BKM-120 (Buparlisib): A Phosphatidyl-Inositol-3 Kinase Inhibitor with Anti-Invasive Properties in Glioblastoma

Cu(II)/PTABS-Promoted, Regioselective SNAr Amination of Polychlorinated Pyrimidines with Mechanistic Understanding

Regioselective amination of polyhalogenated heteroarenes (especially pyrimidines) has extensive synthetic and commercial relevance for drug synthesis applications but is plagued by the lack of effective synthetic strategies. Herein, we report the Cu(II)/PTABS-promoted highly regioselective nucleophilic aromatic substitution (S_NAr) of polychlorinated pyrimidines assisted by DFT predictions of the bond dissociation energies of different C-Cl bonds. The unique reactivity of Cu(II)-PTABS has been attributed to the coordination/activation mechanism that has been known to operate in these reactions, but further insights into the catalytic species have also been provided.

Current State and Future Challenges for PI3K Inhibitors in Cancer Therapy

The phosphoinositide 3 kinase (PI3K)-protein kinase B (PKB/AKT)-mammalian target of the rapamycin (mTOR) axis is a key signal transduction system that links oncogenes and multiple receptor classes which are involved in many essential cellular functions. Aberrant PI3K signalling is one of the most commonly mutated pathways in cancer. Consequently, more than 40 compounds targeting key components of this signalling network have been tested in clinical trials among various types of cancer. As the oncogenic activation of the PI3K/AKT/mTOR pathway often occurs alongside mutations in other signalling networks, combination therapy should be considered. In this review, we highlight recent advances in the knowledge of the PI3K pathway and discuss the current state and future challenges of targeting this pathway in clinical practice.

A Drug Screening Reveals Minocycline Hydrochloride as a Therapeutic Option to Prevent Breast Cancer Cells Extravasation across the Blood-Brain Barrier

Among breast cancer (BC) patients, 15-25% develop BC brain metastases (BCBM), a severe condition due to the limited therapeutic options, which points to the need for preventive strategies. We aimed to find a drug able to boost blood-brain barrier (BBB) properties and prevent BC cells (BCCs) extravasation, among PI3K, HSP90, and EGFR inhibitors and approved drugs. We used BCCs (4T1) and BBB endothelial cells (b.End5) to identify molecules with toxicity to 4T1 cells and safe for b.End5 cells. Moreover, we used those cells in mixed cultures to perform a high-throughput microscopy screening of drugs' ability to ameliorate BBB properties and prevent BCCs adhesion and migration across the endothelium, as well as to analyse miRNAs expression and release profiles. KW-2478, buparlisib, and minocycline hydrochloride (MH) promoted maximal expression of the junctional protein β-catenin and induced 4T1 cells nucleus changes. Buparlisib and MH further decreased 4T1 adhesion. MH was the most promising in preventing 4T1 migration and BBB disruption, tumour and endothelial cytoskeleton-associated proteins modifications, and miRNA deregulation. Our data revealed MH's ability to improve BBB properties, while compromising BCCs viability and interaction with BBB endothelial cells, besides restoring miRNAs' homeostasis, paving the way for MH repurposing for BCBM prevention.

Small Molecule Inhibitors in Adult High-Grade Glioma: From the Past to the Future

Glioblastoma is the most common primary malignant tumor in the brain and has a dismal prognosis despite patients accepting standard therapies. Alternation of genes and deregulation of proteins, such as receptor tyrosine kinase, PI3K/Akt, PKC, Ras/Raf/MEK, histone deacetylases, poly (ADP-ribose) polymerase (PARP), CDK4/6, branched-chain amino acid transaminase 1 (BCAT1), and Isocitrate dehydrogenase (IDH), play pivotal roles in the pathogenesis and progression of glioma. Simultaneously, the abnormalities change the cellular biological behavior and microenvironment of tumor cells. The differences between tumor cells and normal tissue become the vulnerability of tumor, which can be taken advantage of using targeted therapies. Small molecule inhibitors, as an important part of modern treatment for cancers, have shown significant efficacy in hematologic cancers and some solid tumors. To date, in glioblastoma, there have been more than 200 clinical trials completed or ongoing in which trial designers used small molecules as monotherapy or combination regimens to correct the abnormalities. In this review, we summarize the dysfunctional molecular mechanisms and highlight the outcomes of relevant clinical trials associated with small-molecule targeted therapies. Based on the outcomes, the main findings were that small-molecule inhibitors did not bring more benefit to newly diagnosed glioblastoma, but the clinical studies involving progressive glioblastoma usually claimed “noninferiority” compared with historical results. However, as to the clinical inferiority trial, similar dosing regimens should be avoided in future clinical trials.

