Exploring NODAL-Induced Endoplasmic Reticulum Stress as a Potential Tumour- Suppressive Mechanism in Thyroid Cancer

Abstract

Thyroid cancer is the most prevalent endocrine malignancy, with a rising incidence globally. While most thyroid cancers have favourable prognoses, aggressive subtypes such as anaplastic thyroid carcinoma remain highly lethal. In this context, the embryonic morphogen NODAL, part of the TGF-β superfamily, has emerged as a relevant factor, as it is normally inactive in adult tissues but becomes re-expressed in various malignancies, where it is associated with enhanced invasion, metastasis, and cellular plasticity. This study investigates how NODAL influences endoplasmic reticulum (ER) stress and tumourigenicity in thyroid cancer cells. Given the thyroid gland’s uniquely high protein synthesis and secretion demands, its cells are particularly vulnerable to ER stress. While moderate ER stress supports tumour survival through adaptive mechanisms, excessive or prolonged ER stress can induce apoptosis. In other cancers, NODAL reactivation has been shown to remodel the secretome and promote aggressive phenotypes. However, in the thyroid, such reprogramming may exceed the protein-folding capacity, resulting in ER stress. We hypothesize that NODAL promotes a secretory phenotype in thyroid cancer cells, triggering ER stress and ultimately reducing tumourigenicity. Using BCPAP and 8305C thyroid cancer cell lines, we examined NODAL-induced changes in mRNA abundance, protein expression, and secretion through transcriptomic and proteomic analyses. Functional assays, including proliferation, migration, and sphere formation assays, assessed tumourigenic potential. ER stress activation was evaluated by measuring unfolded protein response markers, while tumour xenograft models provided in vivo validation. Our results demonstrate that NODAL overexpression significantly upregulates secretory pathway components, increasing ER stress markers such as GRP78 and CHOP. This correlates with reduced proliferation, migration, and self-renewal capacity. In vivo, NODAL-expressing tumours exhibit decreased growth and metastatic potential. These findings suggest that NODAL-induced ER stress may act as a tumour-suppressive mechanism in thyroid cancer. Although NODAL promotes aggressive behaviour in other malignancies, its reactivation in thyroid cells appears to overwhelm their secretory machinery, triggering stress responses that impair tumourigenicity. By leveraging ER stress to limit tumour progression, targeting NODAL-associated pathways could offer promising therapeutic strategies for aggressive thyroid cancers.