Class I PI3K in oncogenic cellular transformation. Oncogene. 2008;27:5486-5496. [PMID: 18794883 DOI: 10.1038/onc.2008.244]

CDK 4/6 inhibitors sensitize PIK3CA mutant breast cancer to PI3K inhibitors

Activation of the phosphoinositide 3-kinase (PI3K) pathway occurs frequently in breast cancer. However, clinical results of single-agent PI3K inhibitors have been modest to date. A combinatorial drug screen on multiple PIK3CA mutant cancers with decreased sensitivity to PI3K inhibitors revealed that combined CDK 4/6-PI3K inhibition synergistically reduces cell viability. Laboratory studies revealed that sensitive cancers suppress RB phosphorylation upon treatment with single-agent PI3K inhibitors but cancers with reduced sensitivity fail to do so. Similarly, patients' tumors that responded to the PI3K inhibitor BYL719 demonstrated suppression of pRB, while nonresponding tumors showed sustained or increased levels of pRB. Importantly, the combination of PI3K and CDK 4/6 inhibitors overcomes intrinsic and adaptive resistance leading to tumor regressions in PIK3CA mutant xenografts.

Dietary restriction-resistant human tumors harboring the PIK3CA-activating mutation H1047R are sensitive to metformin

Cancer cells expressing constitutively active phosphatidylinositol-3 kinase (PI3K) are proliferative regardless of the absence of insulin, and they form dietary restriction (DR)-resistant tumors in vivo. Because the binding of insulin to its receptors activates the PI3K/AKT/mammalian target of rapamycin (mTOR) signaling cascade, activating mutations in the PIK3CA oncogene may determine tumor response to DR-like pharmacological strategies targeting the insulin and mTOR pathways. The anti-diabetic drug metformin is a stereotypical DR mimetic that exerts its anti-cancer activity through a dual mechanism involving insulin-related (systemic) and mTOR-related (cell-autonomous) effects. However, it remains unclear whether PIK3CA-activating mutations might preclude the anti-cancer activity of metformin in vivo. To model the oncogenic PIK3CA-driven early stages of cancer, we used the clonal breast cancer cell line MCF10DCIS.com, which harbors the gain-of-function H1047R hot-spot mutation in the catalytic domain of the PI3KCA gene and has been shown to form DR-refractory xenotumors. To model PIK3CA-activating mutations in late stages of cancer, we took advantage of the isogenic conversion of a PIK3CA-wild-type tumor into a PIK3CA H1047R-mutated tumor using the highly metastatic colorectal cancer cell line SW48. MCF10DCIS.com xenotumors, although only modestly affected by treatment with oral metformin (approximately 40% tumor growth inhibition), were highly sensitive to the intraperitoneal (i.p.) administration of metformin, the anti-cancer activity of which increased in a time-dependent manner and reached >80% tumor growth inhibition by the end of the treatment. Metformin treatment via the i.p. route significantly reduced the proliferation factor mitotic activity index (MAI) and decreased tumor cellularity in MCF10DCIS.com cancer tissues. Whereas SW48-wild-type (PIK3CA+/+) cells rapidly formed metformin-refractory xenotumors in mice, ad libitum access to water containing metformin significantly reduced the growth of SW48-mutated (PIK3CAH1047R/+) xenotumors by approximately 50%. Thus, metformin can no longer be considered as a bona fide DR mimetic, at least in terms of anti-cancer activity, because tumors harboring the insulin-unresponsive, DR-resistant, PIK3CA-activating mutation H1047R remain sensitive to the anti-tumoral effects of the drug. Given the high prevalence of PIK3CA mutations in human carcinomas and the emerging role of PIK3CA mutation status in the treatment selection process, these findings might have a significant impact on the design of future trials evaluating the potential of combining metformin with targeted therapy.

New Approaches to Target T-ALL

Acute lymphoblastic leukemia is the most common malignancy in children. Although it is now curable in 80-90% of cases, patients with T-cell acute lymphoblastic leukemia (T-ALL) experience a higher frequency of induction failure and early relapse. Despite aggressive treatment approaches, including transplantation and new salvage regimens, most children with relapsed T-ALL will not be cured. As such, we are in need of new targeted therapies for the disease. Recent advances in the molecular characterization of T-ALL have uncovered a number of new therapeutic targets. This review will summarize recent advancements in the study of inhibiting the NOTCH1, PI3K-AKT, and Cyclin D3:CDK4/6 pathways as therapeutic strategies for T-ALL. We will focus on pre-clinical studies supporting the testing of small-molecule inhibitors targeting these proteins and the rationale of combination therapies. Moreover, epigenetic approaches to modulate T-ALL are rapidly emerging. Here, we will discuss the data supporting the role of bromodomain and extra-terminal bromodomain inhibitors in human T-ALL.

CDK 4/6 inhibitors sensitize PIK3CA mutant breast cancer to PI3K inhibitors

Activation of the phosphoinositide 3-kinase (PI3K) pathway occurs frequently in breast cancer. However, clinical results of single-agent PI3K inhibitors have been modest to date. A combinatorial drug screen on multiple PIK3CA mutant cancers with decreased sensitivity to PI3K inhibitors revealed that combined CDK 4/6-PI3K inhibition synergistically reduces cell viability. Laboratory studies revealed that sensitive cancers suppress RB phosphorylation upon treatment with single-agent PI3K inhibitors but cancers with reduced sensitivity fail to do so. Similarly, patients' tumors that responded to the PI3K inhibitor BYL719 demonstrated suppression of pRB, while nonresponding tumors showed sustained or increased levels of pRB. Importantly, the combination of PI3K and CDK 4/6 inhibitors overcomes intrinsic and adaptive resistance leading to tumor regressions in PIK3CA mutant xenografts.

Association between the lengths of GT dinucleotide repeat in the PIK3CA gene with breast cancer risk

The phosphatidylinositol 3-kinase (PI3 K)/Akt signaling pathway is one of the most commonly mutated pathways in breast cancer. To date, there has been no study on polymorphism of phosphatidylinositol-3,4-bisphosphonate 3-kinase, catalytic subunit alpha (PIK3CA) gene microsatellites and their link with breast cancer risk. In the present study, we investigate the guanine-thymine (GT) dinucleotide repeat polymorphism in intron 1 of PIK3CA gene in a cohort of 200 breast cancer patients and 200 healthy individuals and its link to the risk of developing breast cancer. The results of this study demonstrate that PIK3CA gene allele distribution in Isfahan population varies between 13 and 20 repeats. GT14 and GT16 were the most common allele present in patients, and GT17 was the most common allele in controls. Women with one or two alleles shorter than 17 GT repeat have a significantly higher risk of developing breast cancer [Odds ratio (OR) 3.6, p = 0.00001 and OR 3.98, p = 0.000001, respectively], in contrast, women with one or two alleles longer than 16 are at lower risk of breast cancer. This result suggests a potential role for this microsatellite as a predictive marker of breast cancer risk in Iranian women.

