Targeted RNA interference of phosphatidylinositol 3-kinase p110-beta induces apoptosis and proliferation arrest in endometrial carcinoma cells

A somatic mutation in PIK3CD unravels a novel candidate gene for lymphatic malformation

Background

Lymphatic malformations (LMs) are benign congenital malformations that stem from the abnormal development of the lymphatic vessels during early embryogenesis. Somatic PIK3CA gene mutations are conventional cause leading to LMs. Both macrocystic and microcystic LMs arise due to lymphatic endothelial cell-autonomous defects, depending on the time in development at which PIK3CA gene mutation occurs. Recent study finds a PIK3CA mutation in 79% of LMs. However, discovering new genetic events in this disease is crucial to identify the molecular mechanism of the pathogenesis and further develop new targeted therapies.

Results

Here, we initially performed whole-exome sequencing in six children with LMs to find a new causal gene. Somatic mutations in PIK3CA (c.1633G > A [p. E545K] and PIK3CD (c.1997T > C [p.L666P]) were discovered in two different individuals. In vitro functional studies were conducted to demonstrate the pathogenicity of the novel mutation c.1997T > C in PIK3CD. We found that L666P promoted the cell proliferation and migration of human umbilical vein endothelial cells (HUVECs) and induced hyperactivation of the mTOR pathway. These findings indicate that the PIK3CD mutation affects downstream signalling in endothelial cells, which may impair normal lymphangiogenesis.

Conclusions

This study reveals a novel candidate gene associated with the development of LMs, which is consistent with previous researches. These findings in our study may offer a novel gene target for developing therapies, which acts in tight interaction with the previously known PIK3CA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01782-9.

Nuclear upregulation of class I phosphoinositide 3-kinase p110β correlates with high 47S rRNA levels in cancer cells

The class I phosphoinositide 3-kinase (PI3K) catalytic subunits p110α and p110β are ubiquitously expressed but differently targeted in tumours. In cancer, PIK3CB (encoding p110β) is seldom mutated compared with PIK3CA (encoding p110α) but can contribute to tumorigenesis in certain PTEN-deficient tumours. The underlying molecular mechanisms are, however, unclear. We have previously reported that p110β is highly expressed in endometrial cancer (EC) cell lines and at the mRNA level in primary patient tumours. Here, we show that p110β protein levels are high in both the cytoplasmic and nuclear compartments in EC cells. Moreover, high nuclear:cytoplasmic staining ratios were detected in high-grade primary tumours. High levels of phosphatidylinositol (3,4,5)-trisphosphate [PtdIns(3,4,5)P ₃] were measured in the nucleus of EC cells, and pharmacological and genetic approaches showed that its production was partly dependent upon p110β activity. Using immunofluorescence staining, p110β and PtdIns(3,4,5)P ₃ were localised in the nucleolus, which correlated with high levels of 47S pre-rRNA. p110β inhibition led to a decrease in both 47S rRNA levels and cell proliferation. In conclusion, these results present a nucleolar role for p110β that may contribute to tumorigenesis in EC.This article has an associated First Person interview with Fatemeh Mazloumi Gavgani, joint first author of the paper.

Targeting Clusterin Induces Apoptosis, Reduces Growth Ability and Invasion and Mediates Sensitivity to Chemotherapy in Human Osteosarcoma Cells

Objective:

The aim of the study was to investigate the expression of sCLU in relation to the clinicopathological features and prognosis of patients with untreated High-Grade Osteosarcoma (HGOS) and to evaluate sCLU as a target for osteosarcoma (OS) therapies.

Methods:

The expression of sCLU in 98 patients of HGOS enrolled from April 2005 to March 2015 at the affiliated hospital of Qingdao University was evaluated by immunohistochemistry. The sCLU expression, clinical data and survival were compared. siRNA-mediated sCLU gene silencing on cell apoptosis, viability, invasion and chemosensitivity to doxorubicin in U2OS cells in vitro was evaluated.

Results:

sCLU expression was found in 59 (60%) of the 98 patients. A positive correlation was observed between sCLU expression and metastatic disease (P = 0.036) and a negative correlation between sCLU expression and response to chemotherapy (P = 0.002). Targeting sCLU expression in U2OS cells induced significant reduction in cellular growth and higher rates of spontaneous endogenous apoptosis. In addition, targeting sCLU expression inhibited the invasion of U2OS cells. Furthermore, targeting sCLU expression significantly sensitized to chemotherapeutic drug, doxorubicin.

