Common and distinct features of mammary tumors driven by Pten-deletion or activating Pik3ca mutation

Modulation of Genes and MicroRNAs in the Neurospheres of Glioblastoma Cell Lines U343 and T98G Induced by Ionizing Radiation and Temozolomide Therapy

INTRODUCTION

Glioblastoma is the most prevalent primary malignant neoplasm of the central nervous system. It has increased its incidence, while the overall survival remains over 14 months.

PURPOSE

The purpose is to evaluate the expression of the genes EGFR, PTEN, MGMT, and IDH1/2, and microRNAs miR-181b, miR-145, miR-149, and miR-128a in adhered cells (AC) and neurospheres (NS) from cell lines (T98G and U343) submitted to temozolomide (TMZ) and ionizing radiation (IR).

METHODS

T98G and U343 were treated with TMZ, IR, and TMZ+IR. The analysis of gene expression and miRNAs was performed using real-time PCR.

RESULTS

This study demonstrated: a) an improvement in the expression of IDH1 after IR and TMZ + IR in the NS (T98G); b) an increase in the expression of MGMT in NS (T98G) in IR groups and TMZ + IR. The expression of miRNAs results as a) AC (U343) expressed more miR-181b after TMZ, IR, and TMZ + IR; and miR-128a improved after TMZ, IR, and TMZ + IR; b) NS (T98G) after TMZ + IR expressed: miR-181b; miR-149; miR-145 and miR-128a; c) NS (U343) after IR huge expressed miR-149 and miR-145.

CONCLUSION

IR was an independent and determining radioresistance factor in NS. However, we observed no complementarity action of oncomiRs regulation.

Low expression of PTEN is essential for maintenance of a malignant state in human gastric adenocarcinoma via upregulation of p‑AURKA mediated by activation of AURKA

Gastric adenocarcinoma remains a life‑threatening disease, emphasizing the importance of gaining an improved understanding of signaling pathways involved in this disease, which can lead to the development of novel therapeutic methods targeting common molecular pathways shared across different types of gastric adenocarcinoma. The present study revealed phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and aurora kinase A (AURKA) gene alterations, which were involved in changes in the phenotypes of gastric cancer cells, including increased proliferation by cell counting kit‑8 assay and invasion capacity by Transwell invasion assay, and predicted survival rates by KM Plotter database in gastric cancer. The present study investigated the association between PTEN and AURKA. Western blotting revealed that phosphorylated (p)-AURKA correlated with two target genes, PTEN and AURKA. The downregulation of PTEN by small interfering (si)RNA not only increased the expression of AURKA at the mRNA and protein levels by western blotting and by reverse transcription‑quantitative PCR, but also increased the expression of p‑AURKA by western blotting and immunofluorescence analysis. In addition, western blotting and reverse transcription‑quantitative PCR revealed that the downregulation of AURKA affected the expression level of PTEN. Furthermore, PTEN suppressed the malignant phenotypic changes of gastric adenocarcinoma cells by regulating the expression of AURKA inhibited by p‑AURKA, suggesting that p‑AURKA may be the key mediator of the PTEN‑associated activation of AURKA and may be key in maintaining the PTEN‑induced malignant state of gastric adenocarcinoma cells. This hypothesis was confirmed by western blotting, and changes were observed in the protein expression of p‑AURKA and AURKA under conditions in which cells were treated with either MLN8237 or si‑PTEN transfection only, or with si‑PTEN transfection and MLN8237. Knockdown of the expression of PTEN altered the expression of p‑AKT, p‑glycogen synthase kinase 3β and β‑catenin, which are genes that have been reported to be involved in the development of gastric adenocarcinoma. The present study confirmed that p‑AURKA is important in the development of gastric adenocarcinoma and revealed a novel functional link between PTEN, AURKA and p‑AURKA activation. The results also suggest a novel drug design strategy in targeting PTEN and AURKA for more specific gastric cancer cell death that spares normal cells.

Geridonin and paclitaxel act synergistically to inhibit the proliferation of gastric cancer cells through ROS-mediated regulation of the PTEN/PI3K/Akt pathway

Paclitaxel, a taxane, is a cytotoxic chemotherapeutic agent that targets microtubules. It has become a front-line therapy for a broad range of malignancies, including lung, breast, gastric, esophageal, and bladder carcinomas. Although paclitaxel can inhibit tumor development and improve survival, poor solubility, myelotoxicity, allergic reactions, and drug resistance have restricted its clinical application. Paclitaxel is frequently combined with other chemotherapeutics to enhance the antitumor effects and reduce side effects. We synthesized geridonin, a derivative of oridonin, and demonstrate that geridonin and paclitaxel act synergistically to inhibit the growth of gastric cancer cells. Importantly, geridonin enhanced the antitumor effects of paclitaxel without increasing toxicity in vivo. Mechanistic analysis revealed that administration of geridonin in combination with paclitaxel up-regulated the tumor suppressor PTEN and inhibited phosphorylation of Akt and MDM2. This led to the accumulation of p53 and induced apoptosis though the mitochondrial pathway. Thus, geridonin in combination with paclitaxel is a new treatment strategy for gastric cancer.

