The ?-melanocyte stimulating hormone/peroxisome proliferator activated receptor-? pathway down-regulates proliferation in melanoma cell lines.

ABSTRACT:

Background

The ?-Melanocyte Stimulating Hormone (?MSH)/Melanocortin-1 receptor (MC1R) interaction promotes melanogenesis through the cAMP/PKA pathway. The direct induction of this pathway by Forskolin (FSK) is also known to enhance melanocyte proliferation. ?MSH acts as a mitogenic agent in melanocytes and its effect on proliferation of melanoma cells is less known. We previously identified the ?MSH/Peroxisome Proliferator Activated Receptor (PPAR?) pathway as a new pathway on the B16-F10 mouse melanoma cell line. ?MSH induced the translocation of PPAR? into the nucleus as an active transcription factor. This effect was independent of the cAMP/PKA pathway and was mediated by the activation of the PI(4,5)P2/PLC pathway, a pathway which we have described to be triggered by the ?MSH-dependent MC1R stimulation. Moreover, in the same study, preliminary experiments showed that mouse melanoma cells responded to ?MSH by reducing proliferation and that PPAR? was involved in this effect. Due to its key role in the control of cell proliferation, PPAR? agonists are used in therapeutic models for different forms of cancer, including melanoma. The purpose of this study was: (a) to confirm the different proliferative behavior in response to ?MSH in healthy and in melanoma condition; (b) to verify whether the cAMP/PKA pathway and the PLC/PPAR? pathway could exert an antagonistic function in the control of proliferation; (c) to deepen the knowledge of the molecular basis responsible for the down-proliferative response of melanoma cells after exposure to ?MSH.

Methods

We employed B16-F10 cell line, a human melanoma cell line (Mel 13) and two primary cultures of human melanocytes (NHM 1 and NHM 2, respectively), all expressing a wild type MC1R and responding to the ?MSH in terms of pigmentation. We evaluated cell proliferation through: a) cell counting, b) cell cycle analysis c) protein expression of proliferation modulators (p27, p21, cyclin D1 and cyclin E).

Results

The ?MSH acted as a mitogenic agent in primary cultures of human melanocytes, whereas it determined a slow down of proliferation in melanoma cell lines. FSK, as an inducer of the cAMP/PKA pathway, reproduced the ?MSH mediated effect on proliferation in NHMs but it did not mimic the ?MSH effect on proliferation in B16-F10 and Mel 13 melanoma cell lines. Meanwhile, 3 M3-FBS (3 M3), as an inducer of PI(4,5)P2/PLC pathway, reproduced the ?MSH proliferative effect. Further experiments, treating melanoma cell lines with ?MSH in the presence/absence of GW9662, as an inhibitor of PPAR?, confirmed the key role of this transcription factor in decreasing cell proliferation in response to the hormone exposure.

Conclusions

In both melanoma cell lines, ?MSH determined the reduction of proliferation through the PI(4,5)P2/PLC pathway, employing PPAR? as an effector element. These evidence could offer perspectives for new therapeutic approaches for melanoma.

SUBMITTER: Flori E 

PROVIDER: S-EPMC5637056 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature