Studies on the expression patterns of class I PI3K catalytic subunits and its prognostic significance in colorectal cancer

PI3K-alpha translocation mediates nuclear PtdIns(3,4,5)P3 effector signaling in colorectal cancer

The canonical view of phosphatidylinositol 3-kinase alpha (PI3Kα) signaling describes PtdIns(3,4,5)P₃ generation and activation of downstream effectors at the plasma membrane or at microtubule-bound endosomes. Here, we show that colorectal cancer (CRC) cell lines exhibit a diverse plasma membrane-nuclear distribution of PI3Kα, controlling corresponding levels of subcellular PtdIns(3,4,5)P₃ pools. PI3Kα nuclear translocation was mediated by the importin β-dependent nuclear import pathway. By PtdIns(3,4,5)P₃ affinity capture mass spectrometry done in the presence of SDS on CRC cell lines with PI3Kα nuclear localization, we identified 867 potential nuclear PtdIns(3,4,5)P₃ effector proteins. Nuclear PtdIns(3,4,5)P₃ interactome proteins were characterized by non-canonical PtdIns(3,4,5)P₃ binding domains and showed overrepresentation for nuclear membrane, nucleolus and nuclear speckles. The nuclear PtdIns(3,4,5)P₃ interactome was enriched for proteins related to RNA metabolism, with splicing reporter assays and SC-35 foci staining suggesting a role of EGF-stimulated nuclear PI3Kα signaling in modulating pre-mRNA splicing. In patient tumors, nuclear p110α staining was associated with lower T stage and mucinous histology. These results indicate that PI3Kα translocation mediates nuclear PtdIns(3,4,5)P₃ effector signaling in human CRC, modulating signaling responses.

Malignant growth of arsenic-transformed cells depends on activated Akt induced by reactive oxygen species

Arsenic is an identified carcinogen for humans.In this study, chronic exposure of human hepatocyte L-02 to low-doses of inorganic arsenic caused cell malignant proliferation. Meanwhile, compared with normal L-02 cells, arsenic-transformed malignant cells, L-02-As displayed more ROS and significantly higher Cyclin D1 expression as well as aerobic glycolysis. Moreover, Akt activation is followed by the upregulation of Cyclin D1 and HK2 expression in L-02-As cells, since inhibition of Akt activity by Ly294002 attenuated the colony formation in soft agar and decreased the levels of Cyclin D1 and HK2. In addition, scavenging of ROS by NAC resulted in a decreased expression of phospho-Akt, HK2 and Cyclin D1, and attenuates the ability of anchorage-independent growth ofL-02-As cells, suggested that ROS mediated the Akt activation in L-02-As cells. In summary, our results demonstrated that ROS contributes to the malignant phenotype of arsenic-transformed human hepatocyte L-02-As via the activation of Akt pathway.

Antitumor potential of Hedyotis diffusa Willd: A systematic review of bioactive constituents and underlying molecular mechanisms

Cancer is a major cause of death in the world. Chemotherapy can extend the life of cancer patients to some extent, but the quality of life is reduced. Therefore, the quest for more efficient and less toxic medication strategies is still at the forefront of current research. Hedyotis diffusa Willd (HDW), a Chinese herb medicine, has received great attention in the past two decades and has been well documented in clinics for antitumor activity in a variety of human cancers. This review discussed a total of 58 different kinds of active antitumor components isolated from HDW, including iridoids, flavonoids, flavonol glycosides, anthraquinones, phenolic acids, and their derivatives, sterols, and volatile oils. Their antitumor activities include inhibition of tumor cell proliferation, induction of tumor cell apoptosis and tumor angiogenesis, regulation of the host immune response, anti-inflammatory and antioxidant, and protective autophagy. Besides, we provide up-to-date and systematic evidence for HDW antitumor activities and the possible underlying molecular mechanisms and reference for further development of novel drugs and dosage formulation in control of human cancers.

