The PI3K/AKT Pathway as a Target for Cancer Treatment

Overexpression of PIK3CA in head and neck squamous cell carcinoma is associated with poor outcome and activation of the YAP pathway

OBJECTIVES

Phosphatidylinositol 3-kinase catalytic subunit alpha (PIK3CA) is commonly altered in many human tumors, leading to the activation of p110α enzymatic activity that stimulates growth factor-independent cell growth. PIK3CA alterations such as mutation, gene amplification and overexpression are common in head and neck squamous cell carcinoma (HNSCC) and. We aim to explore how these alterations and clinical outcome are associated, as well as the molecular mechanisms involved.

MATERIAL AND METHODS

Mutation and copy-number variation in PIK3CA, and whole-genome expression profiles, were analyzed in primary HNSCC tumors from The Cancer Genome Atlas (TCGA) cohort (n = 243). The results were validated in an independent cohort form the University Hospital of A Coruña (UHAC, n = 62). Expression of the PIK3CA gene protein product (PI3K p110α) and nuclear YAP were assessed in tissue microarrays in a cohort from the University Hospital 12 de Octubre (UH12O, n = 91).

RESULTS

Only high expression of the PIK3CA gene was associated with poor clinical outcome. The study of gene expression, transcription factor and protein signatures suggested that the activation of the Hippo-YAP pathway, involved in organ size, stem cell maintenance and tumorigenesis, could underlie tumor progression in PI3KCA overexpressing tumors. Tissue arrays showed that PI3K p110α levels correlated with YAP nuclear localization in HNSCC tumors.

CONCLUSIONS

High expression of PIK3CA in HNSCC primary tumors identifies patients at high risk for recurrence. In these tumors, progression could rely on the Hippo-YAP pathway instead of the canonical Akt/mTOR pathway. This observation could have important implications in the therapeutic options for patients.

Curcumin inhibits superoxide dismutase-induced epithelial-to-mesenchymal transition via the PI3K/Akt/NF-κB pathway in pancreatic cancer cells

Curcumin is a natural polyphenol compound derived from turmeric. It possesses multiple pharmacological properties, including antioxidant, anti-inflammatory and anti-tumor progression properties. Our recent study demonstrated that superoxide dismutase (SOD)-dependent production of hydrogen peroxide (H2O2) promoted the invasive and migratory activity of pancreatic cancer cells. However, whether curcumin suppresses SOD-induced cancer progression and the related mechanisms remains unclear. Since epithelial‑to-mesenchymal transition (EMT) plays a key role in tumor metastasis, the aim of the present study was to examine whether curcumin intervenes with SOD-induced EMT in pancreatic cancer and the underlying mechanism. The human pancreatic cancer cells BxPC-3 and Panc-1 were exposed to SOD in the presence or absence of curcumin, catalase (CAT, a scavenger of H2O2), or LY 294002 [a phosphoinositide-3 kinase (PI3K) inhibitor]. Intracellular reactive oxygen species (ROS) and H2O2 were evaluated by 2,7-dichlorodihydrofluorecein diacetate and H2O2 assay, respectively. The activation of p-Akt and p-nuclear factor (NF)-κB were examined by western blotting. The migratory and invasive abilities of pancreatic cancer cells were tested by the wound healing and Transwell invasion assays. The expression of E-cadherin, N-cadherin and vimentin (EMT-related genes) were measured by reverse transcription-quantitative polymerase chain reaction and western blotting at the mRNA and protein levels, respectively. The findings of the present study demonstrated that curcumin decreased SOD-induced production of ROS and H2O2 in BxPC-3 and Panc-1 cells. Curcumin was able to suppress SOD-induced invasion and migration, and it also regulated the expression of the above‑mentioned EMT-related genes and cell morphology. SOD-induced cell invasion was also inhibited by catalase and LY 294002. Furthermore, the levels of p-Akt and p-NF-κB caused by SOD could be offset by treatment with curcumin and LY 294002. To summarize, these results demonstrated that curcumin was able to prevent SOD-driven H2O2-induced pancreatic cancer metastasis by blocking the PI3K/Akt/NF-κB signaling pathway. The use of curcumin to inhibit the H2O2/Akt/NF-κB axis may be a promising therapeutic approach to the treatment of patients with pancreatic cancer.

Cardiac Arrhythmias and Antiarrhythmic Drugs: An Autophagic Perspective

Degradation of cellular material by lysosomes is known as autophagy, and its main function is to maintain cellular homeostasis for growth, proliferation and survival of the cell. In recent years, research has focused on the characterization of autophagy pathways. Targeting of autophagy mediators has been described predominantly in cancer treatment, but also in neurological and cardiovascular diseases. Although the number of studies is still limited, there are indications that activity of autophagy pathways increases under arrhythmic conditions. Moreover, an increasing number of antiarrhythmic and non-cardiac drugs are found to affect autophagy pathways. We, therefore, suggest that future work should recognize the largely unaddressed effects of antiarrhythmic agents and other classes of drugs on autophagy pathway activation and inhibition.

The long non-coding RNA FOXD2-AS1 promotes bladder cancer progression and recurrence through a positive feedback loop with Akt and E2F1

Long non-coding RNAs (lncRNAs) have been identified as significant regulators in cancer progression. Positive feedback loops between lncRNAs and transcription factors have attracted increasing attention. Akt pathway plays a crucial role in bladder cancer growth and recurrence. In the present study, we demonstrate a novel regulatory pattern involving FOXD2-AS1, Akt, and E2F1. FOXD2-AS1 is highly expressed in bladder cancer and is associated with tumor stage, recurrence, and poor prognosis. Further experiments showed that FOXD2-AS1 promotes bladder cancer cell proliferation, migration, and invasion in vitro and in vivo. Microarray analysis demonstrated that FOXD2-AS1 negatively regulates the expression of Tribbles pseudokinase 3 (TRIB3), a negative regulator of Akt. Mechanistically, FOXD2-AS1 forms an RNA-DNA complex with the promoter of TRIB3, the transcriptional activity of which is subsequently repressed, and leads to the activation of Akt, which further increases the expression of E2F1, a vital transcription factor involved in the G/S transition. Interestingly, E2F1 could bind to the FOXD2-AS1 promoter region and subsequently enhance its transcriptional activity, indicating that FOXD2-AS1/Akt/E2F1 forms a feedback loop. In summary, this regulatory pattern of positive feedback may be a novel target for the treatment of bladder cancer and FOXD2-AS1 has the potential to be a new recurrence predictor.

Flavagline analog FL3 induces cell cycle arrest in urothelial carcinoma cell of the bladder by inhibiting the Akt/PHB interaction to activate the GADD45α pathway

BACKGROUND

Prohibitin 1 (PHB) is a potential target for the treatment of urothelial carcinoma of the bladder (UCB). FL3 is a newly synthesized agent that inhibits cancer cell proliferation by targeting the PHB protein; however, the effect of FL3 in UCB cells remains unexplored.

METHODS

FL3 was identified to be a potent inhibitor of UCB cell viability using CCK-8 (cell counting kit-8) assay. Then a series of in vitro and in vivo experiments were conducted to further demonstrate the inhibitory effect of FL3 on UCB cell proliferation and to determine the underlying mechanisms.

RESULTS

FL3 inhibited UCB cell proliferation and growth both in vitro and in vivo. By targeting the PHB protein, FL3 inhibited the interaction of Akt and PHB as well as Akt-mediated PHB phosphorylation, which consequently decreases the localization of PHB in the mitochondria. In addition, FL3 treatment resulted in cell cycle arrest in the G2/M phase, and this inhibitory effect of FL3 could be mimicked by knockdown of PHB. Through the microarray analysis of mRNA expression after FL3 treatment and knockdown of PHB, we found that the mRNA expression of the growth arrest and DNA damage-inducible alpha (GADD45α) gene were significantly upregulated. When knocked down the expression of GADD45α, the inhibitory effect of FL3 on cell cycle was rescued, suggesting that FL3-induced cell cycle inhibition is GADD45α dependent.

