Expression Of P110β Research Articles

Research on Mechanism of Nanometer Colloidal Particles of Prostate Specific Membrane Aptamer A10 (PSMA-a10)/TGX221 in Restraining the Transplantation Tumor of Rats with Prostate Cancer (PCa)

This study assesses the effect of nanometer colloidal particles of PSMA-a10/TGX22 1 on the transplantation tumor of rats with prostate cancer (PCa). 26 rats with PCa were divided into PPG group, exposed TGX221 group and nanometer TGX221 group followed by analysis of the growth of transplantation tumor, cell apoptotic rate by flow cytometry, and the expression of p110β and Bcl-2 by RT-PCR and Western Blot. Nanometer TGX221 group and exposed TGX221 group showed smaller tumor volume than in PPG group on day 13 after intervention with significant difference of tumor volume between nanometer TGX221 group and exposed TGX221 group on day 7. The inhibiting rate of tumor growth in exposed TGX221 group was less than that in nanometer TGX221 group. However, nanometer TGX221 group presented higher apoptotic rate than other two groups. The level of p110β and Bcl-2 in nanometer TGX221 group was declined gradually with significant differences compared to other two groups. In conclusion, the nanometer colloidal particles of PSMA-a10/TGX221 have promising tumor-targeted specificity possibly through inhibition of Bcl-2 and the activity of p110β, leading to restrained PCa growth.

Isoform‐selective PI3‐kinase Inhibition Confers Partial Resilience to Cocaine Cessation‐induced Anxiety‐like Behavior

Phosphoinositide 3‐kinase (PI3K) is a multi‐subunit signaling complex that phosphorylates phosphoinositides, membrane‐embedded second messengers that are critical for synaptic and structural plasticity of neurons. Cocaine potentiates PI3K‐Akt‐mTOR cascade activity, and this activation persists beyond the period of drug exposure. The PI3K p110β isoform is neuronally enriched and able to control PI3K signal propagation, allowing for manipulation of PI3K activity in a more targeted manner than broad‐spectrum PI3K inhibition. Cessation of cocaine use triggers anxiety‐like behavior in humans and rodent models, and anxiety can be a causal factor in relapse. Here, we used viral‐mediated gene silencing to reduce expression of p110β in the dorsomedial prefrontal cortex (dmPFC). Isoform‐selective PI3K inhibition mitigated anxiety‐like behavior triggered by acute cocaine. Interestingly, however, a history of repeated cocaine exposure occluded this resilience, presenting an opportunity to compare immediate‐early gene expression between cocaine‐vulnerable and cocaine‐resilient mice. We examined 22 brain regions and found that resilient mice – those displaying less anxiety‐like behavior – displayed lower immediate‐early gene expression in the claustrum and lateral hypothalamus. We next found that chemogenetic stimulation of the claustrum induced anxiety‐like behavior. Future studies will determine whether suppressing p110β in the dmPFC combats anxiety‐like behavior via connections with the claustrum. Our findings suggest that isoform‐selective PI3K inhibition mitigates cocaine cessation‐elicited anxiety‐like behavior, likely via coordinated brain regions and circuits.

Distinct epithelial-to-mesenchymal transitions induced by PIK3CAH1047R and PIK3CB.

The most common PIK3CA mutation, producing the H1047R mutant of p110α, arises in myriad malignancies and is typically observed in low-grade breast tumours. In contrast, amplification is observed for wild-type PIK3CB, encoding p110β, and occurs at low frequency but in aggressive, high-grade metastatic tumours. We hypothesized that mutant p110αH1047R and wild-type p110β give rise to distinct transformed phenotypes. We show that p110αH1047R and wild-type p110β, but not wild-type p110α, transform MCF-10A cells and constitutively stimulate phosphoinositide 3-kinase (PI3K)-AKT pathway signalling. However, their resultant morphological transformed phenotypes are distinct. p110αH1047R induced an epithelial-to-mesenchymal transition (EMT) commensurate with SNAIL (also known as SNAI1) induction and loss of E-cadherin. Upon p110β expression, however, E-cadherin expression was maintained despite cells readily delaminating from epithelial sheets. Distinct from the prominent filopodia in p110αH1047R-expressing cells, p110β induced formation of lamellipodia, and these cells migrated with significantly greater velocity and decreased directionality. p110β-induced phenotypic alterations were accompanied by hyperactivation of RAC1; the dependency of transformation of p110β-binding to Rac1 revealed using a Rac1-binding mutant of p110β. Thus, PIK3CB amplification induces a transformed phenotype that is dependent upon a p110β-Rac1 signalling loop and is distinct from the transformed phenotype induced by p110αH1047R.