Conclusions:

The overexpression of sCLU was significantly correlated with metastasis and chemosensitivity in patients with HGOS. sCLU may be a promising therapeutic or chemopreventive target for human OS treatment.

PI3Kβ-A Versatile Transducer for GPCR, RTK, and Small GTPase Signaling

The phosphoinositide 3-kinase (PI3K) family includes eight distinct catalytic subunits and seven regulatory subunits. Only two PI3Ks are directly regulated downstream from G protein-coupled receptors (GPCRs): the class I enzymes PI3Kβ and PI3Kγ. Both enzymes produce phosphatidylinositol 3,4,5-trisposphate in vivo and are regulated by both heterotrimeric G proteins and small GTPases from the Ras or Rho families. However, PI3Kβ is also regulated by direct interactions with receptor tyrosine kinases (RTKs) and their tyrosine phosphorylated substrates, and similar to the class II and III PI3Ks, it binds activated Rab5. The unusually complex regulation of PI3Kβ by small and trimeric G proteins and RTKs leads to a rich landscape of signaling responses at the cellular and organismic levels. This review focuses first on the regulation of PI3Kβ activity in vitro and in cells, and then summarizes the biology of PI3Kβ signaling in distinct tissues and in human disease.

PIK3CD induces cell growth and invasion by activating AKT/GSK-3β/β-catenin signaling in colorectal cancer

The catalytic subunit p110δ of phosphoinositide 3‐kinase (PI3K) encoded by PIK3CD has been implicated in some human solid tumors. However, its roles in colorectal cancer (CRC) remain largely unknown. Here we found that PIK3CD was overexpressed in colon cancer tissues and CRC cell lines and was an independent predictor for overall survival (OS) of patients with colon cancer. The ectopic overexpression of PIK3CD significantly promoted CRC cell growth, migration and invasion in vitro and tumor growth in vivo. In contrast, inhibition of PIK3CD by specific small‐interfering RNA or idelalisib dramatically suppressed CRC cell growth, migration and invasion in vitro and tumor growth in vivo. Moreover, PIK3CD overexpression increased AKT activity, nuclear translocation of β‐catenin and T‐cell factor/lymphoid enhancer factor (TCF/LEF) transcriptional activity and decreased glycogen synthase kinase 3β (GSK‐3β) activity, whereas PIK3CD inhibition exhibited the opposite effects. Furthermore, PIK3CD‐mediated cell growth, migration and invasion were reversed by blockade of AKT signaling or depletion of β‐catenin. In addition, PIK3CD expression in colon cancer tissues positively correlated with β‐catenin abnormal expression, which was an independent predictor for OS of colon cancer patients. Taken together, our findings demonstrate that PIK3CD is an independent prognostic factor in CRC and that PIK3CD induces CRC cell growth, migration and invasion by activating AKT/GSK‐3β/β‐catenin signaling, suggesting that PIK3CD might be a novel prognostic biomarker and a potential therapeutic target for CRC.

Impact of p85α Alterations in Cancer

The phosphatidylinositol 3-kinase (PI3K) pathway plays a central role in the regulation of cell signaling, proliferation, survival, migration and vesicle trafficking in normal cells and is frequently deregulated in many cancers. The p85α protein is the most characterized regulatory subunit of the class IA PI3Ks, best known for its regulation of the p110-PI3K catalytic subunit. In this review, we will discuss the impact of p85α mutations or alterations in expression levels on the proteins p85α is known to bind and regulate. We will focus on alterations within the N-terminal half of p85α that primarily regulate Rab5 and some members of the Rho-family of GTPases, as well as those that regulate PTEN (phosphatase and tensin homologue deleted on chromosome 10), the enzyme that directly counteracts PI3K signaling. We highlight recent data, mapping the interaction surfaces of the PTEN⁻p85α breakpoint cluster region homology (BH) domain, which sheds new light on key residues in both proteins. As a multifunctional protein that binds and regulates many different proteins, p85α mutations at different sites have different impacts in cancer and would necessarily require distinct treatment strategies to be effective.