Therapeutic Options in Neuro-Oncology

One of the biggest challenges in neuro-oncology is understanding the complexity of central nervous system tumors, such as gliomas, in order to develop suitable therapeutics. Conventional therapies in malignant gliomas reconcile surgery and radiotherapy with the use of chemotherapeutic options such as temozolomide, chloroethyl nitrosoureas and the combination therapy of procarbazine, lomustine and vincristine. With the unraveling of deregulated cancer cell signaling pathways, targeted therapies have been developed. The most affected signaling pathways in glioma cells involve tyrosine kinase receptors and their downstream pathways, such as the phosphatidylinositol 3-kinases (PI3K/AKT/mTOR) and mitogen-activated protein kinase pathways (MAPK). MAPK pathway inhibitors include farnesyl transferase inhibitors, Ras kinase inhibitors and mitogen-activated protein extracellular regulated kinase (MEK) inhibitors, while PI3K/AKT/mTOR pathway inhibitors are divided into pan-inhibitors, PI3K/mTOR dual inhibitors and AKT inhibitors. The relevance of the immune system in carcinogenesis has led to the development of immunotherapy, through vaccination, blocking of immune checkpoints, oncolytic viruses, and adoptive immunotherapy using chimeric antigen receptor T cells. In this article we provide a comprehensive review of the signaling pathways underlying malignant transformation, the therapies currently used in the treatment of malignant gliomas and further explore therapies under development, including several ongoing clinical trials.

BKM120 alters the migration of doublecortin-positive cells in the dentate gyrus of mice

BKM120 is an inhibitor of class I phosphoinositide 3-kinases and its anti-cancer effects have been demonstrated in various solid cancer models. BKM120 is highly brain permeable and has been reported to induce mood disturbances in clinical trials. Therefore, we examined whether BKM120 produces anxiety- and depression-like behaviors in mice, as with patients receiving BKM120 in clinical trials. In this study, repeated BKM120 treatment (2.0 or 5.0mg/kg, i.p., five times at 12-h interval) significantly induced anxiety- and depression-like behaviors in mice. Although abnormal changes in hippocampal neurogenesis have been suggested to, at least in part, associated with the pathogenesis of depression and anxiety, BKM120 did not affect the incorporation of 5-bromo-2'-deoxyuridine or the expression of doublecortin (DCX); however, it significantly enhanced the radial migration of DCX-positive cells in the dentate gyrus. BKM120-induced changes in migration were not accompanied by obvious neuronal damage in the hippocampus. Importantly, BKM120-induced anxiety- and depression-like behaviors were positively correlated with the extent of DCX-positive cell migration. Concomitantly, p-Akt expression was significantly decreased in the dentate gyrus. Moreover, the expression of p-c-Jun N-terminal kinase (JNK), p-DCX, and Ras homolog family member A (RhoA)-GTP decreased significantly, particularly in aberrantly migrated DCX-positive cells. Together, the results suggest that repeated BKM120 treatment enhances the radial migration of DCX-positive cells and induces anxiety- and depression-like behaviors by regulating the activity of Akt, JNK, DCX, and RhoA in the dentate gyrus. It also suggests that the altered migration of adult-born neurons in the dentate gyrus plays a role in mood disturbances.

PI3K/AKT Signaling Tips the Balance of Cytoskeletal Forces for Cancer Progression

The PI3K/AKT signaling pathway plays essential roles in multiple cellular processes, which include cell growth, survival, metabolism, and motility. In response to internal and external stimuli, the PI3K/AKT signaling pathway co-opts other signaling pathways, cellular components, and cytoskeletal proteins to reshape individual cells. The cytoskeletal network comprises three main components, which are namely the microfilaments, microtubules, and intermediate filaments. Collectively, they are essential for many fundamental structures and cellular processes. In cancer, aberrant activation of the PI3K/AKT signaling cascade and alteration of cytoskeletal structures have been observed to be highly prevalent, and eventually contribute to many cancer hallmarks. Due to their critical roles in tumor progression, pharmacological agents targeting PI3K/AKT, along with cytoskeletal components, have been developed for better intervention strategies against cancer. In our review, we first discuss existing evidence in-depth and then build on recent advances to propose new directions for therapeutic intervention.

Role of Inflammatory Mediators, Macrophages, and Neutrophils in Glioma Maintenance and Progression: Mechanistic Understanding and Potential Therapeutic Applications

Simple Summary

The tumor microenvironment is a complex network comprised of neoplastic and a variety of immune cells, proteins, and inflammatory mediators. Previous studies have shown that during cancer progression, diverse inflammatory molecules, either directly or indirectly via recruiting immune cells, support the process of carcinogenesis. The present review focuses on the mechanistic understanding of the oncogenic role of these inflammatory mediators and immune cells, particularly tumor-associated macrophages (TAMs) and tumor-associated neutrophils (TANs) in glioma maintenance and progression. Moreover, the potential therapeutic benefits of targeting inflammatory mediators, immune cells, and associated signaling pathways in glioma genesis have also been discussed.

Abstract

Gliomas are the most common, highly malignant, and deadliest forms of brain tumors. These intra-cranial solid tumors are comprised of both cancerous and non-cancerous cells, which contribute to tumor development, progression, and resistance to the therapeutic regimen. A variety of soluble inflammatory mediators (e.g., cytokines, chemokines, and chemotactic factors) are secreted by these cells, which help in creating an inflammatory microenvironment and contribute to the various stages of cancer development, maintenance, and progression. The major tumor infiltrating immune cells of the tumor microenvironment include TAMs and TANs, which are either recruited peripherally or present as brain-resident macrophages (microglia) and support stroma for cancer cell expansion and invasion. These cells are highly plastic in nature and can be polarized into different phenotypes depending upon different types of stimuli. During neuroinflammation, glioma cells interact with TAMs and TANs, facilitating tumor cell proliferation, survival, and migration. Targeting inflammatory mediators along with the reprogramming of TAMs and TANs could be of great importance in glioma treatment and may delay disease progression. In addition, an inhibition of the key signaling pathways such as NF-κB, JAK/STAT, MAPK, PI3K/Akt/mTOR, and TLRs, which are activated during neuroinflammation and have an oncogenic role in glioblastoma (GBM), can exert more pronounced anti-glioma effects.

