AKT as a therapeutic target in multiple myeloma

PHF19 before and post induction treatment possess favorable potency of reflecting treatment response to protease inhibitors, event-free survival, and overall survival in multiple myeloma patients

OBJECTIVE

Plant homeodomain finger protein 19 (PHF19) regulates hematopoietic stem cell differentiation and promotes multiple myeloma (MM) progression. This study intended to explore the potency of PHF19 at baseline and post induction treatment in estimating treatment response to protease inhibitors and survival in MM patients.

METHODS

This retrospective study screened 69 MM patients who received protease inhibitors with bone marrow (BM) samples available at both baseline and post induction treatment. Twenty healthy BM donors were included as healthy controls (HCs). PHF19 in plasma cells from BM was quantified by reverse transcription-quantitative polymerase chain reaction.

RESULTS

PHF19 at baseline and post induction treatment in MM patients were increased than in HCs. In MM patients, PHF19 was declined post induction treatment. Elevated PHF19 at baseline and post induction treatment were correlated with renal impairment, beta-2-microglobulin ≥5.5 mg/L, t (4; 14), higher international staging system (ISS) stage, and higher revised ISS (R-ISS) stage. Concerning treatment response, PHF19 at baseline and post induction treatment were negatively associated with complete response and overall response rate. Notably, abnormal PHF19 (above 95% quantile value of PHF19 in HCs) at baseline and post induction treatment were linked with shortened event-free survival (EFS) and overall survival (OS). After adjustment, abnormal PHF19 post induction treatment was independently related to shortened EFS (hazard ratio = 2.474) and OS (hazard ratio = 3.124).

CONCLUSION

PHF19 is aberrantly high and declines post induction therapy, which simultaneously reflects unfavorable treatment response to protease inhibitors as well as shorter EFS and OS in MM patients.

Differential cell cycle checkpoint evasion by PTEN germline mutations associated with dichotomous phenotypes of cancer versus autism spectrum disorder

Individuals with a PTEN germline mutation receive the molecular diagnosis of PTEN hamartoma tumor syndrome (PHTS). PHTS displays a complex spectrum of clinical phenotypes including harmartomas, predisposition to cancers, and autism spectrum disorder (ASD). Clear-cut genotype-phenotype correlations are yet to be established due to insufficient information on the PTEN function being impacted by mutations. To fill this knowledge gap, we compared functional impacts of two selected missense PTEN mutant alleles, G132D and M134R, each respectively being associated with distinct clinical phenotype, ASD or thyroid cancer without ASD using gene-edited human induced pluripotent stem cells (hiPSCs). In homozygous hiPSCs, PTEN expression was severely reduced by M134R mutation due to shortened protein half-life. G132D suppressed PTEN expression to a lesser extent than Μ134R mutation without altering protein half-life. When challenged with γ-irradiation, G132D heterozygous cells exited radiation-induced G2 arrest earlier than wildtype and M134R heterozygous hiPSCs despite the similar DNA damage levels as the latter two. Immunoblotting analyses suggested that γ-irradiation induced apoptosis in G132D heterozygous cells to lesser degrees than in the hiPSCs of other genotypes. These data suggest that ASD-associated G132D allele promotes genome instability by premature cell cycle reentry with incomplete DNA repair.

Brucein D imparts a growth inhibitory effect in multiple myeloma cells by abrogating the Akt-driven signaling pathway

