Chemotherapy for Participants With Lymphoma

The primary purpose of this study is to help answer the following research questions: * To assess whether Enzastaurin combined with rituximab, gemcitabine and oxaliplatin (R-GEMOX) can help participants with Diffuse Large B-Cell Lymphoma (DLBCL) remain free from disease and thus live longer. * To assess for any side effects that might be associated with enzastaurin and R-GEMOX . * To look at the characteristics and levels of certain genes and proteins to learn more about DLBCL and how enzastaurin works in the body. * To look at the level of enzastaurin in the body and how long it remains.