MK-2206, an allosteric Akt inhibitor, enhances antitumor efficacy by standard chemotherapeutic agents or molecular targeted drugs in vitro and in vivo

Targeting Akt by SC66 triggers GSK-3β mediated apoptosis in colon cancer therapy

Background

Colon cancer is one of the three common malignant tumors, with lower 5 years survival rate. Akt is an important therapeutic target, while SC66 is a novel allosteric AKT inhibitor, which enhances the therapeutic effect in several types of cancer. However, the molecular mechanisms of targeting AKT by SC66 during colon cancer therapy are not well understood.

Methods

The biological role of GSK-3β in colon cancer growth suppression induced by SC66 was detected in vitro and in vivo. Hoechst 33342 and crystal violet staining were used to determine whether targeting AKT affected apoptosis and cell proliferation. The CCK8 assay was utilized to analyze cell viability. The expression levels of Akt, GSK-3β, Bax, Bcl-xL, p53 and PUMA were measured by immune blotting. Xenograft mouse model was established to study the antitumor effect of SC66 in vivo.

Results

Our results show that SC66 induced significantly colon cancer cell apoptosis, accompanied with Akt inactivation. After AKT inhibition, activated GSK-3β interacted with Bax directly, leading to Bax oligomerization and activation. Knocking down GSK-3β abrogated SC66-triggered Bax activation and apoptosis, which was enhanced by over-expressed GSK-3β. In addition, the expression level of Bcl-xL was down-regulated while p53 had no function during SC66-induced apoptosis. Furthermore, colon cancer growth was suppressed by SC66 therapy in vivo.

Conclusion

Taken together, these data indicated that the novel small molecule AKT inhibitor SC66 shows visible antitumor effects via the AKT/GSK-3β/Bax axis in vitro and in vivo. Our results provide a rational basis for the development of targeting-GSK-3β, which may serve as a potential biomarker and yield meaningful benefits for colon cancer patients in the future.

Rebound pathway overactivation by cancer cells following discontinuation of PI3K or mTOR inhibition promotes cancer cell growth

Whilst effects of anti-cancer drugs have been thoroughly explored, little is known about the repercussion of drug cessation. However, this has important clinical relevance since several clinical protocols such as intermittent drug scheduling lead to frequent drug discontinuation. In this study, we have thus investigated the consequences of withdrawal of agents that target the PI3K/AKT/mTOR signaling pathway in cancer cells. We report that washout of kinase inhibitors of mTOR or PI3K inhibitors led to a rapid and sustainable overactivation of AKT. Consequently, proliferation of tumor cells was significantly higher following drug washout in cancer cells that were pre-treated with mTOR or PI3K inhibitors compared to untreated cells. This effect was prevented by the addition of an AKT inhibitor following drug washout. Rebound AKT overactivation induced by mTOR or PI3K inhibitors discontinuation was mediated by IGF-1R, as demonstrated by its prevention in the presence of an IGF-1R inhibitor and by increased IGF-1R phosphorylation in treated cells versus control cells. Taken together, our results show that discontinuation of PI3K or mTOR inhibitors results in AKT overactivation that promotes tumor growth. They further highlight the benefit of adding an AKT inhibitor following cessation of PI3K or mTOR inhibitors.

Role of cytoplasmic lncRNAs in regulating cancer signaling pathways

Cancer remains a serious healthcare problem despite significant improvements in early detection and treatment approaches in the past few decades. Novel biomarkers for diagnosis and therapeutic strategies are urgently needed. In recent years, long noncoding RNAs (lncRNAs) have been reported to be aberrantly expressed in tumors and show crosstalk with key cancer-related signaling pathways. In this review, we summarized the current progress of research on cytoplasmic lncRNAs and their roles in regulating cancer signaling and tumor progression, further characterization of which may lead to effective approaches for cancer prevention and therapy.

Combination of eribulin plus AKT inhibitor evokes synergistic cytotoxicity in soft tissue sarcoma cells

An activated AKT pathway underlies the pathogenesis of soft tissue sarcoma (STS), with over-expressed phosphorylated AKT (p-AKT) correlating with a poor prognosis in a subset of STS cases. Recently, eribulin, a microtubule dynamics inhibitor, has demonstrated efficacy and is approved in patients with advanced/metastatic liposarcoma and breast cancer. However, mechanisms of eribulin resistance and/or insensitivity remain largely unknown. In this study, we demonstrated that an increased p-AKT level was associated with eribulin resistance in STS cells. We found a combination of eribulin with the AKT inhibitor, MK-2206, synergistically inhibited STS cell growth in vivo as well as in vitro. Mechanistically, eribulin plus MK-2206 induced G1 or G2/M arrest by down-regulating cyclin-dependent kinases, cyclins and cdc2, followed by caspase-dependent apoptosis in STS cells. Our findings demonstrate the significance of p-AKT signaling for eribulin-resistance in STS cells and provide a rationale for the development of an AKT inhibitor in combination with eribulin to treat patients with STS.

PLGA nanoparticle-based docetaxel/LY294002 drug delivery system enhances antitumor activities against gastric cancer

Docetaxel (TXT) is acknowledged as one of the most important chemotherapy agents for gastric cancer (GC). PI3K/AKT signaling is frequently activated in GC, and its inhibitor LY294002 exerts potent antitumor effects. However, the hydrophobicity of TXT and the poor solubility and low bioavailability of LY294002 limit their clinical application. To overcome these shortcomings, we developed poly(lactic acid/glycolic) (PLGA) nanoparticles loaded with TXT and LY294002. PLGA facilitated the accumulation of TXT and LY294002 at the tumor sites. The in vitro functional results showed that PLGA(TXT+LY294002) exhibited controlled-release and resulted in a markedly reduced proliferative capacity and an elevated apoptosis rate. An in vivo orthotopic GC mouse model and xenograft mouse model confirmed the anticancer superiority and tumor-targeting feature of PLGA(TXT+LY294002). Histological analysis indicated that PLGA(TXT+LY294002) was biocompatible and had no toxicity to major organs. Characterized by the combined slow release of TXT and LY294002, this novel PLGA-based TXT/LY294002 drug delivery system provides controlled release and tumor targeting and is safe, shedding light on the future of targeted therapy against GC.

Elucidating the transcriptional program of feline injection-site sarcoma using a cross-species mRNA-sequencing approach

BACKGROUND

Feline injection-site sarcoma (FISS), an aggressive iatrogenic subcutaneous malignancy, is challenging to manage clinically and little is known about the molecular basis of its pathogenesis. Tumor transcriptome profiling has proved valuable for gaining insights into the molecular basis of cancers and for identifying new therapeutic targets. Here, we report the first study of the FISS transcriptome and the first cross-species comparison of the FISS transcriptome with those of anatomically similar soft-tissue sarcomas in dogs and humans.

METHODS

Using high-throughput short-read paired-end sequencing, we comparatively profiled FISS tumors vs. normal tissue samples as well as cultured FISS-derived cell lines vs. skin-derived fibroblasts. We analyzed the mRNA-seq data to compare cancer/normal gene expression level, identify biological processes and molecular pathways that are associated with the pathogenesis of FISS, and identify multimegabase genomic regions of potential somatic copy number alteration (SCNA) in FISS. We additionally conducted cross-species analyses to compare the transcriptome of FISS to those of soft-tissue sarcomas in dogs and humans, at the level of cancer/normal gene expression ratios.

RESULTS

We found: (1) substantial differential expression biases in feline orthologs of human oncogenes and tumor suppressor genes suggesting conserved functions in FISS; (2) a genomic region with recurrent SCNA in human sarcomas that is syntenic to a feline genomic region of probable SCNA in FISS; and (3) significant overlap of the pattern of transcriptional alterations in FISS with the patterns of transcriptional alterations in soft-tissue sarcomas in humans and in dogs. We demonstrated that a protein, BarH-like homeobox 1 (BARX1), has increased expression in FISS cells at the protein level. We identified 11 drugs and four target proteins as potential new therapies for FISS, and validated that one of them (GSK-1059615) inhibits growth of FISS-derived cells in vitro.

