Tamoxifen inhibits tumor cell invasion and metastasis in mouse melanoma through suppression of PKC/MEK/ERK and PKC/PI3K/Akt pathways |
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Authors: | Hiroshi Matsuoka Masanobu Tsubaki Mitsuhiko Ogaki Tatsuki Itoh Shozo Nishida |
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Affiliation: | a Division of Pharmacotherapy, Kinki University School of Pharmacy, Kowakae, Higashi-Osaka 577-8502, Japan b Department of Pharmacy, Nara Hospital, Kinki University School of Medicine, 1248-1 Ikoma, Nara 630-0293, Japan c Department of Pharmacy, Kinki University Hospital, Osakasayama, Osaka 589-8511, Japan d Department of Pharmacy, Higahiosaka City General Hospital, Higashi-osaka, Osaka 578-8588, Japan e Department of Pathology, Kinki University School of Medicine, Osakasayama, Osaka 589-8511, Japan f Department of Otolaryngology, Juntendo University School of Medicine, Tokyo, Japan |
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Abstract: | In melanoma, several signaling pathways are constitutively activated. Among these, the protein kinase C (PKC) signaling pathways are activated through multiple signal transduction molecules and appear to play major roles in melanoma progression. Recently, it has been reported that tamoxifen, an anti-estrogen reagent, inhibits PKC signaling in estrogen-negative and estrogen-independent cancer cell lines. Thus, we investigated whether tamoxifen inhibited tumor cell invasion and metastasis in mouse melanoma cell line B16BL6. Tamoxifen significantly inhibited lung metastasis, cell migration, and invasion at concentrations that did not show anti-proliferative effects on B16BL6 cells. Tamoxifen also inhibited the mRNA expressions and protein activities of matrix metalloproteinases (MMPs). Furthermore, tamoxifen suppressed phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt through the inhibition of PKCα and PKCδ phosphorylation. However, other signal transduction factor, such as p38 mitogen-activated protein kinase (p38MAPK) was unaffected. The results indicate that tamoxifen suppresses the PKC/mitogen-activated protein kinase kinase (MEK)/ERK and PKC/phosphatidylinositol-3 kinase (PI3K)/Akt pathways, thereby inhibiting B16BL6 cell migration, invasion, and metastasis. Moreover, tamoxifen markedly inhibited not only developing but also clinically evident metastasis. These findings suggest that tamoxifen has potential clinical applications for the treatment of tumor cell metastasis. |
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Keywords: | PKC, protein kinase C MMP, matrix metalloproteinase ERK1/2, extracellular signal-regulated kinase 1/2 MAPK, mitogen-activated protein kinase MEK, mitogen-activated protein kinase kinase PI3K, phosphatidylinositol-3 kinase ECM, extracellular matrix SERM, selective estrogen receptor modulator ER, estrogen receptor |
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