Class I Phosphoinositide 3-Kinase PIK3CA/p110α and PIK3CB/p110β Isoforms in Endometrial Cancer

The phosphoinositide 3-kinase (PI3K) signalling pathway is highly dysregulated in cancer, leading to elevated PI3K signalling and altered cellular processes that contribute to tumour development. The pathway is normally orchestrated by class I PI3K enzymes and negatively regulated by the phosphatase and tensin homologue, PTEN. Endometrial carcinomas harbour frequent alterations in components of the pathway, including changes in gene copy number and mutations, in particular in the oncogene PIK3CA, the gene encoding the PI3K catalytic subunit p110α, and the tumour suppressor PTEN. PIK3CB, encoding the other ubiquitously expressed class I isoform p110β, is less frequently altered but the few mutations identified to date are oncogenic. This isoform has received more research interest in recent years, particularly since PTEN-deficient tumours were found to be reliant on p110β activity to sustain transformation. In this review, we describe the current understanding of the common and distinct biochemical properties of the p110α and p110β isoforms, summarise their mutations and highlight how they are targeted in clinical trials in endometrial cancer.

Endometrial cancer cells exhibit high expression of p110β and its selective inhibition induces variable responses on PI3K signaling, cell survival and proliferation

PTEN loss and constitutive activation of the class I phosphoinositide 3-kinase (PI3K) pathway are key drivers of endometrial tumorigenesis. In some cancer types, PTEN-deficient tumors are reliant on class I PI3K p110β (encoded by PIK3CB) activity but little is known about this contribution in endometrial tumorigenesis. In this study, we find that p110β is overexpressed in a panel of 7 endometrial cancer cell lines compared to non-transformed cells. Furthermore, in 234 clinically annotated patient samples, PIK3CB mRNA levels increase significantly in the early phase of tumorigenesis from precursors to low grade primary malignant lesions whereas PIK3CA levels are higher in non-endometrioid compared to endometrioid primary tumors. While high levels of either PIK3CA or PIK3CB associate with poor prognosis, only elevated PIK3CB mRNA levels correlate with a high cell cycle signature score in clinical samples. In cancer cell lines, p110α inhibition reduces cell viability by inducing cell death in PIK3CA mutant cells while p110β inhibition delayed proliferation in PTEN-deficient cells, but not in WT cells. Taken together, our findings suggest that PIK3CB/p110β contributes to some of the pleiotropic functions of PI3K in endometrial cancer, particularly in the early steps by contributing to cell proliferation.

TGX-221 inhibits proliferation and induces apoptosis in human glioblastoma cells

Glioblastoma is the most common type of primary brain tumor in adults, with high mortality and morbidity rates. More effective therapeutic strategies are imperative. Previous studies have shown that the known p110-β-selective inhibitor TGX-221 blocks the activation of PKB/Akt in PTEN-deficient cells. We treated U87 and U251 glioblastoma cells with TGX-221 to determine the effect of TGX-221. We performed a Cell Counting Kit-8 (CCK-8) test, EDU staining and cell cycle distribution analysis and found that TGX-221 inhibited glioblastoma cell proliferation. Next, the effect of TGX-221 on cell apoptosis was investigated using flow cytometry. These results demonstrated that TGX-221 induced apoptosis in glioblastoma cells. Moreover, migration and invasion assays revealed that TGX-221 inhibited human glioblastoma cell migration and invasion. Collectively, our study revealed that TGX-221 could inhibit proliferation and induce apoptosis in glioblastoma cells.

Fibulin-5 is a tumour suppressor inhibiting cell migration and invasion in ovarian cancer

AIMS

Fibulin-5 is an extracellular matrix (ECM) glycoprotein which has a role in the organisation and stabilisation of ECM structures and regulating cell proliferation and tumourigenesis. Here, the expression of fibulin-5 and its functional effects on the migration and invasion of ovarian cancer cells were assessed.

METHODS

Expression of fibulin-5 was detected in 44 ovarian tumour tissues by qRT-PCR, Western blotting and immunohistochemistry. We performed cell migration and invasion assays, and cell cycle analysis in fibulin-5 transfected SKOV3 (SKOV3-FBLN5) cells and the parental SKOV3 cells. We further examined the expression of three tissue inhibitors of metalloproteinases (TIMPs) and seven matrix metalloproteinases (MMPs) by RT-PCR.

