Fenofibrate enhances radiosensitivity of esophageal squamous cell carcinoma by suppressing hypoxia-inducible factor-1α expression

Metabolic Rewiring in Radiation Oncology Toward Improving the Therapeutic Ratio

To meet the anabolic demands of the proliferative potential of tumor cells, malignant cells tend to rewire their metabolic pathways. Although different types of malignant cells share this phenomenon, there is a large intracellular variability how these metabolic patterns are altered. Fortunately, differences in metabolic patterns between normal tissue and malignant cells can be exploited to increase the therapeutic ratio. Modulation of cellular metabolism to improve treatment outcome is an emerging field proposing a variety of promising strategies in primary tumor and metastatic lesion treatment. These strategies, capable of either sensitizing or protecting tissues, target either tumor or normal tissue and are often focused on modulating of tissue oxygenation, hypoxia-inducible factor (HIF) stabilization, glucose metabolism, mitochondrial function and the redox balance. Several compounds or therapies are still in under (pre-)clinical development, while others are already used in clinical practice. Here, we describe different strategies from bench to bedside to optimize the therapeutic ratio through modulation of the cellular metabolism. This review gives an overview of the current state on development and the mechanism of action of modulators affecting cellular metabolism with the aim to improve the radiotherapy response on tumors or to protect the normal tissue and therefore contribute to an improved therapeutic ratio.

Genome-wide RNA-sequencing dataset reveals the prognostic value and potential molecular mechanisms of lncRNA in non-homologous end joining pathway 1 in early stage Pancreatic Ductal Adenocarcinoma

Objective: Our current study is to explore the prognostic value and molecular mechanisms underlying the role of lncRNA in non-homologous end joining pathway 1 (LINP1) in early stage pancreatic ductal adenocarcinoma (PDAC).

Methods: Genome-wide RNA-seq datasets of 112 early stage PDAC patients were got from The Cancer Genome Atlas and analyzed using multiple online tools.

Results: Overall survival in high LINP1 expression patients was shorter than those with low expression (high-LINP1 vs. low-LINP1=481 vs. 592 days, log-rank P=0.0432). The multivariate Cox proportional hazard regression model suggested that high-LINP1 patients had a markedly higher risk of death than low-LINP1 patients (adjusted P=0.004, hazard ratio=2.214, 95% confidence interval=1.283-3.820). Analysis of genome-wide co-expressed genes, screening of differentially expressed genes, and gene set enrichment analysis indicated that LINP1 may be involved in the regulation of cell proliferation-, cell adhesion- and cell cycle-related biological processes in PDAC. Six small-molecule compounds including STOCK1N-35874, fenofibrate, exisulind, NU-1025, vinburnine, and doxylamine were identified as potential LINP1-targeted drugs for the treatment of PDAC.

Conclusions: Our study indicated that LINP1 may serve as a prognostic biomarker of early stage PDAC. Analysis of genome-wide datasets led to the elucidation of the underlying mechanisms and identified six potential targeted drugs for the treatment of early PDAC.

Synergy Between Low Dose Metronomic Chemotherapy and the pH-centered Approach Against Cancer

Low dose metronomic chemotherapy (MC) is becoming a mainstream treatment for cancer in veterinary medicine. Its mechanism of action is anti-angiogenesis by lowering vascular endothelial growth factor (VEGF) and increasing trombospondin-1 (TSP1). It has also been adopted as a compassionate treatment in very advanced human cancer. However, one of the main limitations of this therapy is its short-term effectiveness: 6 to 12 months, after which resistance develops. pH-centered cancer treatment (pHT) has been proposed as a complementary therapy in cancer, but it has not been adopted or tested as a mainstream protocol, in spite of existing evidence of its advantages and benefits. Many of the factors directly or indirectly involved in MC and anti-angiogenic treatment resistance are appropriately antagonized by pHT. This led to the testing of an association between these two treatments. Preliminary evidence indicates that the association of MC and pHT has the ability to reduce anti-angiogenic treatment limitations and develop synergistic anti-cancer effects. This review will describe each of these treatments and will analyze the fundamentals of their synergy.

Alpinumisoflavone radiosensitizes esophageal squamous cell carcinoma through inducing apoptosis and cell cycle arrest

Radiotherapy remains a mainstream treatment for patients with unresectable and locally advanced esophageal squamous cell carcinoma (ESCC). However, intrinsic radioresistance of ESCC tumors has largely compromised the efficacy of radiotherapy. The following study investigates the potential radiosensitizing effect of alpinumisoflavone (AIF) and explores its underlying mechanisms in ESCC. Briefly, our results showed that AIF could significantly increase radiosensitivity of ESCC cells both in vitro and in vivo, by increasing the effect of AIF on irradiation-induced DNA damage, apoptosis and cell cycle arrest. Mechanically, AIF aggravated irradiation-induced ROS generation in ESCC cells, which occurred via suppressing the expression of nuclear transcription factor Nrf2 and Nrf2-driven antioxidant molecule NQO-1 and HO-1. Collectively, we concluded that AIF functions as a potent radiosensitizer in human ESCC.

