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The study investigated the effect of 17β-estradiol on polyamine oxidase (PAOX) expression in estrogen receptor-positive MCF-7 breast cancer cells. It was found that 17β-estradiol significantly reduced both PAOX mRNA and protein levels. The repression of PAOX was mediated by estrogen receptor 2 (ESR2), as shown by experiments using selective ESR antagonists and knockdown of ESR members. A luciferase reporter assay indicated that 17β-estradiol downregulated PAOX promoter activity, and this effect was lost when specific activator protein 1 (AP-1) binding sites in the PAOX promoter were deleted or mutated. Chromatin immunoprecipitation analysis confirmed that ESR2 interacts with AP-1 at these sites. The findings suggested that 17β-estradiol represses PAOX transcription through ESR2's interaction with AP-1, implying that estrogen deficiency could lead to increased PAOX expression and decreased polyamine levels.

The study investigated the use of letrozole- and quercetin-loaded spanlastics for enhanced cytotoxicity against MCF-7 breast cancer cells. The spanlastics were prepared with different edge activators and evaluated for particle size, surface charge, and encapsulation efficiency. The optimized formulations showed sustained drug release and effective skin permeation. The combination of letrozole and quercetin in spanlastics demonstrated superior in vitro cytotoxicity, cell cycle arrest, and increased reactive oxygen species production compared to individual treatments and soluble free drugs. These findings suggested that the combination therapy could improve breast cancer management through transdermal drug delivery.

The study investigated the formulation of a nanosuspension containing kenikir leaf extract, known for its anticancer properties, to enhance its effectiveness against MCF-7 breast cancer cells. Using the ionic gelation method with varying concentrations of PVP K-30 stabilizer, the formula with 5% PVP showed the highest entrapment efficiency (85.04±0.08%) and optimal characteristics, including a particle size of 221.9 nm and a zeta potential of -21.7 mV. The nanosuspension demonstrated significant cytotoxic activity, inhibiting MCF-7 cell proliferation by 23.7% at a concentration of 10 μg/mL, suggesting its potential as a complementary therapy for breast cancer.