RESULTS

mRNA and protein expression of fibulin-5 were down-regulated (0.05-fold and 0.1-fold) in ovarian carcinomas compared with control tissues (p<0.01 and p=0.022). In wound-healing and invasion assays, significantly fewer SKOV3-FBLN5 cells than SKOV3 control cells migrated and invaded (39.1%, p=0.046 and 70%, p=0.03, respectively), which was reversed by siRNA-treatment. Overexpression of fibulin-5 induced G2/M arrest and increased cyclin B1, CDC2 and CDC25C. Expression of TIMP-2 (0.56-fold), MMP-3 (0.43-fold) and MMP-13 (0.18-fold) was lower and MMP-9 expression (2.20-fold) was higher in SKOV3-FBLN5 cells than in control cells.

CONCLUSIONS

Fibulin-5 is significantly down-regulated in ovarian carcinoma and acts as a tumour suppressor by inhibiting the migration and invasion of ovarian cancer cells.

Targeted inhibition of phosphatidyl inositol-3-kinase p110β, but not p110α, enhances apoptosis and sensitivity to paclitaxel in chemoresistant ovarian cancers

The phosphatidylinositol 3-kinase (PI3K) pathway is one of the critical signaling cascades playing important roles in the chemoresistance of human cancer cells, including ovarian cancer. In this study, we investigated the potential of targeting the PI3K p110β-isoform as a novel approach to overcome the chemoresistance in ovarian cancer. The effects on apoptosis, cell viability, proliferation and migration in chemoresistant ovarian cancer cell were determined following targeted p110β inhibition by small interfering RNA (siRNA). Seven paclitaxel (PTX)-resistant sublines (SKpacs and A2780pac) were produced from SKOV3 and A2780 ovarian cancer cell lines. We, first, evaluated the expression of PI3K p110 isoforms in chemosensitive and chemoresistant ovarian cancer cell lines and patient specimens, and found that p110β-isoform was significantly overexpressed both in a panel of ovarian cancer samples, and in PTX-resistant sublines compared with their parent cell lines. RNA interference-mediated p110β silencing augmented PTX-mediated apoptosis (31.15 ± 13.88 %) and reduced cell viability (67 %) in PTX-resistant cells, whereas targeting p110α did not show a significant change in cell viability and apoptosis. In addition, p110β silencing impaired cell proliferation (60 %) in PTX-resistant SKpac cells. We also found the combined treatment group with p110β siRNA and PTX showed a significant inhibition of tumor growth of SKpac cells compared to the PTX-only treated group in a xenograft nude mouse model. Thus, the siRNA-mediated silencing of PI3K p110β resensitizes PTX-resistant ovarian cancer cells, and may be a useful therapeutic strategy for PTX-resistant ovarian cancers.

Expression of PI3Kp110α and PI3Kp110β in colorectal canceration

AIM: To investigate the expression of PI3Kp110α and PI3Kp110β in colorectal canceration and to analyze their correlation.

METHODS: PI3Kp110α and PI3Kp110β expression was detected by immunohistochemistry in 30 cases of normal colorectal mucosa, 46 cases of low-grade intraepithelial neoplasia (LGIN), 32 cases of high-grade intraepithelial neoplasia (HGIN) and 60 cases of colorectal carcinoma.

RESULTS: The expression of PI3Kp110α in colorectal carcinoma was significantly higher than that in normal colorectal mucosa and LGIN (both P < 0.05), but there was no significant difference between colorectal carcinoma and HGIN (P > 0.05). The expression of PI3Kp110β was highest in colorectal carcinoma, followed by HGIN, LGIN and normal colorectal mucosa (P < 0.05). PI3Kp110α expression was correlated with patient age, tumor size and tumor differentiation (all P < 0.05). PI3Kp110β expression was correlated with TNM stage and degree of tumor differentiation (both P < 0.05). The expression of PI3Kp110α was positively correlated with that of PI3Kp110β in LGIN (P < 0.05). There was no significant correlation between the expression of PI3Kp110α and that of PI3Kp110β in colorectal carcinoma, HGIN or normal colorectal mucosa (all P > 0.05).

CONCLUSION: PI3Kp110α and p110β may play different roles in colorectal canceration.