CONCLUSIONS

(1) Window-based analysis of mRNA-seq data can uncover SCNAs. (2) The transcriptome of FISS-derived cells is highly consistent with that of FISS tumors. (3) FISS is highly similar to soft-tissue sarcomas in dogs and humans, at the level of gene expression. This work underscores the potential utility of comparative oncology in improving understanding and treatment of FISS.

Transforming growth factor-β (TGF-β)-induced up-regulation of TGF-β receptors at the cell surface amplifies the TGF-β response

Functional activation of the transforming growth factor-β (TGF-β) receptors (TGFBRs) is carefully regulated through integration of post-translational modifications, spatial regulation at the cellular level, and TGFBR availability at the cell surface. Although the bulk of TGFBRs resides inside the cells, AKT Ser/Thr kinase (AKT) activation in response to insulin or other growth factors rapidly induces transport of TGFBRs to the cell surface, thereby increasing the cell's responsiveness to TGF-β. We now demonstrate that TGF-β itself induces a rapid translocation of its own receptors to the cell surface and thus amplifies its own response. This mechanism of response amplification, which hitherto has not been reported for other cell-surface receptors, depended on AKT activation and TGF-β type I receptor kinase. In addition to an increase in cell-surface TGFBR levels, TGF-β treatment promoted TGFBR internalization, suggesting an overall amplification of TGFBR cycling. The TGF-β-induced increase in receptor presentation at the cell surface amplified TGF-β-induced SMAD family member (SMAD) activation and gene expression. Furthermore, bone morphogenetic protein 4 (BMP-4), which also induces AKT activation, increased TGFBR levels at the cell surface, leading to enhanced autocrine activation of TGF-β-responsive SMADs and gene expression, providing context for the activation of TGF-β signaling in response to BMP during development. In summary, our results indicate that TGF-β- and BMP-induced activation of low levels of cell surface-associated TGFBRs rapidly mobilizes additional TGFBRs from intracellular stores to the cell surface, increasing the abundance of cell-surface TGFBRs and cells' responsiveness to TGF-β signaling.

Differential effects of the Akt inhibitor MK-2206 on migration and radiation sensitivity of glioblastoma cells

Background

Most tumor cells show aberrantly activated Akt which leads to increased cell survival and resistance to cancer radiotherapy. Therefore, targeting Akt can be a promising strategy for radiosensitization. Here, we explore the impact of the Akt inhibitor MK-2206 alone and in combination with the dual PI3K and mTOR inhibitor PI-103 on the radiation sensitivity of glioblastoma cells. In addition, we examine migration of drug-treated cells.

Methods

Using single-cell tracking and wound healing migration tests, colony-forming assay, Western blotting, flow cytometry and electrorotation we examined the effects of MK-2206 and PI-103 and/or irradiation on the migration, radiation sensitivity, expression of several marker proteins, DNA damage, cell cycle progression and the plasma membrane properties in two glioblastoma (DK-MG and SNB19) cell lines, previously shown to differ markedly in their migratory behavior and response to PI3K/mTOR inhibition.

Results

We found that MK-2206 strongly reduces the migration of DK-MG but only moderately reduces the migration of SNB19 cells. Surprisingly, MK-2206 did not cause radiosensitization, but even increased colony-forming ability after irradiation. Moreover, MK-2206 did not enhance the radiosensitizing effect of PI-103. The results appear to contradict the strong depletion of p-Akt in MK-2206-treated cells. Possible reasons for the radioresistance of MK-2206-treated cells could be unaltered or in case of SNB19 cells even increased levels of p-mTOR and p-S6, as compared to the reduced expression of these proteins in PI-103-treated samples. We also found that MK-2206 did not enhance IR-induced DNA damage, neither did it cause cell cycle distortion, nor apoptosis nor excessive autophagy.

Conclusions

Our study provides proof that MK-2206 can effectively inhibit the expression of Akt in two glioblastoma cell lines. However, due to an aberrant activation of mTOR in response to Akt inhibition in PTEN mutated cells, the therapeutic window needs to be carefully defined, or a combination of Akt and mTOR inhibitors should be considered.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5517-4) contains supplementary material, which is available to authorized users.

Rho-kinase inhibition has antidepressant-like efficacy and expedites dendritic spine pruning in adolescent mice

Adolescence represents a critical period of neurodevelopment, defined by structural and synaptic pruning within the prefrontal cortex. While characteristic of typical development, this structural instability may open a window of vulnerability to developing neuropsychiatric disorders, including depression. Thus, therapeutic interventions that support or expedite neural remodeling in adolescence may be advantageous. Here, we inhibited the neuronally-expressed cytoskeletal regulatory factor Rho-kinase (ROCK), focusing primarily on the clinically-viable ROCK inhibitor fasudil. ROCK inhibition had rapid antidepressant-like effects in adolescent mice, and its efficacy was comparable to ketamine and fluoxetine. It also modified levels of the antidepressant-related signaling factors, tropomyosin/tyrosine receptor kinase B and Akt, as well as the postsynaptic marker PSD-95, in the ventromedial prefrontal cortex (vmPFC). Meanwhile, adolescent-typical dendritic spine pruning on excitatory pyramidal neurons in the vmPFC was expedited. Further, vmPFC-specific shRNA-mediated reduction of ROCK2, the dominant ROCK isoform in the brain, had antidepressant-like consequences. We cautiously suggest that ROCK inhibitors may have therapeutic potential for adolescent-onset depression.

The PI3K and MAPK/p38 pathways control stress granule assembly in a hierarchical manner

PI3K and p38 act in a hierarchical manner to enhance mTORC1 activity and stress granule formation; although PI3K is the main driver, the impact of p38 gets apparent as PI3K activity declines.

All cells and organisms exhibit stress-coping mechanisms to ensure survival. Cytoplasmic protein-RNA assemblies termed stress granules are increasingly recognized to promote cellular survival under stress. Thus, they might represent tumor vulnerabilities that are currently poorly explored. The translation-inhibitory eIF2α kinases are established as main drivers of stress granule assembly. Using a systems approach, we identify the translation enhancers PI3K and MAPK/p38 as pro-stress-granule-kinases. They act through the metabolic master regulator mammalian target of rapamycin complex 1 (mTORC1) to promote stress granule assembly. When highly active, PI3K is the main driver of stress granules; however, the impact of p38 becomes apparent as PI3K activity declines. PI3K and p38 thus act in a hierarchical manner to drive mTORC1 activity and stress granule assembly. Of note, this signaling hierarchy is also present in human breast cancer tissue. Importantly, only the recognition of the PI3K-p38 hierarchy under stress enabled the discovery of p38’s role in stress granule formation. In summary, we assign a new pro-survival function to the key oncogenic kinases PI3K and p38, as they hierarchically promote stress granule formation.

AKT drives SOX2 overexpression and cancer cell stemness in esophageal cancer by protecting SOX2 from UBR5-mediated degradation

As a transcription factor critical for embryonic and adult stem cell self-renewal and function, SOX2 gene amplification has been recognized as a driving factor for various cancers including esophageal cancer. SOX2 overexpression occurs more broadly in cancer than gene amplification, but the mechanism is poorly understood. Here we showed that in esophageal cancer cell lines the levels of SOX2 proteins are not directly correlated to the copy numbers of SOX2 genes and are strongly influenced by proteostasis. We showed that AKT is a major determinant for SOX2 overexpression and does so by protecting SOX2 from ubiquitin-dependent protein degradation. We identified UBR5 as a major ubiquitin E3 ligase that induces SOX2 degradation through ubiquitinating SOX2 at lysine 115. Phosphorylation of SOX2 at threonine 116 by AKT inhibits the interaction of UBR5 with SOX2 and thus stabilizes SOX2. We provided evidence that AKT inhibitor can effectively downregulate SOX2 and suppress esopheageal cancer cell proliferation and stemness. Taken together, our study provides new insight into the mechanism of SOX2 overexpression in cancer and evidence for targeting AKT as a potential therapeutic strategy for SOX2-positive cancers.

