High levels of p110δ PI3K expression in solid tumor cells suppress PTEN activity, generating cellular sensitivity to p110δ inhibitors through PTEN activation

Deciphering the predictive value of senescence-related signature in lung adenocarcinoma: Implications for antitumor immunity and immunotherapy efficacy

Objective

The senescence process is pivotal in both the onset and advancement of lung adenocarcinoma (LUAD), influencing cell growth, immune evasion, the potential for metastasis, and resistance to treatments. Senescent cells' dual nature, both harmful and advantageous, adds complexity to understanding their expression patterns and clinical relevance in LUAD. In this study, we sought to evaluate the predictive value of the senescence-related signature in survival outcomes and immunotherapy efficacy in patients with LUAD.

Materials and methods

We integrated data from 1449 LUAD cases sourced from different publicly accessible datasets and a clinical cohort of Chinese LUAD patients. The Cox regression analysis employing the least absolute shrinkage and selection operator (LASSO) was performed on 156 senescence-associated genes to develop the senescence-related signature. Kaplan-Meier analysis and time-dependent receiver operating characteristic curves were utilizaed to assess the prognostic significance of the senescence-related signature. Functional annotation, immune infiltration analysis, and gene set variation analysis were applied to investigate the association of the senescence-related signature with anti-tumor immunity in LUAD. Immunotherapy cohorts of non-small cell lung cancer, urothelial carcinoma, skin cutaneous melanoma, and glioblastoma patients were included to assess the senescence-related signature in predicting immunotherapy efficacy.

Results

The senescence-related signature, which encompasses seven senescence-related genes, namely, FOXM1, VDAC1, PPP3CA, MAPK13, PIK3CD, RRAS, and CCND3, was identified to have predictive significance across multiple LUAD cohorts and demonstrated a negative association with antitumor immunity and tumor-infiltrating neutrophils. Patients exhibiting low expression levels of the senescence-related signature responded more favorably to immune checkpoint inhibitors in various solid tumors, including LUAD. Inhibiting FOXM1 pharmacologically with thiostrepton produced tumor-suppressive effects and improved immunotherapy responses in a Lewis lung carcinoma mouse model.

Conclusions

The senescence-related signature demonstrates potential in predicting patient prognosis and immunotherapy efficacy in LUAD.

Targeting the PI3K/AKT signaling pathway in anticancer research: a recent update on inhibitor design and clinical trials (2020-2023)

INTRODUCTION

Recent years have witnessed great achievements in drug design and development targeting the phosphatidylinositol 3-kinase/protein kinase-B (PI3K/AKT) signaling pathway, a pathway central to cell growth and proliferation. The nearest neighbor protein-protein interaction networks for PI3K and AKT show the interplays between these target proteins which can be harnessed for drug discovery. In this review, we discuss the drug design and clinical development of inhibitors of PI3K/AKT in the past three years. We review in detail the structures, selectivity, efficacy, and combination therapy of 35 inhibitors targeting these proteins, classified based on the target proteins. Approaches to overcoming drug resistance and to minimizing toxicities are discussed. Future research directions for developing combinational therapy and PROTACs of PI3K and AKT inhibitors are also discussed.

AREA COVERED

This review covers clinical trial reports and patent literature on inhibitors of PI3K and AKT published between 2020 and 2023.

EXPERT OPINION

To address drug resistance and drug toxicity of inhibitors of PI3K and AKT, it is highly desirable to design and develop subtype-selective PI3K inhibitors or subtype-selective AKT1 inhibitors to minimize toxicity or to develop allosteric drugs that can form covalent bonds. The development of PROTACs of PI3Kα or AKT helps to reduce off-target toxicities.

A combined opposite targeting of p110δ PI3K and RhoA abrogates skin cancer

Malignant melanoma is the most aggressive and deadly skin cancer with an increasing incidence worldwide whereas SCC is the second most common non-melanoma human skin cancer with limited treatment options. Here we show that the development and metastasis of melanoma and SCC cancers can be blocked by a combined opposite targeting of RhoA and p110δ PI3K. We found that a targeted induction of RhoA activity into tumours by deletion of p190RhoGAP-a potent inhibitor of RhoA GTPase-in tumour cells together with adoptive macrophages transfer from δD910A/D910A mice in mice bearing tumours with active RhoA abrogated growth progression of melanoma and SCC tumours. Τhe efficacy of this combined treatment is the same in tumours lacking activating mutations in BRAF and in tumours harbouring the most frequent BRAF(V600E) mutation. Furthermore, the efficiency of this combined treatment is associated with decreased ATX expression in tumour cells and tumour stroma bypassing a positive feedback expression of ATX induced by direct ATX pharmacological inactivation. Together, our findings highlight the importance of targeting cancer cells and macrophages for skin cancer therapy, emerge a reverse link between ATX and RhoA and illustrate the benefit of p110δ PI3K inhibition as a combinatorial regimen for the treatment of skin cancers.

Aberrant PI3Kδ splice isoform as a potential biomarker and novel therapeutic target for endocrine cancers

Introduction

PI3K/AKT signaling pathway is upregulated in a broad spectrum of cancers. Among the class I PI3Ks (PI3Kδ/β/δ isoforms), PI3Kδ has been implicated in hematologic cancers and solid tumors. Alternative splicing is a post-transcriptional process for acquiring proteomic diversity in eukaryotic cells. Emerging evidence has highlighted the involvement of aberrant mRNA splicing in cancer development/progression.

Methods

Our previous studies revealed that PIK3CD-S is an oncogenic splice variant that promotes tumor aggressiveness and drug resistance in prostate cancer (PCa). To further evaluate the potential of utilizing PI3Kδ-S (encoded from PIK3CD-S) as a cancer biomarker and/or drug target, comprehensive analyses were performed in a series of patient samples and cell lines derived from endocrine/solid tumors. Specifically, IHC, immunofluorescence, western blot and RT-PCR assay results have demonstrated that PI3Kδ isoforms were highly expressed in endocrine/solid tumor patient specimens and cell lines.

Results

Differential PIK3CD-S/PIK3CD-L expression profiles were identified in a panel of endocrine/solid tumor cells. SiRNA knockdown of PIK3CD-L or PIK3CD-S differentially inhibits AKT/mTOR signaling in PCa, breast, colon and lung cancer cell lines. Moreover, siRNA knockdown of PTEN increased PI3Kδ levels and activated AKT/mTOR signaling, while overexpression of PTEN reduced PI3Kδ levels and inhibited AKT/mTOR signaling in cancer cells. Intriguingly, PI3Kδ-S levels remained unchanged upon either siRNA knockdown or overexpression of PTEN. Taken together, these results suggested that PTEN negatively regulates PI3Kδ-L and its downstream AKT/mTOR signaling, while PI3Kδ-S promotes AKT/mTOR signaling without regulation by PTEN. Lastly, PI3Kδ inhibitor Idelalisib and SRPK1/2 inhibitor SRPIN340 were employed to assess their efficacies on inhibiting the PI3Kδ-expressing endocrine/solid tumors. Our results have shown that Idelalisib effectively inhibited PI3Kδ-L (but not PI3Kδ-S) mediated AKT/mTOR signaling. In contrast, SRPIN340 reversed the aberrant mRNA splicing, thereby inhibiting AKT/mTOR signaling. In-vitro functional assays have further demonstrated that a combination of Idelalisib and SRPIN340 achieved a synergistic drug effect (with drastically reduced cell viabilities/growths of tumor spheroids) in inhibiting the advanced tumor cells.