CONCLUSION

Our data provide that FL3 inhibits the interaction of Akt and PHB, which in turn activates the GADD45α-dependent cell cycle inhibition in the G2/M phase.

Therapeutic target discovery using Boolean network attractors: improvements of kali

In a previous article, an algorithm for identifying therapeutic targets in Boolean networks modelling pathological mechanisms was introduced. In the present article, the improvements made on this algorithm, named kali, are described. These improvements are (i) the possibility to work on asynchronous Boolean networks, (ii) a finer assessment of therapeutic targets and (iii) the possibility to use multivalued logic. kali assumes that the attractors of a dynamical system, such as a Boolean network, are associated with the phenotypes of the modelled biological system. Given a logic-based model of pathological mechanisms, kali searches for therapeutic targets able to reduce the reachability of the attractors associated with pathological phenotypes, thus reducing their likeliness. kali is illustrated on an example network and used on a biological case study. The case study is a published logic-based model of bladder tumorigenesis from which kali returns consistent results. However, like any computational tool, kali can predict but cannot replace human expertise: it is a supporting tool for coping with the complexity of biological systems in the field of drug discovery.

Molecular Pathways: Targeting the PI3K Pathway in Cancer-BET Inhibitors to the Rescue

The PI3K signaling pathway is a complex and tightly regulated network that is critical for many physiologic processes, such as cell growth, proliferation, metabolism, and survival. Aberrant activation of this pathway can occur through mutation of almost any of its major nodes and has been implicated in a number of human diseases, including cancer. The high frequency of mutations in this pathway in multiple types of cancer has led to the development of small-molecule inhibitors of PI3K, several of which are currently in clinical trials. However, several feedback mechanisms either within the PI3K pathway or in compensatory pathways can render tumor cells resistant to therapy. Recently, targeting proteins of the bromodomain and extraterminal (BET) family of epigenetic readers of histone acetylation has been shown to effectively block adaptive signaling response of cancer cells to inhibitors of the PI3K pathway, which at least in some cases can restore sensitivity. BET inhibitors also enforce blockade of the MAPK, JAK/STAT, and ER pathways, suggesting they may be a rational combinatorial partner for divergent oncogenic signals that are subject to homeostatic regulation. Here, we review the PI3K pathway as a target for cancer therapy and discuss the potential use of BET inhibition to enhance the clinical efficacy of PI3K inhibitors. Clin Cancer Res; 22(11); 2605-10. ©2016 AACR.

mTOR Cross-Talk in Cancer and Potential for Combination Therapy

The mammalian Target of Rapamycin (mTOR) pathway plays an essential role in sensing and integrating a variety of exogenous cues to regulate cellular growth and metabolism, in both physiological and pathological conditions. mTOR functions through two functionally and structurally distinct multi-component complexes, mTORC1 and mTORC2, which interact with each other and with several elements of other signaling pathways. In the past few years, many new insights into mTOR function and regulation have been gained and extensive genetic and pharmacological studies in mice have enhanced our understanding of how mTOR dysfunction contributes to several diseases, including cancer. Single-agent mTOR targeting, mostly using rapalogs, has so far met limited clinical success; however, due to the extensive cross-talk between mTOR and other pathways, combined approaches are the most promising avenues to improve clinical efficacy of available therapeutics and overcome drug resistance. This review provides a brief and up-to-date narrative on the regulation of mTOR function, the relative contributions of mTORC1 and mTORC2 complexes to cancer development and progression, and prospects for mTOR inhibition as a therapeutic strategy.

EGCG inhibited bladder cancer T24 and 5637 cell proliferation and migration via PI3K/AKT pathway

Epigallocatechin-3-gallate (EGCG), the bioactive polyphenol in green tea, has been demonstrated to have various biological activities. We previously found that EGCG inhibited SW780 tumor growth by down-regulation of NF-κB and MMP-9. This study demonstrated that EGCG inhibited bladder cancer T24 and 5637 cell proliferation and migration via PI3K/AKT pathway, without modulation of NF-κB. Our results showed that treatment of EGCG resulted in significant inhibition of cell proliferation by induction of apoptosis, without obvious toxicity to normal bladder SV-HUC-1 cells. EGCG also inhibited 5637 and T24 cell migration and invasion at 25-100 μM. Western blot confirmed that EGCG induced apoptosis in T24 and 5637cells by activation of caspases-3 and PARP. Besides, EGCG up-regulated PTEN and decreased the expression of phosphorylated PI3K, AKT in both T24 and 5637 cells. In addition, animal study demonstrated that EGCG (100 mg/kg, i.p. injected daily for 4 weeks) decreased the tumor weight in mice bearing T24 tumors by 51.2%, as compared with the untreated control. EGCG also decreased the expression of phosphorylated PI3K and AKT in tumor, indicating the important role of PI3K/AKT in EGCG inhibited tumor growth. When AKT was inhibited, EGCG showed no obvious effect in cell migration in T24 and 5637 cells. In conclusion, our study elucidated that EGCG was effective in inhibition of T24 and 5637 cell proliferation and migration, and presented evidence that EGCG inhibited cell proliferation and tumor growth by modulation of PI3K/AKT pathway.

PI3K/AKT/mTOR pathway in multiple myeloma: from basic biology to clinical promise

Multiple myeloma (MM), a cancer of terminally differentiated plasma cells, is the second most common hematological malignancy. The disease is characterized by the accumulation of abnormal plasma cells in the bone marrow that remains in close association with other cells in the marrow microenvironment. In addition to the genomic alterations that commonly occur in MM, the interaction with cells in the marrow microenvironment promotes signaling events within the myeloma cells that enhances survival of MM cells. The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) is such a pathway that is aberrantly activated in a large proportion of MM patients through numerous mechanisms and can play a role in resistance to several existing therapies making this a central pathway in MM pathophysiology. Here, we review the pathway, its role in MM, promising preclinical results obtained thus far and the clinical promise that drugs targeting this pathway have in MM.

A network modeling approach to elucidate drug resistance mechanisms and predict combinatorial drug treatments in breast cancer

Background

Mechanistic models of within-cell signal transduction networks can explain how these networks integrate internal and external inputs to give rise to the appropriate cellular response. These models can be fruitfully used in cancer cells, whose aberrant decision-making regarding their survival or death, proliferation or quiescence can be connected to errors in the state of nodes or edges of the signal transduction network.

Results

Here we present a comprehensive network, and discrete dynamic model, of signal transduction in ER+ breast cancer based on the literature of ER+, HER2+, and PIK3CA-mutant breast cancers. The network model recapitulates known resistance mechanisms to PI3K inhibitors and suggests other possibilities for resistance. The model also reveals known and novel combinatorial interventions that are more effective than PI3K inhibition alone.

Conclusions

The use of a logic-based, discrete dynamic model enables the identification of results that are mainly due to the organization of the signaling network, and those that also depend on the kinetics of individual events. Network-based models such as this will play an increasing role in the rational design of high-order therapeutic combinations.

Electronic supplementary material

The online version of this article (10.1186/s41236-017-0007-6) contains supplementary material, which is available to authorized users.

hnRNPM guides an alternative splicing program in response to inhibition of the PI3K/AKT/mTOR pathway in Ewing sarcoma cells

Ewing sarcomas (ES) are biologically aggressive tumors of bone and soft tissues for which no cure is currently available. Most ES patients do not respond to chemotherapeutic treatments or acquire resistance. Since the PI3K/AKT/mTOR axis is often deregulated in ES, its inhibition offers therapeutic perspective for these aggressive tumors. Herein, by using splicing sensitive arrays, we have uncovered an extensive splicing program activated upon inhibition of the PI3K/AKT/mTOR signaling pathway by BEZ235. Bioinformatics analyses identified hnRNPM as a key factor in this response. HnRNPM motifs were significantly enriched in introns flanking the regulated exons and proximity of binding represented a key determinant for hnRNPM-dependent splicing regulation. Knockdown of hnRNPM expression abolished a subset of BEZ235-induced splicing changes that contained hnRNPM binding sites, enhanced BEZ235 cytotoxicity and limited the clonogenicity of ES cells. Importantly, hnRNPM up-regulation correlates with poor outcome in sarcoma patients. These findings uncover an hnRNPM-dependent alternative splicing program set in motion by inhibition of the mTOR/AKT/PI3K pathway in ES cells that limits therapeutic efficacy of pharmacologic inhibitors, suggesting that combined inhibition of the PI3K/AKT/mTOR pathway and hnRNPM activity may represent a novel approach for ES treatment.