Oncogenic role of ABHD5 in endometrial cancer

Background

Abhydrolase domain containing 5 (ABHD5) functions as a tumor suppressor in colorectal and prostate cancers. The aim of this study was to investigate the roles of ABHD5 in endometrial cancer.

Materials and methods

ABHD5 expression was detected in clinical samples by immunohistochemical staining. Cell proliferation and invasion were evaluated with the Cell Counting Kit-8 and Transwell assay, respectively. Western blotting was performed to analyze protein expression. Glucose uptake was assessed by 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose. Lactate production was detected by a lactate assay kit.

Results

In the present study, ABHD5 was overexpressed in endometrial cancer tissues, and its expression was closely correlated with the International Federation of Gynecology and Obstetrics (FIGO) stage and lymph node metastasis. In addition, we observed that the knockdown of ABHD5 inhibited cell proliferation, invasion, glucose uptake and lactate production in HEC-1A cells, which expressed high levels of ABHD5. Conversely, the opposite effects were observed when ABHD5 was ectopically expressed in Ishikawa cells, which had low levels of ABHD5. Furthermore, the changes in glycolysis regulators (enolase 1 [ENO1], glucose transporter 1 [GLUT1] and lactate dehydrogenase A [LDHA]) and epithelial-to-mesenchymal transition-related proteins (E-cadherin and Snail) in HEC-1A cells with ABHD5 knockdown were consistent with the effects of ABHD5 on glycolysis and cell invasion. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) was increased, while the phosphorylated AKT (p-AKT) was decreased when ABHD5 was downregulated. Notably, treatment with the allosteric AKT inhibitor MK-2206 completely abolished the effects caused by ABHD5 overexpression in Ishikawa cells. Finally, ABHD5 knockdown potently suppressed tumor growth in vivo.

Conclusion

Overall, these results suggest that ABHD5 may play an oncogenic role in endometrial cancer via the AKT pathway.

Dual inhibition of AKT-mTOR and AR signaling by targeting HDAC3 in PTEN- or SPOP-mutated prostate cancer

AKT‐mTOR and androgen receptor (AR) signaling pathways are aberrantly activated in prostate cancer due to frequent PTEN deletions or SPOP mutations. A clinical barrier is that targeting one of them often activates the other. Here, we demonstrate that HDAC3 augments AKT phosphorylation in prostate cancer cells and its overexpression correlates with AKT phosphorylation in patient samples. HDAC3 facilitates lysine‐63‐chain polyubiquitination and phosphorylation of AKT, and this effect is mediated by AKT deacetylation at lysine 14 and 20 residues and HDAC3 interaction with the scaffold protein APPL1. Conditional homozygous deletion of Hdac3 suppresses prostate tumorigenesis and progression by concomitant blockade of AKT and AR signaling in the Pten knockout mouse model. Pharmacological inhibition of HDAC3 using a selective HDAC3 inhibitor RGFP966 inhibits growth of both PTEN‐deficient and SPOP‐mutated prostate cancer cells in culture, patient‐derived organoids and xenografts in mice. Our study identifies HDAC3 as a common upstream activator of AKT and AR signaling and reveals that dual inhibition of AKT and AR pathways is achievable by single‐agent targeting of HDAC3 in prostate cancer.

AKT as a Therapeutic Target for Cancer

Many cellular processes in cancer are attributed to kinase signaling networks. V-akt murine thymoma viral oncogene homolog (AKT) plays a major role in the PI3K/AKT signaling pathways. AKT is activated by PI3K or phosphoinositide-dependent kinases (PDK) as well as growth factors, inflammation, and DNA damage. Signal transduction occurs through downstream effectors such as mTOR, glycogen synthase kinase 3 beta (GSK3β), or forkhead box protein O1 (FOXO1). The abnormal overexpression or activation of AKT has been observed in many cancers, including ovarian, lung, and pancreatic cancers, and is associated with increased cancer cell proliferation and survival. Therefore, targeting AKT could provide an important approach for cancer prevention and therapy. In this review, we discuss the rationale for targeting AKT and also provide details regarding synthetic and natural AKT-targeting compounds and their associated studies.

Targeting mTOR in Acute Lymphoblastic Leukemia

Acute Lymphoblastic Leukemia (ALL) is an aggressive hematologic disorder and constitutes approximately 25% of cancer diagnoses among children and teenagers. Pediatric patients have a favourable prognosis, with 5-years overall survival rates near 90%, while adult ALL still correlates with poorer survival. However, during the past few decades, the therapeutic outcome of adult ALL was significantly ameliorated, mainly due to intensive pediatric-based protocols of chemotherapy. Mammalian (or mechanistic) target of rapamycin (mTOR) is a conserved serine/threonine kinase belonging to the phosphatidylinositol 3-kinase (PI3K)-related kinase family (PIKK) and resides in two distinct signalling complexes named mTORC1, involved in mRNA translation and protein synthesis and mTORC2 that controls cell survival and migration. Moreover, both complexes are remarkably involved in metabolism regulation. Growing evidence reports that mTOR dysregulation is related to metastatic potential, cell proliferation and angiogenesis and given that PI3K/Akt/mTOR network activation is often associated with poor prognosis and chemoresistance in ALL, there is a constant need to discover novel inhibitors for ALL treatment. Here, the current knowledge of mTOR signalling and the development of anti-mTOR compounds are documented, reporting the most relevant results from both preclinical and clinical studies in ALL that have contributed significantly into their efficacy or failure.

Repression of Human Papillomavirus Oncogene Expression under Hypoxia Is Mediated by PI3K/mTORC2/AKT Signaling

Oncogenic HPV types are major human carcinogens. Under hypoxia, HPV-positive cancer cells can repress the viral E6/E7 oncogenes and induce a reversible growth arrest. This response could contribute to therapy resistance, immune evasion, and tumor recurrence upon reoxygenation. Here, we uncover evidence that HPV oncogene repression is mediated by hypoxia-induced activation of canonical PI3K/mTORC2/AKT signaling. AKT-dependent downregulation of E6/E7 is only observed under hypoxia and occurs, at least in part, at the transcriptional level. Quantitative proteome analyses identify additional factors as candidates to be involved in AKT-dependent E6/E7 repression and/or hypoxic PI3K/mTORC2/AKT activation. These results connect PI3K/mTORC2/AKT signaling with HPV oncogene regulation, providing new mechanistic insights into the cross talk between oncogenic HPVs and their host cells.

Hypoxia is linked to therapeutic resistance and poor clinical prognosis for many tumor entities, including human papillomavirus (HPV)-positive cancers. Notably, HPV-positive cancer cells can induce a dormant state under hypoxia, characterized by a reversible growth arrest and strong repression of viral E6/E7 oncogene expression, which could contribute to therapy resistance, immune evasion and tumor recurrence. The present work aimed to gain mechanistic insights into the pathway(s) underlying HPV oncogene repression under hypoxia. We show that E6/E7 downregulation is mediated by hypoxia-induced stimulation of AKT signaling. Ablating AKT function in hypoxic HPV-positive cancer cells by using chemical inhibitors efficiently counteracts E6/E7 repression. Isoform-specific activation or downregulation of AKT1 and AKT2 reveals that both AKT isoforms contribute to hypoxic E6/E7 repression and act in a functionally redundant manner. Hypoxic AKT activation and consecutive E6/E7 repression is dependent on the activities of the canonical upstream AKT regulators phosphoinositide 3-kinase (PI3K) and mechanistic target of rapamycin (mTOR) complex 2 (mTORC2). Hypoxic downregulation of E6/E7 occurs, at least in part, at the transcriptional level. Modulation of E6/E7 expression by the PI3K/mTORC2/AKT cascade is hypoxia specific and not observed in normoxic HPV-positive cancer cells. Quantitative proteome analyses identify additional factors as candidates to be involved in hypoxia-induced activation of the PI3K/mTORC2/AKT signaling cascade and in the AKT-dependent repression of the E6/E7 oncogenes under hypoxia. Collectively, these data uncover a functional key role of the PI3K/mTORC2/AKT signaling cascade for viral oncogene repression in hypoxic HPV-positive cancer cells and provide new insights into the poorly understood cross talk between oncogenic HPVs and their host cells under hypoxia.

