The purpose of this study is to evaluate the safety of oral azacitidine (CC-486) when combined with R-CHOP (the treatment regimen normally used in treating Diffuse large B-cell lymphoma or Grade 3B follicular lymphoma). This study also proposes to explore the pharmacokinetics of oral azacitidine when administered in combination with R-CHOP and to assess the effects the drug can have on the human body, as well as the ability of CC 486 in combination with R CHOP to further effect the response of tumors associated with Diffuse large B-cell lymphoma or Grade 3B follicular lymphoma, .