Mantle cell lymphoma polarizes tumor-associated macrophages into M2-like macrophages, which in turn promote tumorigenesis
Tumor-associated macrophages (TAMs) are recognized as a hallmark of certain solid cancers and predictors of poor prognosis; however, the functional role of TAMs in lymphoid malignancies, including B-cell lymphoma, has not been well defined. We identified infiltration of F4/801 TAMs in a syngeneic mouse model using the recently generated murine mantle cell lymphoma (MCL) cell line FC-muMCL1. Multicolor flow cytometric analysis of syngeneic lymphoma tumors showed distinct polarization of F4/801 TAMs into CD2061 M2 and CD801 M1 phenotypes. Using human MCL cell lines (Mino, Granta, and JVM2), we further showed that MCL cells polarized monocyte-derived macrophages toward an M2-like phenotype, as assessed by CD1631 expression and increased interleukin-10 (IL-10) level; however, levels of the M1 markers CD80 and IL-12 remained unaffected. To show that macrophages contribute to MCL tumorigenesis, we xenografted the human MCL cell line Mino along with CD141 monocytes and compared tumor growth between these 2 groups. Results showed that xenografted Mino along with CD141 monocytes significantly increased the tumor growth in vivo compared with MCL cells alone (P, .001), whereas treatment with liposomal clodronate (to deplete the macrophages) reversed the effect of CD141 monocytes on growth of MCL xenografts (P, .001). Mechanistically, IL-10 secreted by MCL-polarized M2-like macrophages was found to be responsible for increasing MCL growth by activating STAT1 signaling, whereas IL-10 neutralizing antibody or STAT1 inhibition by fludarabine or STAT1 short hairpin RNA significantly abolished MCL growth (P, .01). Collectively, our data show the existence of a tumor microenvironmental network of macrophages and MCL tumor and suggest the importance of macrophages in interventional therapeutic strategies against MCL and other lymphoid malignancies.
Le, K., Sun, J., Khawaja, H., Shibata, M., Maggirwar, S., Smith, M., & Gupta, M. (2021). Mantle cell lymphoma polarizes tumor-associated macrophages into M2-like macrophages, which in turn promote tumorigenesis. Blood Advances, 5 (14). http://dx.doi.org/10.1182/BLOODADVANCES.2020003871