Inhibition of Akt and other AGC kinases: A target for clinical cancer therapy?

Estradiol cypionate inhibits proliferation and promotes apoptosis of gastric cancer by regulating AKT ubiquitination

Gastric cancer is a common gastrointestinal malignancy worldwide, with a high mortality rate and poor prognosis. Multidrug resistance remains a major obstacle to successful treatment for patients. Hence, it is of great significance to develop novel therapies to potentiate the anti-tumor effect. In this study, we have investigated the effect of estradiol cypionate (ECP) on gastric cancer in vitro and vivo. Our data show that ECP inhibited the proliferation, promoted apoptosis, and caused G1/S phase arrest of gastric cancer cells. The mechanism by which ECP promoted apoptosis of gastric cancer cells was related to the downregulation of AKT protein expression caused by the increased ubiquitination modification levels of AKT, which finally inhibited the over-activation of the PI3K-AKT-mTOR signaling pathway. In vivo tumorigenesis experiments showed that ECP significantly inhibited the growth of gastric cancer cells, showing promise for clinical application. The above findings indicate that ECP inhibited the growth of gastric cancer and induced apoptosis through the PI3K /Akt/mTOR pathway. In summary, the efficacy showed in our data suggests that ECP is a promising anti-tumor compound for gastric cancer.

Luteolin inhibits triple-negative breast cancer by inducing apoptosis and autophagy through SGK1-FOXO3a-BNIP3 signaling

Background: Triple-negative breast cancer (TNBC) is one of the most prominent neoplasm disorders and lacks efficacious treatments yet. Luteolin (3',4',5,7-tetrahydroxyflavone), a natural flavonoid commonly presented in plants, has been reported to delay the progression of TNBC. However, the precise mechanism is still elusive. We aimed to elucidate the inhibition and molecular regulation mechanism of luteolin on TNBC. Methods: The effects of luteolin on the biological functions of TNBC cells were first evaluated using the corresponding assays for cell counting kit-8 assay, flow cytometry, wound-healing assay, and transwell migration assay, respectively. The mechanism of luteolin on TNBC cells was then analyzed by RNA sequencing and verified by RT-qPCR, Western blot, transmission electron microscopy, etc. Finally, in vivo mouse tumor models were constructed to further confirm the effects of luteolin on TNBC. Results: Luteolin dramatically suppressed cell proliferation, invasion, and migration while favoring cell apoptosis in a dose- and time-dependent manner. In TNBC cells treated with luteolin, SGK1 and AKT3 were significantly downregulated while their downstream gene BNIP3 was upregulated. According to the results of 3D modeling, the direct binding of luteolin to SGK1 was superior to that of AKT3. The inhibition of SGK1 promoted FOXO3a translocation into the nucleus and led to the transcription of BNIP3 both in vitro and in vivo, eventually facilitating the interaction between BNIP3 and apoptosis and autophagy protein. Furthermore, the upregulation of SGK1, induced by luteolin, attenuated the apoptosis and autophagy of the TNBC. Conclusion: Luteolin inhibits TNBC by inducing apoptosis and autophagy through SGK1-FOXO3a-BNIP3 signaling.

Targeted Approaches to HER2-Low Breast Cancer: Current Practice and Future Directions

Simple Summary

HER2-low breast cancer (BC) accounts for more than half of breast cancer patients. Anti-HER2 therapy has been ineffective in HER2-low BC, for which palliative chemotherapy is the main treatment modality. The definitive efficacy of T-Dxd in HER2-low BC breaks previous treatment strategies, which will redefine HER2-low and thus reshape anti-HER2 therapy. This review summarizes detection technologies and novel agents for HER2-low BC, and explores their possible role in future clinics, to provide ideas for the diagnosis and treatment of HER2-low BC.

Abstract

HER2-low breast cancer (BC) has a poor prognosis, making the development of more suitable treatment an unmet clinical need. While chemotherapy is the main method of treatment for HER2-low BC, not all patients benefit from it. Antineoplastic therapy without chemotherapy has shown promise in clinical trials and is being explored further. As quantitative detection techniques become more advanced, they assist in better defining the expression level of HER2 and in guiding the development of targeted therapies, which include directly targeting HER2 receptors on the cell surface, targeting HER2-related intracellular signaling pathways and targeting the immune microenvironment. A new anti-HER2 antibody-drug conjugate called T-DM1 has been successfully tested and found to be highly effective in clinical trials. With this progress, it could eventually be transformed from a disease without a defined therapeutic target into a disease with a defined therapeutic molecular target. Furthermore, efforts are being made to compare the sequencing and combination of chemotherapy, endocrine therapy, and HER2-targeted therapy to improve prognosis to customize the subtype of HER2 low expression precision treatment regimens. In this review, we summarize the current and upcoming treatment strategies, to achieve accurate management of HER2-low BC.

