Next generation sequencing of A375 melanoma cell line revealed a complex regulatory network when IGFBP5 overexpressed

IGFBP5, a critical regulators of insulin-like growth factors, has been reported to be involved in many kinds of carcinogenesis and cancer metastases. The role of IGFBP5 in human malignant melanoma (MM), however, remains largely unknown. In this study, we demonstrated that IGFBP5 was aberrantly expressed in human melanoma cells and cancer tissues. Overexpression of IGFBP5 dramatically inhibited the proliferation, migration and invasion of human melanoma cells, whereas knockdown of IGFBP5 by shRNA resulted in the opposite effects, enhanced the cell proliferation, migration and metastasis. In addition, IGFBP5 overexpression suppressed the growth and metastasis of melanoma xenograft tumor in vivo and IGFBP5 overexpression inhibited epithelial–mesenchymal transition (EMT) phenotype and stem cell property of tumor cell, with decreased expression of HIF1α, E-cadherin and stem cell markers NANOG, SOX2, OCT4, KLF4 and CD133. Moreover, IGFBP5 exhibited its growth inhibitory activity through inhibition of extracellular signal-regulated Kinase (ERK) and P38-MAPK signaling pathway. Taken together, our findings indicate that IGFBP5 acts as tumor suppressor roles in MM through the modulation of ERK1/2 and P38-MAPK signaling pathway as well as EMT procession and cell stemness, suggesting IGFBP5 as a novel target for human melanoma diagnosis and therapy.

胰岛素样生长因子结合蛋白5（IGFBP5）作为胰岛素样生长因子的关键调控因子，已有研究表明其参与多种肿瘤发生与癌转移进程。然而，IGFBP5在人类恶性黑色素瘤（MM）中的具体作用仍尚不明确。本研究证实，IGFBP5在人类黑色素瘤细胞及癌组织中存在异常表达。过表达IGFBP5可显著抑制人类黑色素瘤细胞的增殖、迁移与侵袭能力；而通过短发夹RNA（shRNA）敲低IGFBP5则会产生相反效应，促进细胞增殖、迁移与转移。此外，体内实验显示，IGFBP5过表达可抑制黑色素瘤异种移植瘤的生长与转移；同时，IGFBP5过表达可抑制肿瘤细胞的上皮间质转化（EMT）表型及干细胞特性，且伴随缺氧诱导因子1α（HIF1α）、E-钙粘蛋白（E-cadherin）以及干细胞标志物NANOG、SOX2、OCT4、KLF4和CD133的表达下调。进一步机制研究表明，IGFBP5通过抑制细胞外信号调节激酶（ERK）与P38丝裂原活化蛋白激酶（P38-MAPK）信号通路发挥生长抑制活性。综上，本研究结果显示，IGFBP5可通过调控ERK1/2与P38-MAPK信号通路、上皮间质转化进程及细胞干性，在恶性黑色素瘤中发挥肿瘤抑制因子的作用，提示IGFBP5可作为人类黑色素瘤诊断与治疗的新型靶点。