IR down-regulated MSH2 gene transcription/protein expression in PCa cells compared to single IR treatment cells (p<0.05). Bcl-2 interacted with MSH2 both in PCa cells and tumor tissues administrating with AS. AS enhanced reductive effects of IR on tumor size of Xenograft tumor mice.

CONCLUSION

Atorvastatin administration enhanced inhibitory effects of IR either on PCa cells or on tumor size of Xenograft tumor mice. The inhibitory effects of atorvastatin were mediated by reducing MSH2 expression and triggering interaction between Bcl-2 and MSH2, both in vitro and in vivo levels.

Toll-like receptor 9 activation by CpG oligodeoxynucleotide 7909 enhances the radiosensitivity of A549 lung cancer cells via the p53 signaling pathway

Unmethylated cytosine-phosphorothioate-guanine (CpG)-containing oligodeoxynucleotides (ODNs) are synthetic DNA sequences that mimic bacterial DNA, and are known to serve as ligands for Toll-like receptor 9 (TLR9). The interaction between a CpG ODNs with TLR9 activates the complex downstream cascade that contributes to exerting its function. In the present study, the results of clonogenic assays demonstrated that the activation of TLR9 by CpG ODNs significantly increased the radiosensitivity of A549 lung cancer cells, with a sensitivity enhancement ratio (SER) of 1.28. When the expression of TLR9 was effectively silenced, CpG ODNs used alone were identified to produce SERs as low as 1.01. Flow cytometry demonstrated that the interaction between TLR9 and CpG ODN 7909 alone did not significantly affect the rate of apoptosis, but may significantly enhance the radiation-induced apoptosis of A549 cells. Western blot analysis revealed that TLR9 activation by CpG ODN 7909 increased the levels of mitogen-activated protein kinase 14, cellular tumor antigen p53, B-cell lymphoma 2 associated X protein and genome polyprotein, and decreased Bcl-2 expression levels, whereas these effects were not observed in CpG ODN 7909-treated cells in which TLR9 was knocked down. These results suggest that CpG ODN 7909 may enhance radiosensitivity through TLR9 activation, and partially via the p53 pathway in A549 lung cancer cells.

Natural Agents-Mediated Targeting of Histone Deacetylases

In the past few years, basic and clinical scientists have witnessed landmark achievements in many research projects, such as those conducted by the US National Institutes of Health Roadmap Epigenomics Mapping Consortium, the International Human Epigenome Consortium, The Cancer Genome Atlas Network and the International Cancer Genome Consortium, which have provided near-complete resolution of epigenetic landscape in different diseases. Furthermore, genome sequencing of tumors has provided compelling evidence related to frequent existence of mutations in readers, erasers and writers of epigenome in different cancers. Histone acetylation is an intricate mechanism modulated by two opposing sets of enzymes and deeply studied as a key biological phenomenon in 1964 by Vincent Allfrey and colleagues. The research group suggested that this protein modification contributed substantially in transcriptional regulation. Subsequently, histone deacetylases (HDACs), histone acetyltransferases and acetyl-Lys-binding proteins were identified as transcriptional mediators, which further deepened our comprehension regarding biochemical modifications. Overwhelmingly increasing high-impact research is improving our understanding of this molecularly controlled mechanism; moreover, quantification and identification of lysine acetylation by mass spectrometry has added new layers of information. We partition this multi-component review into how both activity and expression of HDAC are targeted using natural agents. We also set spotlight on how oncogenic fusion proteins tactfully utilize HDAC-associated nano-machinery to modulate expression of different genes and how HDAC inhibitors regulate TRAIL-induced apoptosis in cancer cells. HDAC inhibitors have been reported to upregulate expression of TRAIL receptors and protect TRAIL from proteasomal degradation. Deeper understanding of HDAC biology will be useful for stratification and selection of patients who are responders, non-responders and poor-responders for HDACi therapy, and for the rational design of combination studies using HDACi.