Beyond controlling cell size: functional analyses of S6K in tumorigenesis

As a substrate and major effector of the mammalian target of rapamycin complex 1 (mTORC1), the biological functions of ribosomal protein S6 kinase (S6K) have been canonically assigned for cell size control by facilitating mRNA transcription, splicing, and protein synthesis. However, accumulating evidence implies that diverse stimuli and upstream regulators modulate S6K kinase activity, leading to the activation of a plethora of downstream substrates for distinct pathobiological functions. Beyond controlling cell size, S6K simultaneously plays crucial roles in directing cell apoptosis, metabolism, and feedback regulation of its upstream signals. Thus, we comprehensively summarize the emerging upstream regulators, downstream substrates, mouse models, clinical relevance, and candidate inhibitors for S6K and shed light on S6K as a potential therapeutic target for cancers.

Inhibition of PDK1 enhances radiosensitivity and reverses epithelial-mesenchymal transition in nasopharyngeal carcinoma

BACKGROUND

Radioresistance challenges the clinical outcomes of nasopharyngeal carcinoma (NPC). The 3-phosphoinositide-dependent protein kinase 1 (PDK1) is a crucial kinase of PI3K/AKT signaling pathway which has been implicated in the process of radioresistance. However, the role of PDK1 in NPC remains largely unclear.

METHODS

The expression of PDK1 was determined by immunohistochemistry and Western blot. The effects of RNA interference and pharmacologic inhibitor of PDK1 in combination with irradiation were investigated.

RESULTS

Overexpression of PDK1 was correlated with poor prognosis in patients with NPC. PDK1 depletion enhanced radiosensitivity of NPC cells both in vitro and in vivo. Additionally, a specific PDK1 inhibitor also had the potential to enhance radiosensitivity in radioresistant NPC cells. Mechanistically, PDK1 depletion inhibited various targets of AKT including mTOR and GSK-3β and reversed the epithelial-mesenchymal transition.

CONCLUSIONS

These findings indicated that PDK1 might be a potential target for NPC.

Covalent allosteric inhibitors of Akt generated using a click fragment approach

Akt is a protein kinase that has been implicated in the progression of cancerous tumours. A number of covalent allosteric Akt inhibitors are known, and based on these scaffolds, a small library of novel potential covalent allosteric imidazopyridine‐based inhibitors was designed. The envisaged compounds were synthesised, with click chemistry enabling a modular approach to a number of the target compounds. The binding modes, potencies and antiproliferative activities of these synthesised compounds were explored, thereby furthering the structure activity relationship knowledge of this class of Akt inhibitors. Three novel covalent inhibitors were identified, exhibiting moderate activity against Akt1 and various cancer cell lines, potentially paving the way for future covalent allosteric inhibitors with improved properties.

PKI-587 enhances radiosensitization of hepatocellular carcinoma by inhibiting the PI3K/AKT/mTOR pathways and DNA damage repair

Radiation is an important therapeutic strategy for hepatocellular (HCC). In this study, we evaluated the role of the dual PI3K/mTOR inhibitor, PKI-587, on radiosensitization of HCC and its possible mechanism. MTT, colony formation, flow cytometry, and immunofluorescence were used to analyze the proliferation, cell cycle, formation of residual γ-H2AX foci, and apoptosis of HCC cells. A SK-Hep1 xenograft HCC model was used to assess the effects of PKI-587 in combination with ionizing radiation in vivo. The activation levels of PI3K/AKT/mTOR and DNA damage repair pathways and their downstream effector molecules were detected with Western blot. It was found that PKI-587 sensitized HCC cells to radiation by increasing DNA damage, enhancing G0/G1 cell-cycle arrest, and inducing apoptosis. In vivo, the combination of radiation with PKI-587 significantly inhibited tumor growth. These findings suggest the usefulness of PKI-587 on radiosensitization of HCC cells by inhibiting the PI3K/AKT/mTOR and DNA damage repair pathways. The combination of ionizing radiation and PKI-587 may be a strategy to improve the efficacy of treating HCC.