Biochemical significance of limonene and its metabolites: future prospects for designing and developing highly potent anticancer drugs

Monocyclic monoterpenes have been recognized as useful pharmacological ingredients due to their ability to treat numerous diseases. Limonene and perillyl alcohol as well as their metabolites (especially perillic acid and its methyl ester) possess bioactivities such as antitumor, antiviral, anti-inflammatory, and antibacterial agents. These therapeutic properties have been well documented. Based on the aforementioned biological properties of limonene and its metabolites, their structural modification and development into effective drugs could be rewarding. However, utilization of these monocyclic monoterpenes as scaffolds for the design and developments of more effective chemoprotective agents has not received the needed attention by medicinal scientists. Recently, some derivatives of limonene metabolites have been synthesized. Nonetheless, there have been no thorough studies on their pharmacokinetic and pharmacodynamic properties as well as their inhibition against isoprenylation enzymes. In this review, recent research progress in the biochemical significance of limonene and its metabolites was summarized with emphasis on their antitumor effects. Future prospects of these bioactive monoterpenes for drug design and development are also highlighted.

Hypoxia induces pulmonary arterial fibroblast proliferation, migration, differentiation and vascular remodeling via the PI3K/Akt/p70S6K signaling pathway

The present study was designed to examine whether hypoxia induces the proliferation, migration and differentiation of pulmonary arterial fibroblasts (PAFs) via the PI3K/Akt/p70S6K signaling pathway. PAFs were subjected to normoxia (21% O₂) or hypoxia (1% O₂). The proliferation, migration, differentiation and cellular p110α, p-Akt, and p-p70S6K expression levels of the PAFs were examined in vitro. In addition, rats were maintained under hypoxic conditions, and the right ventricular systolic pressure (RVSP), right ventricular hypertrophy index (RVHI) and right ventricular weight/body weight ratio (RV/BW) were examined. The expression levels of p110α, p-Akt, p70S6K, fibronectin and α-SMA in the rat pulmonary vessels were also examined. Hypoxia significantly elevated the proliferation, migration and differentiation of rat PAFs. It also strongly elevated the expression of p110α, p-Akt and p-p70S6K in PAFs in vitro. NVP-BEZ235 was revealed to significantly reduce the hypoxia-induced proliferation, migration and differentiation. In vivo experiments demonstrated that hypoxia significantly induced the elevation of RVSP, RVHI, RV/BW, medial thickening, adventitious thickening, and fibronectin and collagen deposition around pulmonary artery walls. The expression of p110α, p-Akt and p70S6K was evident in the pulmonary arteries of the hypoxic rats. NVP-BEZ235 significantly reduced the hypoxia-induced hypoxic pulmonary vascular remodeling, as well as fibronectin and collagen deposition in the pulmonary arteries. Therefore, hypoxia was demonstrated to induce the proliferation, migration and differentiation of PAFs and the hypoxic pulmonary vascular remodeling of rats via the PI3K/Akt/p70S6K signaling pathway.

Recent advances in the use of PI3K inhibitors for glioblastoma multiforme: current preclinical and clinical development

Glioblastoma multiforme (GBM) is the most common and aggressive malignant primary tumor in the central nervous system. One of the most widely used chemotherapeutic drugs for GBM is temozolomide, which is a DNA-alkylating agent and its efficacy is dependent on MGMT methylation status. Little progress in improving the prognosis of GBM patients has been made in the past ten years, urging the development of more effective molecular targeted therapies. Hyper-activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway is frequently found in a variety of cancers including GBM, and it plays a central role in the regulation of tumor cell survival, growth, motility, angiogenesis and metabolism. Numerous PI3K inhibitors including pan-PI3K, isoform-selective and dual PI3K/mammalian target of rapamycin (mTOR) inhibitors have exhibited favorable preclinical results and entered clinical trials in a range of hematologic malignancies and solid tumors. Furthermore, combination of inhibitors targeting PI3K and other related pathways may exert synergism on suppressing tumor growth and improving patients' prognosis. Currently, only a handful of PI3K inhibitors are in phase I/II clinical trials for GBM treatment. In this review, we focus on the importance of PI3K/Akt pathway in GBM, and summarize the current development of PI3K inhibitors alone or in combination with other inhibitors for GBM treatment from preclinical to clinical studies.

