Activation of Autophagy and Nrf2 Signaling in Human Breast Adenocarcinoma MCF-7 Cells by Novel Monophenolic Antioxidants

The effect of novel water-soluble structurally related monophenolic compounds on the activity of two most important mechanisms of maintaining intracellular homeostasis, autophagy and the redox-sensitive signal system Keap1/Nrf2/ARE, has been studied in human breast adenocarcinoma cell line MCF-7 using confocal microscopy. Autophagy processes were analyzed on the basis of the amount of intracellular vesicles that were positive for the autophagy marker (LC3B). The activation of the Keap1/Nrf2/ARE system was determined by the translocation of the transcription factor Nrf2 into the nucleus. It was found that the effect of the tested compounds depended on their structure and concentration. When the inhibitor of autophagosome–lysosome fusion chloroquine was added to the culture medium (20 μM), the asymmetrically hindered by the tert-butyl group phenols with thiosulfonate (TS-13) and sulfonate group in the para-propyl substituent increased the rate of autophagosome elimination in MCF-7 cells. Shortening of the para-alkyl substituent by one methylene unit abolished the effect. The addition of the second ortho-tert-butyl substituent had the reverse result. Both tested compounds enhanced the translocation of the transcription factor Nrf2 into the nucleus of MCF-7 cells (which is a critical step in Keap1/Nrf2/ARE activation). It was observed after incubation with asymmetrically hindered by the tert-butyl group phenol with selenosulfonate group in para-propyl substituent (5−100 μM) for 4 h and with TS-13 (5−100 μM) for 24 h. Taking into account our previous findings on the toxicity of this group of compounds for MCF-7 cells we can conclude that these compounds exert different effect on autophagy and activation of the antioxidant response element signaling system Keap1/Nrf2/ARE

Synthetic phenolic antioxidant TS-13 suppresses the growth of Lewis lung carcinoma and potentiates oncolytic effect of doxorubicin

ROS are important intracellular messengers; their ambiguous role in malignant processes was demonstrated in many studies. The effects of a synthetic phenolic antioxidant sodium 3-(3’-tert-butyl-4’-hydroxyphenyl)propyl thiosulfonate sodium (TS-13) on the tumor growth and oncolytic properties of doxorubicin were studied in the experimental model of Lewis lung carcinoma in mice. In mice receiving TS-13 with drinking water (100 mg/kg), suppression of tumor growth by 32.3% was observed on day 21 after inoculation of Lewis lung carcinoma cells. Two-fold intraperitoneal injections of doxorubicin in a cumulative dose of 8 mg/kg were followed by inhibition of tumor growth by 49.5%. Combined treatment with TS-13 and doxorubicin suppressed the tumor growth by 55.4%. In contrast to doxorubicin, TS-13 inhibited NO generation by peritoneal macrophages. The results show the prospect of studying TS-13 in the context of overcoming drug-resistance of tumors