Inhibition of gastric cancer cell growth by a PI3K-mTOR dual inhibitor GSK1059615

Gastric cancer (GC) is a common malignancy. Developing novel and efficient anti-GC agents is urgent. GSK1059615 is a PI3K (phosphatidylinositol 3-kinase) and mTOR (mammalian target of rapamycin) dual inhibitor. It activity in human GC cells is tested here. In AGS cells and primary human GC cells, GSK1059615 potently inhibited cell growth, survival, proliferation and cell cycle progression. Further, significant apoptosis activation was detected in GSK1059615-treated GC cells. Contrarily in the primary human gastric epithelial cells, GSK1059615 failed to induce significant cytotoxicity and apoptosis. GSK1059615 blocked PI3K-AKT-mTOR cascade activation, inducing microRNA-9 downregulation but LMX1A (LIM homeobox transcription factor 1α) upregulation in GC cells. Significantly, GSK1059615 administration (i.p., daily, at 10 or 30 mg/kg) in nude mice potently inhibited subcutaneous AGS xenograft growth. AKT-mTOR inhibition and LMX1A upregulation were detected in AGS xenograft tissues with GSK1059615 administration. Together, we conclude that GSK1059615 inhibits GC cell growth in vitro and in vivo.

Targeting allosteric site of AKT by 5,7-dimethoxy-1,4-phenanthrenequinone suppresses neutrophilic inflammation

BACKGROUND

Acute lung injury (ALI) is a severe life-threatening inflammatory disease. Neutrophil activation is a major pathogenic factor in ALI. Protein kinase B (PKB)/AKT regulates diverse cellular responses, but the significance in neutrophilic inflammation and ALI remains unknown.

METHODS

Human neutrophils and neutrophil-like differentiated HL-60 (dHL-60) cells were used to examine the anti-inflammatory effects of 5,7-dimethoxy-1,4-phenanthrenequinone (CLLV-1). The therapeutic potential of CLLV-1 was determined in a mouse model of lipopolysaccharide (LPS)-induced ALI.

FINDINGS

CLLV-1 inhibited respiratory burst, degranulation, adhesion, and chemotaxis in human neutrophils and dHL-60 cells. CLLV-1 inhibited the phosphorylation of AKT (Thr308 and Ser473), but not of ERK, JNK, or p38. Furthermore, CLLV-1 blocked AKT activity and covalently reacted with AKT Cys310 in vitro. The AKT_309-313 peptide-CLLV-1 adducts were determined by NMR or mass spectrometry assay. The alkylation agent-conjugated AKT (reduced form) level was also inhibited by CLLV-1. Significantly, CLLV-1 ameliorated LPS-induced ALI, neutrophil infiltration, and AKT activation in mice.

INTERPRETATION

Our results identify CLLV-1 as a covalent allosteric AKT inhibitor by targeting AKT Cys310. CLLV-1 shows potent anti-inflammatory activity in human neutrophils and LPS-induced mouse ALI. Our findings provide a mechanistic framework for redox modification of AKT that may serve as a novel pharmacological target to alleviate neutrophilic inflammation.

Systemic analysis of tyrosine kinase signaling reveals a common adaptive response program in a HER2-positive breast cancer

Drug-induced compensatory signaling and subsequent rewiring of the signaling pathways that support cell proliferation and survival promote the development of acquired drug resistance in tumors. Here, we sought to analyze the adaptive kinase response in cancer cells after distinct treatment with agents targeting human epidermal growth factor receptor 2 (HER2), specifically those that induce either only temporary cell cycle arrest or, alternatively, apoptosis in HER2-overexpressing cancers. We compared trastuzumab, ARRY380, the combination thereof, and a biparatopic, HER2-targeted designed ankyrin repeat protein (DARPin; specifically, 6L1G) and quantified the phosphoproteome by isobaric tagging using tandem mass tag liquid chromatography/tandem mass spectrometry (TMT LC-MS/MS). We found a specific signature of persistently phosphorylated tyrosine peptides after the nonapoptotic treatments, which we used to distinguish between different treatment-induced cancer cell fates. Next, we analyzed the activation of serine/threonine and tyrosine kinases after treatment using a bait peptide chip array and predicted the corresponding active kinases. Through a combined system-wide analysis, we identified a common adaptive kinase response program that involved the activation of focal adhesion kinase 1 (FAK1), protein kinase C-δ (PRKCD), and Ephrin (EPH) family receptors. These findings reveal potential targets to prevent adaptive resistance to HER2-targeted therapies.

Hepatitis B virus X reduces hepatocyte apoptosis and promotes cell cycle progression through the Akt/mTOR pathway in vivo

Hepatitis B virus X (HBx), a viral onco-protein encoded by HBV, can promote oncogenesis of HCC. However, the mechanism of HBx in hepatocarcinogenesis is still unclear. In this study, we establish a new mouse model with normal immune system to investigate the role of HBx and its functional mechanisms under normal immune function. The animal model was established by injecting HBx-EGFP-14-19 cells into the hepatic portal vein of KM mice. To verify the mouse model, the expression of HBx in the liver tissue of mice was detected by qRT-PCR, western blotting and immunohistochemistry. The apoptosis index was calculated using the terminal deoxynucleotidyl transferase-dUTP nick-end labeling (TUNEL) assay, and the expression levels of apoptosis-related and cell cycle-related factors were measured. Moreover, expression of proteins in the protein kinase B/mammalian target of rapamycin (Akt/mTOR) signaling pathway was detected in HBx-EGFP-14-19 mice with and without use of an Akt inhibitor. The results showed the HBx was successfully overexpressed in liver of KM mice. After overexpressing HBx, the apoptosis index was downregulated in HBx-EGFP-14-19 liver tissue, and the expression levels of caspase-9 and Bad were reduced, but Bcl-xl was increased in HBx-EGFP-14-19 liver tissue. Overexpression of HBx increased the expression of the cyclin-dependent kinase 2 (CDK2), cyclinD1 and cyclinE. Moreover, compared with the low-level HBx group, p-Akt and p-mTOR were increased in the livers of mice with high levels of HBx. However, inactivation of apoptosis by overexpression of HBx was abolished by the treatment with an Akt inhibitor. These results indicate that HBx can induce anti-apoptosis mechanisms in hepatocytes in vivo, which is mediated by the Akt/mTOR signaling pathway.

Allosteric Small-Molecule Serine/Threonine Kinase Inhibitors

Deregulation of protein kinase activity has been linked to many diseases ranging from cancer to AIDS and neurodegenerative diseases. Not surprisingly, drugging the human kinome - the complete set of kinases encoded by the human genome - has been one of the major drug discovery pipelines. Majority of the approved clinical kinase inhibitors target the ATP binding site of kinases. However, the remarkable sequence and structural similarity of ATP binding pockets of kinases make selective inhibition of kinases a daunting task. To circumvent these issues, allosteric inhibitors that target sites other than the orthosteric ATP binding pocket have been developed. The structural diversity of the allosteric sites allows these inhibitors to have higher selectivity, lower toxicity and improved physiochemical properties and overcome drug resistance associated with the use of conventional kinase inhibitors. In this chapter, we will focus on the allosteric inhibitors of selected serine/threonine kinases, outline the benefits of using these inhibitors and discuss the challenges and future opportunities.

