Structural and functional insights into targeting hTERT G-quadruplex by levo-Tetrahydropalmatine in the non-small cell lung cancer.

The G-quadruplex structure in the human telomerase reverse transcriptase (hTERT) promoter has recently emerged as a promising therapeutic target in cancer. However, the development and application are strongly restricted by the lack of selective ligands. Herein, levo-tetrahydropalmatine (l-THP) and its two metabolic derivatives (M1 and M2) were identified as novel ligands of the hTERT G-quadruplex using a combination of fluorescence spectroscopy, UV-visible absorption, circular dichroism (CD), CD-melting assays, electrophoretic mobility shift assays (EMSA), molecular docking, as well as cellular and in vivo models. Our results demonstrate that l-THP, M1, and M2 exhibit potential binding affinity and selectivity toward the hTERT G-quadruplex. Fluorescence mutation assays revealed that these compounds preferentially interact with the junction between the first and second G-tracts (5'-3'), particularly recognizing the cytosine at position 21. Moreover, these ligands significantly suppressed the hTERT mRNA expression (1.00 for control, 0.43 ± 0.02 for l-THP, 0.19 ± 0.01 for M1, 0.33 ± 0.03 for M2) and showed the potent antitumor activity in A549 cells and lung cancer xenograft model. Collectively, these findings establish l-THP and its derivatives as the promising lead compounds for the development of chemotherapeutics against non-small cell lung cancer as well as provide the plausible mechanism insights into potent antitumor activity.