Ex vivo conditioning with IL-12 protects tumor-infiltrating CD8+ T cells from negative regulation by local IFN-γ.

Optimal ex vivo expansion protocols for adoptive cell therapy (ACT) must yield T cells able to effectively home to tumors and survive the inhospitable conditions of the tumor microenvironment (TME), while simultaneously exerting persistent anti-tumor effector functions. Our previous work has shown that ex vivo activation in the presence of IL-12 can induce optimal expansion of murine CD8+ T cells, thus resulting in significant tumor regression after ACT mostly via sustained secretion of IFN-γ. In this report, we further elucidate the mechanism of this potency, showing that IL-12 additionally counteracts the negative regulatory effects of autocrine IFN-γ. IL-12 not only downregulates PD-1 expression by T cells, thus minimizing the effects of IFN-γ-induced PD-L1 upregulation by tumor stromal cells, but also inhibits IFNγR2 expression, thereby protecting T cells from IFN-γ-induced cell death. Thus, the enhanced anti-tumor activity of CD8+ T cells expanded ex vivo in the presence of IL-12 is due not only to the ability of IL-12-stimulated cells to secrete sustained levels of IFN-γ, but also to the additional capacity of IL-12 to counter the negative regulatory effects of autocrine IFN-γ.

Mechanisms of Tumor-Induced Lymphovascular Niche Formation in Draining Lymph Nodes.

Enlargement of the lymphatic vascular network in tumor-draining lymph nodes (LNs) often precedes LN metastasis, likely providing a lymphovascular niche for tumor cells. We investigated morphological and molecular changes associated with the lymphatic remodeling process, using the 4T1 breast cancer and B16F10 melanoma models. Lymphatic expansion in tumor-draining LNs is mediated by sprouting and proliferation of lymphatic endothelial cells (LECs) as early as 4 days after tumor implantation. RNA sequencing revealed an altered transcriptional profile of LECs from tumor-draining compared to naive LNs with similar changes in both tumor models. Integrin αIIb is upregulated in LECs of tumor-draining LNs and mediates LEC adhesion to fibrinogen in vitro. LEC-associated fibrinogen was also detected in LNs in vivo, suggesting a role of integrin αIIb in lymphatic remodeling. Together, our results identify specific responses of LN LECs to tumor stimuli and provide insights into the mechanisms of lymphovascular niche formation in tumor-draining LNs.

Myosin 1e promotes breast cancer malignancy by enhancing tumor cell proliferation and stimulating tumor cell de-differentiation.

Despite advancing therapies, thousands of women die every year of breast cancer. Myosins, actin-dependent molecular motors, are likely to contribute to tumor formation and metastasis via their effects on cell adhesion and migration and may provide promising new targets for cancer therapies. Using the MMTV-PyMT murine model of breast cancer, we identified Myosin 1e (MYO1E) as a novel tumor promoter. Tumor latency in mice lacking MYO1E was significantly increased, and tumors formed in the absence of MYO1E displayed unusual papillary morphology, with well-differentiated layers of epithelial cells covering fibrovascular cores, rather than solid sheets of tumor cells typically observed in this cancer model. These tumors were reminiscent of papillary breast cancer in humans that is typically non-invasive and often cured by tumor excision. MYO1E-null tumors exhibited decreased expression of the markers of cell proliferation, which was recapitulated in primary tumor cells derived from MYO1E-null mice. In agreement with our findings, meta-analysis of patient survival data indicated that MYO1E expression level was associated with reduced recurrence-free survival in basal-like breast cancer. Overall, our data suggests that MYO1E contributes to breast tumor malignancy and regulates the differentiation and proliferation state of breast tumor cells.