Fluctuation correlations as major determinants of structure- and dynamics-driven allosteric effects

Both structure- and dynamics-driven allosteric effects are determined by the correlation of distance fluctuations in proteins.

Adjuvant therapy with stattic enriches the anti-proliferative effect of doxorubicin in human ZR-75-1 breast cancer cells via arresting cell cycle and inducing apoptosis

Adjuvant therapy with novel and effective component has been presented as a contrivance in breast cancer treatment versus the conventional methods. The current research was done to evaluate the implement of stattic, specific STAT3 inhibitor on the anti-proliferative and apoptotic behavior of doxorubicin on ZR-75-1 breast cancer cells. Cell viability was investigated by MTT assay, the percentage of apoptosis by DAPI staining, and Annexin V. Real Time-PCR was applied to find out the correlation between mechanistic roles of the STAT3 pathway and apoptotic signal in the modulation of Bcl-2 and Bax gene expressions axis. The IC50 values for doxorubicin and stattic were 2.5 ± 0.18 μM and 3.5 ± 0.28 μM, respectively. Combination index (CI) value for ZR-75-1 breast cancer was 0.72, which indicated a strong synergistic effect. Incubation of the cells with a combination of stattic and doxorubicin revealed a significant increase in growth inhibitory effect of doxorubicin with more than 50% decrease in proliferation rate and a two-fold increase in the percentage of apoptotic cells. Assessment of gene expression levels demonstrated a visible decrease in antiapoptotic Bcl-2 and Bcl-xl accompanied by an increase in pro-apoptotic Bax mRNA levels (p < 0.05). Taken together, our results show that combination of a STAT3 inhibitor and doxorubicin can be figured out as a promising approach for dealing of patients with breast cancers.

The Molecular and Clinical Landscape of Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors are rare tumors of the pancreas originating from the islets of the Langerhans. These tumors comprise 1% to 3% of all newly diagnosed pancreatic cancers every year and have a unique heterogeneity in clinical presentation. Whole-genome sequencing has led to an increased understanding of the molecular biology of these tumors. In this review, we will summarize the current knowledge of the signaling pathways involved in the tumorigenesis of pancreatic neuroendocrine tumors as well as the major studies targeting these pathways at preclinical and clinical levels.

Allosteric Regulation of Protein Kinases Downstream of PI3-Kinase Signalling

Allostery is a basic principle that enables proteins to process and transmit cellular information. Protein kinases evolved allosteric mechanisms to transduce cellular signals to downstream signalling components or effector molecules. Protein kinases catalyse the transfer of the terminal phosphate from ATP to protein substrates upon specific stimuli. Protein kinases are targets for the development of small molecule inhibitors for the treatment of human diseases. Drug development has focussed on ATP-binding site, while there is increase interest in the development of drugs targeting alternative sites, i.e. allosteric sites. Here, we review the mechanism of regulation of protein kinases, which often involve the allosteric modulation of the ATP-binding site, enhancing or inhibiting activity. We exemplify the molecular mechanism of allostery in protein kinases downstream of PI3-kinase signalling with a focus on phosphoinositide-dependent protein kinase 1 (PDK1), a model kinase where small compounds can allosterically modulate the conformation of the kinase bidirectionally.

Serine 195 phosphorylation in the RNA-binding protein Rbm38 increases p63 expression by modulating Rbm38's interaction with the Ago2-miR203 complex

The p63 transcription factor, a p53 family protein, regulates genes involved in various cellular processes, including cell growth and differentiation. We previously showed that RNA-binding motif protein (Rbm38) is a p63 target and, in turn, regulates p63α mRNA stability by binding to the AU/U-rich element in its 3'UTR. Interestingly, Rbm38 can be phosphorylated at serine 195, altering its ability to regulate mRNA translation. However, whether the Ser-195 phosphorylation affects Rbm38's ability to destabilize p63 mRNA remains unclear. Here, using MCF7 and HaCaT cells, we showed that ectopic expression of phosphomimetic Rbm38-S195D increases, whereas WT Rbm38 and nonphosphorylatable Rbm38-S195A decrease p63α protein and transcript levels. We also found that upon activation of glycogen synthase kinase 3β (GSK3β), phosphorylation of Rbm38 at Ser-195 is increased, enhancing p63α expression in an Rbm38-dependent manner. To confirm this, we generated mouse embryo fibroblasts (MEFs) in which Ser-193 in mouse Rbm38 (equivalent to Ser-195 in human Rbm38) was substituted with aspartic acid (Rbm38^S193D/S193D ) or alanine (Rbm38^S193A/S193A ). We observed that the p63 transcript level was increased in Rbm38^S193D/S193D MEFs, but decreased in Rbm38^S193A/S193A MEFs. Mechanistically, we found that WT Rbm38, but not Rbm38-S195D, is required for p63 mRNA degradation mediated by microRNA 203 (miR203). Furthermore, we noted that Argonaute 2 (Ago2), a key regulator in microRNA-mediated mRNA decay, associates with WT Rbm38, and this association was reduced by Ser-195 phosphorylation. Together, our results reveal a critical mechanism by which Ser-195 phosphorylation in Rbm38 increases p63 expression by attenuating the association of Rbm38 with the Ago2-miR203 complex.

Effect of Akt activation and experimental pharmacological inhibition on responses to neoadjuvant chemoradiotherapy in rectal cancer

BACKGROUND

Neoadjuvant chemoradiotherapy (CRT) is one of the preferred initial treatment strategies for locally advanced rectal cancer. Responses are variable, and most patients still require surgery. The aim of this study was to identify molecular mechanisms determining poor response to CRT.

METHODS

Global gene expression and pathway enrichment were assessed in pretreatment biopsies from patients with non-metastatic cT2-4 N0-2 rectal cancer within 7 cm of the anal verge. Downstream Akt activation was assessed in an independent set of pretreatment biopsies and in colorectal cancer cell lines using immunohistochemistry and western blot respectively. The radiosensitizing effects of the Akt inhibitor MK2206 were assessed using clonogenic assays and xenografts in immunodeficient mice.

RESULTS

A total of 350 differentially expressed genes were identified, of which 123 were upregulated and 199 downregulated in tumours from poor responders. Mitochondrial oxidative phosphorylation (P < 0·001) and phosphatidylinositol signalling pathways (P < 0·050) were identified as significantly enriched pathways among the set of differentially expressed genes. Deregulation of both pathways is known to result in Akt activation, and high immunoexpression of phosphorylated Akt S473 was observed among patients with a poor histological response (tumour regression grade 0-2) to CRT (75 per cent versus 48 per cent in those with a good or complete response; P = 0·016). Akt activation was also confirmed in the radioresistant cell line SW480, and a 50 per cent improvement in sensitivity to CRT was observed in vitro and in vivo when SW480 cells were exposed to the Akt inhibitor MK2206 in combination with radiation and 5-fluorouracil.

CONCLUSION

Akt activation is a key event in the response to CRT. Pharmacological inhibition of Akt activation may enhance the effects of CRT. Surgical relevance Organ preservation is an attractive alternative in rectal cancer management following neoadjuvant chemoradiotherapy (CRT) to avoid the morbidity of radical surgery. Molecular steps associated with tumour response to CRT may provide a useful tool for the identification of patients who are candidates for no immediate surgery. In this study, tumours resistant to CRT were more likely to have activation of specific genetic pathways that result in phosphorylated Akt (pAkt) activation. Pretreatment biopsy tissues with high immunoexpression of pAkt were more likely to exhibit a poor histological response to CRT. In addition, the introduction of a pAkt inhibitor to cancer cell lines in vitro and in vivo led to a significant improvement in sensitivity to CRT. Identification of pAkt-activated tumours may thus allow the identification of poor responders to CRT. In addition, the concomitant use of pAkt inhibitors to increase sensitivity to CRT in patients with rectal cancer may constitute an interesting strategy for increasing the chance of a complete response to treatment and organ preservation.