Molecular target: pan-AKT in gastric cancer

The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signalling pathway is involved in multiple cellular processes, including cell survival, proliferation, differentiation, metabolism and cytoskeletal reorganisation. The downstream effectors of this PI3K pathway are also essential for maintaining physiologic homeostasis, commonly dysregulated in most solid tumours. AKT is the key regulator in PI3K/AKT/mTOR signalling, interacting with multiple intracellular molecules. AKT activation subsequently leads to a number of potential downstream effects, and its aberrant activation results in the pathogenesis of cancer. Accordingly, as an attractive therapeutic target for cancer treatment, several AKT inhibitors are currently under development and in multiple stages of clinical trials for various types of malignancy, including gastric cancer (GC). Therefore, the authors review the significance of AKT and recent studies on AKT inhibitors in GC, focusing on the scientific background with the potential to improve treatment outcomes.

Akt Isoforms: A Family Affair in Breast Cancer

Simple Summary

Breast cancer is the second leading cause of cancer-related death in women in the United States. The Akt signaling pathway is deregulated in approximately 70% of patients with breast cancer. While targeting Akt is an effective therapeutic strategy for the treatment of breast cancer, there are several members in the Akt family that play distinct roles in breast cancer. However, the function of Akt isoforms depends on many factors. This review analyzes current progress on the isoform-specific functions of Akt isoforms in breast cancer.

Abstract

Akt, also known as protein kinase B (PKB), belongs to the AGC family of protein kinases. It acts downstream of the phosphatidylinositol 3-kinase (PI3K) and regulates diverse cellular processes, including cell proliferation, cell survival, metabolism, tumor growth and metastasis. The PI3K/Akt signaling pathway is frequently deregulated in breast cancer and plays an important role in the development and progression of breast cancer. There are three closely related members in the Akt family, namely Akt1(PKBα), Akt2(PKBβ) and Akt3(PKBγ). Although Akt isoforms share similar structures, they exhibit redundant, distinct as well as opposite functions. While the Akt signaling pathway is an important target for cancer therapy, an understanding of the isoform-specific function of Akt is critical to effectively target this pathway. However, our perception regarding how Akt isoforms contribute to the genesis and progression of breast cancer changes as we gain new knowledge. The purpose of this review article is to analyze current literatures on distinct functions of Akt isoforms in breast cancer.

LXR stimulates a metabolic switch and reveals cholesterol homeostasis as a statin target in Tasmanian devil facial tumor disease

Devil facial tumor disease (DFTD) and its lack of available therapies are propelling the Tasmanian devil population toward extinction. This study demonstrates that cholesterol homeostasis and carbohydrate energy metabolism sustain the proliferation of DFTD cells in a cell-type-dependent manner. In addition, we show that the liver-X nuclear receptor-β (LXRβ), a major cholesterol cellular sensor, and its natural ligand 24S-hydroxycholesterol promote the proliferation of DFTD cells via a metabolic switch toward aerobic glycolysis. As a proof of concept of the role of cholesterol homeostasis on DFTD proliferation, we show that atorvastatin, an FDA-approved statin-drug subtype used against human cardiovascular diseases that inhibits cholesterol synthesis, shuts down DFTD energy metabolism and prevents tumor growth in an in vivo DFTD-xenograft model. In conclusion, we show that intervention against cholesterol homeostasis and carbohydrate-dependent energy metabolism by atorvastatin constitutes a feasible biochemical treatment against DFTD, which may assist in the conservation of the Tasmanian devil.

SGK1 in Human Cancer: Emerging Roles and Mechanisms

Serum and glucocorticoid-induced protein kinase 1 (SGK1) is a member of the "AGC" subfamily of protein kinases, which shares structural and functional similarities with the AKT family of kinases and displays serine/threonine kinase activity. Aberrant expression of SGK1 has profound cellular consequences and is closely correlated with human cancer. SGK1 is considered a canonical factor affecting the expression and signal transduction of multiple genes involved in the genesis and development of many human cancers. Abnormal expression of SGK1 has been found in tissue and may hopefully become a useful indicator of cancer progression. In addition, SGK1 acts as a prognostic factor for cancer patient survival. This review systematically summarizes and discusses the role of SGK1 as a diagnostic and prognostic biomarker of diverse cancer types; focuses on its essential roles and functions in tumorigenesis, cancer cell proliferation, apoptosis, invasion, metastasis, autophagy, metabolism, and therapy resistance and in the tumor microenvironment; and finally summarizes the current understanding of the regulatory mechanisms of SGK1 at the molecular level. Taken together, this evidence highlights the crucial role of SGK1 in tumorigenesis and cancer progression, revealing why it has emerged as a potential target for cancer therapy.