PIK3CA and TP53 gene mutations in human breast cancer tumors frequently detected by ion torrent DNA sequencing

Breast cancer is the most common malignancy and the leading cause of cancer deaths in women worldwide. While specific genetic mutations have been linked to 5-10% of breast cancer cases, other environmental and epigenetic factors influence the development and progression of the cancer. Since unique mutations patterns have been observed in individual cancer samples, identification and characterization of the distinctive breast cancer molecular profile is needed to develop more effective target therapies. Until recently, identifying genetic cancer mutations via personalized DNA sequencing was impractical and expensive. The recent technological advancements in next-generation DNA sequencing, such as the semiconductor-based Ion Torrent sequencing platform, has made DNA sequencing cost and time effective with more reliable results. Using the Ion Torrent Ampliseq Cancer Panel, we sequenced 737 loci from 45 cancer-related genes to identify genetic mutations in 105 human breast cancer samples. The sequencing analysis revealed missense mutations in PIK3CA, and TP53 genes in the breast cancer samples of various histologic types. Thus, this study demonstrates the necessity of sequencing individual human cancers in order to develop personalized drugs or combination therapies to effectively target individual, breast cancer-specific mutations.

microRNA: a promising diagnostic biomarker and therapeutic target for hepatocellular carcinoma

microRNAs constitute a novel class of small, non-coding RNAs that negatively regulate gene expression via translational inhibition or mRNA degradation. Aberrant miRNA expression has been implicated in the initiation, progression, and metastasis of hepatocellular carcinoma (HCC). It is well-documented that miRNAs function as either tumor suppressor genes or oncogenes in the development and progression of HCC. Additionally, substantial evidence suggests that unique miRNA signatures can serve as valuable diagnostic and prognostic biomarkers for HCC. Interestingly, certain subsets of miRNAs have also been identified as potential therapeutic targets for HCC.

Suppression of CD4+ T lymphocyte activation in vitro and experimental encephalomyelitis in vivo by the phosphatidyl inositol 3-kinase inhibitor PIK-75

Class IA phosphatidyl inositol-3 kinases (PI3-K) are important targets in cancer therapy and are essential to immune responses, particularly through costimulation by CD28 and ICOS. Thus, small PI3-K inhibitors are likely candidates to immune intervention. PIK-75 is an efficient inhibitor of the PI3-K p110alpha catalytic subunits that suppresses tumor growth, and its effects on immune and autoimmune responses should be studied. Here, we describe the effect of PIK-75 on different immune parameters in vitro and in vivo. PIK-75 at concentrations commonly used in vitro (≥0.1 μM) inhibited T and B cell activation by Concanavalin A and LPS, respectively, and survival of non-stimulated spleen cells. In naive CD4+ T lymphocytes, PIK-75 induced apoptosis of resting or activated cells that was prevented by caspase inhibitors. At low nanomolar concentrations (≤10 nM), PIK-75 inhibited naive CD4+ T cell proliferation, and IL-2 and IFN-gamma production induced by anti-CD3 plus anti-CD28. In activated CD4+ T blasts costimulated by ICOS, PIK-75 (less than 10 nM) inhibited IFN-gamma, IL-17A, or IL-21 secretion. Furthermore, PIK-75 (20 mg/kg p.o.) suppressed clinical symptoms in ongoing experimental autoimmune encephalomyelitis (EAE) and inhibited MOG-specific responses in vitro. Thus, PIK-75 is an efficient suppressor of EAE, modulating lymphocyte function and survival.

Emerging roles of the p38 MAPK and PI3K/AKT/mTOR pathways in oncogene-induced senescence

Oncogene-induced senescence (OIS) is a tumor-suppressing response that must be disrupted for cancer to develop. Mechanistic insights into OIS have begun to emerge. Activation of the p53/p21(WAF1) and/or p16(INK4A) tumor-suppressor pathways is essential for OIS. Moreover, the DNA damage response, chromatin remodeling, and senescence-associated secretory phenotype (SASP) are important for the initiation and maintenance of OIS. This review discusses recent advances in elucidating the mechanisms of OIS, focusing on the roles of the p38 mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/cellular homolog of murine thymoma virus AKT/mammalian target of rapamycin (mTOR) pathways. These studies indicate that OIS is mediated by an intricate signaling network. Further delineation of this network may lead to development of new cancer therapies targeting OIS.

Characterization of the activity of the PI3K/mTOR inhibitor XL765 (SAR245409) in tumor models with diverse genetic alterations affecting the PI3K pathway

Activation of the PI3K (phosphoinositide 3-kinase) pathway is a frequent occurrence in human tumors and is thought to promote growth, survival, and resistance to diverse therapies. Here, we report pharmacologic characterization of the pyridopyrimidinone derivative XL765 (SAR245409), a potent and highly selective pan inhibitor of class I PI3Ks (α, β, γ, and δ) with activity against mTOR. Broad kinase selectivity profiling of >130 protein kinases revealed that XL765 is highly selective for class I PI3Ks and mTOR over other kinases. In cellular assays, XL765 inhibits the formation of PIP(3) in the membrane, and inhibits phosphorylation of AKT, p70S6K, and S6 phosphorylation in multiple tumor cell lines with different genetic alterations affecting the PI3K pathway. In a panel of tumor cell lines, XL765 inhibits proliferation with a wide range of potencies, with evidence of an impact of genotype on sensitivity. In mouse xenograft models, oral administration of XL765 results in dose-dependent inhibition of phosphorylation of AKT, p70S6K, and S6 with a duration of action of approximately 24 hours. Repeat dose administration of XL765 results in significant tumor growth inhibition in multiple human xenograft models in nude mice that is associated with antiproliferative, antiangiogenic, and proapoptotic effects.

Characterization of breast cancers with PI3K mutations in an academic practice setting using SNaPshot profiling

Mutations in the PIK3CA gene are common in breast cancer and represent a clinically useful therapeutic target. Several larger, population-based studies have shown a positive prognostic significance associated with these mutations. This study aims to further identify characteristics of patients harboring PIK3CA mutations while evaluating the clinical impact of genomic testing for these mutations. Tumors from 312 patients at Vanderbilt-Ingram Cancer Center were analyzed for PIK3CA mutations using a multiplex screening assay (SNaPshot). Mutation rates, receptor status, histopathologic characteristics, and time to recurrence were assessed. The number of patients participating in clinical trials, specifically trials relating to the PIK3CA mutation, was examined. Statistically significant differences between wild-type and mutated tumors were determined using the Wilcoxon, Pearson, and Fischer exact tests. The PIK3CA mutation was found in 25 % of tumors tested. Patients with PIK3CA mutations were significantly more likely to express hormone receptors, be of lower combined histological grade, and have a reduced time to recurrence. Patients found to have a PIK3CA mutation were significantly more likely to enter a PIK3CA-specific clinical trial. In addition to confirming previously established positive prognostic characteristics of tumors harboring PIK3CA mutations, this study demonstrates the feasibility and utility of mutation profiling in a clinical setting. PIK3CA mutation testing impacted treatment and resulted in more patients entering mutation-specific clinical trials.

