# The Mediterranean Sea on the Bench: Unveiling the Marine Invertebrate Sidnyum elegans as a Source of Novel Promising Therapeutic Tools Against Triple-Negative Breast Cancer

## TL;DR

This study explores a marine invertebrate from the Mediterranean Sea as a potential source of new treatments for triple-negative breast cancer.

## Contribution

The study identifies and characterizes a novel bioactive fraction from Sidnyum elegans with anti-cancer properties.

## Key findings

- SEB-5 fraction significantly reduced cell proliferation and induced apoptosis in MDA-MB-231 cells.
- SEB-5 arrested cells in the G0/G1 phase and reduced the expression of cell cycle-related genes.
- SEB-5 showed antimetastatic potential by inhibiting cell migration in a wound-healing assay.

## Abstract

This study aims to unveil the marine invertebrate Sidnyum elegans, a Mediterranean ascidian, as a natural resource for the early development of new treatments for triple-negative breast cancer (TNBC). Nine different fractions obtained via medium-pressure liquid chromatography (MPLC) of the butanol-soluble material of the ascidian were evaluated in proliferating MDA-MB-231 cells in a range of 10–50 µg/mL. Among them, the SEB-5 fraction was found to be the most effective in reducing cell proliferation and concomitantly inducing apoptosis, revealed via MTT assay and FACS analysis using Annexin V/PI dual staining. Furthermore, we investigated the effect of this fraction on cell cycle phases, revealing that SEB-5 can arrest the cells in the G0/G1 phase. This latter effect was then confirmed via transcriptomic analysis, showing that treatment with SEB-5 reduced the expression of cyclinB1, CDC25a, and CDK1. Finally, to evaluate the potential antimetastatic effect of SEB-5, a wound-healing assay was performed showing the ability of SEB-5 to reduce MDA-MB-231 cell migration. The chemical characterization of SEB-5 components was performed using liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS/MS) and nuclear magnetic resonance (NMR) spectroscopy. This analysis revealed the presence of a terpenoid and polyketide-like compounds, including the alkyl sulfate 1 and phosphoeleganin 2, along with three novel phosphoeleganin-related products 3–5.