Multiple roles for the p85α isoform in the regulation and function of PI3K signalling and receptor trafficking

The p85α protein is best known as the regulatory subunit of class 1A PI3Ks (phosphoinositide 3-kinases) through its interaction, stabilization and repression of p110-PI3K catalytic subunits. PI3Ks play multiple roles in the regulation of cell survival, signalling, proliferation, migration and vesicle trafficking. The present review will focus on p85α, with special emphasis on its important roles in the regulation of PTEN (phosphatase and tensin homologue deleted on chromosome 10) and Rab5 functions. The phosphatidylinositol-3-phosphatase PTEN directly counteracts PI3K signalling through dephosphorylation of PI3K lipid products. Thus the balance of p85α–p110 and p85α–PTEN complexes determines the signalling output of the PI3K/PTEN pathway, and under conditions of reduced p85α levels, the p85α–PTEN complex is selectively reduced, promoting PI3K signalling. Rab5 GTPases are important during the endocytosis, intracellular trafficking and degradation of activated receptor complexes. The p85α protein helps switch off Rab5, and if defective in this p85α function, results in sustained activated receptor tyrosine kinase signalling and cell transformation through disrupted receptor trafficking. The central role for p85α in the regulation of PTEN and Rab5 has widened the scope of p85α functions to include integration of PI3K activation (p110-mediated), deactivation (PTEN-mediated) and receptor trafficking/signalling (Rab5-mediated) functions, all with key roles in maintaining cellular homoeostasis.

Targeting the mTOR/4E-BP pathway in endometrial cancer

Endometrial cancer is the most common gynecologic malignancy. Although it is highly treatable in the early stages of disease, therapies for advanced and recurrent disease are rarely curative. A molecular and genetic understanding of endometrial cancer involves the mTOR signaling pathway, an emerging target for treatment of type I disease (the most common presentation). Endometrial cancers show a significant reliance on the mTOR pathway for survival, and studies to date have revealed a clinical advantage in targeting this pathway. Less well developed in the study of endometrial cancer is an understanding of mTOR signaling to its major downstream effector, translational control. Given the poor rate of success for treatment of late-stage endometrial cancer, increasing attention is being directed to the development of new therapeutic approaches, including targeting the mTOR pathway. Here, we discuss the potential benefit of targeting mTOR combined with existing chemotherapies by monitoring its impact on translational regulatory pathways and key translation targets in endometrial cancer. We also highlight laboratory and clinical research findings that will provide new avenues for future research and clinical development.

The catalytic phosphoinositol 3-kinase isoform p110δ is required for glioma cell migration and invasion

Glioblastoma multiforme (GBM) is a highly invasive and aggressive primary brain tumour in which loss of phosphatase and tensin homologue deleted on chromosome 10 (PTEN), a negative regulator of PI3K signalling, is a common feature. PTEN/PI3K/Akt signalling is involved in the regulation of proliferation, apoptosis and cell migration. Deregulation of PI3K signalling is considered an essential driver in gliomagenesis. However, the role of different PI3K isoforms in glioma is still largely unclear. Here we show that the catalytic PI3K isoform p110δ is consistently expressed at a high level in various glioma cell lines. We used small interfering RNA to selectively deplete p110δ and to determine its tumourigenic roles in PTEN-deficient cells. Interestingly, knockdown of p110δ decreased the cell migration and invasion ability of all GBM cell lines tested. Mechanistically, p110δ knockdown reduced the protein levels of focal adhesion kinase and cell division cycle 42, key regulators of cellular migration. In contrast, pharmacologic inhibition of p110δ by IC87114 or CAL-101 also clearly impaired glioma cell migration but had no obvious effect on the invasion capacity thus pinpointing to possible kinase-dependent and -independent roles of p110δ in glioma pathology. In summary, our data provide novel evidence that in glioma cells p110δ is a key regulator of cell movement and thus may contribute to the highly invasive phenotype of GBM. Isoform specific targeting of PI3Kδ may be beneficial in the treatment of glioblastoma multiforme by specifically inhibiting tumour cell migration capacity.

PTEN restoration and PIK3CB knockdown synergistically suppress glioblastoma growth in vitro and in xenografts

Glioblastoma is the most frequent and malignant glioma in adults. To develop an effective gene therapy strategy for glioblastoma, we investigated the anti-proliferative effects of phosphatase and tensin homolog (PTEN) restoration and siRNAs specifically targeting PIK3CB and PIK3CA on PTEN-deficient glioblastoma cells in vitro and in subcutaneous xenografts. Restoration of PTEN or knockdown of PIK3CB, but not PIK3CA, in glioblastoma cells markedly down-regulates the phosphorylation level of AKT, inhibits cell proliferation and colony formation, arrests the cell cycle at the G0/G1 stage, and promotes caspase-dependent apoptosis. Combined treatment with PTEN restoration and PIK3CB knockdown shows strong synergy. PTEN restoration or PIK3CB knockdown is also able to efficiently inhibit the growth of human U251 glioblastoma xenografts in nude mice, while tumor growth is entirely suppressed by a combination of the two treatments. In addition, we found that the mRNA levels of inhibitors of apoptosis proteins (IAPs) are reduced in U251 cells by PTEN restoration, suggesting that combined antitumor effects may also be partly attributed to the inhibition of the IAP pathway by PTEN restoration. Collectively, our results demonstrate that PI3 K isoforms play specific roles in tumorigenesis, and that combined treatment of PTEN restoration and PIK3CB siRNA is a promising gene therapy strategy for PTEN-deficient gliomas.

