We determined whether the systemic administration of viable Mycobacterium bovis organisms (BCG) or a lipophilic derivative of muramyl tripeptide (MTP-PE) would lead to the activation of antitumor properties in murine Kupffer cells (KC). KC-mediated tumor cytolysis was determined by the release of radiolabeled nuclear breakdown products of target cells. KC harvested from either C57BL/6 or C3H/HEN mice treated with saline exhibited no cytotoxicity against syngeneic B16 melanoma or UV-2237 fibrosarcoma cells. In contrast, KC harvested from BCG or MTP-PE-injected mice were highly cytotoxic against the tumor targets, as measured by an in vitro radiorelease assay. The demonstration that the administration of macrophage activators can generate in situ tumoricidal activity in KC suggests that these cells can be important in the control of hepatic micrometastases.

No abstract

Objectives: To study the effects of curcumin on the proliferation, invasion, apoptosis, and radiosensitivity of the radioresistant nasopharyngeal carcinoma (NPC) C6661-IR strain as well as the potential radiosensitization mechanism. Methods: NPC cells were continuously irradiated with different intensities of radiation to induce radiation-resistant cell lines. A plate clone formation assay was used to evaluate the effect of curcumin on the radiosensitivity of NPC cells. 3-(4,5-Dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide thiazolyl blue (MTT) assay was conducted to detect changes in cell viability. Flow cytometry was employed to analyze apoptosis percentage as well as Transwell® assay and immunofluorescence assay to observe cell invasion. Western blotting was applied to detect the expression levels of Bax, Bcl-2, and pro/cleaved-caspase 3. MiR-205-5p mimics and si-TP53INP1 were synthesized and transfected into C6661-IR cells, and the cells were then incubated with 10 µm/L curcumin. Real-time quantitative reverse transcription PCR (RT-qPCR) was used to measure miR-205-5p levels and western blotting was conducted to detect the expression of TP53INP1. Results: The optimal radiation dose of X-ray was 6 Gy, and this dose was used in all subsequent experiments. Curcumin treatment significantly inhibited the proliferation and invasion of C6661-IR cells, promoted apoptosis and enhanced radiosensitivity. Compared to the 0 Gy+Cur group and the 6 Gy+Cur group, the miR-205-5p levels were higher in the C6661-IR cells of the 0 Gy and 6 Gy groups. Moreover, miR-204-5p was found to directly target TP53INP1. Curcumin downregulated miR-205-5p levels and upregulated TP53INP1 expression (p < 0.05). Thus, modulation of miR-205-5p or TP53INP1 expression attenuates the biological effects of curcumin on C6661-IR cells. Conclusions: Curcumin inhibited the proliferation and invasion of C6661-IR, promoted apoptosis, and enhanced its radiosensitivity to X-rays by mediating miR-205-5p/TP53INP1 expression.