| Since RB signaling to Cdk 2 is disrupted in these tumor cells , we co expressed two proteins that cooperate with RB in transcriptional repression , AHR and BRG 1 , in an attempt to correct this signaling dysfunction . ^^^ Co expression of AHR / BRG 1 with PSM RB attenuated Cyclin A and Cdk 2 expression as well as Cdk 2 associated kinase activity , resulting in cell cycle inhibition of C33A cells . ^^^ Importantly , ectopic expression of Cyclin A was able to reverse the arrest mediated by co expression of AHR / BRG 1 with PSM RB . ^^^ |