TRIM37 overexpression is associated with chemoresistance in hepatocellular carcinoma via activating the AKT signaling pathway

BACKGROUND

Hepatocellular carcinoma (HCC) is the most common primary liver cancer in the worldwide. Sorafenib is approved for first-line therapy against advanced HCC, but chemo-resistance is still a leading cause of tumor relapse and treatment failure in HCC. Thus, there is a significant clinical need to identify effective strategies to overcome drug resistance on the disease.

METHODS

The protein and mRNA expression of TRIM37 in HCC cell lines and patient tissues were determined using Real-time PCR and Western blot, respectively. HCC tissue samples were analyzed by IHC to investigate the association between TRIM37expression and the clinicopathological characteristics of HCC patients. Functional assays, such as MTT, FACS, and Tunel assay, are used to determine the oncogenic role of TRIM37 in human HCC progression. Furthermore, western blotting and luciferase assay were used to determine the mechanism of TRIM37promotes chemoresistance in HCC.

RESULTS

We found that both the mRNA and protein expression of TRIM37 was markedly upregulated in HCC cell lines and tissues, especially in Sorafenib-resistance HCC tissues. Moreover, high TRIM37 expression was associated with poor prognosis with HCC patients. TRIM37 overexpression confers Sorafenib resistance on HCC cells; however, inhibition of TRIM37 sensitized HCC cell lines to Sorafenib cytotoxicity. Additionally, TRIM37 upregulated the levels of AKT activity and phosphorylated AKT, thereby activating canonical AKT signaling.

CONCLUSION

Our findings suggest that targeting TRIM37 signaling may represent a promising strategy to enhance Sorafenib response in HCC patients with chemoresistant.

MiR-200b Inhibits Tumor Growth and Chemoresistance via Targeting p70S6K1 in Lung Cancer

Downregulation of microRNA-200b (miR-200b) has been identified in a range of cancers, yet the specific mechanisms whereby it influences lung cancer growth require further exploration. We determined that lung cancer patient tumor samples exhibit decreased miR-200b expression, and we further found this miRNA to inhibit tumor growth via interfering with ERK1/2 and AKT signaling, targeting p70S6K1 to suppress HIF-1α expression. This miRNA further rendered H1299 cells more sensitive to cisplatin while impairing their proliferative and invasive potential through its ability to target and inhibit the activity of p70S6K1. These results were further confirmed in a murine xenograft model in which miR-200b also inhibited the growth of tumor and suppressed p70S6K1, p-AKT, p-ERK1/2, and HIF-1α expression. These findings clearly demonstrate a role for miR-200b in suppressing lung cancer development, making it a potentially relevant target for future diagnostic and therapeutic interventions.

Contrasting effects of transforming growth factor β1 on programmed cell death of bovine mammary epithelial cell lines MAC-T and BME-UV1

A previous study in the bovine mammary epithelial cell line BME-UV1 demonstrated that suppression of the phosphatidylinositol-4,5-biphosphate 3 kinase (PI3K)/AKT (somatotropic) signaling pathway was required for transforming growth factor β1 (TGFβ1)-induced programmed cell death (PCD). To investigate whether this is a universal mechanism for TGFβ1 to induce PCD in bovine mammary epithelium, we compared TGFβ1 modulation of PI3K/AKT and its role in PCD in 2 bovine mammary epithelial cell lines: MAC-T and BME-UV1. In MAC-T cells, TGFβ1 promoted cell survival, and this paralleled a reduction in PI3K/AKT activity, rather than an increase. In BME-UV1 cells, TGFβ1 induced PCD, and this was accompanied by a time-dependent effect on PI3K/AKT activity, including an initial significant increase in the phosphorylation of AKT at 3 h, followed by a reduction between 12 and 24 h, and then an increase at 48 h. Inhibition of AKT activity enhanced TGFβ1-induced PCD in BME-UV1 cells but had no effect on MAC-T cells, suggesting that TGFβ1 mediates PCD in BME-UV1 cells through suppression of AKT activity. Inhibition of TGFβ receptor type I (TβRI) kinase activity completely abrogated TGFβ1-induced PCD in BME-UV1 cells but had no effect on TGFβ1-induced suppression of PCD in MAC-T cells, demonstrating that TGFβ1-induced PCD in BME-UV1 cells is dependent on TβRI/SMAD signaling. These and previous observations suggest that the different effects of TGFβ1 on PCD in these cell lines might involve noncanonical signaling pathways other than PI3K/AKT, and may reflect their different lineages. Future studies should address this finding, taking into consideration the effect that different culture conditions might have on cell phenotype.

