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Diallyl disulfide induces ERK phosphorylation and alters gene expression profiles in human colon tumor cells
1Graduate Program in Nutrition and the Nutrition Department, The Pennsylvania State University, University Park, PA 16802, USA.
Abstract:
Diallyl disulfide (DADS), a compound found in processed garlic, has been shown to arrest unsynchronized human colon tumor cells (HCT-15) in the G(2)/M phase of the cell cycle. The present studies were designed to examine whether this cell cycle block related to alterations in protein kinase C (PKC), Ca(2+)/calmodulin-dependent protein kinase II (CAMK II) or extracellular signal-regulated kinase (ERK) activity. Exposing double thymidine synchronized HCT-15 cells to DADS (25, 50 and 100 micromol/L) for 4 h increased the G(2)/M population by 30, 31 and 63%, respectively, compared with controls (P < 0.05). PKC and CAM KII activities were not influenced by increasing DADS exposure and thus did not correlate with the block of cells in the G(2)/M phase. Although ERK activity increased by 44 and 60% after treatment with 100 and 500 micromol/L DADS (P < 0.05), it was not influenced by exposure to 25 or 50 micromol/L DADS. Western blot analysis revealed that although DADS (25, 50, 100 and 500 micromol/L) did not influence the quantity of ERK protein expressed, it did increase its phosphorylation by 39, 52, 73 and 61%, respectively, compared with controls (P < 0.05). These studies provide evidence that early alterations in ERK pathway signaling may contribute to the G(2)/M arrest observed after DADS exposure. Preliminary data generated using the Clonetech Atlas Human Cancer cDNA Expression Array suggest that alterations in cell cycle, DNA repair and cellular adhesion factors accompany DADS exposure and may also be involved in mediating the block in G(2)/M progression.
Insights
Diallyl disulfide (DADS) from garlic halts colon tumor cells in G2/M phase. This cell cycle arrest is linked to early changes in extracellular signal-regulated kinase (ERK) pathway signaling.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Diallyl disulfide (DADS), a garlic compound, induces G2/M cell cycle arrest in human colon tumor cells (HCT-15).
- The precise molecular mechanisms underlying DADS-induced cell cycle arrest require further elucidation.
Purpose of the Study:
- To investigate the role of protein kinase C (PKC), Ca(2+)/calmodulin-dependent protein kinase II (CAMK II), and extracellular signal-regulated kinase (ERK) in DADS-mediated G2/M cell cycle arrest.
- To explore potential downstream signaling pathways involved in DADS's effect on colon cancer cells.
Main Methods:
- HCT-15 cells were synchronized and treated with varying concentrations of DADS.
- Cell cycle progression was analyzed using flow cytometry.
- Protein kinase activities and phosphorylation levels were assessed.
- Western blot analysis was performed to evaluate ERK protein expression and phosphorylation.
- Gene expression profiling was conducted using Clonetech Atlas Human Cancer cDNA Expression Array.
Main Results:
- DADS treatment significantly increased the percentage of cells in the G2/M phase in a dose-dependent manner.
- PKC and CAMK II activities were not significantly affected by DADS.
- ERK activity and phosphorylation were increased by higher concentrations of DADS, suggesting pathway activation.
- DADS did not alter ERK protein expression but enhanced its phosphorylation.
- Preliminary data indicated alterations in cell cycle, DNA repair, and cellular adhesion factors.
Conclusions:
- Early alterations in ERK pathway signaling likely contribute to the G2/M cell cycle arrest induced by DADS.
- DADS may exert its anti-cancer effects through modulation of ERK signaling and other cellular processes.
- Further research is warranted to fully understand the complex mechanisms of DADS in colon cancer therapy.