Macrophages and angiogenesis in human lymphomas

A link exists between chronic inflammation and cancer and immune cells, angiogenesis, and tumor progression. In hematologic malignancies, tumor-associated macrophages (TAMs) are a significant part of the tumor microenvironment. Macrophages are classified into M1/classically activated and M2/alternatively activated. In tumors, TAMs are mainly constituted by M2 subtype, which promotes angiogenesis, lymphangiogenesis, repair, and remodeling, suppressing adaptive immunity, increasing tumor cell proliferation, drug resistance, histological malignancy, and poor clinical prognosis. The aim of our review article is to define the role of TAMs and their relationship with the angiogenesis in patients with lymphoma reporting both an analysis of main published data and those emerging from our studies. Finally, we have discussed the anti-angiogenic approach in the treatment of lymphomas.

Angiogenesis and antiangiogenic therapy in non-Hodgkin's lymphoma

Angiogenesis, the growth of new blood vessels, requires dynamic expansion, assembly and stabilization of vascular endothelial cells in response to proangiogenic stimuli. Antiangiogenic strategies have become an important therapeutic modality for solid tumors. While many aspects of postnatal pathological angiogenesis have been extensively studied in the context of nonhematopoietic neoplasms, the precise role of these processes in lymphoma pathogenesis is under active investigation. Lymphoma growth and progression is potentiated by at least two distinct angiogenic mechanisms: autocrine stimulation of tumor cells via expression of vascular endothelial growth factor (VEGF) and VEGF receptors by lymphoma cells, as well as paracrine influences of proangiogenic tumor microenvironment on both local neovascular transformation and recruitment of circulating bone marrow-derived progenitors. Lymphoma-associated infiltrating host cells including hematopoietic monocytes, T cells and mesenchymal pericytes have increasingly been associated with the pathogenesis and prognosis of lymphoma, in part providing perivascular guidance and support to neoangiogenesis. Collectively, these distinct angiogenic mechanisms appear to be important therapeutic targets in selected non-Hodgkin's lymphoma (NHL) subtypes. Understanding these pathways has led to the introduction of antiangiogenic treatment strategies into the clinic where they are currently under assessment in several ongoing studies of NHL patients.

Immunomodulatory drugs Revlimid (lenalidomide) and CC-4047 induce apoptosis of both hematological and solid tumor cells through NK cell activation

Revlimid (Lenalidomide, CC-5013) and CC-4047 are IMiDs immunomodulatory drugs that have been described as having immunomodulatory properties and anti-tumor activity. Here we report proapoptotic effects of CC-5013 and CC-4047 on tumor cells in a co-culture model of PBMC and tumor cells. CC-5013 and CC-4047 enhanced PBMC activity leading to tumor cell apoptosis in K562/PBMC co-culture model. We also demonstrate that the natural killer (NK) cell population of PBMC was essential in inducing K562 apoptosis. Increases of NK and natural killer T (NKT) cell populations by CC-5013 and CC-4047 was observed along with modulation of NK cell CD56 adhesion marker. In addition, our data indicate that NK activation by CC-4047 was dependent on other cell types of PBMC. We expanded the application of K562/PBMC co-culture model to other hematological and solid tumors. In Raji/PBMC co-culture model, CC-5013 and CC-4047 dose-dependently augmented tumor cell apoptosis. Pre-treatment of Raji cells with Rituximab further enhanced apoptosis induced by CC-5013 or CC-4047-treated PBMC. Moreover, CC-5013 and CC-4047 significantly increased PC-3 prostate cancer cell apoptosis in PC-3/PBMC co-culture, either as single agent or in combination with Docetaxel. Together, the results reveal that co-culture models are suitable cellular systems to assess anti-tumor activities of these compounds. Our findings support clinical evaluation of CC-5013 and CC-4047 in relapsed NHL with Rituximab and in prostate cancer with Docetaxel.

Antibody Therapy in Aggressive Lymphomas

The aggressive lymphomas are potentially curable. The natural history of certain aggressive lymphomas has been altered by monoclonal antibody therapy. Targeted monoclonal antibody therapy to the CD20 antigen has altered the outcome of patients with diffuse large B-cell lymphoma in patients of all ages. Anti-CD20–based radioimmunoconjugates are being evaluated as radioimmunotherapy approaches in patients who have relapsed and in stem cell transplant settings. Antibody-directed therapy to the B-cell–specific antigen CD22 are ongoing. New approaches include different CD20 antibodies and an antibody to the CD40 antigen, which is a member of the tumor necrosis factor (TNF) receptor family, which is expressed on B-cells. Antibody therapy has been incorporated into CHOP (cyclophosphamide, adriamycin, vincristine, prednisone) therapy and other regimens such as EPOCH (etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin) and HyperCVAD (cyclophosphamide, vincristine, adriamycin, dexamethasone). Single-agent anti-CD20 therapy is active in the post-transplantation lymphoproliferative disorders. T-cell antibodies are under evaluation in a number of T-cell lymphoproliferative disorders. Targeted therapy has changed the natural history of a number of aggressive non-Hodgkin lymphomas. This review will describe the contributions of antibody therapies to the treatment of these diseases.