The Secretion of miR-200s by a PKCζ/ADAR2 Signaling Axis Promotes Liver Metastasis in Colorectal Cancer

Abstract

SUMMARY Most colorectal cancer (CRC)-related deaths are due to liver metastases. PKCζ is a tumor suppressor in CRC with reduced expression in metastasis. Given the importance of microRNAs (miRNAs) in regulating cellular plasticity, we performed an unbiased screening and identified the miR-200 family as the most relevant miRNAs downregulated by PKCζ deficiency. The regulation of the intracellular levels of miR-200 by PKCζ is post-transcriptional and involves their secretion in extracellular vesicles. Here, we identified ADAR2 as a direct substrate of PKCζ in CRC cells. Phosphorylation of ADAR2 regulates its editing activity, which is required to maintain miR-200 steady-state levels, suggesting that the PKCζ/ADAR2 axis regulates miR-200 secretion through RNA editing. Loss of this axis results in epithelial-to-mesenchymal transition (EMT) and increased liver metastases, which can be inhibited in vivo by blocking miR-200 release. Therefore, the PKCζ/ADAR2 axis is a critical regulator of CRC metastases through modulation of miR-200 levels.

Differential RNA editing between epithelial and mesenchymal tumors impacts mRNA abundance in immune response pathways

“…These findings suggest that loss of either catalytically active ADAR enabled EMT in the two cell lines. The phenotypic changes following ADAR2 KD are consistent with a previous report that ADAR2-deficiency can induce EMT in SW480 cells 29 . Together, these results indicate that knockdown of ADARs, which impairs RNA editing at genome scale, promotes EMT.…”

“…Our cell line experiments showed EMT induction upon KD of either ADAR1 or ADAR2. Loss of ADAR2 was also previously reported to trigger EMT by mediating the extracellular shuttling of EMT-repressing miR-200s 29 . Given these findings for both enzymatic ADARs, we might expect to observe hypoediting in the M phenotype (which we observed for BRCA and OV).…”

“…EMT is known to be accompanied by substantial transcriptome remodeling 17,[24][25][26][27][28] . Given the previously reported functional relevance of RNA editing in EMT 19,23,29 , we hypothesized that epithelial and mesenchymal tumors possess different transcriptomewide RNA editing profiles. Thus, we analyzed RNA-seq datasets of primary tumors from The Cancer Genome Atlas (TCGA).…”

Development of miRNA‐based therapeutic approaches for cancer patients

“…In colon cancer, EMT and liver metastasis are induced by exosomal secretion of the miR‐200 family, which suppresses the EMT phenotype described above . Shelton et al reported that the intracellular levels of miR‐200 family members are post‐transcriptionally regulated by PKCζ which is reported to act as a tumor suppressor . PKCζ and its substrate ADAR2 play important roles in the accumulation of intracellular miR‐200 family members in cancer cells.…”

cPLA2α reversibly regulates different subsets of cancer stem cells transformation in cervical cancer

“…PKCζ, an atypical protein kinase C, is a key component of PI3k/Akt signaling that can direct cell fate decisions to govern cancer cell state changes (a stem cell‐like state vs a differentiation state) . A very recent study demonstrated that PKCζ is a critical regulator of colorectal cancer cell EMT and metastasis through modulating miR‐200 . Moreover, combined inactivation of PKCζ and COX‐2 induced MET in melanoma cells, which in turn inhibited migration and invasion .…”