Phenanthroindolizidine Alkaloids Isolated from Tylophora ovata as Potent Inhibitors of Inflammation, Spheroid Growth, and Invasion of Triple-Negative Breast Cancer

Abstract

Triple-negative breast cancer (TNBC), representing the most aggressive form of breast cancer with currently no targeted therapy available, is characterized by an inflammatory and hypoxic tumor microenvironment. To date, a broad spectrum of anti-tumor activities has been reported for phenanthroindolizidine alkaloids (PAs), however, their mode of action in TNBC remains elusive. Thus, we investigated six naturally occurring PAs extracted from the plant Tylophora ovata: O-methyltylophorinidine (1) and its five derivatives tylophorinidine (2), tylophoridicine E (3), 2-demethoxytylophorine (4), tylophoridicine D (5), and anhydrodehydrotylophorinidine (6). In comparison to natural (1) and for more-in depth studies, we also utilized a sample of synthetic O-methyltylophorinidine (1s). Our results indicate a remarkably effective blockade of nuclear factor kappa B (NFκB) within 2 h for compounds (1) and (1s) (IC50 = 17.1 ± 2.0 nM and 3.3 ± 0.2 nM) that is different from its effect on cell viability within 24 h (IC50 = 13.6 ± 0.4 nM and 4.2 ± 1 nM). Furthermore, NFκB inhibition data for the additional five analogues indicate a structure–activity relationship (SAR). Mechanistically, NFκB is significantly blocked through the stabilization of its inhibitor protein kappa B alpha (IκBα) under normoxic as well as hypoxic conditions. To better mimic the TNBC microenvironment in vitro, we established a 3D co-culture by combining the human TNBC cell line MDA-MB-231 with primary murine cancer-associated fibroblasts (CAF) and type I collagen. Compound (1) demonstrates superiority against the therapeutic gold standard paclitaxel by diminishing spheroid growth by 40% at 100 nM. The anti-proliferative effect of (1s) is distinct from paclitaxel in that it arrests the cell cycle at the G0/G1 state, thereby mediating a time-dependent delay in cell cycle progression. Furthermore, (1s) inhibited invasion of TNBC monoculture spheroids into a matrigel®-based environment at 10 nM. In conclusion, PAs serve as promising agents with presumably multiple target sites to combat inflammatory and hypoxia-driven cancer, such as TNBC, with a different mode of action than the currently applied chemotherapeutic drugs.

Dermatological plants and their uses in theReceptariumof Burkhard III from Hallwyl from 16thcentury Switzerland – Data mining a historical text and preliminaryin vitroscreening

“…The medicinal properties of the species are often associated with the phenanthroindolizidine alkaloids (PIA) found in plants of the genus Vincetoxicum as well as in other genera. In vitro studies found potent anti-inflammatory activities in RAW264.7 mouse macrophage cell line for different PIAs (Yang et al, 2006; Chou et al, 2017; Reimche et al, 2022). However, PIAs are also known to be strongly cytotoxic and have therefore also been explored in terms of their anticancer properties.…”

NIR diagnostic imaging of triple-negative breast cancer and its lymph node metastasis for high-efficiency hypoxia-activated multimodal therapy

“…Hypoxia, as one of the typical features of TNBC, refers to the condition in which oxygen is insufficient to support the body’s metabolism [ 12 , 13 ]. The hypoxia condition occurs when the vascular supply is interrupted or tumor growth exceeds its vascular supply [ 14 , 15 ].…”

NIR diagnostic imaging of triple-negative breast cancer and its lymph node metastasis for high-efficiency hypoxia-activated multimodal therapy

“…Hypoxia, as one of the typical features of TNBC, refers to the condition in which oxygen is insu cient to support the body's metabolism [12,13]. The hypoxia condition occurs when the vascular supply is interrupted or tumor growth exceeds its vascular supply [14,15].…”