tetra(4-n-methylpyridyl)porphine and Osteosarcoma

Osteosarcoma (OS) is characterized by high levels of the tumour-associated inflammatory microenvironment. Moreover, in approximately 60% of OS, telomere length is maintained by alternative lengthening of telomeres (ALT) pathway. Whether the ALT pathway can be exploited for OS therapeutic treatment and how the OS inflammatory microenvironment influences the anti-cancer drug effect remains unknown. Here, we examined the biological effects of TMPyP4 and cisplatin in the inflammatory microenvironment of OS cells.. Immunofluorescence in situ hybridization (IF-FISH) and C-circle experiments were used to detect the G-quadruplex and ALT activity. The redox potential of single guanine, G-quadruplex and G-quadruplex/TMPyP4 was evaluated by the lowest unoccupied molecular orbital energy (LUMO), zeta potential and cyclic voltammetry. Cell viability, flow cytometry and apoptosis, Western blot, comet assay, adhesion, transwell and scratch experiments were performed to compare the anti-tumour proliferation and migration effects of TMPyP4 and cisplatin in the inflammatory microenvironment.. This study indicated that compared with cisplatin, TMPyP4 could induce the formation of human telomeres and FAK G-quadruplex in vitro and in vivo, and TMPyP4-treated OS cells showed fewer extrachromosomal C-circles and fewer ALT-associated promyelocytic leukaemia bodies. Consequently, the ALT activity and FAK-related cell migration were suppressed by TMPyP4. Mechanistically, the formation of G-quadruplex resulted in both lower redox potential than G within the genome and FAK transcription inhibition, and TMPyP4 could enhance this phenomenon, especially in the inflammatory microenvironment.. Our results reveal that TMPyP4 is more suitable for OS treatment than cisplatin.

Topics: Antineoplastic Agents; Apoptosis; Cell Line, Tumor; Cell Movement; Cell Survival; Cisplatin; G-Quadruplexes; Humans; Osteosarcoma; Porphyrins; Telomerase; Telomere; Tumor Microenvironment

Telomere studies in carcinomas have been extensively reported for prognostic utility and effective methods for targeting telomerase therapy has been described, but efficacy of telomerase inhibitor remained unknown in sarcoma cells. In this study, we investigated the effects of telomerase inhibitor cationic porphyrin TMPyP4 on telomerase activity, telomere length, cell growth, and apoptosis in osteosarcoma cell lines. TMPyP4 significantly inhibited telomerase activity in telomerase positive HOS and Saos-2, but not in MG-63. TMPyP4 significantly induced telomere shortening, and inhibition of the cell growth in HOS and Saos-2 with over 17% apoptosis rates. In terms of MG-63, TMPyP4 did not induce inhibition of both telomerase activity and cell growth, although it induced significant telomere shortening. Telomere length after treatment was 5.60 kb in HOS, 4.00 kb in Saos-2, and 9.89 kb in MG-63. These results may suggest that both telomerase activity loss and sufficient telomere shortening are necessary to inhibit cell growth in telomerase positive osteosarcoma cells. TMPyP4 did not induced telomere shortening but significantly inhibited the growth with 22.6% apoptosis rate in telomerase negative with extremely longer telomere-U2OS, may indicating the antitumor effect of TMPyP4 may be related to DNA damage including telomere dysfunction through G-quadruplex stabilization, independent on telomere length.

Topics: Apoptosis; Bone Neoplasms; Cell Line, Tumor; Cell Survival; Enzyme Inhibitors; Humans; Osteosarcoma; Porphyrins; Telomerase; Telomere