在实验性低氧条件下,结直肠癌细胞中 LAT1 的表达对 HIF-1/2α 积累无反应。

LAT1 expression in colorectal cancer cells is unresponsive to HIF-1/2α accumulation under experimental hypoxia.

机构信息

Department of Bio-System Pharmacology, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.

Integrated Frontier Research for Medical Science Division, Institute for Open and Transdisciplinary Research Initiatives (OTRI), Osaka University, Osaka, 565-0871, Japan.

出版信息

Sci Rep. 2024 Aug 23;14(1):19635. doi: 10.1038/s41598-024-70603-3.

Abstract

L-type amino acid transporter 1 (LAT1) is upregulated in various cancer types and contributes to disease progression. Previous studies have demonstrated or suggested that hypoxia-inducible factors (HIFs), the key transcription factors in hypoxic responses, control the expression of LAT1 gene in several types of cancer cells. However, this regulatory relationship has not been investigated yet in colorectal cancer (CRC), one of the cancer types in which the increased LAT1 expression holds prognostic significance. In this study, we found that neither LAT1 mRNA nor protein is induced under hypoxic condition (1% O) in CRC HT-29 cells in vitro, regardless of the prominent HIF-1/2α accumulation and HIFs-dependent upregulation of glucose transporter 1. The hypoxic treatment generally did not increase either the mRNA or protein expression of LAT1 in eight CRC cell lines tested, in contrast to the pronounced upregulation by amino acid restriction. Interestingly, knockdown of von Hippel-Lindau ubiquitin ligase to inhibit the proteasomal degradation of HIFs caused an accumulation of HIF-2α and increased the LAT1 expression in certain CRC cell lines. This study contributes to delineating the molecular mechanisms responsible for the pathological expression of LAT1 in CRC cells, emphasizing the ambiguity of HIFs-dependent transcriptional upregulation of LAT1 across cancer cells.

摘要

L 型氨基酸转运蛋白 1(LAT1)在多种癌症类型中上调,并促进疾病进展。先前的研究表明,缺氧诱导因子(HIFs)作为缺氧反应的关键转录因子,可控制几种类型癌细胞中 LAT1 基因的表达。然而,在结直肠癌(CRC)这种 LAT1 表达增加具有预后意义的癌症类型中,尚未研究这种调节关系。在这项研究中,我们发现,无论 HIF-1/2α 大量积累和 HIF 依赖性葡萄糖转运蛋白 1上调,CRC HT-29 细胞在体外缺氧条件(1% O)下,LAT1mRNA 和蛋白均未被诱导。与氨基酸限制引起的明显上调相反,缺氧处理通常不会增加所测试的 8 种 CRC 细胞系中 LAT1 的 mRNA 或蛋白表达。有趣的是,敲低 von Hippel-Lindau 泛素连接酶以抑制 HIFs 的蛋白酶体降解会导致 HIF-2α 积累并增加某些 CRC 细胞系中 LAT1 的表达。这项研究有助于描绘导致 CRC 细胞中 LAT1 病理性表达的分子机制,强调了 HIFs 依赖性转录上调 LAT1 在癌细胞中的模糊性。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/ed5d/11343765/f1bf4ff9ef0f/41598_2024_70603_Fig1_HTML.jpg

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