Role of regulatory miRNAs of the PI3K/AKT/mTOR signaling in the pathogenesis of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the common malignant human tumors with high morbidity worldwide. Aberrant activation of the oncogenic phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) signaling is related to clinicopathological features of HCC. Emerging data revealed that microRNAs (miRNAs) have prominent implications for regulating cellular proliferation, differentiation, apoptosis, and metabolism through targeting the PI3K/AKT/mTOR signaling axis. The recognition of the crucial role of miRNAs in hepatocarcinogenesis represents a promising area to identify novel anticancer therapeutics for HCC. The present study summarizes the major findings about the regulatory role of miRNAs in the PI3K/AKT/mTOR pathway in the pathogenesis of HCC.     

LINC01133 aggravates the progression of hepatocellular carcinoma by activating the PI3K/AKT pathway

LncRNAs exhibit crucial roles in various pathological diseases, including hepatocellular carcinoma (HCC). Therefore, it is significant to recognize the dysregulated lncRNAs in HCC progression. Recently, LINC01133 has been identified in several tumors. However, the biological role of LINC01133 in HCC remains poorly understood. Currently, we focused on the function of LINC01133 in HCC development. We observed that LINC01133 was significantly increased in HCC cells including HepG2, Hep3B, MHCC-97L, SK-Hep-1, and MHCC-97H cells compared with the normal human liver cell line HL-7702. In addition, PI3K/AKT signaling was highly activated in HCC cells. Knockdown of LINC01133 was able to inhibit HCC cell proliferation, cell colony formation, cell apoptosis, and blocked cell cycle arrest in the G1 phase. For another, downregulation of LINC01133 repressed HCC cell migration and invasion. Subsequently, the PI3K/AKT signaling pathway was strongly suppressed by silence of LINC01133 in Hep3B and HepG2 cells. Then, in vivo tumor xenografts models were established using Hep3B cells to explore the function of LINC01133 in HCC progression. Consistently, our study indicated that knockdown of LINC01133 dramatically repressed HCC tumor progression through targeting the PI3K/AKT pathway in vivo. Taken these together, we revealed that LINC01133 contributed to HCC progression by activating the PI3K/AKT pathway.     

FUT family mediates the multidrug resistance of human hepatocellular carcinoma via the PI3K/Akt signaling pathway

The fucosyltransferase (FUT) family is the key enzymes in cell-surface antigen synthesis during various biological processes such as tumor multidrug resistance (MDR). The aim of this work was to analyze the alteration of FUTs involved in MDR in human hepatocellular carcinoma (HCC) cell lines. Using mass spectrometry (MS) analysis, the composition profiling of fucosylated N-glycans differed between drug-resistant BEL7402/5-FU (BEL/FU) cells and the sensitive line BEL7402. Further analysis of the expressional profiles of the FUT family in three pairs of parental and chemoresistant human HCC cell lines showed that FUT4, FUT6 and FUT8 were predominant expressed in MDR cell lines. The altered levels of FUT4, FUT6 and FUT8 were responsible for changed drug-resistant phenotypes of BEL7402 and BEL/FU cells both in vitro and in vivo. In addition, regulating FUT4, FUT6 or FUT8 expression markedly modulated the activity of the phosphoinositide 3 kinase (PI3K)/Akt signaling pathway and MDR-related protein 1 (MRP1) expression. Inhibition of the PI3K/Akt pathway by its specific inhibitor wortmannin, or by Akt small interfering RNA (siRNA), resulted in decreased MDR of BEL/FU cells, partly through the downregulation of MRP1. Taken together, our results suggest that FUT4-, FUT6- or FUT8-mediated MDR in human HCC is associated with the activation of the PI3K/Akt pathway and the expression of MRP1, but not of P-gp, indicating a possible novel mechanism by which the FUT family regulates MDR in human HCC.     

PI3K和Akt蛋白在异丙肾上腺素所致大鼠心肌肥厚中的表达

目的研究异丙肾上腺素(ISO)致大鼠心肌肥厚中PI3K和Akt在心肌组织中的表达,为探讨心肌肥厚的信号转导机制和逆转心肌肥厚提供形态学资料.方法健康成年SD大鼠20只,随机分为实验组、对照组,每组10只.实验组给予异丙肾上腺素处理.1周后处死大鼠,取心肌组织,常规石蜡切片,HE染色,观察心肌组织的病理变化,测量心肌肥厚指标;免疫组织化学染色和免疫荧光染色,检测p-PI3K和p-Akt的表达及分布.结果实验组大鼠心肌肥厚指标与对照组相比均明显升高;免疫组织化学检测显示,实验组心肌组织p-PI3K和p-Akt蛋白表达面积和平均光密度较对照组高.免疫荧光检测实验组心肌组织p-PI3K和p-Akt蛋白表达较对照组高.结论小剂量持续给予 ISO 能建立大鼠心肌肥厚模型;p-PI3K和p-Akt蛋白表达均与心肌肥厚的发生和发展过程相关,PI3K/Akt信号通路激活,可能是导致心肌肥厚的机制之一.     

