# Targeting CDK4/6 in Cancer: Molecular Docking and Cytotoxic Evaluation of Thottea siliquosa Root Extract

## TL;DR

This study explores a plant extract as a potential natural CDK4/6 inhibitor for cancer treatment, showing promising results in molecular docking and cell tests.

## Contribution

The study identifies Thottea siliquosa root extract as a novel natural source with potential CDK4/6 inhibitory activity for cancer therapy.

## Key findings

- Isocorydine and Thunbergol from the extract showed strong binding affinities to CDK4/6 comparable to standard inhibitors.
- The extract exhibited dose-dependent cytotoxicity with an IC50 of 140 μg/mL and reduced cell migration in HCT116 cells.
- ADME analysis confirmed favorable drug-like properties with minimal toxicity alerts for the identified compounds.

## Abstract

Background: Cyclin-dependent kinases 4 and 6 (CDK4/6) are pivotal regulators of the cell cycle, whose dysregulation is closely linked to cancer progression. While synthetic CDK4/6 inhibitors such as Palbociclib and Ribociclib are clinically effective, their use is limited by significant adverse effects. Methods: In this study, the aqueous root extract of Thottea siliquosa, a traditionally used medicinal plant, was evaluated for its potential as a natural CDK4/6 inhibitor. Phytochemical profiling using GC-MS identified bioactive compounds, which were subsequently subjected to molecular docking, ADME prediction, and in vitro cell-based assays using HCT116 and L929 cells. Results: The docking results revealed that Isocorydine (−7.4 kcal/mol for CDK4 and −7.2 kcal/mol for CDK6) and Thunbergol (−6.5 kcal/mol for CDK4 and −7.0 kcal/mol for CDK6) exhibited promising binding affinities comparable to standard CDK inhibitors, Palbociclib (−7.2, −8.3 kcal/mol) and Ribociclib (−7.1, −8.1 kcal/mol). Among the other tested natural compounds, Squalene (−7.1 kcal/mol for CDK4) and 2-palmitoylglycerol (−5.2 kcal/mol for CDK4, −4.9 kcal/mol for CDK6) demonstrated moderate binding affinities. ADME analysis confirmed favorable drug-like properties with minimal toxicity alerts. The extract displayed dose-dependent cytotoxicity with an IC50 of 140 μg/mL and reduced cell migration in HCT116 cells, indicating potential anti-proliferative effects. These findings suggest that T. siliquosa root extract, through synergistic phytochemical interactions, holds promise as a multi-targeted, plant-based therapeutic candidate for CDK4/6-associated cancers, warranting further in vitro and in vivo validation.