Department of Pathology, Xinqiao Hospital, Third Military Medical University, 183 Xinqiao Street, Shapingba District, Chongqing, 400037, People's Republic of China.
Clinical Medical Research Center, Xinqiao Hospital, Third Military Medical University, Chongqing, 400037, People's Republic of China.
J Transl Med. 2024 Jan 2;22(1):6. doi: 10.1186/s12967-023-04721-3.
Tandem C2 domains, nuclear (TC2N) is a C2 domain-containing protein that belongs to the carboxyl-terminal type (C-type) tandem C2 protein family, and acts as an oncogenic driver in several cancers. Previously, we preliminarily reported that TC2N mediates the PI3K-Akt signaling pathway to inhibit tumor growth of breast cancer (BC) cells. Beyond that, its precise biological functions and detailed molecular mechanisms in BC development and progression are not fully understood.
Tumor tissues of 212 BC patients were subjected to tissue microarray and further assessed the associations of TC2N expression with pathological parameters and FASN expression. The protein levels of TC2N and FASN in cell lines and tumor specimens were monitored by qRT-PCR, WB, immunofluorescence and immunohistochemistry. In vitro cell assays, in vivo nude mice model was used to assess the effect of TC2N ectopic expression on tumor metastasis and stemness of breast cancer cells. The downstream signaling pathway or target molecule of TC2N was mined using a combination of transcriptomics, proteomics and lipidomics, and the underlying mechanism was explored by WB and co-IP assays.
Here, we found that the expression of TC2N remarkedly silenced in metastatic and poorly differentiated tumors. Function-wide, TC2N strongly inhibits tumor metastasis and stem-like properties of BC via inhibition of fatty acid synthesis. Mechanism-wise, TC2N blocks neddylated PTEN-mediated FASN stabilization by a dual mechanism. The C2B domain is crucial for nuclear localization of TC2N, further consolidating the TRIM21-mediated ubiquitylation and degradation of FASN by competing with neddylated PTEN for binding to FASN in nucleus. On the other hand, cytoplasmic TC2N interacts with import proteins, thereby restraining nuclear import of PTEN to decrease neddylated PTEN level.
Altogether, we demonstrate a previously unidentified role and mechanism of TC2N in regulation of lipid metabolism and PTEN neddylation, providing a potential therapeutic target for anti-cancer.
串联 C2 结构域，核（TC2N）是一种含有 C2 结构域的蛋白质，属于羧基末端 C 型串联 C2 蛋白家族，在几种癌症中作为致癌驱动因子。此前，我们初步报道 TC2N 介导 PI3K-Akt 信号通路抑制乳腺癌（BC）细胞的肿瘤生长。除此之外，其在 BC 发展和进展中的精确生物学功能和详细分子机制尚不完全清楚。
对 212 例 BC 患者的肿瘤组织进行组织微阵列分析，并进一步评估 TC2N 表达与病理参数和 FASN 表达的相关性。通过 qRT-PCR、WB、免疫荧光和免疫组化监测细胞系和肿瘤标本中 TC2N 和 FASN 的蛋白水平。体外细胞实验、体内裸鼠模型用于评估 TC2N 异位表达对乳腺癌细胞转移和干性的影响。通过转录组学、蛋白质组学和脂质组学的组合，挖掘 TC2N 的下游信号通路或靶分子，并通过 WB 和 co-IP 实验探讨其潜在机制。
在这里，我们发现 TC2N 的表达在转移性和低分化肿瘤中明显沉默。功能上，TC2N 通过抑制脂肪酸合成强烈抑制 BC 的肿瘤转移和干性。机制上，TC2N 通过双重机制阻断 neddylatedPTEN 介导的 FASN 稳定。C2B 结构域对于 TC2N 的核定位至关重要，进一步证实了 TRIM21 通过与 neddylatedPTEN 竞争结合核内 FASN，来促进 FASN 的泛素化和降解。另一方面，细胞质 TC2N 与输入蛋白相互作用，从而抑制 PTEN 的核输入，降低 neddylatedPTEN 水平。
总之，我们证明了 TC2N 在调节脂质代谢和 PTEN neddylation 中的一个以前未被识别的作用和机制，为抗癌提供了一个潜在的治疗靶点。