Therapeutic Vulnerabilities in FLT3-Mutant AML Unmasked by Palbociclib

While significant progress has been made in the treatment of acute myeloid leukemia (AML), not all patients can be cured. Mutated in about 1/3 of de novo AML, the FLT3 receptor tyrosine kinase is an attractive target for drug development, activating mutations of the FLT3 map to the juxtamembrane domain (internal tandem duplications, ITD) or the tyrosine kinase domain (TKD), most frequently at codon D835. While small molecule tyrosine kinase inhibitors (TKI) effectively target ITD mutant forms, those on the TKD are not responsive. Moreover, FLT3 inhibition fails to induce a persistent response in patients due to mutational resistance. More potent compounds with broader inhibitory effects on multiple FLT3 mutations are highly desirable. We describe a critical role of CDK6 in the survival of FLT3⁺ AML cells as palbociclib induced apoptosis not only in FLT3–ITD⁺ cells but also in FLT3–D835Y⁺ cells. Antineoplastic effects were also seen in primary patient-derived cells and in a xenograft model, where therapy effectively suppressed tumor formation in vivo at clinically relevant concentrations. In cells with FLT3–ITD or -TKD mutations, the CDK6 protein not only affects cell cycle progression but also transcriptionally regulates oncogenic kinases mediating intrinsic drug resistance, including AURORA and AKT—a feature not shared by its homolog CDK4. While AKT and AURORA kinase inhibitors have significant therapeutic potential in AML, single agent activity has not been proven overly effective. We describe synergistic combination effects when applying these drugs together with palbociclib which could be readily translated to patients with AML bearing FLT3–ITD or –TKD mutations. Targeting synergistically acting vulnerabilities, with CDK6 being the common denominator, may represent a promising strategy to improve AML patient responses and to reduce the incidence of selection of resistance-inducing mutations.

Targeting the BRD4/FOXO3a/CDK6 axis sensitizes AKT inhibition in luminal breast cancer

BRD4 assembles transcriptional machinery at gene super-enhancer regions and governs the expression of genes that are critical for cancer progression. However, it remains unclear whether BRD4-mediated gene transcription is required for tumor cells to develop drug resistance. Our data show that prolonged treatment of luminal breast cancer cells with AKT inhibitors induces FOXO3a dephosphorylation, nuclear translocation, and disrupts its association with SirT6, eventually leading to FOXO3a acetylation as well as BRD4 recognition. Acetylated FOXO3a recognizes the BD2 domain of BRD4, recruits the BRD4/RNAPII complex to the CDK6 gene promoter, and induces its transcription. Pharmacological inhibition of either BRD4/FOXO3a association or CDK6 significantly overcomes the resistance of luminal breast cancer cells to AKT inhibitors in vitro and in vivo. Our study reports the involvement of BRD4/FOXO3a/CDK6 axis in AKTi resistance and provides potential therapeutic strategies for treating resistant breast cancer.

Akt2 causes TGFβ-induced deptor downregulation facilitating mTOR to drive podocyte hypertrophy and matrix protein expression

TGFβ promotes podocyte hypertrophy and expression of matrix proteins in fibrotic kidney diseases such as diabetic nephropathy. Both mTORC1 and mTORC2 are hyperactive in response to TGFβ in various renal diseases. Deptor is a component of mTOR complexes and a constitutive inhibitor of their activities. We identified that deptor downregulation by TGFβ maintains hyperactive mTOR in podocytes. To unravel the mechanism, we found that TGFβ -initiated noncanonical signaling controls deptor inhibition. Pharmacological inhibitor of PI 3 kinase, Ly 294002 and pan Akt kinase inhibitor MK 2206 prevented the TGFβ induced downregulation of deptor, resulting in suppression of both mTORC1 and mTORC2 activities. However, specific isoform of Akt involved in this process is not known. We identified Akt2 as predominant isoform expressed in kidney cortex, glomeruli and podocytes. TGFβ time-dependently increased the activating phosphorylation of Akt2. Expression of dominant negative PI 3 kinase and its signaling inhibitor PTEN blocked Akt2 phosphorylation by TGFβ. Inhibition of Akt2 using a phospho-deficient mutant that inactivates its kinase activity, as well as siRNA against the kinase markedly diminished TGFβ -mediated deptor suppression, its association with mTOR and activation of mTORC1 and mTORC2. Importantly, inhibition of Akt2 blocked TGFβ -induced podocyte hypertrophy and expression of the matrix protein fibronectin. This inhibition was reversed by the downregulation of deptor. Interestingly, we detected increased phosphorylation of Akt2 concomitant with TGFβ expression in the kidneys of diabetic rats. Thus, our data identify previously unrecognized Akt2 kinase as a driver of TGFβ induced deptor downregulation and sustained mTORC1 and mTORC2 activation. Furthermore, we provide the first evidence that deptor downstream of Akt2 contributes to podocyte hypertrophy and matrix protein expression found in glomerulosclerosis in different renal diseases.

E-cadherin loss induces targetable autocrine activation of growth factor signalling in lobular breast cancer

Despite the fact that loss of E-cadherin is causal to the development and progression of invasive lobular carcinoma (ILC), options to treat this major breast cancer subtype are limited if tumours develop resistance to anti-oestrogen treatment regimens. This study aimed to identify clinically targetable pathways that are aberrantly active downstream of E-cadherin loss in ILC. Using a combination of reverse-phase protein array (RPPA) analyses, mRNA sequencing, conditioned medium growth assays and CRISPR/Cas9-based knock-out experiments, we demonstrate that E-cadherin loss causes increased responsiveness to autocrine growth factor receptor (GFR)-dependent activation of phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/Akt signalling. Autocrine activation of GFR signalling and its downstream PI3K/Akt hub was independent of oncogenic mutations in PIK3CA, AKT1 or PTEN. Analyses of human ILC samples confirmed growth factor production and pathway activity. Pharmacological inhibition of Akt using AZD5363 or MK2206 resulted in robust inhibition of cell growth and survival of ILC cells, and impeded tumour growth in a mouse ILC model. Because E-cadherin loss evokes hypersensitisation of PI3K/Akt activation independent of oncogenic mutations in this pathway, we propose clinical intervention of PI3K/Akt in ILC based on functional E-cadherin inactivation, irrespective of activating pathway mutations.

Genome-Informed Targeted Therapy for Osteosarcoma

Osteosarcoma is a highly aggressive cancer for which treatment has remained essentially unchanged for more than 30 years. Osteosarcoma is characterized by widespread and recurrent somatic copy-number alterations (SCNA) and structural rearrangements. In contrast, few recurrent point mutations in protein-coding genes have been identified, suggesting that genes within SCNAs are key oncogenic drivers in this disease. SCNAs and structural rearrangements are highly heterogeneous across osteosarcoma cases, suggesting the need for a genome-informed approach to targeted therapy. To identify patient-specific candidate drivers, we used a simple heuristic based on degree and rank order of copy-number amplification (identified by whole-genome sequencing) and changes in gene expression as identified by RNA sequencing. Using patient-derived tumor xenografts, we demonstrate that targeting of patient-specific SCNAs leads to significant decrease in tumor burden, providing a road map for genome-informed treatment of osteosarcoma. SIGNIFICANCE: Osteosarcoma is treated with a chemotherapy regimen established 30 years ago. Although osteosarcoma is genomically complex, we hypothesized that tumor-specific dependencies could be identified within SCNAs. Using patient-derived tumor xenografts, we found a high degree of response for "genome-matched" therapies, demonstrating the utility of a targeted genome-informed approach.This article is highlighted in the In This Issue feature, p. 1.