Conclusion

In summary, our study has suggested a promising potential of utilizing PI3Kδ-S (an oncogenic isoform conferring drug resistance and exempt from PTEN regulation) as a prognostic biomarker and drug target in advanced endocrine cancers.

Functional impact and molecular binding modes of drugs that target the PI3K isoform p110δ

Targeting the PI3K isoform p110δ against B cell malignancies is at the mainstay of PI3K inhibitor (PI3Ki) development. Therefore, we generated isogenic cell lines, which express wild type or mutant p110δ, for assessing the potency, isoform-selectivity and molecular interactions of various PI3Ki chemotypes. The affinity pocket mutation I777M maintains p110δ activity in the presence of idelalisib, as indicated by intracellular AKT phosphorylation, and rescues cell functions such as p110δ-dependent cell viability. Resistance owing to this substitution consistently affects the potency of p110δ-selective in contrast to most multi-targeted PI3Ki, thus distinguishing usually propeller-shaped and typically flat molecules. Accordingly, molecular dynamics simulations indicate that the I777M substitution disturbs conformational flexibility in the specificity or affinity pockets of p110δ that is necessary for binding idelalisib or ZSTK474, but not copanlisib. In summary, cell-based and molecular exploration provide comparative characterization of currently developed PI3Ki and structural insights for future PI3Ki design.

Molecular Insight into Drug Resistance Mechanism Conferred by Aberrant PIK3CD Splice Variant in African American Prostate Cancer

Targeting PI3Kδ has emerged as a promising therapy for hematologic and non-hematologic malignancies. Previously, we identified an oncogenic splice variant, PIK3CD-S, conferring Idelalisib resistance in African American (AA) prostate cancer (PCa). In the current study, we employed a comprehensive analysis combining molecular biology, biochemistry, histology, in silico simulation, and in vitro functional assays to investigate the PIK3CD-S expression profiles in PCa samples and to elucidate the drug resistance mechanism mediated by PI3Kδ-S (encoded by PIK3CD-S). The immunohistochemistry, RT-PCR, and Western blot assays first confirmed that PI3Kδ-S is highly expressed in AA PCa. Compared with PCa expressing the full-length PI3Kδ-L, PCa expressing PI3Kδ-S exhibits enhanced drug resistance properties, including a higher cell viability, more antiapoptotic and invasive capacities, and constitutively activated PI3K/AKT signaling, in the presence of PI3Kδ/PI3K inhibitors (Idelalisib, Seletalisib, Wortmannin, and Dactolisib). Molecular docking, ATP-competitive assays, and PI3 kinase assays have further indicated a drastically reduced affinity of PI3Kδ inhibitors with PI3Kδ-S vs. PI3Kδ-L, attributed to the lack of core binding residues in the PI3Kδ-S catalytic domain. Additionally, SRSF2 has been identified as a critical splicing factor mediating exon 20 skipping in PIK3CD pre-mRNA. The inhibition of the SRSF2 activity by SRPIN340 successfully sensitizes AA PCa cells to PI3Kδ inhibitors, suggesting a novel therapeutic option for Idelalisib-resistant tumors.

Binding and selectivity studies of phosphatidylinositol 3-kinase (PI3K) inhibitors

Overexpression of the Phosphatidylinositol 3-kinase (PI3K) proteins have been observed in cancer cells. Targeting the phosphatidylinositol 3-kinase (PI3K) signaling transduction pathway by inhibition of the PI3K substrate recognition sites has been proved to be an effective approach to block cancer progression. Many PI3K inhibitors have been developed. Seven drugs have been approved by the US FDA with a mechanism of targeting the phosphatidylinositol 3-kinase/protein kinase-B/mammalian target of rapamycin (PI3K/AKT/mTOR) signaling pathway. In this study, we used docking tools to investigate selective binding of ligands toward four different subtypes of PI3Ks (PI3Kα, PI3Kβ, PI3Kγ and PI3Kδ). The affinity predicted from both the Glide dock and the Movable-Type (MT)-based free energy calculations agreed well with the experimental data. The validation of our predicted methods with a large dataset of 147 ligands showed very small mean errors. We identified residues that may dictate the subtype-specific binding. Particularly, residues Asp964, Ser806, Lys890 and Thr886 of PI3Kγ might be utilized for PI3Kγ-selective inhibitor design. Residues Val828, Trp760, Glu826 and Tyr813 may be important for PI3Kδ-selective inhibitor binding.

Nuclear PTEN's Functions in Suppressing Tumorigenesis: Implications for Rare Cancers

Phosphatase and tensin homolog (PTEN) encodes a tumor-suppressive phosphatase with both lipid and protein phosphatase activity. The tumor-suppressive functions of PTEN are lost through a variety of mechanisms across a wide spectrum of human malignancies, including several rare cancers that affect pediatric and adult populations. Originally discovered and characterized as a negative regulator of the cytoplasmic, pro-oncogenic phosphoinositide-3-kinase (PI3K) pathway, PTEN is also localized to the nucleus where it can exert tumor-suppressive functions in a PI3K pathway-independent manner. Cancers can usurp the tumor-suppressive functions of PTEN to promote oncogenesis by disrupting homeostatic subcellular PTEN localization. The objective of this review is to describe the changes seen in PTEN subcellular localization during tumorigenesis, how PTEN enters the nucleus, and the spectrum of impacts and consequences arising from disrupted PTEN nuclear localization on tumor promotion. This review will highlight the immediate need in understanding not only the cytoplasmic but also the nuclear functions of PTEN to gain more complete insights into how important PTEN is in preventing human cancers.

Role of PI3K-AKT-mTOR Pathway as a Pro-Survival Signaling and Resistance-Mediating Mechanism to Therapy of Prostate Cancer

Androgen deprivation therapy (ADT) and androgen receptor (AR)-targeted therapy are the gold standard options for treating prostate cancer (PCa). These are initially effective, as localized and the early stage of metastatic disease are androgen- and castration-sensitive. The tumor strongly relies on systemic/circulating androgens for activating AR signaling to stimulate growth and progression. However, after a certain point, the tumor will eventually develop a resistant stage, where ADT and AR antagonists are no longer effective. Mechanistically, it seems that the tumor becomes more aggressive through adaptive responses, relies more on alternative activated pathways, and is less dependent on AR signaling. This includes hyperactivation of PI3K-AKT-mTOR pathway, which is a central signal that regulates cell pro-survival/anti-apoptotic pathways, thus, compensating the blockade of AR signaling. The PI3K-AKT-mTOR pathway is well-documented for its crosstalk between genomic and non-genomic AR signaling, as well as other signaling cascades. Such a reciprocal feedback loop makes it more complicated to target individual factor/signaling for treating PCa. Here, we highlight the role of PI3K-AKT-mTOR signaling as a resistance mechanism for PCa therapy and illustrate the transition of prostate tumor from AR signaling-dependent to PI3K-AKT-mTOR pathway-dependent. Moreover, therapeutic strategies with inhibitors targeting the PI3K-AKT-mTOR signal used in clinic and ongoing clinical trials are discussed.