A phase I trial of MK-2206 and hydroxychloroquine in patients with advanced solid tumors

PURPOSE

Given the evidence that coordinate inhibition of AKT induces autophagy, we studied the combination of the AKT inhibitor, MK-2206 with hydroxychloroquine (HCQ) in patients with advanced solid tumors.

METHODS

Patients were treated with weekly MK-2206 (135 mg or 200 mg) plus HCQ (200 mg, 400 mg or 600 mg BID).

RESULTS

Thirty-five patients were enrolled across 5 dose levels. Two DLTs of grade 3 maculo-papular rash were observed at dose level 2 (MK-2206 200 mg weekly plus HCQ at 400 mg BID) and 1 DLT of grade 3 fatigue at dose level 2B (MK-2206 135 mg weekly plus HCQ 600 mg BID). The maximum tolerated dose (MTD) was declared as dose level 2B. The most common adverse events attributed to MK-2206 were hyperglycemia (N = 18; 51%), fatigue (N = 17; 49%), maculo-papular rash (N = 16; 46%), diarrhea (N = 12; 34%), anorexia (N = 11; 31%), and nausea (N = 11; 31%). Patients experiencing adverse events attributed to HCQ were small in number (N = 13) and primarily included fatigue (N = 5; 14%) and maculo-papular rashes (N = 3; 9%). Statistically significant effects on the pharmacokinetic properties of MK-2206 were observed in combination with HCQ. In addition, the plasma concentrations of HCQ in the combination with MK-2206 were significantly higher than the plasma levels of HCQ as monotherapy in prior studies. The best overall response of stable disease was observed in 5/34 (15%) patients.

CONCLUSION

The combination of MK-2206 and hydroxychloroquine was tolerable, but with substantial number of drug-related AEs and minimal evidence of antitumor activity.

Deep Learning Enhancing Kinome-Wide Polypharmacology Profiling: Model Construction and Experiment Validation

The kinome-wide virtual profiling of small molecules with high-dimensional structure-activity data is a challenging task in drug discovery. Here, we present a virtual profiling model against a panel of 391 kinases based on large-scale bioactivity data and the multitask deep neural network algorithm. The obtained model yields excellent internal prediction capability with an auROC of 0.90 and consistently outperforms conventional single-task models on external tests, especially for kinases with insufficient activity data. Moreover, more rigorous experimental validations including 1410 kinase-compound pairs showed a high-quality average auROC of 0.75 and confirmed many novel predicted "off-target" activities. Given the verified generalizability, the model was further applied to various scenarios for depicting the kinome-wide selectivity and the association with certain diseases. Overall, the computational model enables us to create a comprehensive kinome interaction network for designing novel chemical modulators or drug repositioning and is of practical value for exploring previously less studied kinases.

FGFR3S249C mutation promotes chemoresistance by activating Akt signaling in bladder cancer cells

Fibroblast growth factor receptor 3 (FGFR3) is a high frequency mutant gene in bladder cancer (BCa) and has become a promising therapeutic target due to its involvement in cell proliferation and migration. However, whether and how FGFR3 mutations affects BCa cell chemosensitivity is unknown. The current study aimed to elucidate the role of the FGFR3^S249C mutation in the development of chemoresistance in BCa cells. The results revealed that 97-7 (FGFR3^S249C) cells had decreased sensitivity to cisplatin compared with 5637 (FGFR3^WT) and T24 (FGFR3^WT) cells. The ratio of phosphorylated-Akt/total-Akt was higher in 97-7 (FGFR3^S249C) cells, which was reversed by knockdown of FGFR3. Furthermore, inhibition of Akt signaling by GDC0068 or LY294002 increased the cisplatin sensitivity of 97-7 (FGFR3^S249C) cells. GDC0068 or LY294002 was also revealed to augment the effects of cisplatin on 97-7 (FGFR3^S249C) cell proliferation and apoptosis. The results of the present study demonstrated that the FGFR3^S249C mutation promotes chemoresistance in BCa cells by activating the Akt signaling pathway. The FGFR3^S249C mutation may therefore be used as a predictor of chemosensitivity in patients with BCa.