OVA66, a tumor associated protein, induces oncogenic transformation of NIH3T3 cells

The tumor associated antigen OVA66 has been demonstrated to be highly expressed in malignant tumors and implicated in various cellular processes. To further elucidate its oncogenic character, we established an OVA66 stably overexpressed NIH3T3 cell line and a vector transfected control, named NIH3T3-flagOVA66 and NIH3T3-mock, respectively. NIH3T3-flagOVA66 cells showed faster cell cycling, proliferation, cell migration and more resistance to 5-fluorouracil-induced apoptosis. When NIH3T3-flagOVA66 and NIH3T3-mock cells were injected into nude mice for xenograft tumorigenicity assays, the NIH3T3-flagOVA66 cells formed tumors whereas no tumors were observed in mice inoculated with NIH3T3-mock cells. Analysis of PI3K/AKT and ERK1/2 MAPK signaling pathways by serum stimulation indicated hyperactivation of AKT and ERK1/2 in NIH3T3-flagOVA66 cells compared with NIH3T3-mock cells, while a decreased level of p-AKT and p-ERK1/2 were observed in OVA66 knocked down HeLa cells. To further validate if the p-AKT or p-ERK1/2 is essential for OVA66 induced oncogenic transformation, we treated the cells with the PI3K/AKT specific inhibitor LY294002 and the ERK1/2 MAPK specific inhibitor PD98059 and found either inhibitor can attenuate the cell colony forming ability in soft agar and the cell viability of NIH3T3-flagOVA66 cells, suggesting aberrantly activated AKT and ERK1/2 signaling be indispensible of the tumorigenic role of OVA66. Our results indicate that OVA66 is important in oncogenic transformation, promoting proliferation, cell migration and reducing apoptosis via hyperactivating PI3K/AKT and ERK1/2 MAPK signaling pathway. Thus, OVA66 might be a novel target for early detection, prevention and treatment of tumors in the future.

Synergistic anti-tumor effects of a novel phosphatidyl inositol-3 kinase/mammalian target of rapamycin dual inhibitor BGT226 and gefitinib in non-small cell lung cancer cell lines

Epidermal growth factor receptor (EGFR) and PI3K/mTOR pathway are drug targets for non-small cell lung cancer (NSCLC). Herein, we investigated anti-tumor effects of the combination of BGT226, a novel PI3K/mTOR dual inhibitor, and gefitinib on NSCLC cell lines which are high sensitive to gefitinib. The combination of BGT226 and gefitinib exhibited supra-additive growth inhibitory effects in PC-9 and HCC827 cells. Apoptotic induction and the inhibition of PI3K/mTOR signaling were enhanced by the combination. Significant tumor growth suppression was observed in xenograft model by the combination. These results suggest that the combination is effective in EGFR inhibitor-sensitive NSCLC therapy.

Activation of PI3Kα by physiological effectors and by oncogenic mutations: structural and dynamic effects

PI3Kα, a heterodimeric lipid kinase, catalyzes the conversion of phosphoinositide-4,5-bisphosphate (PIP2) to phosphoinositide-3,4,5-trisphosphate (PIP3), a lipid that recruits to the plasma membrane proteins that regulate signaling cascades that control key cellular processes such as cell proliferation, carbohydrate metabolism, cell motility, and apoptosis. PI3Kα is composed of two subunits, p110α and p85, that are activated by binding to phosphorylated receptor tyrosine kinases (RTKs) or their substrates. The gene coding for p110α, PIK3CA, has been found to be mutated in a large number of tumors; these mutations result in increased PI3Kα kinase activity. The structure of the complex of p110α with a fragment of p85 containing the nSH2 and the iSH2 domains has provided valuable information about the mechanisms underlying the physiological activation of PI3Kα and its pathological activation by oncogenic mutations. This review discusses information derived from x-ray diffraction and theoretical calculations regarding the structural and dynamic effects of mutations in four highly mutated regions of PI3K p110α, as well as the proposed mechanisms by which these mutations increase kinase activity. During the physiological activation of PI3Kα, the phosphorylated tyrosine of RTKs binds to the nSH2 domain of p85, dislodging an inhibitory interaction between the p85 nSH2 and a loop of the helical domain of p110α. Several of the oncogenic mutations in p110α activate the enzyme by weakening this autoinhibitory interaction. These effects involve structural changes as well as changes in the dynamics of the enzyme. One of the most common p110α mutations, H1047R, activates PI3Kα by a different mechanism: it increases the interaction of the enzyme with the membrane, maximizing the access of the PI3Kα to its substrate PIP2, a membrane lipid.

Genetic unraveling of colorectal cancer

Colorectal cancer is a common disease in both men and women (being the third most common cancer in men and the second most common among women) and thus represents an important and serious public health issue, especially in the western world. Although it is a well-established fact that cancers of the large intestine produce symptoms relatively earlier at a stage that can be easily cured by resection, a large number of people lose their lives to this deadly disease each year. Recent times have seen an important change in the incidence of colorectal cancer in different parts of the world. The etiology of colorectal cancer is multifactorial and is likely to involve the actions of genes at multiple levels along the multistage carcinogenesis process. Exhaustive efforts have been made out in the direction of unraveling the role of various environmental factors, gene mutations, and polymorphisms worldwide (as well as in Kashmir-"a valley of gastrointestinal cancers") that have got a role to play in the development of this disease so that antitumor drugs could be developed against this cancer, first, and, finally, the responsiveness or resistance to these agents could be understood for combating this global issue.

PI3K p110δ uniquely promotes gain-of-function Shp2-induced GM-CSF hypersensitivity in a model of JMML

Although hyperactivation of the Ras-Erk signaling pathway is known to underlie the pathogenesis of juvenile myelomonocytic leukemia (JMML), a fatal childhood disease, the PI3K-Akt signaling pathway is also dysregulated in this disease. Using genetic models, we demonstrate that inactivation of phosphatidylinositol-3-kinase (PI3K) catalytic subunit p110δ, but not PI3K p110α, corrects gain-of-function (GOF) Shp2-induced granulocyte macrophage-colony-stimulating factor (GM-CSF) hypersensitivity, Akt and Erk hyperactivation, and skewed hematopoietic progenitor distribution. Likewise, potent p110δ-specific inhibitors curtail the proliferation of GOF Shp2-expressing hematopoietic cells and cooperate with mitogen-activated or extracellular signal-regulated protein kinase kinase (MEK) inhibition to reduce proliferation further and maximally block Erk and Akt activation. Furthermore, the PI3K p110δ-specific inhibitor, idelalisib, also demonstrates activity against primary leukemia cells from individuals with JMML. These findings suggest that selective inhibition of the PI3K catalytic subunit p110δ could provide an innovative approach for treatment of JMML, with the potential for limiting toxicity resulting from the hematopoietic-restricted expression of p110δ.