Dual blockade of the lipid kinase PIP4Ks and mitotic pathways leads to cancer-selective lethality

Achieving robust cancer-specific lethality is the ultimate clinical goal. Here, we identify a compound with dual-inhibitory properties, named a131, that selectively kills cancer cells, while protecting normal cells. Through an unbiased CETSA screen, we identify the PIP4K lipid kinases as the target of a131. Ablation of the PIP4Ks generates a phenocopy of the pharmacological effects of PIP4K inhibition by a131. Notably, PIP4Ks inhibition by a131 causes reversible growth arrest in normal cells by transcriptionally upregulating PIK3IP1, a suppressor of the PI3K/Akt/mTOR pathway. Strikingly, Ras activation overrides a131-induced PIK3IP1 upregulation and activates the PI3K/Akt/mTOR pathway. Consequently, Ras-transformed cells override a131-induced growth arrest and enter mitosis where a131’s ability to de-cluster supernumerary centrosomes in cancer cells eliminates Ras-activated cells through mitotic catastrophe. Our discovery of drugs with a dual-inhibitory mechanism provides a unique pharmacological strategy against cancer and evidence of cross-activation between the Ras/Raf/MEK/ERK and PI3K/AKT/mTOR pathways via a Ras˧PIK3IP1˧PI3K signaling network.

The Ras/Raf/MEK/ERK and PI3K/Akt/mTOR signaling pathways are essential for cancer cell survival. Here, the authors describes a molecule a131 with dual-inhibitory properties, which targets PI5P4K and mitosis, and it is involved in Ras/Raf/MEK/ERK and PI3K/Akt/mTOR crosstalk, thereby causing reversible growth arrest in normal cells and cell death of tumor cells.

Targeted molecular profiling reveals genetic heterogeneity of poromas and porocarcinomas

The genetic landscape of rare benign tumours and their malignant counterparts is still largely unexplored. While recent work showed that mutant HRAS is present in subsets of poromas and porocarcinomas, a more comprehensive genetic view on these rare adnexal neoplasms is lacking. Using high-coverage next generation sequencing, we investigated the mutational profile of 50 cancer-related genes in 12 cases (six poromas and six porocarcinomas). Non-synonymous mutations were found in two-thirds of both poromas and porocarcinomas. Hotspot HRAS mutations were identified in two poromas (p.G13R and p.Q61R) and one porocarcinoma (p.G13C). While in poromas only few cases showed single mutated genes, porocarcinomas showed greater genetic heterogeneity with up to six mutated genes per case. Recurrent TP53 mutations were found in all porocarcinomas that harboured mutated genes. Non-recurrent mutations in porocarcinomas were found in several additional tumour suppressors (RB1, APC, CDKN2A, and PTEN), and genes implicated in PI3K-AKT and MAPK signalling pathways (ABL1, PDGFRA, PIK3CA, HRAS, and RET). UV-associated mutations were found in TP53, APC, CDKN2A, PTEN, and RET. In conclusion, our study confirms and extends the spectrum of genetic lesions in poromas and porocarcinomas. While poromas exhibited only few mutations, which did not involve TP53, the majority of porocarcinomas harboured UV-mediated mutations in TP53 with some of these cases showing considerable genetic heterogeneity that may be clinically exploitable.

Glycogen Synthase Kinase 3 Inactivation Compensates for the Lack of CD28 in the Priming of CD8+ Cytotoxic T-Cells: Implications for anti-PD-1 Immunotherapy

The rescue of exhausted CD8⁺ cytolytic T-cells (CTLs) by anti-Programmed Cell Death-1 (anti-PD-1) blockade has been found to require CD28 expression. At the same time, we have shown that the inactivation of the serine/threonine kinase glycogen synthase kinase (GSK)-3α/β with small-interfering RNAs (siRNAs) and small molecule inhibitors (SMIs) specifically down-regulates PD-1 expression for enhanced CD8⁺ CTL function and clearance of tumors and viral infections. Despite this, it has been unclear whether the GSK-3α/β pathway accounts for CD28 costimulation of CD8⁺ CTL function. In this article, we show that inactivation of GSK-3α/β through siRNA or by SMIs during priming can substitute CD28 co-stimulation in the potentiation of cytotoxic CD8⁺ CTL function against the EL-4 lymphoma cells expressing OVA peptide. The effect was seen using several structurally distinct GSK-3 SMIs and was accompanied by an increase in Lamp-1 and GZMB expression. Conversely, CD28 crosslinking obviated the need for GSK-3α/β inhibition in its enhancement of CTL function. Our findings support a model where GSK-3 is the central cosignal for CD28 priming of CD8⁺ CTLs in anti-PD-1 immunotherapy.

PTEN loss and level of HER2 amplification is associated with trastuzumab resistance and prognosis in HER2-positive gastric cancer

Background

Trastuzumab is an active agent against human epidermal growth factor receptor 2 (HER2)-positive gastric cancer (GC). This study aimed to characterize resistance to trastuzumab-based front-line chemotherapy in HER2+ GC patients and to establish factors predictive of this resistance.

Results

Among 129 HER2+ GC patients, 25% displayed rapid disease progression within 4 months from initiation of therapy. These patients showed a higher rate of signet ring cell histology, bone metastasis, poor performance status, frequent loss of PTEN expression, and low HER2 amplification index compared with patients who were progression-free for at least 4 months. In contrast, there was no significant difference in the frequency of the PIK3R1 variant. Multivariate analyses confirmed two independent molecular predictors for trastuzumab resistance: loss of PTEN expression and low HER2 amplification index (<5). Patients with one or both molecular predictors at diagnosis exhibited worse progression-free and overall survival compared to those without risk factors (p < 0.001 and p = 0.001, respectively).

Conclusion

In HER2+ GC patients, loss of PTEN expression and low HER2 AI correlated with resistance to trastuzumab-based therapy and dismal prognosis. Since patients harboring these molecular predictors are unlikely to respond to trastuzumab-based therapy, other novel therapeutic targets needed to be considered.

Methods

HER2+ GC patients who were treated with trastuzumab in combination with either 5-fluorouracil/cisplatin or capecitabine/cisplatin were enrolled. Clinicopathologic features and molecular alterations of HER2, phosphoinositide 3-kinase regulatory subunit 1 (PIK3R1), and phosphatase and tensin homolog (PTEN) were correlated with treatment outcome. Factors predictive of resistance were also explored.

Novel betulin derivative induces anti-proliferative activity by G2/M phase cell cycle arrest and apoptosis in Huh7 cells

Betulin (BT) has been identified to exhibit potential benefits for treating hepatocellular carcinoma (HCC). The results of the present study demonstrated that a new semisynthetic derivative of BT, 3,28-di-(2-nitroxy-acetyl)-oxy-BT, may effectively decrease the viability of Huh7 cells. Mechanistic studies revealed that 3,28-di-(2-nitroxy-acetyl)-oxy-BT inhibited the transition between G₂ and M phase of the cell cycle by regulating cell cycle regulatory proteins. Additional study revealed that 3,28-di-(2-nitroxy-acetyl)-oxy-BT may trigger Huh7 cells to undergo caspase-dependent apoptosis as an increased proportion of cells were identified in the sub-G₁ phase, which may be a result of poly(ADP-ribose) polymerase cleavage and caspase activation. Furthermore, 3,28-di-(2-nitroxy-acetyl)-oxy-BT-induced apoptosis was mitochondrion-mediated. The results of the present study demonstrated that Bcl-2-associated X protein translocated to the mitochondria from the cytosol following 3,28-di-(2-nitroxy-acetyl)-oxy-BT treatment. Notably, the phosphoinositide 3-kinase/protein kinase B signaling pathway was involved in 3,28-di-(2-nitroxy-acetyl)-oxy-BT-treated Huh7 cells. Therefore, the results of the present study demonstrated that 3,28-di-(2-nitroxy-acetyl)-oxy-BT may inhibit HCC, which may be a possible application to treat HCC.

