Selective PI3K inhibition by BKM120 and BEZ235 alone or in combination with chemotherapy in wild-type and mutated human gastrointestinal cancer cell lines

Unlocking the Potential: Epstein-Barr Virus (EBV) in Gastric Cancer and Future Treatment Prospects, a Literature Review

Gastric cancer (GC) is a complex disease with various etiologies. While Helicobacter pylori infection is still one of the leading risk factors for GC, increasing evidence suggests a link between GC and other infective agents such as Epstein Bar Virus (EBV). EBV-associated gastric cancer (EBVaGC) is now recognized as a distinct subgroup of GC, and the complex interactions between the virus and gastric mucosa may influence its development. A recent integrative analysis of the genome and proteome of GC tissues by The Cancer Genome Atlas project has identified EBVaGC as a specific subtype characterized by PIK3CA and ARID1A mutations, extensive DNA hyper-methylation, and activation of immune signaling pathways. These molecular characteristics are markers of the unique molecular profile of this subset of GC and are potential targets for therapy. This review aims to provide an overview of the current knowledge on EBVaGC. It will focus on the epidemiology, clinic-pathological features, and genetic characteristics of EBVaGC. Additionally, it will discuss recent data indicating the potential use of EBV infection as a predictive biomarker of response to chemotherapy and immune checkpoint inhibitors. The review also delves into potential therapeutic approaches for EBVaGC, including targeted therapies and adoptive immunotherapy, highlighting the promising potential of EBV as a therapeutic target.

The essential roles of lncRNAs/PI3K/AKT axis in gastrointestinal tumors

The role of long noncoding RNA (lncRNA) in tumors, particularly in gastrointestinal tumors, has gained significant attention. Accumulating evidence underscores the interaction between various lncRNAs and diverse molecular pathways involved in cancer progression. One such pivotal pathway is the PI3K/AKT pathway, which serves as a crucial intracellular mechanism maintaining the balance among various cellular physiological processes for normal cell growth and survival. Frequent dysregulation of the PI3K/AKT pathway in cancer, along with aberrant activation, plays a critical role in driving tumorigenesis. LncRNAs modulate the PI3K/AKT signaling pathway through diverse mechanisms, primarily by acting as competing endogenous RNA to regulate miRNA expression and associated genes. This interaction significantly influences fundamental biological behaviors such as cell proliferation, metastasis, and drug resistance. Abnormal expression of numerous lncRNAs in gastrointestinal tumors often correlates with clinical outcomes and pathological features in patients with cancer. Additionally, these lncRNAs influence the sensitivity of tumor cells to chemotherapy in multiple types of gastrointestinal tumors through the abnormal activation of the PI3K/AKT pathway. These findings provide valuable insights into the mechanisms underlying gastrointestinal tumors and potential therapeutic targets. However, gastrointestinal tumors remain a significant global health concern, with increasing incidence and mortality rates of gastrointestinal tumors over recent decades. This review provides a comprehensive summary of the latest research on the interactions of lncRNA and the PI3K/AKT pathway in gastrointestinal tumor development. Additionally, it focuses on the functions of lncRNAs and the PI3K/AKT pathway in carcinogenesis, exploring expression profiles, clinicopathological characteristics, interaction mechanisms with the PI3K/AKT pathway, and potential clinical applications.

Inhibition of PI3K/AKT signaling using BKM120 reduced the proliferation and migration potentials of colorectal cancer cells and enhanced cisplatin-induced cytotoxicity

BACKGROUND

Although extensive efforts have been made to improve the treatment of colorectal cancer (CRC) patients, the prognosis for these patients remains poor. A wide range of anti-cancer agents has been applied to ameliorate the clinical management of CRC patients; however, drug resistance develops in nearly all patients. Based on the prominent role of PI3K/AKT signaling in the development of CRC and current interest in the application of PI3K inhibitors, we aimed to disclose the exact mechanism underlying the efficacy of BKM120, a well-known pan-class I PI3K inhibitor, in CRC-derived SW480 cells.

MATERIALS AND METHODS

The effects of BKM120 on SW480 cells were studied using MTT assay, cell cycle assay, Annexin V/PI apoptosis tests, and scratch assay. In the next step, qRT-PCR was used to investigate the underlying molecular mechanisms by which the PI3K inhibitor could suppress the survival of SW480 cells.

RESULT

The results of the MTT assay showed that BKM120 could decrease the metabolic activity of SW480 cells in a concentration and time-dependent manner. Investigating the exact mechanism of BKM120 showed that this PI3K inhibitor induces its anti-survival effects through a G2/M cell cycle arrest and apoptosis-mediated cell death. Moreover, the scratch assay demonstrated that PI3K inhibition led to the inhibition of cancer invasion and inhibition of PI3K/AKT signaling remarkably sensitized SW480 cells to Cisplatin.

CONCLUSION

Based on our results, inhibition of PI3K/AKT signaling can be a promising approach, either as a single modality or in combination with Cisplatin. However, further clinical studies should be performed to improve our understanding.

Role of AT-rich interaction domain 1A in gastric cancer immunotherapy: Preclinical and clinical perspectives

The application of immune checkpoint inhibitor (ICI) using monoclonal antibodies has brought about a profound transformation in the clinical outcomes for patients grappling with advanced gastric cancer (GC). Nonetheless, despite these achievements, the quest for effective functional biomarkers for ICI therapy remains constrained. Recent research endeavours have shed light on the critical involvement of modified epigenetic regulators in the pathogenesis of gastric tumorigenesis, thus providing a glimpse into potential biomarkers. Among these regulatory factors, AT-rich interaction domain 1A (ARID1A), a pivotal constituent of the switch/sucrose non-fermentable (SWI/SNF) complex, has emerged as a promising candidate. Investigations have unveiled the pivotal role of ARID1A in bridging the gap between genome instability and the reconfiguration of the tumour immune microenvironment, culminating in an enhanced response to ICI within the landscape of gastric cancer treatment. This all-encompassing review aims to dissect the potential of ARID1A as a valuable biomarker for immunotherapeutic approaches in gastric cancer, drawing from insights garnered from both preclinical experimentation and clinical observations.

The effects of ARID1A mutation in gastric cancer and its significance for treatment

Gastric cancer (GC) has emerged as a significant issue in public health all worldwide as a result of its high mortality rate and dismal prognosis. AT-rich interactive domain 1 A (ARID1A) is a vital component of the switch/sucrose-non-fermentable (SWI/SNF) chromatin remodeling complex, and ARID1A mutations occur in various tumors, leading to protein loss and decreased expression; it then affects the tumor biological behavior or prognosis. More significantly, ARID1A mutations will likely be biological markers for immune checkpoint blockade (ICB) treatment and selective targeted therapy. To provide theoretical support for future research on the stratification of individuals with gastric cancer with ARID1A as a biomarker to achieve precision therapy, we have focused on the clinical significance, predictive value, underlying mechanisms, and possible treatment strategies for ARID1A mutations in gastric cancer in this review.