Phase I, open-label, multicentre study of buparlisib in combination with temozolomide or with concomitant radiation therapy and temozolomide in patients with newly diagnosed glioblastoma

Background

Most glioblastoma tumours exhibit intrinsic phosphatidylinositol 3-kinase (PI3K) pathway activation. Preclinical in vitro and in vivo models suggest that buparlisib (an oral pan-PI3K inhibitor) can have an effect on glioblastoma directly and by enhancing the activity of radiation and of temozolomide.

Methods

This was a phase I, two-stage, multicentre, open-label, dose-escalation study of buparlisib in combination with temozolomide and radiotherapy in patients with newly diagnosed glioblastoma. In stage I, patients who completed the concomitant phase of combination of temozolomide and radiation prior to study entry received buparlisib in combination with temozolomide. In stage II, patients received buparlisib in combination with temozolomide and radiotherapy in the concomitant phase and temozolomide in the adjuvant treatment phase. The primary objective was to estimate the maximum tolerated dose (MTD) of buparlisib when combined with the approved first-line treatment of temozolomide and radiotherapy.

Results

The MTD of buparlisib in combination with temozolomide at stage I (adjuvant phase only) was 80 mg/day, which was used as the starting dose in stage II. The MTD of buparlisib in combination with temozolomide and radiotherapy in stage II (concomitant + adjuvant phase) was not determined due to the observed dose-limiting toxicities and treatment discontinuations due to adverse events (AEs). In stage I, the most commonly reported AEs were nausea (72.7%) and fatigue (59.1%). In stage II, the most commonly reported AEs were fatigue and nausea (56.3% each). No on-treatment deaths were reported during the study.

Conclusion

Considering that the primary objective of estimating the MTD was not achieved in addition to the observed challenging safety profile of buparlisib in combination with radiotherapy and temozolomide, Novartis decided not to pursue the development of buparlisib in newly diagnosed glioblastoma.

Trial registration number

ClinicalTrials.gov identifier: NCT01473901.

Buparlisib plus carboplatin or lomustine in patients with recurrent glioblastoma: a phase Ib/II, open-label, multicentre, randomised study

Background

Glioblastoma relapse is associated with activation of phosphatidylinositol 3-kinase (PI3K) signalling pathway. In preclinical studies, the pan-PI3K inhibitor buparlisib showed antitumour activity in glioma models.

Methods

This was a two-part, multicentre, phase Ib/II study in patients with recurrent glioblastoma pretreated with radiotherapy and temozolomide standard of care. Patients received buparlisib (80 mg or 100 mg once daily) plus carboplatin (area under the curve (AUC)=5 every 3 weeks), or buparlisib (60 mg once daily) plus lomustine (100 mg/m² every 6 weeks). The primary endpoint was to determine the maximum tolerable dose (MTD) and/or recommended phase II dose of buparlisib plus carboplatin or lomustine.

Results

Between 28 February 2014 and 7 July 2016, 35 patients were enrolled and treated with buparlisib plus carboplatin (n=17; buparlisib (80 mg) plus carboplatin, n=3; and buparlisib (100 mg) plus carboplatin, n=14), or buparlisib (60 mg) plus lomustine (n=18). The MTD of buparlisib was determined to be 100 mg per day in combination with carboplatin at an AUC of 5 every 3 weeks. The MTD of buparlisib in combination with lomustine could not be determined as it did not satisfy the MTD criteria per the Bayesian logistic regression model.

Conclusion

The overall safety profile of buparlisib remained unchanged, and no new or unexpected safety findings were reported in this study. Preliminary assessment for both combinations did not demonstrate sufficient antitumour activity compared with historical data on single-agent carboplatin or lomustine.

Trial registration number

NCT01934361.

Room-Temperature Amination of Chloroheteroarenes in Water by a Recyclable Copper(II)-Phosphaadamantanium Sulfonate System

Buchwald-Hartwig amination of chloroheteroarenes has been a challenging synthetic process, with very few protocols promoting this important transformation at ambient temperature. The current report discusses about an efficient copper-based catalytic system (Cu/PTABS) for the amination of chloroheteroarenes at ambient temperature in water as the sole reaction solvent, a combination that is first to be reported. A wide variety of chloroheteroarenes could be coupled efficiently with primary and secondary amines as well as selected amino acid esters under mild reaction conditions. Catalytic efficiency of the developed protocol also promotes late-stage functionalization of active pharmaceutical ingredients (APIs) such as antibiotics (floxacins) and anticancer drugs. The catalytic system also performs efficiently at a very low concentration of 0.0001 mol % (TON = 980,000) and can be recycled 12 times without any appreciable loss in activity. Theoretical calculations reveal that the π-acceptor ability of the ligand PTABS is the main reason for the appreciably high reactivity of the catalytic system. Preliminary characterization of the catalytic species in the reaction was carried out using UV-VIS and ESR spectroscopy, providing evidence for the Cu(II) oxidation state.