Journey of TRAIL from Bench to Bedside and its Potential Role in Immuno-Oncology

Induction of apoptosis in cancer cells has increasingly been the focus of many therapeutic approaches in oncology field. Since its identification as a TNF family member, TRAIL (TNF-related apoptosis-inducing ligand) paved a new path in apoptosis inducing cancer therapies. Its selective ability to activate extrinsic and intrinsic cell death pathways in cancer cells only, independently from p53 mutations responsible for conventional therapeutics resistance, spotted TRAIL as a potent cancer apoptotic agent. Many recombinant preparations of TRAIL and death receptor targeting monoclonal antibodies have been developed and being tested pre-clinically and clinically both as a single agent and in combinations. Of note, the monoclonal antibodies were not the only type of antibodies developed to target TRAIL receptors. Recent technology has brought forth several single chain variable domains (scFv) designs fused recombinantly to TRAIL as well. Also, it is becoming progressively more understandable that field of nanotechnology has revolutionized cancer diagnosis and therapy. The recent breakthroughs in materials science and protein engineering have helped considerably in strategically loading drugs into nanoparticles or conjugating drugs to their surface. In this review we aim to comprehensively highlight the molecular knowledge of TRAIL in the context of its pathway, receptors and resistance factors. We also aim to review the clinical trials that have been done using TRAIL based therapies and to review various scFv designs, the arsenal of nano-carriers and molecules available to selectively target tumor cells with TRAIL.

Survivin a radiogenetic promoter for glioblastoma viral gene therapy independently from CArG motifs

Background

Radiogenetic therapy is a novel approach in the treatment of cancer, which employs genetic modification to alter the sensitivity of tumor cells to the effect of applied radiation.

Aim

To select a potent radiation inducible promoter in the context of brain tumors and to investigate if CArG radio responsive motifs or other elements in the promoter nucleotide sequences can correlate to its response to radiation.

Methods

To select initial candidates for promoter inducible elements, the levels of mRNA expression of six different promoters were assessed using Quantitative RTPCR in D54 MG cells before and after radiation exposure. Recombinant Ad/reporter genes driven by five different promoters; CMV, VEGF, FLT-1, DR5 and survivin were constructed. Glioma cell lines were infected with different multiplicity of infection of the (promoter) Ad or CMV Ad. Cells were then exposed to a range of radiation (0–12 Gy) at single fraction. Fluorescent microscopy, Luc assay and X-gal staining was used to detect the level of expression of related genes. Different glioma cell lines and normal astrocytes were infected with Ad survivin and exposed to radiation. The promoters were analyzed for presence of CArG radio-responsive motifs and CCAAT box consensus using NCBI blast bioinformatics software.

Results

Radiotherapy increases the expression of gene expression by 1.25–2.5 fold in different promoters other than survivin after 2 h of radiation. RNA analysis was done and has shown an increase in copy number of tenfold for survivin. Most importantly cells treated with RT and Ad Luc driven by survivin promoter showed a fivefold increase in expression after 2 Gy of radiation in comparison to non-irradiated cells. Presence or absence of CArG motifs did not correlate with promoter response to radiation. Survivin with the best response to radiation had the lowest number of CCAAT box.

Conclusion

Survivin is a selective potent radiation inducible promoter for glioblastoma viral gene therapy and this response to radiation could be independent of CArG motifs.

Role of nanotechnology and gene delivery systems in TRAIL-based therapies

Since its identification as a member of the tumour necrosis factor (TNF) family, TRAIL (TNF-related apoptosis-inducing ligand) has emerged as a new avenue in apoptosis-inducing cancer therapies. Its ability to circumvent the chemoresistance of conventional therapeutics and to interact with cancer stem cells (CSCs) self-renewal pathways, amplified its potential as a cancer apoptotic agent. Many recombinant preparations of this death ligand and monoclonal antibodies targeting its death receptors have been tested in monotherapy and combinational clinical trials. Gene therapy is a new approach for cancer treatment which implies viral or non-viral functional transgene induction of apoptosis in cancer cells or repair of the underlying genetic abnormality on a molecular level. The role of this approach in overcoming the traditional barriers of radiation and chemotherapeutics systemic toxicity, risk of recurrence, and metastasis made it a promising platform for cancer treatment. The recent first Food Drug Administration (FDA) approved oncolytic herpes virus for melanoma treatment brings forth the potency of the cancer gene therapy approach in the future. Many gene delivery systems have been studied for intratumoural TRAIL gene delivery alone or in combination with chemotherapeutic agents to produce synergistic cancer cytotoxicity. However, there still remain many obstacles to be conquered for this different gene delivery systems. Nanomedicine on the other hand offers a new frontier for clinical trials and biomedical research. The FDA approved nanodrugs motivates horizon exploration for other nanoscale designed particles’ implications in gene delivery. In this review we aim to highlight the molecular role of TRAIL in apoptosis and interaction with cancer stem cells (CSCs) self-renewal pathways. Finally, we also aim to discuss the different roles of gene delivery systems, mesenchymal cells, and nanotechnology designs in TRAIL gene delivery.