Synthesis, antiproliferative activity, and biological profiling of C-19 trityl and silyl ether andrographolide analogs in colon cancer and breast cancer cells

Andrographolide, a natural product, putatively functions through covalent inhibition of NF-κB, a transcription factor that modulates tumor survival and metastasis. Previous studies found that functionalization of the C-19 hydroxyl alters the primary mode of action from inhibition of NF-κB to the modulation of the Wnt1/β-catenin signaling pathway. Here, we synthesized a series of C-19 trityl and silyl ether analogs. MTT assays reveal cell line selectivity between colorectal and breast cancer cells, which is consistent with known mechanisms of β-catenin-driven cell proliferation in colorectal cancer cell lines. Through a TNF-α dependent NF-κB reporter assay, we observed that our analogs generally exhibit greater activity than andrographolide. Fluorescence imaging demonstrated that cells treated with andrographolide and its C-19 analogs retained similar distributions of active β-catenin, but notable differences in antiproliferative potency upon co-delivery with GSK-3β inhibitor CHIR99021 suggest several analogs have a greater dependence on β-catenin signaling for antiproliferative activity in HT-29 cells.