A Systematic Review of Glioblastoma-Targeted Therapies in Phases II, III, IV Clinical Trials

Glioblastoma (GBM), the most frequent and aggressive glial tumor, is currently treated as first line by the Stupp protocol, which combines, after surgery, radiotherapy and chemotherapy. For recurrent GBM, in absence of standard treatment or available clinical trials, various protocols including cytotoxic drugs and/or bevacizumab are currently applied. Despite these heavy treatments, the mean overall survival of patients is under 18 months. Many clinical studies are underway. Based on clinicaltrials.org and conducted up to 1 April 2020, this review lists, not only main, but all targeted therapies in phases II-IV of 257 clinical trials on adults with newly diagnosed or recurrent GBMs for the last twenty years. It does not involve targeted immunotherapies and therapies targeting tumor cell metabolism, that are well documented in other reviews. Without surprise, the most frequently reported drugs are those targeting (i) EGFR (40 clinical trials), and more generally tyrosine kinase receptors (85 clinical trials) and (ii) VEGF/VEGFR (75 clinical trials of which 53 involving bevacizumab). But many other targets and drugs are of interest. They are all listed and thoroughly described, on an one-on-one basis, in four sections related to targeting (i) GBM stem cells and stem cell pathways, (ii) the growth autonomy and migration, (iii) the cell cycle and the escape to cell death, (iv) and angiogenesis.

Research update on the anticancer effects of buparlisib

Buparlisib is a highly efficient and selective PI3K inhibitor and a member of the 2,6-dimorpholinopyrimidine-derived family of compounds. It selectively inhibits four isomers of PI3K, PI3Kα, PI3Kβ, PI3Kγ and PI3Kδ, by competitively binding the lipid kinase domain on adenosine 5'-triphosphate (ATP), and serves an important role in inhibiting proliferation, promoting apoptosis and blocking angiogenesis, predominantly by antagonizing the PI3K/AKT pathway. Buparlisib has been confirmed to have a clinical effect in patients with solid tumors and hematological malignancies. A global, phase II clinical trial with buparlisib and paclitaxel in head and neck squamous cell carcinoma has now been completed, with a manageable safety profile. Buparlisib currently has fast-track status with the United States Food and Drug Administration. The present review examined the biochemical structure, pharmacokinetic characteristics, preclinical data and ongoing clinical studies of buparlisib. The various mechanisms of influence of buparlisib in tumors, particularly in preclinical research, were summarized, providing a theoretical basis and direction for basic research on and clinical treatment with buparlisib.

Targeted inhibition of cooperative mutation- and therapy-induced AKT activation in AML effectively enhances response to chemotherapy

Most AML patients exhibit mutational activation of the PI3K/AKT signaling pathway, which promotes downstream effects including growth, survival, DNA repair, and resistance to chemotherapy. Herein we demonstrate that the inv(16)/KIT^D816Y AML mouse model exhibits constitutive activation of PI3K/AKT signaling, which was enhanced by chemotherapy-induced DNA damage through DNA-PK-dependent AKT phosphorylation. Strikingly, inhibitors of either PI3K or DNA-PK markedly reduced chemotherapy-induced AKT phosphorylation and signaling leading to increased DNA damage and apoptosis of inv(16)/KIT^D816Y AML cells in response to chemotherapy. Consistently, combinations of chemotherapy and PI3K or DNA-PK inhibitors synergistically inhibited growth and survival of clonogenic AML cells without substantially inhibiting normal clonogenic bone marrow cells. Moreover, treatment of inv(16)/KIT^D816Y AML mice with combinations of chemotherapy and PI3K or DNA-PK inhibitors significantly prolonged survival compared to untreated/single-treated mice. Mechanistically, our findings implicate that constitutive activation of PI3K/AKT signaling driven by mutant KIT, and potentially other mutational activators such as FLT3 and RAS, cooperates with chemotherapy-induced DNA-PK-dependent activation of AKT to promote survival, DNA repair, and chemotherapy resistance in AML. Hence, our study provides a rationale to select AML patients exhibiting constitutive PI3K/AKT activation for simultaneous treatment with chemotherapy and inhibitors of DNA-PK and PI3K to improve chemotherapy response and clinical outcome.

The PTEN Conundrum: How to Target PTEN-Deficient Prostate Cancer

Loss of the tumor suppressor phosphatase and tensin homologue deleted on chromosome 10 (PTEN), which negatively regulates the PI3K-AKT-mTOR pathway, is strongly linked to advanced prostate cancer progression and poor clinical outcome. Accordingly, several therapeutic approaches are currently being explored to combat PTEN-deficient tumors. These include classical inhibition of the PI3K-AKT-mTOR signaling network, as well as new approaches that restore PTEN function, or target PTEN regulation of chromosome stability, DNA damage repair and the tumor microenvironment. While targeting PTEN-deficient prostate cancer remains a clinical challenge, new advances in the field of precision medicine indicate that PTEN loss provides a valuable biomarker to stratify prostate cancer patients for treatments, which may improve overall outcome. Here, we discuss the clinical implications of PTEN loss in the management of prostate cancer and review recent therapeutic advances in targeting PTEN-deficient prostate cancer. Deepening our understanding of how PTEN loss contributes to prostate cancer growth and therapeutic resistance will inform the design of future clinical studies and precision-medicine strategies that will ultimately improve patient care.

