Wnt Inhibition Sensitizes PD-L1 Blockade Therapy by Overcoming Bone Marrow-Derived Myofibroblasts-Mediated Immune Resistance in Tumors

Cancer-associated fibroblasts (CAFs) has been recognized as one cause of tumor resistance to immune checkpoint blockade therapy, but the underlying mechanisms still remain elusive. In the present study, a bone marrow-derived CAF (BMF) -rich tumor model is successfully established by subcutaneously mixed inoculation of BMFs and tumor cells into mice and the BMF-mixed tumor xenografts are demonstrated to be resistant to anti-PD-L1 antibody immunotherapy compared to the mere tumor xenografts. In vitro assays via the co-culture system of BMFs and tumor cells indicate that the co-cultured BMFs are induced to overexpress PD-L1, while there is no such a phenomenon in the co-cultured cancer cells. The further knock-out of PD-L1 in BMFs rescues the sensitivity of BMF-mixed tumor xenografts to PD-L1 blockade therapy. Mechanistically, via the microarray assay, we identify that the upregulation of PD-L1 in BMFs stimulated by cancer cells is medicated by the activation of the Wnt/β-catenin signaling pathway in BMFs. Moreover, the administration of Wnt/β-catenin signaling inhibitors, including XAV-939 and Wnt-C59, distinctly inhibits the upregulation of PD-L1 expression in the co-cultured BMFs. The further combination administration of XAV-939 significantly potentiates the therapeutic outcome of PD-L1 blockade therapy in BMF-mixed tumors. In summary, our study demonstrates that Wnt inhibition augments PD-L1 blockade efficacy by overcoming BMF-mediated immunotherapy resistance.

Bone Marrow-Derived Myofibroblasts Promote Gastric Cancer Metastasis by Activating TGF-β1 and IL-6/STAT3 Signalling Loop

Background

Murine bone marrow-derived myofibroblasts (BMFs) have previously been shown to promote gastric cancer growth. However, whether BMFs promote gastric cancer cell metastasis remains largely unknown.

Methods

Wound healing assay, Transwell invasion and migration assay and 3D organotypic co-culture systems were conducted to study the effects of BMFs on invasion and migration of gastric cancer cells and the invasion and migration ability of gastric cancer stem cell-like cells (CSC-LCs) induced by BMFs. We employed two animal model to study the role of BMFs on the in vivo metastasis of gastric cancer cells and the metastatic ability of gastric BMF-induced CSC-LCs. A human gastric cancer tissue microarray and TCGA gastric cancer database were analysed to study the relationship between the expression of IL-6 and TGF-β1 and clinicopathological characteristics and survival in gastric cancer.

Results

We found that BMFs promoted the in vitro migration and invasion of gastric cancer cells. BMFs promoted liver, lung, subcutaneous, and splenic metastases of MKN28 cells in the spleen injection liver metastasis model and co-injection of caudal vein (IOCV) mouse model. BMFs reprogrammed non-gastric cancer stem cell (CSC) to CSC-LCs and enhanced CSC-LC migration and metastasis. BMF-derived IL-6 and gastric cancer cell-secreted TGF-β1 mediated the interaction between BMFs and gastric cancer cells, promoting tumour metastasis. BMFs enhanced the expressions of STAT3 and p-STAT3 in co-cultured gastric cancer cells. A combination of Napabucasin and Galunisertib exhibited the strongest inhibition of cell migration compared to when administered alone. Gastric cancer tissue array and TCGA database indicated that the overexpression of IL-6 and TGF-β1 was associated with gastric cancer metastasis.

Conclusion

Our results demonstrated that BMFs promote gastric cancer metastasis through the activation of the TGF-β1 and IL-6/STAT3 signalling pathways. Targeting the inhibition of these interactions may be a potent therapeutic strategy for addressing gastric cancer metastasis.

Bone marrow-derived myofibroblasts promote colon tumorigenesis through the IL-6/JAK2/STAT3 pathway

Bone marrow-derived myofibroblasts (BMFs) have been shown to promote tumor growth. Here, we found that BMFs or BMF conditioned medium (BMF-CM) induced cancer stem cell-like sphere formation of colon cancer cells. The co-cultured BMFs, but not co-cultured cancer cells, expressed higher levels of IL-6 than BMFs or cancer cells cultured alone. Anti-mouse IL-6 neutralizing antibody, JAK2 inhibitors and STAT3 knockdown in mouse cancer cells reduced BMF- and BMF-CM-induced sphere formation of colon cancer cells. When co-injected, BMFs significantly enhanced tumorigenesis of colon cancer cells in mice. Our results demonstrate that BMFs promote tumorigenesis via the activation of the IL-6/JAK2/STAT3 pathway.