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Updated: May 6, 2026
Spatial and Temporal Control of Murine Melanoma Initiation from Mutant Melanocyte Stem Cells
Published on: June 7, 2019
PTEN functions as a melanoma tumor suppressor by promoting host immune response
Y Dong1, J-Ae Richards2, R Gupta3
11] Department of Pathology, Yale University School of Medicine, New Haven, CT, USA [2] Department of Oral and Maxillofacial Surgery, College of Stomatology, Hebei Medical University, Shijiazhuang, China.
Abstract:
Cancer cells acquire several traits that allow for their survival and progression, including the ability to evade the host immune response. However, the mechanisms by which cancer cells evade host immune responses remain largely elusive. Here we study the phenomena of immune evasion in malignant melanoma cells. We find that the tumor suppressor phosphatase and tensin homolog (PTEN) is an important regulator of the host immune response against melanoma cells. Mechanistically, PTEN represses the expression of immunosuppressive cytokines by blocking the phosphatidylinositide 3-kinase (PI3K) pathway. In melanoma cells lacking PTEN, signal transducer and activator of transcription 3 activates the transcription of immunosuppressive cytokines in a PI3K-dependent manner. Furthermore, conditioned media from PTEN-deficient, patient-derived short-term melanoma cultures and established melanoma cell lines blocked the production of the interleukin-12 (IL-12) in human monocyte-derived dendritic cells. Inhibition of IL-12 production was rescued by restoring PTEN or using neutralizing antibodies against the immunosuppressive cytokines. Furthermore, we report that PTEN, as an alternative mechanism to promote the host immune response against cancer cells, represses the expression of programmed cell death 1 ligand, a known repressor of the host immune response. Finally, to establish the clinical significance of our results, we analyzed malignant melanoma patient samples with or without brisk host responses. These analyses confirmed that PTEN loss is associated with a higher percentage of malignant melanoma samples with non-brisk host responses compared with samples with brisk host responses. Collectively, these results establish that PTEN functions as a melanoma tumor suppressor in part by regulating the host immune response against melanoma cells and highlight the importance of assessing PTEN status before recruiting melanoma patients for immunotherapies.
Insights
The tumor suppressor phosphatase and tensin homolog (PTEN) helps the immune system fight malignant melanoma by reducing immunosuppressive cytokines and programmed cell death 1 ligand. PTEN loss in melanoma correlates with a weaker immune response, impacting immunotherapy decisions.
Area of Science:
- Immunology
- Oncology
- Molecular Biology
Background:
- Cancer cells evade immune detection through complex mechanisms.
- Malignant melanoma presents unique challenges in immune evasion.
- Understanding regulators of anti-tumor immunity is crucial for effective cancer therapy.
Purpose of the Study:
- To investigate the role of phosphatase and tensin homolog (PTEN) in regulating the immune response against malignant melanoma.
- To elucidate the molecular mechanisms by which PTEN influences immune evasion in melanoma.
- To assess the clinical relevance of PTEN status in melanoma patients undergoing immunotherapy.
Main Methods:
- Analysis of PTEN's effect on immunosuppressive cytokine expression via the phosphatidylinositide 3-kinase (PI3K) pathway.
- Investigating the role of signal transducer and activator of transcription 3 (STAT3) in PTEN-deficient melanoma.
- Assessing the impact of melanoma cell-conditioned media on dendritic cell function (IL-12 production).
- Evaluating PTEN's regulation of programmed cell death 1 ligand (PD-L1) expression.
- Correlating PTEN status with host immune response in patient melanoma samples.
Main Results:
- PTEN represses immunosuppressive cytokines by inhibiting the PI3K pathway.
- PTEN-deficient melanoma cells exhibit STAT3-dependent upregulation of immunosuppressive cytokines.
- Conditioned media from PTEN-deficient melanoma impairs IL-12 production in dendritic cells.
- PTEN also represses PD-L1 expression, a key immune checkpoint inhibitor.
- Loss of PTEN in melanoma patients is associated with reduced host immune responses.
Conclusions:
- PTEN acts as a tumor suppressor in melanoma by enhancing host anti-tumor immunity.
- PTEN regulates melanoma immune evasion through modulation of cytokine production and PD-L1 expression.
- Assessing PTEN status is clinically important for predicting immunotherapy response in melanoma patients.
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