# Linking the microbiome and immune-checkpoint in melanoma by RNF5

> **NIH NIH R01** · SANFORD BURNHAM PREBYS MEDICAL DISCOVERY INSTITUTE · 2021 · $603,580

## Abstract

Project Summary
This application is set to define a novel mechanism underlying the control of gut microbiota-immune checkpoint
interactions by the ubiquitin ligase RNF5, and the implications of such regulation to melanoma development
and response to therapy. Despite the most exciting and significant advances made in clinical management of
melanoma via the immune-checkpoint based clinical trials, mechanisms underlying their control, the
susceptibility to distinct therapies (or not), are among the fundamental questions that remain unsolved. Here,
we provide data to support a model whereby immune checkpoints are regulated by gut microbiome, which is
defined by the ubiquitin ligase RNF5. Our discovery of impaired growth of Braf/Pten mutant melanoma in
syngeneic Rnf5–/– mice, compared with Rnfwt littermates, was linked with enhanced infiltration of tumor-
infiltrating lymphocytes (TILs) (CD4 and CD8 positive), macrophages and dendritic cells in the tumors that
developed significantly slower in the Rnf5–/– mice. Strikingly, co-housing the Rnf5–/– and Rnfwt animals or
antibiotic ablation of the gut microbiota resulted in loss of the above phenotypes—tumor growth was no longer
attenuated and immune checkpoint-based phenotypes were largely lost. Assessment of the gut microbiome
revealed a distinct subset of bacterial species, which distinguish Rnf5–/– mice from their WT littermates (all
“pure” in-house maintained C57BL/6 strain). Notably, common to the distinct RNF5-microbiome are bacterial
species that generate select subset of short chain fatty acids. These observations provide the foundation for
our hypothesis that RNF5 controls the intestinal microbiota that affects immune checkpoint
mechanisms, which in turn impacts melanoma development. Our proposed studies will (i) define RNF5
effect on the gut microbiome–tumor interactions, (ii) identify microbiome-dependent changes in the regulation
of tumor immune checkpoint control by RNF5, and (iii) establish the physiological significance and impact of
RNF5 control of microbiome and immune checkpoint on melanomagenesis in different mouse strains, age, and
under select combination therapies. Our highly integrated studies will define the fundamental mechanisms that
underlie the regulation of both gut microbiome and immune checkpoints, thereby providing new insights into
therapeutic modalities for melanoma and other cancers.

## Key facts

- **NIH application ID:** 10098006
- **Project number:** 5R01CA216187-05
- **Recipient organization:** SANFORD BURNHAM PREBYS MEDICAL DISCOVERY INSTITUTE
- **Principal Investigator:** Linda Mac Pherson Bradley
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $603,580
- **Award type:** 5
- **Project period:** 2017-03-15 → 2022-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10098006

## Citation

> US National Institutes of Health, RePORTER application 10098006, Linking the microbiome and immune-checkpoint in melanoma by RNF5 (5R01CA216187-05). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10098006. Licensed CC0.

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