Dual Roles of T/NK Immunomodulatory and Anti-Tumor Properties for Selected Herbal Medicines in Multiple Myeloma Therapy.

Thalidomide is one of the current therapies for multiple myeloma (MM) which has multiple mechanisms on myeloma cells, bone marrow microenvironment, T cells and NK cells. Chinese herbal medicines have been used in the treatment of cancer and also have multiple pharmacological activities; however, there is a strong need for evidence-based scientific data to understand their anti-cancer mechanisms. The aim of this study is to integrate thalidomide and Chinese herbs to enhance the beneficial effects and minimize the side-effects of thalidomide. The melanins from an anti-cancer Chinese herb Ligustrum lucidum were extracted and tested. The dual roles of the herbal extracts on T/NK immunomodulatory and anti-tumor properties were investigated in the following three aspects:

1. Proliferation measured by both [³H] thymidine assays and CFSE assays;

2. Cell survival measured by propidium iodide exclusion and trypan blue staining; and

3. NK cytotoxicity using myeloma cell line 8226 as target cell labeled with CalceinAM, and peripheral blood mononuclear cells (PBMC) from healthy subjects as the source of effector cells.

It was found that in the [³H] thymidine assays, Ligustrum lucidum melanin (LLM) extracts exhibited both stimulatory effect on PBMC proliferation and inhibitory effects on myeloma cell line 8226 proliferation at the concentration of 0.02 to 20 μg/ml. The stimulatory effect on PBMC was also observed with CFSE assays when PBMC was incubated with LLM (20 μg/ml) for 2 days with a proliferated population of 33%, compared with thalidomide (5 μg/ml) 57%, and control, 12%. In the cell survival assay tumor cell line NK92-MI was completely inhibited by LLM (20 μg/ml). NK cytotoxicity assay showed the LLM (0.02 to 20 μg/ml) showed dose response increase of cytotoxic effects of NK cells from 50% to 70%, higher than 42% achieved by thalidomide (5 μg/ml). These results indicate that herbal medicine Ligustrum lucidum posses both T cell / NK cell immunomodulatory effects and anti-tumor effects to myeloma cells. Further works will be to determine the structure of the plant constituent and to assess the synergistic combinations of the active extracts and constituents with thalidomide in the cellular assays.