Analysis of replication timing using synchronized budding yeast cultures

Echinacea Angustifolia DC Extract Induces Apoptosis and Cell Cycle Arrest and Synergizes with Paclitaxel in the MDA-MB-231 and MCF-7 Human Breast Cancer Cell Lines

BACKGROUND

Echinacea spp. displays different biological activities, such as antiviral, immunomodulatory, and anticancer activities. Currently, high sales of hydroalcoholic extracts of Echinacea have been reported; hence, the importance of studies on Echinacea.

AIM

To establish the effects of Echinacea angustifolia DC extract obtained with ethyl acetate (Ea-AcOEt) in breast cancer cell lines.

METHODS

Cytotoxicity, cell cycle arrest, and cell death were evaluated. Besides, the safety of the extract, as well as its effect in combination with paclitaxel were investigated.

RESULTS

The echinacoside and caffeic acid content in the Ea-AcOEt extract were quantified by HPLC, and its antioxidant activity was assessed. The Ea-AcOEt extract showed cytotoxic activity on breast cancer MDA-MB-231 cells (IC₅₀ 28.18 ± 1.14 µg/ml) and MCF-7 cells (19.97 ± 2.31 µg/ml). No effect was observed in normal breast MCF-10 cells. The Ea-AcOEt extract induced cell cycle arrest in the G1 phase and caspase-mediated apoptosis. No genotoxicity was found in vitro or in vivo, and the extract showed no signs of toxicity or death at 2,000 mg/kg in rodents. In vitro, the combination of Ea-AcOEt extract and paclitaxel showed a synergistic effect on both cancer cell lines.

CONCLUSION

The Ea-AcOEt extract is a potential candidate for breast cancer treatment.

Incision of damaged DNA in the presence of an impaired Smc5/6 complex imperils genome stability

The Smc5/6 complex is implicated in homologous recombination-mediated DNA repair during DNA damage or replication stress. Here, we analysed genome-wide replication dynamics in a hypomorphic budding yeast mutant, smc6-P4. The overall replication dynamics in the smc6 mutant is similar to that in the wild-type cells. However, we captured a difference in the replication profile of an early S phase sample in the mutant, prompting the hypothesis that the mutant incorporates ribonucleotides and/or accumulates single-stranded DNA gaps during replication. We tested if inhibiting the ribonucleotide excision repair pathway would exacerbate the smc6 mutant in response to DNA replication stress. Contrary to our expectation, impairment of ribonucleotide excision repair, as well as virtually all other DNA repair pathways, alleviated smc6 mutant's hypersensitivity to induced replication stress. We propose that nucleotide incision in the absence of a functional Smc5/6 complex has more disastrous outcomes than the damage per se. Our study provides novel perspectives for the role of the Smc5/6 complex during DNA replication.