# Triptolide Triggers Protective Autophagy via ROS Induction in NSCLC: Therapeutic Synergy with Autophagy Inhibition

## TL;DR

Triptolide kills lung cancer cells by causing stress, but the cells try to survive by recycling; blocking this recycling makes triptolide more effective.

## Contribution

This study reveals that triptolide-induced ROS activates protective autophagy in NSCLC and that inhibiting autophagy enhances its anticancer effects.

## Key findings

- Triptolide increases ROS levels, leading to NSCLC cell death.
- ROS accumulation activates protective autophagy in NSCLC cells.
- Combining triptolide with chloroquine significantly suppresses tumor growth in mice.

## Abstract

Non-small cell lung cancer (NSCLC) remains difficult to treat because tumor cells can adapt to therapy and survive. Triptolide, a natural compound from Tripterygium wilfordii, has shown anticancer activity, but its mechanisms in NSCLC are not fully understood. In this study, we found that triptolide increases oxidative stress inside NSCLC cells, which contributes to tumor cell death. At the same time, the cells activate autophagy, a self-protective recycling process that helps them tolerate stress. Importantly, blocking autophagy with chloroquine strengthened the anticancer effect of triptolide in a mouse tumor model. These findings suggest that combining triptolide with autophagy inhibition may be a promising strategy to improve treatment efficacy in NSCLC.

Background: Triptolide (TPL) is an epoxytriptolide diterpenoid lactone isolated from the traditional Chinese medicinal herb Tripterygium wilfordii and exhibits broad pharmacological activities, including anti-inflammatory, immunomodulatory, and antitumor effects. Its water-soluble prodrug, minnelide, is currently undergoing clinical trials for the treatment of pancreatic cancer. Reactive oxygen species (ROS) regulate cellular fate by inducing oxidative damage and activating autophagy, which can promote cell survival under moderate stress but contribute to cell death when excessively or persistently activated. Although TPL has been reported to induce ROS accumulation, its mechanistic role in non-small cell lung cancer (NSCLC) remains incompletely understood. This study aimed to systematically investigate the role of ROS-mediated autophagy in TPL-induced cytotoxicity and to evaluate the therapeutic potential of combining TPL with autophagy inhibition in NSCLC. Methods: A series of in vitro experiments was performed to characterize TPL-mediated changes in NSCLC cell proliferation, migration, and ROS production. Autophagy- and apoptosis-related molecular alterations were analyzed using Western blotting and fluorescence microscopy with fluorescent reporter constructs. An H1299 xenograft mouse model was established to assess the antitumor efficacy of TPL in vivo and its combination effects with an autophagy inhibitor. Results: In this study, we demonstrated that TPL induces NSCLC cell death primarily through increased ROS levels. Mechanistic analyses further revealed that ROS accumulation simultaneously activates a protective autophagic response. Notably, in vivo experiments showed that co-administration of TPL with the autophagy inhibitor chloroquine resulted in significantly stronger tumor growth suppression than either treatment alone. Conclusions: Autophagy acts as a resistance mechanism against TPL-induced cytotoxicity in NSCLC, and pharmacological autophagy inhibition potentiates the antitumor activity of TPL. These findings clarify the ROS–autophagy interplay underlying TPL-mediated cell death and provide a preclinical rationale for combining TPL with autophagy inhibitors as a therapeutic strategy for NSCLC.