Oleic Acid Protects Against Insulin Resistance by Regulating the Genes Related to the PI3K Signaling Pathway.

Background: The effects of different types of fatty acids on the gene expression of key players in the IRS1/PI3K signaling pathway have been poorly studied. Material and Methods: We analyzed IRS1, p85α, and p110β mRNA expression and the fatty acid composition of phospholipids in visceral adipose tissue from patients with morbid obesity and from non-obese patients. Moreover, we analyzed the expression of those genes in visceral adipocytes incubated with oleic, linoleic, palmitic and dosahexaenoic acids. Results: We found a reduced IRS1 expression in patients with morbid obesity, independent of insulin resistance, and a reduced p110β expression in those with lower insulin resistance. A positive correlation was found between p85α and stearic acid, and between IRS1 and p110β with palmitic and dosahexaenoic acid. In contrast, a negative correlation was found between p85α and oleic acid, and between IRS1 and p110β with linoleic, arachidonic and adrenic acid. Incubation with palmitic acid decreased IRS1 expression. p85α was down-regulated after incubation with oleic and dosahexaenoic acid and up-regulated with palmitic acid. p110β expression was increased and decreased after incubation with oleic and palmitic acid, respectively. The ratio p85α/p110β was decreased by oleic and dosahexaenoic acid and increased by palmitic acid. Conclusions: Our in vitro results suggest a detrimental role of palmitic acid on the expression of gene related to insulin signaling pathway, with oleic acid being the one with the higher and more beneficial effects. DHA had a slight beneficial effect. Fatty acid-induced regulation of genes related to the IRS1/PI3K pathway may be a novel mechanism by which fatty acids regulate insulin sensitivity in visceral adipocytes.

PB1647 EXPRESSION OF PHOSPHORYLATED AKT AND CLASS I PI3K ISOFORMS IN CHILDHOOD ACUTE LYMPHOBLASTIC LEUKEMIA

Background : Acute lymphoblastic leukemia (ALL) is the most common neoplastic disease in children and represents 30% of all childhood malignancies. Although more than 80% of ALL cases are long term survivors, there is still a percentage of resistant or relapsed disease. The identification of genes and molecular pathways that are involved is crucial for targeted therapy design. The intracellular signaling pathway PI3K/AKT gets induced by growth factors and plays an important role in triggering many biological processes of the cell such as cell growth, metabolism, proliferation, survival, metabolism of insulin, protein synthesis and apoptosis. Recently it has been found that changes in the expression and mutations in many molecules of that pathway are involved in tumor genesis, which makes them an attractive target for cancer therapy. Aims: The study of the expression of the P110β, P110δ and P-Akt proteins in leukemic blasts of bone marrow from children with ALL at diagnosis and lymphomononuclear cells from children in remission, compared to the expression in lymphomononuclear cells from bone marrow of children with solid tumors without marrow involvement. Methods: Bone marrow mononuclear cells from 31 children with ALL at diagnosis, 25 children with ALL in remission and 20 children with solid tumors without bone marrow involvement was collected. Proteins were extracted and were analyzed with Western blot. The detection of P-Akt, P110β and P110δ was done with Thermo Scientific™ Pierce™ ECL Western Blotting Substrate,.The analysis of the results was performed with Image Lab and the statistical analysis with IBM SPSS Statistics version 25 (Kruskal-Wallis test and Mann-Whitney test). Results: The expression level of P-Akt in ALL diagnosis was significantly lower compared with ALL in remission (0.66 ± 0.21 vs 1.97 ± 0.41, p = 0.004) as well as with the solid tumors without bone marrow involvement (0.66 ± 0.21 vs 1.03 ± 0.25, p = 0.019). Additionally, the expression of P110δ estimated significantly lower in ALL diagnosis compared with ALL remission (0.92 ± 0.37 vs 1.52 ± 0.41, p = 0.012). On the other hand, there was no statistically significant difference of P110β expression values between ALL diagnosis, remission and solid tumors. Summary/Conclusion: P-Akt and P110δ expression was estimated decreased in ALL diagnosis although P110β expression was not found to be different between ALL diagnosis, ALL remission and solid tumors. Further studies are needed in order to clarify the relation of these proteins’ expression with other established prognostic factors and their role to the leukemia course, outcome and prognosis.

Expression of Phosphoinositide 3-Kinase p110α and p110β Subunits and PIK3CA Mutation in Patients With Advanced Gastric Carcinoma.

