Nuclear Overexpression of SAMHD1 Induces M Phase Stalling in Hepatoma Cells and Suppresses HCC Progression by Interacting with the Cohesin Complex

Emerging evidence suggests that the sterile alpha-motif (SAM) and histidine-aspartate (HD) domain-containing protein 1 (SAMHD1) is implicated in various cancers, including hepatocellular carcinoma (HCC). However, its precise role in tumor cells and the underlying mechanisms remain unclear. This study aimed to investigate the expression patterns, prognostic values, and functional role of SAMHD1 in HCC progression. We constructed liver tissue microarrays using tumor and paired paratumor tissue specimens from 187 patients with primary HCC. Our findings indicate that nuclear SAMHD1 protein levels are increased in tumors compared to paratumor tissues. Moreover, nuclear SAMHD1 levels decline in advanced tumor stages, with higher SAMHD1 nuclear staining correlating with favorable prognostic outcomes. Hepatocyte-specific SAMHD1 knockout mice, generated by crossing SAMHD1^fl/fl mice with Alb-cre mice, showed accelerated tumor progression in a diethylnitrosamine (DEN)-induced HCC model. In hepatoma cell lines, nuclear overexpression of SAMHD1 inhibited cell proliferation by stalling mitosis, independent of its deoxynucleotide triphosphohydrolase (dNTPase) function. Mechanistically, SAMHD1 interacts with the cohesin complex in nucleus, enhancing sister chromatid cohesion during cell division, which delays metaphase progression. Our findings suggest that nuclear SAMHD1 plays a critical role in slowing HCC progression by regulating mitosis, highlighting its potential as a therapeutic target by manipulating cohesin dynamics.