Combination of lutetium-177 labelled anti-L1CAM antibody chCE7 with the clinically relevant protein kinase inhibitor MK1775: a novel combination against human ovarian carcinoma

Background

Protein kinase inhibitors (PKIs) are currently tested in clinical studies (phase I-III) as an alternative strategy against (recurrent) ovarian cancer. Besides their anti-tumour efficacy, several PKIs have also shown radiosensitizing effects when combined with external beam radiation. Based on these results we asked if the addition of PKIs offers a therapeutic opportunity to improve radioimmunotherapy (RIT) against ovarian cancer. Five PKIs (alisertib, MK1775, MK2206, saracatinib, temsirolimus) were chosen for cytotoxicity screenings based on their current clinical trials in the treatment of ovarian cancer and their influence on cell cycle regulation and DNA damage repair pathways. We combined selected PKIs with ¹⁷⁷Lu-labelled anti-L1CAM monoclonal antibody chCE7 for our investigations.

Methods

PKIs cytotoxicity was determined via cell colony-forming assays. Biomarker of DNA double-strand breaks (DSBs, γH2A.X) was analysed by western blot and fluorescence microscopy. Flow cytometric measurements were performed to evaluate levels of apoptosis based on mono- or combination treatments. The best combination was used for in vivo combination therapy studies in nude mice with SKOV3ip and IGROV1 human ovarian cancer xenografts. Bonferroni correction was used to determine statistical significance for multiple comparisons.

Results

The highest cytotoxicity against both cell lines was observed for MK1775 and alisertib. Combinations including ¹⁷⁷Lu-labelled mAb chCE7 and MK1775 decreased ¹⁷⁷Lu-DOTA-chCE7 IC₆₀-values 14-fold, compared to 6-fold, when the radioimmunoconjugate was combined with alisertib. The most effective PKI MK1775 was further evaluated and demonstrated synergistic effects in combination with ¹⁷⁷Lu-DOTA-chCE7 against IGROV1 cells. Significantly higher amounts of DSBs were detected in IGROV1 cells after combination (91%) compared to either treatment alone (MK1775: 52%; radioimmunoconjugate: 72%; p < 0.0125). Early-apoptosis was significantly enhanced in IGROV1 cells correlating with induced DSBs (¹⁷⁷Lu-DOTA-chCE7: 8%, MK1775: 28%, ¹⁷⁷Lu-DOTA-chCE7 + MK1775: 40%, p < 0.0125). Immunohistochemistry analysis of γH2A.X expression levels after therapy in SKOV3ip xenografts revealed a high sensitivity of the tumour cells to MK1775 and a high radioresistance. A prominent effect of tumour growth inhibition of the RIT and of the combination therapy was observed in vivo in a late stage IGROV1 xenograft model.

Conclusions

Our results warrant further evaluation of combination of MK1775 and radioimmunotherapy.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4836-1) contains supplementary material, which is available to authorized users.

AKT inhibitor MK-2206 sensitizes breast cancer cells to MLN4924, a first-in-class NEDD8-activating enzyme (NAE) inhibitor

Breast cancer is a common type of cancer among female cancer patients and the main cause of cancer-related deaths. During the last decades, targeted therapies for breast cancer have been rapidly developing. Among them, MLN4924, a first-in-class NEDD8-activating enzyme (NAE) inhibitor, has performed antitumor activity by inactivating the cullin-RING ligases and causing the accumulation of their substrates to induce apoptosis in a number of studies. In this study, we found that MLN4924 activates the AKT pathway in both HER2-positive and triple-negative breast cancer (TNBC) cell lines. Given that AKT signaling is responsible for tumor progression and drug resistance in some types of cancers, we hypothesized that the AKT inhibitor may synergistically enhance the tumor suppression capability in breast cancer by MLN4924. To demonstrate the sensitizing effect, MK-2206 was chosen as the adjuvant treatment, and cell growth, migration and apoptosis were detected. The results showed that MLN4924 treatment inhibited cell growth and migration and induced apoptosis in both SK-BR3 and MDA-MB231 breast cancer cell lines. More importantly, the combined treatment of MLN4924 and MK-2206 indeed caused stronger cytotoxicity and inhibition of migration and a much higher induction of apoptosis compared with MLN4924 treatment alone. Our study provides the proof-of-concept evidence for strategic drug combination of MLN4924 with an AKT inhibitor for maximal killing of breast cancer cells via the enhancement of apoptosis.

Inhibiting eEF-2 kinase-mediated autophagy enhanced the cytocidal effect of AKT inhibitor on human nasopharyngeal carcinoma

Aim

Our previous research showed that AKT inactivation via small molecule inhibitors did not induce significant apoptosis, but rather markedly increased autophagy in nasopharyngeal carcinoma (NPC). The purpose of the current study was to determine whether autophagy inhibition can enhance the anticancer efficacy of an AKT inhibitor (MK-2206).

Materials and methods

NPC cell lines CNE-2 (Epstein–Barr virus negative) and C666-1 (Epstein–Barr virus positive) were used to conduct the research. Autophagy induction effects were evaluated via Western blotting. Eukaryotic elongation factor-2 (eEF-2) kinase was specifically and stably knocked down using shRNA. The growth and proliferation of the cells were assessed by Cell Counting Kit-8. In CNE-2 xenograft tumors, the antitumor effects of an AKT inhibitor (MK-2206) combined with an eEF-2 kinase inhibitor (NH125) were tested.

Results

MK-2206 induced eEF-2 kinase-dependent autophagy in NPC cell lines. Knockdown of eEF-2 kinase using shRNA blunted the autophagy activated by MK-2206. Compared with treatment with MK-2206 alone, shRNA or NH125 suppressed eEF-2 kinase and increased the growth-inhibitory effect of MK-2206 on the human NPC cell lines. The synergistic effects of eEF-2 kinase inhibition and MK-2206 were similar to those of the combination of hydroxychloroquine and MK-2206. Moreover, NH125 showed good synergistic effects with MK-2206 in vivo.

Conclusion

eEF-2 kinase-mediated autophagy induced by AKT inhibition played a protective role in NPC cells. Inhibition of eEF-2 kinase may be an effective method for increasing the efficacy of an AKT inhibitor such as MK-2206 in NPC.

The Protozoan Parasite Toxoplasma gondii Selectively Reprograms the Host Cell Translatome

The intracellular parasite Toxoplasma gondii promotes infection by targeting multiple host cell processes; however, whether it modulates mRNA translation is currently unknown. Here, we show that infection of primary murine macrophages with type I or II T. gondii strains causes a profound perturbation of the host cell translatome. Notably, translation of transcripts encoding proteins involved in metabolic activity and components of the translation machinery was activated upon infection. In contrast, the translational efficiency of mRNAs related to immune cell activation and cytoskeleton/cytoplasm organization was largely suppressed. Mechanistically, T. gondii bolstered mechanistic target of rapamycin (mTOR) signaling to selectively activate the translation of mTOR-sensitive mRNAs, including those with a 5'-terminal oligopyrimidine (5' TOP) motif and those encoding mitochondrion-related proteins. Consistent with parasite modulation of host mTOR-sensitive translation to promote infection, inhibition of mTOR activity suppressed T. gondii replication. Thus, selective reprogramming of host mRNA translation represents an important subversion strategy during T. gondii infection.

The next generation of PI3K-Akt-mTOR pathway inhibitors in breast cancer cohorts

The PI3K/Akt/mTOR pathway plays a role in various oncogenic processes in breast cancer and key pathway aberrations have been identified which drive the different molecular subtypes. Early drugs developed targeting this pathway produced some clinical success but were hampered by pharmacokinetics, tolerability and efficacy problems. This created a need for new PI3K pathway-inhibiting drugs, which would produce more robust results allowing incorporation into treatment regimens for breast cancer patients. In this review, the most promising candidates from the new generation of PI3K-pathway inhibitors is explored, presenting evidence from preclinical and early clinical research, as well as ongoing trials utilising these drugs in breast cancer cohorts. The problems hindering the development of drugs targeting the PI3K pathway are examined, which have created problems for their use as monotherapies. PI3K pathway inhibitor combinations therefore remains a dynamic research area, and their role in combination with immunotherapies and epigenetic therapies is also inspected.