The role of PI 3-kinase p110beta in AKT signally, cell survival, and proliferation in human prostate cancer cells

BACKGROUND

Class IA PI 3-kinases produce phosphatidylinositol (3,4,5)-trisphosphate (PIP3). PIP3 is bound by AKT which facilities its activation by PDK1. Activated AKT promotes cell survival and stimulates cell proliferation. Class IA PI 3-kinases are heterodimers consisting of a regulatory subunit p85 and a catalytic subunit p110. The p110alpha isoform has been shown to be mutated in a number of tumor types. A number of recent studies suggest that the p110beta isoform may be functionally relevant in prostate cancer. In this study we extend this work to include the examination of the expression and functional properties of p110alpha and p110beta in three different prostate cancer cell lines, DU145, LNCaP, PC3, as well as the non-tumorigenic but immortalized RWPE1 prostate epithelial cell line.

METHODS

Western blot analysis was used to measure protein expression and quantitative real-time PCR was used to measure mRNA levels. After targeted knockdown using isoform-specific siRNAs to reduce PI 3-kinase p110alpha or p110beta isoform expression, we measured downstream signally events such as phosphorylation of AKT, ERK 1/2, PDK, and FOXO, as well as biological consequences such as changes in apoptosis, and alterations in cell cycle progression.

RESULTS

In all three prostate cancer cell lines examined, targeted knockdown of p110beta, and not p110alpha, resulted in significantly reduced AKT, PDK, and FOXO phosphorylation. While knockdown of either p110 isoform resulted in an increase in apoptosis and a cell cycle arrest in G1 in the remaining non-apoptotic cells, these effects were much more pronounced with knockdown of p110beta.

CONCLUSIONS

Our results support the concept that p110beta appears to be the predominant functional class I PI 3-kinase isoform in prostate cancer cells.

PIK3CA and PIK3CB inhibition produce synthetic lethality when combined with estrogen deprivation in estrogen receptor-positive breast cancer

Several phosphoinositide 3-kinase (PI3K) catalytic subunit inhibitors are currently in clinical trial. We therefore sought to examine relationships between pharmacologic inhibition and somatic mutations in PI3K catalytic subunits in estrogen receptor (ER)-positive breast cancer, in which these mutations are particularly common. RNA interference (RNAi) was used to determine the effect of selective inhibition of PI3K catalytic subunits, p110alpha and p110beta, in ER(+) breast cancer cells harboring either mutation (PIK3CA) or gene amplification (PIK3CB). p110alpha RNAi inhibited growth and promoted apoptosis in all tested ER(+) breast cancer cells under estrogen deprived-conditions, whereas p110beta RNAi only affected cells harboring PIK3CB amplification. Moreover, dual p110alpha/p110beta inhibition potentiated these effects. In addition, treatment with the clinical-grade PI3K catalytic subunit inhibitor BEZ235 also promoted apoptosis in ER(+) breast cancer cells. Importantly, estradiol suppressed apoptosis induced by both gene knockdowns and BEZ235 treatment. Our results suggest that PI3K inhibitors should target both p110alpha and p110beta catalytic subunits, whether wild-type or mutant, and be combined with endocrine therapy for maximal efficacy when treating ER(+) breast cancer.

Should individual PI3 kinase isoforms be targeted in cancer?