Activation of phosphoinositide 3-kinase (PI3K) is pivotal for the activity of the oncogenic PI3K/AKT signaling pathway. This study assessed the expression of 2 PI3K isoform proteins, p110α and p110β, and PIK3CA mutational status in advanced gastric carcinoma (AGC) and their correlation with clinicopathologic factors. Tissue microarray blocks were generated from 99 AGCs and immunohistochemically stained for p110α and p110β. Analysis of mutations in the PIK3CA gene, which encodes p110α, was performed using the PNAClamp PIK3CA Mutation Detection kit. Of the 99 tumors, positivity was seen in 62 (62.6%) for p110α and 97 (98.0%) for p110β with variable intensity and extent of staining. The median H-scores were 40 (range: 0 to 300) for p110α and 180 (range: 0 to 300) for p110β. Isoform p110α was more highly expressed in tumors with a lower pathologic T stage (P=0.035) and TNM stage (P=0.165), while p110β was not significantly associated with clinicopathologic factors. Samples with high p110α expression had a trend toward longer overall survival (OS) although it was not statistically significant (P=0.271), whereas high p110β expression correlated with shorter OS (P=0.016). In addition, p110β was an independent factor for poor prognosis in multivariate analysis for OS. Eight (8.1%) samples had PIK3CA mutations in exon 9. Mutational status at this locus was not significantly correlated with clinicopathologic factors. These results imply that p110β could have a more important role in the progression and aggressiveness of AGC than p110α and has potential as a prognostic biomarker in patients with AGC.

Integrin β1 promotes gemcitabine resistance in pancreatic cancer through Cdc42 activation of PI3K p110β signaling

Pancreatic ductal adenocarcinoma (PDAC) is one of the most common malignancies with very poor prognosis due to its broad resistance to chemotherapy. Our previous study showed that integrin β1 expression is upregulated in PDAC and confers gemcitabine resistance in PDAC cells via the signaling pathway including Cdc42 and AKT activation. But the accurate signal transductions are not clear. Here, we aimed to illuminate the signal transductions of integrin β1 in the acquisition of gemcitabine resistance in PDAC. Drug-resistance (DR) cells from AsPC-1 parent cell line (PCL) were selected. Integrin β1 expression was determined using western blot assay. Changes in drug response and the activity of phosphatidylinositol 3-kinase (PI3K) signaling after knockdown of integrin β1, Cdc42 or p110β were evaluated using MTT, cleaved caspase-3 immunofluorescence and western blot assay. Western blot assays also detected the variations in Cdc42 activity and p110β expression after integrin β1 knockdown. The interaction between Cdc42 and p110β was determined by Glutathione S-transferase (GST) pull-down assay. The results showed that integrin β1 expression was upregulated in DR-AsPC-1 cells, and integrin β1 knockdown significantly decreased the activity of Cdc42, a target molecule of integrin β1, and p110β expression. Knockdown of anyone of integrin β1, Cdc42 and p110β inhibited the activity of PI3K signaling, and sensitized DR-AsPC-1 cells to gemcitabine. GST pull-down assay showed that GTP-Cdc42 interacted with p110β. Collectively, these data indicated that integrin β1 promoted gemcitabine resistance in PDAC through Cdc42 activation of PI3K p110β signaling. In vivo experiments also confirmed this conclusion. These findings contribute to a better understanding the molecular mechanism of chemoresistance and facilitate the development of more targeted and effective treatment strategy for PDAC.

Natural product toosendanin reverses the resistance of human breast cancer cells to adriamycin as a novel PI3K inhibitor

Adriamycin (ADM) is a commonly used drug in clinical breast cancer treatment. However, some breast cancer types or breast cancers subjected to repeated ADM exposure develop strong resistance to ADM thus limiting its clinical efficacy. In this study, we found for the first time that toosendanin (TSN), a triterpenoid extracted from the traditional Chinese medicine Melia toosendan Sieb et Zucc, could successfully reverse adriamycin resistance in human breast cancer cells. Immunofluorescence and HPLC analysis demonstrated that TSN promoted adriamycin accumulation in breast cancer cells, especially in the nucleus. Furthermore, TSN could significantly reduce ABCB1 expression. We then found that TSN was capable of suppressing adriamycin-induced Akt phosphorylation, probably due to downregulation of the PI3K catalytic subunits P110α and P110β, and inhibition of DNA-PKcs. Importantly, the inhibitory effect of TSN on PI3K P110α and P110β expression was specifically observed in breast cancer cells but not in normal human cells. Moreover, TSN significantly potentiated the anti-cancer effect of ADM in the 4T1 breast cancer model and its inhibition rate was nearly 90%. Thus, TSN could be used as a novel PI3K inhibitor to reverse breast cancer resistance. The combination of ADM and TSN may represent a useful strategy for human breast cancer therapy.