Inhibition of COX-2 and 5-LOX regulates the progression of colorectal cancer by promoting PTEN and suppressing PI3K/AKT pathway

For colorectal cancer (CRC) patients, local and systemic inflammatory responses have been extensively reported to closely associate with patient survival. However, the specific signaling pathways responsible for carcinogenic responses are unclear. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a negative regulator of PI3K/AKT pathway that is gradually inactivated in cancers through mutation, loss of heterozygosity and others epigenetic mechanisms. In addition, COX and LOX metabolic pathways of arachidonic acid (AA) play a crucial role in promoting adenoma development. The aim of this study is to clarify the relationship of COX, LOX and PTEN/PI3K/AKT pathway. Results showed that the over-expressed COX and LOX in cancer cells can be targeted to decrease the expression of PTEN. After using corresponding inhibitors, this condition was significantly improved and promoted apoptosis, inhibited invasion, proliferation and the production of reactive oxygen species. And for COX-2-/- or 5-LOX-/- Apc^Min/+ mice, the PI3K/AKT pathway was further inhibited via promoting PTEN. Furthermore, weakened oxidative stress, inhibited adenoma growth, and improved survival rate. All findings indicated that PTEN was indirectly targeted by these enzyme inhibitors and acted as the potential therapeutic target for colorectal cancer therapy. In short, COX-2 or 5-LOX deletion and its inhibitors enhanced activity of PTEN and suppressed cell and adenoma progression through PI3K/AKT pathway in colorectal cancer.

Apoptosis induced by the methanol extract of Salvia miltiorrhiza Bunge in non-small cell lung cancer through PTEN-mediated inhibition of PI3K/Akt pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Salvia miltiorrhiza Bunge, a well-known traditional Chinese medicinal (TCM) plant, has been used to treat cardiovascular diseases since thousands of years. Many studies reported that the active component tanshinones displayed a variety of biological activities: anti-thrombous, anti-allergic, anti-inflammatory, antioxidant and anti-tumor promoting. But the mechanism of how the active components working still need to be clarified. The anti-tumor effect of compounds of tanshinone (CTN), the methanol extract of Salvia miltiorrhiza Bunge roots, was investigated. The aim of this study was to investigate the effects of CTN on the growth inhibition, apoptosis and molecular targets of human non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

CTN-induced cytotoxicity was determined by MTT assay. The cell survival was evaluated using clonogenic survival assay. The morphology of Glc-82 cells after treatment with CTN was determined by fluorescence microscopy. Cell cycle distribution was revealed by flow cytometry. The apoptotic cells were quantified with annexin V-FITC/PI staining and flow cytometry, and observed using Hoechst 33258 staining and TUNEL assays. The expression levels of proteins were analyzed using western blot. Tumor growth was assessed by subcutaneous inoculation of cells into BALB/c nude mice.

RESULTS

CTN inhibited the proliferation of NSCLC in a dose-dependent manner and induced both early and late apoptosis. Treatment of Glc-82 cells with CTN (5-80μg/ml) significantly (p<0.05) suppressed the cell proliferation in a concentration and time-dependent manner. CTN induced significant (p<0.05) and dose-dependent apoptosis of Glc-82 cells. Cell cycle assay showed that CTN induced a G₂/M phase arrest, and significantly (p<0.05) increased expression of p53 and p21, actived caspase-3/9 and PARP1, which suggest the involvement of the mitochondria in the apoptotic signals. In addition, CTN decreased expression of the anti-apoptotic protein Bcl-2, Bcl-xl and increased expression of the pro-apoptotic protein Bax. Result also showed that CTN could increase expression levels of PTEN, and reduce the phosphorylated levels of Akt (protein kinase B) on Thr 308 and Ser 473 domain. In vivo assay showed that the antitumor effect of CTN was significantly augmented without increasing toxicity in nude mice bearing Glc-82 xenograft.