Ginsenoside Rh2 inhibits human A172 glioma cell proliferation and induces cell cycle arrest status via modulating Akt signaling pathway

Ginsenoside Rh2 (G-Rh2), the main bioactive component in American ginseng, is known to exert a wide variety of biological activities. Accumulating evidence suggests that G-Rh2 inhibits cell proliferation and induces apoptosis of tumor cells. However, the possible mechanism through which G-Rh2 exerts its action on malignant glioma cells have not been completely elucidated. The findings of the present study demonstrated that G-Rh2 decreased the viability of glioma cells in a dose- and time-dependent manner, and induced cell cycle arrest. G-Rh2-induced cell cycle arrest was accompanied by the downregulation of cyclin-dependent kinase 4 and Cyclin E. In addition, G-Rh2 markedly reduced the expression of total- RAC-α serine/threonine-protein kinase (Akt) and the levels of phosphorylated-Akt. These findings provide mechanistic details of how G-Rh2 acts on glioma cells and suggest that G-Rh2 may function as a potential anti-cancer drug for glioma treatment.

FOXO3 induces ubiquitylation of AKT through MUL1 regulation

AKT (also known as protein kinase B, PKB) plays an important role in cell survival or tumor progression. For these reasons, AKT is an emerging target for cancer therapeutics. Previously our studies showed that mitochondrial E3 ubiquitin protein ligase 1 (MUL1, also known as MULAN/GIDE/MAPL) is suppressed in head and neck cancer (HNC) and acts as negative regulator against AKT. However, the MUL1 regulatory mechanisms remain largely unknown. Here we report that cisplatin (CDDP) induces thyroid cancer cell death through MUL1-AKT axis. Specifically, CDDP-induced MUL1 leads to ubiquitylation of active form of AKT. We also observed that the role of forkhead box O3 (FOXO3) is pivotal in CDDP-induced MUL1 regulation. FOXO3 knock-downed cells show resistance against CDDP-mediated MUL1-AKT axis. CDDP-mediated intracellular ROS increment plays an important role in FOXO3-MUL1-AKT signal pathway. The data provide compelling evidence to support the idea that the regulation of FOXO3-MUL1-AKT axis can be a novel strategy for the treatment of HNC with CDDP.

Cisplatin triggers cancer stem cell enrichment in platinum-resistant cells through NF-κB-TNFα-PIK3CA loop

Background

Parallel to complex alteration in molecular and cellular events, enrichment of cancer stem cells (CSC) contributes significantly in deliberation and maintenance of cisplatin resistance. Cisplatin mediated CSC enrichment is well established in various cancers, yet the underlying mechanism is largely unknown. Cisplatin also promotes transcriptional upregulation of PIK3CA, hence activating PI3K/AKT signaling in resistant cells. However, such cisplatin-induced transcriptional regulators of PIK3CA and their impact on cancer stem cell population in resistant cells are largely unknown.

Methods

DNA-binding protein pulldown using PIK3CA promoter as bait followed by nLCMS was used to identify, cisplatin-induced potential transcriptional regulators of PIK3CA promoter. PIK3CA promoter activity was estimated by luciferase based reporter assay. ChIP was used to assess interaction of NF-κB with PIK3CA promoter. CSC-enriched side-population was sorted using DCV-dye exclusion methods. All the gene expression levels were assessed using qPCR.

Results

Using a transcription factor pull-down assay with PIK3CA promoter, we identified NF-κB as a prime regulator, which escalates both TNFα and PIK3CA expression only in CSC enriched side-population (SP) but not in non side-population (NSP) in platinum resistant ovarian cancer cells upon cisplatin treatment. This SP-specific NF-κB-TNFα-PIK3CA bi-modal loop, on one hand, maintains persistent activation of NF-κB through TNFα- NF-κB autocrine loop, while NF-κB-PIK3CA loop nurture CSC population under cisplatin treatment. Activation of PI3K/AKT signalling drives SP’s into an undifferentiated, anti-apoptotic stage through upregulating P21, P27,cFLIP expression. Contrarily, lack of active NF-κB-TNFα-PIK3CA loop makes NSPs vulnerable towards cisplatin and undergoes apoptosis. Altogether, cisplatin enriches cancer stem cells properties in SP fraction, which is evident from increased levels of pluripotency gene OCT4/SOX2/NANOG expression. Disruption of PIK3CA-NF-κB loop by Wortamannin reduces SP fraction by 1.4–1.6 fold in control and treated cells.

Conclusion

Together, our study signifies an active role of NF-κB-TNFα-PIK3CA bi-modal loop in cisplatin-mediated promotion and maintenance of CSC-like population in platinum-resistant cells.

Electronic supplementary material

The online version of this article (10.1186/s13046-017-0636-8) contains supplementary material, which is available to authorized users.

The role of paraoxonase in cancer

The paraoxonase (PON) gene family includes three proteins, PON1, PON2 and PON3. PON1 and PON3 are both associated with high-density lipoprotein (HDL) particles and exert anti-oxidant and anti-inflammatory properties. PON2 and PON3 are intracellular enzymes which modulate mitochondrial superoxide anion production and endoplasmic reticulum (ER) stress-induced apoptosis. The pleiotropic roles exerted by PONs have been mainly investigated in cardiovascular and neurodegenerative diseases. In recent years, overexpression of PON2 and PON3 has been observed in cancer cells and it has been proposed that both enzymes could be involved in tumor survival and stress resistance. Moreover, a lower activity of serum PON1 has been reported in cancer patients. This review summarizes literature data on the role of PONs in human cancers and their potential role as a target for antitumor drugs.

In-vitro and in-vivo combined effect of ARQ 092, an AKT inhibitor, with ARQ 087, a FGFR inhibitor

The PI3K/AKT pathway plays an important role in the initiation and progression of cancer, and the drug development efforts targeting this pathway with therapeutic interventions have been advanced by academic and industrial groups. However, the clinical outcome is moderate. Combination of inhibition of PI3K/AKT and other targeted agents became a feasible approach. In this study we assessed the combined effect of ARQ 092, a pan-AKT inhibitor, and ARQ 087, a pan-FGFR inhibitor, in vitro and in vivo. In a panel of 45 cancer cell lines, on 24% (11 out of 45) the compounds showed synergistic effect, on 62% (28 out of 45) additive, and on 13% (6 out of 45) antagonistic. The highest percentage of synergism was found on endometrial and ovarian cancer cell lines. Mutational analysis revealed that PIK3CA/PIK3R1 mutations and aberrant activation of FGFR2 predicted synergism, whereas Ras mutations showed a reverse correlation. Pathway analysis revealed that a combination of ARQ 092 and ARQ 087 enhanced the inhibition of both the AKT and FGFR pathways in cell lines in which synergistic effects were found (AN3CA and IGROV-1). Cell cycle arrest and apoptotic response occurred only in AN3CA cell, and was not seen in IGROV-1 cells. Furthermore, enhanced antitumor activity was observed in mouse models with endometrial cancer cell line and patient-derived tumors when ARQ 092 and ARQ 087 were combined. These results from in-vitro and in-vivo studies provide a strong rationale in treating endometrial and other cancers with the activated PI3K/AKT and FGFR pathways.

SGK1 Is a Critical Component of an AKT-Independent Pathway Essential for PI3K-Mediated Tumor Development and Maintenance

Activation of the PI3K-AKT signaling cascade is a common critical event during malignant transformation. In this study, we used thyroid gland epithelial cells and a series of genetically engineered mouse strains as model systems to demonstrate that, although necessary, AKT activation is not sufficient for PI3K-driven transformation. Instead, transformation requires the activity of the PDK1-regulated AGC family of protein kinases. In particular, SGK1 was found to be essential for proliferation and survival of thyroid cancer cells harboring PI3K-activating mutations. Notably, cotargeting SGK1 and AKT resulted in significantly higher growth suppression than inhibiting either PI3K or AKT alone. Overall, these findings underscore the clinical relevance of AKT-independent pathways in tumors driven by genetic lesions targeting the PI3K cascade. Cancer Res; 77(24); 6914-26. ©2017 AACR.