CBF-Beta Mitigates PI3K-Alpha-Specific Inhibitor Killing through PIM1 in PIK3CA-Mutant Gastric Cancer

PIK3CA is the second most mutated gene in cancer leading to aberrant PI3K/AKT/mTOR signaling and increased translation, proliferation, and survival. Some 4%-25% of gastric cancers display activating PIK3CA mutations, including 80% of Epstein-Barr virus-associated GCs. Small molecules, including pan-PI3K and dual PI3K/mTOR inhibitors, have shown moderate success clinically, due to broad on-target/off-tissue effects. Thus, isoform-specific and mutant selective inhibitors have been of significant interest. However, drug resistance is a problem and has affected success of new drugs. There has been a concerted effort to define mechanisms of resistance and identify potent combinations in many tumor types, though gastric cancer is comparatively understudied. In this study, we identified modulators of the response to the PI3Kα-specific inhibitor, BYL719, in PIK3CA-mutant GCs. We found that loss of NEDD9 or inhibition of BCL-XL conferred hypersensitivity to BYL719, through increased cell-cycle arrest and cell death, respectively. In addition, we discovered that loss of CBFB conferred resistance to BYL719. CBFB loss led to upregulation of the protein kinase PIM1, which can phosphorylate and activate several overlapping downstream substrates as AKT thereby maintaining pathway activity in the presence of PI3Kα inhibition. The addition of a pan-PIM inhibitor re-sensitized resistant cells to BYL719. Our data provide clear mechanistic insights into PI3Kα inhibitor response in PIK3CA-mutant gastric tumors and can inform future work as mutant-selective inhibitors are in development for diverse tumor types.

IMPLICATIONS

Loss of either NEDD9 or BCL-XL confers hypersensitivity to PI3K-alpha inhibition whereas loss of CBFB confers resistance through a CBFB/PIM1 signaling axis.

Upregulation of PIK3IP1 monitors the anti-cancer activity of PI3Kα inhibitors in gastric cancer cells

Gastric cancer remains one of the most malignant cancers in the world. The target-based drugs approved by FDA for gastric cancer treatment include only three targets and benefit a small portion of gastric cancer patients. PIK3CA, a confirmed oncogene, mutates in 7-25% gastric cancer patients. PI3Kα inhibitor BYL719 has been approved for treating specific breast cancer. However, there is no comprehensive study about PI3Kα inhibitor in gastric cancer. In this study, we found pharmacological inhibition or knockdown of PI3Kα effectively inhibited the proliferation of partial gastric cancer cells. Then, we systematically explored the potential biomarkers for predicting or monitoring treatment response according to previous reports and found that basal expression of several receptor tyrosine kinases were related with the sensitivity of gastric cancer cells to BYL719. Next, RNA-seq technique was utilized and showed that BYL719 inhibited Myc targets V2 gene set in sensitive gastric cancer cells, and western blotting further verified that c-Myc was only inhibited in sensitive gastric cancer cells. More importantly, we firstly found BYL719 significantly elevated the expression of PIK3IP1 in sensitive gastric cancer cells, which was also observed in NCI-N87 cell derived xenograft mice models. Meanwhile, knockdown of PIK3IP1 partially rescued the cell growth inhibited by BYL719 in sensitive gastric cancer cells, suggesting the important role of PIK3IP1 in the antitumor activity of BYL719. In conclusion, our study provides biological evidence that PI3Kα is a promising target in specific gastric cancer and the elevation of PIK3IP1 could supply as a biomarker that monitoring treatment response.

Discovery of Synergistic Drug Combinations for Colorectal Cancer Driven by Tumor Barcode Derived from Metabolomics “Big Data”

The accumulation of cancer metabolomics data in the past decade provides exceptional opportunities for deeper investigations into cancer metabolism. However, integrating a large amount of heterogeneous metabolomics data to draw a full picture of the metabolic reprogramming and to discover oncometabolites of certain cancers remains challenging. In this study, a tumor barcode constructed based upon existing metabolomics “big data” using the Bayesian vote-counting method is proposed to identify oncometabolites in colorectal cancer (CRC). Specifically, a panel of oncometabolites of CRC was generated from 39 clinical studies with 3202 blood samples (1332 CRC vs. 1870 controls) and 990 tissue samples (495 CRC vs. 495 controls). Next, an oncometabolite-protein network was constructed by combining the tumor barcode and its involved proteins/enzymes. The effect of anti-cancer drugs or drug combinations was then mapped into this network by the random walk with restart process. Utilizing this network, potential Irinotecan (CPT-11)-sensitizing agents for CRC treatment were discovered by random forest and Xgboost. Finally, a compound named MK-2206 was highlighted and its synergy with CPT-11 was validated on two CRC cell lines. To summarize, we demonstrate in the present study that the metabolomics “big data”-based tumor barcodes and the subsequent network analyses are potentially useful for drug combination discovery or drug repositioning.

The Superior Cytotoxicity of Dual Targeting of BCR/ABL and PI3K in K562 Cells: Proposing a Novel Therapeutic Potential for the Treatment of CML

Apart from BCR/ABL which is the main player in the pathogenesis of chronic myeloid leukemia (CML), the role of other signaling cascades should not be underestimated especially for the maintenance of leukemic cells survival. The results of the present study indicate that either an isoform-specific or a pan-PI3K inhibitor could potently reduce the survival of CML-derived K562 cells, shedding more light on the involvement of the PI3K axis in the pathogenesis of CML. Of particular interest, the importance of the PI3K pathway in this disease became more evident when we found that there was a more remarkable reduction in the viability of K562 cells when BKM120 was used in combination with imatinib. Moreover, BKM120 robustly enhanced the growth-suppressive effect of imatinib through p21-mediated induction of G2/M cell cycle arrest and induction of apoptotic cell death. Despite the favorable anti-survival effects of the drug combination, these agents failed to induce inhibitory effects on the expression of c-Myc and NF-κB anti-apoptotic target genes. However, the ability of combinational therapy in diminishing K562 cell survival was potentiated either in the presence of 10058-F4 (c-Myc inhibitor) or Bortezomib (proteasome inhibitor), suggestive of the role of both NF-κB and c-Myc in overshadowing the therapeutic value of drugs combination. Taken together, the results of this study showed that inhibition of the PI3K pathway is a suitable approach to enhance the therapeutic value of imatinib in the treatment of CML.

AP-2α Regulates S-Phase and Is a Marker for Sensitivity to PI3K Inhibitor Buparlisib in Colon Cancer

Activating protein 2 alpha (AP-2α; encoded by TFAP2A) functions as a tumor suppressor and influences response to therapy in several cancer types. We aimed to characterize regulation of the transcriptome by AP-2α in colon cancer. CRISPR-Cas9 and short hairpin RNA were used to eliminate TFAP2A expression in HCT116 and a panel of colon cancer cell lines. AP-2α target genes were identified with RNA sequencing and chromatin immunoprecipitation sequencing. Effects on cell cycle were characterized in cells synchronized with aphidicolin and analyzed by FACS and Premo FUCCI. Effects on invasion and tumorigenesis were determined by invasion assay, growth of xenografts, and phosphorylated histone H3 (PHH3). Knockout of TFAP2A induced significant alterations in the transcriptome including repression of TGM2, identified as a primary gene target of AP-2α. Loss of AP-2α delayed progression through S-phase into G₂-M and decreased phosphorylation of AKT, effects that were mediated through regulation of TGM2. Buparlisib (BKM120) repressed in vitro invasiveness of HCT116 and a panel of colon cancer cell lines; however, loss of AP-2α induced resistance to buparlisib. Similarly, buparlisib repressed PHH3 and growth of tumor xenografts and increased overall survival of tumor-bearing mice, whereas, loss of AP-2α induced resistance to the effect of PI3K inhibition. Loss of AP-2α in colon cancer leads to prolonged S-phase through altered activation of AKT leading to resistance to the PI3K inhibitor, Buparlisib. The findings demonstrate an important role for AP-2α in regulating progression through the cell cycle and indicates that AP-2α is a marker for response to PI3K inhibitors. IMPLICATIONS: AP-2α regulated cell cycle through the PI3K cascade and activation of AKT mediated through TGM2. AP-2α induced sensitivity to Buparlisib/BKM120, indicating that AP-2α is a biomarker predictive of response to PI3K inhibitors.