CONCLUSION

The PTEN/Akt signaling axis is defined as a critical pathway regulated by PTEN in NSCLC. CTN, the methanol extract of Salvia miltiorrhiza Bunge, are the active compounds as shown by their ability to induce apoptosis through the mitochondrial pathway of apoptosis and PTEN-mediated inhibition of PI3K/Akt pathway. CTN could inhibit tumor growth more efficiently, which supports the ethno-medicinal use of this herb as an alternative or complementary therapy for NSCLC.

PTEN expression as a predictor for the response to trastuzumab-based therapy in Her-2 overexpressing metastatic breast cancer

Background

Even though trastuzumab is an effective therapy in early stage Her-2+ breast cancer, 40–50% of advanced Her-2+ breast cancer patients develop trastuzumab resistance. A potential resistance mechanism is aberrant downstream signal transmission due to loss of phosphatase and tensin homologue (PTEN). This study investigated the relationship between the expression of PTEN and trastuzumab response in Her-2 overexpressing metastatic breast cancer patients.

Methods

Between 2000 and 2007, 164 patients with Her-2+ metastatic breast cancer received trastuzumab-based therapy in our institution. We analyzed PTEN status by immunohistochemistry of 115 available tumor tissues and analyzed associations with other histopathological parameters, response rate, progression free survival (PFS) and overall survival (OS) with a median follow-up of 60 months.

Results

Eighty patients were PTEN positive (69.6%) and 35 patients PTEN negative (30.4%). We found a significant association of the expression of PTEN and p53 (p = 0.041), while there was no association with grading, hormone receptor status, IGFR or MIB. We found significantly more cases with progressive disease under trastuzumab-based therapy in patients with PTEN positive breast cancers (p = 0.018), while there was no significant correlation with PFS or OS.

Conclusion

In Her-2-positive metastatic breast cancers, PTEN positivity was significantly associated with progressive disease, but not with PFS or OS.

Phosphoproteomic comparison of Pik3ca and Pten signalling identifies the nucleotidase NT5C as a novel AKT substrate

To identify novel effectors and processes regulated by PI3K pathway activation, we performed an unbiased phosphoproteomic screen comparing two common events of PI3K deregulation in cancer: oncogenic Pik3ca mutation (Pik3caH1047R) and deletion of Pten. Using mouse embryonic fibroblast (MEF) models that generate inducible, low-level pathway activation as observed in cancer, we quantified 7566 unique phosphopeptides from 3279 proteins. A number of proteins were found to be differentially-regulated by Pik3caH1047R and Pten loss, suggesting unique roles for these two events in processes such as vesicular trafficking, DNA damage repair and RNA splicing. We also identified novel PI3K effectors that were commonly-regulated, including putative AKT substrates. Validation of one of these hits, confirmed NT5C (5',3'-Nucleotidase, Cytosolic) as a novel AKT substrate, with an unexpected role in actin cytoskeleton regulation via an interaction with the ARP2/3 complex. This study has produced a comprehensive data resource and identified a new link between PI3K pathway activation and actin regulation.

RB1 deficiency in triple-negative breast cancer induces mitochondrial protein translation

Triple-negative breast cancer (TNBC) includes basal-like and claudin-low subtypes for which no specific treatment is currently available. Although the retinoblastoma tumor-suppressor gene (RB1) is frequently lost together with TP53 in TNBC, it is not directly targetable. There is thus great interest in identifying vulnerabilities downstream of RB1 that can be therapeutically exploited. Here, we determined that combined inactivation of murine Rb and p53 in diverse mammary epithelial cells induced claudin-low-like TNBC with Met, Birc2/3-Mmp13-Yap1, and Pvt1-Myc amplifications. Gene set enrichment analysis revealed that Rb/p53-deficient tumors showed elevated expression of the mitochondrial protein translation (MPT) gene pathway relative to tumors harboring p53 deletion alone. Accordingly, bioinformatic, functional, and biochemical analyses showed that RB1-E2F complexes bind to MPT gene promoters to regulate transcription and control MPT. Additionally, a screen of US Food and Drug Administration-approved (FDA-approved) drugs identified the MPT antagonist tigecycline (TIG) as a potent inhibitor of Rb/p53-deficient tumor cell proliferation. TIG preferentially suppressed RB1-deficient TNBC cell proliferation, targeted both the bulk and cancer stem cell fraction, and strongly attenuated xenograft growth. It also cooperated with sulfasalazine, an FDA-approved inhibitor of cystine xCT antiporter, in culture and xenograft assays. Our results suggest that RB1 deficiency promotes cancer cell proliferation in part by enhancing mitochondrial function and identify TIG as a clinically approved drug for RB1-deficient TNBC.