Abstract
The transcriptional coactivator WW domain-binding protein 2 (WBP2) is an emerging oncogene and serves as a node between the signaling protein Wnt and other signaling molecules and pathways, including epidermal growth factor receptor, estrogen receptor/progesterone receptor, and the Hippo pathway. The upstream regulation of WBP2 is well-studied, but its downstream activity remains unclear. Here, we elucidated WBP2's role in triple-negative breast cancer (TNBC), in which Wnt signaling is predominantly activated. Using RNAi coupled with RNA-Seq and MS analyses to identify Wnt/WBP2- and WBP2-dependent targets in MDA-MB-231 TNBC cells, we found that WBP2 is required for the expression of a core set of genes in Wnt signaling. These included AXIN2, which was essential for Wnt/WBP2-mediated breast cancer growth and migration. WBP2 also regulated a much larger set of genes and proteins independently of Wnt, revealing that WBP2 primes cells to Wnt activity by up-regulating G protein pathway suppressor 1 (GPS1) and TRAF2- and NCK-interacting kinase (TNIK). GPS1 activated the c-Jun N-terminal kinase (JNK)/Jun pathway, resulting in a positive feedback loop with TNIK that mediated Wnt-induced AXIN2 expression. WBP2 promoted TNBC growth by integrating JNK with Wnt signaling, and its expression profoundly influenced the sensitivity of TNBC to JNK/TNIK inhibitors. In conclusion, WBP2 links JNK to Wnt signaling in TNBC. GPS1 and TNIK are constituents of a WBP2-initiated cascade that primes responses to Wnt ligands and are also important for TNBC biology. We propose that WBP2 is a potential drug target for JNK/TNIK-based precision medicine for managing TNBC.
Highlights
The transcriptional coactivator WW domain– binding protein 2 (WBP2) is an emerging oncogene and serves as a node between the signaling protein Wnt and other signaling molecules and pathways, including epidermal growth factor receptor, estrogen receptor/progesterone receptor, and the Hippo pathway
Using RNAi coupled with RNA-Seq and MS analyses to identify Wnt/WBP2- and WBP2-dependent targets in MDA-MB-231 triple-negative breast cancer (TNBC) cells, we found that WBP2 is required for the expression of a core set of genes in Wnt signaling
These results indicate that WBP2 is a prognostic factor and its elevated levels in breast cancer may be caused by genomic amplification/gain in addition to the previously described epigenetic mechanism involving protein turnover [21]
Summary
Using RNAi coupled with RNA-Seq and MS analyses to identify Wnt/WBP2- and WBP2-dependent targets in MDA-MB-231 TNBC cells, we found that WBP2 is required for the expression of a core set of genes in Wnt signaling These included AXIN2, which was essential for Wnt/WBP2-mediated breast cancer growth and migration. WBP2 is degraded by itchy E3 ubiquitin protein ligase (ITCH E3 ligase) to prevent aberrant growth but is protected from ITCH and activated by Wnt oncogenic signaling to drive TCF/-catenin– mediated transcription to promote breast cancer [21]. Besides confirming the role of WBP2 as a mediator of Wnt signaling regulating known and novel gene targets including AXIN2, a new function for WBP2 as a primer of cellular response to Wnt ligand was discovered and validated through the elucidation of a signaling axis involving GPS1, JNK/Jun, and TNIK
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