The PI3K/Akt/mTOR signaling pathway in gastric cancer; from oncogenic variations to the possibilities for pharmacologic interventions

Genetic and epigenetic alterations have been under concentrated investigations for many years in order to unearth the molecules regulating human cancer pathogenesis. However, the identification of a wide range of dysregulated genes and their protein products has raised a question regarding how the results of this large collection of alterations could converge into a formation of one malignancy. The answer may be found in the signaling cascades that regulate the survival and metabolism of the cells. Aberrancies of each participant molecule of such cascades may well result in augmented viability and unlimited proliferation of cancer cells. Among various signaling pathways, the phosphatidylinositol-3-kinase (PI3K) axis has been shown to be activated in about one-third of human cancers. One of the malignancies that is mostly affected by this axis is gastric cancer (GC), one of the most fatal cancers worldwide. In the present review, we aimed to illustrate the significance of the PI3K/Akt/mTOR axis in the pathogenesis of GC and also provided a wide perspective about the application of the inhibitors of this axis in the therapeutic strategies of this malignancy.

The influence of PI3K inhibition on the radiotherapy response of head and neck cancer cells

Radiotherapy has a central role in the treatment of head and neck squamous cell carcinoma (HNSCC). Activation of the PI3K/AKT/mTOR pathway can decrease the efficiency of radiotherapy via the promotion of cell survival and DNA repair. Here, the influence of PI3K pathway inhibition on radiotherapy response was investigated. Two PI3K inhibitors were investigated and both BKM120 and GDC0980 effectively inhibited cellular and clonogenic growth in 6 HNSCC cells, both HPV-positive as well as HPV-negative. Despite targeted inhibition of the pathway and slight increase in DNA damage, PI3K inhibition did not show significant radiosensitization. Currently only one clinical trial is assessing the effectiveness of combining BKM120 with RT in HNSCC (NCT02113878) of which the results are eagerly awaited.

Orthotopic Patient-Derived Xenografts of Gastric Cancer to Decipher Drugs Effects on Cancer Stem Cells and Metastatic Dissemination

Gastric cancer is the third leading cause of cancer mortality worldwide. Cancer stem cells (CSC) are at the origin of tumor initiation, chemoresistance, and the formation of metastases. However, there is a lack of mouse models enabling the study of the metastatic process in gastric adenocarcinoma (GC). The aims of this study were to develop original mouse models of patient-derived primary GC orthotopic xenografts (PDOX) allowing the development of distant metastases as preclinical models to study the anti-metastatic efficiency of drugs such as the phosphatidylinositol 3-kinase (PI3K) inhibitor Buparlisib (BKM120). Luciferase-encoding cells generated from primary GC were injected into the stomach wall of immunocompromised mice; gastric tumor and metastases development were followed by bioluminescence imaging. The anti-CSC properties of BKM120 were evaluated on the GC cells’ phenotype (CD44 expression) and tumorigenic properties in vitro and in vivo on BKM120-treated mice. After eight weeks, PDOX mice formed tumors in the stomach as well as distant metastases, that were enriched in CSC, in the liver, the lung, and the peritoneal cavity. BKM120 treatment significantly inhibited the CSC properties in vitro and reduced the number of distant metastases in mice. These new preclinical models offer the opportunity to study the anti-metastatic efficiency of new CSC-based therapeutic strategies.

Therapeutic Potency of PI3K Pharmacological Inhibitors of Gastrointestinal Cancer

Therapeutic targeting of phosphatidyl-inositol 3-kinase (PI3K) is considered as a possible strategy in several types of cancer, including gastrointestinal ones. In vitro and in vivo studies indicated the significance of proapoptotic and antiproliferative inhibition of PI3K. Although there are many phase 1 and 2 clinical trials on PI3K inhibitors in patients with gastrointestinal cancer, the molecular mechanism of PI3K targeting PI3K/ mTOR pathway is not clear. Panclass I, isoformselective, and dual PI3K/mTOR inhibitors are under investigation. This review aimed to indicate PI3K-dependent targeting mechanisms in gastrointestinal cancer and the evaluation of related clinical data.

PTRF suppresses the progression of colorectal cancers

As a key component of caveolae structure on the plasma membrane, accumulated evidence has suggested that Polymerase I and Transcript Release Factor (PTRF) plays a pivotal role in suppressing the progression of human malignances. However, the function of PTRF in the development of colorectal cancers is still unclear. Here we report that the expression of PTRF is significantly reduced in tumor tissues derived from human patients with colorectal cancers, and that the downregulation of PTRF correlates to the advanced stage of the disease. In addition, we found that the expression of PTRF negatively regulates the tumorigenic activities of colorectal cell lines (Colo320, HT29 and CaCo2). Furthermore, ectopic PTRF expression caused significant suppression of cellular proliferation, and anchorage-independent colony growth of Colo320 cells, which have the lowest expression level of PTRF in the three studied cell lines. Meanwhile, shRNA mediated knockdown of PTRF in CaCo2 cells significantly promoted cellular proliferation and anchorage-independent colony growth. In addition, in vivo assays further revealed that tumor growth was significantly inhibited in xenografts with ectopic PTRF expression as compared to untreated Colo320 cells, but was markedly enhanced in PTRF knockdown CaCo2 cells. Biochemical studies revealed that overexpression of PTRF led to the suppression of the AKT/mTOR pathway, as evidenced by reduced phosphorylation of AKT, mTOR, and downstream MMP-9. Thus, these findings, for the first time, demonstrated that PTRF inhibits the tumorigenesis of colorectal cancers and that it might serve as a potential therapeutic target for human colon cancer patients.

Novel Targeted Therapies for Esophagogastric Cancer

Gastroesophageal cancer (GEC) remains a major cause of cancer-related mortality worldwide. Although the incidence of distal gastric adenocarcinoma (GC) is declining in the United States, proximal esophagogastric junction adenocarcinoma (EGJ) is increasing in incidence. GEC, including GC and EGJ, is treated uniformly in the metastatic setting. Overall survival in the metastatic setting remains poor. Molecular characterization of GEC has identified mutations and copy number variations, along with other oncogenes, biomarkers, and immuno-oncologic checkpoints that may serve as actionable therapeutic targets. This article reviews these key aberrations, their impact on protein expression, therapeutic implications, and clinical directions within each pathway.

Inhibition of phosphatidylinositide 3-kinase ameliorates antiproliferation by benzyl isothiocyanate in human colon cancer cells

In the present study, we clarified the role of phosphatidylinositide 3-kinase (PI3K) in antiproliferation induced by benzyl isothiocyanate (BITC) in human colorectal cancer cells. BITC simultaneously activated the PI3K/Akt/forkhead box O (FoxO) pathway, whereas it significantly inhibited the proliferation in human colorectal cancer cells. Inhibitory experiments using a PI3K selective inhibitor, LY294002 or NVP-BEZ235, significantly enhanced the BITC-induced antiproliferation and apoptotic cell population with the attenuation of the BITC-induced activation of the PI3K/Akt/FoxO survival pathway. Furthermore, BITC enhanced the insulin-activated PI3K/Akt/FoxO pathway, possibly through its inhibition of the protein tyrosine phosphatase 1B enzymatic activity. Taken together, these results suggested that the PI3K/Akt/FoxO pathway negatively regulates the BITC-induced antiproliferation in human colorectal cancer cells.

