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Hygrolidin induces p21 expression and abrogates cell cycle progression at G1 and S phases
Manabu Kawada1, Ihomi Usami, Shun Ohba
1Institute for Chemotherapy, Microbial Chemistry Research Foundation, 18-24 Miyamoto, Numazu-shi, Shizuoka-ken 410-0301, Japan.
Abstract:
Hygrolidin family antibiotics showed selective cytotoxicity against both cyclin E- and cyclin A-overexpressing cells. Among them, hygrolidin was the most potent and inhibited growth of solid tumor-derived cell lines such as DLD-1 human colon cancer cells efficiently more than that of hematopoietic tumor cells and normal fibroblasts. FACS analysis revealed that hygrolidin increased cells in G1 and S phases in DLD-1 cells. While hygrolidin decreased amounts of cyclin-dependent kinase (cdk) 4, cyclin D, and cyclin B, it increased cyclin E and p21 levels. Hygrolidin-induced p21 bound to and inhibit cyclin A-cdk2 complex more strongly than cyclin E-cdk2 complex. Furthermore, hygrolidin was found to increase p21 mRNA in DLD-1 cells, but not in normal fibroblasts. Thus, hygrolidin inhibited tumor cell growth through induction of p21. In respect to p21 induction, inhibition of vacuolar-type (H+)-ATPase by hygrolidin was suggested to be involved.
Insights
Hygrolidin, a potent antibiotic, selectively kills cancer cells by increasing p21 levels, a key protein that halts cell growth. This compound shows promise in targeting solid tumors like colon cancer.
Area of Science:
- Pharmacology
- Molecular Biology
- Oncology
Background:
- The hygrolidin family of antibiotics exhibits selective cytotoxicity.
- Cyclin E and cyclin A overexpression are implicated in certain cancers.
Purpose of the Study:
- To investigate the mechanism of action of hygrolidin, focusing on its selective cytotoxicity against cancer cells.
- To elucidate the role of p21 induction in hygrolidin's anti-tumor effects.
Main Methods:
- Cytotoxicity assays on various cell lines (DLD-1 colon cancer, hematopoietic tumor cells, normal fibroblasts).
- Flow cytometry (FACS) analysis to assess cell cycle distribution.
- Western blotting to quantify protein levels (cyclins, cyclin-dependent kinases, p21).
- Quantitative PCR to measure mRNA levels of p21.
Main Results:
- Hygrolidin demonstrated potent inhibition of solid tumor cell lines, notably DLD-1 human colon cancer cells.
- FACS analysis showed hygrolidin induced G1 and S phase arrest in DLD-1 cells.
- Hygrolidin decreased cyclin-dependent kinase (cdk) 4, cyclin D, and cyclin B, while increasing cyclin E and p21.
- Induced p21 strongly inhibited cyclin A-cdk2 complex and, to a lesser extent, cyclin E-cdk2 complex.
- Hygrolidin increased p21 mRNA levels specifically in DLD-1 cells, not normal fibroblasts.
- Inhibition of vacuolar-type (H+)-ATPase was suggested to be involved in p21 induction.
Conclusions:
- Hygrolidin effectively inhibits tumor cell growth, particularly in solid tumors, through the induction of p21.
- The mechanism involves cell cycle arrest at G1/S phases and modulation of key cell cycle regulatory proteins.
- p21 induction by hygrolidin, potentially linked to vacuolar-type (H+)-ATPase inhibition, is a critical factor in its anti-cancer activity.