Document Type

Article

Publication Date

9-7-2020

Publication Title

Oncogenesis

Abstract

cMYC (MYC) is a potent oncoprotein that is subject to post-translational modifications that affect its stability and activity. Here, we show that Serine 62 phosphorylation, which increases MYC stability and oncogenic activity, is elevated while Threonine 58 phosphorylation, which targets MYC for degradation, is decreased in squamous cell carcinoma (SCC). The oncogenic role of MYC in the development of SCC is unclear since studies have shown in normal skin that wild-type MYC overexpression can drive loss of stem cells and epidermal differentiation. To investigate whether and how altered MYC phosphorylation might affect SCC development, progression, and metastasis, we generated mice with inducible expression of MYC(WT) or MYC(T58A) in the basal layer of the skin epidermis. In the T58A mutant, MYC is stabilized with constitutive S62 phosphorylation. When challenged with DMBA/TPA-mediated carcinogenesis, MYC(T58A) mice had accelerated development of papillomas, increased conversion to malignant lesions, and increased metastasis as compared to MYC(WT) mice. In addition, MYC(T58A)-driven SCC displayed stem cell gene expression not observed with MYC(WT), including increased expression of Lgr6, Sox2, and CD34. In support of MYC(T58A) enhancing stem cell phenotypes, its expression was associated with an increased number of BrdU long-term label-retaining cells, increased CD34 expression in hair follicles, and increased colony formation from neonatal keratinocytes. Together, these results indicate that altering MYC phosphorylation changes its oncogenic activity-instead of diminishing establishment and/or maintenance of epidermal stem cell populations like wild-type MYC, pS62-MYC enhances these populations and, under carcinogenic conditions, pS62-MYC expression results in aggressive tumor phenotypes.

PubMed ID

32895364

Volume

9

Issue

9

First Page

79

Last Page

79

Share

COinS