Ionizing Radiation Increases the Activity of Exosomal Secretory Pathway in MCF-7 Human Breast Cancer Cells: A Possible Way to Communicate Resistance against Radiotherapy

Abstract

Radiation therapy, which applies high-energy rays, to eradicate tumor cells, is considered an essential therapy for the patients with breast cancer. Most tumor cells secrete exosomes, which are involved in cell-to-cell communication in tumor tissue and contribute therapeutic resistance and promote tumor aggressiveness. Here, we investigated the effect of clinically applicable doses of X-ray irradiation (2, 4, 6, 8, 10 Gy) on the dynamics of the exosomes’ activity in MCF-7 breast cancer cells. Survival and apoptosis rate of cells against X-ray doses was examined using MTT and flow cytometry assays, respectively. Whereas, the levels of reactive oxygen species (ROS) in the X-ray-treated cells were detected by fluorometric method. The mRNA levels of vital genes involved in exosome biogenesis and secretion including Alix, Rab11, Rab27a, Rab27b, TSPA8, and CD63 were measured by real-time PCR. The protein level of CD63 was examined by Western blotting. Additionally, exosomes were characterized by monitoring acetylcholinesterase activity, transmission electron microscopy, size determination, and zeta potential. The result showed that in comparison with control group cell survival and the percentage of apoptotic cells as well as amount of ROS dose-dependently decreased and increased in irradiated cells respectively (p < 0.05). The expression level of genes including Alix, Rab27a, Rab27b, TSPA8, and CD63 as well as the protein level of CD63 upraised according to an increase in X-ray dose (p < 0.05). We found that concurrent with an increasing dose of X-ray, the acetylcholinesterase activity, size, and zeta-potential values of exosomes from irradiated cells increased (p < 0.05). Data suggest X-ray could activate exosome biogenesis and secretion in MCF-7 cells in a dose-dependent way, suggesting the therapeutic response of cells via ROS and exosome activity.

Retracted Article: Macrophage-derived exosomes mediate osteosarcoma cell behavior by activating AKT signaling

“…Exosomes mediate various physiologic processes by transmitting their contents, such as nucleic acids, proteins and lipids to recipient cells, therefore exerting their functions. 25,26 For example, mouse colon cancer cell-derived exosomes carry Wnt1 to mediate autophagic ux and tumorigenic potential. 24 miR-192-5p was shown within exosomes derived from lipotoxic hepatocyte to activate the macrophages.…”

“…The typical exosome marker ALIX is a transcription factor, and is involved in exosome biogenesis and secretion. 26 Through the knockdown of ALIX, exosome production and secretion decreased. Our results revealed that ALIX knockdown altered the effect of macrophagederived exosomes on cell proliferation, migration and drugresistance.…”

Role of Exosomes in Cancer-Related Cognitive Impairment

“…The use of radiation therapy in the treatment of a variety of CNS-related malignancies can affect brain structure and function, leading to cognitive deterioration [102]. Radiation used in cancer therapy can also activate the biogenesis and induce exosome secretion from cancer cells [103]. Hinzman et al highlighted that several molecules (i.e., triglycerides, platelet activating factor, carnitine, and C-16 sphinganine) involved in inflammation were enriched in the exosomes of mice exposed to cranial ionizing radiation [104].…”

High frequency acoustic cell stimulation promotes exosome generation regulated by a calcium-dependent mechanism

“…There are nevertheless a number of potential disadvantages to some of the aforementioned methods. The use of additives such as ionomycin and calcium phosphate, for example, while capable of enhancing exosome yield by 2.5-fold within 2-72 h (approximately 0.03-1-fold/h), are, however, dose dependent and overexposure of the cells to these chemicals can lead to a considerable reduction in their viability 34 ; similarly, exposing cells to ionising radiation can result in cell apoptosis 46 . Thermal and oxidative stresses, on the other hand, have been reported to increase exosome yield by approximately 20-30-fold in 24 h (approximately 0.8-1.25-fold/h) but can generate immunoresponsive exosomes, which could impair their diagnostic or therapeutic potential 44 .…”