Ionizing Radiation-inducible microRNA-21 Induces Angiogenesis by Directly Targeting PTEN

Background:

Previous experimental studies have established that MicroRNAs (miRNAs) can function as oncogenes or tumor suppressors in the regulation of tumor biology or pathology. However, the effects of ionizing radiation (IR) on the expression levels of cellular miRNAs and their further effects on the biological behavior of tumor cells require further investigation.

Methods:

We determined the proliferation, migration and tube formation of HUVEC cells after ionizing radiation (control, 0h and 24h), and the changes of miR-21, VEFG and HIF-1α levels after ionizing radiation were measured by Western blot (WB). The effects of miR-21 mimics and inhibitors on the protein and mRNA expression of PTEN were determined by RT-PCT and WB. Two independent luciferase reporter plasmids were constructed to detect changes in PTEN protein expression.

Results:

We found that both IR and miR-21 increase proliferation, migration and tube formation of HUVEC cells. Ionizing radiation directly targets the inhibition of PTEN expression by causing an increase in miR-21 expression, and induces the accumulation of VEGF and HIF-1α expression in cells by the PI3K / AKT signaling pathway. Simultaneous induction of ectopic expression of PTEN can rescue radiation-induced proliferation, migration and tube formation in tumor cells.

Conclusion:

miR-21 promotes tumor cell proliferation and migration by targeting inhibition of PTEN expression, which may become a potential target for tumor therapy in the future.

Radiosensitivity of human ovarian cancer cells is enhanced by pseudolaric acid B due to the inhibition of the Ras/Raf/ERK signaling pathway

Ovarian cancer has the highest mortality rate among gynecological cancers; the most effective therapy for this cancer is a combination of radiation treatment and chemotherapy. However, radiation resistance is the leading factor associated with treatment failure. The present study aimed to investigate pseudolaric acid B (PAB) as a potential radiosensitizer for the treatment of ovarian cancer. The present study performed MTT and clonogenic assays, and demonstrated that PAB could induce a radiosensitizing effect on SKOV-3 cells. An Annexin V/propidium iodide staining assay revealed that PAB exerted a radiosensitizing effect by inducing SKOV-3 cell apoptosis. In addition, western blot analysis demonstrated that the activity of the Ras/RAF proto-oncogene serine/threonine-protein kinase/extracellular signal-regulated kinase signaling pathway was reduced by combination therapy with PAB and irradiation. In conclusion, the present study establishes PAB as a radiosensitizer, and provides a rational basis for the use of PAB and irradiation as a combination therapy to treat ovarian cancer.

Low-dose radiation may be a novel approach to enhance the effectiveness of cancer therapeutics

It has been generally accepted that both natural and man-made sources of ionizing radiation contribute to human exposure and consequently pose a possible risk to human health. However, accumulating evidence has shown that the biological effects of low-dose radiation (LDR) are different from those of high-dose radiation. LDR can stimulate proliferation of normal cells and activate their defense systems, while these biological effects are not observed in some cancer cell types. Although there is still no concordance on this matter, the fact that LDR has the potential to enhance the effects of cancer therapeutics and reduce the toxic side effects of anti-cancer therapy has garnered significant interest. Here, we provide an overview of the current knowledge regarding the experimental data detailing the different responses of normal and cancer tissues to LDR, the underlying mechanisms, and its significance in clinical application.

High and low dose radiation effects on mammary adenocarcinoma cells - an epigenetic connection

The successful treatment of cancer, including breast cancer, depends largely on radiation therapy and proper diagnostics. The effect of ionizing radiation on cells and tissues depends on the radiation dose and energy level, but there is insufficient evidence concerning how tumor cells respond to the low and high doses of radiation that are often used in medical diagnostic and treatment modalities. The purpose of this study was to investigate radiation-induced gene expression changes in the MCF-7 breast adenocarcinoma cell line. Using microarray technology tools, we were able to screen the differential gene expressions profiles between various radiation doses applied to MCF-7 cells. Here, we report the substantial alteration in the expression level of genes after high-dose treatment. In contrast, no dramatic gene expression alterations were noticed after the application of low and medium doses of radiation. In response to a high radiation dose, MCF-7 cells exhibited down-regulation of biological pathways such as cell cycle, DNA replication, and DNA repair and activation of the p53 pathway. Similar dose-dependent responses were seen on the epigenetic level, which was tested by a microRNA expression analysis. MicroRNA analysis showed dose-dependent radiation-induced microRNA expression alterations that were associated with cell cycle arrest and cell death. An increased rate of apoptosis was determined by an Annexin V assay. The results of this study showed that high doses of radiation affect gene expression genetically and epigenetically, leading to alterations in cell cycle, DNA replication, and apoptosis.

Tumor inhibition effects and mechanisms of Angelica sinensis and Sophorae flavescentis ait decoction combined with cisplatin in xenograft mice

BACKGROUND

To investigate tumor inhibition effects and mechanisms of Angelica sinensis and Sophorae flavescentis ait decoction (ASSF) combined with diamine-dichloroplatinum (DDP).

MATERIALS AND METHODS

Bodyweight, tumor inhibition rate and q value were calculated for single ASSF or ASSF combined with DDP on H22 carcinoma xenograft KM mice. Biochemical methods for serum LDH, AST, ALT, and AKP, ELISA method for serum HIF-1α, pathological assessemnt of thymus, immunohistochemistry detection of tumor tissue caspase3 and mutant p53 protein, and qRT-PCR detection of bax/ bcl-2 mRNA were applied.

RESULTS

Compared with DDP control group, the bodyweight increased in ASSF-DDP group (p<0.01). Tumor inhibition rates for DDP, ASSF, ASSF-DDP were 62.7%. 43.7% and 71.0% respectively, with a q value of 0.90. Compared with other groups, thymus of DDP control group had obvious pathological injury (p<0.01), serum LDH, AST, ALT, AKP increased significantly in DDP control group (p<0.01), while serum HIF-1α was increased in the model control group. Compared with this latter, the expression of mutant p53 protein and bcl-2 mRNA were decreased in all treatment groups (p<0.01), but there were no statistical difference between DDP control p and ASSF-DDP groups. The expression of caspase3 protein and bax mRNA was increased in all treatment groups, with statistical differences between the DDP and ASSF-DDP groups (p<0.01).

CONCLUSIONS

ASSF can inhibit bodyweight decrease caused by DDP, can inhibit tumor growth synergistically with DDP mainly through increasing serum HIF-1α and pro-apoptotic molecules such as caspase 3 and bax, rather than through decreasing anti-apoptotic mutant p53 and bcl-2. ASSF can reduce DDP toxicity due to decreasing the release of LDH, AST, ALT, AKP into blood and enhancing thymus protection.