FGF1ΔHBS ameliorates chronic kidney disease via PI3K/AKT mediated suppression of oxidative stress and inflammation

Currently, there is a lack of effective therapeutic approaches to the treatment of chronic kidney disease (CKD) with irreversible deterioration of renal function. This study aimed to investigate the ability of mutant FGF1 (FGF1^ΔHBS, which has reduced mitogenic activity) to alleviate CKD and to study its associated mechanisms. We found that FGF1^ΔHBS exhibited much weaker mitogenic activity than wild-type FGF1 (FGF1^WT) in renal tissues. RNA-seq analysis revealed that FGF1^ΔHBS inhibited oxidative stress and inflammatory signals in mouse podocytes challenged with high glucose. These antioxidative stress and anti-inflammatory activities of FGF1^ΔHBS prevented CKD in two mouse models: a diabetic nephropathy model and an adriamycin-induced nephropathy model. Further mechanistic analyses suggested that the inhibitory effects of FGF1^ΔHBS on oxidative stress and inflammation were mediated by activation of the GSK-3β/Nrf2 pathway and inhibition of the ASK1/JNK signaling pathway, respectively. An in-depth study demonstrated that both pathways are under control of PI3K/AKT signaling activated by FGF1^ΔHBS. This finding expands the potential uses of FGF1^ΔHBS for the treatment of various kinds of CKD associated with oxidative stress and inflammation.

STYK1 promotes tumor growth and metastasis by reducing SPINT2/HAI-2 expression in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer deaths worldwide. However, the molecular mechanisms underlying NSCLC progression remains not fully understood. In this study, 347 patients with complete clinicopathologic characteristics who underwent NSCLC surgery were recruited for the investigation. We verified that elevated serine threonine tyrosine kinase 1 (STYK1) or decreased serine peptidase inhibitor Kunitz type 2 (SPINT2/HAI-2) expression significantly correlated with poor prognosis, tumor invasion, and metastasis of NSCLC patients. STYK1 overexpression promoted NSCLC cells proliferation, migration, and invasion. STYK1 also induced epithelial–mesenchymal transition by E-cadherin downregulation and Snail upregulation. Moreover, RNA-seq, quantitative polymerase chain reaction (qRT-PCR), and western blot analyses confirmed that STYK1 overexpression significantly decreased the SPINT2 level in NSCLC cells, and SPINT2 overexpression obviously reversed STYK1-mediated NSCLC progression both in vitro and in vivo. Further survival analyses showed that NSCLC patients with high STYK1 level and low SPINT2 level had the worst prognosis and survival. These results indicated that STYK1 facilitated NSCLC progression via reducing SPINT2 expression. Therefore, targeting STYK1 and SPINT2 may be a novel therapeutic strategy for NSCLC.

PEG10 counteracts signaling pathways of TGF-β and BMP to regulate growth, motility and invasion of SW1353 chondrosarcoma cells

Recently, we reported highly active transforming growth factor (TGF)-β and bone morphogenetic protein (BMP) signaling in human chondrosarcoma samples and concurrent downregulation of paternally expressed gene 10 (PEG10). PEG10 expression was suppressed by TGF-β signaling, and PEG10 interfered with the TGF-β and BMP-SMAD pathways in chondrosarcoma cells. However, the roles of PEG10 in bone tumors, including chondrosarcoma, remain unknown. Here, we report that PEG10 promotes SW1353 chondrosarcoma cell growth by preventing TGF-β1-mediated suppression. In contrast, PEG10 knockdown augments the TGF-β1-induced motility of SW1353 cells. Individually, TGF-β1 and PEG10 siRNA increase AKT phosphorylation, whereas an AKT inhibitor, MK2206, mitigates the effect of PEG10 silencing on cell migration. SW1353 cell invasion was enhanced by BMP-6, which was further increased by PEG10 silencing. The effect of siPEG10 was suppressed by inhibitors of matrix metalloproteinase (MMP). BMP-6 induced expression of MMP-1, -3, and -13, and PEG10 lentivirus or PEG10 siRNA downregulated or further upregulated these MMPs, respectively. PEG10 siRNA increased BMP-6-induced phosphorylation of p38 MAPK and AKT, whereas the p38 inhibitor SB203580 and MK2206 diminished SW1353 cell invasion by PEG10 siRNA. SB203580 and MK2206 impeded the enhancing effect of PEG10 siRNA on the BMP-6-induced expression of MMP-1, -3, and -13. Our findings suggest dual functions for PEG10: accelerating cell growth by suppressing TGF-β signaling and inhibiting cell motility and invasion by interfering with TGF-β and BMP signaling via the AKT and p38 pathways, respectively. Thus, PEG10 might be a molecular target for suppressing the aggressive phenotypes of chondrosarcoma cells.