Neuron-specific regulation of class I PI3K catalytic subunits and their dysfunction in brain disorders

The phosphoinositide 3-kinase (PI3K) complex plays important roles in virtually all cells of the body. The enzymatic activity of PI3K to phosphorylate phosphoinositides in the membrane is mediated by a group of catalytic and regulatory subunits. Among those, the class I catalytic subunits, p110α, p110β, p110γ, and p110δ, have recently drawn attention in the neuroscience field due to their specific dysregulation in diverse brain disorders. While in non-neuronal cells these catalytic subunits may have partially redundant functions, there is increasing evidence that in neurons their roles are more specialized, and confined to distinct receptor-dependent pathways. This review will summarize the emerging role of class I PI3K catalytic subunits in neurotransmitter-regulated neuronal signaling, and their dysfunction in a variety of neurological diseases, including fragile X syndrome, schizophrenia, and epilepsy. We will discuss recent literature describing the use of PI3K subunit-selective inhibitors to rescue brain disease-associated phenotypes in in vitro and animal models. These studies give rise to the exciting prospect that these drugs, originally designed for cancer treatment, may be repurposed as therapeutic drugs for brain disorders in the future.

Caffeine and the analog CGS 15943 inhibit cancer cell growth by targeting the phosphoinositide 3-kinase/Akt pathway

Caffeine is a naturally occurring methylxanthine that acts as a non-selective adenosine receptor antagonist. Epidemiological studies demonstrated habitual coffee drinking to be significantly associated with liver cancer survival. We aimed to investigate the effects of caffeine and its analog CGS 15943 on hepatocellular carcinoma (HCC) and pancreatic cancer adenocarcinoma (PDAC). We demonstrate that caffeine and CGS 15943 block proliferation in HCC and PDAC cell lines by inhibiting the PI3K/Akt pathway. Importantly a kinase profiling assay reveals that CGS 15943 targets specifically the catalytic subunit of the class IB PI3K isoform (p110γ). These data give mechanistic insight into the action of caffeine and its analogs and they identify these compounds as promising lead compounds to develop drugs that can specifically target this PI3K isoform whose key role in cancer progression is emerging.

Molecular therapy of colorectal cancer: progress and future directions

Colorectal cancer (CRC) remains one of the most common types of cancer and leading causes of cancer death worldwide. Although the introduction of cytotoxic drugs such as oxaliplatin, irinotecan and fluorouracil has improved the treatment of advanced CRC, the individual response to chemoradiotherapy varies tremendously from one patient to another. However, recent progress in CRC molecular therapies may provide new insight into the treatment of this disease. Currently, components of the EGFR, VEGF, Wnt and NF-kB pathways are the most important targets for CRC therapy. This review chronicles the development of molecular CRC therapies over the past few decades. We also provide an update on the current progress of research concerning the molecular pathways leading to CRC and discuss the possible implications for CRC therapy.

Phosphoinositide 3-kinase δ regulates migration and invasion of synoviocytes in rheumatoid arthritis

Cartilage destruction mediated by invasive fibroblast-like synoviocytes (FLS) plays a central role in pathogenesis of rheumatoid arthritis (RA). Increased cell migration and degradation of extracellular matrix are fundamental to these processes. The class I PI3Ks control cell survival, proliferation, and migration, which might be involved in cartilage damage in RA. PI3Kδ isoform was recently identified as a key regulator of FLS growth and survival, suggesting that it could contribute to synoviocyte aggressive behavior. Therefore, we assessed the role of PI3Kδ in RA synoviocyte migration and invasion. We observed that PI3Kδ inhibition or small interfering RNA knockdown decreased platelet-derived growth factor (PDGF)-mediated migration and invasion of FLS. We then showed that PI3Kδ regulates the organization of actin cytoskeleton and lamellipodium formation during PDGF stimulation. To gain insight into molecular mechanisms, we examined the effect of PI3Kδ inhibition on Rac1/PAK, FAK, and JNK activation. Our studies suggest that Rac1/PAK is key target of PDGF-mediated PI3Kδ signaling, whereas FAK and JNK are not involved. Thus, PI3Kδ contributes to multiple aspects of the pathogenic FLS behavior in RA. These observations, together with previous findings that PI3Kδ regulates FLS growth and survival, suggest that PI3Kδ inhibition could be chondroprotective in RA by modulating synoviocyte growth, migration, and invasion.

Dominant-activating germline mutations in the gene encoding the PI(3)K catalytic subunit p110δ result in T cell senescence and human immunodeficiency

The p110δ subunit of phosphatidylinositol-3-OH kinase (PI(3)K) is selectively expressed in leukocytes and is critical for lymphocyte biology. Here we report fourteen patients from seven families who were heterozygous for three different germline, gain-of-function mutations in PIK3CD (which encodes p110δ). These patients presented with sinopulmonary infections, lymphadenopathy, nodular lymphoid hyperplasia and viremia due to cytomegalovirus (CMV) and/or Epstein-Barr virus (EBV). Strikingly, they had a substantial deficiency in naive T cells but an over-representation of senescent effector T cells. In vitro, T cells from patients exhibited increased phosphorylation of the kinase Akt and hyperactivation of the metabolic checkpoint kinase mTOR, enhanced glucose uptake and terminal effector differentiation. Notably, treatment with rapamycin to inhibit mTOR activity in vivo partially restored the abundance of naive T cells, largely 'rescued' the in vitro T cell defects and improved the clinical course.

PIK3CA gene alterations in bladder cancer are frequent and associate with reduced recurrence in non-muscle invasive tumors

Bladder cancer (BC) is the fifth most common cancer in the world, being the non-muscle invasive tumors (NMIBC) the most frequent. NMIBC shows a very high frequency of recurrence and, in certain cases, tumor progression. The phosphatidylinositol 3-kinase (PI3K) pathway, which controls cell growth, tumorigenesis, cell invasion and drug response, is frequently activated in numerous human cancers, including BC, in part through alterations of PIK3CA gene. However, the significance of PIK3CA gene alterations with respect to clinicopathological characteristics, and in particular tumor recurrence and progression, remains elusive. Here, we analyzed the presence of mutations in FGFR3 and PIK3CA genes and copy number alterations of PIK3CA gene in bladder tumor and their correspondent paired normal samples from 87 patients. We observed an extremely high frequency of PIK3CA gene alterations (mutations, copy gains, or both) in tumor samples, affecting primarily T1 and T2 tumors. A significant number of normal tissues also showed mutations and copy gains, being coincident with those found in the corresponding tumor sample. In low-grade tumors PIK3CA mutations associated with FGFR3 mutations. Alterations in PIK3CA gene resulted in increased Akt activity in tumors. Interestingly, the presence of PIK3CA gene alterations, and in particular gene mutations, is significantly associated with reduced recurrence of NMIBC patients. Importantly, the presence of FGFR3 mutations may influence the clinical outcome of patients bearing alterations in PIK3CA gene, and increased recurrence was associated to FGFR3 mutated, PIK3CA wt tumors. These findings may have high relevance in terms of using PI3K-targeted therapies for BC treatment.