A Review of Phosphocreatine 3 Kinase δ Subtype (PI3Kδ) and Its Inhibitors in Malignancy

Most cancer deaths are caused by metastasis. The phosphocreatine 3-kinase (PI3K) family includes the I–III classes, with class I divided into 4 subtypes (α, β, γ, δ); and PI3K signaling participates in the regulatory processes of cell proliferation, differentiation, apoptosis, and glucose transport. Moreover, PI3Ks are modulators of cellular membrane lipids involved in signaling and trafficking events. The PI3Kdelta isoform (PI3Kδ), which is not only specifically expressed in hematopoietic cells, but also in different tumor cell lines, is expressed extensively. The increase in PI3Kδ activity is often associated with a variety of cancers. Currently, the strategy of tumor therapy based on PI3Kδ and its related signaling pathway is developing. Besides its established role in controlling functions in autoimmunity and inflammation, the role of PI3Kδ in tumor and metastasis is not clearly elucidated, with the effects of inhibiting PI3Kδ in several types of tumors also remaining unexplored. In addition, the specific inhibitor of PI3Kδ in tumor progression and metastasis and its underlying mechanism need to be further studied. The purpose of this review is to rationalize the existing functions and mechanisms of PI3Kδ in tumor metastasis and the relationship with hematopoietic cells in cancers as well cross-talking with miRNA, which provides a new theoretical basis and potential therapeutic target for the drug therapy of tumor metastasis.

PI3K inhibitors are finally coming of age

Overactive phosphoinositide 3-kinase (PI3K) in cancer and immune dysregulation has spurred extensive efforts to develop therapeutic PI3K inhibitors. Although progress has been hampered by issues such as poor drug tolerance and drug resistance, several PI3K inhibitors have now received regulatory approval - the PI3Kα isoform-selective inhibitor alpelisib for the treatment of breast cancer and inhibitors mainly aimed at the leukocyte-enriched PI3Kδ in B cell malignancies. In addition to targeting cancer cell-intrinsic PI3K activity, emerging evidence highlights the potential of PI3K inhibitors in cancer immunotherapy. This Review summarizes key discoveries that aid the clinical translation of PI3Kα and PI3Kδ inhibitors, highlighting lessons learnt and future opportunities.

Role of PTEN-less in cardiac injury, hypertrophy and regeneration

Cardiovascular diseases are the leading cause of death worldwide. Cardiomyocytes are capable of coordinated contractions, which are mainly responsible for pumping blood. When cardiac stress occurs, cardiomyocytes undergo transition from physiological homeostasis to hypertrophic growth, proliferation, or apoptosis. During these processes, many cellular factors and signaling pathways participate. PTEN is a ubiquitous dual-specificity phosphatase and functions by dephosphorylating target proteins or lipids, such as PIP3, a second messenger in the PI3K/AKT signaling pathway. Downregulation of PTEN expression or inhibiting its biologic activity improves heart function, promotes cardiomyocytes proliferation, reduces cardiac fibrosis as well as dilation, and inhibits apoptosis following ischemic stress such as myocardial infarction. Inactivation of PTEN exhibits a potentially beneficial therapeutic effects against cardiac diseases. In this review, we summarize various strategies for PTEN inactivation and highlight the roles of PTEN-less in regulating cardiomyocytes during cardiac development and stress responses.

Attacking the PI3K/Akt/mTOR signaling pathway for targeted therapeutic treatment in human cancer

Cancer is the second leading cause of human death globally. PI3K/Akt/mTOR signaling is one of the most frequently dysregulated signaling pathways observed in cancer patients that plays crucial roles in promoting tumor initiation, progression and therapy responses. This is largely due to that PI3K/Akt/mTOR signaling is indispensable for many cellular biological processes, including cell growth, metastasis, survival, metabolism, and others. As such, small molecule inhibitors targeting major kinase components of the PI3K/Akt/mTOR signaling pathway have drawn extensive attention and been developed and evaluated in preclinical models and clinical trials. Targeting a single kinase component within this signaling usually causes growth arrest rather than apoptosis associated with toxicity-induced adverse effects in patients. Combination therapies including PI3K/Akt/mTOR inhibitors show improved patient response and clinical outcome, albeit developed resistance has been reported. In this review, we focus on revealing the mechanisms leading to the hyperactivation of PI3K/Akt/mTOR signaling in cancer and summarizing efforts for developing PI3K/Akt/mTOR inhibitors as either mono-therapy or combination therapy in different cancer settings. We hope that this review will facilitate further understanding of the regulatory mechanisms governing dysregulation of PI3K/Akt/mTOR oncogenic signaling in cancer and provide insights into possible future directions for targeted therapeutic regimen for cancer treatment, by developing new agents, drug delivery systems, or combination regimen to target the PI3K/Akt/mTOR signaling pathway. This information will also provide effective patient stratification strategy to improve the patient response and clinical outcome for cancer patients with deregulated PI3K/Akt/mTOR signaling.

WSX1 act as a tumor suppressor in hepatocellular carcinoma by downregulating neoplastic PD-L1 expression

WSX1, a receptor subunit for IL-27, is widely expressed in immune cells and closely involved in immune response, but its function in nonimmune cells remains unknown. Here we report that WSX1 is highly expressed in human hepatocytes but downregulated in hepatocellular carcinoma (HCC) cells. Using NRAS/AKT-derived spontaneous HCC mouse models, we reveal an IL-27–independent tumor-suppressive effect of WSX1 that largely relies on CD8⁺ T-cell immune surveillance via reducing neoplastic PD-L1 expression and the associated CD8⁺ T-cell exhaustion. Mechanistically, WSX1 transcriptionally downregulates an isoform of PI3K—PI3Kδ and thereby inactivates AKT, reducing AKT-induced GSK3β inhibition. Activated GSK3β then boosts PD-L1 degradation, resulting in PD-L1 reduction. Overall, we demonstrate that WSX1 is a tumor suppressor that reinforces hepatic immune surveillance by blocking the PI3Kδ/AKT/GSK3β/PD-L1 pathway. Our results may yield insights into the host homeostatic control of immune response and benefit the development of cancer immunotherapies.

The biological functions of WSX1, the alpha subunit of the interleukin-27 receptor, in non-immune cells are largely unknown. Here, the authors propose an IL-27-independent tumor suppressor role for WSX1 in hepatocytes, showing that WSX1 restricts tumor progression by down-regulating PD-L1 expression in tumour cells and maximizing T cell mediated antitumor immune responses.

