Class I PI3 kinase inhibition by the pyridinylfuranopyrimidine inhibitor PI-103 enhances tumor radiosensitivity

Cell signaling initiated at the epidermal growth factor receptor (EGFR), RAS oncoproteins, or PI3K contributes to a common pathway that promotes tumor survival after radiation-induced DNA damage. Inhibition of signaling at the level of EGFR, RAS, and PI3K has been tested, but clinical applicability has been shown only at the level of the EGFR or by inhibiting RAS indirectly with prenyltransferase inhibitors. Inhibition of PI3K with LY294002 or wortmannin lacks specificity and has shown unacceptable toxicity in preclinical studies. We previously showed that inhibiting class I PI3K expression with siRNA resulted in enhanced radiation killing of tumor cells. Here, we tested the possibility of achieving specific tumor cell radiosensitization with a pharmacologic inhibitor of class I PI3K, the pyridinylfuranopyrimidine inhibitor PI-103. Our results show that inhibiting PI3K activity reduces phosphorylation of AKT at serine 473. Reduced survival is seen in cells with AKT activation and seems preferential for tumor cells over cells in which AKT activity is not elevated. Reduced survival is accompanied by persistence of DNA damage as evidenced by persistence of gamma H2AX and Rad 51 foci after irradiation in the presence of the inhibitor. Reduced survival does not result from cell cycle redistribution during the PI-103 treatment intervals tested, although combining PI-103 treatment with radiation enhances the G(2)-M delay observed after irradiation. These results indicate that pharmacologic inhibitors with enhanced specificity for class I PI3K may be of benefit when combined with radiotherapy.     

抑制Notch和PI3K/Akt信号通路对食管腺癌细胞增殖、侵袭及迁移的影响

目的 探讨Notch和PI3K/Akt两条信号通路对人食管腺癌细胞OE33增殖、侵袭及迁移能力的影响及两条信号通路之间的联系。方法 应用Notch信号通路阻滞剂DAPT和PI3K/Akt信号通路阻滞剂LY294002分别单独和联合处理OE33细胞,设置对照组;Western blot和实时定量PCR法检测OE33细胞中NICD、Hes1、p-Akt、PTEN蛋白和mRNA的表达变化;CCK-8法检测细胞的增殖抑制率;划痕实验用于检测细胞迁移能力的变化;Transwell细胞侵袭实验用于检测细胞的侵袭能力变化。结果 Notch1通路阻滞剂DAPT能减低Notch1通路相关蛋白NICD和Hes1的表达,并能提高p-Akt蛋白的表达;PI3K/Akt路阻滞剂LY294002不仅使p-Akt的蛋白表达水平减低,还能降低Hes1的蛋白表达水平,同时使NICD的蛋白和Hes1的mRNA表达水平增高。DAPT和LY294002联合处理组的NICD、Hes1、p-Akt的蛋白表达均较空白对照组和单药处理组降低,同时细胞的增殖、迁移和转移能力亦明显减弱。各处理组中PTEN的蛋白和mRNA表达水平较对照组均有一定程度的升高。结论 Notch和PI3K/Akt两条信号通路在食管腺癌细胞OE33中可能存在串话, 同时抑制这两种信号通路能有效的抑制OE33的增殖、侵袭及迁移。     

Combined therapy with RAD001 e BEZ235 overcomes resistance of PET immortalized cell lines to mTOR inhibition

Pancreatic endocrine tumors (PETs) are characterised by an indolent behaviour in terms of tumor growth. However, most patients display metastasis at diagnosis and no cure is currently available. Since the PI3K/AKT/mTOR axis is deregulated in PETs, the mTOR inhibitor RAD001 represents the first line treatment. Nevertheless, some patients do not respond to treatments and most acquire resistance. Inhibition of mTOR leads to feedback re-activation of PI3K activity, which may promote resistance to RAD001. Thus, PI3K represents a novel potential target for PETs. We tested the impact of three novel PI3K inhibitors (BEZ235, BKM120 and BYL719) on proliferation of PET cells that are responsive (BON-1) or unresponsive (QGP-1) to RAD001. BEZ235 was the most efficient in inhibiting proliferation in PET cells. Furthermore, combined treatment with BEZ235 and RAD001 exhibited synergic effects and was also effective in BON-1 that acquired resistance to RAD001 (BON-1 RR). Analysis of PI3K/AKT/mTOR pathway showed that RAD001 and BEZ235 only partially inhibited mTOR-dependent phosphorylation of 4EBP1. By contrast, combined therapy with the two inhibitors strongly inhibited phosphorylation of 4EBP1, assembly of the translational initiation complex and protein synthesis. Thus, combined treatment with BEZ235 may represent suitable therapy to counteract primary and acquired resistance to RAD001 in PETs.     

