Melanoma induces immunosuppression by up-regulating FOXP3(+) regulatory T cells.
BACKGROUND
The immune response to melanoma is rarely curative, suggesting the emergence of immunosuppression. FOXP3-expressing regulatory T cells (T(reg) cells) function to suppress immune responses. The objective of this study was to determine if melanoma evades immune surveillance, in part, by inducing T(reg) cells.


METHODS
Peripheral blood mononuclear cells (PBMCs) were isolated and exposed to melanoma-conditioned media (MCM) or control media for 1 week. The induction of T(reg) cells in these PBMCs was determined by measuring the proportion of CD25(+)FOXP3(+) T cells in all CD4(+) T cells by flow cytometry. FOXP3 expression was determined by mean fluorescence intensity (MFI) and Western blot. Supernatant cytokines were determined by ELISA.


RESULTS
Normal PBMCs exposed to MCM revealed higher proportions of T(reg) cells than those exposed to control media after 6 days (3.4% versus 1.3%, respectively, P < 0.02). The expression of FOXP3 in T(reg) cells from PBMCs exposed to MCM increased over time by MFI and Western blot but was not significantly different than those exposed to control media. The level of IL-10 and TGF-beta in supernatants after 6 days growth was higher in MCM than control media, but this did not reach statistical significance.


CONCLUSIONS
Exposure of PBMCs to melanoma results in induction of FOXP3(+) T(reg) cells.
Baumgartner
Joel
J
Department of Surgery, University of Colorado at Denver and Health Sciences Center, Denver, Colorado 80262, USA.
Wilson
Cara
C
Palmer
Brent
B
Richter
Don
D
Banerjee
Anirban
A
McCarter
Martin
M
D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000378:metabolism; D017077:Culture Media, Conditioned / Q000494:pharmacology; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007111:Immunity, Cellular / Q000187:drug effects / Q000502:physiology; D007165:Immunosuppression Therapy; D016753:Interleukin-10 / Q000378:metabolism; D008545:Melanoma / Q000276:immunology*; D012878:Skin Neoplasms / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*
D017077:Culture Media, Conditioned; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D016212:Transforming Growth Factor beta; D016753:Interleukin-10