Molecular targets for cancer therapy in the PI3K/AKT/mTOR pathway

Aberrations in various cellular signaling pathways are instrumental in regulating cellular metabolism, tumor development, growth, proliferation, metastasis and cytoskeletal reorganization. The fundamental cellular signaling cascade involved in these processes, the phosphatidylinositol 3-kinase/protein kinase-B/mammalian target of rapamycin (PI3K/AKT/mTOR), closely related to the mitogen-activated protein kinase (MAPK) pathway, is a crucial and intensively explored intracellular signaling pathway in tumorigenesis. Various activating mutations in oncogenes together with the inactivation of tumor suppressor genes are found in diverse malignancies across almost all members of the pathway. Substantial progress in uncovering PI3K/AKT/mTOR alterations and their roles in tumorigenesis has enabled the development of novel targeted molecules with potential for developing efficacious anticancer treatment. Two approved anticancer drugs, everolimus and temsirolimus, exemplify targeted inhibition of PI3K/AKT/mTOR in the clinic and many others are in preclinical development as well as being tested in early clinical trials for many different types of cancer. This review focuses on targeted PI3K/AKT/mTOR signaling from the perspective of novel molecular targets for cancer therapy found in key pathway members and their corresponding experimental therapeutic agents. Various aberrant prognostic and predictive biomarkers are also discussed and examples are given. Novel approaches to PI3K/AKT/mTOR pathway inhibition together with a better understanding of prognostic and predictive markers have the potential to significantly improve the future care of cancer patients in the current era of personalized cancer medicine.

Identification of a subset of human non-small cell lung cancer patients with high PI3Kβ and low PTEN expression, more prevalent in squamous cell carcinoma

PURPOSE

The phosphoinositide 3-kinase (PI3K) pathway is a major oncogenic signaling pathway and an attractive target for therapeutic intervention. Signaling through the PI3K pathway is moderated by the tumor suppressor PTEN, which is deficient or mutated in many human cancers. Molecular characterization of the PI3K signaling network has not been well defined in lung cancer; in particular, the role of PI3Kβ and its relation to PTEN in non-small cell lung cancer NSCLC remain unclear.

EXPERIMENTAL DESIGN

Antibodies directed against PI3Kβ and PTEN were validated and used to examine, by immunohistochemistry, expression in 240 NSCLC resection tissues [tissue microarray (TMA) set 1]. Preliminary observations were extended to an independent set of tissues (TMA set 2) comprising 820 NSCLC patient samples analyzed in a separate laboratory applying the same validated antibodies and staining protocols. The staining intensities for PI3Kβ and PTEN were explored and colocalization of these markers in individual tumor cores were correlated.

RESULTS

PI3Kβ expression was elevated significantly in squamous cell carcinomas (SCC) compared with adenocarcinomas. In contrast, PTEN loss was greater in SCC than in adenocarcinoma. Detailed correlative analyses of individual patient samples revealed a significantly greater proportion of SCC in TMA set 1 with higher PI3Kβ and lower PTEN expression when compared with adenocarcinoma. These findings were reinforced following independent analyses of TMA set 2.

CONCLUSIONS

We identify for the first time a subset of NSCLC more prevalent in SCC, with elevated expression of PI3Kβ accompanied by a reduction/loss of PTEN, for whom selective PI3Kβ inhibitors may be predicted to achieve greater clinical benefit.

What a tangled web we weave: emerging resistance mechanisms to inhibition of the phosphoinositide 3-kinase pathway

The phosphoinositide 3-kinase (PI3K) pathway is one of the most frequently mutated pathways in cancer, and is actively being pursued as a therapeutic target. Despite the importance of the PI3K pathway in cancer, durable responses to PI3K pathway-targeted therapies are uncommon with monotherapy. Several in vitro and xenograft models have elucidated compensatory signaling and genomic changes which may limit the therapeutic effectiveness of PI3K inhibitors in the clinic. Future clinical trials with prospective evaluation of tumor signaling and genomic changes are likely to identify novel resistance mechanisms as well as subsets of patients who may derive maximal benefit from PI3K pathway inhibitors.

SIGNIFICANCE

There are multiple ongoing clinical trials targeting the PI3K pathway members in several malignancies. This review summarizes the known mechanisms of resistance to targeting the PI3K pathway. Understanding of resistance mechanisms will help to inform more rational clinical trial design to optimize the clinical impact of targeting the PI3K pathway in cancer.

Inhibiting the RAS-PI3K pathway in cancer therapy

The PI3K pathway is over-activated in the majority of human cancers. This may occur through oncogenic activation of upstream RAS isoforms and tyrosine kinase receptors, or by mutational activation of components of the PI3K pathway themselves. Stimulation of the PI3K pathway enhances growth, survival, and metabolism of cancer cells. Migration, invasion, and angiogenesis are also supported by PI3K signaling. Thus, the PI3K pathway is an attractive candidate for the therapeutic targeting of tumors. Multiple kinases within the PI3Ks, AKT, and mTOR pathway have been selected for inhibition, and dual inhibitors have also been produced. Recently, the development of kinase inhibitors with enhanced specificity and improved pharmacokinetics has facilitated the investigation of PI3K pathway inhibition in clinical trials. Initial reports are encouraging, with tolerable toxicity profiles reported. PI3K inhibitors have provided some benefit as single-agent treatments of advanced solid tumors and the possibilities for enhanced effect with combination treatments look promising. In this chapter, we describe the PI3K inhibitors currently under investigation for the treatment of cancer and discuss the opportunities and obstacles that have been revealed by the latest preclinical and clinical studies.

Direct association of heat shock protein 20 (HSPB6) with phosphoinositide 3-kinase (PI3K) in human hepatocellular carcinoma: regulation of the PI3K activity

HSP20 (HSPB6), one of small heat shock proteins (HSPs), is constitutively expressed in various tissues and has several functions. We previously reported that the expression levels of HSP20 in human hepatocellular carcinoma (HCC) cells inversely correlated with the progression of HCC, and that HSP20 suppresses the growth of HCC cells via the AKT and mitogen-activated protein kinase signaling pathways. However, the exact mechanism underlying the effect of HSP20 on the regulation of these signaling pathways remains to be elucidated. To clarify the details of this effect in HCC, we explored the direct targets of HSP20 in HCC using human HCC-derived HuH7 cells with HSP20 overexpression. HSP20 proteins in the HuH7 cells were coimmunoprecipitated with the p85 regulatory subunit and p110 catalytic subunit of phosphoinositide 3-kinase (PI3K), an upstream kinase of AKT. Although HSP20 overexpression in HCC cells failed to affect the expression levels of PI3K, the activity of PI3K in the unstimulated cells and even in the transforming growth factor-α stimulated cells were downregulated by HSP20 overexpression. The association of HSP20 with PI3K was also observed in human HCC tissues in vivo. These findings strongly suggest that HSP20 directly associates with PI3K and suppresses its activity in HCC, resulting in the inhibition of the AKT pathway, and subsequently decreasing the growth of HCC.

