Expression of CD44st in MCF-7, MCF-7/neo, and MCF-7/CD44st cells. RT-PCR products were run on an agarose gel to indicate the expression levels of the CD44st gene and β-actin gene. The anticipated 1023-bp product for CD44st was present in MCF-7/CD44st cells. The β-actin gene was amplified using semi-quantitative RT-PCR and used as a loading control. The 330-bp product for β-actin gene expression was present in all cells.