PIK3CA mutations are associated with increased tumor aggressiveness and Akt activation in gastric cancer

PIK3CA mutations are frequent in gastric cancer. However, their pathological and clinical implications are still unclear. We analyzed the clinicopathological characteristics according to the PIK3CA mutation status of patients with stage IB–IV disease who underwent gastrectomy between May 2003 and Dec. 2005 (cohort 1; n = 302) and of those with stage IV disease who received gastrectomy between Jul. 2006 and Dec. 2012 (cohort 2; n = 120). PIK3CA mutations were detected in 40 patients (13.2%) in cohort 1. In these patients, PIK3CA-mutant tumors were more frequently located in the upper third of the stomach (p = 0.021) and significantly showed poorly differentiated histology (p = 0.018) and increased lymphatic (p = 0.015), vascular (p = 0.005), and perineural invasion (p = 0.026). In addition, these tumors showed significantly increased lymphocyte and neutrophil infiltration in cancer stroma (p < 0.001), Epstein–Barr virus positivity (p < 0.001), and microsatellite instability (p = 0.015). Cytoplasmic Akt expression was significantly increased in these tumors (p = 0.001). In cohort 2, PIK3CA mutations were identified in 15 patients (12.5%). PIK3CA-mutant tumors showed significantly increased vascular invasion (p = 0.019) and microsatellite instability (p = 0.041). In addition, cytoplasmic Akt expression was also significantly increased (p = 0.018). However, in both cohorts, PIK3CA mutations were not associated with the prognosis of patients. In conclusion, PIK3CA mutations were associated with increased tumor aggressiveness, especially in locoregional disease, and Akt activation in gastric cancer. Our data suggest that PIK3CA-mutated gastric cancer is a distinct disease entity, which might need a different therapeutic approach.

Overexpression of ATP-Binding Cassette Subfamily G Member 2 Confers Resistance to Phosphatidylinositol 3-Kinase Inhibitor PF-4989216 in Cancer Cells

Deregulated activation of phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is frequently found in human cancers, which plays a key role in promoting cancer proliferation and resistance to anticancer therapies. Therefore, developing inhibitors targeting key components of the PI3K/Akt/mTOR signaling pathway has great clinical significance. PF-4989216 is a novel, orally available small-molecule drug that was developed to selectively inhibit the PI3K/Akt/mTOR signaling pathway and subsequent cancer cell proliferation. PF-4989216 exhibited potent and selective inhibition against PI3K kinase activity in preclinical small-cell lung cancer (SCLC) models, and was especially effective against the proliferation of SCLCs harboring PIK3CA mutation. Unfortunately, in addition to innate resistance mechanisms, drug extrusion by the efflux pumps may also contribute to the development of acquired resistance to PI3K inhibitors in cancer cells. The overexpression of ATP-binding cassette (ABC) drug transporters ABCB1 and ABCG2 is one of the most common mechanisms for reducing intracellular drug concentration and developing multidrug resistance, which remains a substantial challenge to the effective treatment of cancer. In this study, we report the discovery of ABCG2 overexpression as a mechanism of resistance to PI3K inhibitor PF-4989216 in human cancer cells. We demonstrated that the inhibition of Akt and downstream S6RP phosphorylation by PF-4989216 were significantly reduced in ABCG2-overexpressing human cancer cells. Moreover, overexpression of ABCG2 in various cancer cell lines confers significant resistance to PF-4989216, which can be reversed by an inhibitor or competitive substrate of ABCG2, indicating that ABCG2-mediated transport alone can sufficiently reduce the intracellular concentration of PF-4989216.

Deconvolution of Buparlisib's mechanism of action defines specific PI3K and tubulin inhibitors for therapeutic intervention

BKM120 (Buparlisib) is one of the most advanced phosphoinositide 3-kinase (PI3K) inhibitors for the treatment of cancer, but it interferes as an off-target effect with microtubule polymerization. Here, we developed two chemical derivatives that differ from BKM120 by only one atom. We show that these minute changes separate the dual activity of BKM120 into discrete PI3K and tubulin inhibitors. Analysis of the compounds cellular growth arrest phenotypes and microtubule dynamics suggest that the antiproliferative activity of BKM120 is mainly due to microtubule-dependent cytotoxicity rather than through inhibition of PI3K. Crystal structures of BKM120 and derivatives in complex with tubulin and PI3K provide insights into the selective mode of action of this class of drugs. Our results raise concerns over BKM120's generally accepted mode of action, and provide a unique mechanistic basis for next-generation PI3K inhibitors with improved safety profiles and flexibility for use in combination therapies.

Buparlisib/BKM120 is in phase 3 clinical trials as a phosphoinositide 3-kinase (PI3K) inhibitor. Here, Bohnacker et al. combine chemical biology and structural biology approaches to segregate BKM120's biological actions, and suggest that it causes mitotic arrest predominantly by binding microtubules and disrupting their dynamics.

In Vitro and In Vivo Synergistic Antitumor Activity of the Combination of BKM120 and Erlotinib in Head and Neck Cancer: Mechanism of Apoptosis and Resistance

We previously reported that the EGFR-targeted inhibitor erlotinib induces G₁ arrest of squamous cell carcinoma of the head and neck (SCCHN) cell lines without inducing significant apoptosis. Large-scale genomic studies suggest that >50% of SCCHN cases have activation of PI3K pathways. This study investigated whether cotargeting of EGFR and PI3K has synergistic antitumor effects and apoptosis induction. We examined growth suppression, apoptosis, and signaling pathway modulation resulting from single and combined targeting of EGFR and PI3K with erlotinib and BKM120, respectively, in a panel of SCCHN cell lines and a xenograft model of SCCHN. In a panel of 12 cell lines, single targeting of EGFR with erlotinib or PI3K with BKM120 suppressed cellular growth without inducing significant apoptosis. Cotargeting of EGFR and PI3K synergistically inhibited SCCHN cell line and xenograft tumor growth, but induced variable apoptosis; some lines were highly sensitive, others were resistant. Mechanistic studies revealed that the combination inhibited both axes of the mTORC1 (S6 and 4EBP1) pathway in apoptosis-sensitive cell lines along with translational inhibition of Bcl-2, Bcl-xL, and Mcl-1, but failed to inhibit p-4EBP1, Bcl-2, Bcl-xL, and Mcl-1 in an apoptosis-resistant cell line. siRNA-mediated knockdown of eIF4E inhibited Bcl-2 and Mcl-1 and sensitized this cell line to apoptosis. Our results strongly suggest that cotargeting of EGFR and PI3K is synergistic and induces apoptosis of SCCHN cell lines by inhibiting both axes of the AKT-mTOR pathway and translational regulation of antiapoptotic Bcl-2 proteins. These findings may guide the development of clinical trials using this combination of agents. Mol Cancer Ther; 16(4); 729-38. ©2017 AACR.

MK-2206 co-treatment with 5-fluorouracil or doxorubicin enhances chemosensitivity and apoptosis in gastric cancer by attenuation of Akt phosphorylation

The anticancer effect of MK-2206, an Akt inhibitor, has been explored in some types of cancers, but its effect on gastric cancer is unclear. In this study, we aimed to investigate its anticancer effect in gastric cancer cells. Cell viability and colony formation assays showed that MK-2206 effectively inhibited the proliferation of SGC-7901 and MKN45 cells. The 50% inhibitory concentration values after 24, 48, and 72 hours' treatment were 22.92, 13.68, and 8.55 μM in SGC-7901 cells and 19.21, 13.10, and 9.11 μM in MKN45 cells, respectively. Treatment with MK-2206 induced apoptosis in SGC-7901 cells as indicated by flow cytometry assay. The combination indexes of MK-2206 and doxorubicin were 0.59 in SGC-7901 cells and 0.57 in MKN45 cells, whereas for 5-fluorouracil (5-FU) the indexes were 0.17 in SGC-7901 cells and 0.73 in MKN45 cells, indicating that MK-2206 could work synergistically with doxorubicin or 5-FU to inhibit cell growth. Furthermore, a small dose (1 μM) of MK-2206 co-treatment with doxorubicin or 5-FU was sufficient for complete inhibition of chemotherapeutic alteration of phosphorylated Akt expression and significant enhancement of pro-apoptosis effect through the activation of caspase pathway. Therefore, MK-2206 effectively inhibits gastric cancer cell growth by attenuation of Akt phosphorylation and synergistically enhances the antitumor effect of doxorubicin and 5-FU via caspase-dependent apoptosis.

