β-catenin/TCF: Small Molecule Peptidomimetic Inhibitors of the Interaction of β-catenin and T-cell Factor
Aberrant Wnt pathway signaling is thought to be important for the growth of triple negative breast cancer (TNBC) stem cells. The formation of the β-catenin/T-cell factor (Tcf) complex is a crucial step in Wnt signaling, and is the major driving force for the initiation, progression, and metastasis of TNBC. Peptidomimetics were developed that can selectively disrupt the β-catenin/Tcf protein-protein interaction (PPI). Compounds 53 and 57 had a Ki of 0.64 ± 0.12 and 0.44 ± 0.098 μM, respectively, and exhibit good selectivity for β-catenin/Tcf over β-catenin/E-cadherin and β-catenin/APC PPIs. Cell-based studies indicated that 56, the prodrug of 53, disrupted the β-catenin/Tcf PPI without affecting the β-catenin/E-cadherin and β-catenin/APC PPIs, with an IC50 as low as 7.25 ± 0.72 μM, suppressed transactivation of Wnt/β-catenin signaling in a dose-dependent manner, and selectively inhibited viability, migration, and invasiveness of Wnt/β-catenin dependent cancer cells.
- There are expected to be about 266,000 new cases of breast cancer in 2018. Breast cancer is the leading cause of cancer death in females worldwide. Triple negative breast cancer (estrogen receptor, progesterone receptor and epidermal growth factor receptor 2-negative breast cancer) is found in about 10–20% of breast cancer patients. TNBC represents an important clinical challenge because it is highly metastatic, less responsive to standard treatment, and associated with a high rate of cancer recurrence.
- Currently, no targeted treatment option is available for TNBC. TNBC cells are heterogeneous and have a subpopulation of cancer stem cells that drive tumor growth, seed metastases, and induce cancer recurrence. These cancer stem cells are resistant to current treatments, but must be eradicated to achieve a durable remission. Canonical Wnt signaling is aberrantly over-activated in TNBC cancer stem cells, which maintains cancer stem cell self-renewal and resistance to current therapies. There is also some recent evidence to suggest that activation of the Wnt/ β-catenin pathway may help cancer cells avoid a T-cell based anti-tumor immune response.
Based on compound 1, which was designed to target the Tcf4 G13ANDE17 binding site of β-catenin, extensive structure-activity relationship (SAR) studies were conducted. As a result, compounds 53 and 57 were found to disrupt the β-catenin/Tcf PPI with the Ki of 0.64 ± 0.12 and 0.44 ± 0.098 μM, respectively. MTS tetrazolium cell viability assays were performed to evaluate the effect of β-catenin/Tcf inhibitors on growth of different cancer cell lines with hyperactive Wnt signaling, including TNBC cells MDAMB-231 and MDA-MB-468. The IC50s of 56 are 12.3 ± 2.16 μM for TNBC MDA-MB-231 cells and 7.25 ± 0.72 μM for TNBC MDA-MB-468 cells. Using the FP selectivity assay, the selectivities of 53 for β-catenin/Tcf4 over β-catenin/E-cadherin interactions and β-catenin/APC-R3 interactions are 50- and 137-fold, respectively. Scratch wound healing and Matrigel invasion assays using TNBC MDA-MB-231 cells were conducted, and compound 56 can effectively inhibit TNBC cell migration and invasion at 10 μM. The effects are comparable to that of the β-catenin/CBP inhibitor ICG-001 at 5 μM.
Provisional patent application filed on March 29, 2018 for Dr. Mark Ji.
Haskell Adler PhD MBA CLP
Senior Licensing Manager
Registered Patent Agent