Nuclear Localization of BRAFV600E Is Associated with HMOX-1 Upregulation and Aggressive Behavior of Melanoma Cells

Mourad Zerfaoui; Eman Toraih; Emmanuelle Ruiz; Youssef Errami; Abdallah S Attia; Moroz Krzysztof; Zakaria Y Abd Elmageed; Emad Kandil

doi:10.3390/cancers14020311

Nuclear Localization of BRAF^V600E Is Associated with HMOX-1 Upregulation and Aggressive Behavior of Melanoma Cells

Cancers (Basel). 2022 Jan 9;14(2):311. doi: 10.3390/cancers14020311.

Authors

Mourad Zerfaoui¹, Eman Toraih¹, Emmanuelle Ruiz¹, Youssef Errami¹, Abdallah S Attia¹, Moroz Krzysztof², Zakaria Y Abd Elmageed^{1

3}, Emad Kandil¹

Affiliations

¹ Department of Surgery, Tulane University School of Medicine, New Orleans, LA 70112, USA.
² Department of Pathology, Tulane University School of Medicine, New Orleans, LA 70112, USA.
³ Department of Pharmacology, Edward Via College of Osteopathic Medicine, University of Louisiana, Monroe, LA 71203, USA.

Abstract

Background: Previously, we have demonstrated that nuclear BRAF^V600E is associated with melanoma aggressiveness and vemurafenib resistance. However, the underlying mechanisms of how nuclear localization of BRAF^V600E promotes cell aggressiveness have not yet been investigated. Despite therapeutic advancements targeting cutaneous melanoma, unknown cellular processes prevent effective treatment for this malignancy, prompting an urgent need to identify new biological targets. This study aims to explore the association of inducible heme oxygenase 1 (HMOX-1) with nuclear BRAF^V600E in promoting melanoma aggressiveness.

Methods: Proteomics analysis was performed to identify the interacting partner(s) of nuclear BRAF^V600E. Immunohistochemistry was applied to evaluate the levels of HMOX-1 and nuclear BRAF^V600E expression in melanoma and adjacent healthy tissues. Immunofluorescence assessed the nuclear localization of BRAF^V600E in vemurafenib-resistant A375R melanoma cells. Further study of HMOX-1 knockdown or BRAF^V600E overexpression in melanoma cells suggested a role for HMOX-1 in the regulation of cell proliferation in vivo and in vitro. Finally, Western blot analysis was performed to confirm the pathway by which HMOX-1 mediates Akt signaling.

Results: Proteomics results showed that HMOX-1 protein expression was 10-fold higher in resistant A375R cells compared to parental counterpart cells. In vitro and in vivo results illustrate that nuclear BRAF^V600E promotes HMOX-1 overexpression, whereas HMOX-1 reduction represses melanoma cell proliferation and tumor growth. Mechanistic studies revealed that HMOX-1 was associated with nuclear BRAF^V600E localization, thus promoting melanoma proliferation via a persistent activation of the AKT pathway.

Conclusions: Our results highlight a previously unknown mechanism in which the nuclear BRAF^V600E/HMOX-1/AKT axis plays an essential role in melanoma cell proliferation. Targeting HMOX-1 could be a novel method for treating melanoma patients who develop BRAF inhibitor resistance.

Keywords: HMOX-1; aggressiveness; melanoma; nuclear BRAFV600E; poor prognosis; vemurafenib resistance.

Abstract

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