Repurposing Synthetic Congeners of a Natural Product Aurone Unveils a Lead Antitumor Agent Inhibiting Folded P-Loop Conformation of MET Receptor Tyrosine Kinase

Abstract

A library of 24 congeners of the natural product sulfuretin were evaluated against nine panels representing nine cancer diseases. While sulfuretin elicited very weak activities at 10 µM concentration, congener 1t was identified as a potential compound triggering growth inhibition of diverse cell lines. Mechanistic studies in HCT116 colon cancer cells revealed that congener 1t dose-dependently increased levels of cleaved-caspases 8 and 9 and cleaved-PARP, while it concentration-dependently decreased levels of CDK4, CDK6, Cdc25A, and Cyclin D and E resulting in induction of cell cycle arrest and apoptosis in colon cancer HCT116 cells. Mechanistic study also presented MET receptor tyrosine kinase as the molecular target mediating the anticancer activity of compound 1t in HCT116 cells. In silico study predicted folded p-loop conformation as the form of MET receptor tyrosine kinase responsible for binding of compound 1t. Together, the current study presents compound 1t as an interesting anticancer lead for further development.

Keywords: MET kinase; antitumor agents; apoptosis; aurone; cell cycle arrest; colon cancer; natural products congeners; sulfuretin.

Figure 1

Design of sulfuretin’s congeners focused library for profiling anticancer activities.

Figure 2

% growth inhibition of diverse blood cancer cell lines triggered by 10 µM concentrations of sulfuretin and its congeners (1a–1x).

Figure 3

% growth inhibition of diverse non-small-cell lung cancer cell lines triggered by 10 µM concentrations of sulfuretin and its congeners (1a–1x).

Figure 4

% growth inhibition of growth of diverse colorectal cancer cell lines triggered by 10 µM concentrations of sulfuretin and its congeners (1a–1x).

Figure 5

% growth inhibition of growth of diverse CNS cancer cell lines triggered by 10 µM concentrations of sulfuretin and its congeners (1a–1x).

Figure 6

% growth inhibition of growth of diverse melanoma cancer cell lines triggered by 10 µM concentrations of sulfuretin and its congeners (1a–1x).

Figure 7

% growth inhibition of growth of ovarian cancer cell lines triggered by 10 µM concentrations of sulfuretin and its congeners (1a–1x).

Figure 8

% growth inhibition of growth of diverse renal cancer cell lines triggered by 10 µM concentrations of sulfuretin and its congeners (1a–1x).

Figure 9

% growth inhibition of growth of prostate cancer cell lines triggered by 10 µM concentrations of sulfuretin and its congeners (1a–1x).

Figure 10

% Growth inhibition of growth of diverse breast cancer cell lines triggered by 10 µM concentrations of sulfuretin and its congeners (1a–1x).

Figure 11

Apoptotic effects of compound 1t in HCT116 cells. (A) Flow cytometry after staining with annexin V-FITC/PI; (B) PARP, cleaved PARP, caspase 8, cleaved caspase 8, caspase 9, and cleaved caspase 9 protein expressions in compound 1t-treated HCT116 cells.

Figure 12

Impact of compound 1t on the cell cycle distribution in HCT116 cells. (A) HCT116 cell cycle distributions after treatment with different concentrations of compound 1t. The graphs show the quantified results. (B) CDK4, CDK6, Cyclin D, Cyclin E, and Cdc25A protein expressions after treatment with different concentrations of compound 1t.

Figure 13

Impact of compound 1t on MET/PI3K/AKT/mTOR pathway in HCT116 cells.

Figure 14

Molecular docking predicted binding modes of compound 1t with different conformation of MET receptor tyrosine kinase: (A) Predicted binding mode with folded p-loop conformation (PDB: 7b41; co-crystallized ligand is pink-colored). (B) Predicted binding mode with extended p-loop conformation (PDB: 7b3w; co-crystallized ligand is pink-colored). (C) Predicted binding mode with rearranged αC helix conformation (PDB: 8an8; co-crystallized ligand is pink-colored).