Synergistic inhibition of colon cancer cell growth with nanoemulsion-loaded paclitaxel and PI3K/mTOR dual inhibitor BEZ235 through apoptosis

Colon cancer is the third most common cancer in the world, with drug resistance and metastasis being the major challenges to effective treatments. To overcome this, combination therapy with different chemotherapeutics is a common practice. In this study, we demonstrated that paclitaxel (PTX) together with BEZ235 exhibited a synergetic inhibition effect on colon cancer cell growth. Furthermore, nanoemulsion (NE)-loaded PTX and BEZ235 were more effective than the free drug, and a combination treatment of both NE drugs increased the efficiency of the treatments. BEZ235 pretreatment before adding PTX sensitized the cancer cells further, suggesting a synergistic inhibition effect through the phosphatidylinositol-3-kinases/protein kinase B/mammalian target of rapamycin pathway. The 50% inhibitory concentrations for BEZ235 were 127.1 nM and 145.0 nM and for PTX 9.7 nM and 9.5 nM for HCT-116 and HT-29 cells, respectively. When loaded with NE the 50% inhibitory concentrations for BEZ235 decreased to 52.6 nM and 55.6 nM and for PTX to 1.9 nM and 2.3 nM for HCT-116 and HT-29 cells, respectively. Combination treatment with 10 nM NE-BEZ235 and 0.6 nM and 1.78 nM NE-PTX could kill 50% of HCT-116 and HT-29, respectively. The cell death caused by the treatment was through apoptotic cell death, which coincided with decreased expression of anti-apoptotic protein B-cell lymphoma 2. Our data indicate that the combination therapy of PTX with the phosphatidylinositol-3-kinases/protein kinase B/mammalian target of rapamycin dual inhibitor BEZ235 using NE delivery may hold promise for a more effective approach for colon cancer treatment.

Translating gastric cancer genomics into targeted therapies

Gastric cancer is a common disease with limited treatment options and a poor prognosis. Many gastric cancers harbour potentially actionable targets, including over-expression and mutations in tyrosine kinase pathways. Agents have been developed against these targets with varying success- in particular, the use of trastuzumab in HER2-overexpressing gastric cancers has resulted in overall survival benefits. Gastric cancers also have high levels of somatic mutations, making them candidates for immunotherapy; early work in this field has been promising. Recent advances in whole genome and multi-platform sequencing have driven the development of molecular classification systems, which may in turn guide the selection of patients for targeted treatment. Moving forward, challenges will include the development of appropriate biomarkers to predict responses to targeted therapy, and the application of new molecular classifications into trial development and clinical practice.

Targeted therapies in gastric cancer treatment: where we are and where we are going

Gastric cancer (GC) is one of the most common malignancies and a major cause of cancer-related deaths worldwide. Its incidence has significantly declined over the last few decades, probably due to the identification of specific etiologic agents such as Helicobacter pylori and other dietary and environmental risk factors. Nevertheless, most of the cases are unfortunately diagnosed at an advanced stage justifying median overall survival rates frequently not exceeding one year. Palliative combination chemotherapy usually represented by a platinum-based doublet is the mainstay of treatment in the metastatic setting. Adding a third drug such as an anthracycline or a taxane has been shown to improve response rate and provide limited survival benefits in fit selected patients. Unlike other tumors, the introduction of molecularly targeted drugs in the medical armamentarium for GC is relatively recent with trastuzumab and ultimately ramucirumab constituting the only agents approved to date. Recent advances in the understanding of GC biology have led to the development of novel targeted therapies holding the promise to further improve treatment outcomes. The aim of this paper is to review the main available data coming from clinical trials of targeted drugs and to describe some of the most interesting molecules in clinical development in GC. These include drugs targeting EGFR, angiogenesis, c-MET, FGFR2, mTOR and immune checkpoints.

Targeting the PI3K signaling pathway in KRAS mutant colon cancer

Metastatic colorectal cancer (CRC) patients with v‐Ki‐ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations are resistant to monoclonal antibody that targets the epidermal growth factor receptor such as cetuximab. BKM120 targets phosphatidylinositide‐3‐kinase (PIK3CA), but it is unknown whether BKM120 can reverse cetuximab resistance in KRAS mutant CRC. Human CRC cell lines with KRAS mutations (DLD‐1, HCT116, and LoVo) were used to test the effect of cetuximab, BKM120, and cetuximab plus BKM120 on cell proliferation in vitro and in vivo. BKM120 reduced cell proliferation in a concentration‐dependent manner in the LoVo (PI3KCA wild type) as well as the HCT116 and DLD1 cells (that carry a PI3KCA mutation). BKM120 only inhibited ERK phosphorylation in LoVo cells (PIK3CA wild type), but not in DLD1 or HCT116 cells at a concentration of 1 μmol/L. Treatment with cetuximab and BKM120 significantly reduced the growth of xenograft tumors originating from KRAS mutant cells compared with cetuximab alone (P = 0.034). BKM120 may overcome cetuximab resistance in colon cancer cells with KRAS mutation.

The pan-class I phosphatidyl-inositol-3 kinase inhibitor NVP-BKM120 demonstrates anti-leukemic activity in acute myeloid leukemia

Aberrant activation of the PI3K/Akt/mTOR pathway is a common feature of acute myeloid leukemia (AML) patients contributing to chemoresistance, disease progression and unfavourable outcome. Therefore, inhibition of this pathway may represent a potential therapeutic approach in AML. The aim of this study was to evaluate the pre-clinical activity of NVP-BKM120 (BKM120), a selective pan-class I PI3K inhibitor, on AML cell lines and primary samples. Our results demonstrate that BKM120 abrogates the activity of the PI3K/Akt/mTOR signaling, promoting cell growth arrest and significant apoptosis in a dose- and time-dependent manner in AML cells but not in the normal counterpart. BKM120-induced cytotoxicity is associated with a profound modulation of metabolic behaviour in both cell lines and primary samples. In addition, BKM120 synergizes with the glycolitic inhibitor dichloroacetate enhancing apoptosis induction at lower doses. Finally, in vivo administration of BKM120 to a xenotransplant mouse model of AML significantly inhibited leukemia progression and improved the overall survival of treated mice. Taken together, our findings indicate that BKM120, alone or in combination with other drugs, has a significant anti-leukemic activity supporting its clinical development as a novel therapeutic agent in AML.

Targeting the PI3K/Akt signaling pathway in gastric carcinoma: A reality for personalized medicine?

Frequent activation of phosphatidylinositol-3 kinases (PI3K)/Akt/mTOR signaling pathway in gastric cancer (GC) is gaining immense popularity with identification of mutations and/or amplifications of PIK3CA gene or loss of function of PTEN, a tumor suppressor protein, to name a few; both playing a crucial role in regulating this pathway. These aberrations result in dysregulation of this pathway eventually leading to gastric oncogenesis, hence, there is a need for targeted therapy for more effective anticancer treatment. Several inhibitors are currently in either preclinical or clinical stages for treatment of solid tumors like GC. With so many inhibitors under development, further studies on predictive biomarkers are needed to measure the specificity of any therapeutic intervention. Herein, we review the common dysregulation of PI3K/Akt/mTOR pathway in GC and the various types of single or dual pathway inhibitors under development that might have a superior role in GC treatment. We also summarize the recent developments in identification of predictive biomarkers and propose use of predictive biomarkers to facilitate more personalized cancer therapy with effective PI3K/Akt/mTOR pathway inhibition.