PI3K 抑制剂抗肿瘤临床研究进展

磷脂酰肌醇-3-激酶 (PI3K) 是一种胞内磷脂酰肌醇激酶,在介导细胞生长、发育、分裂、分化和凋亡等过程中发挥重要作用,因此 PI3K 抑制剂的开发已成为当前抗癌新药研究的热点之一。目前已有多个 PI3K 抑制剂进入临床研究阶段或已上市,其单用或与其他药物联 用的疗效和安全性有待进一步临床验证。综述 PI3K 抑制剂作为抗肿瘤药物的临床研究进展,为其进一步研究与应用提供参考。     

Discovery of benzenesulfonamide derivatives as potent PI3K/mTOR dual inhibitors with in vivo efficacies against hepatocellular carcinoma

The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway is related to cellular activities. Abnormalities of this signaling pathway were discovered in various cancers, including hepatocellular carcinoma (HCC). The PI3K/mTOR dual inhibitors were proposed to have enhanced antitumor efficacies by targeting multiple points of the signaling pathway. We synthesized a series of propynyl-substituted benzenesulfonamide derivatives as PI3K/mTOR dual inhibitors. Compound 7k (NSC781406) was identified as a highly potent dual inhibitor, which exhibited potent tumor growth inhibition in the hepatocellular carcinoma BEL-7404 xenograft model. Compound 7k may be a potential therapeutic drug candidate for HCC.     

PI3K-PKB-mTOR hyperactivation in relation to nasopharyngeal carcinoma progression and prognosis

Nasopharyngeal carcinoma (NPC) has a unique and complex etiology, which is not completely understood. The aim of this study is to investigate the expression patterns of phosphatidylinositol 3-kinase (PI3K), protein kinase B (PKB), and mammalian target of rapamycin (mTOR) proteins in patients with NPC and their relationship with NPC progression and prognosis. Between January 2008 and March 2010, PI3K, PKB, and mTOR protein expressions were detected using immunohistochemistry among 119 patients with NPC and 30 healthy people. A 5-year follow-up was conducted for all patients. Correlations of PI3K, PKB, and mTOR proteins with the clinicopathological features and prognosis of NPC were evaluated using Spearman's rank correlation coefficient and Kaplan-Meier curve. Cox's regression analysis was performed to analyze the risk factors for the prognosis of NPC. First, PI3K, PKB, and mTOR were highly expressed in patients with NPC. The expressions of PI3K, PKB, and mTOR proteins were associated with T stage, N stage, clinical stage, relapse, and distant metastasis. Meanwhile, PI3K is positively correlated with PKB and PKB is positively correlated with mTOR in NPC. Higher PI3K, PKB, and mTOR protein expressions were related to a shorter survival time and a lower survival rate in NPC. Cox regression analysis revealed that age, T stage, N stage, PI3K, PKB, and mTOR were independent risk factors for NPC patient survival. Altogether, our data suggest that overexpression of PI3K, PKB, and mTOR proteins is an important indicator of poor survival in NPC. In addition, inhibition of PI3K-PKB-mTOR signaling may also contribute to the development of new therapeutic strategies for NPC.     

DMBT1 suppresses progression of gallbladder carcinoma through PI3K/AKT signaling pathway by targeting PTEN

ABSTRACT

Gallbladder carcinoma (GBC) is a highly lethal malignancy of the gastrointestinal tract. Despite extensive research, the underlying molecular mechanism of GBC remains largely unclear. Deleted in malignant brain tumors 1 (DMBT1) is low-expression during cancer progression and as a potential tumor-suppressor gene in various types of cancer. However, its role in Gallbladder cancer remains poorly understood. Here, we found that DMBT1 was significantly low-expression and deletion of copy number in GBC tissues by qRT-PCR and Western blot. Overexpression of DMBT1 impaired survival, promoted apoptosis in GBC cells in vitro, and inhibited tumor progression in vivo. Further study of underlying mechanisms demonstrated that DMBT1 combined with PTEN which could stabilize PTEN protein, resulting in inhibiting the activation of PI3K/AKT signaling pathway. Our study revealed a new sight of DMBT1 as a tumor-suppressor gene on the PI3K/AKT pathway in GBC, which may be a potential therapeutic target for improving treatment.     

