跨膜emp24区域含有（TMED）蛋白已知在正常发育中起着关键作用，但据报道，与胰腺疾病、免疫系统紊乱和癌症相关。就TMED3而言，它在癌症中的作用是有争议的，然而，在恶性黑色素瘤（MM）环境下描述TMED3的证据很少。在本研究中，我们表征了TMED3在MM中的功能重要性，并确定了TMED3作为MM发展的肿瘤促进因子。TMED3的耗竭阻止了MM在体内外的发展。在机制上，我们发现TMED3能够与细胞分裂周期相关8（CDCA8）相互作用。降低CDCA8可抑制与MM发展有关的细胞事件。相反，提高CDCA8可增强细胞活力和运动性，甚至可以逆转TMED3敲低对MM发展的抑制作用。另一方面，我们发现，在TMED3下调表达的应答中，P-Akt和P-PI3K的水平下降，这部分被SC79处理后部分废除。因此，我们认为TMED3通过PI3K/Akt途径加剧MM进展。更值得注意的是，在TMED3敲低的细胞中先前降低的P-Akt和P-PI3K在过度表达CDCA8后得到恢复。同样，在添加SC79后，由于CDCA8耗竭而受到影响的细胞事件得到了改善，这意味着TMED3通过CDCA8调节PI3K-AKT途径，从而促进MM的发展。总之，本研究建立了TMED3与MM之间的联系，并为携带丰富TMED3的MM患者提供了潜在的治疗干预手段。©2023作者。

Transmembrane emp24 domain containing (TMED) proteins are known to play pivotal roles in normal development, but have been reported to be implicated in pancreatic disease, immune system disorders, and cancers. As far as TMED3 is concerned, its roles in cancers are controversial. However, evidence describing TMED3 in the context of malignant melanoma (MM) is scarce.In this study, we characterized the functional significance of TMED3 in MM and identified TMED3 as a tumor-promoting factor in MM development. Depletion of TMED3 arrested the development of MM in vitro and in vivo. Mechanistically, we found that TMED3 could interact with Cell division cycle associated 8 (CDCA8). Knocking down CDCA8 suppressed cell events associated with MM development. On the contrary, elevating CDCA8 augmented cell viability and motility and even reversed the inhibitory effects of TMED3 knockdown on MM development. On the other hand, we found that the levels of P-Akt and P-PI3K were decreased in response to TMED3 downregulation, which was partially abolished following SC79 treatment. Thus, our suspicion was that TMED3 exacerbates MM progression via PI3K/Akt pathway. More notably, previously decreased P-Akt and P-PI3K in TMED3-depleted cells were rescued after overexpressing CDCA8. Also, previously impaired cell events due to CDCA8 depletion were ameliorated after SC79 addition, implying that TMED3 regulates PI3K-AKT pathway via CDCA8, thereby promoting MM development.Collectively, this study established the link between TMED3 and MM, and provides a potential therapeutic intervention for patients with MM harboring abundant TMED3.© 2023. The Author(s).