Phosphatidylinositol 3-kinase (PI3K) inhibitors: a recent update on inhibitor design and clinical trials (2016-2020)

Introduction: The phosphatidylinositol 3-kinase/protein kinase-B/mammalian target of rapamycin (PI3K/AKT/mTOR) signaling pathway plays a central role in regulating cell growth and proliferation and thus has been considered as effective anticancer drug targets. Many PI3K inhibitors have been developed and progressed to various stages of clinical trials, and some have been approved as anticancer treatment. In this review, we discuss the drug design and clinical development of PI3K inhibitors over the past 4 years. We review the selectivity and potency of 47 PI3K inhibitors. Structural determinants for increasing selectivity toward PI3K subtype-selectivity or mutant selectivity are discussed. Future research direction and current clinical development in combination therapy of inhibitors involved in PI3Ks are also discussed.Area covered: This review covers clinical trial reports and patent literature on PI3K inhibitors and their selectivity published between 2016 and 2020.Expert opinion: To PI3Kα mutants (E542K, E545K, and H1047R), it is highly desirable to design and develop mutant-specific PI3K inhibitors. It is also necessary to develop subtype-selective PI3Kα inhibitors to minimize toxicity. To reduce drug resistance and to improve efficacy, future studies should include combination therapy of PI3K inhibitors with existing anticancer drugs from different pathways.

The role of different PI3K protein subtypes in the metastasis, angiogenesis and clinical prognosis of hepatocellular carcinoma

BACKGROUND AND OBJECTIVES

Abnormal activation of the PI3K/AKT pathway is closely related to tumor occurrence, development and angiogenesis. PI3K, as a key protein in the PI3K/Akt pathway, has different subtypes that play diverse roles in various tumors. The aim of this study was to examine the roles of different PI3K protein subtypes (PI3Kp110α, PI3Kp110β, and PI3Kp110δ) in the metastasis, angiogenesis and prognosis of hepatocellular carcinoma (HCC).

METHODS

The roles of different PI3K protein subtypes in the metastasis, angiogenesis and prognosis of HCC were assessed by immunohistochemical staining of 97 HCC tissues and the STRING database.

RESULTS

Our results showed that PI3Kp110α and PI3Kp110δ were associated with HCC metastasis and angiogenesis. Patients with high expression of PI3Kp110α and PI3Kp110δ had a worse prognosis and shorter survival time, respectively, than those with low expression, whereas these effects were not observed for PI3Kp110β. Cox regression analysis showed that PI3Kp110α and clinical stage were independent risk factors for the overall survival of HCC patients.

CONCLUSIONS

PI3Kp110α and PI3Kp110δ promoted HCC metastasis and angiogenesis via the PI3K/AKT pathway, and PI3Kp110α was an independent risk factor for HCC patients. These findings provide valuable insights for the prognosis evaluation and the selection of subtype inhibitors of HCC patients.

Diverse mechanisms activate the PI 3-kinase/mTOR pathway in melanomas: implications for the use of PI 3-kinase inhibitors to overcome resistance to inhibitors of BRAF and MEK

Background

The PI 3-kinase (PI3K) pathway has been implicated as a target for melanoma therapy.

Methods

Given the high degree of genetic heterogeneity in melanoma, we sought to understand the breadth of variation in PI3K signalling in the large NZM panel of early passage cell lines developed from metastatic melanomas.

Results

We find the vast majority of lines show upregulation of this pathway, and this upregulation is achieved by a wide range of mechanisms. Expression of all class-IA PI3K isoforms was readily detected in these cell lines. A range of genetic changes in different components of the PI3K pathway was seen in different lines. Coding variants or amplification were identified in the PIK3CA gene, and amplification of the PK3CG gene was common. Deletions in the PIK3R1 and PIK3R2 regulatory subunits were also relatively common. Notably, no genetic variants were seen in the PIK3CD gene despite p110δ being expressed in many of the lines. Genetic variants were detected in a number of genes that encode phosphatases regulating the PI3K signalling, with reductions in copy number common in PTEN, INPP4B, INPP5J, PHLLP1 and PHLLP2 genes. While the pan-PI3K inhibitor ZSTK474 attenuated cell growth in all the lines tested, isoform-selective inhibition of p110α and p110δ inhibited cell growth in only a subset of the lines and the inhibition was only partial. This suggests that functional redundancy exists between PI3K isoforms. Furthermore, while ZSTK474 was initially effective in melanoma cells with induced resistance to vemurafenib, a subset of these cell lines concurrently developed partial resistance to PI3K inhibition. Importantly, mTOR-selective or mTOR/PI3K dual inhibitors effectively inhibited cell growth in all the lines, including those already resistant to BRAF inhibitors and ZSTK474.

Conclusions

Overall, this indicates a high degree of diversity in the way the PI3K pathway is activated in different melanoma cell lines and that mTOR is the most effective point for targeting the growth via the PI3K pathway across all of these cell lines.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07826-4.

The PI3K-AKT-mTOR Pathway and Prostate Cancer: At the Crossroads of AR, MAPK, and WNT Signaling

Oncogenic activation of the phosphatidylinositol-3-kinase (PI3K), protein kinase B (PKB/AKT), and mammalian target of rapamycin (mTOR) pathway is a frequent event in prostate cancer that facilitates tumor formation, disease progression and therapeutic resistance. Recent discoveries indicate that the complex crosstalk between the PI3K-AKT-mTOR pathway and multiple interacting cell signaling cascades can further promote prostate cancer progression and influence the sensitivity of prostate cancer cells to PI3K-AKT-mTOR-targeted therapies being explored in the clinic, as well as standard treatment approaches such as androgen-deprivation therapy (ADT). However, the full extent of the PI3K-AKT-mTOR signaling network during prostate tumorigenesis, invasive progression and disease recurrence remains to be determined. In this review, we outline the emerging diversity of the genetic alterations that lead to activated PI3K-AKT-mTOR signaling in prostate cancer, and discuss new mechanistic insights into the interplay between the PI3K-AKT-mTOR pathway and several key interacting oncogenic signaling cascades that can cooperate to facilitate prostate cancer growth and drug-resistance, specifically the androgen receptor (AR), mitogen-activated protein kinase (MAPK), and WNT signaling cascades. Ultimately, deepening our understanding of the broader PI3K-AKT-mTOR signaling network is crucial to aid patient stratification for PI3K-AKT-mTOR pathway-directed therapies, and to discover new therapeutic approaches for prostate cancer that improve patient outcome.

p110δ PI3K as a therapeutic target of solid tumours

From the time of first characterization of PI3K as a heterodimer made up of a p110 catalytic subunit and a regulatory subunit, a wealth of evidence have placed the class IA PI3Ks at the forefront of drug development for the treatment of various diseases including cancer. The p110α isoform was quickly brought at the centre of attention in the field of cancer research by the discovery of cancer-specific gain-of-function mutations in PIK3CA gene in a range of human solid tumours. In contrast, p110δ PI3K was placed into the spotlight of immunity, inflammation and haematologic malignancies because of the preferential expression of this isoform in leucocytes and the rare mutations in PIK3CD gene. The last decade, however, several studies have provided evidence showing that the correlation between the PIK3CA mutations and the response to PI3K inhibition is less clear than originally considered, whereas concurrently an unexpected role of p110δ PI3K in solid tumours has being emerging. While PIK3CD is mostly non-mutated in cancer, the expression levels of p110δ protein seem to act as an intrinsic cancer-causing driver in various solid tumours including breast, prostate, colorectal and liver cancer, Merkel-Cell carcinoma, glioblastoma and neurobalstoma. Furthermore, p110δ selective inhibitors are being studied as potential single agent treatments or as combination partners in attempt to improve cancer immunotherapy, with both strategies to shown great promise for the treatment of several solid tumours. In this review, we discuss the evidence implicating the p110δ PI3K in human solid tumours, their impact on the current state of the field and the potential of using p110δ-selective inhibitors as monotherapy or combined therapy in different cancer contexts.

