Probes for LONG

The phosphoinositide 3-kinase (PI3K) pathway represents the most hyperactivated oncogenic pathway in triple-negative breast cancer (TNBC), a highly aggressive tumor subtype encompassing ∼15% of breast cancers and which possesses no targeted therapeutics. Despite critical contributions of its signaling arms to disease pathogenesis, PI3K pathway inhibitors have not achieved expected clinical responses in TNBC, owing largely to a still-incomplete understanding of the compensatory cascades that operate downstream of PI3K. Here, we investigated the contributions of long noncoding RNAs (lncRNAs) to PI3K activities in clinical and experimental TNBC and discovered a prominent role for LINC01133 as a PI3K-AKT signaling effector. We found that LINC01133 exerted protumorigenic roles in TNBC and that it governed a previously undescribed mTOR Complex 2 (mTORC2)-dependent pathway that activated AKT in a PI3K-independent manner. Mechanistically, LINC01133 induced the expression of the mTORC2 component PROTOR1/PRR5 by competitively coupling away its negative messenger RNA (mRNA) regulator, the heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2B1). PROTOR1/PRR5 in turn was sufficient and necessary for LINC01133-triggered functions, casting previously unappreciated roles for this Rictor-binding protein in cellular signaling and growth. Notably, LINC01133 antagonism undermined cellular growth, and we show that the LINC01133-PROTOR1/PRR5 pathway was tightly associated with TNBC poor patient survival. Altogether, our findings uncovered a lncRNA-driven signaling shunt that acts as a critical determinant of malignancy downstream of the PI3K pathway and as a potential RNA therapeutic target in clinical TNBC management.

Long noncoding RNAs (lncRNAs) are functionally associated with cancer development and progression. Although gene copy number variation (CNV) is common in hepatocellular carcinoma (HCC), it is not known how CNV in lncRNAs affects HCC progression and recurrence. We aimed to identify a CNV-related lncRNA involved in HCC progression and recurrence and illustrate its underlying mechanisms and prognostic value. We analyzed the whole genome sequencing (WGS) data of matched cancerous and noncancerous liver samples from 49 patients with HCC to identify lncRNAs with CNV. The results were validated in another cohort of 238 paired HCC and nontumor samples by TaqMan copy number assay. We preformed Kaplan-Meier analysis and log-rank test to identify lncRNA CNV with prognostic value. We conducted loss- and gain-of-function studies to explore the biological functions of LINC01133 in vitro and in vivo. The competing endogenous RNAs (ceRNAs) mechanism was clarified by microRNA sequencing (miR-seq), quantitative real-time PCR (qRT-PCR), western blot, and dual-luciferase reporter assays. We confirmed the binding mechanism between lncRNA and protein by RNA pull-down, RNA immunoprecipitation, qRT-PCR, and western blot analyses. Genomic copy numbers of LINC01133 were increased in HCC, which were positively related with the elevated expression of LINC01133. Increased copy number of LINC01133 predicted the poor prognosis in HCC patients. LINC01133 overexpression in HCC cells promoted proliferation and aggressive phenotypes in vitro, and facilitated tumor growth and lung metastasis in vivo, whereas LINC01133 knockdown had the opposite effects. LINC01133 sponged miR-199a-5p, resulting in enhanced expression of SNAI1, which induced epithelial-to-mesenchymal transition (EMT) in HCC cells. In addition, LINC01133 interacted with Annexin A2 (ANXA2) to activate the ANXA2/STAT3 signaling pathway. LINC01133 promotes HCC progression by sponging miR-199a-5p and interacting with ANXA2. LINC01133 CNV gain is predictive of poor prognosis in patients with HCC.