Clinical Significance and Mechanism of PI3K p110β Overexpression in Non-small Cell Lung Cancer

背景与目的磷脂酰肌醇-3激酶（phosphatidylinositide 3-kinases, PI3K）通路是细胞内最重要的信号传导通路之一，参与细胞生长、增殖、分化、运动等多项重要功能，其异常活化见于50%-70%的非小细胞肺癌（non-small cell lung cancer, NSCLC）。PI3K蛋白作为PI3K通路的枢纽，表达水平的变化直接影响通路的功能状态，与NSCLC的发生、发展和靶向治疗密切相关。本研究旨在探讨PI3K催化亚基p110β在NSCLC中的表达、临床意义及作用机制。方法采用免疫组化法检测170例NSCLC中p110β和PI3K通路其他蛋白的表达，分析p110β的表达与患者临床病理特征的关系，与PI3K通路其他蛋白表达的关系。结果p110β在NSCLC的高表达率为41.8%。其表达水平与Ki67计数呈正相关（P=0.040），在腺癌和鳞状细胞癌间、不同性别、年龄、吸烟状况分组间以及不同T分期、N分期、TNM分期和病理学分级间差异均无统计学意义（P＞0.05）。p110β的高表达与EGFR突变呈负相关（P=0.022），与PTEN表达缺失呈正相关（P＜0.001），与ROS1、野生型EGFR、HER2、ALK和p-Akt（Ser473）的表达均无明显关系（P＞0.05）。结论p110β高表达在NSCLC是一频发事件；与PTEN缺失密切相关，是PTEN缺失肿瘤生存和进展的关键；可导致肿瘤增殖指数升高，但却与磷酸化Akt无关。PIK3CB突变不是p110β高表达的主要原因；各类受体酪氨酸激酶（receptor tyrosine kinases, RTKs）异常均未显示导致癌组织p110β表达增高的能力，而且，EGFR突变者p110β的表达反而低于EGFR野生型。

Abstract 336: PIK3CB/p110B is a survival factor in glioblastoma

Abstract Glioblastoma multiforme (GBM) is lethal even after surgical removal of the tumor, radiation, and chemotherapy. Residual tumor cells form an intractable tumor in nearly all patients within two years. Recurrent GBM is incurable due to resistance to current therapies. Inhibitors of PI3K (phosphatidylinositol-4,5-biphosphate 3-kinase)-a signaling pathway that causally contributes to tumor formation/recurrence-have been used to treat recurrent GBMs and achieved modest clinical effect. This is perhaps attributed to non-selective inhibition of PI3K isoforms, which yields intolerable toxicity. Class IA PI3K isoforms include three catalytic subunits (PIK3CA, B, or D that encodes p110α, β, or δ) and three regulatory subunits (PIK3R1-3 that encodes p85 isoforms). Our recent work indicates that PIK3CB levels positively correlate with the chances/risk of GBM recurrence, while being inversely associated with patient prognosis. This suggests that PIK3CB/p110β is important for GBM cell survival. To test this hypothesis, we first measured the expression of PI3K isoforms in a panel of 9 GBM cell lines. We found that U87MG, SF295, and U251 expressed much higher levels of p110β, coinciding with the levels of phosphorylated AKT. We then knocked down PIK3CA, B, and D in human U87MG cells and found that only depletion of PIK3CB/p110β resulted in an inactivation of downstream AKT. Moreover, knockdown of PIK3CB/p110β, but not other isoforms, induced substantial growth inhibition in U87MG, SF295 and U251 cells. This is congruent with the result that inhibition of PIK3CB/p110β activated apoptosis in U87MG cells. We also report that treatment of p110βhigh GBM cells with isoform specific inhibitors selectively represses the viability of these cells. Finally, we report that ectopic expression of p110β, but not p110α or δ, partially rescued U87MG cells from growth inhibition induced by TGX-221, a p110β-selective inhibitor. Collectively, our results demonstrate that PIK3CB/p110β is an important selective survival factor in GBM, underscoring the divergent roles of PI3K isoforms in GBM disease progression/recurrence and future therapeutic intervention. Citation Format: Kevin J. Pridham, Sujuan Guo, Zhi Sheng. PIK3CB/p110B is a survival factor in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 336. doi:10.1158/1538-7445.AM2017-336

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.

