Micromeria fruticosa and Foeniculum vulgare essential oils inhibit melanoma cell growth and migration by targeting MMP9 and NFkB signaling
Authors: Salama Yousef , Al-Maharik Nawaf 
Published: January 2024

Abstract
Background
Fennel (Fe), also known scientifically as Foeniculum vulgare, and Micromeria fruticose are herbaceous plants endemic to the Mediterranean Region. The use of their essential oils for their health-promoting effects has been seen in Middle-Eastern societies, where they have been used as a type of traditional medicine. These oils have been used to treat a variety of diseases, including headaches, abdominal pains, skin and eye infections, colds, and wounds. This study looks at the chemical makeup of essential oils extracted from Palestine-grown fennel seeds and Micromeria fruticose leaves. The anticancer properties of each essential oil, as well as the combined mixture of both oils, were evaluated against the melanoma cell line.

Results
GC–MS was used to study the essential oils (EOs) from Micromeria fruticose leaves and fennel seeds that were extracted by hydrodistillation. Analysis of M. fruticose EO allowed the identification of 20 compounds, accounting for 97.73% of the EO's overall composition, with pulegone (81.77%), β-caryophyllene (2.95%), isomenthone (2.17%), piperitenone oxide (1.78%), and p-mentha-3-en-8-ol (1.38%) being the primary components. 24 phytochemicals were identified in the essential oil of fennel seeds, accounting for 100% of its composition, of which trans-anethole (93.69%), fenchone (3.93%), and sylvestrene (0.83%) were the major constituents. Although the EOs derived from M. fruticosa leaves and fennel seeds have shown potential for inhibiting the growth of several types of cancer, their impact on the proliferation and migration of melanoma cells has not been investigated. The results of our study demonstrate that the application of both oils, either separately or in combination (referred to as Mix-EO therapy), effectively suppressed the growth of melanoma cells in a manner that was dependent on the dosage. Furthermore, both treatments resulted in the upregulation of pro-apoptotic Bax and the downregulation of apoptosis-inhibiting Bcl2 expression in an in vitro setting. The anti-proliferative effects were confirmed using a murine melanoma model in vivo. Furthermore, both the individual EOs that were assessed and their combination (Mix-EO) exhibited inhibitory properties against the migration of melanoma cells. Both EOs and Mix-EO were found to decrease the intracellular levels of the transcription factor nuclear factor kappa B (NFkB) and one of its downstream targets, matrix metalloproteinase9 (MMP9), in melanoma and tumor-associated mesenchymal stem cells. Finally, we demonstrate for the first time that EOs from M. fruticose leaves, fennel seeds, and their combination exert anti-cancer characteristics by inhibiting NFkB and MMP9 in melanoma (autocrine) and tumor-associated mesenchymal stem (paracrine) cells, thereby inducing melanoma cell apoptosis and preventing cell migration.

Conclusions
The findings of our investigation indicate that the EOs derived from the fennel seeds and the M. fruticose leaves encompass a diverse array of biologically active chemicals, which have robust anticancer effects. The results of this study hold promise for application in the advancement of innovative natural medications. Additional investigation is required to delve into the medicinal capacity of these essential oils in biological entities.

Graphical Abstract