Hemoxygenase-1 genetic variants effects on breast cancer progression

Abstract

Hemoxygenase-1 (HO-1) is a microsomal enzyme that catalyzes the degradation of the heme group, and its C-terminal truncated form can translocate to the nucleus and perform functions at the transcrip- tional level. Our laboratory has already shown that HO-1 has antitumoral effects in breast cancer. We have additionally confirmed that the HO-1 truncated form is not enzymatically active. The aim of this work was to study the effect of genetic overexpression of HO-1 vari- ants (full-length form (FL), full-length form without enzymatic activity (H25A) and nuclear truncated form (T-HO1)) on cellular processes related to cancer development, and also the molecular mechanisms through which HO-1 would modulate the cellular processes investi- gated. To accomplish this goal, we used T47D human breast cancer cell line that was stably transfected with plasmids overexpressing HO-1 variants. To analyse cell behaviour between variants, we per- formed viability assays and flow cytometry, and to quantify differen- tial protein expression we used immunofluorescence and western blot. We observed significant differences in cell viability between wild-type T47D cells and T47D cells overexpressing HO-1 variants. We found that the wild-type form is more proliferative than the FL-, H25A- and T-HO1-overexpressing forms (p<0.05, two-way ANOVA). We also observed that in H25A-overexpressing cells this behaviour results, in part, from an increase in cell death (p<0.05, two-way ANOVA). Finally, by immunofluorescence, we observed differences in the number of actin filopodia. So far, these results indicate that the overexpression of HO-1 FL seems to display an anti-tumor role. The behaviour of the H25A and the T-HO1 forms would indicate that the anti-tumor behaviour is the result of HO-1 enzymatic activity and its nuclear role. Future experiments will allow us to understand the role of the different pathways involved between HO-1 variants