Endogenous DOPA inhibits melanoma through suppression of CHRM1 signaling

Abstract

Melanoma risk is 30 times higher in people with lightly pigmented skin versus darkly pigmented skin. Using primary human melanocytes representing the full human skin pigment continuum and preclinical melanoma models, we show that cell-intrinsic differences between dark and light melanocytes regulate melanocyte proliferative capacity and susceptibility to malignant transformation, independent of melanin and ultraviolet exposure. These differences result from dihydroxyphenylalanine (DOPA), a melanin precursor synthesized at higher levels in melanocytes from darkly pigmented skin. We used both high-throughput pharmacologic and genetic in vivo CRISPR screens to determine that DOPA limits melanocyte and melanoma cell proliferation by inhibiting the muscarinic acetylcholine receptor M 1 (CHRM1) signaling. Pharmacologic CHRM1 antagonism in melanoma leads to depletion of c-Myc and FOXM1, both of which are proliferation drivers associated with aggressive melanoma. In preclinical mouse melanoma models, pharmacologic inhibition of CHRM1 or FOXM1 inhibited tumor growth. CHRM1 and FOXM1 may be new therapeutic targets for melanoma.

Targeting anti-apoptotic pathways eliminates senescent melanocytes and leads to nevi regression

“…Immunohistochemistry staining was performed by the University of Pennsylvania Skin Biology and Diseases Resource-based Center (SBDRC). Tissue section quantification was performed according to previous reports 54 , 55 . Briefly, 4× photomicrograph images of representative tissue sections were taken using the Keyence BZ-X710 (Itasca, IL, USA).…”

“…293FT cells were maintained in complete DMEM and maintained in atmospheric oxygen concentrations in a 5% CO 2 , 37 °C incubator. For cells grown in organotypic skin models, primary human melanocytes and keratinocytes were extracted from fresh discarded human foreskin and surgical specimens as previously described 39,53,54 . The human primary cells were obtained from the University of Pennsylvania Skin Biology and Disease Research Core, which establishes the cultures from deidentified discarded tissues under an approved IRB exempt protocol.…”

“…Organotypic skin grafts were cultured in medium modified from previous methods 39,53,54 . Specifically, the Keratinocyte Growth Media (KGM) used for keratinocyte-only skin grafts was replaced with modified Melanocyte Xenograft Seeding Media (MXSM).…”

Stress vesicles are induced by acute mechanical force and precede the commitment of epidermal stem cells to terminal differentiation

“…Organotypic skin grafts containing human primary keratinocytes were performed as previously detailed methods [107][108][109][110] . Primary human keratinocytes that provided from SBDRC Core B were initiated from adult human skin and plated directly for experiments.…”