RATIONALE: Monoclonal antibodies, such as rituximab, can locate cancer cells and either kill them or deliver cancer-killing substances to them without harming normal cells. Drugs used in chemotherapy, such as cyclophosphamide, doxorubicin, vincristine, and prednisone, use different ways to stop cancer cells from dividing so they stop growing or die. Oblimersen may increase the effectiveness of a chemotherapy drug by making cancer cells more sensitive to the drug. Combining oblimersen with rituximab and combination chemotherapy may kill more cancer cells.