Nuclear interaction of Arp2/3 complex and BRAFV600E promotes aggressive behavior and vemurafenib resistance of thyroid cancer

Mourad Zerfaoui; Koji Tsumagari; Eman Toraih; Youssef Errami; Emmanuelle Ruiz; Mohammed Sohail M Elaasar; Moroz Krzysztof; Andrew B Sholl; Sameh Magdeldin; Mohamed Soudy; Zakaria Y Abd Elmageed; A Hamid Boulares; Emad Kandil

Nuclear interaction of Arp2/3 complex and BRAF^V600E promotes aggressive behavior and vemurafenib resistance of thyroid cancer

Am J Cancer Res. 2022 Jul 15;12(7):3014-3033. eCollection 2022.

Authors

Affiliations

¹ Department of Surgery, Tulane University School of Medicine USA.
² Department of Pathology, Tulane University School of Medicine USA.
³ Department of Otolaryngology, Tulane University School of Medicine USA.
⁴ Proteomics Research Program Unit, Basic Research Department, Children Cancer Hospital Cairo Egypt.
⁵ Department of Physiology, Faculty of Veterinary Medicine, Suez Canal University Ismailia 41522, Egypt.
⁶ Department of Pharmacology, Edward Via College of Osteopathic Medicine, University of Louisiana Monroe, USA.
⁷ Department of Pharmacology, LSU Health Sciences Center New Orleans, LA, USA.

PMID: 35968344
PMCID: PMC9360225

Abstract

The presence of mutant BRAF ^V600E correlates with the risk of recurrence in papillary thyroid cancer (PTC) patients. However, not all PTC patients with BRAF ^V600E are associated with poor prognosis. Thus, understanding the mechanisms by which certain PTC patients with nuclear BRAF ^V600E become aggressive and develop resistance to a selective BRAF inhibitor, PLX-4032, is urgently needed. The effect of nuclear localization of BRAF^V600E using in vitro studies, xenograft mouse-model and human tissues was evaluated. PTC cells harboring a nuclear localization signal (NLS) of BRAF^V600E were established and examined in nude mice implanted with TPC1-NLS-BRAF^V600E cells followed by PLX-4032 treatment. Immunohistochemical (IHC) analysis was performed on 100 PTC specimens previously confirmed that they have BRAF^V600E mutations. Our results demonstrate that 21 of 100 (21%) PTC tissues stained with specific BRAF^V600E antibody had nuclear staining with more aggressive features compared to their cytosolic counterparts. In vitro studies show that BRAF^V600E is transported between the nucleus and the cytosol through CRM1 and importin (α/β) system. Sequestration of BRAF^V600E in the cytosol sensitized resistant cells to PLX-4032, whereas nuclear BRAF^V600E was associated with aggressive phenotypes and developed drug resistance. Proteomic analysis revealed Arp2/3 complex members, actin-related protein 2 (ACTR2 aliases ARP2) and actin-related protein 3 (ACTR3 aliases ARP3), as the most enriched nuclear BRAF^V600E partners. ACTR3 was highly correlated to lymph node stage and extrathyroidal extension and was validated with different functional assays. Our findings provide new insights into the clinical utility of the nuclear BRAF^V600E as a prognostic marker for PTC aggressiveness and determine the efficacy of selective BRAF^V600E inhibitor treatment which opens new avenues for future treatment options.

Keywords: ACTR2 (ARP2); ACTR3 (ARP3); Arp2/3 complex; BRAFV600E; Thyroid cancer; nuclear localization; poor prognosis; vemurafenib resistance.

Grants and funding

U54 GM104940/GM/NIGMS NIH HHS/United States