Enzyme activity effects of N-terminal His-tag attached to catalytic sub-unit of phosphoinositide-3-kinase

NTT (N-terminal tags) on the catalytic (p110) sub-unit of PI 3-K (phosphoinositol 3-kinase) have previously been shown to increase cell signalling and oncogenic transformation. Here we test the impact of an NT (N-terminal) His-tag on in vitro lipid and protein kinase activity of all class-1 PI 3-K isoforms and two representative oncogenic mutant forms (E545K and H1047R), in order to elucidate the mechanisms behind this elevated signalling and transformation observed in vivo. Our results show that an NT His-tag has no impact on lipid kinase activity as measured by enzyme titration, kinetics and inhibitor susceptibility. Conversely, the NT His-tag did result in a differential effect on protein kinase activity, further potentiating the elevated protein kinase activity of both the helical domain and catalytic domain oncogenic mutants with relation to p110 phosphorylation. All other isoforms also showed elevated p110 phosphorylation (although not statistically significant). We conclude that the previously reported increase in cell signalling and oncogenic-like transformation in response to p110 NTT is not mediated via an increase in the lipid kinase activity of PI 3-K, but may be mediated by increased p110 autophosphorylation and/or other, as yet unidentified, intracellular protein/protein interactions. We further observe that tagged recombinant protein is suitable for use in in vitro lipid kinase screens to identify PI 3-K inhibitors; however, we recommend that in vivo (including intracellular) experiments and investigations into the protein kinase activity of PI 3-K should be conducted with untagged constructs.

Targeting the protein-protein interaction between IRS1 and mutant p110α for cancer therapy

Phosphoinositide-3-kinase, catalytic, alpha polypeptide, which encodes the catalytic p110α subunit of phosphatidylinositol 3-kinase α, is the most frequently mutated oncogene in human cancers. Targeting mutant p110α holds great promise for cancer therapy. However, it is challenging to develop p110α isoform-specific inhibitors. Most p110α mutations occur at two hot spot regions: an acidic cluster (E542, E545, and Q546) in the helical domain and a histidine residue (H1047) in the kinase domain. We recently discovered that p110α helical domain mutant proteins, but not the kinase domain mutant proteins, directly associate with insulin receptor substrate 1 (IRS1). Moreover, we demonstrated that disruption of protein-protein interaction between p110α helical domain mutant and IRS1 inhibits the growth of tumors with such mutations. The direct protein interaction between IRS1 and p110α helical domain mutants may provide a more accessible target for developing novel precision cancer therapy.

Obesity and melanoma: exploring molecular links

Obesity is now a major health problem due to its rapidly increasing incidence worldwide and severe consequences. Among many conditions associated with obesity are some cancers including melanoma. Both genetic defects and environmental risk factors are involved in the carcinogenesis of melanoma. Activation of multiple signal pathways such as the PI3K/Akt and MAPK pathways are necessary for the initiation of melanoma. Activation of the MAPK pathway as a result of activating mutations in BRAF is commonly seen in melanoma though it alone is not sufficient to cause malignant transformation of melanocytes. Obesity can result in the activation of many signal pathways including PI3K/Akt, MAPK, and STAT3. The activation of these pathways may have a synergistic effect with the genetic defects thereby increasing the incidence of melanoma.

BAY 80-6946 is a highly selective intravenous PI3K inhibitor with potent p110α and p110δ activities in tumor cell lines and xenograft models

Because of the complexity derived from the existence of various phosphoinositide 3-kinase (PI3K) isoforms and their differential roles in cancers, development of PI3K inhibitors with differential pharmacologic and pharmacokinetic profiles would allow best exploration in different indications, combinations, and dosing regimens. Here, we report BAY 80-6946, a highly selective and potent pan-class I PI3K inhibitor with sub-nanomolar IC50s against PI3Kα and PI3Kδ. BAY 80-6946 exhibited preferential inhibition (about 10-fold) of AKT phosphorylation by PI3Kα compared with PI3Kβ in cells. BAY 80-6946 showed superior antitumor activity (>40-fold) in PIK3CA mutant and/or HER2 overexpression as compared with HER2-negative and wild-type PIK3CA breast cancer cell lines. In addition, BAY 80-6946 revealed potent activity to induce apoptosis in a subset of tumor cells with aberrant activation of PI3K as a single agent. In vivo, single intravenous administration of BAY 80-6946 exhibited higher exposure and prolonged inhibition of pAKT levels in tumors versus plasma. BAY 80-6946 is efficacious in tumors with activated PI3K when dosed either continuously or intermittently. Thus, BAY 80-6946 induced 100% complete tumor regression when dosed as a single agent every second day in rats bearing HER2-amplified and PIK3CA-mutated KPL4 breast tumors. In combination with paclitaxel, weekly dosing of BAY 80-6946 is sufficient to reach sustained response in all animals bearing patient-derived non-small cell lung cancer xenografts, despite a short plasma elimination half-life (1 hour) in mice. Thus, BAY 80-6946 is a promising agent with differential pharmacologic and pharmacokinetic properties for the treatment of PI3K-dependent human tumors.

Phase I safety, pharmacokinetic, and pharmacodynamic study of SAR245408 (XL147), an oral pan-class I PI3K inhibitor, in patients with advanced solid tumors

PURPOSE

SAR245408 is a pan-class I phosphoinositide 3-kinase (PI3K) inhibitor. This phase I study determined the maximum tolerated dose (MTD) of two dosing schedules [first 21 days of a 28-day period (21/7) and continuous once-daily dosing (CDD)], pharmacokinetic and pharmacodynamic profiles, and preliminary efficacy.

EXPERIMENTAL DESIGN

Patients with refractory advanced solid malignancies were treated with SAR245408 using a 3 + 3 design. Pharmacokinetic parameters were determined after single and repeated doses. Pharmacodynamic effects were evaluated in plasma, hair sheath cells, and skin and tumor biopsies.

RESULTS

Sixty-nine patients were enrolled. The MTD of both schedules was 600 mg; dose-limiting toxicities were maculopapular rash and hypersensitivity reaction. The most frequent drug-related adverse events included dermatologic toxicities, diarrhea, nausea, and decreased appetite. Plasma pharmacokinetics showed a median time to maximum concentration of 8 to 22 hours, mean terminal elimination half-life of 70 to 88 hours, and 5- to 13-fold accumulation after daily dosing (first cycle). Steady-state concentration was reached between days 15 and 21, and exposure was dose-proportional with doses up to 400 mg. SAR245408 inhibited the PI3K pathway (∼40%-80% reduction in phosphorylation of AKT, PRAS40, 4EBP1, and S6 in tumor and surrogate tissues) and, unexpectedly, also inhibited the MEK/ERK pathway. A partial response was seen in one patient with advanced non-small cell lung cancer. Eight patients were progression-free at 6 months. Pharmacodynamic and clinical activity were observed irrespective of tumor PI3K pathway molecular alterations.

