Pharmacological Inhibition of SP1 Reverses Cancer Stemness and Enhances Sorafenib Efficacy in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a highly heterogeneous malignancy characterized by poor prognosis and limited therapeutic response. Cancer stem cells (CSCs) contribute to tumor progression, therapeutic resistance, and tumor recurrence. Among transcriptional regulators potentially involved in these processes, Specificity Protein 1 (SP1) has emerged as a candidate integrator of oncogenic and epigenetic signaling networks. However, its contribution to CSC-associated phenotypes and drug resistance in HCC remains incompletely defined. In this study, we combined transcriptomic analyses of TCGA datasets with functional experiments in HCC cell lines (Huh7 and HepG2). SP1-associated transcriptional programs were targeted pharmacologically using mithramycin A (MIT-A) and genetically using siRNA-mediated knockdown. The effects were assessed by RNA sequencing, RT-qPCR, Western blotting, flow cytometry, and functional assays evaluating proliferation, migration, CSC-associated properties, and response to sorafenib. MIT-A treatment markedly reduced the expression of stemness-associated transcription factors (NANOG, OCT4, SOX2) and CSC markers (CD133, CD24), impaired CSC-related functions including ALDH activity and the Side Population phenotype, and inhibited cell proliferation and migration. MIT-A also sensitized both parental and sorafenib-resistant HCC cells to sorafenib, associated with modulation of apoptotic regulators and reduced transporter-mediated efflux activity. SP1 knockdown partially reproduced several of these effects, supporting a contribution of SP1-dependent transcriptional programs to these phenotypes. Overall, these findings identify SP1-associated transcriptional networks as potential regulators of CSC features and therapeutic resistance in HCC and support targeting SP1-associated transcriptional programs as a strategy to enhance sorafenib efficacy.