Pancreatic cancer has a poor prognosis as a malignant tumor. Whether it is surgery, radiotherapy or chemotherapy, the survival rate of patients is not high. It is urgent to develop new effective treatment strategies. Photodynamic therapy (PDT) is a new method for treating diseases by using photosensitizers. When photosensitizers are activated by light, reactive oxygen species (ROS) are formed, which destroys tumor cells. Compared to traditional radiotherapy and chemotherapy, PDT is more selective and therefore has fewer side effects. The good optical properties of quantum dots make it surpass the traditional photosensitizers. Recent studies have shown that under light conditions, quantum dots conduct electrons to the surrounding oxygen molecules to induce ROS formation, making quantum dots a potential photosensitizer for photodynamic therapy.
The Lei-Ming Xu group of Xinhua Hospital affiliated to Shanghai Jiaotong University, with different concentration of quantum dots, was incubated with pancreatic cancer cell line SW1990 with or without light, and then on cell viability, ultrastructure, apoptosis and reactive oxygen species. Free radical levels and the like were tested and analyzed. The results show that when the concentration is high, the quantum dots inhibit cell proliferation. If the light is increased or the incubation time is prolonged, the cell viability is significantly decreased. Under light conditions, the quantum dots cause ultrastructural changes such as organelle degradation, chromatin condensation and nuclear. Weekly aggregation; fluorescence microscopy and flow cytometry showed that 1.5uM quantum dots induced apoptosis and reactive oxygen species production under light conditions; qPCR and Western blotting showed increased expression of Bax and caspase, while Bcl-2 expression At the same time, inhibition of ROS and apoptosis alleviated cell death induced by quantum dot photodynamic therapy (Figure 1 and Figure 2). The above research provides a new application direction for photodynamic therapy of pancreatic cancer, but more preclinical and clinical trials are needed before clinical application.
Figure 1 Generation of reactive oxygen species (ROS) after quantum dots and illumination treatment.
A. Fluorescence imaging of ROS in SW1990 cells; B. Flow cytometry to detect relative levels of ROS; C. Analysis of SW1990 cell viability using CCK-8 kit. Control: normal SW1990 cells; Light: light treatment (20 J/cm2) of SW1990 cells; QDs: Quantum dots (1.5 uM incubation for 3 h) treated SW1990 cells; PDT: quantum dots (1.5 uM, 3 h) and SW1990 cells co-treated with light (20 J/cm2). NAC: N-acetylcysteine, N-acetylcysteine, ROS capture agent, incubated with 5 mM NAC for 1 h before treatment of cells.
Figure 2 Quantum dot photodynamic therapy induces cell death through apoptosis.
A. Analysis of SW1990 cell viability by CCK-8 kit; B. Analysis of apoptosis and necrosis of SW1990 cells by Hochest33342/PI nuclear staining (100X magnification), white arrow indicating dead cells; C. Analysis of SW1990 cells by flow cytometry Percentage of apoptosis and necrosis. SW1990 cells were treated with Z-VAD-FMK (50 uM, caspase inhibitor) for 1 h and then treated with QD-PDT (1.5 uM, 3 h, 20 J/cm 2 ). QDs: Quantum dots; PDT: Photodynamic therapy; FCM: Flow cytometry; CCK-8: Cell counting kit-8; PI: Propidium iodide.
Source of the document:
He SJ, Cao J, Li YS, Yang JC, Zhou M, Qu CY, Zhang Y, Shen F, Chen Y, Li MM, Xu LM. CdSe/ZnS quantum dots induce photodynamic effects and cytotoxicity in pancreatic cancer cells. World J Gastroenterol. 2016;22(21):5012-22.
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