Effects of PI3K catalytic subunit and Akt isoform deficiency on mTOR and p70S6K activation in myoblasts

The PI3K/Akt/mTOR signaling pathway is critical for cellular growth and survival in skeletal muscle, and is activated in response to growth factors such as insulin-like growth factor-I (IGF-I). We found that in C2C12 myoblasts, deficiency of PI3K p110 catalytic subunits or Akt isoforms had distinct effects on phosphorylation of mTOR and p70S6K. siRNA-mediated knockdown of PI3K p110α, p110β, and simultaneous knockdown of p110α and p110β resulted in increased basal and IGF-I-stimulated phosphorylation of mTOR S2448 and p70S6K T389; however, phosphorylation of S6 was reduced in p110β-deficient cells, possibly due to reductions in total S6 protein. We found that IGF-I-stimulated Akt1 activity was enhanced in Akt2- or Akt3-deficient cells, and that knockdown of individual Akt isoforms increased mTOR/p70S6K activation in an isoform-specific fashion. Conversely, levels of IGF-I-stimulated p70S6K phosphorylation in cells simultaneously deficient in both Akt1 and Akt3 were increased beyond those seen with loss of any single Akt isoform, suggesting an alternate, Akt-independent mechanism that activates mTOR/p70S6K. Our results collectively suggest that mTOR/p70S6K is activated in a PI3K/Akt-dependent manner, but that in the absence of p110α or Akt, alternate pathway(s) may mediate activation of mTOR/p70S6K in C2C12 myoblasts.     

MiR-27a-3p enhances the cisplatin sensitivity in hepatocellular carcinoma cells through inhibiting PI3K/Akt pathway

MicroRNAs (miRNAs) play an important role in drug resistance, and it is reported that miR-27a-3p regulated the sensitivity of cisplatin in breast cancer, lung cancer and ovarian cancer. However, the relationship between miR-27a-3p and chemosensitivity of cisplatin in hepatocellular carcinoma (HCC) was unclear, especially the underlying mechanism was unknown. In the present study, we analyzed miR-27a-3p expression levels in 372 tumor tissues and 49 adjacent tissues in HCC samples from TCGA database, and found that the miR-27a-3p was down-regulated in HCC tissues. The level of miR-27a-3p was associated with metastasis, Child–Pugh grade and race. MiR-27a-3p was regarded as a favorable prognosis indicator for HCC patients. Then, miR-27a-3p was overexpressed in HepG2 cell, and was knocked down in PLC cell. Next, we conducted a series of in vitro assays, including MTT, apoptosis and cell cycle assays to observe the biological changes. Further, inhibitor rate and apoptosis rate were detected with pre- and post-cisplatin treatment in HCC. The results showed that overexpression of miR-27a-3p repressed the cell viability, promoted apoptosis and increased the percentage of cells in G₀/G₁ phase. Importantly, overexpression of miR-27a-3p significantly increased the inhibitor rate and apoptosis rate with cisplatin intervention. Besides, we found that miR-27a-3p added cisplatin sensitivity potentially through regulating PI3K/Akt signaling pathway. Taken together, miR-27a-3p acted as a tumor suppressor gene in HCC cells, and it could be useful for modulating cisplatin sensitivity in chemotherapy.     

CircPUM1 promotes hepatocellular carcinoma progression through the miR-1208/MAP3K2 axis

Hepatocellular carcinoma (HCC) is a common disease with a significant mortality, and there is no effective treatment for advanced patients. Growing evidence indicates that circRNAs are closely related to HCC progression, may be used as biomarkers and targets for the diagnosis and treatment of HCC. Recent researches have shown that circPUM1 may play an oncogene role in a variety of human cancers, but its role in HCC development has not been reported. Our study found that circPUM1 could promote the proliferation, migration and invasion of HCC cells in vitro. In addition, in vivo studies showed that circPUM1 could increase the development of HCC tumours and regulate the expression of EMT-related proteins. Furthermore, we demonstrated that circPUM1 could promote the development of HCC by up-regulating the expression of MAP3K2 via sponging miR-1208. Our study suggested that circPUM1 may be a potential therapeutic target for HCC.     

The gene dosage of class Ia PI3K dictates the development of PTEN hamartoma tumor syndrome

The PTEN hamartoma tumor syndrome (PHTS) is a complex disorder caused by germline inactivating mutations of the tumor suppressor gene PTEN. Loss of PTEN function leads to unimpeded phosphatidylinositol-3′-kinase (PI3K) activity and PI3K-driven cell division. Individuals with PHTS develop benign hamartomas in various tissues and have an increased risk of developing malignant diseases. Notably, no effective therapy currently exists for this disorder. Using both genetic mouse models and pharmacological approaches, we recently demonstrated that PI3K p110α and p110β isoforms play spatially distinct but concerted roles in the skin that are required for the development and maintenance of PHTS. We also show that treatment with a pan-PI3K inhibitor prevents the development of skin PHTS and reverses advanced-stage skin hamartomas in vivo. Here, we report that genetic ablation of only 3 out of 4 p110 alleles is sufficient to block the development of skin hamartomas resulting from the complete loss of Pten in mice. Similar to our findings in skin, we now also show that mammary gland neoplastic lesions can be prevented or reversed upon PI3K inhibition in our PHTS mouse model. Our data suggest a possible route to chemoprevention using reduced doses of PI3K inhibitors for PTEN-deficient carrier patients.     

