Although radiotherapy has been extensively applied in cancer treatment, external beam radiation therapy is still unable to avoid damage to adjacent normal tissues in the process of delivering a sufficient radiation dose to the tumor sites of patients. To overcome this limitation, chemoradiotherapy, as a combination of chemotherapy and radiotherapy of a radioactive seed, has been proposed to decrease the damage to tumor-surrounding tissues and enhance the radiosensitivity of solid tumors. In this study, we designed and synthesized folic acid-conjugated selenium nanoparticles (FA@SeNPs) as a cancer-targeting agent that could be synergistically enhanced by radioactive I seeds to realize anticancer efficacy and inhibited colony formation ability. Interestingly, when compared with X-ray irradiation,I seeds demonstrate a larger synergistic effect with the FA@SeNPs, drastically increasing reactive oxygen species overproduction to trigger apoptosis and influencing the cell cycle distribution in human breast cancer cells, inducing DNA damage and activating the mitogen-activated protein kinase and p53 signaling pathways. Moreover, this combination treatment demonstrates better in vivo antitumor activity and lower systemic toxicity. Therefore, this study demonstrates a new strategy for using functionalized SeNPs as a radiation sensitizer for I seeds for cancer therapy.
Bladder cancer is still a common malignancy of the urinary tract due to the high metastasis rate and unexpected side effects of drug treatments. The acidic environment of the urinary bladder also strongly limits the efficacy of the chemotherapeutic agents during the treatment of bladder cancer. In this study, a series of selenadiazole derivatives (SeDs) have been rationally designed and synthesized and could actively suppress the progression and metastasis of bladder cancer cells. SeDs demonstrated better antiproliferative activity and higher stability under different physiological conditions, especially in an acidic urocystic environment, than mitomycin, a clinically used anti-bladder cancer drug. In particular, compound 1b displayed better selectivity between cancer and normal cells in comparison with other compounds. Studies on the structure-activity relationship revealed that the introduction of strong electron donating substituents, such as the methoxy group, resulted in a dramatic enhancement in the anticancer efficacy. Furthermore, 1b induced anti-migration and anti-invasion activities against bladder cancer cells. Mechanistic investigation revealed that compound 1b was able to enter the cells through endocytosis and then trigger reactive oxygen species (ROS) overproduction, further causing DNA damage-mediated p53 phosphorylation and promoting cancer cell apoptosis by regulating the AKT and MAPKs signaling pathways. Altogether, the study provides a strategy for rational design of selenadiazole derivatives with improved stability to antagonize bladder cancer.
Cancer radiotherapy with I seeds demonstrates higher long-term efficacy and fewer side effects than traditional X-ray radiotherapy owing to its low-dose and continuous radiation but is still limited by radioresistance in clinical applications. Therefore, the design and synthesis of sensitizers that could enhance the sensitivity of cancer cells to I seeds is of great importance for future radiotherapy. Selenium nanoparticles (SeNPs) have been found to exhibit high potential in cancer chemotherapy and as drug carriers. In this study, we found that, based on the Auger-electron effect and Compton effect of Se atoms, cancer-targeted SeNPs in combination with I seeds achieve synergetic effects to inhibit cancer-cell growth and colony formation through the induction of cell apoptosis and cell cycle arrest. Detailed studies on the action mechanisms reveal that the combined treatments effectively activate intracellular reactive oxygen species (ROS) overproduction to regulate p53-mediated DNA damage apoptotic signaling pathways and mitogen-activated protein kinase (MAPK) phosphorylation and to prevent the self-repair of cancer cells simultaneously. Taken together, the combination of SeNPs with I seeds could be further exploited as a safe and effective strategy for next-generation cancer chemo-radiotherapy in clinical applications.
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