News Release 

Moffitt researchers identify molecular characteristics of leptomeningeal melanoma metastases

The microenvironment of leptomeningeal melanoma metastases is enriched for molecules critical to melanoma cell survival and growth

H. Lee Moffitt Cancer Center & Research Institute

TAMPA, Fla. - Patients with advanced melanoma who develop metastases in the leptomeninges, the fluid filled membranes surrounding the brain and spinal cord, have an extremely dismal prognosis. Most patients only survive for 8 to 10 weeks after diagnosis. One reason for this poor prognosis is that very little information is known about the molecular development of leptomeningeal melanoma metastases (LMM), making it difficult to develop effective therapies. Researchers in Moffitt Cancer Center's Donald A. Adam Melanoma and Skin Cancer Center of Excellence and the Department of Neuro-Oncology sought to change this by performing an extensive analysis of the molecular characteristics of the cerebrospinal fluid of patients with LMM. Their findings were published in Clinical Cancer Research, a journal of the American Association for Cancer Research.

Cancer development and progression are highly regulated by intricate interactions between cancer cells and the surrounding environment. Melanoma cells that invade and metastasize into the leptomeninges interact with the surrounding cerebrospinal fluid. Moffitt researchers wanted to improve their understanding of the development of LMM by analyzing the protein and RNA composition of cerebrospinal fluid from patients with LMM. They compared the molecular profiles of 8 control patients without LMM to 8 patients with LMM, including one LMM patient who had an extraordinary response to treatment and was still alive more than 35 months after diagnosis.

They discovered that the cerebrospinal fluid from LMM patients was enriched for proteins involved in innate immunity, proteases and the IGF-signaling pathway. The most commonly altered protein was TGF-β1. Interestingly, the one patient who had an extraordinary response to treatment displayed high levels of these proteins at baseline, but expression levels decreased as the patient responded to treatment. However, the protein expression patterns in the remaining LMM patients who had poor responses to treatment were high at baseline and remained high throughout treatment and disease progression.

The researcher team, led by Keiran Smalley, Ph.D., director of the Donald A. Adam Melanoma and Skin Cancer Center of Excellence and Peter Forsyth, M.D., Chair of the Department of Neuro-Oncology, hypothesized that the cerebrospinal fluid of LMM patients could impact melanoma cells by modulating their molecular profile. They confirmed this hypothesis by incubating cerebrospinal fluid from the LMM patients with melanoma cells and discovered that the fluid was able to induce activation of proteins and signaling pathways involved in malignant progression, including the PI3K/AKT pathway, integrins, B cell signaling, mitotic cell cycle progression, TNFR, TGF-β and oxidative stress.

Their findings demonstrate that the cerebrospinal fluid from LMM patients who did not respond to treatment promoted survival of melanoma cells, while the cerebrospinal fluid from the extraordinary responder did not promote survival. These observations suggest that molecules exist within the cerebrospinal fluid that can stimulate melanoma cell survival and prevent cell death. The researchers reported that one of these survival molecules is TGF-β. The patient who responded well to treatment had very low to undetectable levels of cerebrospinal fluid TGF-β, while those patients who did not respond to treatment had much higher levels of TGF-β.

The researchers hope that their data will provide important knowledge about LMM and offer insights into potential therapeutic targets. "It is likely that the environment of LMM is a key regulator of both disease progression and therapeutic response. Improved knowledge about the microenvironment of LMM may allow novel therapeutic strategies to be developed that can delay disease progression," explained Smalley.

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This study was supported by grants from the National Institutes of Health, the Department of Defense and the State of Florida.

About Moffitt Cancer Center

Moffitt is dedicated to one lifesaving mission: to contribute to the prevention and cure of cancer. The Tampa-based facility is one of only 51 National Cancer Institute-designated Comprehensive Cancer Centers, a distinction that recognizes Moffitt's scientific excellence, multidisciplinary research, and robust training and education. Moffitt is a Top 10 cancer hospital and has been nationally ranked by U.S. News & World Report since 1999. Moffitt's expert nursing staff is recognized by the American Nurses Credentialing Center with Magnet® status, its highest distinction. With more than 6,500 team members, Moffitt has an economic impact in the state of $2.4 billion. For more information, call 1-888-MOFFITT (1-888-663-3488), visit MOFFITT.org, and follow the momentum on Facebook, Twitter, Instagram and YouTube.

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