The IMiDs® Immunomodulatory Drugs Revlimid® (Lenalidomide) and CC-4047 Induce Growth Arrest and Apoptosis in NHL Tumor Cells In Vitro.

IMiDs^® immunomodulatory drugs are thalidomide analogues that have been developed for improved anti-cancer and anti-inflammatory properties and decreased side effects. Many IMiDs^® immunomodulatory drugs have been shown to have activities in hematologic cancers and solid malignancies, as well as having profound effects on the bone marrow microenvironment. Specifically in NHL, it was shown that addition of Revlimid^® or CC-4047 to Rituxan enhances anti-tumor activity in a SCID mouse lymphoma model.

Here we tested the direct effects of Revlimid^® and CC-4047 on NHL tumor cells by treating Raji cells with each drug alone or with each drug in combination with anti-CD20 antibodies B1 and Rituxan. CC-4047 alone caused up to 40% inhibition of proliferation at 10 μM in Raji cells, which corresponded to G1 arrest. In combination with B1, CC-4047 showed a small additive effect at 10 μM while Revlimid^® effects were minimal up to 10 μM. In combination with Rituxan, CC-4047 showed a slight additive effect at 10 μM and Revlimid^® at 50 μM.

We have also developed a co-culture assay of PBMC and NHL tumor cells as an in vitro model of tumor-host immune system interaction, to further explore the anti-tumor potential of the drugs in NHL. This assay is non-radioactive and flow cytometry based. In this co-culture system using Raji and PBMC, we have shown that pre-treatment of PBMC with Revlimid^® or CC-4047 can enhance the PBMC activity in inducing Raji cell apoptosis in a dose dependent manner. In addition, our data indicate that pre-treatment of Raji cells with Rituxan can further enhance the apoptosis induced by PBMC pre-treated with Revlimid^® or CC-4047. Since minimal additive effect between each drug and Rituxan was observed in the Raji single tumor cell model, these studies suggest that the co-culture system is a more appropriate cellular model to assess the anti-tumor activities of certain IMiDs^® immunomodulatory drugs. This system can reveal the effects of certain IMiD^® immunomodulatory drugs not observable with single tumor cell proliferation models.

In summary, our data clearly demonstrate that Revlimid^® and CC-4047 directly induce NHL tumor cell growth arrest and effectively enhance tumor cell apoptosis induced by PBMC. These results support clinical evaluation of Revlimid^® and certain IMiDs^® immunomodulatory drugs in relapsed B-cell NHL in combination with Rituxan.