The Akt signaling pathway is an oncogenic cascade activated in the bone marrow microenvironment of multiple myeloma (MM) cells and contributes to their uncontrolled proliferation. Abrogation of Akt signaling has been presented as one of the prime therapeutic targets in the treatment of MM. In the present report, we have investigated the effect of Brucein D (BD) on Akt-driven signaling events in MM cells. BD (300 nM) substantially inhibited cell viability and imparted growth-inhibitory effects in U266 cells as evidenced by cell viability assays and flow cytometric analysis. Effect of BD on cell viability was evaluated by MTT assay. Apoptotic cells and cell cycle arrest by BD were analyzed by flow cytometer. The results of the TUNEL assay and western blotting showed that BD induces apoptosis of MM cells by activating caspase-8 and 9 with subsequent reduction in the expression of antiapoptotic proteins (Bcl-2, Bcl-xl, survivin, cyclin D1, COX-2, VEGF, MMP-9). Analysis of activated kinases by Phospho-Kinase Array Kit revealed that Akt, p70S6K, HSP60, p53, and WNK1 were strongly expressed in untreated cells and BD treatment reversed this effect. Using transfection experiments, AKT depletion led to a decrease in phosphorylation of Akt, mTOR, p70S6K, and WNK. However, Akt overexpression led to increase in phosphorylation of these proteins. Depletion of Akt potentiated the apoptosis-inducing effect of BD whereas overexpression displayed resistance to BD-induced apoptosis suggesting the role of Akt in chemoresistance. Taken together, BD mitigates Akt-dependent signaling pathways in MM cells to impart its anticancer activity.

Inhibition of PI3K Class IA Kinases Using GDC-0941 Overcomes Cytoprotection of Multiple Myeloma Cells in the Osteoclastic Bone Marrow Microenvironment Enhancing the Efficacy of Current Clinical Therapeutics

Osteoclasts contribute to bone marrow (BM)-mediated drug resistance in multiple myeloma (MM) by providing cytoprotective cues. Additionally, 80% of patients develop osteolytic lesions, which is a major cause of morbidity in MM. Although targeting osteoclast function is critical to improve MM therapies, pre-clinical studies rarely consider overcoming osteoclast-mediated cytoprotection within the selection criteria of drug candidates. We have performed a drug screening and identified PI3K as a key regulator of a signalling node associated with resistance to dexamethasone lenalidomide, pomalidomide, and bortezomib mediated by osteoclasts and BM fibroblastic stromal cells, which was blocked by the pan-PI3K Class IA inhibitor GDC-0941. Additionally, GDC-0941 repressed the maturation of osteoclasts derived from MM patients and disrupted the organisation of the F-actin cytoskeleton in sealing zones required for bone degradation, correlating with decreased bone resorption by osteoclasts. In vivo, GDC-0941 improved the efficacy of dexamethasone against MM in the syngeneic GFP-5T33/C57-Rawji mouse model. Taken together, our results indicate that GDC-0941 in combination with currently used therapeutic agents could effectively kill MM cells in the presence of the cytoprotective BM microenvironment while inhibiting bone resorption by osteoclasts. These data support investigating GDC-0941 in combination with currently used therapeutic drugs for MM patients with active bone disease.

Cytotoxic Effects of the Schweinfurthin Analog 5′-Methylschweinfurthin G in Malignant Plasma Cells

<b><i>Introduction:</i></b> Multiple myeloma (MM) is a B plasma cell malignancy currently incurable, and novel therapeutics are needed. Evidences regarding the effect of natural compound schweinfurthins suggest that hematological cancers showed growth inhibitory effects to this family of compounds at single nanomolar concentrations. In this study, we evaluated the cytotoxicity of the schweinfurthin synthetic analog 5′-methylschweinfurthin G (MeSG) in MM cell lines, to better understand the validity of this compound as a therapeutic candidate for further studies in MM. <b><i>Methods:</i></b> MeSG toxicity against MM cell lines RPMI-8226, MM.1S, and H-929 was evaluated. Trypan blue exclusion and MTT assays measured cell viability and mitochondrial activity, respectively. Flow cytometry was performed to detect apoptotic mitochondria. Flow cytometry and Western blotting techniques were used to investigate apoptosis and to examine the cell cycle. Western blotting was used to determine AKT activation upon MeSG treatment. <b><i>Results:</i></b> We provide evidence that in all MM cells analyzed, MeSG exerts diverse cytotoxic effects. MeSG treatment of MM.1S and H-929, but not in RPMI-8226, causes a loss of mitochondria membrane potential. MeSG causes an arrest in G₂/M, especially in RPMI-8226, supported by decreased levels of cyclin-B1 and early increased levels of p21. Finally, there is a diverse response to the MeSG treatment for AKT phosphorylation. MM.1S and H-929 showed a marked decrease in AKT phosphorylation at earlier time points compared to the RPMI-8226 line. <b><i>Conclusions:</i></b> MeSG cytotoxicity has been confirmed in all of 3 cell lines studied. Results suggest an early event of increased reactive oxygen species, and/or involvement of cholesterol homeostasis via decreased AKT activation, both of which are currently under investigation.

