PURPOSE:

Primary effusion lymphoma (PEL) is an aggressive subtype of non-Hodgkin lymphoma that shows malignant effusion most commonly seen in advanced AIDS patients. In this study, we clarified the potential role of VEGF and IL-6 in PEL fluid retention and evaluated the efficacy of humanized anti-VEGF monoclonal antibody (mAb), bevacizumab, and humanized anti-IL-6 receptor mAb, tocilizumab, against PEL.

METHODS:

The production of VEGF and IL-6, and the expression of IL-6Rα in PEL cell lines were examined. The antiproliferative effect of bevacizumab and tocilizumab on PEL cells was evaluated in vitro. The effect of tocilizumab on VEGF was also examined. An intraperitoneal xenograft mouse model was used for in vivo efficacy.

RESULTS:

Although we found the production of VEGF and IL-6, and the expression of IL-6Rα in PEL cell lines, bevacizumab and tocilizumab did not inhibit the proliferation of PEL cells in vitro. Tocilizumab decreased VEGF mRNA and VEGF production by inhibiting Stat3 phosphorylation and Stat3 binding to VEGF promoter. In a PEL xenograft mouse model that showed profuse ascites, bevacizumab suppressed ascites formation completely, indicating the critical role of VEGF for PEL fluid retention. Tocilizumab also significantly inhibited ascites formation in vivo. Moreover, these mAbs improved the overall survival of treated mice.

CONCLUSIONS:

IL-6-VEGF axis contributed to fluid retention, and bevacizumab and tocilizumab could be effective molecular targeting therapies for PEL.