IGF-1R is a molecular determinant for response to p53 reactivation therapy in conjunctival melanoma.

Abstract

As the p53 tumor suppressor is rarely mutated in conjunctival melanoma (CM), we investigated its activation as a potential therapeutic strategy. Preventing p53/Mdm2 interaction by Nutlin-3, the prototypical Mdm2 antagonist, or via direct siRNA Mdm2 depletion, increased p53 and inhibited viability in CM cell lines. The sensitivity to Nutlin-3 p53 reactivation with concomitant Mdm2 stabilization was higher than that achieved by siRNA, indicative of effects on alternative Mdm2 targets, identified as the cancer-protective IGF-1R. Nutlin-3 treatment increased the association between IGF-1R and β-arrestin1, the adaptor protein that brings Mdm2 to the IGF-1R, initiating receptor degradation in a ligand-dependent manner. Controlled expression of β-arrestin1 augmented inhibitory Nutlin-3 effects on CM survival through enhanced IGF-1R degradation. Yet, the effect of IGF-1R downregulation on cell proliferation is balanced by β-arrestin1-induced p53 inhibition. As mitomycin (MMC) is a well-established adjuvant treatment for CM, and it triggers p53 activation through genotoxic stress, we evaluated how these alternative p53-targeting strategies alter the cancer-relevant bioactivities of CM. In 2D and 3D in vitro models, Nutlin-3 or MMC alone, or in combination, reduces the overall cell tumor growth ~30%, with double treatment inhibition rate only marginally higher than single-drug regimens. However, histopathological evaluation of the 3D models revealed that Nutlin-3 was the most effective, causing necrotic areas inside spheroids and complete loss of nuclear staining for the proliferative marker Ki67. These findings were further validated in vivo; zebrafish xenografts demonstrate that Nutlin-3 alone has higher efficacy in restraining CM tumor cell growth and preventing metastasis. Combined, these results reveal that β-arrestin1 directs Mdm2 toward different substrates, thus balancing IGF-1R pro-tumorigenic and p53-tumor suppressive signals. This study defines a potent dual-hit strategy: simultaneous control of a tumor-promoter (IGF-1R) and tumor-suppressor (p53), which ultimately mitigates recurrent and metastatic potential, thus opening up targeted therapy to CM.

• Authors: Dawei Song, Sonia Cismas, Caitrin Crudden, Eric Trocme, Claire Worrall, Naida Suleymanova, Tingting Lin, Huiyuan Zheng, Stefan Seregard, Ada Girnita, Leonard Girnita
• Journal: Oncogene (Oncogene) Vol. 41 Issue 4 Pg. 600-611 (01 2022) ISSN: 1476-5594 [Electronic] England
• PMID: 34785779 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2021. The Author(s), under exclusive licence to Springer Nature Limited.

Chemical References

• Igf1r protein, mouse
• Tumor Suppressor Protein p53
• Receptor, IGF Type 1

Topics

• Animals
• Conjunctival Neoplasms (genetics, pathology)
• Humans
• Male
• Melanoma (genetics, pathology)
• Mice
• Receptor, IGF Type 1 (metabolism)
• Transfection
• Tumor Suppressor Protein p53 (genetics)