PI3Kδ Is a Therapeutic Target in Hepatocellular Carcinoma

Class I phosphoinositide 3-kinase (PI3K) signaling is a major pathway in human cancer development and progression. Among the four PI3K isoforms, PI3Kα and PI3Kβ are ubiquitously expressed, whereas PI3Kγ and PI3Kδ are found primarily in leukocytes. Until now, PI3K targeting in solid tumors has focused on inhibiting PI3Kα-mediated and PI3Kβ-mediated cancer cell-intrinsic PI3K activity. The role of PI3Kδ in solid tumors is unknown. Here, we evaluated the effects of PI3Kδ using established hepatocellular carcinoma (HCC) cells, malignant hepatocytes derived from patients with advanced HCC, murine models, and HCC tissues using RNA sequencing, quantitative PCR, immunoblotting, immunofluorescence, microarray, liquid chromatography-tandem mass spectrometry, and kinase assay. We established a chemical carcinogenesis model of liver malignancy that reflects the malignant phenotype and the in vivo environment of advanced HCC. In this in vivo advanced HCC-mimic system using HCC cells treated with hydrogen peroxide (H₂ O₂ ), we showed that H₂ O₂ selectively increases PI3Kδ activity while decreasing that of other class I PI3Ks. Blocking PI3Kδ activity with a PI3Kδ inhibitor or small interfering RNA-mediated PI3Kδ gene silencing inhibited HCC-cell proliferation and dampened key features of malignant HCC, including the up-regulation of telomerase reverse transcriptase (TERT). Mechanistically, H₂ O₂ induced oxidative modification of the serpin peptidase inhibitor, serpin peptidase inhibitor (SERPINA3), blocking its ubiquitin-dependent degradation and enhancing its activity as a transcriptional activator of PI3Kδ and TERT. High PI3Kδ levels in HCC were found to correlate with poor survival rates, with human advanced HCC showing positive correlations between the protein levels of oxidized SERPINA3, PI3Kδ, and TERT. Thus, PI3Kδ plays significant roles in malignant liver tumors. Conclusion: Our data identify PI3Kδ inhibition, recently approved for the treatment of human B-cell malignancies, as a potential treatment for HCC.

Pharmacological inactivation of the PI3K p110δ prevents breast tumour progression by targeting cancer cells and macrophages

Patient selection for PI3K-targeted solid cancer treatment was based on the PIK3CA/PTEN mutational status. However, it is increasingly clear that this is not a good predictor of the response of breast cancer cells to the anti-proliferative effect of PI3K inhibitors, indicating that isoform(s) other than p110α may modulate cancer cells sensitivity to PI3K inhibition. Surprisingly, we found that although no mutations in the p110δ subunit have been detected thus far in breast cancer, the expression of p110δ becomes gradually elevated during human breast cancer progression from grade I to grade III. Moreover, pharmacological inactivation of p110δ in mice abrogated the formation of tumours and the recruitment of macrophages to tumour sites and strongly affected the survival, proliferation and apoptosis of grafted tumour cells. Pharmacological inactivation of p110δ in mice with defective macrophages or in mice with normal macrophages but grafted with p110δ-lacking tumours suppressed only partly tumour growth, indicating a requisite role of p110δ in both macrophages and cancer cells in tumour progression. Adoptive transfer of δD910A/D910A macrophages into mice with defected macrophages suppressed tumour growth, eliminated the recruitment of macrophages to tumour sites and prevented metastasis compared with mice that received WT macrophages further establishing that inactivation of p110δ in macrophage prevents tumour progression. Our work provides the first in vivo evidence for a critical role of p110δ in cancer cells and macrophages during solid tumour growth and may pave the way for the use of p110δ inhibitors in breast cancer treatment.

Phosphatidylinositol 3-kinase β and δ isoforms play key roles in metastasis of prostate cancer DU145 cells

Metastasis is the main cause of the lethality of prostate cancer. Class I phosphatidylinositol 3-kinases (PI3Ks), which contain 4 isoforms, α, β, δ, and γ, are known to play important roles in cell growth, migration, invasion, and so on. However, the respective role of each PI3K isoform in cancer cell migration and invasion remains unknown. In a study that aimed to elucidate the respective role of the 4 PI3K isoforms, we investigated the change in migratory and invasive ability of DU145 cells after treatment with each PI3K isoform-specific inhibitor. Both migration and invasion of DU145 cells were potently blocked by each of the PI3Kβ inhibitors (GSK2636771 and TGX221) and PI3Kδ inhibitors (CAL101 and IC87114) while not obviously affected by PI3Kα inhibitor BYL719 or PI3Kγ inhibitor AS252424. Furthermore, knocking down PI3Kβ or PI3Kδ isoform led to a significant decrease in migration of DU145. The results suggest that PI3Kβ and PI3Kδ play key roles in prostate cancer cell migration, while PI3Kα and PI3Kγ might be redundant. Oral administration of GSK2636771 (100 mg/kg) and CAL101 (30 mg/kg) inhibited tumor growth in bone, an experimental model by intratibia injection of DU145 cells, with improved bone structure and bone mineral density analyzed by micro-computed tomography. Tissue staining indicated reduction of metastatic DU145 cells and osteoclasts in the bones of GSK2636771- and CAL101-treated mice compared to the untreated group. In summary, our results indicated the distinct roles of 4 PI3K isoforms in the migration of prostate cancer DU145 cells, and they demonstrated the in vitro and in vivo antimetastatic effect of PI3K-isoform specific inhibitors, most of which are in clinical trials.-Zhang, Z., Liu, J., Wang, Y., Tan, X., Zhao, W., Xing, X., Qiu, Y., Wang, R., Jin, M., Fan, G., Zhang, P., Zhong, Y., Kong, D. Phosphatidylinositol 3-kinase β and δ isoforms play key roles in metastasis of prostate cancer DU145 cells.

Inhibition of PI4K IIIα radiosensitizes in human tumor xenograft and immune-competent syngeneic murine tumor model

Phosphatidylinositol (PI) 4-kinase (PI4K) has emerged as a potential target for anti-cancer treatment. We recently reported that simeprevir, an anti-hepatitis C viral (HCV) agent, radiosensitized diverse human cancer cells by inhibiting PI4K IIIα in vitro. In this study, we investigated the radiosensitizing effect of simeprevir in an in vivo tumor xenograft model and the mechanism of its interaction. The immune modulatory effect of PI4K IIIα was evaluated in an immune-competent syngeneic murine tumor model.

