Loss of WT1 Drives Adaptive Plasticity in CCDC6-RET Selpercatinib-Resistant Papillary Thyroid Cancer

  • Curr Issues Mol Biol. 2026 Mar 4;48(3):274. doi: 10.3390/cimb48030274.
Giuseppe Siragusa  1 ,  Laura Tomasello  2 ,  Mattia Biondo  1 ,  Fabiola Vaglica  2 ,  Carla Giordano  2 ,  Giorgio Arnaldi  2 ,  Giuseppe Pizzolanti  2  3
Affiliations
  • 1. Department of Biological, Chemical and Pharmaceutical Sciences and Technologies (STEBICEF), University of Palermo, 90128 Palermo, PA, Italy.
  • 2. Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical Specialties (PROMISE), University of Palermo, 90127 Palermo, PA, Italy.
  • 3. Advanced Technologies Network Center (ATEN Center), University of Palermo, 90128 Palermo, PA, Italy.
PMID: 41899426 DOI: 10.3390/cimb48030274
Abstract

Background: Papillary Thyroid Cancer (PTC) harboring CCDC6-RET translocation is typically classified as a differentiated epithelial tumor. Although Selpercatinib, a RET-selective drug, was recently approved for use in advanced PTC, the emergence of drug resistance has already been observed. Tumor plasticity, including non-canonical Epithelial-Mesenchymal Transition (EMT) programs, is recognized as a key mechanism underlying drug resistance. The downregulation of the transcription factor Wilms' Tumor 1 (WT1) in Cancer is associated with increased motility, invasiveness, and metastatic potential. Methods: In this study, we developed a selpercatinib-resistant PTC-derived cell line, TPC-1-SelpR. Bioinformatic analyses were conducted to study the promoter of the CCDC6-RET gene and the transcriptomic landscape of PTC from RNAseq data. Subsequent Real-Time PCR, Western blot, and imaging techniques, such as confocal microscopy (CM) and fluorescence microscopy (FM), were employed to study the effects of WT1 loss-of-function following RNAi silencing. Results: In TPC-1-SelpR, WT1 expression appears downregulated compared to its counterpart, TPC-1. Crucially, WT1 silencing induced a context-dependent modulation of the CCDC6-RET driver: while WT1 silencing reduced CCDC6-RET expression in TPC-1, in TPC-1-SelpR, a post-transcriptional compensation of CCDC6-RET was observed. The gene expression of several factors involved in EMT, such as Twist, Vimentin, Integrin beta-1, and Profilin, was rewired in TPC-1-SelpRWT1-knockdown. Although the Vimentin protein product decreased, CM and FM analyses confirmed a reorganization of residual protein: the subcellular redistribution was more dispersed in TPC-1-SelpRWT1-knockdown. Further upregulation of the stemness factor Sox2 over the differentiation factor Sox17 occurred. These molecular changes were associated with higher cell motility of TPC-1-SelpRWT1-knockdown. Conclusions: Collectively, these findings suggest that WT1 is a critical regulator involved in tumor plasticity, thereby supporting selpercatinib resistance.

Keywords
CCDC6-RET; WT1; cancer; resistance; selpercatinib; thyroid.
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