PIK3CA and PIK3CB silencing by RNAi reverse MDR and inhibit tumorigenic properties in human colorectal carcinoma

Colorectal carcinoma (CRC) is the second most common and frequent cause of cancer-related deaths for men and women in the world. PIK3CA and PIK3CB that reverse multidrug resistance (MDR) can serve as predictive and prognostic markers as well as therapeutic targets for CRC treatment. In the present study, we showed that PIK3CA and PIK3CB are upregulated in CRCs and positively correlated with MDR-1, LRP, and GST-π. Long-term monitoring of 316 CRC patients showed that PIK3CA and PIK3CB were associated with poor survival time as shown by Kaplan-Meier analysis. Furthermore, we found that the downregulation of PIK3CA and PIK3CB reversed MDR; inhibited the capability of proliferation, migration, and invasion of CRC cells; and slowed down the CRC tumor growth in nude mice. Consistent with clinical observations, PIK3CA and PIK3CB significantly increase multidrug resistance of CRC cells in vivo. Together, these results suggest that PIK3CA and PIK3CB may be used as potential therapeutic drug targets for colorectal cancer.

Phosphatidylinositol 3-kinase CB association with preoperative radiotherapy response in rectal adenocarcinoma

AIM: To examine the correlation of phosphatidylinositol 3-kinase (PIK3) CB expression with preoperative radiotherapy response in patients with stage II/III rectal adenocarcinoma.

METHODS: PIK3CB immunoexpression was retrospectively assessed in pretreatment biopsies from 208 patients with clinical stage II/III rectal adenocarcinoma, who underwent radical surgery after 30-Gy/10-fraction preoperative radiotherapy. The relation between PIK3CB expression and tumor regression grade, clinicopathological characteristics, and survival time was statistically analyzed. Western blotting and in vitro clonogenic formation assay were used to detect PIK3CB expression in four colorectal cancer cell lines (HCT116, HT29, LoVo, and LS174T) treated with 6-Gy ionizing radiation. Pharmacological assays were used to evaluate the therapeutic relevance of TGX-221 (a PIK3CB-specific inhibitor) in the four colorectal cancer cell lines.

RESULTS: Immunohistochemical staining indicated that PIK3CB was more abundant in rectal adenocarcinoma tissues with poor response to preoperative radiotherapy. High expression of PIK3CB was closely correlated with tumor height (P < 0.05), ypT stage (P < 0.05), and high-degree tumor regression grade (P < 0.001). High expression of PIK3CB was a potential prognostic factor for local recurrence-free survival (P < 0.05) and metastasis-free survival (P < 0.05). High expression of PIK3CB was also associated with poor therapeutic response and adverse outcomes in rectal adenocarcinoma patients treated with 30-Gy/10-fraction preoperative radiotherapy. In vitro, PIK3CB expression was upregulated in all four colorectal cancer cell lines concurrently treated with 6-Gy ionizing radiation, and the PIK3CB-specific inhibitor TGX-221 effectively inhibited the clonogenic formation of these four colorectal cancer cell lines.

CONCLUSION: PIK3CB is critically involved in response to preoperative radiotherapy and may serve as a novel target for therapeutic intervention.

[Abelson interactor 1 (Abi1) in colorectal cancer. From synaptic plasticity to tumor cell migration]

BACKGROUND

Invasion and metastatic dissemination of tumor cells defines the prognosis of patients with colorectal cancer (CRC). The Abelson interactor 1 (Abi1), a 65 kD substrate of the eponymous Abelson tyrosine kinase, interacts with phosphatidylinositol-3-kinase (PI3K) and heterogeneous nuclear ribonucleoprotein K (hnRNP K) and is a key regulator of cytoskeletal reorganization during synaptic maturation and cellular migration.

