EFFECTS OF POLYDOPAMINE COMBINED WITH LUTEOLIN ON TUMOR KILLING BY CYTOTOXIC LYMPHOCYTES

Abstract

Objective To explore the effects of polydopamine (PDA) plus luteolin (LUT) with photothermal therapy on tumor killing by cytotoxic lymphocytes (CTL). Methods The synthesized PDA was characterized by using a scanning electron microscope (SEM) and a contact angle analyzer. RAW264.7 cells were divided into control group, LPS group (2 μg/L), and PDA' group (50 000 μg/L). After 48 h culture, cell viability was determined by cell counting kit-8. The effect of LUT on the differentiation of RAW264.7 cells was determined by flow cytometry. Female C57BL/6 mice were randomly divided into model group, PDA group, LUT group, and PDA+LUT group. B16F10 melanoma cells were subcutaneously injected into the back of mice in each group. On the 10th day after modeling, the PDA and PDA+LUT groups received injection of PDA into the tumor as well as photothermal therapy. The mice in the four groups received injection of PBS, PDA (2.5 μg/piece), LUT (500 μg/piece), and PDA (2.5 μg/piece) plus LUT (500 μg/piece) into the muscle of the right thigh, respectively. We observed the tumor growth and survival of the model mice. On days 3 and 7 after treatment, the spleen of each mouse was taken to prepare a single cell suspension for analysis of macrophage differentiation and T cell expression by flow cytometry. Results SEM showed that the synthesized PDA had good adhesion and affinity for water. CCK8 showed that the PDA did not affect cell viability (P>0.05). Significant differences were found in the mean fluorescence intensities of CD206 and iNOS between different groups of RAW264.7 cells (F=30.72,1 516.00,P<0.05). There were significant differences in tumor size and the expression levels of iNOS, CD206, IFN-γ+CD4+, and TNF-α+CD8+ of immune cells between mice with and without LUT injection, under the condition of either injecting or not injecting PDA (F=23.10-235.52,P<0.05). There were significant differences in tumor size and the expression levels of iNOS, CD206, IFN-γ+CD4+, and TNF-α+CD8+ of immune cells between mice with and without PDA injection, under the condition of either injecting or not injecting LUT (F=8.98-200.67,P<0.05). The survival rate of the PDA+LUT group was significantly higher than those of the other groups (χ2=9.70,P<0.01). Conclusion LUT could inhibit the differentiation of macrophages to M2 and promote the differentiation to M1 in mice. PDA combined with LUT could effectively inhibit tumor growth, improve survival rate, and enhance the tumor-kil-ling effect of CTL in mice.

Keywords

• melanoma|cell line, tumor|photothermal therapy|dopamine|polymers|luteolin|tumor escape|t-lymphocytes, cytotoxic