The Potential of Novel Lipid Agents for the Treatment of Chemotherapy-Resistant Human Epithelial Ovarian Cancer

Simple Summary

Disease recurrence and chemotherapy resistance are the major causes of mortality for the majority of epithelial ovarian cancer (EOC) patients. Standard of care relies on cytotoxic drugs that induce a form of cell death called apoptosis. EOC cells can evolve to resist apoptosis. We developed drugs called glycosylated antitumor ether lipids (GAELs) that kill EOC cells by a mechanism that does not involve apoptosis. GAELs most likely induce cell death through a process called methuosis. Importantly, we showed that GAELs are effective at killing chemotherapy-resistant EOC cells in vitro and in vivo. Our work shows that the EOC community should begin to investigate methuosis-inducing agents as a novel therapeutic platform to treat chemotherapy-resistant EOC.

Abstract

Recurrent epithelial ovarian cancer (EOC) coincident with chemotherapy resistance remains the main contributor to patient mortality. There is an ongoing investigation to enhance patient progression-free and overall survival with novel chemotherapeutic delivery, such as the utilization of antiangiogenic medications, PARP inhibitors, or immune modulators. Our preclinical studies highlight a novel tool to combat chemotherapy-resistant human EOC. Glycosylated antitumor ether lipids (GAELs) are synthetic glycerolipids capable of killing established human epithelial cell lines from a wide variety of human cancers, including EOC cell lines representative of different EOC histotypes. Importantly, GAELs kill high-grade serous ovarian cancer (HGSOC) cells isolated from the ascites of chemotherapy-sensitive and chemotherapy-resistant patients grown as monolayers of spheroid cultures. In addition, GAELs were well tolerated by experimental animals (mice) and were capable of reducing tumor burden and blocking ascites formation in an OVCAR-3 xenograft model. Overall, GAELs show great promise as adjuvant therapy for EOC patients with or without chemotherapy resistance.

Involvement of the NF-κB and PI3K/Akt/mTOR pathways in cell death triggered by stypoldione, an o-quinone isolated from the brown algae Stypopodium zonale

Multiple myeloma (MM) is a clonal plasma cell malignancy that remains incurable to date. Thus, the aims of this study were to evaluate the involvement of the NF-κB and PI3K/Akt/mTOR pathways in the cytotoxicity of stypoldione, an o-quinone isolated from the brown algae Stypopodium zonale, in MM cells (MM1.S). The cytotoxic effect was evaluated in MM1.S cells and peripheral blood mononuclear cells (PBMCs) by MTT assay. The stypoldione reduced the cell viability of MM1.S cells in a concentration and time-dependent manner (IC50 in MM.1S from 2.55 to 5.38 μM). However, it was also cytotoxic to PBMCs, but at a lower range. Additionally, no significant hemolysis was observed even at concentration up to 10 times the IC50 . Apoptotic cell death was confirmed by cell morphology and Annexin V-FITC assay. Stypoldione induced intrinsic and extrinsic apoptosis by increasing FasR expression and reactive oxygen species (ROS) production, inverting the Bax/Bcl-2 ratio, and inducing ΔΨm loss, which resulted in AIF release and caspase-3 activation. It also increased Ki-67 and survivin expression and inhibited the NF-κB and PI3K/Akt/mTOR pathways. These results suggest that stypoldione is a good candidate for the development of new drugs for MM treatment.