Targeting the PI3K/AKT/mTOR pathway: biomarkers of success and tribulation

PI3K/AKT/mTOR pathway is an established oncogenic driver in humans. Targeted biologic agents against components of this pathway have shown promising activity leading to the approval of the allosteric inhibitors of mTOR, everolimus, and temsirolimus for the treatment of advanced cancers of the kidney, breast, and pancreas. Despite the established and promising activity of this therapeutic strategy, the duration and quality of benefit remains suboptimal in unselected patients. Improved understanding of the biologic consequence of altered PI3K/AKT/mTOR signaling is informing the development of protein (phosphorylated forms of S6, AKT, eIF4e) and genetic (PIK3CA mutation, PTEN loss of function, TSC1 and TSC2 mutation, PIK3CA-GS genetic profile) biomarkers to identify patients most likely to benefit from this therapeutic strategy. This review provides an overview of the biologic rational and promising results of protein and genetic biomarkers for selecting patients appropriate for therapy with inhibitors of this pathway.

Molecular Dimensions of Gastric Cancer: Translational and Clinical Perspectives

Gastric cancer is a global health burden and has the highest incidence in East Asia. This disease is complex in nature because it arises from multiple interactions of genetic, local environmental, and host factors, resulting in biological heterogeneity. This genetic intricacy converges on molecular characteristics reflecting the pathophysiology, tumor biology, and clinical outcome. Therefore, understanding the molecular characteristics at a genomic level is pivotal to improving the clinical care of patients with gastric cancer. A recent landmark study, The Cancer Genome Atlas (TCGA) project, showed the molecular landscape of gastric cancer through a comprehensive molecular evaluation of 295 primary gastric cancers. The proposed molecular classification divided gastric cancer into four subtypes: Epstein-Barr virus–positive, microsatellite unstable, genomic stable, and chromosomal instability. This information will be taken into account in future clinical trials and will be translated into clinical therapeutic decisions. To fully realize the clinical benefit, many challenges must be overcome. Rapid growth of high-throughput biology and functional validation of molecular targets will further deepen our knowledge of molecular dimensions of this cancer, allowing for personalized precision medicine.

A phase-1, open-label, single-dose study of the pharmacokinetics of buparlisib in subjects with mild to severe hepatic impairment

The pharmacokinetics (PK) and safety of single‐dose buparlisib (30 mg) were assessed in subjects with mild to severe hepatic impairment (n = 6 each) relative to healthy controls (n = 13). Blood samples were collected until 336 hours postdose and evaluated by liquid chromatography tandem mass spectrometry. PK parameters (including area under the curve [AUC_∞] and C_max) were derived using noncompartmental analysis. Buparlisib was rapidly absorbed in all groups (median T_max 1.0–1.3 h). Buparlisib exposure (AUC_∞) was moderately increased in subjects with mild (geometric mean ratio [GMR] 1.16; 90%CI 0.81, 1.65), moderate (GMR 1.14; 90%CI 0.80, 1.63), or severe (GMR 1.20; 90%CI 0.84, 1.72) hepatic impairment, relative to healthy controls. Apparent oral clearance was similar across groups. Due to a higher unbound fraction in the severe group (0.21) than all other groups (0.17), subjects with severe hepatic impairment had greater exposure to unbound buparlisib (GMR relative to healthy controls: AUC_∞ 1.52; 90%CI 1.09, 2.13; C_max 1.83; 90%CI 1.42, 2.36). The results indicate that a buparlisib dose adjustment may not be necessary for patients with mild to moderate hepatic impairment. The safety and therapeutic indices should be considered before determining if a dose adjustment is appropriate for patients with severe hepatic impairment.

Inhibition of PI3K Pathway Reduces Invasiveness and Epithelial-to-Mesenchymal Transition in Squamous Lung Cancer Cell Lines Harboring PIK3CA Gene Alterations

A prominent role in the pathogenesis of squamous cell carcinoma of the lung (SQCLC) has been attributed to the aberrant activation of the PI3K signaling pathway, due to amplification or mutations of the p110α subunit of class I phosphatidylinositol 3-kinase (PIK3CA) gene. The aim of our study was to determine whether different genetic alterations of PIK3CA affect the biologic properties of SQCLC and to evaluate the response to specific targeting agents in vitro and in vivo. The effects of NVP-BEZ235, NVP-BKM120, and NVP-BYL719 on two-dimensional/three-dimensional (2D/3D) cellular growth, epithelial-to-mesenchymal transition, and invasiveness were evaluated in E545K or H1047R PIK3CA-mutated SQCLC cells and in newly generated clones carrying PIK3CA alterations, as well as in a xenograft model. PIK3CA mutated/amplified cells showed increased growth rate and enhanced migration and invasiveness, associated with an increased activity of RhoA family proteins and the acquisition of a mesenchymal phenotype. PI3K inhibitors reverted this aggressive phenotype by reducing metalloproteinase production, RhoA activity, and the expression of mesenchymal markers, with the specific PI3K inhibitors NVP-BKM120 and NVP-BYL719 being more effective than the dual PI3K/mTOR inhibitor NVP-BEZ235. A xenograft model of SQCLC confirmed that PIK3CA mutation promotes the acquisition of a mesenchymal phenotype in vivo and proved the efficacy of its specific targeting drug NVP-BYL719 in reducing the growth and the expression of mesenchymal markers in xenotransplanted tumors. These data indicate that PIK3CA mutation/amplification may represent a good predictive feature for the clinical application of specific PI3K inhibitors in SQCLC patients.

Advances in subunits of PI3K class I in cancer

Phosphatidylinositol 3-kinases (PI3Ks) include members of a unique and conserved family of intracellular lipid kinases that phosphorylate the 3-hydroxyl group of phosphatidylinositols and phosphoinositides. The resultant activation of many intracellular signalling pathways regulates various biological functions such as cell metabolism, survival, growth, proliferation, polarity, and apoptosis. PI3Ks are classified into three types: class I, II, and III. Of them, class I PI3K is most widely studied and plays an important role in the development and progression of tumours. In this review, we describe PI3K family members and their functions, especially the subunits of class I PI3K, their alterations in cancers, as well as PI3K inhibitors and their clinical trial status in cancer-targeted therapy.

Treatment effect of buparlisib, cetuximab and irradiation in wild-type or PI3KCA-mutated head and neck cancer cell lines

Introduction In complement to anti-EGFR therapy, the targeting of PI3K/AKT/mTOR signaling pathway is of particular interest in the management of Head and Neck Squamous Cell Carcinoma (HNSCC). Here, we assess the effects of PI3K inhibition combined with anti-EGFR monoclonal antibody cetuximab and/or irradiation (RT). Material and methods Anti-proliferative effects of the combination of buparlisib (a specific PI3K inhibitor), cetuximab and RT was determined in two HNSCC cell lines (CAL33, PI3KCA H1047R-mutated and CAL27, PI3KCA wild-type). We examined biochemical factors related to proliferation, apoptosis (caspases), DNA repair (ERCC1, XRCC1) and the PI3K pathway (pEGFR/EGFR, pAKT/AKT, p-p70, p4EBP1). Results The best synergistic combined treatment in inhibiting cell proliferation was sequence 2 (cetuximab followed by buparlisib) in both cell lines. Addition of RT increased sequence 2 anti-proliferative effect only in CAL27. Data on protein expression indicated a possible activation of mTORC2 complex and caspases proteins in CAL27 not seen in CAL33. In CAL33, the synergistic anti-proliferative effect of the two drugs may derive from the higher sensitivity of mutated cells to PI3K targeting. Conclusions Our study demonstrates a synergistic effect of cetuximab followed by buparlisib in both PI3KCA wild-type and mutated cells, even with different intracellular signaling cross-talk depending on mutational status.