Activation of the phosphoinositide-3-kinase (PI3K) signaling pathway is frequently found in common human cancers, brought about by oncogenic receptor tyrosine kinases (RTKs) acting upstream, PTEN loss, or activating mutations of PI3K itself. Recent studies have delineated distinct but overlapping functions in cell signaling and tumorigenesis for p110alpha and p110beta, the two major catalytic subunits of PI3K expressed in the tissues of origin for the common tumor types. In most cell types studied, p110alpha carries the majority of the PI3K signal in classic RTK signal transduction, while p110beta responds to GPCRs. Both p110alpha and p110beta function in cellular transformation induced by alterations in components of PI3K pathway. Specifically, p110alpha is essential for the signaling and growth of tumors driven by PIK3CA mutations and/or oncogenic RTKs/Ras, whereas p110beta is the major isoform in mediating PTEN-deficient tumorigenesis. While pan-PI3K inhibitors are currently being tested in the clinic, p110 isoform-specific inhibition holds promise as a therapeutic strategy.

Phosphatidylinositol 3-kinase inhibition broadly sensitizes glioblastoma cells to death receptor- and drug-induced apoptosis

The aberrant activity of the phosphatidylinositol 3-kinase (PI3K) pathway has been reported to correlate with adverse clinical outcome in human glioblastoma in vivo. However, the question of how this survival network can be successfully targeted to restore the sensitivity of glioblastoma to apoptosis induction has not yet been answered. Here, we report that inhibition of PI3K by LY294002 broadly sensitizes wild-type and mutant PTEN glioblastoma cells to both death receptor- and chemotherapy-induced apoptosis, whereas mammalian target of rapamycin (mTOR) inhibition is not sufficient to restore apoptosis sensitivity. LY294002 significantly enhances apoptosis triggered by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), agonistic anti-CD95 antibodies, or several anticancer drugs (i.e., doxorubicin, etoposide, and vincristine) in a highly synergistic manner. In addition, LY294002 cooperates with TRAIL or doxorubicin to suppress colony formation, thus also showing a strong effect on long-term survival. Similarly, genetic knockdown of PI3K subunits p110alpha and/or p110beta by RNA interference (RNAi) primes glioblastoma cells for TRAIL- or doxorubicin-mediated apoptosis. In contrast to PI3K inhibition, pharmacologic or genetic blockade of mTOR by RAD001 (everolimus), rapamycin, or RNAi fails to enhance TRAIL- or doxorubicin-induced apoptosis. Analysis of apoptosis pathways reveals that PI3K inhibition acts in concert with TRAIL or doxorubicin to trigger mitochondrial membrane permeabilization, caspase activation, and caspase-dependent apoptosis, which are abolished by the caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone. Most importantly, PI3K inhibition by LY294002 sensitizes primary cultured glioblastoma cells obtained from surgical specimens to TRAIL- or chemotherapy-induced cell death. By showing that PI3K inhibition broadly primes glioblastoma cells for apoptosis, our findings provide the rationale for using PI3K inhibitors in combination regimens to enhance TRAIL- or chemotherapy-induced apoptosis in glioblastoma.

FoxO proteins in pancreatic β-cells as potential therapeutic targets in diabetes

Diabetes results from complete (Type 1) or progressive (Type 2) insulin insufficiency. Resulting chronic and acute hyperglycemia are thus prevented mainly by insulin injections, a therapy that is care intensive, costly and does not abolish vascular damage, with severe consequences for the patient in the long term. In view of the epidemic spread of the disease, diabetes is considered a major threat for public healthcare systems. Thus, there is a great incentive to find therapies and drugs preserving or restoring pancreatic β-cells mass and function. In this context, this review addresses the FoxO transcription factors as direct or indirect, in vivo or ex vivo drug targets, since FoxO proteins play a central role for β-cells growth and resistance to oxidative stress. The review includes specific proposals for preclinical drug development.

Future of RNAi-based therapies for human papillomavirus-associated cervical cancer

Over 99% of cervical cancers are associated with infection of high-risk type human papillomaviruses (HPV). These viruses infect epithelial cells lining the cervix and express the early viral genes E6 and E7, which are oncogenes and are primarily responsible for the transformation of the epithelial cells. The continuous expression of those genes is essential for maintenance of the cancer cell phenotype and viability. These viral genes can be silenced using oligonucleotide-based techniques, for example RNAi, antisense RNA and ribozymes. In spite of promising results in vitro and in vivo, in mice, these methods have thus far proved unsuccessful in humans, owing to the lack of an effective delivery system amongst other limitations. In this review we will discuss potential gene-silencing strategies in cervical cancer that would target both viral genes such as E6 and E7, and cellular genes that become deregulated such as E2F, p53, Akt, mTor, NF-κB or Bcl-2. By investigating these approaches we may generate an effective treatment for HPV-induced cervical cancer using gene silencing.