Resibufogenin inhibits the malignant characteristics of multiple myeloma cells by blocking the PI3K/Akt signaling pathway

Resibufogenin (RBG) is an active ingredient of toad venom that also has antitumor potential. The present study aimed to investigate the role of RBG in multiple myeloma (MM) and the underlying action mechanism involving the PI3K/Akt signaling pathway. A human MM cell line, RPMI8226, was treated with RBG and/or insulin-like growth factor 1 (IGF-1; an activator of the PI3K/AKT signaling pathway). Cell viability and apoptosis were detected using Cell Counting Kit-8 and flow cytometry, respectively. Cell migration and invasion were detected using a Transwell assay. In addition, the epithelial-mesenchymal transition (EMT)-associated proteins (E-cadherin, N-cadherin and Vimentin) and the PI3K/AKT pathway-associated proteins [AKT, phosphorylated (p)-AKT, PI3K and p-PI3K] were measured using western blotting. RBG inhibited the viability, migration and invasion, and promoted the apoptosis of RPMI8226 cells in a dose-dependent manner. RBG at concentrations of 4 and 8 µM upregulated E-cadherin, and downregulated N-cadherin and Vimentin in RPMI8226 cells. RBG also decreased the protein expression of p-AKT and p-PI3K in a dose-dependent manner. In addition, the intervention of IGF-1 weakened the inhibitory effects of RBG on the malignant characteristics of MM cells. RBG-induced inhibition of EMT and the PI3K/AKT pathway were also weakened by IGF-1 treatment. In conclusion, RBG inhibited viability, migration, invasion and EMT, and promoted the apoptosis of MM cells by blocking the PI3K/AKT signaling pathway.

Extracellular vesicle proteomic analysis leads to the discovery of HDGF as a new factor in multiple myeloma biology

HDGF is secreted by and found in multiple myeloma cell extracellular vesicles; it activates AKT and sustains multiple myeloma cell growth.

HDGF polarizes naïve macrophages to an M1 phenotype and generates immunosuppressive M-MDSC.

Identifying factors secreted by multiple myeloma (MM) cells that may contribute to MM tumor biology and progression is of the utmost importance. In this study, hepatoma-derived growth factor (HDGF) was identified as a protein present in extracellular vesicles (EVs) released from human MM cell lines (HMCLs). Investigation of the role of HDGF in MM cell biology revealed lower proliferation of HMCLs following HDGF knockdown and AKT phosphorylation following the addition of exogenous HDGF. Metabolic analysis demonstrated that HDGF enhances the already high glycolytic levels of HMCLs and significantly lowers mitochondrial respiration, indicating that HDGF may play a role in myeloma cell survival and/or act in a paracrine manner on cells in the bone marrow (BM) tumor microenvironment (ME). Indeed, HDGF polarizes macrophages to an M1-like phenotype and phenotypically alters naïve CD14⁺ monocytes to resemble myeloid-derived suppressor cells which are functionally suppressive. In summary, HDGF is a novel factor in MM biology and may function to both maintain MM cell viability as well as modify the tumor ME.

Phosphocatalytic Kinome Activity Profiling of Apoptotic and Ferroptotic Agents in Multiple Myeloma Cells

Through phosphorylation of their substrate proteins, protein kinases are crucial for transducing cellular signals and orchestrating biological processes, including cell death and survival. Recent studies have revealed that kinases are involved in ferroptosis, an iron-dependent mode of cell death associated with toxic lipid peroxidation. Given that ferroptosis is being explored as an alternative strategy to eliminate apoptosis-resistant tumor cells, further characterization of ferroptosis-dependent kinase changes might aid in identifying novel druggable targets for protein kinase inhibitors in the context of cancer treatment. To this end, we performed a phosphopeptidome based kinase activity profiling of glucocorticoid-resistant multiple myeloma cells treated with either the apoptosis inducer staurosporine (STS) or ferroptosis inducer RSL3 and compared their kinome activity signatures. Our data demonstrate that both cell death mechanisms inhibit the activity of kinases classified into the CMGC and AGC families, with STS showing a broader spectrum of serine/threonine kinase inhibition. In contrast, RSL3 targets a significant number of tyrosine kinases, including key players of the B-cell receptor signaling pathway. Remarkably, additional kinase profiling of the anti-cancer agent withaferin A revealed considerable overlap with ferroptosis and apoptosis kinome activity, explaining why withaferin A can induce mixed ferroptotic and apoptotic cell death features. Altogether, we show that apoptotic and ferroptotic cell death induce different kinase signaling changes and that kinome profiling might become a valid approach to identify cell death chemosensitization modalities of novel anti-cancer agents.