ErbB2 signaling activates the Hedgehog pathway via PI3K-Akt in human esophageal adenocarcinoma: identification of novel targets for concerted therapy concepts

The Hedgehog pathway plays an important role in the pathogenesis of several tumor types, including esophageal cancer. In our study, we show an expression of the ligand Indian hedgehog (Ihh) and its downstream mediator Gli-1 in primary resected adenocarcinoma tissue by immunohistochemistry and quantitative PCR in fifty percent of the cases, while matching healthy esophagus mucosa was negative for both proteins. Moreover, a functionally important regulation of Gli-1 by ErbB2-PI3K-mTORC signaling as well as a Gli-1-dependent regulation of Ihh in the ErbB2 amplified esophageal adenocarcinoma cell line OE19 was observed. Treatment of OE19 cells with the Her2 antibody trastuzumab, the PI3K-mTORC1 inhibitor NVP BEZ235 (BEZ235) or the knockdown of Akt1 resulted in a downregulation of Gli-1 and Ihh as well as in a reduction of viable OE19 cells in vitro. Interestingly, the Hedgehog receptor Smo, which acts upstream of Gli-1, was not expressed in OE19 cells and in the majority of primary human esophageal adenocarcinoma, suggesting a non-canonical upregulation of Gli-1 expression by the ErbB2-PI3K axis. To translate our findings into a therapeutic concept, we targeted ErbB2-PI3K-mTORC1 by trastuzumab and BEZ235, combining both compounds with the Gli-1/2 inhibitor GANT61. The triple combination led to significantly stronger reduction of tumor cell viability than cisplatinum or each biological alone. Therefore, concomitant blockage of the ErbB2-PI3K pathway and the Hedgehog downstream mediator Gli-1 may provide a new therapeutic strategy for esophageal cancer.

Targeting survival and cell trafficking in multiple myeloma and Waldenstrom macroglobulinemia using pan-class I PI3K inhibitor, buparlisib

The phosphatidylinositol-3 kinase (PI3K) pathway is activated in multiple myeloma (MM) and Waldenstrom Macroglobulenima (WM), and plays a crucial role in tumor progression and drug resistance. In this study, we characterized the role of pan-class I PI3K inhibition on cell trafficking and survival of MM and WM cells. We tested the effect of pan-class I PI3K inhibition by siRNA silencing or pharmacologic inhibition with buparlisib on MM cell survival, apoptosis and cell cycle in vitro and tumor growth and mobilization of MM cells in vivo. We then evaluated buparlisib-dependent mechanisms of induced MM cell mobilization. Moreover, the effect of buparlisib on cell survival, apoptosis, and adhesion of WM cells to bone marrow stromal cells (BMSCs) has been evaluated. We showed that buparlisib induced toxicity in MM cells, supported by induction of apoptosis and cell cycle arrest. Buparlisib was also found to reduce tumor progression in vivo. Importantly, buparlisib enhanced MM cell mobilization in vivo which was driven by decreased adhesion of MM cells to BMSCs and increased chemotaxis via up-regulation of CXCR4 expression. Similar to its effects on MM cells, buparlisib also induced cell survival and apoptosis, and decreased adhesion in WM cells. These data highlight the critical contribution of class I PI3K signaling to the regulation of survival and cell dissemination in B-cell malignancies.

Detection of PI3K inhibition in human neuroblastoma using multiplex luminex bead immunoassay: a targeted approach for pathway analysis

Neuroblastoma (NB) is a common solid tumor in children. Outcomes for advanced stage NB have not improved, at least in part because of multimodality therapy resistance. Better comprehension of novel molecular targets will likely lead to improved therapies with specific cytotoxic agents. For instance, the role of deregulated IGF-1R/AKT/PI3K/mTOR (PI3K) pathway activity has attracted much attention across several tumors, including NB. Thus, modulating this pathway via anti-PI3K drugs has taken center stage in many cancer clinical trials. However, varied clinical effects have hampered the precise application of these agents. Tumor PI3K pathway profiling may reveal a method to enhance the efficacy of these inhibitors. To this end, solid-phase antibody-based array platforms have emerged as a direct, rapid means of profiling intracellular signaling pathways. We tested the efficacy of four PI3K inhibitors against a panel of human NB cell lines using Luminex xMAP bead array technology to establish PI3K phosphoprotein profiles. We demonstrate the utility of the xMAP approach in following intracellular signaling signatures specific for PI3K targeted therapy. Further validation is required before xMAP is used routinely for clinical PI3K pathway evaluation, but this method may eventually be personalized by taking into account each child's basal NB pathway status.

PIK3CA gene mutations and overexpression: implications for prognostic biomarker and therapeutic target in Chinese esophageal squamous cell carcinoma

Aims

To evaluate PIK3CA gene mutations and PIK3CA expression status in Chinese esophageal squamous cell carcinoma (ESCC) patients, and their correlation with clinicopathological characteristics and clinical outcomes.

Methods

Direct sequencing was applied to investigate mutations in exons 9 and 20 of PIK3CA in 406 Chinese ESCC patients. PIK3CA expression was evaluated using immunohistochemistry analysis. The associations of PIK3CA gene mutations and PIK3CA expression with clinicopathological characteristics and clinical outcome were examined.

Results

Thirty somatic point mutations (30/406, 7.4%) were identified in exon 9 whereas no mutations were detected in exon 20. PIK3CA mutations were not correlated with clinicopathological characteristics or clinical outcomes. However in the ESCC patients with family cancer history, PIK3CA mutations were independently correlated with worse overall survival (multivariate hazard ratio (HR) = 10.493, 95% CI: 2.432–45.267, P = 0.002). Compared to normal esophageal tissue, PIK3CA was significantly overexpressed in cancer tissue (P<0.001). PIK3CA overexpression was independently associated with higher risk of local recurrence (multivariate HR  = 1.435, 95% CI: 1.040–1.979, P = 0.028). In female ESCC patients, PIK3CA overexpression was independently correlated with worse overall survival (multivariate HR  = 2.341, 95% CI: 1.073–5.108, P = 0.033).

Conclusions

Our results suggest PIK3CA gene mutation and overexpression could act as biomarkers for individualized molecular targeted therapy for Chinese ESCC patients.

Effective inhibition of colon cancer cell growth with MgAl-layered double hydroxide (LDH) loaded 5-FU and PI3K/mTOR dual inhibitor BEZ-235 through apoptotic pathways

Colon cancer is the third most common cancer and the third largest cause of cancer-related death. Fluorouracil (5-FU) is the front-line chemotherapeutic agent for colon cancer. However, its response rate is less than 60%, even in combination with other chemotherapeutic agents. The side effects of 5-FU also limit its application. Nanoparticles have been used to deliver 5-FU, to increase its effectiveness and reduce side effects. Another common approach for colon cancer treatment is targeted therapy against the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway. A recently-invented inhibitor of this pathway, BEZ-235, has been tested in several clinical trials and has shown effectiveness and low side effects. Thus, it is a very promising drug for colon cancer treatment. The combination of these two drugs, especially nanoparticle-packed 5-FU and BEZ-235, has not been studied. In the present study, we demonstrated that nanoparticles of layered double hydroxide (LDH) loaded with 5-FU were more effective than a free drug at inhibiting colon cancer cell growth, and that a combination treatment with BEZ-235 further increased the sensitivity of colon cancer cells to the treatment of LDH-packed 5-FU (LDH-5-FU). BEZ-235 alone can decrease colon cancer HCT-116 cell viability to 46% of the control, and the addition of LDH-5-FU produced a greater effect, reducing cell survival to 8% of the control. Our data indicate that the combination therapy of nanodelivered 5-FU with a PI3K/Akt inhibitor, BEZ-235, may promise a more effective approach for colon cancer treatment.

