Flavokavain C Suppresses Breast Cancer Cell Viability and Induces Cell Apoptosis by Triggering DNA Damage.

Breast cancer, presented by multiple breast cancer subtypes that coexist within a diagnosed tumor in clinical, has ranked as the most common malignancy in women in recent years. Evidence suggested that limited effective drugs caused the unsatisfactory therapeutic efficacy of breast cancer. Flavokavain C exhibited anticancer activity on colon cancer cells HCT116. It is yet unknown if it can be used to treat breast cancer. This study aims to believe the mechanisms by which Flavokavain C suppresses cell proliferation and the pathways that impact on this effect in breast cancer. 3-(4,5-Dimethythiazol)-2,5-diphenyltetrazolium bromide assay was chosen to evaluate cell cytotoxicity. Colony formation and cell proliferation assays using 5-ethynyl-2'-deoxyuridine staining were performed. Cell cycle progression and apoptosis were examined via flow cytometry and Western blotting, respectively. Five methods (comet assay, immunofluorescence, Western blotting, agarose gel electrophoresis and molecular docking) were used to quantify DNA damage and its cellular response. Compared to cisplatin, Flavokavain C possessed a comparable or more substantial inhibitory effect on breast cancer cell viability while having lower cytotoxicity on human mammary cells. Breast cancer cells treated with Flavokavain C had their colony formation suppressed, DNA replication blocked, the G2/M phase cell cycle arrested, and apoptosis. Furthermore, the results indicated that Flavokavain C would directly interact with DNA and induce DNA cleavage, demonstrating that DNA is an attractive substrate for Flavokavain C. These results suggested that Flavokavain C had strong anticancer activity against multiple subtypes of breast cancer cells.

G-quadruplex stabilizer Tetra-Pt(bpy) disrupts telomere maintenance and impairs FAK-mediated migration of telomerase-positive cells.

G-quadruplex regulates a wide spectrum of biological processes, including telomere maintenance, DNA replication and transcription. The development of small molecules to selectively target G-quadruplex and their application remain hotspots in cancer therapy. Here, we explored the biological effect of G-quadruplexes stabilizer Tetra-Pt(bpy) in telomerase-positive cancer cells. Telomere maintenance was evaluated by telomerase repeat amplification protocol, chromosome orientation fluorescence in situ hybridization and telomere restriction fragment assays. We found that Tetra-Pt(bpy) accelerates telomere shortening through dual inhibition of telomerase activity and telomere sister chromatin exchanges mediated by telomeric G-quadruplexes. Consequently, Tetra-Pt(bpy)-treated cancer cells became enriched with extremely short telomeres and produced a strong telomeric DNA damage response following long-term treatment, leading to cell proliferation inhibition and senescence. Experimental evidence from RNA seq and cell migration-related assays showed that Tetra-Pt(bpy) decreased cell-matrix adhesion and inhibited the migration of non-senescent tumor cells. Mechanistically, Tetra-Pt(bpy) induced the formation of G-quadruplexes in focal adhesion kinase (FAK)-encoding gene PTK2, resulting in FAK transcription inhibition. Tetra-Pt(bpy) reduced xenograft tumor formation and inhibited tumor cell growth and migration in mice. This study further elucidates the function of G-quadruplexes in the human genome and reveals the potential of Tetra-Pt(bpy) as a novel chemotherapeutic agent for targeting telomerase-positive cancer cells.

A chalcone-syringaldehyde hybrid inhibits triple-negative breast cancer cell proliferation and migration by inhibiting CKAP2-mediated FAK and STAT3 phosphorylation.

BACKGROUND: Although triple-negative breast cancer (TNBC) accounts for only 15% of breast cancer cases, it is associated with a high relapse rate and poor outcome after standard treatment. Currently, the effective drugs and treatment strategies for TNBC remain limited, and thus, developing effective treatments for TNBC is pressing. Several studies have demonstrated that both chalcone and syringaldehyde have anticancer effect, but their potential anti-TNBC bioactivity are still unknown. PURPOSE: The present study aimed to synthesize a chalcone-syringaldehyde hybrid (CSH1) and explore its potential anti-TNBC effects and the underlying molecular mechanism. METHODS: Cell cytotoxicity was determined by 3-(4,5-dimethythiazol)-2,5-diphenyltetrazolium bromide (MTT). The activity of cell proliferation was measured by colony formation assay and 5-ethynyl-2'-deoxyuridine (EdU) staining assay. Cell cycle distribution and cell apoptosis were determined by fluorescence-activated cell sorter (FACS). The situation of DNA damage was observed using fluorescence microscopy. The ability of cell-matrix adhesion, migration and invasion was detected using cell adhesion assay and transwell assay. Transcriptome sequencing was performed to find out the changed genes. Levels of various signaling proteins were assessed by western blotting. RESULTS: CSH1 treatment triggered DNA damage and inhibited DNA replication, cell cycle arrest, and cell apoptosis via suppressing signal transducer and activator of transcription 3 (STAT3) phosphorylation. Whole genome RNA-seq analysis suggested that 4% of changed genes were correlated to DNA damage and repair, and nearly 18% of changed genes were functionally related to cell adhesion and migration. Experimental evidence indicated that CSH1 treatment significantly affected the distribution of focal adhesion kinase (FAK) and its phosphorylation, resulting in cell-matrix-adhesion reduction and migration inhibition of TNBC cells. Further mechanistic studies indicated that CSH1 inhibited TNBC cell proliferation, adhesion, and migration by inhibiting cytoskeleton-associated protein 2 (CKAP2)-mediated FAK and STAT3 phosphorylation signaling. CONCLUSION: These results suggest that CKAP2-mediated FAK and STAT3 phosphorylation signaling is a valuable target for TNBC treatment, and these findings also reveal the potential of CSH1 as a prospective TNBC drug.