In in vivo xenograft models using BT474 breast cancer and U251 brain tumor cells, inhibition of PI4K IIIα induced by simeprevir combined with radiation significantly delayed tumor growth compared to either treatment alone. PI4K IIIα inhibition led to eversion of the epithelial-mesenchymal transition as suggested by decreased invasion/migration and vascular tube formation. Simeprevir down-regulated PI3Kδ expression and PI3Kδ inhibition using RNA interference radiosensitized breast cancer cells. PI4K IIIα inhibition enhanced the radiosensitizing effect of anti-programmed death-ligand 1 (PD-L1) and decreased the expression of PI3Kδ, phosphorylated-Akt, and PD-L1 in breast cancer cells co-cultured with human T-lymphocytes. The immune modulatory effect in vivo was evaluated in immune-competent syngeneic 4T1 murine tumor models. Simeprevir showed significant radiosensitizing effect and immune modulatory function by affecting the CD4(+)/CD8(+) ratio of tumor infiltrating lymphocytes.

These findings suggest that targeting PI4K IIIα with an anti-HCV agent is a viable drug repositioning approach for enhancing the therapeutic efficacy of radiation therapy. The immune regulatory function of PI4K IIIα via modulation of PI3Kδ suggests a strategy for enhancing the radiosensitizing effect of immune checkpoint blockades.

Alternative splicing promotes tumour aggressiveness and drug resistance in African American prostate cancer

Clinical challenges exist in reducing prostate cancer (PCa) disparities. The RNA splicing landscape of PCa across racial populations has not been fully explored as a potential molecular mechanism contributing to race-related tumour aggressiveness. Here, we identify novel genome-wide, race-specific RNA splicing events as critical drivers of PCa aggressiveness and therapeutic resistance in African American (AA) men. AA-enriched splice variants of PIK3CD, FGFR3, TSC2 and RASGRP2 contribute to greater oncogenic potential compared with corresponding European American (EA)-expressing variants. Ectopic overexpression of the newly cloned AA-enriched variant, PIK3CD-S, in EA PCa cell lines enhances AKT/mTOR signalling and increases proliferative and invasive capacity in vitro and confers resistance to selective PI3Kδ inhibitor, CAL-101 (idelalisib), in mouse xenograft models. High PIK3CD-S expression in PCa specimens associates with poor survival. These results highlight the potential of RNA splice variants to serve as novel biomarkers and molecular targets for developmental therapeutics in aggressive PCa.

Recent advances in the use of PI3K inhibitors for glioblastoma multiforme: current preclinical and clinical development

Glioblastoma multiforme (GBM) is the most common and aggressive malignant primary tumor in the central nervous system. One of the most widely used chemotherapeutic drugs for GBM is temozolomide, which is a DNA-alkylating agent and its efficacy is dependent on MGMT methylation status. Little progress in improving the prognosis of GBM patients has been made in the past ten years, urging the development of more effective molecular targeted therapies. Hyper-activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway is frequently found in a variety of cancers including GBM, and it plays a central role in the regulation of tumor cell survival, growth, motility, angiogenesis and metabolism. Numerous PI3K inhibitors including pan-PI3K, isoform-selective and dual PI3K/mammalian target of rapamycin (mTOR) inhibitors have exhibited favorable preclinical results and entered clinical trials in a range of hematologic malignancies and solid tumors. Furthermore, combination of inhibitors targeting PI3K and other related pathways may exert synergism on suppressing tumor growth and improving patients' prognosis. Currently, only a handful of PI3K inhibitors are in phase I/II clinical trials for GBM treatment. In this review, we focus on the importance of PI3K/Akt pathway in GBM, and summarize the current development of PI3K inhibitors alone or in combination with other inhibitors for GBM treatment from preclinical to clinical studies.

TGF-β induces phosphorylation of phosphatase and tensin homolog: implications for fibrosis of the trabecular meshwork tissue in glaucoma

Fundamental cell signaling mechanisms that regulate dynamic remodeling of the extracellular matrix (ECM) in mechanically loaded tissues are not yet clearly understood. Trabecular meshwork (TM) tissue in the eye is under constant mechanical stress and continuous remodeling of ECM is crucial to maintain normal aqueous humor drainage and intraocular pressure (IOP). However, excessive ECM remodeling can cause fibrosis of the TM as in primary open-angle glaucoma (POAG) patients, and is characterized by increased resistance to aqueous humor drainage, elevated IOP, optic nerve degeneration and blindness. Increased levels of active transforming growth factor-β2 (TGF-β2) in the aqueous humor is the main cause of fibrosis of TM in POAG patients. Herein, we report a novel finding that, in TM cells, TGF-β-induced increase in collagen expression is associated with phosphorylation of phosphatase and tensin homolog (PTEN) at residues Ser380/Thr382/383. Exogenous overexpression of a mutated form of PTEN with enhanced phosphatase activity prevented the TGF-β-induced collagen expression by TM cells. We propose that rapid alteration of PTEN activity through changes in its phosphorylation status could uniquely regulate the continuous remodeling of ECM in the normal TM. Modulating PTEN activity may have high therapeutic potential to alleviating the fibrosis of TM in POAG patients.

Development and mechanistic insight into enhanced cytotoxic potential of hyaluronic acid conjugated nanoparticles in CD44 overexpressing cancer cells

The overexpression of CD44 in cancer cells reroutes number of oncogenic pathways including the central Pi3K/Akt/NF-kB pathway leading to cancer progression and malignancy. Herein, we developed hyaluronic acid-modified poly(dl-lactic-co-glycolic acid)-poly (ethylene glycol) nanoparticles (PLGA-PEG-HA NPs) for targeted delivery of TTQ (thio-tetrazolyl analog of a clinical candidate, IC87114) to CD44 overexpressing cancer cells. The PLGA-PEG co-polymer was synthesized and characterized by NMR and FTIR. The co-polymer based nanoparticles were prepared by solvent evaporation method and hyaluronic acid (HA) was conjugated on to the nanoparticle surface via EDC/NHS chemistry. The PLGA-PEG-HA NPs had a desirable particle size (<200nm) with reduced polydispersibility and exhibited spherical shape under atomic force microscope (AFM). In vitro cytotoxicity and cellular uptake studies demonstrated higher cytotoxicity and enhanced intracellular accumulation of PLGA-PEG-HA NPs compared to PLGA-PEG NPs in high CD44 expressing MiaPaca-2 cells compared to MDA-MB-231 and MCF7 cells. At the molecular level, the PLGA-PEG-HA NPs were found to be inducing premature senescence with increase in senescence associated β-galactosidase activity and senescence specific marker p21 expression through modulation of Pi3K/Akt/NF-kB signaling pathway in MiaPaca-2 cells. These findings collectively indicated that HA-modified nanoparticles might serve as a promising nanocarrier for site-specific drug delivery, and can be explored further to increase the therapeutic efficacy of anticancer drugs via targeting to CD44 over-expressing cancer cells.

