PDF file - 1004K, S1. The Twist box domain is required for full Twist1 transcriptional activity. S2. Quantification of immunofluorescence from isogenic prostate cancer cell lines stably expressing Twist1 and Twist1-F191G. S3. The Twist box domain is required for full Twist1-induced EMT marker phenotypes of prostate cancer cells. S4. Twist1 overexpression induces temporal changes in the material properties of prostate cancer cells during their migration in a wound healing assay. S5. The overexpression of Twist1 or Twist1-F191G does not increase cellular proliferation of prostate cancer cells in vitro. S6. The Twist box domain is required for full Twist1-induced cellular migration in PC3 cells. S7. Twist1 overexpression increases cell traction forces of individual androgenindependent PC3 prostate cancer cells. S8. Twist1 overexpression confers radioresistance to prostate cancer cells which is attenuated by mutation of the Twist box domain. S9. The Twist box domain is required for Twist1-induced soft agar anchorageindependent growth of 22Rv1 prostate cancer cells. S10. Twist1 overexpression does not confer prostate cancer cells increased primary tumorigenicity and slows primary tumor cell growth in vivo. S11. The Twist box domain is required for full Twist1-induced expression of Hoxa9/HOXA9.
ARTICLE ABSTRACT
Twist1, a basic helix-loop-helix transcription factor, plays a key role during development and is a master regulator of the epithelial–mesenchymal transition (EMT) that promotes cancer metastasis. Structure–function relationships of Twist1 to cancer-related phenotypes are underappreciated, so we studied the requirement of the conserved Twist box domain for metastatic phenotypes in prostate cancer. Evidence suggests that Twist1 is overexpressed in clinical specimens and correlated with aggressive/metastatic disease. Therefore, we examined a transactivation mutant, Twist1-F191G, in prostate cancer cells using in vitro assays, which mimic various stages of metastasis. Twist1 overexpression led to elevated cytoskeletal stiffness and cell traction forces at the migratory edge of cells based on biophysical single-cell measurements. Twist1 conferred additional cellular properties associated with cancer cell metastasis including increased migration, invasion, anoikis resistance, and anchorage-independent growth. The Twist box mutant was defective for these Twist1 phenotypes in vitro. Importantly, we observed a high frequency of Twist1-induced metastatic lung tumors and extrathoracic metastases in vivo using the experimental lung metastasis assay. The Twist box was required for prostate cancer cells to colonize metastatic lung lesions and extrathoracic metastases. Comparative genomic profiling revealed transcriptional programs directed by the Twist box that were associated with cancer progression, such as Hoxa9. Mechanistically, Twist1 bound to the Hoxa9 promoter and positively regulated Hoxa9 expression in prostate cancer cells. Finally, Hoxa9 was important for Twist1-induced cellular phenotypes associated with metastasis. These data suggest that the Twist box domain is required for Twist1 transcriptional programs and prostate cancer metastasis.Implications: Targeting the Twist box domain of Twist1 may effectively limit prostate cancer metastatic potential. Mol Cancer Res; 11(11); 1387–400. ©2013 AACR.