CONCLUSIONS

SAR245408 was tolerable at doses associated with PI3K pathway inhibition. The recommended phase II dose of the capsule formulation is 600 mg administered orally with CDD.

Exploring novel therapeutic targets in GIST: focus on the PI3K/Akt/mTOR pathway

Gastrointestinal stromal tumors (GISTs) are the most common soft tissue sarcoma, and most feature abnormalities in two genes encoding the receptor tyrosine kinases (RTKs), KIT, and PDGFRA. The RTK inhibitor imatinib revolutionized treatment in GIST; however, drug resistance remains a challenge. Constitutive autophosphorylation of RTKs is linked to phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway hyperactivation, which is central to oncogenic signaling, and known to be dysregulated in GIST. Preclinical experiments have confirmed that inhibiting the PI3K/Akt/mTOR pathway is a rational target for therapy. Early studies using mTOR inhibitors have shown limited success, which may be due to the activation of Akt that occurs following mTORC1 inhibition. Therefore, targeting PI3K or Akt, which lie upstream of mTORC1, may translate into more complete pathway inhibition. Several treatment strategies are currently being developed in phase 1 and 2 clinical trials. Compounds currently in development include pan-Class I PI3K inhibitors, dual PI3K/mTOR inhibitors, and Akt inhibitors. The aim of this review is to highlight the evidence for targeting PI3K/Akt/mTOR-dependent mechanisms in GIST and to evaluate the existing preclinical and clinical data supporting this strategy.

Frequency, characterization, and prognostic analysis of PIK3CA gene mutations in Chinese esophageal squamous cell carcinoma

PIK3CA gene mutations are found in numerous cancers but correlate differently with prognosis. Although the frequency of PIK3CA gene mutation in esophageal squamous cell carcinoma (ESCC) has been previously studied, a prognostic analysis has not been reported. Ninety-six surgically resected ESCC tissues were collected from Chinese patients and DNA was extracted. Gene mutations in PIK3CA (exons 9 and 20), EGFR (exons 18, 19, 20 and 21), KRAS (exons 2 and 3), and BRAF (exons 11 and 15) were screened using mutant-enriched liquid chip technology. PIK3CA gene mutations were identified in 12 of 96 ESCC cases (12.5%). No mutations were identified in EGFR, KRAS or BRAF genes in this study. Correlations between clinicopathological features and PIK3CA mutation status were analyzed and finally, patient survival information was used to determine the prognostic significance of PIK3CA mutation. Interestingly, the frequency of PIK3CA mutation was higher in female ESCC patients (31.3%, 5/16) than in males (8.8%, 7/80), and higher in patients with non-lymph node metastasis (19.6%, 10/51, P = .013) than in patients with lymph node metastasis (4.4%, 2/45, P = .025). Furthermore, patients with PIK3CA-mutated tumors showed a trend towards favorable overall survival (P = .085) but not disease-free survival (P = .238), suggesting that PIK3CA gene status may be a favorable predictive marker in ESCC patients.

High level of p37δ-mRNA relative to p110δ-mRNA in neuroblastoma tumors correlates with poor patient survival

Alterations in the PI3K/Akt pathway, a pathway that promotes proliferation and oncogenic transformation, are common in various cancers. In neuroblastoma, activation of Akt is correlated with aggressive disease although mutations in genes of this pathway are rare. Previous findings include a few mutations in PIK3CD, the gene encoding PI3K catalytic subunit delta, p110δ. We recently reported that an alternatively spliced form of p110δ, called p37δ, had cell proliferative properties and was over-expressed in ovarian and colorectal tumors. Here, we investigated p37δ in neuroblastoma primary tumors of different stages using qPCR (TaqMan) for gene expression analysis (46 samples) and Western blot for protein analysis (22 samples). Elevated levels of both p37δ-mRNA and p110δ-mRNA were detected in metastasizing neuroblastoma tumors compared to normal adrenal gland (P < 0.05), and higher expression of p37δ-mRNA relative to p110δ-mRNA in neuroblastoma non-survivor patients compared to survivors (P < 0.01). p37δ-Protein levels but not p110δ levels correlated with increased pAKT(T308) and pERK levels. The p37δ-mRNA levels did not correlate with the protein levels, indicating major regulation at the translational/protein level. Deregulation of signaling pathways is a hallmark of cancer development. Here, we show that p37δ, a kinase-dead isoform of the PI3K catalytic subunit p110δ, is over-expressed in neuroblastoma tumors, and that it correlates with the activation of both PI3K/Akt- and RAS-signaling pathways.

PI3K in cancer-stroma interactions: bad in seed and ugly in soil

Over the past decade the phosphoinositide-3 kinase (PI3K) signaling pathway emerged as an important player for tumor initiation and growth and, currently, PI3K inhibition constitutes a promising therapeutic approach for solid and hematological tumors. Beside its role in tumor cell evolution, PI3K signaling also provides integral functions for noncancerous cells that reside in healthy tissues surrounding the tumor, also referred as tumor microenvironment (TME). This review will address how PI3K signaling participates to the tumorigenic process and discuss the interaction between tumor cells and the surrounding TME, with particular focus on the role of PI3Ks in tumor-associated immune responses, tumor angiogenesis and metastasis formation.

Initiation of human astrovirus type 1 infection was blocked by inhibitors of phosphoinositide 3-kinase

BACKGROUND

Upon initial contact with a virus, host cells activate a series of cellular signaling cascades that facilitate viral entry and viral propagation within the cell. Little is known about how the human astrovirus (HAstV) exploits signaling cascades to establish an infection in host cells. Recent studies showed that activation of extracellular signal-regulated kinase 1/2 (ERK1/2) is important for HAstV infection, though the involvement of other signaling cascades remains unclear.

METHODS

A panel of kinase blockers was used to search for cellular signaling pathways important for HAstV1 infection. To determine their impact on the infectious process, we examined viral gene expression, RNA replication, and viral RNA and capsid protein release from host cells.

RESULTS

Inhibitors of phosphoinositide 3-kinase (PI3K) activation interfered with the infection, independent of their effect on ERK 1/2 activation. Activation of the PI3K signaling cascade occurred at an early phase of the infection, judging from the timeframe of Akt phosphorylation. PI3K inhibition at early times, but not at later times, blocked viral gene expression. However, inhibiting the downstream targets of PI3K activation, Akt and Rac1, did not block infection. Inhibition of protein kinase A (PKA) activation was found to block a later phase of HAstV1 production.

CONCLUSIONS

Our results reveal a previously unknown, essential role of PI3K in the life cycle of HAstV1. PI3K participates in the early stage of infection, possibly during the viral entry process. Our results also reveal the role of PKA in viral production.