Divergent Roles of PI3K Isoforms in PTEN-Deficient Glioblastomas

Loss of PTEN, the negative regulator of PI3K activity, is frequent in glioblastomas (GBMs). However, the role of the two major PI3K isoforms, p110α and p110β, in PTEN-deficient gliomagenesis remains unknown. We show that PTEN-deficient GBM largely depends on p110α for proliferation and p110β for migration. Genetic ablation of either isoform delays tumor progression in mice, but only ablating both isoforms completely blocks GBM driven by the concurrent ablation of Pten and p53. BKM120 (buparlisib) treatment only modestly prolongs survival in mice bearing intracranial Pten/p53 null tumors due to partial pathway inhibition. BKM120 extends the survival of mice bearing intracranial tumors in which p110β, but not p110α, has been genetically ablated in the Pten/p53 null glioma, indicating that BKM120 fails to inhibit p110β effectively. Our study suggests that the failure of PI3K inhibitors in GBM may be due to insufficient inhibition of p110β and indicates a need to develop brain-penetrant p110α/β inhibitors.

Xie et al. show that p110α and p110β isoforms of PI3K play overlapping and divergent roles in PTEN-deficient glioblastomas, suggesting the importance of blocking both PI3K isoforms to effectively treat PTEN-deficient glioblastomas. Moreover, this study also provides a potential mechanism explaining the failure of BKM120 in the clinic.

A high-throughput drug combination screen identifies an anti-glioma synergism between TH588 and PI3K inhibitors

Background

Glioblastoma multiforme (GBM) is the most common and lethal type of primary brain tumor. More than half of GBMs contain mutation(s) of PTEN/PI3K/AKT, making inhibitors targeting the PI3K pathway very attractive for clinical investigation. However, so far, PI3K/AKT/mTOR inhibitors have not achieved satisfactory therapeutic effects in clinical trials of GBM. In this study, we aimed to develop a high-throughput screening method for high-throughput identification of potential targeted agents that synergize with PI3K inhibitors in GBM.

Methods

A Sensitivity Index (SI)-based drug combination screening method was established to evaluate the interactions between BKM120, a pan-PI3K inhibitor, and compounds from a library of 606 target-selective inhibitors. Proliferation, colony and 3D spheroid formation assays, western blotting, comet assay, γ-H2AX staining were used to evaluate the anti-glioma effects of the top-ranked candidates. The drug combination effects were analyzed by the Chou-Talalay method.

Results

Six compounds were successfully identified from the drug screen, including three previously reported compounds that cause synergistic antitumor effects with PI3K/mTOR inhibitors. TH588, an putative MTH1 inhibitor exhibited significant synergy with BKM120 in suppressing the proliferation, colony formation and 3D spheroid formation of GBM cells. Further investigation revealed that both DNA damage and apoptosis were markedly enhanced upon combination treatment with TH588 and BKM120. Finally, activation of PI3K or overexpression of AKT compromised the anti-glioma efficacy of TH588.

Conclusions

The screening method developed in this study demonstrated its usefulness in the rapid identification of synergistic drug combinations of PI3K inhibitors and targeted agents.

Effective Treatment of Metastatic Melanoma by Combining MAPK and PI3K Signaling Pathway Inhibitors

Malignant melanoma is the most aggressive type of skin cancer and is closely associated with the development of brain metastases. Despite aggressive treatment, the prognosis has traditionally been poor, necessitating improved therapies. In melanoma, the mitogen activated protein kinase and the phosphoinositide 3-kinase signaling pathways are commonly altered, and therapeutically inhibiting one of the pathways often upregulates the other, leading to resistance. Thus, combined treatment targeting both pathways is a promising strategy to overcome this. Here, we studied the in vitro and in vivo effects of the PI3K inhibitor buparlisib and the MEK1/2 inhibitor trametinib, used either as targeted monotherapies or in combination, on patient-derived melanoma brain metastasis cell lines. Scratch wound and trans-well assays were carried out to assess the migratory capacity of the cells upon drug treatment, whereas flow cytometry, apoptosis array and Western blots were used to study apoptosis. Finally, an in vivo treatment experiment was carried out on NOD/SCID mice. We show that combined therapy was more effective than monotherapy. Combined treatment also more effectively increased apoptosis, and inhibited tumor growth in vivo. This suggests a clinical potential of combined treatment to overcome ceased treatment activity which is often seen after monotherapies, and strongly encourages the evaluation of the treatment strategy on melanoma patients with brain metastases.

PI3K-AKT-mTOR and NFκB Pathways in Ovarian Cancer: Implications for Targeted Therapeutics

Ovarian cancer is the most lethal gynecologic malignancy in the United States, with an estimated 22,530 new cases and 13,980 deaths in 2019. Recent studies have indicated that the phosphoinositol 3 kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR), as well as the nuclear factor-κ light chain enhancer of activated B cells (NFκB) pathways are highly mutated and/or hyper-activated in a majority of ovarian cancer patients, and are associated with advanced grade and stage disease and poor prognosis. In this review, we will investigate PI3K/AKT/mTOR and their interconnection with NFκB pathway in ovarian cancer cells.

