Prostate Cancer (PCa) is the second leading cause of cancer death in American men.

The inflammatory tumor microenvironment is a fertile niche that releases reactive oxygen species, which accelerates the malignant transformation and appears as a fine tuner of the adhesive behavior of cells. Heme oxygenase 1 (HO-1), the rate-limiting enzyme in heme degradation, represents an essential event in cellular responses to pro-oxidative and pro-inflammatory insults. As we previously reported that HO-1 over-expression impaired tumor growth and angiogenesis in vivo we sought to assess whether HO-1 could regulate the adhesive properties and the morphology of PCa cells. A bioinformatics enrichment analysis using Metacore, GeneMANIA and DAVID was performed; rendering a significant association of the HO-1 regulated genes with several proteins located in the extracellular space and cell membrane; compartments highly correlated with the adhesive behavior of cells. In an effort to understand the molecular mechanisms underlying HO-1's role in cell morphology regulation we used a proteomics approach to identify HO-1 partners. We performed GST-pull-down assays using lysates from PC3 cells transfected with either GST-tagged HO-1 or the empty vector, and the isolated proteins were subjected to MALDI-TOF/TOF analyses.

Our results showed that HO-1 interacts with Muskelin, a nucleocytoplasmic mediator of cellular morphology and adhesiveness. Up-regulation of Muskelin under HO-1 induction in PCa cells was confirmed by confocal microscopy. A high degree of nuclear overlay between HO-1 and Muskelin signals was observed when cells were exposed to hemin, a potent specific inducer of HO-1 or genetically manipulated to over-express HO-1, compared to controls. Interestingly after HO-1 induction, both protein exhibit similar sub-cellular dynamics, relocating from the cell membrane, towards the cell nuclei. Altogether, we have shown for the first time that HO-1 binds and up-regulates Muskelin, a specific factor involved in shaping cellular morphology and adhesive properties, favoring a less aggressive phenotype and further supporting the anti-tumoral function of HO-1in PCa.

Citation Format: Geraldine Gueron, Jimena Giudice, Alejandra Paez, Pia Valacco, Noelia Carabelos, Federico Schuster, Javier Cotignola, Felipe Jaworski, Daiana Leonardi, Maria Binaghi, Marcelo Marti, Nora Navone, Elba Vazquez. Unveiling the molecular significance of HO-1 and muskelin interaction: two masterminds behind the morphology and the adhesive behavior of prostate cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-43. doi:10.1158/1538-7445.AM2014-LB-43