PTEN Regulates PI(3,4)P2 Signaling Downstream of Class I PI3K

The PI3K signaling pathway regulates cell growth and movement and is heavily mutated in cancer. Class I PI3Ks synthesize the lipid messenger PI(3,4,5)P₃. PI(3,4,5)P₃ can be dephosphorylated by 3- or 5-phosphatases, the latter producing PI(3,4)P₂. The PTEN tumor suppressor is thought to function primarily as a PI(3,4,5)P₃ 3-phosphatase, limiting activation of this pathway. Here we show that PTEN also functions as a PI(3,4)P₂ 3-phosphatase, both in vitro and in vivo. PTEN is a major PI(3,4)P₂ phosphatase in Mcf10a cytosol, and loss of PTEN and INPP4B, a known PI(3,4)P₂ 4-phosphatase, leads to synergistic accumulation of PI(3,4)P₂, which correlated with increased invadopodia in epidermal growth factor (EGF)-stimulated cells. PTEN deletion increased PI(3,4)P₂ levels in a mouse model of prostate cancer, and it inversely correlated with PI(3,4)P₂ levels across several EGF-stimulated prostate and breast cancer lines. These results point to a role for PI(3,4)P₂ in the phenotype caused by loss-of-function mutations or deletions in PTEN.

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PTEN is a PI(3,4)P₂ 3-phosphatase

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PTEN and INPP4B regulate PI(3,4)P₂ accumulation downstream of class I PI3K

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PTEN regulates PI(3,4)P₂-dependent activation of Akt and formation of invadopodia

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PI(3,4)P₂ signaling may play a role in the tumor suppressor function of PTEN

Cytological Assessments and Transcriptome Profiling Demonstrate that Evodiamine Inhibits Growth and Induces Apoptosis in a Renal Carcinoma Cell Line

Chinese medicines are an important source of secondary metabolites with excellent antitumour activity. Evodia rutaecarpa, from the family Rutaceae, exhibits antitumour activity. Evodiamine (EVO), which was isolated from the fruit of E. rutaecarpa, exhibits robust antitumour activity. However, the antitumour mechanism of EVO remains unclear. In this study, we assessed the growth-inhibiting effect of EVO on two renal carcinoma cell lines. We found that EVO could change the morphology and decrease the viability and proliferation of cells in a time- and concentration-dependent manner in vitro. In addition, transcriptome analysis indicated that EVO can modulate the transcriptome of Caki-1 cells. In total, 7,243 differentially expressed genes were found, among which 3,347 downregulated genes and 3,896 upregulated genes were mainly involved in cell migration, apoptosis, cell cycle, and DNA replication. Furthermore, we demonstrated that EVO can cause apoptosis, arrest cells in the G2/M phase, and regulate the expression of apoptosis- and cell cycle-related genes in Caki-1 cells. Our study reveals the anticancer effects of EVO using cellular and molecular data, and indicates the potential uses of this compound as a resource to characterize the antitumour mechanisms of E. rutaecarpa.

Human cytomegalovirus infection enhances cell proliferation, migration and upregulation of EMT markers in colorectal cancer-derived stem cell-like cells

Increasing evidence suggests a link between persistent human cytomegalovirus (HCMV) infection and cancer. Although the role of HCMV in cancer is still elusive, recent studies revealed the presence of HCMV nucleic acids and proteins in different cancer types such as glioblastoma, colorectal, breast, and prostate cancers, and neuroblastoma. Although HCMV may not be directly associated with the neoplastic transformation, the presence of HCMV DNA in the tumorous tissue has been associated with altered clinical outcomes in cancer patients. However, the mechanisms involved in the association between colorectal cancer (CRC) and HCMV are unclear. In this study, we investigated the influence of HCMV infection on CRC or their derived cells. Proliferation and migration assays revealed a high infection efficiency in CRC-derived HT29 and SW480 'stem-like' cells. After 24, 48 and 72 h of HCMV infection, both HT29 and SW480 parental and stem-like cells showed a significant increase in cell proliferation and viability (p<0.0001). Moreover, HCMV infection promoted cell migration. These results demonstrate a significant phenotypic alteration in the CRC cell line upon HCMV infection. Using epithelial to mesenchymal transition (EMT) assays, we demonstrated that the EMT markers and driver genes were upregulated during the virus infection. The WNT signaling pathway, which is associated with the proliferation and migration of CRC cells, was upregulated (6-fold) in HCMV-infected cells as compared to the non-infected cells at day 7 from infection.

Everolimus Plus Letrozole for Treatment of Patients With HR+, HER2- Advanced Breast Cancer Progressing on Endocrine Therapy: An Open-label, Phase II Trial

PURPOSE

In the Breast cancer trials of OraL EveROlimus-2 (BOLERO-2) trial, everolimus plus exemestane improved progression-free survival (PFS) in patients with hormone receptor-positive (HR⁺), human epidermal growth factor receptor 2-negative (HER2^-) advanced breast cancer (ABC) recurring or progressing on/after prior endocrine therapy (ET), suggesting that dual blockade using targeted therapy and ET was an effective treatment option. Here, we investigated the clinical benefit of combining everolimus with different endocrine partner, letrozole, in a similar patient population.

METHODS

In this phase II, open-label, single-arm, multicenter trial, postmenopausal women with HR⁺, HER2^- ABC who had recurrence/progression on/after prior ET received everolimus 10 mg daily and letrozole 2.5 mg daily. The primary end point was objective response rate; key secondary end points included disease-control rate, PFS, overall survival, and safety.

RESULTS

A total of 72 patients were enrolled and followed-up for a median duration of 11.4 months. Everolimus plus letrozole achieved an overall response rate of 23.3% (95% confidence interval [CI], 13.4%-36.0%). The median PFS was 8.8 months (95% CI, 6.6-11.0 months), and the overall survival was 22.9 months (95% CI, 18.5-28.9 months). Disease-control rate was achieved in 51 (85%) patients. The safety profile was consistent with previously published data: The most frequently reported any grade adverse events (AEs) were fatigue (61.1%), stomatitis (54.2%), and rash (33.4%). The most frequently reported grade 3 AEs were stomatitis and anemia (8.3% each), fatigue and diarrhea (5.6% each), and hyperglycemia (4.2%). Only 1 patient had grade 4 AE of anemia.

CONCLUSIONS

Everolimus plus letrozole demonstrated clinical benefit and could be a valid treatment option for postmenopausal women recurring/progressing on prior endocrine therapy.

NRF2-regulated metabolic gene signature as a prognostic biomarker in non-small cell lung cancer

Mutations in Kelch-like ECH-associated protein 1 (KEAP1) cause the aberrant activation of nuclear factor erythroid-derived 2-like 2 (NRF2), which leads to oncogenesis and drug resistance in lung cancer cells. Our study was designed to identify the genes involved in lung cancer progression targeted by NRF2. A series of microarray experiments in normal and cancer cells, as well as in animal models, have revealed regulatory genes downstream of NRF2 that are involved in wide variety of pathways. Specifically, we carried out individual and combinatorial microarray analysis of KEAP1 overexpression and NRF2 siRNA-knockdown in a KEAP1 mutant-A549 non-small cell lung cancer (NSCLC) cell line. As a result, we identified a list of genes which were mainly involved in metabolic functions in NSCLC by using functional annotation analysis. In addition, we carried out in silico analysis to characterize the antioxidant responsive element sequences in the promoter regions of known and putative NRF2-regulated metabolic genes. We further identified an NRF2-regulated metabolic gene signature (NRMGS) by correlating the microarray data with lung adenocarcinoma RNA-Seq gene expression data from The Cancer Genome Atlas followed by qRT-PCR validation, and finally showed that higher expression of the signature conferred a poor prognosis in 8 independent NSCLC cohorts. Our findings provide novel prognostic biomarkers for NSCLC.