Targeting Class IA PI3K Isoforms Selectively Impairs Cell Growth, Survival, and Migration in Glioblastoma

The phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is frequently activated in human cancer and plays a crucial role in glioblastoma biology. We were interested in gaining further insight into the potential of targeting PI3K isoforms as a novel anti-tumor approach in glioblastoma. Consistent expression of the PI3K catalytic isoform PI3K p110α was detected in a panel of glioblastoma patient samples. In contrast, PI3K p110β expression was only rarely detected in glioblastoma patient samples. The expression of a module comprising the epidermal growth factor receptor (EGFR)/PI3K p110α/phosphorylated ribosomal S6 protein (p-S6) was correlated with shorter patient survival. Inhibition of PI3K p110α activity impaired the anchorage-dependent growth of glioblastoma cells and induced tumor regression in vivo. Inhibition of PI3K p110α or PI3K p110β also led to impaired anchorage-independent growth, a decreased migratory capacity of glioblastoma cells, and reduced the activation of the Akt/mTOR pathway. These effects were selective, because targeting of PI3K p110δ did not result in a comparable impairment of glioblastoma tumorigenic properties. Together, our data reveal that drugs targeting PI3K p110α can reduce growth in a subset of glioblastoma tumors characterized by the expression of EGFR/PI3K p110α/p-S6.

AcSDKP Regulates Cell Proliferation through the PI3KCA/Akt Signaling Pathway

The natural tetrapeptide acetyl-N-Ser-Asp-Lys-Pro (AcSDKP) is generated from the N-terminus of thymosin-β4 through enzymatic cleavage by prolyl oligopeptidase (POP). AcSDKP regulation of proliferation of different cells is implicated in hematopoiesis and angiogenesis. This tetrapeptide present in almost all cells was recently detected at elevated concentrations in neoplastic diseases. However, previously reported in vitro and in vivo studies indicate that AcSDKP does not contribute to the pathogenesis of cancers. Here we show that exogenous AcSDKP exerts no effect on the proliferation of actively dividing malignant cells. Using S17092, a specific POP inhibitor (POPi), to suppress the biosynthesis of AcSDKP in U87-MG glioblastoma cells characterized by high intracellular levels of this peptide, we found that all tested doses of POPi resulted in an equally effective depletion of AcSDKP, which was not correlated with the dose-dependent decreases in the proliferation rate of treated cells. Interestingly, addition of exogenous AcSDKP markedly reversed the reduction in the proliferation of U87-MG cells treated with the highest dose of POPi, and this effect was associated with activation of the phosphatidylinositol-3 kinase (PI3K)/Akt pathway. However, extracellular-regulated protein kinase (ERK) activation was unaltered by S17092 and AcSDKP co-treatment. Knockdown of individual PI3K catalytic subunits revealed that p110α and p110β contributed differently to AcSDKP regulation of U87-MG cell proliferation. Disruption of p110α expression by small interfering RNA (siRNA) abrogated AcSDKP-stimulated Akt phosphorylation, whereas knockdown of p110β expression exhibited no such effect. Our findings indicate for the first time that the PI3KCA/Akt pathway mediates AcSDKP regulation of cell proliferation and suggest a role for this ubiquitous intracellular peptide in cell survival.

Down-regulation of p110β expression increases chemosensitivity of colon cancer cell lines to oxaliplatin

This study examined the synergetic effect of class IA Phosphoinositide 3-kinases catalytic subunit p110β knockdown in conjunction with oxaliplatin treatment on colon cancer cells. Down-regulation of p110β by siRNA interference and oxaliplatin treatment were applied in colon cancer cell lines HT29, SW620 and HCT116. MTT assay was used to measure the inhibitory effect of p110β knockdown on the proliferation of colon cancer cell lines. SubG1 assay and Annexin-V FITC/PI double-labeling cytometry were applied to detect cell apoptosis. And cell cycle was evaluated by using PI staining and flow cytometry. The expression of caspase 3, cleaved PARP, p-Akt, T-Akt and p110β was determined by western blotting. The results suggested that down-regulation of p110β expression by siRNA obviously reduced cell number via accumulation in G(0)-G(1) phase of the cell cycle in the absence of notablely increased apoptosis in colon cancer cell lines HT29 and SW620 (S phase arrest in HCT116). Moreover, inhibition of p110β expression increased oxaliplatin-induced cell apoptosis and cell cycle arrest in HT29, HCT116 and SW620 cell lines. In addition, increases of cleaved caspase-3 and cleaved PARP induced by oxaliplatin treatment were determined by immunoblotting in p110β knockdown group compared with normal control group and wild-type group. It is concluded that down-regulated expression of p110β could inhibit colon cancer cells proliferation and result in increased chemosensitivity of colorectal cancer cells to oxaliplatin through augmentation of oxaliplatin-induced cell apoptosis and cell cycle arrest.

