RIPK1/RIPK3 promotes vascular permeability to allow tumor cell extravasation independent of its necroptotic function

Abstract

Necroptosis is an inflammatory form of programmed cell death requiring receptor-interacting protein kinase 1, 3 (RIPK1, RIPK3) and mixed lineage kinase domain-like protein (MLKL). The kinase of RIPK3 phosphorylates MLKL causing MLKL to form a pore-like structure, allowing intracellular contents to release and cell death to occur. Alternatively, RIPK1 and RIPK3 have been shown to regulate cytokine production directly influencing inflammatory immune infiltrates. Recent data suggest that necroptosis may contribute to the malignant transformation of tumor cells in vivo and we asked whether necroptosis may have a role in the tumor microenvironment altering the ability of the tumor to grow or metastasize. To determine if necroptosis in the tumor microenvironment could promote inflammation alone or by initiating necroptosis and thereby influencing growth or metastasis of tumors, we utilized a syngeneic tumor model of metastasis. Loss of RIPK3 in the tumor microenvironment reduced the number of tumor nodules in the lung by 46%. Loss of the kinase activity in RIPK1, a member of the necrosome also reduced tumor nodules in the lung by 38%. However, the loss of kinase activity in RIPK3 or the loss of MLKL only marginally altered the ability of tumor cells to form in the lung. Using bone marrow chimeras, the decrease in tumor nodules in the Ripk3−/− appeared to be due to the stromal compartment rather than the hematopoietic compartment. Transmigration assays showed decreased ability of tumor cells to transmigrate through the vascular endothelial layer, which correlated with decreased permeability in the Ripk3−/− mice after tumor injection. In response to permeability factors, such as vascular endothelial growth factor, RIPK3 null endothelial cells showed decreased p38/HSP27 activation. Taken together, our results suggest an alternative function for RIPK1/RIPK3 in vascular permeability leading to decreased number of metastasis.

Signalling networks in cholangiocarcinoma: Molecular pathogenesis, targeted therapies and drug resistance

“…72 Furthermore, RIP3-dependent signalling promotes vascular permeability by both triggering necroptosis in vascular endothelial cells 73 and activating p38/heat shock protein 27. 74…”

Necroptotic cell death in anti‐cancer therapy

“…Other mechanisms of tumor metastasis in which RIPK1 and RIPK3 signaling may play an important role have been proposed. Hanggi et al . have shown that although the loss of the kinase activities of RIPK1 and RIPK3 are important in the ability of tumor cells to form lung nodules, cell death in the endothelial cell layer was not dependent on RIPK3.…”

“…99 Other mechanisms of tumor metastasis in which RIPK1 and RIPK3 signaling may play an important role have been proposed. Hanggi et al 100 have shown that although the loss of the kinase activities of RIPK1 and RIPK3 are important in the ability of tumor cells to form lung nodules, cell death in the endothelial cell layer was not dependent on RIPK3. The authors showed that p38/HSP27 activation of RIPK3-null endothelial cells is decreased in response to permeability factors, such as vascular endothelial growth factor, due to decreased vessel permeability.…”

RIPK1 and RIPK3 - emerging targets in cancer?

“…Using genetic and pharmacologic tools, the authors established that this mechanism plays a major role in B16 melanoma extravasation and metastasis in vivo. Hanngi et al (110) reported that RIPK1 kinase activity and RIPK3 (primarily as a scaffold) were required for activation of p38/Hsp27 by vascular permeability factors, such as VEGF-A, providing an alternative explanation for the role of these factors in melanoma extravasation.…”