Molecules in medicine mini-review: isoforms of PI3K in biology and disease

The PI3K lipid kinases are involved in signal transduction and intracellular vesicular traffic, endowing these enzymes with multiple cellular functions and important roles in normal physiology and disease. In this mini-review, we aim to distill from the vast PI3K literature the key relevant concepts for successful targeting of this pathway in disease. Of the eight isoforms of PI3K, the class I PI3Ks have been implicated in the aetiology and maintenance of various diseases, most prominently cancer, overgrowth syndromes, inflammation and autoimmunity, with emerging potential roles in metabolic and cardiovascular disorders. The development of class I PI3K inhibitors, mainly for use in cancer and inflammation, is a very active area of drug development. In 2014, an inhibitor of the p110δ isoform of PI3K was approved for the treatment of specific human B cell malignancies. The key therapeutic indications of targeting each class I PI3K isoform are summarized and discussed.

Focal adhesion kinase phosphorylates the phosphatase and tensin homolog deleted on chromosome 10 under the control of p110δ phosphoinositide-3 kinase

The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) tumor suppressor protein is regulated by various mechanisms that are not fully understood. This includes regulation by Tyr phosphorylation by a mechanism that remains elusive. Here, we show that focal adhesion kinase (FAK) phosphorylates PTEN in vitro, in cell-free systems and in cells. Furthermore, by mass spectrometry, we identified Tyr336 on PTEN as being phosphorylated by FAK. Tyr336 phosphorylation increased phosphatase activity, protein-lipid interaction, and protein stability of PTEN. In cells, including primary mouse macrophages and human cancer cell lines, FAK was found to be negatively regulated by p110δ phosphoinositide-3 kinase (PI3K), whereas the activation of FAK was positively regulated by RhoA-associated kinase (ROCK). Indeed, the phosphorylation of FAK was unexpectedly increased in macrophages derived from mice expressing kinase-dead p110δ. Pharmacologic inactivation of RhoA/ROCK reduced the phosphorylation of FAK to normal levels in cells with genetically inactivated p110δ. Likewise, pharmacologic inactivation of FAK reduced the phosphorylation of PTEN in cells expressing kinase-dead p110δ and restored the functional defects of p110δ inactivation, including Akt phosphorylation and cell proliferation. This work identifies FAK as a target of p110δ PI3K that links RhoA with PTEN and establishes for the first time that PTEN is a substrate of FAK-mediated Tyr phosphorylation.

The Unique Non-Catalytic C-Terminus of P37delta-PI3K Adds Proliferative Properties In Vitro and In Vivo

The PI3K/Akt pathway is central for numerous cellular functions and is frequently deregulated in human cancers. The catalytic subunits of PI3K, p110, are thought to have a potential oncogenic function, and the regulatory subunit p85 exerts tumor suppressor properties. The fruit fly, Drosophila melanogaster, is a highly suitable system to investigate PI3K signaling, expressing one catalytic, Dp110, and one regulatory subunit, Dp60, and both show strong homology with the human PI3K proteins p110 and p85. We recently showed that p37δ, an alternatively spliced product of human PI3K p110δ, displayed strong proliferation-promoting properties despite lacking the catalytic domain completely. Here we functionally evaluate the different domains of human p37δ in Drosophila. The N-terminal region of Dp110 alone promotes cell proliferation, and we show that the unique C-terminal region of human p37δ further enhances these proliferative properties, both when expressed in Drosophila, and in human HEK-293 cells. Surprisingly, although the N-terminal region of Dp110 and the C-terminal region of p37δ both display proliferative effects, over-expression of full length Dp110 or the N-terminal part of Dp110 decreases survival in Drosophila, whereas the unique C-terminal region of p37δ prevents this effect. Furthermore, we found that the N-terminal region of the catalytic subunit of PI3K p110, including only the Dp60 (p85)-binding domain and a minor part of the Ras binding domain, rescues phenotypes with severely impaired development caused by Dp60 over-expression in Drosophila, possibly by regulating the levels of Dp60, and also by increasing the levels of phosphorylated Akt. Our results indicate a novel kinase-independent function of the PI3K catalytic subunit.

PI3K pathway inhibitors: potential prospects as adjuncts to vaccine immunotherapy for glioblastoma

Constitutive activation of the PI3K pathway has been implicated in glioblastoma (GBM) pathogenesis. Pharmacologic inhibition can both inhibit tumor survival and downregulate expression of programmed death ligand-1, a protein highly expressed on glioma cells that strongly contributes to cancer immunosuppression. In that manner, PI3K pathway inhibitors can help optimize GBM vaccine immunotherapy. In this review, we describe and assess the potential integration of various classes of PI3K pathway inhibitors into GBM immunotherapy. While early-generation inhibitors have a wide range of immunosuppressive effects that could negate their antitumor potency, further work should better characterize how contemporary inhibitors affect the immune response. This will help determine if these inhibitors are truly a therapeutic avenue with a strong future in GBM immunotherapy.

Phosphoinositide 3-kinase p110δ promotes lumen formation through the enhancement of apico-basal polarity and basal membrane organization

Signalling triggered by adhesion to the extracellular matrix plays a key role in the spatial orientation of epithelial polarity and formation of lumens in glandular tissues. Phosphoinositide 3-kinase signalling in particular is known to influence the polarization process during epithelial cell morphogenesis. Here, using Madin-Darby canine kidney epithelial cells grown in 3D culture, we show that the p110δ isoform of phosphoinositide 3-kinase co-localizes with focal adhesion proteins at the basal surface of polarized cells. Pharmacological, siRNA- or kinase-dead-mediated inhibition of p110δ impair the early stages of lumen formation, resulting in inverted polarized cysts, with no laminin or type IV collagen assembly at cell/extracellular matrix contacts. p110δ also regulates the organization of focal adhesions and membrane localization of dystroglycan. Thus, we uncover a previously unrecognized role for p110δ in epithelial cells in the orientation of the apico-basal axis and lumen formation.

Gold nanoparticle supported phospholipid membranes as a biomimetic biosensor platform for phosphoinositide signaling detection

Enzyme mediated phosphoinositide signaling plays important regulatory roles in diverse cellular processes and has close implication in human diseases. However, detection of phosphoinositide enzymes remains a challenge because of the difficulty in discriminating the phosphorylation patterns of phosphoinositide. Here we develop a novel enzyme-activated gold nanoparticles (AuNPs) assembly strategy as a homogeneous colorimetric biosensor for activity detection of phosphoinositide kinases and phosphatases. This strategy utilizes a biomimetic mechanism of phosphoinositide signaling, in which AuNP supported phospholipid membranes are constructed to mimic the cellular membrane substrate, and AuNPs modified with the pleckstrin homology (PH) domain of cytosolic proteins are designed for specific, multivalent recognition of phosphorylated phosphoinositides. This biomimetic strategy enables efficient enzymatic reactions of the substrate and highly selective detection of target enzyme. The biosensor is demonstrated for the detection of phosphoinositide 3-kinase (PI3K) and phosphatase with tensin homology (PTEN). The results revealed that it allows sensitive, rapid visual detection of the enzymes with pM detection limits and four-decade wide dynamic ranges, and is capable of detecting enzyme activities in complex cell lysate samples. This biosensor might provide a general biosensor platform for high-throughput detection of phosphoinositide enzymes with high sensitivity and selectivity in biomedical research and clinical diagnostics.

