|M.Sc Student||Saadi Hitam|
|Subject||Microenvironment-Mediated Growth and Progression of Mantle|
|Department||Department of Medicine||Supervisors||Dr. Netanel Horowitz|
|Dr. Tamar Katz|
Mantle cell lymphoma (MCL) is an aggressive and incurable B-cell malignancy characterized by dissemination of lymphoma cells in different compartments, mainly lymph nodes (LN) and bone marrow (BM). The interaction between lymphoma cells and their tumor microenvironment (TME) is known to have an impact on malignant cell behavior. The lymphoma-stroma cross-talk is found to increase cell survival, dissemination and resistance to anti-cancer therapy, but these effects may vary between different TME niches. Several novel drugs are reported to be highly efficient in MCL therapy, inhibiting lymphoma cell proliferation, adhesion and supporting anti-cancer immune attacks. However, the pro-tumor effect of specific TME niches is unknown. The current study aimed to explore the interaction between MCL cells and stroma cells derived from different sources, focusing on their effects on lymphoma cell survival, trafficking and response to Ibrutinib.
In this research we found that LN stroma secrete higher SDF1 levels, and induced extensive MCL cells migration compared to BM stromal cells. This migration to LN stroma was significantly impaired after AMD3100 treatment. However, AMD3100 treatment have no effect on MCL migration capacity to BM stroma. In addition, BM stromal cells expressed significantly higher levels of chemokines CCL20, MCP-1 and RANTES compared with LN stromal cells. The latter results indicated that migration of MCL cells to LN stroma is SDF1-CXCR4 axis dependent, however, another soluble factors involved in BM-stroma induced migration.
The protecting effect of TME on Ibrutinib-induced cell apoptosis depended on the TME source. Co-culture of MCL cells with BM and LN stroma resulted in a significant increase in lymphoma cell survival, which was superior in the BM stroma (45% vs. 25%). Resistance to Ibrutinib was also observed under non-contact conditions, which was also higher in BM stroma, suggesting the involvement of stroma secreted factors. Consistent with these findings, following co-culture of MCL cells with BM stroma, the secretion of pro-survival cytokines IL-6, IL-8, VEGF and the chemokine RANTES/CCL5 was significantly augmented compared to co-culture with LN stroma. Comparison of the results in the different conditions (contact vs. non-contact), showed that the protection under non-contact conditions was significantly inferior compared to contact conditions in the co-culture of MCL with BM stroma. However, in co-culture with LN stroma was no different in protection capability. Furthermore, co-culture of MCL cells with BM stroma, showed a significant increase in adhesion molecule expression on lymphoma cells compared to co-culture with LN stroma, suggesting that BM stroma protection dependent in both soluble factors and cell-cell contact, dissimilar to survival induced by LN stroma which dependent in soluble factors only. In vivo experiment revealed that the tumor growth observed in mice receiving MCL mixed with BM stromal cells was more robust than in mice injected with MCL mixed with LN stromal cells.
Our results suggest that the critical role of TME in supporting MCL cell survival and dissemination is context-dependent. MCL response to Ibrutinib varies between surrounding milieus. Therefore, the therapy should not only target tumor cell-specific mechanisms, but should also be adjusted to particular TME niches.