Downregulation of ATXN3 Enhances the Sensitivity to AKT Inhibitors (Perifosine or MK-2206), but Decreases the Sensitivity to Chemotherapeutic Drugs (Etoposide or Cisplatin) in Neuroblastoma Cells

Background

Chemotherapy resistance is the major cause of failure in neuroblastoma (NB) treatment. ATXN3 has been linked to various types of cancer and neurodegenerative diseases; however, its roles in NB have not been established. The aim of our study was to explore the role of ATXN3 in the cell death induced by AKT inhibitor (perifosine or MK-2206) or chemotherapy drugs (etoposide or cisplatin) in NB cells.

Methods

The expressions of ATXN3 and BCL-2 family members were detected by Western blot. Cell survival was evaluated by CCK8, cell confluence was measured by IncuCyte, and apoptosis was detected by flow cytometry. AS and BE2 were treated with AKT inhibitors or chemotherapeutics, respectively.

Results

Downregulation of ATXN3 did not block, but significantly increased the perifosine/MK-2206-induced cell death. Among the BCL-2 family members, the expression of pro-apoptotic protein BIM and anti-proapoptotic protein Bcl-xl expression increased significantly when ATXN3 was down-regulated. Downregulation of BIM protected NB cells from the combination of perifosine/MK-2206 and ATXN3 downregulation. Downregulation of ATXN3 did not increase, but decrease the sensitivity of NB cells to etoposide/cisplatin, and knockdown of Bcl-xl attenuated this decrease in sensitivity.

Conclusion

Downregulation of ATXN3 enhanced AKT inhibitors (perifosine or MK-2206) induced cell death by BIM, but decreased the cell death induced by chemotherapeutic drugs (etoposide or cisplatin) via Bcl-xl. The expression of ATXN3 may be an indicator in selecting different treatment regimen.

PDK1 Inhibitor GSK-470 Exhibits Potent Anticancer Activity in a Pheochromocytoma PC12 Cell Tumor Model via Akt/mTOR Pathway

BACKGROUND

Phosphoinositide-Dependent Kinase 1 (PDK1) is now widely studied in malignant solid tumors. Researchers have previously revealed that targeting PDK1 is thought of as a promising anticancer treatment strategy. The aim of this study was designed to evaluate the anticancer activity of GSK-470, a novel and highly specific inhibitor of PDK1, in Pheochromocytoma (PCC) tumor model.

METHODS

PC12 cells were xenografted into nude mice to build PCC tumor model. Animals were treated with GSK-470 vs vehicle. Mean tumor volume was calculated and compared across groups. TUNEL was used to detect apoptosis. The effects of PDK1 inhibitor GSK-470 on activation of the Akt signaling and its downstream Akt/mTOR pathway in xenotransplant tumor tissues were examined by western bolt.

RESULTS

The mean tumor volume in GSK-470 group was significantly less than that in control group. TUNEL results found that cell apoptosis was markedly increased in GSK-470 group compared with the control group. The western bolt analysis showed that the phosphorylation of Akt at threonine 308 was significantly reduced in GSK-470 group. Also, GSK-470 strongly inhibited phosphorylation of mTOR on Ser2448, a marker for mTORC1 activity, as well as phosphorylation of p70S6K, best characterized targets of mTOR.

CONCLUSION

Our results showed that GSK-470 exhibited potent anticancer activity in PC12 tumor-bearing mice. Also, we found that this effect appeared to be mediated by the inhibition of the Akt/mTOR pathway. The present study once again provides new insights into the therapeutic effects of inhibiting PDK1 in the treatment of malignant PCC. Therefore, we propose that GSK-470 might be an effective therapeutic agent for the treatment of malignant PCC.

