Natural Bioactive Compounds, Vegetal Extracts and Modern Pharmaceutical Formulations: New Insights into the Anti-Cancer Mechanism of Action

New insights into the cytotoxic effects of Thymus vulgaris essential oil on the human triple-negative breast cancer cell line MDA-MB-231

Essential oils (EOs) are natural products that have gained wide interest due to their biological activities and anticancer properties through various mechanisms. The present study aimed to test the cytotoxicity of Thymus vulgaris L. (thyme) EO of Italian origin, rich in thymol (49.6%) and p-cymene (18.8%), towards the triple-negative breast cancer cell line MDA-MB-231 and to investigate the biochemical mechanisms underlying its antitumor activity. Thyme EO reduced cancer cell viability in a dose-dependent manner after 24 h treatment, with an IC50 value equal to 75.1 ± 15.2 μg/ml; simultaneously, the inhibition of cancer cell migration and colony formation capacity was evidenced. Thyme EO antiproliferative effects were related to the induction of apoptosis as demonstrated by the increased expression of the pro-apoptotic proteins Bax, cleaved caspase-3, phospho-p53, and SMAC/Diablo and by the reduction of the anti-apoptotic proteins Bcl-2, cIAP-1, cIAP-2, HIF-1α, survivin, and XIAP. Thyme EO administration led to the early formation of intracellular ROS, followed by the increment of MDA as an index of lipid peroxidation and by the decreased expression of the antioxidant enzymes catalase and PON2. The upregulation of Nrf2 mRNA expression and the strong induction of HO-1 sustained the activation of the Nrf2 pathway by thyme EO. These data showed that the EO from Thymus vulgaris L. might inhibit the malignant phenotype of MDA-MB-231, thus suggesting potential benefits against human triple-negative breast cancer.

Bombyx batryticatus Cocoonase Inhibitor Separation, Purification, and Inhibitory Effect on the Proliferation of SMCC-7721 HeLa-Derived Cells

The present study was to isolate and purify Bombyx batryticatus cocoonase inhibitor (BBCI) and to evaluate its inhibitory effect on the proliferation of SMCC-7721 cells. BBCI was purified from the crude proteins of Bombyx batryticatus using affinity chromatography with cocoonase as the ligand, its N-terminal amino acid sequence was determined using the Edman degradation method, and its inhibiting activity on SMCC-7721 cell proliferation was detected in vitro using the MTT method and in vivo in tumor-bearing nude mice. The purified BBCI presented as a single band in SDS-PAGE, the molecular weight determined by time-of-flight mass spectrometry was 13,973.63 Da, and its N-terminal amino acid sequence was VRNKRQSNDD. BBCI was a noncompetitive cocoonase inhibitor with an average Michaelis constant of 76.50, and it inhibited cocoonase activity with an inhibition ratio of 1 : 1 (molar). BBCI could inhibit the proliferation of SMCC-7721 cells in vitro with the IC₅₀ being about 260.52 μg/ml within 36 h of treatment and inhibit the SMCC-7721 tumor growth in nude mice by subcutaneous injection of BBCI around the tumor, where the tumor inhibitory effect was dose dependent. BBCI did not significantly influence the spleen coefficient of the mice. In conclusion, to the best of our knowledge, the present study is the first to report that BBCI, which was purified from Bombyx batryticatus, was a serine proteinase inhibitor with antitumor activity.