Tubulin mRNA stability is sensitive to change in microtubule dynamics caused by multiple physiological and toxic cues

The localization, mass, and dynamics of microtubules are important in many processes. Cells may actively monitor the state of their microtubules and respond to perturbation, but how this occurs outside mitosis is poorly understood. We used gene-expression analysis in quiescent cells to analyze responses to subtle and strong perturbation of microtubules. Genes encoding α-, β, and γ-tubulins (TUBAs, TUBBs, and TUBGs), but not δ- or ε-tubulins (TUBDs or TUBEs), exhibited the strongest differential expression response to microtubule-stabilizing versus destabilizing drugs. Quantitative PCR of exon versus intron sequences confirmed that these changes were caused by regulation of tubulin mRNA stability and not transcription. Using tubulin mRNA stability as a signature to query the Gene Expression Omnibus (GEO) database, we find that tubulin genes respond to toxins known to damage microtubules. Importantly, we find many other experimental perturbations, including multiple signaling and metabolic inputs that trigger tubulin differential expression, suggesting their novel, to our knowledge, role in the regulation of the microtubule cytoskeleton. Mechanistic follow-up confirms that one important physiological signal, phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) activity, indeed regulates tubulin mRNA stability via changes in microtubule dynamics. We propose that tubulin gene expression is regulated as part of many coordinated biological responses, with wide implications in physiology and toxicology. Furthermore, we present a new way to discover microtubule regulation using transcriptomics.

The PI3K inhibitor buparlisib suppresses osteoclast formation and tumour cell growth in bone metastasis of lung cancer, as evidenced by multimodality molecular imaging

Non‑small cell lung cancer (NSCLC) metastasis commonly occurs in bone, which often results in pathological fractures. Sustained phosphoinositide‑3‑kinase (PI3K) signalling promotes the growth of PI3K‑dependent NSCLC and elevates osteoclastogenic potential. The present study investigated the effects of a PI3K inhibitor on NSCLC growth in bone and osteoclast formation, and aimed to determine whether it could control symptoms associated with bone metastasis. A bone metastasis xenograft model was established by implanting NCI‑H460‑luc2 lung cancer cells, which contain a phosphatidylinositol‑​4,5‑bisphosphate 3‑kinase catalytic subunit α mutation, into the right tibiae of mice. After 1 week, the tumours were challenged with a PI3K inhibitor (buparlisib) or blank control for 3 weeks. Tumour growth and burden were longitudinally assessed in vivo via reporter gene bioluminescence imaging (BLI), small animal positron emission tomography/computed tomography (CT) [18F‑fluorodeoxyglucose (18F‑FDG)] and single‑photon emission computed tomography/CT [99mTc‑methylene diphosphonate (99mTc‑MDP)] imaging. Tibia sections of intraosseous NCI‑H460 tumours were analysed by immunohistochemistry (IHC), western blotting and flow cytometry. Dynamic weight bearing (DWB) tests were further performed to examine the improvement of symptoms associated with bone metastasis during the entire study. Administration of buparlisib significantly inhibited the progression of bone metastasis of NSCLC, as evidenced by significantly reduced uptake of 18F‑FDG, 99mTc‑MDP and BLI signals in the treated lesions. In addition, buparlisib appeared to inhibit the expression of tartrate‑resistant acid phosphatase and receptor activator of nuclear factor‑κB ligand, as determined by IHC. Buparlisib also resulted in increased cell apoptosis, as determined by a higher percentage of Annexin V staining and increased caspase 3 expression. Furthermore, buparlisib significantly increased weight‑bearing capacity, as revealed by DWB tests. The PI3K inhibitor, buparlisib, suppressed osteoclast formation in vivo, and exhibited antitumour activity, thus leading to increased weight‑bearing ability in mice with bone metastasis of lung cancer. Therefore, targeting the PI3K pathway may be a potential therapeutic strategy that prevents the structural skeletal damage associated with bone metastasis of lung cancer.

Lipid phosphatases SKIP and SHIP2 regulate fibronectin-dependent cell migration in glioblastoma

Cell migration is an important process that occurs during development and has also been linked to the motility of cancer cells. Cytoskeleton reorganization takes place in the migration process leading to lamellipodia formation. Understanding the molecular underpinnings of cell migration is particularly important in studies of glioblastoma, a highly invasive and aggressive cancer type. Two members of the phosphoinositide 5-phosphatase family, SKIP and SHIP2, have been associated with cell migration in glioblastoma; however, the precise role these enzymes play in the process-and whether they work in concert-remains unclear. Here, we compared phosphoinositide 5-phosphatases expression in glioblastoma primary cells and cell lines and showed that SHIP2 and SKIP expression greatly varies between different cell types, while OCRL, another phosphoinositide 5-phosphatase, is constitutively expressed. Upon adhesion of U-251 MG cells to fibronectin, SHIP2, SKIP, and PI(4,5)P2 colocalized in membrane ruffles. Upregulation of PI(4,5)P2 was observed in SKIP-depleted U-251 MG cells compared to control cells, but only when cells were adhered to fibronectin. Both PTEN-deficient (U-251) and PTEN-containing (LN229) glioblastoma cells showed a decrease in cell migration velocity in response to SKIP downregulation. Moreover, a SHIP2 catalytic inhibitor lowered cell migration velocity in the U-251 MG cell line. We conclude that integrin activation in U-251 cells leads to colocalization of both SKIP and SHIP2 in ruffles, where they act as potential drivers of cell migration. Depending on their expression levels in glioblastoma, phosphoinositide 5-phosphatases could cooperate and synergize in the regulation of cell migration and adhesion.