Search of Allosteric Inhibitors and Associated Proteins of an AKT-like Kinase from Trypanosoma cruzi

Proteins associated to the PI3K/AKT/mTOR signaling pathway are widely used targets for cancer treatment, and in recent years they have also been evaluated as putative targets in trypanosomatids parasites, such as Trypanosoma cruzi. Here, we performed a virtual screening approach to find candidates that can bind regions on or near the Pleckstrin homology domain of an AKT-like protein in T. cruzi. The compounds were also evaluated in vitro. The in silico and experimental results allowed us to identify a set of compounds that can potentially alter the intracellular signaling pathway through the AKT-like kinase of the parasite; among them, a derivative of the pyrazolopyridine nucleus with an IC₅₀ of 14.25 ± 1.00 μM against amastigotes of T. cruzi. In addition, we built a protein–protein interaction network of T. cruzi to understand the role of the AKT-like protein in the parasite, and look for additional proteins that can be postulated as possible novel molecular targets for the rational design of compounds against T. cruzi.

Inhibition of mTORC2/RICTOR Impairs Melanoma Hepatic Metastasis

Mammalian target of rapamycin complex 2 (mTORC2) with its pivotal component rapamycin-insensitive companion of mTOR (RICTOR) is the major regulator of AKT phosphorylation and is increasingly implicated in tumor growth and progression. In cutaneous melanoma, an extremely aggressive and highly metastatic disease, RICTOR overexpression is involved in tumor development and invasiveness. Therefore, we investigated the impact of RICTOR inhibition in melanoma cells in vitro and in vivo with special emphasis on hepatic metastasis. Moreover, our study focused on the interaction of tumor cells and hepatic stellate cells (HSC) which play a crucial role in the hepatic microenvironment. In silico analysis revealed increased RICTOR expression in melanoma cells and tissues and indicated higher expression in advanced melanoma stages and metastases. In vitro, transient RICTOR knock-down via siRNA caused a significant reduction of tumor cell motility. Using a syngeneic murine splenic injection model, a significant decrease in liver metastasis burden was detected in vivo. Moreover, stimulation of melanoma cells with conditioned medium (CM) from activated HSC or hepatocyte growth factor (HGF) led to a significant induction of AKT phosphorylation and tumor cell motility. Blocking of RICTOR expression in cancer cells diminished constitutive and HGF-induced AKT phosphorylation as well as cell motility. Interestingly, RICTOR blockade also led to an abrogation of CM-induced effects on AKT phosphorylation and motility in melanoma cells. In conclusion, these results provide first evidence for a critical role of mTORC2/RICTOR in melanoma liver metastasis via cancer cell/HSC interactions.

Combination treatment of cancer cells with pan-Akt and pan-mTOR inhibitors: effects on cell cycle distribution, p-Akt expression level and radiolabelled-choline incorporation

Signal transduction pathways, which regulate cell growth and survival, are up-regulated in many cancers and there is considerable interest in their pharmaceutical modulation for cancer treatment. However inhibitors of single pathway components induce feedback mechanisms that overcome the growth moderating effect of the inhibitor. Combination treatments have been proposed to provide a more complete pathway inhibition. Here the effect of dual treatment of cancer cells with a pan-Akt and a pan-mTOR inhibitor was explored. Breast (SKBr3 and MDA-MB-468) and colorectal (HCT8) cancer cells were treated with the pan-Akt inhibitor MK2206 and pan-mTOR inhibitor AZD8055. Cytotoxic effect of the two drugs were determined using the MTT assay and the Combination Index and isobolomic analysis used to determine the nature of the interaction of the two drugs. Flow cytometry and western blot were employed to demonstrate drug effects on cell cycle distribution and phosph-Akt^ser473 expression. Radiolabelled ([methyl-³H]) Choline uptake was measured in control and drug-treated cells to determine the modulatory effects of the drugs on choline incorporation. The two drugs acted synergistically to inhibit the growth rate of each cancer cell line. Flow cytometry demonstrated G0/G1 blockade with MK2206 and AZD8055 which was greater when cells were treated with both drugs. The incorporation of [methyl-³H] choline was found be decreased to a greater extent in cells treated with both drugs compared with cells treated with either drug alone. Conclusions Pan-mTOR and pan-Akt inhibition may be highly effective in cancer treatment and measuring changes in choline uptake could be useful in detecting efficacious drug combinations.