Activation of PPARα by clofibrate sensitizes pancreatic cancer cells to radiation through the Wnt/β-catenin pathway

Radiotherapy is emerging as an important modality for the local control of pancreatic cancer, but pancreatic cancer cell radioresistance remains a serious concern. Peroxisome proliferator-activated receptor α (PPARα) is a member of the PPAR nuclear hormone receptor superfamily, which can be activated by fibrate ligands. The clinical relevance of PPARα and its biological function in pancreatic cancer radiosensitivity have not been previously described. In this study, we examined PPARα expression in tissue samples of pancreatic cancer patients. We found significantly higher expression of PPARα in pancreatic cancer tissues than in tumor-adjacent tissues and that the PPARα expression level is inversely associated with higher overall patient survival rate. We further observed that PPARα activation by its agonist clofibrate sensitizes pancreatic cancer cells to radiation by modulating cell cycle progression and apoptosis in several pancreatic cancer cell lines. Small interfering RNA-mediated PPARα silencing and PPARα blockade by the antagonist GW6471 abolish the effect of clofibrate on radiosensitization. An in vivo study showed that PANC1 xenografts treated with clofibrate are more sensitive to radiation than untreated xenografts. mRNA profiling by microarray analysis revealed that the expression of PTPRZ1 and Wnt8a, two core components of the β-catenin pathway, is downregulated by clofibrate. Chromatin immunoprecipitation analysis confirmed that clofibrate abrogates the binding of nuclear factor-κB to the PTPRZ1 and Wnt8a promoters, ultimately decreasing Wnt/β-catenin signaling activity, which is associated with radiosensitivity. Overall, we demonstrate that PPARα is overexpressed in pancreatic cancer tissues and clofibrate-mediated PPARα activation sensitizes pancreatic cancer cells to radiation through the Wnt/β-catenin pathway.

Hypoxia and hypoxia response-associated molecular markers in esophageal cancer: A systematic review

PURPOSE

In this systematic review, the existing evidence of available hypoxia-associated molecular response biomarkers in esophageal cancer (EC) patients is summarized and set into the context of the role of hypoxia in the prediction of esophageal cancer, treatment response and treatment outcome.

METHODS

A systematic literature search was performed in Web of Science, MEDLINE, and PubMed databases using the keywords: hypoxia, esophagus, cancer, treatment outcome and treatment response. Eligible publications were independently evaluated by two reviewers. In total, 22 out of 419 records were included for systematic review. The described search strategy was applied weekly, with the last update being performed on April 3rd, 2017.

RESULTS

In esophageal cancer, several (non-)invasive biomarkers for hypoxia could be identified. Independent prognostic factors for treatment response include HIF-1α, CA IX, GLUT-1 overexpression and elevated uptake of the PET-tracer ¹⁸F-fluoroerythronitroimidazole (¹⁸F-FETNIM). Hypoxia-associated molecular responses represents a clinically relevant phenomenon in esophageal cancer and detection of elevated levels of hypoxia-associated biomarkers and tends to be associated with poor treatment outcome (i.e., overall survival, disease-free survival, complete response and local control).

CONCLUSION

Evaluation of tumor micro-environmental conditions, such as intratumoral hypoxia, is important to predict treatment outcome and efficacy. Promising non-invasive imaging-techniques have been suggested to assess tumor hypoxia and hypoxia-associated molecular responses. However, extensive validation in EC is lacking. Hypoxia-associated markers that are independent prognostic factors could potentially provide targets for novel treatment strategies to improve treatment outcome. For personalized hypoxia-guided treatment, safe and reliable makers for tumor hypoxia are needed to select suitable patients.

Radiosensitizing effect of irisquinone on glioma through the downregulation of HIF-1α evaluated by 18F-FDG and 18F-FMISO PET/CT

OBJECTIVE

The aim of this study was to elucidate the radiosensitizing mechanism of irisquinone (IQ) and evaluate the utility of F-fluorodeoxyglucose (F-FDG) and F-fluoromisonidazole (F-FMISO) PET/computed tomography (CT) in assessing the radiosensitizing effect of IQ.

MATERIALS AND METHODS

In an in-vitro experiment, C6 rat glioma cells were treated with IQ, radiation, or both. The viability and radiosensitivity of C6 cells were detected using the MTT assay and clonogenic survival assay. The expression of hypoxia-inducible factor-1α (HIF-1α) was evaluated by real-time PCR and western blot. In an in-vivo experiment, C6 rat glioma cells were implanted into the right flank of rats and treated with IQ, radiation, both, or no treatment. F-FDG and F-FMISO PET/CT images were obtained before and after treatment. The expression of HIF-1α was detected by immunohistochemistry staining.

