I did Real-time quantitative RT-PCR for some mRNA coding genes in U-87 MG cell line. I used GAPDH as an endogenous control gene for this gene expression assessment, due to its stable expression across the test sample set . I suggest you try this. Good luck

it depends what sort of gene you look at,

i used U6 and it works great HPRT AND GAPDH  are not bad

Thank you for your complete answer.