Caveolin-1 Protects Retinal Ganglion Cells against Acute Ocular Hypertension Injury via Modulating Microglial Phenotypes and Distribution and Activating AKT pathway

Glaucoma, a group of eye diseases, causes gradual loss of retinal ganglion cells (RGCs) and ultimately results in irreversible blindness. Studies of the underlying mechanisms of glaucoma and clinical trial are far from satisfactory. Results from a genome-wide association study have suggested that the CAV1/CAV2 locus is associated with glaucoma, but this association and its potential underlying mechanisms need to be confirmed and further explored. Here, we studied the function of caveolin-1 (Cav1) in an acute ocular hypertension glaucoma model. Cav1 deficiency caused an aggregated lesion in the retina. In addition, treatment with cavtratin, a membrane permeable Cav1 scaffolding domain peptide, enhanced RGC survival. After cavtratin treatment, microglial numbers decreased significantly, and the majority of them migrated from the inner retinal layer to the outer retinal layers. Furthermore, cavtratin promoted a change in the microglia phenotype from the neurotoxic pro-inflammatory M1 to the neuroprotective anti-inflammatory M2. In a molecular mechanism experiment, we found that cavtratin activated the phosphorylation of both AKT and PTEN in cultured N9 cells. Our data highlights the neuroprotective effect of Cav1 on acute ocular hypertension and suggests that Cav1 may serve as a novel therapeutic target for the treatment of glaucoma. We further propose that cavtratin is a therapeutic candidate for glaucoma clinical trials.

Systems analysis of apoptotic priming in ovarian cancer identifies vulnerabilities and predictors of drug response

The lack of effective chemotherapies for high-grade serous ovarian cancers (HGS-OvCa) has motivated a search for alternative treatment strategies. Here, we present an unbiased systems-approach to interrogate a panel of 14 well-annotated HGS-OvCa patient-derived xenografts for sensitivity to PI3K and PI3K/mTOR inhibitors and uncover cell death vulnerabilities. Proteomic analysis reveals that PI3K/mTOR inhibition in HGS-OvCa patient-derived xenografts induces both pro-apoptotic and anti-apoptotic signaling responses that limit cell killing, but also primes cells for inhibitors of anti-apoptotic proteins. In-depth quantitative analysis of BCL-2 family proteins and other apoptotic regulators, together with computational modeling and selective anti-apoptotic protein inhibitors, uncovers new mechanistic details about apoptotic regulators that are predictive of drug sensitivity (BIM, caspase-3, BCL-X_L) and resistance (MCL-1, XIAP). Our systems-approach presents a strategy for systematic analysis of the mechanisms that limit effective tumor cell killing and the identification of apoptotic vulnerabilities to overcome drug resistance in ovarian and other cancers.High-grade serous ovarian cancers (HGS-OvCa) frequently develop chemotherapy resistance. Here, the authors through a systematic analysis of proteomic and drug response data of 14 HGS-OvCa PDXs demonstrate that targeting apoptosis regulators can improve response of these tumors to inhibitors of the PI3K/mTOR pathway.

Systems analysis of apoptotic priming in ovarian cancer identifies vulnerabilities and predictors of drug response

The lack of effective chemotherapies for high-grade serous ovarian cancers (HGS-OvCa) has motivated a search for alternative treatment strategies. Here, we present an unbiased systems-approach to interrogate a panel of 14 well-annotated HGS-OvCa patient-derived xenografts for sensitivity to PI3K and PI3K/mTOR inhibitors and uncover cell death vulnerabilities. Proteomic analysis reveals that PI3K/mTOR inhibition in HGS-OvCa patient-derived xenografts induces both pro-apoptotic and anti-apoptotic signaling responses that limit cell killing, but also primes cells for inhibitors of anti-apoptotic proteins. In-depth quantitative analysis of BCL-2 family proteins and other apoptotic regulators, together with computational modeling and selective anti-apoptotic protein inhibitors, uncovers new mechanistic details about apoptotic regulators that are predictive of drug sensitivity (BIM, caspase-3, BCL-X_L) and resistance (MCL-1, XIAP). Our systems-approach presents a strategy for systematic analysis of the mechanisms that limit effective tumor cell killing and the identification of apoptotic vulnerabilities to overcome drug resistance in ovarian and other cancers.

High-grade serous ovarian cancers (HGS-OvCa) frequently develop chemotherapy resistance. Here, the authors through a systematic analysis of proteomic and drug response data of 14 HGS-OvCa PDXs demonstrate that targeting apoptosis regulators can improve response of these tumors to inhibitors of the PI3K/mTOR pathway.

Systems analysis of apoptotic priming in ovarian cancer identifies vulnerabilities and predictors of drug response

The lack of effective chemotherapies for high-grade serous ovarian cancers (HGS-OvCa) has motivated a search for alternative treatment strategies. Here, we present an unbiased systems-approach to interrogate a panel of 14 well-annotated HGS-OvCa patient-derived xenografts for sensitivity to PI3K and PI3K/mTOR inhibitors and uncover cell death vulnerabilities. Proteomic analysis reveals that PI3K/mTOR inhibition in HGS-OvCa patient-derived xenografts induces both pro-apoptotic and anti-apoptotic signaling responses that limit cell killing, but also primes cells for inhibitors of anti-apoptotic proteins. In-depth quantitative analysis of BCL-2 family proteins and other apoptotic regulators, together with computational modeling and selective anti-apoptotic protein inhibitors, uncovers new mechanistic details about apoptotic regulators that are predictive of drug sensitivity (BIM, caspase-3, BCL-X_L) and resistance (MCL-1, XIAP). Our systems-approach presents a strategy for systematic analysis of the mechanisms that limit effective tumor cell killing and the identification of apoptotic vulnerabilities to overcome drug resistance in ovarian and other cancers.High-grade serous ovarian cancers (HGS-OvCa) frequently develop chemotherapy resistance. Here, the authors through a systematic analysis of proteomic and drug response data of 14 HGS-OvCa PDXs demonstrate that targeting apoptosis regulators can improve response of these tumors to inhibitors of the PI3K/mTOR pathway.

Characterization of a novel p110β-specific inhibitor BL140 that overcomes MDV3100-resistance in castration-resistant prostate cancer cells

BACKGROUND

Our previous studies demonstrated that the class IA PI3K/p110β is critical in castration-resistant progression of prostate cancer (CRPC) and that targeting prostate cancer with nanomicelle-loaded p110β-specific inhibitor TGX221 blocked xenograft tumor growth in nude mice, confirming the feasibility of p110β-targeted therapy for CRPCs. To improve TGX221's aqueous solubility, in this study, we characterized four recently synthesized TGX221 analogs.

METHODS

TGX221 analog efficacy were examined in multiple prostate cancer cell lines with the SRB cell growth assay, Western blot assay for AKT phosphorylation and cell cycle protein levels. Target engagement with PI3K isoforms was evaluated with cellular thermal shift assay. PI3K activity was determined with the Kinase-Glo Plus luminescent kinase assay. Cell cycle distribution was evaluated with flow cytometry after propidium iodide staining.

RESULTS

As expected, replacing either one of two major functional groups in TGX221 by more hydrophilic groups dramatically improved the aqueous solubility (about 40-fold) compared to TGX221. In the CETSA assay, all the analogs dramatically shifted the melting curve of p110β protein while none of them largely affected the melting curves of p110α, p110γ, or Akt proteins, indicating target-specific engagement of these analogs with p110β protein. However, functional evaluation showed that only one of the analogs BL140 ubiquitously inhibited AKT phosphorylation in all CRPC cell lines tested with diverse genetic abnormalities including AR, PTEN, and p53 status. BL140 was superior than GSK2636771 (IC50 5.74 vs 20.49 nM), the only p110β-selective inhibitor currently in clinical trials, as revealed in an in vitro Kinase-Glo assay. Furthermore, BL140 exhibited a stronger inhibitory effect than GSK2636771 on multiple CRPC cell lines including a MDV3100-resistant C4-2B cell subline, indicating BL140 elimination of MDV3100 resistance. Mechanistic studies revealed that BL140 blocked G1 phase cell cycle entry by reducing cyclin D1 but increasing p27kip1 protein levels.