Checkpoint kinase1 (CHK1) is an important biomarker in breast cancer having a role in chemotherapy response

Background:

Checkpoint kinase1 (CHK1), which is a key component of DNA-damage-activated checkpoint signalling response, may have a role in breast cancer (BC) pathogenesis and influence response to chemotherapy. This study investigated the clinicopathological significance of phosphorylated CHK1 (pCHK1) protein in BC.

Method:

pCHK1 protein expression was assessed using immunohistochemistry in a large, well-characterized annotated series of early-stage primary operable invasive BC prepared as tissue microarray (n=1200).

Result:

pCHK1 showed nuclear and/or cytoplasmic expression. Tumours with nuclear expression showed positive associations with favourable prognostic features such as lower grade, lower mitotic activity, expression of hormone receptor and lack of expression of KI67 and PI3K (P<0.001). On the other hand, cytoplasmic expression was associated with features of poor prognosis such as higher grade, triple-negative phenotype and expression of KI67, p53, AKT and PI3K. pCHK1 expression showed an association with DNA damage response (ATM, RAD51, BRCA1, KU70/KU80, DNA-PKCα and BARD1) and sumoylation (UBC9 and PIASγ) biomarkers. Subcellular localisation of pCHK1 was associated with the expression of the nuclear transport protein KPNA2. Positive nuclear expression predicted better survival outcome in patients who did not receive chemotherapy in the whole series and in ER-positive tumours. In ER-negative and triple-negative subgroups, nuclear pCHK1 predicted shorter survival in patients who received cyclophosphamide, methotrexate and 5-florouracil chemotherapy.

Conclusions:

Our data suggest that pCHK1 may have prognostic and predictive significance in BC. Subcellular localisation of pCHK1 protein is related to its function.     

Genomic evolution in Barrett's adenocarcinoma cells: critical roles of elevated hsRAD51, homologous recombination and Alu sequences in the genome

A prominent feature of most cancers including Barrett's adenocarcinoma (BAC) is genetic instability, which is associated with development and progression of disease. In this study, we investigated the role of recombinase (hsRAD51), a key component of homologous recombination (HR)/repair, in evolving genomic changes and growth of BAC cells. We show that the expression of RAD51 is elevated in BAC cell lines and tissue specimens, relative to normal cells. HR activity is also elevated and significantly correlates with RAD51 expression in BAC cells. The suppression of RAD51 expression, by short hairpin RNA (shRNA) specifically targeting this gene, significantly prevented BAC cells from acquiring genomic changes to either copy number or heterozygosity (P<0.02) in several independent experiments employing single-nucleotide polymorphism arrays. The reduction in copy-number changes, following shRNA treatment, was confirmed by Comparative Genome Hybridization analyses of the same DNA samples. Moreover, the chromosomal distributions of mutations correlated strongly with frequencies and locations of Alu interspersed repetitive elements on individual chromosomes. We conclude that the hsRAD51 protein level is systematically elevated in BAC, contributes significantly to genomic evolution during serial propagation of these cells and correlates with disease progression. Alu sequences may serve as substrates for elevated HR during cell proliferation in vitro, as they have been reported to do during the evolution of species, and thus may provide additional targets for prevention or treatment of this disease.     

Cranberry proanthocyanidins inhibit esophageal adenocarcinoma in vitro and in vivo through pleiotropic cell death induction and PI3K/AKT/mTOR inactivation

Cranberries are rich in bioactive constituents known to improve urinary tract health and more recent evidence supports cranberries possess cancer inhibitory properties. However, mechanisms of cancer inhibition by cranberries remain to be elucidated, particularly in vivo. Properties of a purified cranberry-derived proanthocyanidin extract (C-PAC) were investigated utilizing acid-sensitive and acid-resistant human esophageal adenocarcinoma (EAC) cell lines and esophageal tumor xenografts in athymic NU/NU mice. C-PAC induced caspase-independent cell death mainly via autophagy and low levels of apoptosis in acid-sensitive JHAD1 and OE33 cells, but resulted in cellular necrosis in acid-resistant OE19 cells. Similarly, C-PAC induced necrosis in JHAD1 cells pushed to acid-resistance via repeated exposures to an acidified bile cocktail. C-PAC associated cell death involved PI3K/AKT/mTOR inactivation, pro-apoptotic protein induction (BAX, BAK1, deamidated BCL-xL, Cytochrome C, PARP), modulation of MAPKs (P-P38/P-JNK) and G_2-M cell cycle arrest in vitro. Importantly, oral delivery of C-PAC significantly inhibited OE19 tumor xenograft growth via modulation of AKT/mTOR/MAPK signaling and induction of the autophagic form of LC3B supporting in vivo efficacy against EAC for the first time. C-PAC is a potent inducer of EAC cell death and is efficacious in vivo at non-toxic behaviorally achievable concentrations, holding promise for preventive or therapeutic interventions in cohorts at increased risk for EAC, a rapidly rising and extremely deadly malignancy.     