Understanding and exploiting cell signalling convergence nodes and pathway cross-talk in malignant brain cancer

In cancer, complex intracellular and intercellular signals constantly evolve for the advantage of the tumour cells but to the disadvantage of the whole organism. Decades of intensive research have revealed the critical roles of cellular signalling pathways in regulating complex cell behaviours which influence tumour development, growth and therapeutic response, and ultimately patient outcome. Most studies have focussed on specific pathways and the resulting tumour cell function in a rather linear fashion, partly due to the available methodologies and partly due to the traditionally reductionist approach to research. Advances in cancer research, including genomic technologies have led to a deep appreciation of the complex signals and pathway interactions operating in tumour cells. In this review we examine the role and interaction of three major cell signalling pathways, PI3K, MAPK and cAMP, in regulating tumour cell functions and discuss the prospects for exploiting this knowledge to better treat difficult to treat cancers, using glioblastoma, the most common and deadly malignant brain cancer, as the example disease.

Buparlisib is a brain penetrable pan-PI3K inhibitor

Characterization of the genomic landscapes of intracranial tumours has revealed a clear role for the PI3K-AKT-mTOR pathway in tumorigenesis and tumour maintenance of these malignancies, making phosphatidylinositol 3-kinase (PI3K) inhibition a promising therapeutic strategy for these tumours. Buparlisib is a novel pan-PI3K inhibitor that is currently in clinical development for various cancers, including primary and secondary brain tumours. Importantly however, earlier studies have revealed that sufficient brain penetration is a prerequisite for antitumor efficacy against intracranial tumours. We therefore investigated the brain penetration of buparlisib using a comprehensive set of in vitro and in vivo mouse models. We demonstrate that buparlisib has an excellent brain penetration that is unaffected by efflux transporters at the blood-brain barrier, complete oral bioavailability and efficient intracranial target inhibition at clinically achievable plasma concentrations. Together, these characteristics make buparlisib the ideal candidate for intracranially-targeted therapeutic strategies that involve PI3K inhibition.

PIK3CA missense mutations promote glioblastoma pathogenesis, but do not enhance targeted PI3K inhibition

Background

Glioblastoma (GBM) is the most common adult primary brain tumor. Multimodal treatment is empiric and prognosis remains poor. Recurrent PIK3CA missense mutations (PIK3CA^mut) in GBM are restricted to three functional domains: adaptor binding (ABD), helical, and kinase. Defining how these mutations influence gliomagenesis and response to kinase inhibitors may aid in the clinical development of novel targeted therapies in biomarker-stratified patients.

Methods

We used normal human astrocytes immortalized via expression of hTERT, E6, and E7 (NHA). We selected two PIK3CA^mut from each of 3 mutated domains and induced their expression in NHA with (NHA^RAS) and without mutant RAS using lentiviral vectors. We then examined the role of PIK3CA^mut in gliomagenesis in vitro and in mice, as well as response to targeted PI3K (PI3Ki) and MEK (MEKi) inhibitors in vitro.

Results

PIK3CA^mut, particularly helical and kinase domain mutations, potentiated proximal PI3K signaling and migration of NHA and NHA^RASin vitro. Only kinase domain mutations promoted NHA colony formation, but both helical and kinase domain mutations promoted NHA^RAS tumorigenesis in vivo. PIK3CA^mut status had minimal effects on PI3Ki and MEKi efficacy. However, PI3Ki/MEKi synergism was pronounced in NHA and NHA^RAS harboring ABD or helical mutations.

Conclusion

PIK3CA^mut promoted differential gliomagenesis based on the mutated domain. While PIK3CA^mut did not influence sensitivity to single agent PI3Ki, they did alter PI3Ki/MEKi synergism. Taken together, our results demonstrate that a subset of PIK3CA^mut promote tumorigenesis and suggest that patients with helical domain mutations may be most sensitive to dual PI3Ki/MEKi treatment.

Inhibitory effect of NVP-BKM120 on cholangiocarcinoma cell growth

Abnormal activation of the phosphatidylinositol 3-kinase (PI3K) pathway has been demonstrated in certain types of cancer, including cholangiocarcinoma (CCA). This pathway may therefore be a promising target for CCA treatment. The present study assessed the inhibitory effect of NVP-BKM120, a pan-class I PI3K inhibitor, on CCA cell growth. This inhibitory effect was determined using CCA cell lines and in CCA-inoculated mice. The result from sulforhodamine B (SRB) assay demonstrated that NVP-BKM120 treatment inhibited CCA cell growth in a dose-dependent manner, even at the lowest tested concentration. The in vivo study revealed that oral administration of NVP-BKM120 (10 or 30 mg/kg) to CCA-inoculated nude mice led to a reduction in tumor growth when compared with controls, which was indicated by an immunohistochemical assay for Ki67 expression. In addition, the result from TUNEL assay demonstrated that NVP-BKM120 induced cancer cell death without any signs of toxicity, which indicated by the body weight of mice (data not shown). Western blot analysis demonstrated that NVP-BKM120 inhibited CCA cell growth by suppressing RAC serine/threonine protein kinase/mechanistic target of rapamycin activation and inhibiting the phosphorylation of phosphatase and tensin homolog, which is the inactivation form of the negative regulator of this pathway. Therefore, the results of the present study indicated that NVP-BKM120 should be considered as a therapeutic agent against CCA that could be used to improve treatment.