RESULTS

In the in-vitro experiment, the results of the MTT assay showed that the half-inhibition concentration (IC50) of IQ for normoxic and hypoxic C6 tumor cells was 17.2 and 21.0 nmol/l, respectively. Clonogenic survival assay showed that IQ could improve the radiosensitivity of both normoxic and hypoxic C6 tumor cells. When the concentration of irradiation was 20% IC50 (4.2 nmol/l), the sensitive enhancement ratio of normoxic and hypoxic C6 tumor cells was 1.18 and 1.33, respectively. The mRNA and protein expression levels of HIF-1α decreased significantly when treated with IQ plus radiation compared with the other groups.In the in-vivo experiment, 24 or 48 h after different treatments, the maximum standardized uptake values (SUVmax) of F-FDG or F-FMISO uptake decreased in the radiation group and the IQ plus radiation group, whereas these values increased in the control and IQ groups. The SUVmax of F-FDG or F-FMISO uptake in IQ plus radiation group were lower than those of the radiation group (t=3.28, 2.62, P<0.05). However, there was no significant decrease in tumor volumes in the radiation group and the IQ plus radiation treatment group early after treatment.Immunohistochemistry staining showed that there were significant differences in the expression of HIF-1α in the four groups (F=87.1, P<0.01). The SUVmax of both F-FDG and F-FMISO uptake showed a significant correlation with the expression of HIF-1α. F-FMISO provided a higher correlation coefficient with HIF-1α than F-FDG (r=0.93, 0.82, P<0.01).

CONCLUSION

The present experiments indicated that IQ enhanced the radiosensitivity of C6 rat glioma cells both in vitro and in vivo. The primary mechanism of this radiosensitizing effect involves the downregulation of HIF-1α. F-FDG and F-FMISO PET/CT were sensitive and noninvasive for monitoring the early radiosensitizing effect of IQ. Meanwhile, F-FMISO PET/CT provided more information on the changes in tumor hypoxic status.

Gambogic acid enhances the radiosensitivity of human esophageal cancer cells by inducing reactive oxygen species via targeting Akt/mTOR pathway

Radiotherapy is a widespread treatment in human solid tumors. However, therapy resistance and poor prognosis are still problems. Gambogic acid (GA), extracted from the dried yellow resin of gamboges, has an anticancer effect against various types of cancer cells. To explore the radiosensitivity of GA on esophageal cancer cell line TE13, cell viability was tested by Cell Counting Kit-8 (CCK-8) assay, colony formation assay was used to assess the effects of GA on the radiosensitivity of TE13, and flow cytometry was performed to meter the percentage of apoptosis. The protein levels of microtubule-associated protein 1 light chain 3 (LC3), caspase3, caspase8, casepase9, pAkt, and p-mammalian target of rapamycin (p-mTOR) were tested using Western blot. The distribution of LC3 was detected by immunofluorescence. Additionally, we also examined reactive oxygen species (ROS) expression by laser scanning confocal microscope (LSCM). The cells were transfected with adenovial vector to monitor the autophagy through the expression of green fluorescent protein (GFP-red fluroscent protein (RFP)-LC3. The rates of apoptotic cells in combined-treated TE13 increased significantly compared with the control groups in accordance with the results of Western blot. The clonogenic survival assay showed that GA enhances radiosensitivity with a sensitizing enhancement ratio (SER) of 1.217 and 1.436 at different concentrations. The LC3-II protein level increased in the combined group indicating the increase of autophagy incidence, and the results of GFP-RFP-LC3 experiment showed that GA may block the process of autophagic flux in TE13 cells. Moreover, we successfully demonstrated that ROS is involved in the induction of autophagy. ROS-mediated autophagy depends on the inhibition of the Akt/mTOR pathway. Taken together, GA induced radiosensitivity involves autophagy and apoptosis which are regulated by ROS hypergeneration and Akt/mTOR inhibition.

