PIK3CA 突变介导的 circLHFPL2 下调通过上调 PTEN 抑制结直肠癌细胞进展。
PIK3CA mutations-mediated downregulation of circLHFPL2 inhibits colorectal cancer progression via upregulating PTEN.
机构信息
Clinical Oncology Institute, Translational Medicine Center, Navy Military Medical University, 800 Xiangyin Road, Yangpu District, Shanghai, 200433, China.
Department of Oncology, Shanghai East Hospital, Tongji University School of Medicine, 150 Jimo Road, Pudong District, Shanghai, 200120, China.
出版信息
Mol Cancer. 2022 May 26;21(1):118. doi: 10.1186/s12943-022-01531-x.
BACKGROUND
PIK3CA mutation and PTEN suppression lead to tumorigenesis and drug resistance in colorectal cancer (CRC). There is no research on the role of circular RNAs (circRNAs) in regulating PIK3CA mutation and MEK inhibitor resistance in CRC.
METHODS
The expression of circLHFPL2 in PIK3CA-mutant and wild-type cells and tissues was quantified by RNA-sequencing and qRT-PCR. CCK-8 assay and colony formation assay were used to evaluate cell viability. Annexin V/PI staining was implemented to assess cell apoptosis. Luciferase assay, biotin-coupled microRNA capture, and RIP assay were used to validate the interaction among potential targets. Western blotting and qRT-PCR assays were used to evaluate the expression of involved targets. Xenograft tumor in a nude mouse model was used to explore the role of circRNAs in vivo.
RESULTS
RNA sequencing defined downregulated expression of circLHFPL2 in both PIK3CA (HCT116) and PIK3CA (DLD1) cells. CircLHFPL2 was also downregulated in PIK3CA-mutant CRC primary cells and tissues, which was correlated with poor prognosis. CircLHFPL2 was mainly localized in the cytoplasm and its downregulation was attributed to the PI3K/AKT signaling pathway activated by phosphorylating Foxo3a. CircLHFPL2 inhibited PI3KCA-Mut CRC progression both in vitro and in vivo. Furthermore, our work indicated that circLHFPL2 acts as a ceRNA to sponge miR-556-5p and miR-1322 in CRC cells and in turn modulate the expression of PTEN. Importantly, circLHFPL2 was able to overcome PIK3CA-mediated MEK inhibitor resistance in CRC cells.
CONCLUSIONS
Downregulation of circLHFPL2 sustains the activation of the PI3K/AKT signaling pathway via a positive feedback loop in PIK3CA-mutant CRC. In addition, downregulation of circLHFPL2 leads to MEK inhibitor resistance in CRC. Therefore, targeting circLHFPL2 could be an effective approach for the treatment of CRC patients harboring oncogenic PIK3CA mutations.
背景
PIK3CA 突变和 PTEN 抑制导致结直肠癌（CRC）的肿瘤发生和耐药。目前尚无关于环状 RNA（circRNA）在调节 CRC 中 PIK3CA 突变和 MEK 抑制剂耐药中的作用的研究。
方法
通过 RNA 测序和 qRT-PCR 定量检测 PIK3CA 突变型和野生型细胞和组织中 circLHFPL2 的表达。CCK-8 检测和集落形成实验用于评估细胞活力。采用 Annexin V/PI 染色评估细胞凋亡。荧光素酶报告基因实验、生物素偶联 miRNA 捕获实验和 RIP 实验用于验证潜在靶标的相互作用。Western blot 和 qRT-PCR 实验用于评估相关靶标的表达。裸鼠皮下移植瘤模型用于研究 circRNAs 在体内的作用。
结果
RNA 测序确定 PIK3CA（HCT116）和 PIK3CA（DLD1）细胞中 circLHFPL2 的表达下调。PIK3CA 突变型 CRC 原代细胞和组织中也下调了 circLHFPL2，与不良预后相关。circLHFPL2 主要定位于细胞质，其下调归因于磷酸化 Foxo3a 激活的 PI3K/AKT 信号通路。circLHFPL2 抑制了体外和体内的 PI3KCA-Mut CRC 进展。此外，我们的工作表明，circLHFPL2 作为 ceRNA 在 CRC 细胞中与 miR-556-5p 和 miR-1322 结合，并进而调节 PTEN 的表达。重要的是，circLHFPL2 能够克服 CRC 细胞中 PIK3CA 介导的 MEK 抑制剂耐药性。
结论
在 PIK3CA 突变型 CRC 中，circLHFPL2 的下调通过 PI3K/AKT 信号通路的正反馈环维持该通路的激活。此外，circLHFPL2 的下调导致 CRC 中的 MEK 抑制剂耐药性。因此，靶向 circLHFPL2 可能是治疗携带致癌性 PIK3CA 突变的 CRC 患者的有效方法。
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