De Stefano, M. A. | bioRxiv Science

bioRxiv2025

Type 2 Deiodinase in Cancer-Associated Fibroblasts is required to sustain growth of poorly and undifferentiated thyroid cancer

Poorly differentiated (PDTC) and anaplastic thyroid carcinomas (ATC) are characterized by rapid progression and poor patient survival. While the tumor microenvironment (TME) - particularly cancer-associated bibroblasts (CAFs)- plays a crucial role in supporting tumor growth, its metabolic contribution remains poorly understood. Here, we identify a critical role for type 2 deiodinase (D2), the enzyme that activates the thyroid hormone (TH) thyroxine (T4) into the biologically active triiodothyronine (T3), in sustaining a pro-tumorigenic TME in PDTC and ATC. We show that D2 is expressed not only in thyroid epithelial cancer cells, but at even higher levels in CAFs, especially inblammatory CAFs (iCAFs). In in vivo mouse models, pharmacological inhibition of D2 reduces tumor growth and alters composition of CAFs. In 3D co-culture spheroids, D2 activity proves essential for supporting tumor cell proliferation by establishing a paracrine loop between stromal and epithelial cancer cells that amplibies local TH signaling. Notably, human PDTC organoids expressing D2 respond to modulation of TH levels, conbirming the functional relevance of this metabolic axis in human tumors. In conclusion, these bindings identify D2 as a key mediator of stromal-epithelial crosstalk in PDTC and ATC, and highlight local TH metabolism as a potential therapeutic target in these lethal cancers.

cancer biology↗

bioRxiv2025

Targeted p63 isoform switch corrects dominant mutations in AEC syndrome without disrupting epidermal homeostasis

The transcription factor p63 is a master regulator of stratified epithelial development, and its disruption causes severe congenital defects affecting the skin, limbs, and craniofacial structures in both humans and mice. Among p63-related disorders, Ankyloblepharon-Ectodermal Defects-Cleft Lip/Palate (AEC) syndrome is caused by dominant mutations primarily affecting the Sterile Alpha Motif (SAM) domain and the Transactivation Inhibitory Domain (TID) of the TP63 gene, which are unique to the p63 isoform. These mutations promote protein aggregation and transcriptional dysregulation, ultimately leading to debilitating skin erosions, suggesting that isoform-specific strategies could be therapeutically relevant. To explore a therapeutic strategy based on isoform switching, we generated a conditional mouse model with deletion of exon 13, resulting in replacement of p63 by the shorter p63{beta} isoform, which is expressed in the skin at lower levels. Although we found that p63 is required for limb and palate development, p63{beta} proved sufficient to support epidermal formation, postnatal skin homeostasis, and wound healing. At the molecular level, the switch from p63 to p63{beta} preserved chromatin binding and global transcriptional programs in keratinocytes. We next used genome editing to delete exon 13 in human primary keratinocytes, inducing a switch from p63 to p63{beta}. This isoform switch maintained normal proliferation and global gene expression. Importantly, p63{beta} expression in AEC patient-derived keratinocytes rescued protein aggregation, restored mechanical integrity, and normalized epidermal gene expression. Together, these findings demonstrate that p63{beta} can functionally compensate for p63 in the skin and establish and indicate that isoform switching could offer a new treatment option for AEC syndrome.

molecular biology↗