PI3K Inhibition with GDC-0941 Has Greater Efficacy Compared to p110δ-Selective Inhibition with CAL-101 in Mantle Cell Lymphoma and May Be Particularly Advantageous in Multiply Relapsed Patients

Abstract 1654 Background:Mantle cell lymphoma (MCL) is an incurable, aggressive subtype of non-Hodgkin lymphoma in which there is a need for novel targeted therapies. Activation of the PI3K-Akt pathway and its role in the pathogenesis of MCL has been highlighted in a number of studies. Constitutive activation of the PI3K pathway inactivates GSK-3β, a downstream target of Akt, that can phosphorylate cyclin D1 resulting in its nuclear export. There is also evidence that cyclin D1 mRNA stability and translation is enhanced by this pathway. The class Ia PI3K p110 catalytic subunit isoforms α, β and δ are primarily implicated in oncogenesis. While the PI3K p110δ isoform is known to be enriched in lymphocytes, a gain of PIK3CA (the gene encoding PI3K p110α) copy number has been shown to be a frequent alteration in MCL. The expression and relative importance of the individual Class Ia PI3K isoforms has not been documented in this disease. With the development of isoform selective inhibitors, this is an important issue that needs to be addressed. Aims:We studied the expression of class Ia PI3K isoforms in primary MCL with relation to morphological variants and disease status. We also compared the efficacy of PI3K inhibition in MCL cell lines and primary samples using two novel inhibitors, GDC-0941(predominantly p110α/δ-selective) and CAL-101 (δ-selective), both of which are in early phase clinical trials. Methods:Tissue microarrays were constructed from triplicate 1mm cores from 144 MCL biopsies and 16 tonsil controls. The levels of p110α, p110β and p110δ isoforms were then determined by immunohistochemistry using isoform-specific antibodies. The in vitro effect of PI3K inhibitors on cell viability and apoptosis was studied in 4 MCL cell lines, (Jeko-1, Granta519, REC-1 and JVM-2), and 15 primary MCL samples. Expression of the class Ia PI3K isoforms and changes in downstream targets of PI3K were determined by western blotting. Results:P110δ was expressed at a consistently higher level in MCL samples and normal tonsil controls compared to the α and β isoforms, while p110β expression was weak and significantly lower than p110α expression. On comparing expression of isoforms at diagnosis and relapse, p110α expression was significantly increased beyond 1st relapse compared to diagnostic biopsies (p=0.04) and tonsil controls (p=0.02), an observation that was even more apparent in 6 paired samples [p=0.008, median IHC score 19.6 (5.0−53.2) at diagnosis vs. 91.5 (38.6 − 129) beyond 1st relapse]. No significant change was found in the expression of p110β or p110δ between diagnostic and relapse samples. There was no significant difference in expression levels of the 3 isoforms between blastoid and non-blastoid morphological variants. Expression of both the p110α and δ isoforms was detected by western blotting in 4 MCL cell lines, but only Jeko-1 cells were sensitive to inhibition with GDC-0941. CAL-101 produced little or no apoptosis in all 4 cell lines. In primary MCL samples, GDC-0941 was consistently more potent than CAL-101, with decrease in cell viability of 32 vs. 20% at 1μM (p=0.15), 51 vs. 25% at 5μM (p=0.02) and 67 vs. 35% at 10μM (p<0.0001) GDC-0941 and CAL-101 respectively. GDC-0941 was also able to partially overcome the stimulatory effect of sCD40L and IL4 on primary MCL samples. Western blotting showed a consistent reduction in the phosphorylation of Akt and GSK-3β in sensitive MCL cells. Conclusion:Our studies demonstrate that although p110δ is the most consistently expressed isoform, the expression of the p110α subunit increases significantly in multiply relapsed MCL. This observation, in combination with significantly greater in vitro sensitivity of MCL primary samples to GDC-0941, compared to the p110δ-selective inhibitor CAL-101, provides strong evidence for further evaluation of GDC-0941 in this disease. Disclosures:Gribben:Roche: Honoraria; Celgene: Honoraria; GSK: Honoraria; Mundipharma: Honoraria; Gilead: Honoraria; Pharmacyclics: Honoraria. Joel:Astra Zeneca: Research Funding; Intellikine: Research Funding.