Inhibition of glycolytic metabolism in glioblastoma cells by Pt3glc combinated with PI3K inhibitor via SIRT3-mediated mitochondrial and PI3K/Akt–MAPK pathway

Glioblastoma multiforme (GBM) is the most malignant and aggressive glioma with abnormal expression of genes that mediate glycolytic metabolism and tumor cell growth. Petunidin-3-O-glucoside (Pt3glc) is a kind of anthocyanin in the red grape and derived beverages, representing the most common naturally occurring anthocyanins with a reduced incidence of cancer and heart diseases. In this study, whether Pt3glc could effectively regulate glycolysis to inhibit GBM cell was investigated by using the DBTRG-05MG cell lines. Notably, Pt3glc displayed potent antiproliferative activity and significantly changed the protein levels related to both glycolytic metabolism and GBM cell survival. The expression of the proapoptotic protein Bcl-2-associated X protein was increased with concomitant reduction on the levels of the antiapoptotic protein B-cell lymphoma 2 and caspase-3 activity. Furthermore, the levels of survival signaling proteins, such as protein kinase B (Akt) and phospho-Akt (Scr473), extracellular signal-regulated kinase (ERK) and phospho-ERK, were significantly decreased by Pt3glc in combination with the phosphoinositide 3-kinase (PI3K) inhibitor of LY294002. Most importantly, the levels of Sirtuin 3 (SIRT3) and phosphorylated p53 were also downregulated, indicating that Pt3glc combinated with PI3K inhibitor could induce GBM cell death may act via the SIRT3/p53-mediated mitochondrial and PI3K/Akt-ERK pathways. Our findings thus provide rational evidence that the combination of Pt3glc with PI3K inhibitor, which target alternative pathways in GBM cells, may be a useful adjuvant therapy in glioblastoma treatment.     

PI3K inhibition potentiates Bcl‐2‐dependent apoptosis in renal carcinoma cells

Inhibitors of PI3‐K/Akt are currently being assessed clinically in patients with advanced RCC. Identification of therapeutic strategies that might enhance the efficacy of PI3‐K/Akt inhibitors is therefore of great interest. As PI3‐K inhibition would be expected to have many pro‐apoptotic effects, we hypothesized that there may be unique synergy between PI3‐K inhibitors and BH3‐mimetics. Towards this end, we assessed the combination of the PI3K inhibitor LY 294002 and the Bcl‐2 family inhibitor ABT‐737 in RCC cell lines. We found that the combinatorial treatment with these agents led to a significant increase in PARP cleavage and cell death in all RCC cell lines. The synergized cell death was correlated with decreased levels of Mcl‐1 and XIAP, and increased levels in Bim, and appears critically dependent upon the activation of caspase 3 and 8. The enhanced lethality observed with the combination also appears dependent upon the regulation of XIAP, Mcl‐1 and Bim levels. Our results suggest that the combination of PI3‐K inhibitors with BH3‐mimetics may be a viable therapeutic strategy in RCC.     

Discovery and biological activity of a novel class I PI3K inhibitor, CH5132799

Phosphatidylinositol 3-kinase (PI3K) is a lipid kinase and a promising therapeutic target for cancer. Using structure-based drug design (SBDD), we have identified novel PI3K inhibitors with a dihydropyrrolopyrimidine skeleton. Metabolic stability of the first lead series was drastically improved by replacing phenol with aminopyrimidine moiety. CH5132799, a novel class I PI3K inhibitor, exhibited a strong inhibitory activity especially against PI3Kα (IC₅₀ = 0.014 μM). In human tumor cell lines with PI3K pathway activation, CH5132799 showed potent antiproliferative activity. CH5132799 is orally available and showed significant antitumor activity in PI3K pathway-activated human cancer xenograft models in mice.     

Phosphorylation and changes in the distribution of nucleolin promote tumor metastasis via the PI3K/Akt pathway in colorectal carcinoma

Here, we investigated the molecular mechanism underlying the changes in the distribution of nucleolin. Our study identified PI3K/Akt signaling as an essential pathway regulating the distribution of nucleolin. Furthermore, nucleolin can interact with phospho-PI3K-p55, and changes in the distribution of nucleolin were related to its phosphorylation. Subsequently, we analyzed the correlation of VEGF and nucleolin, and found that distribution of nucleolin related to metastatic potential. Finally, blocking cell surface nucleolin influences the process of epithelial–mesenchymal transitions. This indicates that nucleolin may be a novel cancer therapy target and a predictive marker for tumor migration in colorectal carcinoma.