Inhibition of miR-128-3p by Tongxinluo Protects Human Cardiomyocytes from Ischemia/reperfusion Injury via Upregulation of p70s6k1/p-p70s6k1

Background and Aims: Tongxinluo (TXL) is a multifunctional traditional Chinese medicine that has been widely used to treat cardiovascular and cerebrovascular diseases. However, no studies have explored whether TXL can protect human cardiomyocytes (HCMs) from ischemia/reperfusion (I/R) injury. Reperfusion Injury Salvage Kinase (RISK) pathway activation was previously demonstrated to protect the hearts against I/R injury and it is generally activated via Akt or (and) Erk 1/2, and their common downstream protein, ribosomal protein S6 kinase (p70s6k). In addition, prior studies proved that TXL treatment of cells promoted secretion of VEGF, which could be stimulated by the increased phosphorylation of one p70s6k subtype, p70s6k1. Consequently, we hypothesized TXL could protect HCMs from I/R injury by activating p70s6k1 and investigated the underlying mechanism.

Methods and Results: HCMs were exposed to hypoxia (18 h) and reoxygenation (2 h) (H/R), with or without TXL pretreatment. H/R reduced mitochondrial membrane potential, increased bax/bcl-2 ratios and cytochrome C levels and induced HCM apoptosis. TXL preconditioning reversed these H/R-induced changes in a dose-dependent manner and was most effective at 400 μg/mL. The anti-apoptotic effect of TXL was abrogated by rapamycin, an inhibitor of p70s6k. However, inhibitors of Erk1/2 (U0126) or Akt (LY294002) failed to inhibit the protective effect of TXL. TXL increased p70s6k1 expression and, thus, enhanced its phosphorylation. Furthermore, transfection of cardiomyocytes with siRNA to p70s6k1 abolished the protective effects of TXL. Among the micro-RNAs (miR-145-5p, miR-128-3p and miR-497-5p) previously reported to target p70s6k1, TXL downregulated miR-128-3p in HCMs during H/R, but had no effects on miR-145-5p and miR-497-5p. An in vivo study confirmed the role of the p70s6k1 pathway in the infarct-sparing effect of TXL, demonstrating that TXL decreased miR-128-3p levels in the rat myocardium during I/R. Transfection of HCMs with a hsa-miR-128-3p mimic eliminated the protective effects of TXL.

Conclusions: The miR-128-3p/p70s6k1 signaling pathway is involved in protection by TXL against HCM apoptosis during H/R. Overexpression of p70s6k1 is, therefore, a potential new strategy for alleviating myocardial reperfusion injury.

MYC Modulation around the CDK2/p27/SKP2 Axis

MYC is a pleiotropic transcription factor that controls a number of fundamental cellular processes required for the proliferation and survival of normal and malignant cells, including the cell cycle. MYC interacts with several central cell cycle regulators that control the balance between cell cycle progression and temporary or permanent cell cycle arrest (cellular senescence). Among these are the cyclin E/A/cyclin-dependent kinase 2 (CDK2) complexes, the CDK inhibitor p27^KIP1 (p27) and the E3 ubiquitin ligase component S-phase kinase-associated protein 2 (SKP2), which control each other by forming a triangular network. MYC is engaged in bidirectional crosstalk with each of these players; while MYC regulates their expression and/or activity, these factors in turn modulate MYC through protein interactions and post-translational modifications including phosphorylation and ubiquitylation, impacting on MYC's transcriptional output on genes involved in cell cycle progression and senescence. Here we elaborate on these network interactions with MYC and their impact on transcription, cell cycle, replication and stress signaling, and on the role of other players interconnected to this network, such as CDK1, the retinoblastoma protein (pRB), protein phosphatase 2A (PP2A), the F-box proteins FBXW7 and FBXO28, the RAS oncoprotein and the ubiquitin/proteasome system. Finally, we describe how the MYC/CDK2/p27/SKP2 axis impacts on tumor development and discuss possible ways to interfere therapeutically with this system to improve cancer treatment.