Plectin 1d Isoform as a Potential Regulator of Metastatic Progression in Papillary Thyroid Carcinoma

Papillary thyroid carcinoma (PTC) typically exhibits a favorable prognosis; however, lymph node and distant metastases continue to present significant clinical challenges. Plectin isoform 1d (PLEC 1d) contributes to myofiber integrity and is implicated in cytoskeletal organization and cancer cell motility, but its role in PTC progression is largely unknown. In this study, PLEC 1d expression was examined by RT-PCR in three PTC cell lines (MDA-T32, MDA-T41, MDA-T120) and normal thyroid cells (Nthy-ori-3-1). CRISPR-Cas9-mediated knockdown (KD) of PLEC 1d was performed in MDA-T41 cells, with KD efficiency confirmed by RT-qPCR. Cell proliferation and migration were assessed using EdU incorporation and wound-healing assays, respectively. RNA sequencing (RNA-seq) combined with RT-qPCR and Western blotting was employed to identify downstream targets. Accordingly, PLEC 1d mRNA and total plectin protein levels were substantially elevated only in MDA-T41 cells. PLEC 1d KD reduced proliferation by 6.6% and migration by 26%. Transcriptomic analysis revealed 170 differentially expressed genes, including significant downregulation of LAMA4, MMP1, and HEY1. HEY1 downregulation was confirmed at both mRNA and protein levels. Although LAMA4 and MMP1 were also downregulated following PLEC 1d KD, LAMA4 mRNA expression varied across PTC cell lines, suggesting cell-line-specific regulation. Notably, MMP1 was consistently upregulated at the mRNA level in all PTC cell lines, while HEY1 showed elevated expression at both the transcript and protein levels. Collectively, these findings indicate that PLEC 1d enhances cell migration and may contribute to cellular processes associated with metastatic behavior in a subset of PTC cells, potentially through a HEY1-dependent mechanism.