TFF3 Drives Hippo-Dependent EGFR-TKI Resistance in Lung Adenocarcinoma

Academic Background

Lung adenocarcinoma (LUAD) is one of the most common subtypes of non-small cell lung cancer (NSCLC), with frequent mutations in the epidermal growth factor receptor (EGFR). Since 2013, EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib, erlotinib, and osimertinib have been approved for the treatment of NSCLC patients with EGFR mutations. However, 5-25% of patients with EGFR mutations exhibit intrinsic resistance to EGFR-TKIs, and even those initially sensitive to EGFR-TKIs often develop acquired resistance within 8-13 months. Although several resistance mechanisms, such as the EGFR T790M mutation and activation of bypass signaling pathways, have been reported, many remain unclear. Therefore, a deeper understanding of the molecular mechanisms underlying EGFR-TKI resistance is crucial for developing more effective therapeutic strategies.

Trefoil factor 3 (TFF3) is a small secreted protein belonging to the trefoil factor family. TFF3 is upregulated in various cancers and promotes cancer cell survival, proliferation, and migration by activating receptor tyrosine kinases (RTKs) such as EGFR. Additionally, TFF3 has been implicated in resistance to various cancer therapies. This study aims to investigate the role of TFF3 in EGFR-TKI resistance in LUAD and its underlying mechanisms.

Source of the Paper

The study was conducted by S. Zhang et al. and published in Oncogene in 2024, with the DOI: 10.1038/s41388-024-03244-5. The research team is affiliated with multiple institutions, and the full list of authors and their affiliations can be found at the end of the paper.

Research Process and Results

1. Correlation Between TFF3 Expression and Prognosis in LUAD

The study first analyzed the relationship between TFF3 expression and clinicopathological parameters as well as patient survival using a LUAD tissue microarray. The results showed that high TFF3 expression was positively correlated with the degree of lymph node metastasis, and patients with high TFF3 expression had significantly lower overall survival compared to those with low TFF3 expression (p=0.02). This suggests that TFF3 has potential prognostic value in LUAD.

2. TFF3 Mediates EGFR-TKI Resistance via the EGFR Signaling Pathway

To investigate the effect of TFF3 on EGFR-TKI response, the research team forced the expression of TFF3 in PC-9 and HCC827 cell lines. Western blot analysis revealed that forced TFF3 expression increased EGFR activation (as indicated by an increased p-EGFR-Tyr1068/EGFR ratio) and reduced the sensitivity of cells to EGFR-TKIs. Additionally, forced TFF3 expression decreased EGFR-TKI-induced apoptosis and inhibited the effects of EGFR-TKIs on foci formation.

3. TFF3 Inhibition Enhances EGFR-TKI Sensitivity

By knocking down TFF3 using shRNA or inhibiting TFF3 with the small molecule inhibitor AMPC, the research team found that TFF3 inhibition significantly reduced EGFR activation and enhanced the sensitivity of cells to EGFR-TKIs. The combination of AMPC and EGFR-TKIs exhibited synergistic effects both in vitro and in vivo, significantly inhibiting tumor growth and promoting apoptosis.

4. Role of TFF3 in Acquired EGFR-TKI Resistance

The research team established acquired resistant PC-9 and HCC827 cell lines by gradually increasing the concentration of EGFR-TKIs. The results showed that TFF3 expression was significantly increased in the acquired resistant cells, while EGFR activation levels were reduced. Knockdown or inhibition of TFF3 restored the sensitivity of these resistant cells to EGFR-TKIs, indicating that TFF3 plays a key role in acquired EGFR-TKI resistance.

5. Role of the Hippo Signaling Pathway in Acquired EGFR-TKI Resistance

RNA sequencing analysis revealed significant changes in the expression of Hippo signaling pathway-related genes in acquired resistant cells. The expression of YAP, a key effector of the Hippo signaling pathway, was significantly upregulated in resistant cells. TFF3 positively regulated YAP expression through post-transcriptional mechanisms, thereby mediating acquired EGFR-TKI resistance. Inhibition of TFF3 reduced YAP expression and transcriptional activity, restoring the sensitivity of cells to EGFR-TKIs.

Conclusions and Significance

This study reveals a novel mechanism by which TFF3 mediates EGFR-TKI resistance in LUAD. TFF3 mediates intrinsic resistance by enhancing the EGFR signaling pathway and acquired resistance by regulating YAP, a key effector of the Hippo signaling pathway. Inhibition of TFF3 not only enhances the sensitivity to EGFR-TKIs but also restores the response of acquired resistant cells to EGFR-TKIs. These findings provide new therapeutic strategies for overcoming EGFR-TKI resistance and have significant scientific and clinical implications.

Research Highlights

1. Dual Role of TFF3 in LUAD: TFF3 mediates intrinsic resistance through the EGFR signaling pathway and acquired resistance through the Hippo signaling pathway.
2. Synergistic Effects of TFF3 Inhibition: The combination of the TFF3 inhibitor AMPC and EGFR-TKIs exhibits significant synergistic effects both in vitro and in vivo.
3. Key Role of YAP: YAP, as a key effector of the Hippo signaling pathway, plays a central role in TFF3-mediated acquired resistance.
4. Potential Clinical Applications: TFF3 inhibition may become a new strategy for overcoming EGFR-TKI resistance, particularly in patients with acquired resistance.

Other Valuable Information

The study also found a positive correlation between TFF3 expression and YAP expression, and TFF3 inhibition significantly reduced YAP transcriptional activity. This provides new insights for future therapeutic strategies targeting the Hippo signaling pathway. Additionally, serum levels of TFF3 may serve as a non-invasive biomarker for monitoring the development of EGFR-TKI resistance.

Summary

This study is the first to reveal the dual mechanisms by which TFF3 mediates EGFR-TKI resistance in LUAD and proposes TFF3 inhibition as a new strategy for overcoming resistance. These findings not only deepen our understanding of EGFR-TKI resistance mechanisms but also provide new directions for clinical treatment.