Gain of interaction with IRS1 by p110α-helical domain mutants is crucial for their oncogenic functions

PIK3CA, which encodes the p110α catalytic subunit of phosphatidylinositol 3-kinase α, is frequently mutated in human cancers. Most of these mutations occur at two hot-spots: E545K and H1047R located in the helical domain and the kinase domain, respectively. Here, we report that p110α E545K, but not p110α H1047R, gains the ability to associate with IRS1 independent of the p85 regulatory subunit, thereby rewiring this oncogenic signaling pathway. Disruption of the IRS1-p110α E545K interaction destabilizes the p110α protein, reduces AKT phosphorylation, and slows xenograft tumor growth of a cancer cell line expressing p110α E545K. Moreover, a hydrocarbon-stapled peptide that disrupts this interaction inhibits the growth of tumors expressing p110α E545K.

PIK3CA gene mutation associated with poor prognosis of lung adenocarcinoma

Purpose

PIK3CA gene mutations have been detected in many malignancies, but the frequency of different mutations and their role in the carcinogenesis of lung adenocarcinoma are still unclear. The purpose of this study was to explore the clinical pathological impact and prognostic implications of PIK3CA mutations in lung adenocarcinoma.

Methods

Five common PIK3CA mutations (E542K, E545K, and E545D mutation in exon 9, H1047R and H1047L mutation in exon 20) were detected by amplification refractory mutation system (ARMS) allele-specific polymerase chain reaction (PCR), in 122 patients with lung adenocarcinoma. The relationships were studied between these mutations and various clinicopathologic variables (age, lymph node status, distant metastasis, clinicopathologic stage, smoking status, and progression-free survival).

Results

In total, 25 mutations were identified, of which 24 mutations were clustered in exon 20, and one mutation in exon 9. The most common mutations were H1047R (18 out of the 122 patients, 14.8%) in exon 20. PIK3CA-mutated tumors were more frequently found in patients with lymph node positive metastasis status (P < 0.05). There was no significant association between PIK3CA mutations and age, distant metastasis, smoking status, or clinicopathologic stage. However, mutations were found less frequently in the early clinicopathologic stage patients (six in 50 cases, 12%) than in advanced stage (19 in 72 cases, 26.4%). Higher frequency of H1047R mutations was associated with poor prognosis, and this association reached statistical significance (P < 0.05).

Conclusion

Our data indicate that the PIK3CA mutations H1047R and H1047L are significant genetic alterations in lung adenocarcinoma. Among lung adenocarcinoma patients who underwent curative resection, PIK3CA mutations were associated with shorter progression-free survival. Our findings demonstrated a significant role of PIK3CA in lung adenocarcinoma.

Antagonism between FOXO and MYC Regulates Cellular Powerhouse

Alterations in cellular metabolism are a key feature of the transformed phenotype. Enhanced macromolecule synthesis is a prerequisite for rapid proliferation but may also contribute to induction of angiogenesis, metastasis formation, and tumor progression, thereby leading to a poorer clinical outcome. Metabolic adaptations enable cancer cells to survive in suboptimal growth conditions, such as the limited supply of nutrient and oxygen often found in the tumor microenvironment. Metabolic changes, including activation of glycolysis and inhibition of mitochondrial ATP production, are induced under hypoxia to promote survival in low oxygen. FOXO3a, a transcription factor that is inhibited by the phosphatidylinositol 3-kinase/Akt pathway and is upregulated in hypoxia, has emerged as an important negative regulator of MYC function. Recent studies have revealed that FOXO3a acts as a negative regulator of mitochondrial function through inhibition of MYC. Ablation of FOXO3a prevents the inhibition of mitochondrial function induced by hypoxia and results in enhanced oxidative stress. This review will focus on the antagonism between FOXO3a and MYC and discuss their role in cellular bioenergetics, reactive oxygen metabolism, and adaptation to hypoxia, raising questions about the role of FOXO proteins in cancer.

Outcome impact of PIK3CA mutations in HER2-positive breast cancer patients treated with trastuzumab

Background:

Phosphatidylinositol 3-kinase (PI3K) pathway activation has been suggested to negatively influence response to anti-HER2 therapy in breast cancer patients. The present study focused on mutations of the PIK3CA gene, encoding one of the two PI3K subunits.

Methods:

PIK3CA mutations were assessed by direct sequencing in 80 HER2-positive patients treated with 1 year of trastuzumab. All patients preoperatively received four cycles of anthracycline-based chemotherapy, followed by four cycles of docetaxel and 1 year of trastuzumab, starting either before surgery with the first cycle of docetaxel and continuing after surgery (neoadjuvant trastuzumab arm, n=43), or only after surgery (adjuvant trastuzumab arm, n=37).

Results:

PIK3CA mutations were found in 17 tumours (21.3%). Better disease-free survival (DFS) was observed in patients with PIK3CA wild-type compared with mutated tumours (P=0.0063). By combining PIK3CA status and treatment arms, four separate prognostic groups with significantly different DFS (P=0.0013) were identified.

Conclusion:

These results confirm that the outcome of HER2-positive patients treated with trastuzumab is significantly worse in patients with PIK3CA-mutated compared with wild-type tumours.

Molecular mechanisms of natural killer cell activation in response to cellular stress

Protection against cellular stress from various sources, such as nutritional, physical, pathogenic, or oncogenic, results in the induction of both intrinsic and extrinsic cellular protection mechanisms that collectively limit the damage these insults inflict on the host. The major extrinsic protection mechanism against cellular stress is the immune system. Indeed, it has been well described that cells that are stressed due to association with viral infection or early malignant transformation can be directly sensed by the immune system, particularly natural killer (NK) cells. Although the ability of NK cells to directly recognize and respond to stressed cells is well appreciated, the mechanisms and the breadth of cell-intrinsic responses that are intimately linked with their activation are only beginning to be uncovered. This review will provide a brief introduction to NK cells and the relevant receptors and ligands involved in direct responses to cellular stress. This will be followed by an in-depth discussion surrounding the various intrinsic responses to stress that can naturally engage NK cells, and how therapeutic agents may induce specific activation of NK cells and other innate immune cells by activating cellular responses to stress.

Single copies of mutant KRAS and mutant PIK3CA cooperate in immortalized human epithelial cells to induce tumor formation

The selective pressures leading to cancers with mutations in both KRAS and PIK3CA are unclear. Here, we show that somatic cell knockin of both KRAS G12V and oncogenic PIK3CA mutations in human breast epithelial cells results in cooperative activation of the phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways in vitro, and leads to tumor formation in immunocompromised mice. Xenografts from double-knockin cells retain single copies of mutant KRAS and PIK3CA, suggesting that tumor formation does not require increased copy number of either oncogene, and these results were also observed in human colorectal cancer specimens. Mechanistically, the cooperativity between mutant KRAS and PIK3CA is mediated in part by Ras/p110α binding, as inactivating point mutations within the Ras-binding domain of PIK3CA significantly abates pathway signaling. In addition, Pdk1 activation of the downstream effector p90RSK is also increased by the combined presence of mutant KRAS and PIK3CA. These results provide new insights into mutant KRAS function and its role in carcinogenesis.