Concurrent inhibition of PI3-Kinase and mTOR induces cell death in diffuse large B cell lymphomas,a mechanism involving down regulation of Mcl-1

Phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling is frequently dysregulated in diffuse large B cell lymphoma (DLBCL) including the favorable germinal centre B-cell (GCB) and the unfavorable activated B-cell (ABC) subtypes. mTOR promotes cap-dependent translation of proteins, like Mcl-1, through inhibitory phosphorylation of the eukaryotic translation initiation factor 4E binding protein 1 (4EBP1). Inhibition of mTOR by RAD001 reduces proliferation but fails to dephosphorylate 4EBP1 and to induce cell death in either DLBCL subtype. In contrast, concurrent inhibition of PI3K and mTOR with NVP-BEZ235 inhibits proliferation, dephosphorylates 4EBP1, and induces cells death, notably more pronounced in CGB cells. Small RNA interference identifies Mcl-1 as a crucial cell death mediator of both DLBCL subtypes. Inhibition of the PI3K/mTOR/4EBP1 by NVP-BEZ235 results in suppression of the cap-dependent translation initiation complex and concomitant downregulation of Mcl-1 in GCB cell lines. In ABC cell lines, this suppression is possibly compensated by NF-κB- or Pim kinase-mediated signaling.     

Suppression of esophageal tumor growth and chemoresistance by directly targeting the PI3K/AKT pathway

Esophageal cancer is the sixth most common cause of cancer-related deaths worldwide. Novel therapeutic intervention is urgently needed for this deadly disease. The functional role of PI3K/AKT pathway in esophageal cancer is little known. In this study, our results from 49 pairs of human esophageal tumor and normal specimens demonstrated that AKT was constitutively active in the majority (75.5%) of esophageal tumors compared with corresponding normal tissues. Inhibition of the PI3K/AKT pathway with specific inhibitors, wortmannin and {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002, significantly reduced Bcl-xL expression, induced caspase-3-dependent apoptosis, and repressed cell proliferation and tumor growth in vitro and in vivo without obvious toxic effects. Moreover, significantly higher expression level of p-AKT was observed in fluorouracil (5-FU)-resistant esophageal cancer cells. Inactivation of PI3K/AKT pathway markedly increased the sensitivity and even reversed acquired resistance of esophageal cancer cells to chemotherapeutic drugs in vitro. More importantly, the resistance of tumor xenografts derived from esophageal cancer cells with acquired 5-FU resistance to chemotherapeutic drugs was significantly abrogated by wortmannin treatment in animals. In summary, our data support PI3K/AKT as a valid therapeutic target and strongly suggest that PI3K/AKT inhibitors used in conjunction with conventional chemotherapy may be a potentially useful therapeutic strategy in treating esophageal cancer patients.     

MCL-1-independent mechanisms of synergy between dual PI3K/mTOR and BCL-2 inhibition in diffuse large B cell lymphoma

The PI3K/AKT/mTOR axis promotes survival and is a frequently mutated pathway in cancer. Yet, inhibitors targeting this pathway are insufficient to induce cancer cell death as single agents in some contexts, including diffuse large B cell lymphoma (DLBCL). In these situations, combinations with inhibitors targeting BCL-2 survival proteins (ABT-199 and ABT-263) may hold potential. Indeed, studies have demonstrated marked synergy in contexts where PI3K/mTOR inhibitors suppress expression of the pro-survival protein, MCL-1. In this study, we use BH3 profiling to confirm that BCL-2 and BCL-X_L support survival following PI3K pathway inhibition, and that the dual PI3K/mTOR inhibitor BEZ235 strongly synergizes with BCL-2 antagonists in DLBCL. However, we identify an alternative mechanism of synergy between PI3K/mTOR and BCL-2 inhibitors, independent of MCL-1 down-regulation. Instead, we show that suppression of AKT activation by BEZ235 can induce the mitochondrial accumulation of pro-apoptotic BAD and BIM, and that expression of a constitutively active form of AKT prevents sensitization to BCL-2 antagonism. Thus, our work identifies an additional mechanism of synergy between PI3K pathway inhibitors and BCL-2 antagonists that strengthens the rationale for testing this combination in DLBCL.     

