Stellettin B Induces Cell Death in Bladder Cancer Via Activating the Autophagy/DAPK2/Apoptosis Signaling Cascade

Abstract

Bladder cancer (BC) is one of the most prevalent cancers worldwide. However, the recurrence rate and five-year survival rate have not been significantly improved in advanced BC, and new therapeutic strategies are urgently needed. The anticancer activity of stellettin B (SP-2), a triterpene isolated from the marine sponge Rhabdastrella sp., was evaluated with the MTT assay as well as PI and Annexin V/7-AAD staining. Detailed mechanisms were elucidated through an NGS analysis, protein arrays, and Western blotting. SP-2 suppressed the viability of BC cells without severe toxicity towards normal uroepithelial cells, and it increased apoptosis with the activation of caspase 3/8/9, PARP, and γH2AX. The phosphorylation of FGFR3 and its downstream targets were downregulated by SP-2. Meanwhile, it induced autophagy in BC cells as evidenced by LC3-II formation and p62 downregulation. The inhibition of autophagy using pharmacological inhibitors or through an ATG5-knockout protected RT-112 cells from SP-2-induced cell viability suppression and apoptosis. In addition, the upregulation of DAPK2 mRNA and protein expression also contributed to SP-2-induced cytotoxicity and apoptosis. In RT-112 cells, an FGFR3-TACC3-knockout caused the downregulation of DAPK2, autophagy, and apoptosis. In conclusion, this is the first study demonstrating that SP-2 exhibits potent anti-BC activity by suppressing the FGFR3-TACC3/Akt/mTOR pathway, which further activates a novel autophagy/DAPK2/apoptosis signaling cascade.

Marine-Derived Leads as Anticancer Candidates by Disrupting Hypoxic Signaling through Hypoxia-Inducible Factors Inhibition

“…There is an increasing number of reports describing the anticancer effects of stellettin B (87) (Figure 8), an isomalabaricane-type triterpene commonly reported from sponges of the genera Geodia [316,317], Jaspis [318,319], Rhabdastrella [320,321], and Stelletta [322,323]. Stellettin B (87) appears to act mainly due to the induction of autophagy and apoptosis by interfering with the PI3K/Akt, Stat3, and mTOR signaling pathways in glioblastoma [324,325] and chronic myeloid leukemia cells [319].…”

“…The variance in cytotoxicity observed between the sensitive breast cancer T47D cells, which heavily depend on mitochondrial oxidative phosphorylation, and the relatively unresponsive breast cancer MDA-MB-231 cells, which primarily utilize glycolysis, can be explained by the impact of thyrsiferol (81) on mitochondrial function [306]. There is an increasing number of reports describing the anticancer effects of stellettin B (87) (Figure 8), an isomalabaricane-type triterpene commonly reported from sponges of the genera Geodia [316,317], Jaspis [318,319], Rhabdastrella [320,321], and Stelletta [322,323]. Stellettin B (87) appears to act mainly due to the induction of autophagy and apoptosis by interfering with the PI3K/Akt, Stat3, and mTOR signaling pathways in glioblastoma [324,325] and chronic myeloid leukemia cells [319].…”

Deep-Sea Sponges and Corals off the Western Coast of Florida—Intracellular Mechanisms of Action of Bioactive Compounds and Technological Advances Supporting the Drug Discovery Pipeline

“…Subclass of Heteroscleromorpha: Stellettin B (isolated from Rhabdastrella sp.) inhibited cellular viability in bladder cancer cell lines including RT-112 (0.02-0.16 µM), which was associated with apoptotic features [122]. Via a protein kinase array, p-FGFR3, p-EGFR, and p-ErbB2 were reduced at the protein level (0.125-0.5 µM, 24-48 h) along with reduced levels of p-AKT and p-STAT3 (downstream of FGFR signaling) [122].…”

“…inhibited cellular viability in bladder cancer cell lines including RT-112 (0.02-0.16 µM), which was associated with apoptotic features [122]. Via a protein kinase array, p-FGFR3, p-EGFR, and p-ErbB2 were reduced at the protein level (0.125-0.5 µM, 24-48 h) along with reduced levels of p-AKT and p-STAT3 (downstream of FGFR signaling) [122]. Halenaquinone (purified from Xestospongia carbonaria) elicited the inhibition of cellular proliferation (EC 50 values of 1-10 µM) across a series of cell lines, including RR1022 (rat cells transformed with Rous sarcoma virus), NY684 (rat cells transformed with a temperature-sensitive variant of v-src), NIH src (NIH 3T3 transformed with wild-type c-src), NIH erbB-HX (NIH 3T3 transformed with v-erbB), and CH R C5 (multidrug-resistant Chinese hamster ovarian cells) [123].…”

Cucurbitacin E Exerts Anti-Proliferative Activity via Promoting p62-Dependent Apoptosis in Human Non-Small-Cell Lung Cancer A549 Cells

“…Subsequently, they were treated with DMSO (0.05%) or the indicated compounds without changing the media for 48h. Cell viability was assessed using the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, as previously described [41]. The absorbance of the treatment group was compared to that of the DMSO-treated control group, which was considered 100%, to calculate cell viability.…”