# Influence of Melanocyte Differentiation State on Melanoma Susceptibility

> **NIH NIH F31** · UNIVERSITY OF PENNSYLVANIA · 2020 · $45,520

## Abstract

Project Summary:
Melanoma is the most lethal skin cancer with over 90,000 new cases in United States each year. The risk of
developing melanoma is substantially greater for people with lightly pigmented skin (1:38 in the US) than those
with darkly pigmented skin (1:1000 in the US). Although this discrepancy is generally attributed to the physical
UV shielding effect of melanin pigment, the sun protective factor (SPF) of melanin is only 2-3, which seems
insufficient to explain the 40-fold difference of melanoma incidence in darkly and lightly pigmented skin. Our
preliminary data show that primary human melanocytes (MCs) from lightly pigmented skin produce less
melanin relative to primary MCs from dark skin, and this is associated with a decreased MC differentiation
state and increased proliferative capacity. Additionally, the proliferation and differentiation differences between
light and dark MCs persist upon transformation of primary MCs with medically relevant melanoma drivers
(BRAFV600E, CDK4R24C, P53R248W, and hTERT). To test if these differences translated into different melanoma
phenotypes in vivo, I engineered architecturally faithful 3-D human skin and orthotopically xenografted the
tissue on SCID mice. My preliminary data show that transformed light MCs form early melanomas, whereas
transformed dark MCs do not. This observation led us to question whether this stark difference was mediated
by melanin synthesis itself, or by intermediates of melanin synthesis, such as dihydroxyphenylalanine (DOPA).
We found that darkly pigmented MCs contain approximately 300% more DOPA, as compared to light MCs.
Previous work along with my preliminary data show that DOPA serves as a signaling molecule and inhibits
proliferation. Specifically, I found that exogenously supplied DOPA induces melanin synthesis in light MCs and
melanoma cells, but has no effect on primary dark MC, which likely contain saturating levels of endogenously
produced DOPA. The mechanism(s) of the DOPA anti-proliferative effect are currently unknown, but my
preliminary data show that DOPA inhibits canonical Gq GPCR pathways leading to a decrease in MAPK and
PI3K/AKT signaling pathways. In a collaborative effort with Dr. Bryan Roth at the University of North Carolina,
we conducted a functional screen to test whether DOPA binds to any of the ~320 non-olfactory GPCRs in the
human genome. The top hit was the Gq-coupled metabotropic glutamate receptor 5 (GRM5), which is a known
melanoma driver. Aim 1 will focus on determining the mechanism of DOPA’s anti-proliferative effect, by
specifically focusing on its inhibitory role of GRM5, or other top hits from our GPCR screen. Additionally, I
determined that DOPA inhibits growth of medically relevant syngeneic BRaf-driven melanoma in vivo. Aim 2
seeks to further understand the endogenous and exogenous roles of DOPA in melanoma inhibition in
medically-relevant melanoma models in vivo. Together, these aims will help to define the underexplored
mela...

## Key facts

- **NIH application ID:** 9991296
- **Project number:** 1F31CA250316-01
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** Miriam Doepner
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $45,520
- **Award type:** 1
- **Project period:** 2020-07-15 → 2023-07-14

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9991296

## Citation

> US National Institutes of Health, RePORTER application 9991296, Influence of Melanocyte Differentiation State on Melanoma Susceptibility (1F31CA250316-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9991296. Licensed CC0.

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