HO-1 Genetics variants and its effects in thyroid cancer biology

Abstract

In previous studies on human thyroid cancer (TC), we observed elevated levels of hemeoxygenase-1 (HO-1) protein in both cyto- plasmic and nuclear compartments. Additionally, increased HO-1 mRNA expression correlated with tumor progression. Activation of HO-1 through hemin treatment in the TPC-1 cell line promoted cell viability, proliferation, migration, and cell cycle progression, while inhibition via ZnPP had opposite effects. This study aimed to investigate the impact of genetically overexpressed HO-1 variants (full-length - FL, enzymatically inactive - H25A, and nuclear trun- cated - t-HO1) on cancer-related processes. Using stable transfec- tions of these variants into TPC-1 cells, we observed that FL and H25A forms were predominantly overexpressed in the cytoplasm, while t-HO-1 accumulated in the nucleus. Overexpression of FL and t-HO-1 significantly enhanced cell viability (p<0.0001) and migration (p<0.0001) compared to controls. In contrast, H25A overexpression hindered these processes (p<0.0001) compared to FL. In primary cultures of human thyroid tumors and normal tissues, we identified HO-1 expression in the nuclei of normal cells and in nuclei/cyto- plasm in tumor cells. Hemin treatment increased viability (p<0.0001) in tumor cells but decreased it in normal cells (p<0.0001). These findings correlate with prior evidence, demonstrating that hemin ac- tivation of HO-1 in tumor cells, through its enzymatic activity, exerts a protumor role. The current study revealed that FL and t-HO-1 vari- ants independently promoted tumor-related processes, irrespective of subcellular localization. Notably, FL- impact on viability and mi- gration seems tied to its enzymatic activity, as the H25A mutation impairs these effects. Intriguingly, nuclear HO-1 expression might differentially affect normal and tumor thyroid cells. Subsequent ex- periments will shed light on the relationship between HO-1’s subcel- lular localization, enzymatic activity, and thyroid cancer progression