Fenofibrate inhibits the expression of VEGFC and VEGFR-3 in retinal pigmental epithelial cells exposed to hypoxia

The aim of the present study was to examine the mechanisms through which fenofibrate inhibits the ability of human retinal pigment epithelial cells (RPE cells) exposed to hypoxia to stimulate the proliferation and migration of human umbilical vein endothelial cells (HUVECs). For this purpose, RPE cells and HUVECs were divided into the following groups: RPE-normoxia, RPE + fenofibrate, RPE-hypoxia, RPE hypoxia + fenofibrate; HUVECs normal culture and HUVECs + RPE-hypoxia culture supernatant. RPE cell hypoxia was induced by cobalt(II) chloride (CoCl₂). A superoxide anion probe was used to measure the production of superoxide anion, which is indicative of hypoxic conditions. Cell proliferation was assessed by MTT assay, and the expression of vascular endothelial growth factor C (VEGFC) and vascular endothelial growth factor receptor-3 (VEGFR-3) in the RPE cell culture supernatant was measured by enzyme-linked immunosorbent assay (ELISA). The migration ability of the HUVECs was determined by scratch-wound assay, and the angiogenic ability of the HUVECs was examined by measuring cell lumen formation. The mRNA and protein expression levels of VEGFC and VEGFR-3 in the RPE cells were measured by RT-qPCR and western blot analysis, respectively. Our results revealed that fenofibrate inhibited the increase in the expression and release of VEGFC and VEGFR-3 into the RPE cell culture supernatant induced by exposure to hypoxia. The culture of HUVECs in medium supernatant of RPE cells epxosed to hypoxia enhanced the viability and migration ability of the HUVECs and promoted lumen formation; these effects were inhibited by fenofibrate. In conclusion, our data demonstrated that the exposure of RPE cells to hypoxia induced the expression and release of VEGFC and VEGFR-3 into the cell culture supernatant. The culture of HUVECs in conditioned medium from RPE cells exposed to hypoxia increased VEGFC and VEGFR-3 expression, and promoted the proliferation and migration of the HUVECs, as well as capillary tube formation, suggesting that RPE cells play an important role in the formation of choroidal neovascularization resulting from hypoxia. Fenofibrate inhibited the upregulation of VEGFC and VEGFR-3 in the RPE cells exposed to hypoxia, and thus reduced the ability of HUVECs to form new blood vessels.

Fenofibrate in cancer: mechanisms involved in anticancer activity

Objective: To review the mechanisms of anti-cancer activity of fenofibrate (FF) and other Peroxisome Proliferator Activator Receptor α (PPARα) agonists based on evidences reported in the published literature.Methods: We extensively reviewed the literature concerning FF as an off target anti-cancer drug. Controversies regarding conflicting findings were also addressed.Results: The main mechanism involved in anti-cancer activity is anti-angiogenesis through down-regulation of  Vascular Endothelial Growth Factor (VEGF), Vascular Endothelial Growth Factor Receptor (VEGFR) and Hypoxia Inducible factor-1 α (HIF-1α), inhibition of endothelial cell migration, up-regulation of endostatin and thrombospondin-1, but there are many other contributing mechanisms like apoptosis and cell cycle arrest, down-regulation of Nuclear Factor Kappa B (NF-kB) and Protein kinase B (Akt) and decrease of cellular energy by impairing mitochondrial function. Growth impairment is related to down-regulation of Phospho-Inositol 3 Kinase (PI3K)/Akt axis and down-regulation of the p38 map kinase (MAPK) cascade. A possible role should be assigned to FF stimulated over-expression of Tribbles Homolog-3 (TRIB3) which inhibits Akt phosphorylation. Important anti-cancer and anti-metastatic activities are due to down-regulation of MCP-1 (monocyte chemotactic protein-1), decreased Metalloprotease-9 (MMP-9) production, weak down-regulation of adhesion molecules like E selectin, intercellular adhesion molecules (ICAM) and Vascular Endothelial Adhesion Molecules (VCAM), and decreased secretion of chemokines like Interleukin-6 (IL-6), and down-regulation of cyclin D-1. There is no direct link between FF activity in lipid metabolism and anticancer activity, except for the fact that many anticancer actions are dependent from PPARα agonism. FF exhibits also PPARα independent anti-cancer activities.Conclusions: There are strong evidences indicating that FF can disrupt growth-related activities in many different cancers, due to anti-angiogenesis and anti-inflammatory effects. Therefore FF may be useful as a complementary adjunct treatment of cancer, particularly included in anti-angiogenic protocols like those currently increasingly used in glioblastoma. There are sound reasons to initiate well planned phase II clinical trials for FF as a complementary adjunct treatment of cancer.

Metformin enhances radiation response of ECa109 cells through activation of ATM and AMPK

Metformin is a first-line used agent for type II diabetes with few side effects. The antineoplastic effect of metformin was widely explored recently. Metformin may also be a prospective chemosensitizer or radiosensitizer in cancer treatment. In the present study, we firstly showed that metformin could effectively enhance the anti-proliferation effect of ionizing radiation (IR) on esophageal cancer (EC) cells ECa109. More potent DNA damage was observed by detection of γH2AX foci. Metformin synergistically induce apoptosis and cell cycle arrest in ECa109 cells with IR. Furthermore, the mechanisms how metformin sensitized ECa109 cells to IR may be targeting the ATM and AMPK/mTOR/HIF-1α pathways. Metformin may be a valuable agent in comprehensive treatment of EC.