Pd/PTABS: Catalyst for Room Temperature Amination of Heteroarenes

A mild and highly efficient catalytic amination procedure for chloroheteroarenes at ambient temperature using the Pd/PTABS catalytic system is reported. The protocol is selective for the amination of chloroheteroarenes using secondary amines such as piperidine, pyrrolidine, and several others. The exceptional mildness of the developed protocol is beneficial for the synthesis of a crucial Buparlisib intermediate as well as the formal synthesis of Alogliptin in competitive yields.

Anticancer activity of osmium(VI) nitrido complexes in patient-derived glioblastoma initiating cells and in vivo mouse models

Glioblastoma is the most prevalent and lethal primary intrinsic brain tumor with a median patient survival of less than two years, even with the optimal standard of care, namely, surgical resection followed by radiotherapy with adjuvant temozolomide chemotherapy. Long-term survival is extremely rare and there is a tremendous need for novel GBM therapies. Following our prior reports on the anticancer activity of osmium(VI) nitrido compounds and their effectiveness against cancer initiating cells, we investigated the efficacy of Os(VI) on GBM initiating cells in vitro and in vivo. Conventional MTT and 3D cytotoxicity assays revealed that patient-derived GBM models were sensitive to cisplatin, TMZ, and two Os(IV) derivatives. Rapid cell death occurred at low micromolar concentrations of the Os(IV) compounds. Cell cycle analysis, Os uptake studies, and cellular distribution experiments provided further insight into the anticancer properties of these compounds, indicating differential uptake for both compounds and a modest G₂/M arrest after treatment. Moreover, in vivo experiments showed a significant increase in survival after a single intracranial chemotherapeutic injection, results that warrant further studies using this approach.

NVP-BKM120 inhibits colon cancer growth via FoxO3a-dependent PUMA induction

NVP-BKM120, a potent and highly selective PI3K inhibitor, is currently being investigated in phase I/II clinical trials. The mechanisms of action of NVP-BKM120 in colon cancer cells are unclear. In the present study, we investigated how NVP-BKM120 suppresses colon cancer cells growth and potentiates effects of other chemotherapeutic drugs. We found that NVP-BKM120 treatment enhance PUMA induction irrespective of p53 status through the FoxO3a pathway following AKT inhibition. Furthermore, PUMA is required for NVP-BKM120-induced apoptosis in colon cancer cells. In addition, NVP-BKM120 also synergized with 5-Fluorouracil or regorafenib to induce marked apoptosis via PUMA induction. Deficiency of PUMA suppressed apoptosis and antitumor effect of NVP-BKM120 in xenograft model. These results demonstrate a key role of PUMA in mediating the anticancer effects of NVP-BKM120 and suggest that PUMA could be used as an indicator of NVP-BKM120 sensitivity, and also have important implications for it clinical applications.

Duvelisib: a phosphoinositide-3 kinase δ/γ inhibitor for chronic lymphocytic leukemia

INTRODUCTION

Frontline chemotherapy is successful against chronic lymphocytic leukemia (CLL), but results in untoward toxicity. Further, prognostic factors, cytogenetic anomalies, and compensatory cellular signaling lead to therapy resistance or disease relapse. Therefore, for the past few years, development of targeted therapies is on the rise. PI3K is a major player in the B-cell receptor (BCR) signaling axis, which is critical for the survival and maintenance of B cells. Duvelisib, a PI3K δ/γ dual isoform specific inhibitor that induces apoptosis and reduces cytokine and chemokine levels in vitro, holds promise for CLL. Areas covered: Herein, we review PI3K isoforms and their inhibitors in general, and duvelisib in particular; examine literature on preclinical investigations, pharmacokinetics and clinical studies of duvelisib either as single agent or in combination, for patients with CLL and other lymphoid malignancies. Expert opinion: Duvelisib targets the PI3K δ isoform, which is necessary for cell proliferation and survival, and γ isoform, which is critical for cytokine signaling and pro-inflammatory responses from the microenvironment. In phase I clinical trials, duvelisib as a single agent showed promise for CLL and other lymphoid malignancies. Phase II and III trials of duvelisib alone or in combination with other agents are ongoing.

PI3K Pathway Inhibition Achieves Potent Antitumor Activity in Melanoma Brain Metastases In Vitro and In Vivo

PURPOSE

Great advances have recently been made in treating patients with metastatic melanoma. However, existing therapies are less effective on cerebral than extracerebral metastases. This highlights the potential role of the brain environment on tumor progression and drug resistance and underlines the need for "brain-specific" therapies. We previously showed that the PI3K-AKT survival pathway is hyperactivated in brain but not extracerebral melanoma metastases and that astrocyte-conditioned medium activates AKT in melanoma cells in vitro We therefore tested the PI3K inhibitor buparlisib as an antitumor agent for melanoma brain metastases.

EXPERIMENTAL DESIGN AND RESULTS

Buparlisib inhibited AKT activity, decreased proliferation, and induced apoptosis in metastatic melanoma cell lines and short-term brain melanoma cells, irrespective of their BRAF and NRAS mutation status. In addition, buparlisib inhibited hyperactivated AKT and induced apoptosis in melanoma cells that were stimulated with astrocyte-conditioned medium. The growth of tumors induced by injecting human BRAF- and NRAS-mutant metastatic melanoma cells into the brain of mice was significantly inhibited by buparlisib.

CONCLUSIONS

These results emphasize the value of targeting the PI3K pathway as a strategy to develop drugs for melanoma brain metastases. Clin Cancer Res; 22(23); 5818-28. ©2016 AACR.