CK2 inhibition protects white matter from ischemic injury

Strokes occur predominantly in the elderly and white matter (WM) is injured in most strokes, contributing to the disability associated with clinical deficits. Casein kinase 2 (CK2) is expressed in neuronal cells and was reported to be neuroprotective during cerebral ischemia. Recently, we reported that CK2 is abundantly expressed by glial cells and myelin. However, in contrast to its role in cerebral (gray matter) ischemia, CK2 activation during ischemia mediated WM injury via the CDK5 and AKT/GSK3β signaling pathways (Bastian et al., 2018). Subsequently, CK2 inhibition using the small molecule inhibitor CX-4945 correlated with preservation of oligodendrocytes as well as conservation of axon structure and axonal mitochondria, leading to improved functional recovery. Notably, CK2 inhibition promoted WM function when applied before or after ischemic injury by differentially regulating the CDK5 and AKT/GSK3β pathways. Specifically, blockade of the active conformation of AKT conferred post-ischemic protection to young, aging, and old WM, suggesting a common therapeutic target across age groups. CK2 inhibitors are currently being used in clinical trials for cancer patients; therefore, it is important to consider the potential benefits of CK2 inhibitors during an ischemic attack.

Cross Talk Networks of Mammalian Target of Rapamycin Signaling With the Ubiquitin Proteasome System and Their Clinical Implications in Multiple Myeloma

Multiple myeloma (MM) is the second most common hematological malignancy and results from the clonal amplification of plasma cells. Despite recent advances in treatment, MM remains incurable with a median survival time of only 5-6years, thus necessitating further insights into MM biology and exploitation of novel therapeutic approaches. Both the ubiquitin proteasome system (UPS) and the PI3K/Akt/mTOR signaling pathways have been implicated in the pathogenesis, and treatment of MM and different lines of evidence suggest a close cross talk between these central cell-regulatory signaling networks. In this review, we outline the interplay between the UPS and mTOR pathways and discuss their implications for the pathophysiology and therapy of MM.

Loss of EGFR confers acquired resistance to AZD9291 in an EGFR-mutant non-small cell lung cancer cell line with an epithelial-mesenchymal transition phenotype

PURPOSE

AZD9291 is an irreversible, small-molecule inhibitor which has potency against mutant EGFR- and T790M-resistant mutation. Despite the encouraging efficacy in clinical, the acquired resistance will finally occur. Further study will need to be done to identify the acquired resistance mechanisms and determine the next treatment.

METHODS

We established an AZD9291-resistant cell line (HCC827/AZDR) from parental HCC827 cell line through stepwise pulsed selection of AZD9291. The expression of EGFR and its downstream pathways were determined by western blot analysis or immunofluorescence assay. The sensitivity to indicated agents were evaluated by MTS.

RESULTS

Compared with parental HCC827 cells, the HCC827/AZDR cells showed high resistance to AZD9291 and other EGFR-TKIs, and exhibited a mesenchymal-like phenotype. Almost complete loss of EGFR expression was observed in HCC827/AZDR cells. But the activation of downstream pathway, MAPK signaling, was found in HCC827/AZDR cells even in the presence of AZD9291. Inhibition of MAPK signaling had no effect on cell viability of HCC827/AZDR and could not reverse AZD9291 resistance because of the subsequent activation of AKT signaling. When treated with the combination of AKT and MAPK inhibitor, HCC827/AZDR showed remarkable growth inhibition.

CONCLUSIONS

Loss of EGFR could be proposed as a potential acquired resistance mechanism of AZD9291 in EGFR-mutant NSCLC cells with an EMT phenotype. Despite the loss of EGFR, the activation of MAPK pathway which had crosstalk with AKT pathway could maintain the proliferation and survival of resistant cells. Blocking MAPK and AKT signaling may be a potential therapeutic strategy following AZD9291 resistance.

Autophagic cell death associated to Sorafenib in renal cell carcinoma is mediated through Akt inhibition in an ERK1/2 independent fashion

OBJECTIVES

To fully clarify the role of Mitogen Activated Protein Kinase in the therapeutic response to Sorafenib in Renal Cell Carcinoma as well as the cell death mechanism associated to this kinase inhibitor, we have evaluated the implication of several Mitogen Activated Protein Kinases in Renal Cell Carcinoma-derived cell lines.

MATERIALS AND METHODS

An experimental model of Renal Cell Carcinoma-derived cell lines (ACHN and 786-O cells) was evaluated in terms of viability by MTT assay, induction of apoptosis by caspase 3/7 activity, autophagy induction by LC3 lipidation, and p62 degradation and kinase activity using phospho-targeted antibodies. Knock down of ATG5 and ERK5 was performed using lentiviral vector coding specific shRNA.

RESULTS

Our data discard Extracellular Regulated Kinase 1/2 and 5 as well as p38 Mitogen Activated Protein Kinase pathways as mediators of Sorafenib toxic effect but instead indicate that the inhibitory effect is exerted through the PI3K/Akt signalling pathway. Furthermore, we demonstrate that inhibition of Akt mediates cell death associated to Sorafenib without caspase activation, and this is consistent with the induction of autophagy, as indicated by the use of pharmacological and genetic approaches.

CONCLUSION

The present report demonstrates that Sorafenib exerts its toxic effect through the induction of autophagy in an Akt-dependent fashion without the implication of Mitogen Activated Protein Kinase. Therefore, our data discard the use of inhibitors of the RAF-MEK-ERK1/2 signalling pathway in RCC and support the use of pro-autophagic compounds, opening new therapeutic opportunities for Renal Cell Carcinoma.

Augmentation of Ouabain-Induced Increase in Heart Muscle Contractility by Akt Inhibitor MK-2206

Cardiac steroids (CSs), such as ouabain and digoxin, increase the force of contraction of heart muscle and are used for the treatment of congestive heart failure (CHF). However, their small therapeutic window limits their use. It is well established that Na+, K+-ATPase inhibition mediates CS-induced increase in heart contractility. Recently, the involvement of intracellular signal transduction was implicated in this effect. The aim of the present study was to test the hypothesis that combined treatment with ouabain and Akt inhibitor (MK-2206) augments ouabain-induced inotropy in mammalian models. We demonstrate that the combined treatment led to an ouabain-induced increase in contractility at concentrations at which ouabain alone was ineffective. This was shown in 3 experimental systems: neonatal primary rat cardiomyocytes, a Langendorff preparation, and an in vivo myocardial infarction induced by left anterior descending coronary artery (LAD) ligation. Furthermore, cell viability experiments revealed that this treatment protected primary cardiomyocytes from MK-2206 toxicity and in vivo reduced the size of scar tissue 10 days post-LAD ligation. We propose that Akt activity imposes a constant inhibitory force on muscle contraction, which is attenuated by low concentrations of MK-2206, resulting in potentiation of the ouabain effect. This demonstration of the increase in the CS effect advocates the development of the combined treatment in CHF.

Protein Tyrosine Signaling and its Potential Therapeutic Implications in Carcinogenesis

Protein tyrosine phosphorylation is a crucial signaling mechanism that plays a role in epithelial carcinogenesis. Protein tyrosine kinases (PTKs) control various cellular processes including growth, differentiation, metabolism, and motility by activating major signaling pathways including STAT3, AKT, and MAPK. Genetic mutation of PTKs and/or prolonged activation of PTKs and their downstream pathways can lead to the development of epithelial cancer. Therefore, PTKs became an attractive target for cancer prevention. PTK inhibitors are continuously being developed, and they are currently used for the treatment of cancers that show a high expression of PTKs. Protein tyrosine phosphatases (PTPs), the homeostatic counterpart of PTKs, negatively regulate the rate and duration of phosphotyrosine signaling. PTPs initially were considered to be only housekeeping enzymes with low specificity. However, recent studies have demonstrated that PTPs can function as either tumor suppressors or tumor promoters, depending on their target substrates. Together, both PTK and PTP signal transduction pathways are potential therapeutic targets for cancer prevention and treatment.