Regulation of RIP3 by the transcription factor Sp1 and the epigenetic regulator UHRF1 modulates cancer cell necroptosis

Abstract

Receptor-interacting kinase-3 (RIP3) is a key regulator of necroptosis. It has been shown that the expression of RIP3 is silenced in most cancer cells and tissues due to genomic methylation. However, the regulatory mechanisms controlling RIP3 expression in cancer cells have not been fully elucidated. Here, we report that Sp1, a well-characterized zinc-finger transcription factor, directly regulates RIP3 expression in cancer cells. Knockdown of endogenous Sp1 significantly decreases the transcription of Rip3, thereby further inhibiting necroptosis. The re-expression of Sp1 restores the necroptotic response. In addition, knockdown of epigenetic regulator UHRF1 (ubiquitin-like, containing PHD and RING finger domains 1) in RIP3-null cancer cells reduces the methylation level of the Rip3 promoter. This effect is sufficient to trigger the expression of RIP3 in RIP3-null cancer cells. The induced expression of RIP3 by UHRF1 RNAi depends on the presence of Sp1. Remarkably, the ectopic expression of RIP3 in RIP3-null cancer cells results in a decrease in tumor growth in mice. Therefore, our findings offer insights into RIP3 expression control in cancer cells and suggest an inhibitory effect of RIP3 on tumorigenesis.

Loss of Caspase-8 function in combination with SMAC mimetic treatment sensitizes Head and Neck Squamous Carcinoma to radiation through induction of necroptosis

“…In that study, the cancer cell lines that showed lack of RIP3 expression were found to be resistant to the combination of TNFα, Z-VAD-FMK and the SMAC mimetic SM-164. Similarly, in another study where 8 colon cancer cell lines were tested for sensitivity to a TNFα, SMAC mimetic and Z-VAD-FMK combination, only those that were devoid of RIP3 at the mRNA and protein levels failed to undergo necroptosis (50). Consistent with these results, our data suggest that RIP3 loss can be an underlying mechanism by which HNSCCs become resistant to necroptotic death stimulated with Birinapant and Z-VAD-FMK (Fig 4A-G).…”

Receptor‐Interacting Protein Kinase 3 (RIPK3) inhibits autophagic flux during necroptosis in intestinal epithelial cells

“…Next, the intestinal epithelial cell line HCT116, which lacks RIPK3 expression , was used to clarify the role of RIPK3 in the increased LC3 puncta observed following TNF‐α plus Z‐VAD treatment. To confirm RIPK3 dependency of this phenomenon, Myc‐RIPK3 was introduced into HCT116 cells and the LC3 puncta in Myc‐expressing cells were analyzed (Fig.…”

RIPK3-Induced Inflammation by I-MDSCs Promotes Intestinal Tumors

“…However, tumors continue to grow and increase in numbers. Ectopic RIPK3 expression in a lung cancer cell line induced cell death to reduce tumor growth in a xenograft model (41). In contrast, RIPK3 deletion in breast and colon cancer cell lines reduced tumor growth in xenograft models (30).…”