PIK3CA gene amplification and PI3K p110α protein expression in breast carcinoma

A family of PI3Ks is the lipid kinases, which enhance intracellular pools of phosphatidyl inositol 3,4,5-tri-phosphate (PIP3) through phosphorylating its precursor. Amplifications and deletions of genes, as well as somatic missense of the PIK3CA gene have been described in many human cancer varieties, including of the brain, colon, liver, lung and stomach. Immunohistochemistry and Real-time quantitative PCR tests were used to determine the PIK3CA gene amplification (gene copy number) and to detect protein expression, respectively. The results obtained were analysed and the ratio of PIK3CA to β-actin gene copy number was calculated. Positive gene amplification of PIK3CA was appointed as a copy number of ≥4. Also, PI3K p110α protein expression was scored from 0 to 3+ and the scores of 2+ and 3+ were considered as positive for PI3K p110α protein expression. We studied 50 breast carcinoma samples for PI3K p110α protein expression and PIK3CA gene copy numbers. In general, 36 out of 50 (72%) breast carcinoma samples showed a significant increase in PIK3CA gene amplification. 12 out of 50 (24%) showed positive staining, and 38 out of 50 (76%) showed negative staining for PI3K p110α expression. We have identified no significant relationship between PIK3CA amplification, race (p= 0.630) and histological type (p=0. 731) in breast carcinoma, but correlation of PIK3CA amplification and age showed a significant relationship (p=0. 003) between them. No significant relationship has been identified in correlation of PI3K p110α protein expression compared to age (p=0. 284), race (p=0. 546) and histological type (p=0. 285). Amplification of PIK3CA was frequent in breast carcinoma and occurs in stages of breast carcinoma. Our result shows that there is a relationship between gene amplification and age in breast carcinoma. We suggest that PIK3CA is significant in breast tumorigenesis serve as a prevalent mechanism contributes to the oncogenic activation pathway of PIK3CA in breast cancer.

PI3Kδ inhibition augments the efficacy of rapamycin in suppressing proliferation of Epstein-Barr virus (EBV)+ B cell lymphomas

Posttransplant lymphoproliferative disorder (PTLD) continues to be a devastating and potentially life-threatening complication in organ transplant recipients. PTLD is associated with EBV infection and can result in malignant B cell lymphomas. Here we demonstrate that the PI3K/Akt/mTOR pathway is highly activated in EBV+ B cell lymphoma lines derived from patients with PTLD. Treatment with the mTORC1 inhibitor Rapamycin (RAPA) partially inhibited the proliferation of EBV+ B cell lines. Resistance to RAPA treatment correlated with high levels of Akt phosphorylation. An mTORC1/2 inhibitor and a PI3K/mTOR dual inhibitor suppressed Akt phosphorylation and showed a greater anti-proliferative effect on EBV+ B lymphoma lines compared to RAPA. EBV+ B cell lymphoma lines expressed high levels of PI3Kδ. We demonstrate that PI3Kδ is responsible for Akt activation in EBV+ B cell lymphomas, and that selective inhibition of PI3Kδ by either siRNA, or a small molecule inhibitor, augmented the anti-proliferative effect of RAPA on EBV+ B cell lymphomas. These results suggest that PI3Kδ is a novel, potential therapeutic target for the treatment of EBV-associated PTLD and that combined blockade of PI3Kδ and mTOR provides increased efficacy in inhibiting proliferation of EBV+ B cell lymphomas.

Dissecting Major Signaling Pathways throughout the Development of Prostate Cancer

Prostate cancer (PCa) is one of the most common malignancies found in males. The development of PCa involves several mutations in prostate epithelial cells, usually linked to developmental changes, such as enhanced resistance to apoptotic death, constitutive proliferation, and, in some cases, to differentiation into an androgen deprivation-resistant phenotype, leading to the appearance of castration-resistant PCa (CRPCa), which leads to a poor prognosis in patients. In this review, we summarize recent findings concerning the main deregulations into signaling pathways that will lead to the development of PCa and/or CRPCa. Key mutations in some pathway molecules are often linked to a higher prevalence of PCa, by directly affecting the respective cascade and, in some cases, by deregulating a cross-talk node or junction along the pathways. We also discuss the possible environmental and nonenvironmental inducers for these mutations, as well as the potential therapeutic strategies targeting these signaling pathways. A better understanding of how some risk factors induce deregulation of these signaling pathways, as well as how these deregulated pathways affect the development of PCa and CRPCa, will further help in the development of new treatments and prevention strategies for this disease.

p110δ PI3 kinase pathway: emerging roles in cancer

Class IA PI3Ks consists of three isoforms of the p110 catalytic subunit designated p110α, p110β, and p110δ which are encoded by three separate genes. Gain-of-function mutations on PIK3CA gene encoding for p110α isoform have been detected in a wide variety of human cancers whereas no somatic mutations of genes encoding for p110β or p110δ have been reported. Unlike p110α and p110β which are ubiquitously expressed, p110δ is highly enriched in leukocytes and thus the p110δ PI3K pathway has attracted more attention for its involvement in immune disorders. However, findings have been accumulated showing that the p110δ PI3K plays a seminal role in the development and progression of some hematologic malignancies. A wealth of knowledge has come from studies showing the central role of p110δ PI3K in B-cell functions and B-cell malignancies. Further data have documented that wild-type p110δ becomes oncogenic when overexpressed in cell culture models and that p110δ is the predominant isoform expressed in some human solid tumor cells playing a prominent role in these cells. Genetic inactivation of p110δ in mice models and highly-selective inhibitors of p110δ have demonstrated an important role of this isoform in differentiation, growth, survival, motility, and morphology with the inositol phosphatase PTEN to play a critical role in p110δ signaling. In this review, we summarize our understanding of the p110δ PI3K signaling pathway in hematopoietic cells and malignancies, we highlight the evidence showing the oncogenic potential of p110δ in cells of non-hematopoietic origin and we discuss perspectives for potential novel roles of p110δ PI3K in cancer.

Genomic Determinants of PI3K Pathway Inhibitor Response in Cancer

The phosphoinositide 3-kinase (PI3K) pathway is frequently activated in cancer as a result of genetic (e.g., amplifications, mutations, deletions) and epigenetic (e.g., methylation, regulation by non-coding RNAs) aberrations targeting its key components. Several lines of evidence demonstrate that tumors from different anatomical sites depend on the continued activation of this pathway for the maintenance of their malignant phenotype. The PI3K pathway therefore is an attractive candidate for therapeutic intervention, and inhibitors targeting different components of this pathway are in various stages of clinical development. Burgeoning data suggest that the genomic features of a given tumor determine its response to targeted small molecule inhibitors. Importantly, alterations of different components of the PI3K pathway may result in distinct types of dependencies and response to specific therapeutic agents. In this review, we will focus on the genomic determinants of response to PI3K, dual PI3K/mechanistic target of rapamycin (mTOR), mTOR, and AKT inhibitors in cancer identified in preclinical models and clinical trials to date, and the development of molecular tools for the stratification of cancer patients.