Toll-Like Receptor 4 Signaling Promotes the Migration of Human Melanoma Cells
Toll-Like Receptor 4 Signaling Promotes the Migration of Human Melanoma Cells
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DOI：
10.1620/tjem.234.57
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发表时间：
2014-09-01
影响因子：
2.2
通讯作者：
Okuyama, Ryuhei
中科院分区：
文献类型：
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作者：
Takazawa, Yuko;Kiniwa, Yukiko;Okuyama, Ryuhei
免疫细胞Toll样受体(TLRs)识别保守的微生物成分，导致免疫和炎症反应。然而，TLRs也在癌细胞中表达，包括表达TLR2-4的黑色素瘤细胞。TLR4配体作为免疫疗法已经受到重视；因此，我们评估了代表不同类型黑色素瘤的TLR4在人类黑色素瘤标本(29个原发灶和28个转移灶)中的表达。免疫组织化学显示，TLR4在黑色素瘤皮损中的表达比例很高(=90%)。接下来，用TLR4阳性(TLR4(+))黑色素瘤细胞系501mel和888mel，以及TLR4阴性(TLR4(-))928mel黑色素瘤细胞系评估TLR4在细胞增殖和迁移中的作用。TLR4激动剂脂多糖可促进TLR4(+)黑色素瘤细胞的增殖，但不能促进TLR4(-)928mel细胞的增殖。针对TLR4或TLR4下游分子髓系分化主要反应基因88(MyD88)的小干扰RNA(SiRNA)可阻断TLR4信号转导通路，从而阻断内毒素对888mel细胞的促增殖作用。然而，下调TLR4或MyD88的表达并不影响内毒素诱导的501mel细胞的增殖，提示残留的TLR4信号足以维持细胞的增殖。相反，脂多糖促进TLR4(+)黑色素瘤细胞的迁移，这种作用被TLR4或MyD88基因敲除后显著抑制。此外，即使在没有内毒素的情况下，TLR4基因敲除也会减少细胞的迁移，这表明黑色素瘤细胞中存在内源性TLR4配体(S)。TLR4信号可能有助于黑色素瘤的进展，当使用TLR4配体作为癌症的辅助治疗时应谨慎。
Immune cell Toll-like receptors (TLRs) recognize conserved microbial components, leading to immune and inflammatory responses.. However, TLRs are also expressed in cancer cells, including melanoma cells, which express TLR2-4. TLR4 ligands have received attention as immunotherapies; therefore, we assessed the expression of TLR4 in human melanoma specimens (29 primary lesions and 28 metastatic lesions) representing different types of melanoma. A high percentage (>= 90%) of melanoma lesions expressed TLR4, as judged by immunohistochemistry. Next, the role of TLR4 in cell proliferation and migration was assessed using the TLR4-positive (TLR4(+)) melanoma cell lines 501mel and 888mel, and TLR4-negative (TLR4(-)) 928mel melanoma cells. Lipopolysaccharide (LPS), a TLR4 agonist, increased the proliferation of TLR4(+) melanoma cells but not of TLR4(-) 928mel cells. The proliferation-inducing effect of LPS in 888mel cells was abolished by blockade of TLR4 signaling via treatment with short interfering RNA (siRNA) targeting TLR4 or myeloid differentiation primary response gene 88 (MyD88), a molecule downstream of TLR4. However, knockdown of TLR4 or MyD88 expression did not affect the LPS-induced proliferation of 501mel cells, suggesting that residual TLR4 signaling is sufficient to maintain cell proliferation. By contrast, LPS increased the migration of TLR4(+) melanoma cells, and this effect was substantially inhibited by TLR4 or MyD88 knockdown. Furthermore, TLR4 knockdown decreased cell migration even in the absence of LPS, suggesting the presence of an endogenous TLR4 ligand(s) in melanoma cells. TLR4 signaling may contribute to melanoma progression, and caution should be exercised when using TLR4 ligands as adjuvant therapy for cancer.