The Role of PI3K/Akt/mTOR Signaling in Gastric Carcinoma

The phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is one of the key signaling pathways induced by various receptor-tyrosine kinases. Accumulating evidence shows that this pathway is an important promoter of cell growth, metabolism, survival, metastasis, and resistance to chemotherapy. Genetic alterations in the PI3K/Akt/mTOR pathway in gastric carcinoma have often been demonstrated. Many kinds of molecular targeting therapies are currently undergoing clinical testing in patients with solid tumors. However, with the exception of the ErbB2-targeting antibody, targeting agents, including PI3K/Akt/mTOR inhibitors, have not been approved for treatment of patients with gastric carcinoma. This review summarizes the current knowledge on PI3K/Akt/mTOR signaling in the pathogenesis of gastric carcinoma and the possible therapeutic targets for gastric carcinoma. Improved knowledge of the PI3K/Akt/mTOR pathway in gastric carcinoma will be useful in understanding the mechanisms of tumor development and for identifying ideal targets of anticancer therapy for gastric carcinoma.

Targeting the PI3K-AKT-mTOR signaling network in cancer

The phosphoinositide 3-kinase-AKT-mammalian target of rapamycin (PI3K-AKT-mTOR) pathway is a frequently hyperactivated pathway in cancer and is important for tumor cell growth and survival. The development of targeted therapies against mTOR, a vital substrate along this pathway, led to the approval of allosteric inhibitors, including everolimus and temsirolimus, for the treatment of breast, renal, and pancreatic cancers. However, the suboptimal duration of response in unselected patients remains an unresolved issue. Numerous novel therapies against critical nodes of this pathway are therefore being actively investigated in the clinic in multiple tumour types. In this review, we focus on the progress of these agents in clinical development along with their biological rationale, the need of predictive biomarkers and various combination strategies, which will be useful in counteracting the mechanisms of resistance to this class of drugs.

Targeting mTOR network in colorectal cancer therapy

The mechanistic target of rapamycin (mTOR) integrates growth factor signals with cellular nutrient and energy levels and coordinates cell growth, proliferation and survival. A regulatory network with multiple feedback loops has evolved to ensure the exquisite regulation of cell growth and division. Colorectal cancer is the most intensively studied cancer because of its high incidence and mortality rate. Multiple genetic alterations are involved in colorectal carcinogenesis, including oncogenic Ras activation, phosphatidylinositol 3-kinase pathway hyperactivation, p53 mutation, and dysregulation of wnt pathway. Many oncogenic pathways activate the mTOR pathway. mTOR has emerged as an effective target for colorectal cancer therapy. In vitro and preclinical studies targeting the mTOR pathway for colorectal cancer chemotherapy have provided promising perspectives. However, the overall objective response rates in major solid tumors achieved with single-agent rapalog therapy have been modest, especially in advanced metastatic colorectal cancer. Combination regimens of mTOR inhibitor with agents such as cytotoxic chemotherapy, inhibitors of vascular endothelial growth factor, epidermal growth factor receptor and Mitogen-activated protein kinase kinase (MEK) inhibitors are being intensively studied and appear to be promising. Further understanding of the molecular mechanism in mTOR signaling network is needed to develop optimized therapeutic regimens. In this paper, oncogenic gene alterations in colorectal cancer, as well as their interaction with the mTOR pathway, are systematically summarized. The most recent preclinical and clinical anticancer therapeutic endeavors are reviewed. New players in mTOR signaling pathway, such as non-steroidal anti-inflammatory drug and metformin with therapeutic potentials are also discussed here.

Moguntinones--new selective inhibitors for the treatment of human colorectal cancer

3-Indolyl and 3-azaindolyl-4-aryl maleimide derivatives, called moguntinones (MOG), have been selected for their ability to inhibit protein kinases associated with angiogenesis and induce apoptosis. Here, we characterize their mode of action and their potential clinical value in human colorectal cancer in vitro and in vivo. MOG-19 and MOG-13 were characterized in vitro using kinase, viability, and apoptosis assays in different human colon cancer (HT-29, HCT-116, Caco-2, and SW480) and normal colon cell lines (CCD-18Co, FHC, and HCoEpiC) alone or in combination with topoisomerase I inhibitors. Intracellular signaling pathways were analyzed by Western blotting. To determine their potential to inhibit tumor growth in vivo, the human HT-29 tumor xenograft model was used. Moguntinones prominently inhibit several protein kinases associated with tumor growth and metastasis. Specific signaling pathways such as GSK3β and mTOR downstream targets were inhibited with IC(50) values in the nanomolar range. GSK3β signaling inhibition was independent of KRAS, BRAF, and PI3KCA mutation status. While moguntinones alone induced apoptosis only in concentrations >10 μmol/L, MOG-19 in combination with topoisomerase I inhibitors induced apoptosis synergistically at lower concentrations. Consistent with in vitro data, MOG-19 significantly reduced tumor volume and weight in combination with a topoisomerase I inhibitor in vivo. Our in vitro and in vivo data present significant proapoptotic, antiangiogenic, and antiproliferative effects of MOG-19 in different human colon cancer cells. Combination with clinically relevant topoisomerase I inhibitors in vitro and xenograft mouse model demonstrate a high potency of moguntinones to complement and improve standard chemotherapy options in human colorectal cancer.

Phase I dose-escalation study of buparlisib (BKM120), an oral pan-class I PI3K inhibitor, in Japanese patients with advanced solid tumors

Buparlisib (BKM120) is an oral pan-phosphatidylinositol 3-kinase inhibitor, targeting all four isoforms of class I PI3K (α, β, γ and δ). This open-label Phase I dose-escalation study was conducted to determine the maximum tolerated dose of continuous daily buparlisib in Japanese patients with advanced solid tumors. Secondary objectives included safety and tolerability, pharmacokinetics, antitumor activity and pharmacodynamic marker changes. Fifteen patients were treated at 25 mg/day (n = 3), 50 mg/day (n = 3) and 100 mg/day (n = 9) dose levels. One dose-limiting toxicity of Grade 4 abnormal liver function occurred at 100 mg/day. Considering the safety profile and the maximum tolerated dose in the first-in-man study of buparlisib in non-Japanese patients, further dose escalation was stopped and 100 mg/day was declared the recommended dose. The most common treatment-related adverse events were rash, abnormal hepatic function (including increased transaminase levels), increased blood insulin levels and increased eosinophil count. Hyperglycemia was experienced by two patients, one Grade 1 and one Grade 4, and mood alterations were experienced by three patients, two Grade 1 and one Grade 2. Pharmacokinetic results showed that buparlisib was rapidly absorbed in a dose-proportional manner. Best overall response was stable disease for six patients, including one unconfirmed partial response. In these Japanese patients with advanced solid tumors, buparlisib had a manageable safety profile, with similar pharmacokinetics to non-Japanese patients. The recommended dose of 100 mg/day will be used in future studies of buparlisib in Japanese patients.