Inhibition of activated phosphatidylinositol 3-kinase/AKT pathway in malignant pleural mesothelioma leads to G1 cell cycle arrest

Phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway plays pivotal roles in fundamental cellular functions including cell proliferation and cell survival. Its deregulation has been implicated in many types of human malignancies. We investigated the role of PI3K/AKT signaling pathway in human malignant pleural mesothelioma (MM). Here, we report that aberrant activation of the PI3K/AKT signaling pathway is associated with cell cycle progression in MM cells. Inhibition of the PI3K activity by its small molecule inhibitor LY294002 led to significant G1 cell cycle arrest and suppression of cell proliferation in all MM cell lines that we examined. In addition, we found that the protein level of p27Kip1 was up-regulated and the protein level of cyclin D1 was down-regulated following LY294002 treatment in those MM cell lines. However, no noticeable apoptosis induction was observed following 24 h of LY294002 treatment in those MM cell lines. These results confirm that the PI3K/AKT signaling pathway is aberrantly active and plays a critical role for the cell cycle progression in human MM cells.     

Equivalent benefit of mTORC1 blockade and combined PI3K-mTOR blockade in a mouse model of tuberous sclerosis

Background  

Tuberous sclerosis (TSC) is a hamartoma syndrome in which renal and lung tumors cause the greatest morbidity. Loss of either TSC1 or TSC2 in TSC hamartomas leads to activation of mTORC1 and suppression of AKT. Recent studies indicate that inhibition of mTORC1 with RAD001 (everolimus) leads to rebound activation of AKT, which could protect tumors from drug-induced cell death. Here we examine the potential benefit of inhibition of both mTOR and AKT signaling in a mouse model of TSC, using a dual pan class I PI3K/mTOR catalytic small molecule inhibitor NVP-BEZ235.     

CCR9 mediates PI3K/AKT‐dependent antiapoptotic signals in prostate cancer cells and inhibition of CCR9‐CCL25 interaction enhances the cytotoxic effects of etoposide

Despite recent advances in treatment and management of prostate cancer (PCa), it remains the second leading cause of cancer‐related deaths among men in the US. Chemotherapy is one of the treatment alternatives for hormone refractory metastatic PCa. However, current chemotherapeutic regimens provide palliative benefit but relatively modest survival advantage primarily due to chemo‐resistance and upregulated antiapoptotic machineries in PCa cells. Therefore, blocking the mechanisms responsible for suppression of apoptosis might improve current chemotherapeutic regimens. In this study, we show that CC chemokine receptor‐9 (CCR9) and its natural ligand CCL25 interaction upregulates antiapoptotic proteins (i.e., PI3K, AKT, ERK1/2 and GSK‐3β) and downregulate activation of caspase‐3 in PCa cells. Significant downregulation of these CCR9‐mediated antiapoptotic proteins in the presence of a PI3K inhibitor (wortmannin), further suggests that the antiapoptotic action of CCR9 is primarily regulated through PI3K. Furthermore, the cytotoxic effect of etoposide was significantly inhibited in the presence of CCL25, and this inhibitory effect of CCL25 was abrogated when CCR9‐CCL25 interaction was blocked using anti‐CCR9 monoclonal antibodies. In conformation to these in vitro studies, significant reduction in tumor burden was found in mice receiving CCL25 neutralizing antibodies and etoposide together as compared to both as a single agent. These results suggest that the CCR9‐CCL25 axis mediates PI3K/AKT‐dependent antiapoptotic signals in PCa cells and could be a possible reason for low apoptosis and modest chemotherapeutic response. Therefore, targeting CCR9‐CCL25 axis with cytotoxic agents may provide better therapeutic outcomes than using cytotoxic agents alone.     

