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Updated: Feb 2, 2026
Induction of Mesenchymal-Epithelial Transitions in Sarcoma Cells
Published on: April 7, 2017
The Tumor Suppressor SASH1 Interacts With the Signal Adaptor CRKL to Inhibit Epithelial-Mesenchymal Transition and
Fabian Christoph Franke1, Johannes Müller1, Miguel Abal2
1Department of Surgery, Technical University of Munich, School of Medicine, Klinikum Rechts der Isar, Munich, Germany.
Background & Aims:
The tumor-suppressor sterile α motif- and Src-homology 3-domain containing 1 (SASH1) has clinical relevance in colorectal carcinoma and is associated specifically with metachronous metastasis. We sought to identify the molecular mechanisms linking decreased SASH1 expression with distant metastasis formation.
Methods:
SASH1-deficient, SASH1-depleted, or SASH1-overexpressing HCT116 colon cancer cells were generated by the Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated 9-method, RNA interference, and transient plasmid transfection, respectively. Epithelial-mesenchymal transition (EMT) was analyzed by quantitative reverse-transcription polymerase chain reaction, immunoblotting, immunofluorescence microscopy, migration/invasion assays, and 3-dimensional cell culture. Yeast 2-hybrid assays and co-immunoprecipitation/mass-spectrometry showed V-Crk avian sarcoma virus CT10 oncogene homolog-like (CRKL) as a novel interaction partner of SASH1, further confirmed by domain mapping, site-directed mutagenesis, co-immunoprecipitation, and dynamic mass redistribution assays. CRKL-deficient cells were generated in parental or SASH1-deficient cells. Metastatic capacity was analyzed with an orthotopic mouse model. Expression and significance of SASH1 and CRKL for survival and response to chemotherapy was assessed in patient samples from our department and The Cancer Genome Atlas data set.
Results:
SASH1 expression is down-regulated during cytokine-induced EMT in cell lines from colorectal, pancreatic, or hepatocellular cancer, mediated by the putative SASH1 promoter. Deficiency or knock-down of SASH1 induces EMT, leading to an aggressive, invasive phenotype with increased chemoresistance. SASH1 counteracts EMT through interaction with the oncoprotein CRKL, inhibiting CRKL-mediated activation of SRC kinase, which is crucially required for EMT. SASH1-deficient cells form significantly more metastases in vivo, depending entirely on CRKL. Patient tumor samples show significantly decreased SASH1 and increased CRKL expression, associated with significantly decreased overall survival. Patients with increased CRKL expression show significantly worse response to adjuvant chemotherapy.
Conclusions:
We propose SASH1 as an inhibitor of CRKL-mediated SRC signaling, introducing a potentially druggable mechanism counteracting chemoresistance and metastasis formation.
Insights
Decreased sterile alpha motif- and Src-homology 3-domain containing 1 (SASH1) expression promotes colorectal cancer metastasis by enabling epithelial-mesenchymal transition (EMT). SASH1 inhibits this process by interacting with CRKL and blocking SRC signaling.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Metastasis
Background:
- The tumor suppressor sterile alpha motif- and Src-homology 3-domain containing 1 (SASH1) is clinically relevant in colorectal carcinoma.
- SASH1 expression is linked to metachronous metastasis in colorectal cancer patients.
Purpose of the Study:
- To elucidate the molecular mechanisms by which reduced SASH1 expression contributes to distant metastasis.
- To identify novel therapeutic targets for preventing colorectal cancer progression and chemoresistance.
Main Methods:
- Generated SASH1-deficient/depleted/overexpressing colon cancer cells using CRISPR-Cas9 and RNA interference.
- Analyzed epithelial-mesenchymal transition (EMT) markers and cellular functions via molecular and cell-based assays.
- Identified V-Crk avian sarcoma virus CT10 oncogene homolog-like (CRKL) as a SASH1 interaction partner using yeast two-hybrid and co-immunoprecipitation/mass spectrometry.
- Assessed metastatic capacity in an orthotopic mouse model and analyzed SASH1/CRKL expression in patient samples.
Main Results:
- Down-regulation of SASH1 during cytokine-induced EMT promotes an aggressive, invasive phenotype with increased chemoresistance.
- SASH1 inhibits EMT by interacting with the oncoprotein CRKL, thereby blocking CRKL-mediated SRC kinase activation.
- SASH1-deficient cells exhibit significantly increased metastatic potential in vivo, dependent on CRKL.
- Decreased SASH1 and increased CRKL expression in patient tumors correlate with reduced overall survival and poor response to chemotherapy.
Conclusions:
- SASH1 acts as an inhibitor of CRKL-mediated SRC signaling, offering a potential druggable target.
- Targeting the SASH1-CRKL-SRC axis may provide a strategy to counteract chemoresistance and metastasis in colorectal cancer.
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