Studies on the Expression Patterns of Class I PI3K Catalytic Subunits and Its Prognostic Significance in Colorectal Cancer

The phosphatidylinositol 3-kinase/AKT (PI3K/AKT) pathway plays a critical role in human cancer. We determined the expression patterns of class I PI3K catalytic subunits and evaluated their importance in the development or progression of colorectal cancer (CRC). For this purpose, expression of class I PI3K isoforms was evaluated in 82 primary CRC and paired non-cancerous mucosa samples by qRT-PCR. P-AKT-Ser473 and P-AKT-Thr308 expression were measured by western blot. We found that, compared with paired non-cancerous mucosa samples, mRNA expression of p110α and p110β in CRCs was significantly increased to 2.02-fold (95% confidence interval [CI] 1.25-3.28 fold) and 1.76-fold (95% CI 1.19-2.60 fold), respectively; while slight differences were found regarding the expression of p110δ (0.57-fold; 95% CI 0.31-1.07 fold) and p110γ (0.97-fold; 95% CI 0.50-1.88 fold). Increased p110α and p110β expression correlated with primary tumor size, regional lymph node metastases, and AJCC stage. Increased p110β expression also correlated with distant metastasis. P-AKT-Thr308 and P-AKT-Ser473 expression showed significant direct correlations with p110α and p110β mRNA expression. Besides, CRC patients with p110β mRNA overexpression had a worse disease-free survival after radical surgery compared with those with normal or decreased levels (P = 0.043). It was, therefore, concluded that the altered p110α and p110β expression might contribute to the CRC development or progression.

Phosphoinositide 3-Kinase Pathway Activation in Phosphate and Tensin Homolog (PTEN)-deficient Prostate Cancer Cells Is Independent of Receptor Tyrosine Kinases and Mediated by the p110β and p110δ Catalytic Subunits

Class IA phosphoinositide 3-kinase (PI3K) p110 catalytic subunits are activated upon Src homology 2 domain-mediated binding of their p85 regulatory subunits to tyrosine-phosphorylated pYXXM motifs in receptor tyrosine kinases (RTKs) or adaptor proteins. The PI3K pathway is activated by phosphate and tensin homolog (PTEN) loss in most prostate cancers (PCa), but the contribution of upstream RTKs that may be targeted therapeutically has not been assessed. Immunoblotting of p85-associated proteins in serum-starved PTEN-deficient LNCaP and C4-2 PCa cells showed a small set of discrete tyrosine-phosphorylated proteins, but these proteins were not recognized by an anti-pYXXM motif antibody and were not found in PTEN-deficient PC3 PCa cells. LC/MS/MS using label-free proteomics and immunoblotting showed that p85 was associated primarily with p110beta and p110delta. An interaction with ErbB3 was also detected but was independent of ErbB3 tyrosine phosphorylation and was not required for basal PI3K activity. Basal tyrosine phosphorylation of p110beta and p110delta could be blocked by c-Src inhibitors, but this did not suppress PI3K activity, which was similarly independent of Ras. Basal PI3K activity was mediated by p110beta in PC3 cells and by both p110beta and p110delta in LNCaP cells, whereas p110alpha was required for PI3K activation in response to RTK stimulation by heregulin-beta1. These findings show that basal PI3K activity in PTEN-deficient PCa cells is RTK-independent and can be mediated by p110beta and p110delta. Increased p110beta expression in PCa may be required for RTK-independent PI3K pathway activation in adult prostate epithelium with genetic or epigenetic PTEN down-regulation.

Altered skeletal muscle insulin signaling and mitochondrial complex II-III linked activity in adult offspring of obese mice

We recently reported insulin resistance in adult offspring of obese C57BL/6J mice. We have now evaluated whether parameters of skeletal muscle structure and function may play a role in insulin resistance in this model of developmental programming. Obesity was induced in female mice by feeding a highly palatable sugar and fat-rich diet for 6 wk prior to pregnancy, and during pregnancy and lactation. Offspring of obese dams were weaned onto standard laboratory chow. At 3 mo of age, skeletal muscle insulin signaling protein expression, mitochondrial electron transport chain activity (ETC), muscle fiber type, fiber density, and fiber cross-sectional area were compared with that of offspring of control dams weaned onto the chow diet. Female offspring of obese dams demonstrated decreased skeletal muscle expression of p110beta, the catalytic subunit of PI3K (P < 0.01), as well as reduced Akt phosphorylation at Serine residue 473 compared with control offspring. Male offspring of obese dams demonstrated increased skeletal muscle Akt2 and PKCzeta expression (P < 0.01; P < 0.001, respectively). A decrease in mitochondrial-linked complex II-III was observed in male offspring of obese dams (P < 0.01), which was unrelated to CoQ deficiency. This was not observed in females. There were no differences in muscle fiber density between offspring of obese dams and control offspring in either sex. Sex-related alterations in key insulin-signaling proteins and in mitochondrial ETC may contribute to a state of insulin resistance in offspring of obese mice.

Synthetic lethality when combining phosphoinositide 3-kinase alpha and beta catalytic subunit-directed RNAi and estrogen deprivation for estrogen receptor positive breast cancer: implications for clinical trial design with pharmacological inhibitors.