AIM

The aim of this study was the analysis of Abi1 expression patterns and to elucidate the role in cytoskeletal reorganization in colorectal carcinoma cells.

MATERIAL AND METHODS

The methods used in this study were immunohistochemistry; immunofluorescence microscopy; liposomal transfection and protein analysis by Western blotting.

RESULTS

The results showed that Abi1 is expressed at the invasive front of colorectal carcinomas and localizes to the leading edge of lamellipodia in cultured colorectal carcinoma cells. A phosphorylated isoform of Abi1 that stains positively in these microcompartments disappears after treatment with the tyrosine kinase inhibitor STI571 (Glivec®). The RNA interference (RNAi) approach knockdown of Abi1 as well as treatment with STI571 induce a shift in cellular morphology from broad lamellipodia-like to thin filopodia-like cellular protrusions.

DISCUSSION

The initial results support a central role for phosphorylated Abi1 in the formation of lamellipodia-like cellular protrusions as a prerequisite for cellular migration of colorectal carcinoma cells. As phosphorylation of Abi1 could be pharmaceutically targeted with STI571, this indicates a possible therapeutic option to prevent the gain of a metastatic phenotype in colorectal cancer. This possibility will be further evaluated in ongoing research.

Expression and clinicopathological significance of EED, SUZ12 and EZH2 mRNA in colorectal cancer

BACKGROUND AND OBJECTIVES

Enhancer of zeste 2 (EZH2), embryonic ectoderm development (EED), and suppressor of zeste 12 homolog (SUZ12), the key component of polycomb repressive complex 2, are of great importance in human cancer pathogenesis. This study was designed to investigate the clinical and prognostic significances of EZH2, EED and SUZ12 in colorectal cancer (CRC) patients.

METHODS

The expression of EZH2, EED and SUZ12 mRNA was evaluated in 82 primary CRC and paired non-cancerous mucosa samples by qRT-PCR.

RESULTS

We found that overall EZH2, EED and SUZ12 mRNA expression in the CRC tissues was significantly increased than in the non-cancerous tissue (p < 0.05). Increased EZH2, EED and SUZ12 mRNA expression was directly correlated with primary tumor size, regional lymph node metastases, distant metastasis and AJCC stage. Furthermore, CRC patients with higher level of EED, SUZ12 or EZH2 showed a worse disease-free survival (DFS) (p < 0.01). In multivariate analysis, the increased EZH2 expression may be a risk factor for the patients' 3-year DFS (HR 2.517; 95% CI 1.104, 5.736; p = 0.028). Furthermore, the k-means cluster analysis showed that high mRNA expression of EED, SUZ12 and EZH2 was significantly correlated with the aggressive clinical behavior and poor prognosis.

CONCLUSIONS

High expression of EED, SUZ12 and EZH2 might contribute to the CRC development/progression.

Induction of apoptosis by D-limonene is mediated by inactivation of Akt in LS174T human colon cancer cells

D-limonene is recognized as a potential chemotherapeutic agent, however, the details of this mechanism remain unclear. In this study, we investigated the effects of d-limonene on colon cancer cell viability and its potential mechanism of action in vitro. After 48 h of treatment, d-limonene suppressed the viability of LS174T cells in a dose-dependent manner and caused a dose-dependent apoptotic cell death. D-limonene activated caspase-3 and -9 and PARP cleavage in a dose-dependent manner. Moreover, an increase in Bax protein and cytosol cytochrome c from mitochondria and a decrease in bcl-2 protein were observed following treatment with d-limonene. In addition, d-limonene decreased the levels of p-Akt (Ser473), p-Akt (Thr308) and p-GSK-3β (Ser9), suggesting that d-limonene induced apoptosis via the mitochondrial death pathway and the suppression of the PI3K/Akt pathway.