Troglitazone-Induced PRODH/POX-Dependent Apoptosis Occurs in the Absence of Estradiol or ERβ in ER-Negative Breast Cancer Cells

Abstract

The impact of estradiol on troglitazone (TGZ)-induced proline dehydrogenase/proline oxidase (PRODH/POX)-dependent apoptosis was studied in wild-type and PRODH/POX-silenced estrogen receptor (ER) dependent MCF-7 cells and ER-independent MDA-MB-231 cells. DNA and collagen biosynthesis were determined by radiometric method, prolidase activity evaluated by colorimetric method, ROS production was measured by fluorescence assay. Protein expression was determined by Western blot and proline concentration by LC/MS analysis. PRODH/POX degrades proline yielding reactive oxygen species (ROS). Estrogens stimulate collagen biosynthesis utilizing free proline and limiting its availability for PRODH/POX-dependent apoptosis. TGZ cytotoxicity was highly pronounced in wild-type MDA-MB-231 cells cultured in medium without estradiol or in the cells cultured in medium with estradiol but deprived of ERβ (by ICI-dependent degradation), while in PRODH/POX-silenced cells the process was not affected. The TGZ cytotoxicity was accompanied by increase in PRODH/POX expression, ROS production, expression of cleaved caspase-3, caspase-9 and PARP, inhibition of collagen biosynthesis, prolidase activity and decrease in intracellular proline concentration. The phenomena were not observed in PRODH/POX-silenced cells. The data suggest that TGZ-induced apoptosis in MDA-MB-231 cells cultured in medium without estradiol or deprived of ERβ is mediated by PRODH/POX and the process is facilitated by proline availability for PRODH/POX by TGZ-dependent inhibition of collagen biosynthesis. It suggests that combined TGZ and antiestrogen treatment could be considered in experimental therapy of estrogen receptor negative breast cancers.

Nonsteroidal Anti-Inflammatory Drugs as PPARγ Agonists Can Induce PRODH/POX-Dependent Apoptosis in Breast Cancer Cells: New Alternative Pathway in NSAID-Induced Apoptosis

“…These receptors can be activated by natural ligands, such as fatty acids or prostaglandins, as well as by synthetic ligands [20][21][22][23]. The most popular and well-studied synthetic ligands of PPARγ are thiazolidinediones (i.e., troglitazone, pioglitazone), the class of drugs used for the treatment of type 2 diabetes mellitus [24][25][26]. Interestingly, they were found to provoke proapoptotic activities in cancer cells [25,27].…”

Understanding Breast Cancer Aggressiveness and Its Implications in Diagnosis and Treatment

“…Glycolysis is also induced by oncogenes activation and loss of tumor suppressors, linking a high rate of glucose metabolism and cancer [ 8 ]. Since glucose is supporting cancer progression, it has been suggested that controlled calorie intake will reduce oxidative stress and protect cells from becoming oncogenic [ 9 ]. Therefore, caloric restriction could ameliorate the risk factors in breast cancer by reducing blood glucose levels, inflammation, and the onset of angiogenesis [ 10 ].…”

Metformin Induces PRODH/POX-Dependent Apoptosis in Breast Cancer Cells

“…A similar effect was found in MCF-7 cells treated with non-steroidal anti-inflammatory drugs ( Kazberuk et al, 2022b ). Other studies on MCF-7 and MDA-MB-231 cells highlighted the role of estrogens and estrogen receptors (ERα and ERβ) in PRODH/POX-dependent apoptosis ( Lewoniewska et al, 2021 ). We have found that the activation of PRODH/POX (by troglitazone) induced apoptosis only in the absence of estradiol or ERβ in MDA-MB-231 cells.…”