胰腺癌组织高表达血小板反应蛋白2 的预后意义及其对癌细胞增殖和迁移的影响

[摘要] 目的：探索血小板反应蛋白2（thrombospondin 2,THBS2）表达对胰腺癌患者的预后意义及对胰腺癌ASPC-1 细胞增殖和迁移的影响,并探讨可能的分子机制。方法：利用数据库分析THBS2 在胰腺癌组织中的表达情况及其对患者整体生存率的影响。Wb实验检测THBS2 在胰腺癌ASPC-1 细胞中的表达,RNA干扰技术敲低ASPC-1 细胞中THBS2 的表达后,采用MTT实验以及Transwell 实验检测敲低THBS2 对于细胞增殖和迁移能力的影响;Wb技术检测对ASPC-1 细胞中MMP、E-钙黏蛋白、AKT以及PI3K蛋白表达的影响。结果：THBS2 在胰腺癌组织中的表达显著高于正常胰腺组织中的表达(P<0.01),且THBS2 的高表达会导致胰腺癌患者整体生存率的下降。THBS2 在ASPC-1 细胞中表达上调,干扰THBS2 的表达后ASPC-1 细胞的增殖(P<0.01)和迁移能力(P<0.01)均显著下降,细胞内AKT以及PI3K的表达显著下调(P<0.01)。结论：THBS2 在胰腺癌组织和细胞中高表达,且与患者的预后情况呈负相关,其机制可能是通过调控AKT/PI3K信号通路而调节ASPC-1细胞的增殖和迁移。     

Overexpression of AKT2/protein kinase Bbeta leads to up-regulation of beta1 integrins,increased invasion,and metastasis of human breast and ovarian cancer cells

To determine how AKT2 might contribute to tumor cell progression, a full-length, wild-type, human AKT2/protein kinase B (PKB)beta cDNA was transfected into a panel of eight human breast and ovarian cancer cells. AKT2 transfectants demonstrated increased adhesion and invasion through collagen IV because of up-regulation of beta1 integrins. In addition, AKT2 cells were more metastatic than control cells in vivo. Increased invasion by AKT2 was blocked by preincubation with an anti-beta1 integrin function blocking antibody, exposure to wortmannin, and by expression of phosphatase and tensin homologue tumor suppressor (PTEN). Confocal microscopy performed on transfected human breast cancer cells showed that unlike AKT1, AKT2 protein predominantly localized adjacent to the collagen IV matrix during cellular attachment. Overexpression of AKT2, but not AKT1 or AKT3, was sufficient to duplicate the invasive effects of phosphoinositide 3-OH kinase (PI3-K) transfected in breast cancer cells. Furthermore, expression of kinase dead AKT2(181 amino acid methionine [M]), and not kinase dead AKT1(179M) or AKT3(177M), was capable of blocking invasion induced by either human epidermal growth factor receptor-2 (HER-2) overexpression or by activation of PI3-K. Taken together, these data indicate that AKT2 mediates PI3-K-dependent effects on adhesion, motility, invasion, and metastasis in vivo.     

miR-182激活PI3K/AKT信号通路促进肝癌HepG2细胞增殖、侵袭和迁移的机制研究

目的:探讨miR-182通过PI3K/AKT信号通路对肝癌HepG2细胞增殖、侵袭和迁移的影响及其机制。方法:将体外培养的HepG2细胞分为对照组(未转染)、阴性组(转染阴性对照)、模拟物组(转染miR-182模拟物)和模拟物+抑制剂组(转染miR-182模拟物后,加入PI3K/AKT信号通路抑制剂LY294002),采用RT-PCR检测各组细胞中miR-182的表达水平,Western blot检测各组细胞中PI3K/AKT信号通路相关蛋白PI3K、p-PI3K、AKT、p-AKT和MMP-9、c-Myc、VEGF蛋白的表达,采用MTT法、克隆形成实验和Transwell小室分别检测各组细胞的增殖、侵袭和迁移能力。结果:与对照组相比,模拟物组细胞的存活率、克隆形成率和侵袭细胞数、迁移细胞数均明显升高,细胞中p-PI3K、p-AKT和MMP-9、c-Myc、VEGF蛋白的表达水平也均明显上升(P<0.05);而阴性组和对照组细胞相比无显著性差异(P>0.05)。与模拟物组相比,模拟物+抑制剂组细胞的存活率、克隆形成率和侵袭细胞数、迁移细胞数明显降低,细胞中p-PI3K、p-AKT和MMP-9、c-Myc、VEGF蛋白的表达水平也均明显下降(P<0.05)。结论:miR-182可通过激活PI3K/AKT信号通路上调MMP-9、c-Myc、VEGF蛋白的表达促进肝癌细胞的增殖、侵袭和迁移。