ABSTRACT
Oncogene activation through DNA amplification or overexpression is a crucial driver of cancer initiation and progression. The FOXK2 gene, located on chromosome 17q25, encodes a transcription factor with a forkhead DNA-binding domain. Analysis of genomic datasets reveals that FOXK2 is frequently amplified and overexpressed in breast cancer, correlating with poor patient survival. Knockdown of FOXK2 significantly inhibited breast cancer cell proliferation, migration, anchorage-independent growth, and delayed tumor growth in a xenograft mouse model. Additionally, inhibiting FOXK2 sensitized breast cancer cells to chemotherapy. Co-overexpression of FOXK2 and mutant PI3KCA transformed non-tumorigenic MCF-10A cells, suggesting a role for FOXK2 in PI3KCA-driven tumorigenesis. CCNE2, PDK1, and ESR1 were identified as transcriptional targets of FOXK2 in MCF-7 cells. Small-molecule inhibitors of CCNE2/CDK2 (dinaciclib) and PDK1 (dichloroacetate) exhibited synergistic anti-tumor effects with PI3KCA inhibitor (alpelisib) in vitro. Inhibition of FOXK2 by dinaciclib synergistically enhanced the anti-tumor effects of alpelisib in a xenograft mouse model. Collectively, these findings highlight the oncogenic function of FOXK2 and suggest that FOXK2 and its downstream genes represent potential therapeutic targets in breast cancer.
Subject(s)
Breast Neoplasms , Cell Proliferation , Drug Resistance, Neoplasm , Forkhead Transcription Factors , Animals , Female , Humans , Mice , 3-Phosphoinositide-Dependent Protein Kinases/metabolism , 3-Phosphoinositide-Dependent Protein Kinases/genetics , Antineoplastic Agents/pharmacology , Breast Neoplasms/genetics , Breast Neoplasms/pathology , Breast Neoplasms/drug therapy , Breast Neoplasms/metabolism , Cell Movement/drug effects , Cell Proliferation/drug effects , Cyclin-Dependent Kinase 2/genetics , Cyclin-Dependent Kinase 2/metabolism , Drug Resistance, Neoplasm/genetics , Estrogen Receptor alpha/genetics , Estrogen Receptor alpha/metabolism , Forkhead Transcription Factors/genetics , Forkhead Transcription Factors/metabolism , Gene Amplification , Gene Expression Regulation, Neoplastic/drug effects , MCF-7 Cells , Mice, Nude , Pyruvate Dehydrogenase Acetyl-Transferring Kinase/genetics , Pyruvate Dehydrogenase Acetyl-Transferring Kinase/metabolism , Thiazoles/pharmacology , Xenograft Model Antitumor AssaysABSTRACT
SMARCB1 loss has long been observed in many solid tumors. However, there is a need to elucidate targetable pathways driving growth and metastasis in SMARCB1-deficient tumors. Here, we demonstrate that SMARCB1 deficiency, defined as genomic SMARCB1 copy number loss associated with reduced mRNA, drives disease progression in patients with bladder cancer by engaging STAT3. SMARCB1 loss increases the chromatin accessibility of the STAT3 locus in vitro. Orthotopically implanted SMARCB1 knockout (KO) cell lines exhibit increased tumor growth and metastasis. SMARCB1-deficient tumors show an increased IL6/JAK/STAT3 signaling axis in in vivo models and patients. Furthermore, a pSTAT3 selective inhibitor, TTI-101, reduces tumor growth in SMARCB1 KO orthotopic cell line-derived xenografts and a SMARCB1-deficient patient derived xenograft model. We have identified a gene signature generated from SMARCB1 KO tumors that predicts SMARCB1 deficiency in patients. Overall, these findings support the clinical evaluation of STAT3 inhibitors for the treatment of SMARCB1-deficient bladder cancer.
Subject(s)
Interleukin-6 , Urinary Bladder Neoplasms , Humans , Interleukin-6/genetics , Interleukin-6/metabolism , Signal Transduction/genetics , SMARCB1 Protein/genetics , SMARCB1 Protein/metabolism , Urinary Bladder Neoplasms/genetics , Cell Line, Tumor , STAT3 Transcription Factor/genetics , STAT3 Transcription Factor/metabolismABSTRACT
ZNRF3 and RNF43 are closely related transmembrane E3 ubiquitin ligases with significant roles in development and cancer. Conventionally, their biological functions have been associated with regulating WNT signaling receptor ubiquitination and degradation. However, our proteogenomic studies have revealed EGFR as the most negatively correlated protein with ZNRF3/RNF43 mRNA levels in multiple human cancers. Through biochemical investigations, we demonstrate that ZNRF3/RNF43 interact with EGFR via their extracellular domains, leading to EGFR ubiquitination and subsequent degradation facilitated by the E3 ligase RING domain. Overexpression of ZNRF3 reduces EGFR levels and suppresses cancer cell growth in vitro and in vivo, whereas knockout of ZNRF3/RNF43 stimulates cell growth and tumorigenesis through upregulated EGFR signaling. Together, these data highlight ZNRF3 and RNF43 as novel E3 ubiquitin ligases of EGFR and establish the inactivation of ZNRF3/RNF43 as a driver of increased EGFR signaling, ultimately promoting cancer progression. This discovery establishes a connection between two fundamental signaling pathways, EGFR and WNT, at the level of cytoplasmic membrane receptor, uncovering a novel mechanism underlying the frequent co-activation of EGFR and WNT signaling in development and cancer.