Beclin 1 gene inhibits tumor growth in colon cancer cell lines.

The Beclin 1 gene binds to the apoptosis-inhibiting protein Bcl-2. The expression and function of the Beclin 1 gene in four colorectal cancer cell lines (HT29, DLD-1, SW480, SW620) was investigated. The expression of Beclin 1 mRNA was examined by reverse transcription-polymerase chain reaction (RT-PCR), the cell growth rate of a stable cell line established after transfection of the Beclin 1 gene into low Beclin 1-expressing HT29 colon cancer cells. In addition, changes in cell cycle were investigated by flow cytometry, and the expression levels of cell cycle related proteins in the Beclin 1 transfected colon cancer cell line were assessed. The expression level of Beclin 1 mRNA in the colon cancer cell lines was variable. Transfection of the low Beclin 1 gene-expressing colon cancer cell line with the Beclin 1 gene resulted in cell growth inhibition. The cell cycle analysis showed that the percentage of GJ-phase cells was significantly higher in Beclin 1 transfectants than in mock transfected cells. The expression levels of cyclin E and phosphorylated Rb were decreased. These results indicate that Beclin 1 can inhibit the growth of colorectal cancer cells.