CONCLUSION

These studies suggested that BL140 is a promising p110β-specific inhibitor with multiple superb properties than GSK2636771 worthy for further clinical development.

Role of Forkhead Box Class O proteins in cancer progression and metastasis

It is now widely accepted that several gene alterations including transcription factors are critically involved in cancer progression and metastasis. Forkhead Box Class O proteins (FoxOs) including FoxO1/FKHR, FoxO3/FKHRL1, FoxO4/AFX and FoxO6 transcription factors are known to play key roles in proliferation, apoptosis, metastasis, cell metabolism, aging and cancer biology through their phosphorylation, ubiquitination, acetylation and methylation. Though FoxOs are proved to be mainly regulated by upstream phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3 K)/Akt signaling pathway, the role of FoxOs in cancer progression and metastasis still remains unclear so far. Thus, with previous experimental evidences, the present review discussed the role of FoxOs in association with metastasis related molecules including cannabinoid receptor 1 (CNR1), Cdc25A/Cdk2, Src, serum and glucocorticoid inducible kinases (SGKs), CXCR4, E-cadherin, annexin A8 (ANXA8), Zinc finger E-box-binding homeobox 2 (ZEB2), human epidermal growth factor receptor 2 (HER2) and mRNAs such as miR-182, miR-135b, miR-499-5p, miR-1274a, miR-150, miR-34b/c and miR-622, subsequently analyzed the molecular mechanism of some natural compounds targeting FoxOs and finally suggested future research directions in cancer progression and metastasis.

De-escalation of treatment in HER2-positive breast cancer: Determinants of response and mechanisms of resistance

Overexpression and/or gene amplification of HER2, a crucial member of the HER family of four receptors, occur in about 15-20% of breast cancers and define an aggressive subtype of the disease. Activated HER homo and heterodimers govern a complex and redundant downstream signaling network that regulates cell survival and metastasis. Despite treatment with effective HER2-targeted therapies, many HER2-positive tumors fail to respond, or initially respond but eventually develop resistance. One of the upfront reasons for this treatment failure is failure to accurately select the tumors that are truly dependent on HER2 for survival and so would benefit the most from HER2-targeted therapy. In these truly HER2-addicted tumors (i.e. physiologically dependent), resistance could be the result of an incomplete inhibition of signaling at the HER receptor layer. In this regard, preclinical and clinical studies have documented the superiority of combination anti-HER2 therapy over single agent therapy to achieve a more comprehensive inhibition of the various HER receptor dimers. HER2 can be further activated or reactivated by mutations or other alterations in HER2 itself, or in other HER family members. Even when a complete and sustained HER inhibition is achieved, resistance to anti-HER therapy can arise by other somewhat dominant mechanisms, including preexisting or emerging alternative signaling pathways such as the estrogen receptor, deregulated downstream signaling components, especially of the PI3K pathway, and the tumor immune microenvironment. Most of the clinical trials that have investigated the efficacy of anti-HER2 therapies took place in the background of aggressive chemotherapy regimens, thus confounding the identification of key factors of resistance to the anti-HER2 treatments. Recent studies, however, have suggested that some HER2-amplified tumors may benefit from anti-HER2 therapy combined with only a single chemotherapy agent or in the absence of any chemotherapy. This de-escalation approach, a promising therapeutic strategy, is currently being explored in the clinic. In this review, we summarize the major molecular determinants that play a crucial role in influencing tumor response and resistance to HER2-targeted therapy, and discuss the growing need for patient stratification in order to facilitate the development of de-escalation strategies using HER2-targeted therapy alone with no chemotherapy.

Design, synthesis, and biological evaluation of novel 3-substituted imidazo[1,2-a]pyridine and quinazolin-4(3H)-one derivatives as PI3Kα inhibitors

Phosphatidylinositol 3-kinase (PI3K) is a pivotal regulator of intracellular signaling pathways and considered as a promising target in the development of a therapeutic treatment of cancer. Among the different PI3K subtypes, the PIK3CA gene encoding PI3K p110α is frequently mutated and overexpressed in majority of human cancers. Therefore, the inhibition of PI3Kα has been considered to be an efficient approach for the treatment of cancer. In this study, two series compounds containing hydrophilic group in imidazo[1,2-a]pyridine and quinazolin-4(3H)-one were synthesized and their antiproliferative activities against five cancer cell lines, including HCT-116, SK-HEP-1, MDA-MB-231, SNU638 and A549, were evaluated. Compound 1i with most potent antiproliferative activity was selected for further biological evaluation. PI3K kinase assay showed that 1i has selectivity for PI3Kα distinguished from other isoforms. The western blot assay indicated that 1i is more effective than HS-173, an imidazopyridine-based PI3Ka inhibitor, in reducing the levels of phospho-Akt. All these results suggested that 1i is a potent PI3Kα inhibitor and could be considered as a potential candidate for the development of anticancer agents.

The Wnt/β-catenin and PI3K/Akt signaling pathways promote EMT in gastric cancer by epigenetic regulation via H3 lysine 27 acetylation

In this study, we investigated the underlying mechanism of the phosphoinositide 3-kinase/Akt- and Wnt/β-catenin-mediated promotion of epithelial-to-mesenchymal transition by epigenetic regulation of histone acetylation in gastric cancer. First, we used immunohistochemistry to detect the expression of phosphorylated Akt, phosphorylated glycogen synthase kinase 3 beta, and β-catenin in gastric cancer tissues and adjacent tissues. In addition, we confirmed that the phosphoinositide 3-kinase/Akt and Wnt/β-catenin signaling pathways were correlated with tumorigenesis, progression, and maintenance of gastric cancer using the phosphoinositide 3-kinase inhibitor LY294002 and an inhibitor of the β-catenin/TCF4 complex, FH535. Epithelial-to-mesenchymal transition-related gene expression was measured by western blotting and quantitative real-time polymerase chain reaction assays. Furthermore, we detected the acetylation of histone H3 lysine 4 and lysine 27 using the FH535 and LY294002 inhibitors at different concentrations for 24 and 48 h. Finally, chromatin immunoprecipitation-quantitative polymerase chain reaction was performed to detect the specific binding of H3K27ac to the promoter of the epithelial-to-mesenchymal transition-related factor, Twist. Taken together, abnormal activation of the phosphoinositide 3-kinase/Akt and Wnt/β-catenin signaling pathway was correlated with the gastric cancer progression and contributed to epithelial-to-mesenchymal transition regulation by controlling histone acetylation.

A synthetic peptide hijacks the catalytic subunit of class I PI3K to suppress the growth of cancer cells

Activation of class I Phosphoinositide 3-kinases (PI3Ks) by mutation or overexpression closely correlates with the development of various human cancers. Class I PI3Ks are heterodimers composed of p110 catalytic subunits and regulatory subunits represented by p85. PAQR3 has been found to inhibit p110α activity by blocking its interaction with p85. In this study, we identified the N-terminal 6-55 amino acid residues of PAQR3 being sufficient for its interaction with p110α. A synthetic peptide, P6-55, that contains the N-terminus of PAQR3 could disrupt the interactions of p110α with both PAQR3 and p85. The activity of PI3K was also inhibited by P6-55, accompanied by significant inhibition of cancer cell proliferation. In a xenograft mouse model, P6-55 was able to reduce tumor growth in vivo. Furthermore, P6-55 was capable of inhibiting the elevated basal PI3K activity of H1047R, a hotspot mutation found in many types of human cancers. The cell proliferation and migration of cancer cells bearing H1047R mutation were also reduced by P6-55. In conclusion, our study provides a proof of concept that blocking the interaction of p110α with p85 by a peptide can serve as a new strategy to inhibit the oncogenic activity of PI3K in cancer therapy.