Abstract Abstract #3063 Background: Endocrine therapy with estrogen deprivation (ED) induces cell cycle arrest in sensitive estrogen receptor positive (ER+) breast cancers, but typically not apoptosis, thus relapse is common despite ED due to residual surviving tumor cells. The phosphoinositide 3-kinase (PI3K) pathway, which promotes cell survival, is hyperactivated in ER+ breast cancer due to mutations of genes in the PI3K signaling cascade, most commonly PIK3CA. We therefore investigated the role of p110α and p110β, the gene products of PIK3CA and PIK3CB, in promoting cell survival in ER+ breast cancer.&amp;#x2028; Materials and Methods: RNA interference (RNAi) was used to selectively inhibit p110α and p110β expression in the ER+, PIK3CA mutant MCF-7 and T47D cell lines; the ER+, PIK3CA wild-type but PIK3CB gene amplified HCC712 cell line; and the ER-, PIK3CA and PIK3CB wild-type MDA-MB-231 cell line. Western blotting was used to confirm p110α and p110β knockdown efficiencies and to determine the effects of specific knockdowns on PI3K pathway signaling. Cell line growth was measured using a resazurin reduction assay. Apoptosis was quantified using TUNEL/Hoechst staining. Gene copy number for PIK3CB was assessed by FISH in cell lines and tumor samples.&amp;#x2028; Results: PIK3CA RNAi inhibited growth and activated apoptosis in all tested ER+ cell lines under ED, whereas the addition of estrogen reversed PIK3CA RNAi-induced apoptosis. PIK3CB RNAi inhibited proliferation and promoted apoptosis in the absence of estrogen only in the PIK3CB-gene amplified HCC712 cell line. In combination, PIK3CA and PIK3CB gene knockdowns produced a synergistic apoptotic effect on T47D and HCC712 cell lines, but not in MCF-7 cells which contain low levels of p110β protein. In contrast PIK3CA and PIK3CB RNAi did not promote apoptosis in the ER- MDA-MB-231 cell line. Finally, since PIK3CB gene amplification has not been described previously we conducted a screen by FISH and array CGH and detected low-level PIK3CB copy number gain or amplification in ∼5% of clinical samples from a series of breast cancer patients representing diverse clinical phenotypes (ER+, ER-, ERBB2+).&amp;#x2028; Conclusions: Inhibition of the PI3K pathway through suppression of PI3K catalytic subunit expression produces a synthetic lethal effect in the absence of estrogen specifically in ER+ breast cancer cells. These data establish a preclinical rationale for combining endocrine therapy with PI3K pharmacological inhibitors in ER+ breast cancer, but suggest that both PIK3CA and PIK3CB are therapeutic targets and gene mutation or amplification in both catalytic subunits may have to be taken into account when identiying a sensitive population for PI3 kinase-directed therapy. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3063.

Association Analysis Indicates That a Variant GATA-Binding Site in the PIK3CB Promoter Is a Cis-Acting Expression Quantitative Trait Locus for This Gene and Attenuates Insulin Resistance in Obese Children

In search of functional polymorphisms associated with the genetics of insulin resistance, we studied a variant in the promoter of PIK3CB, the gene coding for the catalytic p110beta subunit of phosphatidylinositol (PI) 3-kinase, a major effector of insulin action. The rs361072 C/T variant was selected among single nucleotide polymorphisms of the PIK3CB region because we suspected that its common C allele (allelic frequency approximately 50% in Europeans) could create a GATA-binding motif and was genotyped in five cohorts of obese (n = 1,876) and two cohorts of nonobese (n = 1,490) European children. To estimate insulin resistance in these children, the homeostasis model assessment for insulin resistance (HOMA-IR) index was measured in strict nutritional conditions. GATA-binding and functional effects of rs361072 were explored in transfected cell lines and in lymphocytes from obese children. The rs361072 C/T variant was associated with HOMA-IR in the obese children cohorts (1.7 x 10(-12) < P < 2 x 10(-4) for C/C vs. T/T using regression analysis). HOMA-IR averaged 3.3 +/- 0.1 in C/C and 4.5 +/- 0.2 in T/T obese children (P = 4.5 x 10(-6) by ANOVA). C/T patients had intermediate values. As shown by the interaction between BMI and genotype (P = 2.1 x 10(-9)), the association of rs361072 with HOMA-IR depended on BMI and was only marginal in nonobese children (P = 0.04). At the molecular level, the C allele of rs361072 was found to create a GATA-binding site able to increase transcription of PIK3CB. We postulate that the C allele of rs361072 is a causal variant capable of attenuating insulin resistance in obese children through increased expression of p110beta.