CENPH Inhibits Rapamycin Sensitivity by Regulating GOLPH3-dependent mTOR Signaling Pathway in Colorectal Cancer

Background: Centromere protein H (CENPH) is known as a fundamental component of the active centromere complex, and its overexpression is correlated with poor prognosis in various solid tumors. mTOR inhibitor rapamycin has been shown to possess antitumor activity, as well as prevent intestinal tumorigenesis. However, the prognostic value of CENPH in colorectal cancer (CRC) and the role of CENPH in rapamycin sensitivity remain unknown. Materials and methods: The effect of CENPH on the cell proliferation, clonogenicity, and cell response to rapamycin in CRC were evaluated by MTT and/or colony formation assays. For the underlying mechanisms, the interaction between CENPH and GOLPH3 were detected by co-immunoprecipitation, GST pull-down, and His-tag pull-down assays, as well as the laser scanning confocal microscopy. The status of kinases in mTOR signaling was determined by Western blot. Finally, the clinical significance of CENPH was analyzed using public CRC datasets with CENPH transcripts and clinical information. Results: CENPH inhibited CRC malignant phenotypes, conferred reduced sensitivity to rapamycin, and attenuated both mTORC1 and mTORC2 in mTOR signaling pathway through the interaction with golgi phosphoprotein 3 (GOLPH3), which has been identified as a potential oncogene and modulates the response to rapamycin. Moreover, elevated levels of CENPH were detected in CRC tissues, compared with normal colorectal tissues. High levels of CENPH expression gradually decreased according to CRC tumor stages. Patients with high CENPH expression had favorable survival. Conclusions: Our results suggest that CENPH inhibits rapamycin sensitivity by regulating GOLPH3 dependent mTOR pathway. High CENPH expression is associated with better prognosis in CRC patients. Taken together, CENPH may serve as a potential predictor for rapamycin sensitivity and therapeutic target for CRC patients.

Breast cancer suppression by aplysin is associated with inhibition of PI3K/AKT/FOXO3a pathway

Aplysin, a bromosesquiterpene isolated from Aplysia kurodai, was explored as a potential anti-breast cancer agent by us. However, the mechanisms underlying the anticarcinogenic effect of aplysin remain unclear. Here, aplysin was found to remarkably suppress tumor growth in vivo, inhibit cell proliferation and promote apoptosis in vitro. Additionally, we demonstrated that aplysin attained these effects in part by down-regulating PI3K/AKT/FOXO3a signaling pathway. Aplysin treatment inhibited the phosphorylation levels of AKT (Ser-473) and AKT-dependent phosphorylation of FOXO3a (Ser-253) in breast cancer cell lines and breast cancer tissues. The expression levels of FOXO3a-targeted genes were also destabilized by aplysin, cyclin D1 and Bcl-XL were declined; however, p21^CIP1, p27^KIP1, Bim, TRAIL and FasL were increased both in vivo and in vitro. Furthermore, activation of the PI3K/AKT signaling pathway by an activator and silencing of FOXO3a by shRNA protected the cells from aplysin mediated growth suppression and apoptosis. In summary, our findings revealed that aplysin could suppress breast cancer progression by inhibiting PI3K/AKT/FOXO3a pathway, thereby suggesting a potential role of aplysin as a chemoprevention drug for patients with breast cancer.

Marine Mollusk-Derived Agents with Antiproliferative Activity as Promising Anticancer Agents to Overcome Chemotherapy Resistance

The chemical investigation of marine mollusks has led to the isolation of a wide variety of bioactive metabolites, which evolved in marine organisms as favorable adaptations to survive in different environments. Most of them are derived from food sources, but they can be also biosynthesized de novo by the mollusks themselves, or produced by symbionts. Consequently, the isolated compounds cannot be strictly considered as "chemotaxonomic markers" for the different molluscan species. However, the chemical investigation of this phylum has provided many compounds of interest as potential anticancer drugs that assume particular importance in the light of the growing literature on cancer biology and chemotherapy. The current review highlights the diversity of chemical structures, mechanisms of action, and, most importantly, the potential of mollusk-derived metabolites as anticancer agents, including those biosynthesized by mollusks and those of dietary origin. After the discussion of dolastatins and kahalalides, compounds previously studied in clinical trials, the review covers potentially promising anticancer agents, which are grouped based on their structural type and include terpenes, steroids, peptides, polyketides and nitrogen-containing compounds. The "promise" of a mollusk-derived natural product as an anticancer agent is evaluated on the basis of its ability to target biological characteristics of cancer cells responsible for poor treatment outcomes. These characteristics include high antiproliferative potency against cancer cells in vitro, preferential inhibition of the proliferation of cancer cells over normal ones, mechanism of action via nonapoptotic signaling pathways, circumvention of multidrug resistance phenotype, and high activity in vivo, among others. The review also includes sections on the targeted delivery of mollusk-derived anticancer agents and solutions to their procurement in quantity.

Small molecules to the rescue: Inhibition of cytokine signaling in immune-mediated diseases

Cytokines are small, secreted proteins associated with the maintenance of immune homeostasis but also implicated with the pathogenesis of several autoimmune and inflammatory diseases. Biologic agents blocking cytokines or their receptors have revolutionized the treatment of such pathologies. Nonetheless, some patients fail to respond to these drugs or do not achieve complete remission. The signal transduction originating from membrane-bound cytokine receptors is an intricate network of events that lead to gene expression and ultimately regulate cellular functionality. Our understanding of the intracellular actions that molecules such as interleukins, interferons (IFNs) and tumor necrosis factor (TNF) set into motion has greatly increased in the past few years, making it possible to interfere with cytokines' signaling cascades. The Janus kinase (JAK)/signal transducer and activator of transcription (STAT), the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB), the mitogen activated protein kinase (MAPK) and the Phosphatidylinositol-3'-kinases (PI3K) pathways have all been intensively studied and key steps as well as molecules have been identified. These research efforts have led to the development of a new generation of small molecule inhibitors. Drugs capable of blocking JAK enzymatic activity or interfering with the proteasome-mediated degradation of intermediates in the NF-kB pathway have already entered the clinical arena confirming the validity of this approach. In this review, we have recapitulated the biochemical events downstream of cytokine receptors and discussed some of the drugs which have already been successfully utilized in the clinic. Moreover, we have highlighted some of the new molecules that are currently being developed for the treatment of immune-mediated pathologies and malignancies.

HOXB7 accelerates the malignant progression of hepatocellular carcinoma by promoting stemness and epithelial-mesenchymal transition

Background

Homeobox B7 (HOXB7) has been identified associated with poor prognosis of hepatocellular carcinoma (HCC). However, the specific mechanism by which HOXB7 promotes the malignant progression of HCC remains to be determined.

Methods

Immunohistochemistry (IHC) was used to detect the expression level of HOXB7 in 77-paired HCC tissue samples, and the correlation between HOXB7 and HCC prognosis was assessed. The location of HOXB7 was confirmed by immunofluorescence. Cell Titer-Blue assay was used to assess the proliferation of hepatoma cells. The stem-like properties of hepatoma cells were analysed by sphere formation and clone formation assays. The effect of HOXB7 on expression of cancer stem cell markers was evaluated. Transwell and wound-healing assays were performed to estimate the invasion and migration abilities of hepatoma cells. A xenograft tumor model was established in nude mice to assess the role of HOXB7 in tumor growth. Bioluminescence imaging was used to survey the effect of HOXB7 on the metastatic ability of hepatoma cells in vivo.

Results

Higher expression of HOXB7 was detected in HCC tissues compared with noncancerous tissues and significantly associated with poor prognosis of HCC. In addition, HOXB7 knockdown suppressed the cell proliferation, clone formation, sphere formation, invasion and migration of hepatoma cells in vitro; conversely, these biological abilities of hepatoma cells were enhanced by HOXB7 overexpression. Moreover, the cancer stem cell markers EPCAM and NANOG were up-regulated by HOXB7. The role of HOXB7 in promoting tumor growth and metastasis was verified in vivo. Further investigation revealed that c-Myc and Slug expression was elevated by HOXB7 and the AKT pathway was activated.

Conclusion

Overexpression of HOXB7 was significantly correlated with poor prognosis of HCC. HOXB7 up-regulated c-Myc and Slug expression via the AKT pathway to promote the acquisition of stem-like properties and facilitate epithelial-mesenchymal transition of hepatoma cells, accelerating the malignant progression of HCC.