Pathway-Directed Therapy in Multiple Myeloma

Multiple Myeloma (MM) is a malignant plasma cell disorder with an unmet medical need, in particular for relapsed and refractory patients. Molecules within deregulated signaling pathways, including the RAS/RAF/MEK/ERK, but also the PI3K/AKT-pathway belong to the most promising evolving therapeutic targets. Rationally derived compounds hold great therapeutic promise to target tumor-specific abnormalities rather than general MM-associated vulnerabilities. This paradigm is probably best depicted by targeting mutated BRAF: while well-tolerated, remarkable responses have been achieved in selected patients by inhibition of BRAFV600E alone or in combination with MEK. Targeting of AKT has also shown promising results in a subset of patients as monotherapy or to resensitize MM-cells to conventional treatment. Approaches to target transcription factors, convergence points of signaling cascades such as p53 or c-MYC, are emerging as yet another exciting strategy for pathway-directed therapy. Informed by our increasing knowledge on the impact of signaling pathways in MM pathophysiology, rationally derived Precision-Medicine trials are ongoing. Their results are likely to once more fundamentally change treatment strategies in MM.

Metformin - its anti-cancer effects in hematologic malignancies

The main anti-diabetic effect of metformin mediated through stimulation of adenosine monophosphate (AMP)-activated protein kinase (AMPK) is the inhibition of hepatic gluconeogenesis and triggering glucose uptake in skeletal muscles. Additionally, some new pathways, besides the AMPK activation, were discovered, that can explain wide-range properties of metformin. All these properties are now attracting the attention of researchers in the fields other than diabetes and the drug has been reported to have anti-cancer, immunoregulatory and anti-aging effects. Among others, the beneficial effects of metformin in hematological disorders like leukemias, lymphomas, and multiple myeloma were reported. Despite a great progress in therapy, these diseases are still incurable in most cases. Thus, there is an urgent need to discover novel, less toxic and more effective drugs especially for older or chemotherapy-resistant patients. In this review article, the current findings on the anti-cancer effect of metformin together with underlying possible mechanisms in blood cancers are discussed. However. to evaluate precisely these promising effects of metformin, more studies are required, because many of the published results are preclinical.

Randomized, placebo‐controlled, phase 3 study of perifosine combined with bortezomib and dexamethasone in patients with relapsed, refractory multiple myeloma previously treated with bortezomib

Perifosine, an investigational, oral, synthetic alkylphospholipid, inhibits signal transduction pathways of relevance in multiple myeloma (MM) including PI3K/Akt. Perifosine demonstrated anti‐MM activity in preclinical studies and encouraging early‐phase clinical activity in combination with bortezomib. A randomized, double‐blind, placebo‐controlled phase 3 study was conducted to evaluate addition of perifosine to bortezomib‐dexamethasone in MM patients with one to four prior therapies who had relapsed following previous bortezomib‐based therapy. The primary endpoint was progression‐free survival (PFS). The study was discontinued at planned interim analysis, with 135 patients enrolled. Median PFS was 22.7 weeks (95% confidence interval 16·0–45·4) in the perifosine arm and 39.0 weeks (18.3–50.1) in the placebo arm (hazard ratio 1.269 [0.817–1.969]; P = .287); overall response rates were 20% and 27%, respectively. Conversely, median overall survival (OS) was 141.9 weeks and 83.3 weeks (hazard ratio 0.734 [0.380–1.419]; P = .356). Overall, 61% and 55% of patients in the perifosine and placebo arms reported grade 3/4 adverse events, including thrombocytopenia (26% vs 14%), anemia (7% vs 8%), hyponatremia (6% vs 8%), and pneumonia (9% vs 3%). These findings demonstrate no PFS benefit from the addition of perifosine to bortezomib‐dexamethasone in this study of relapsed/refractory MM, but comparable safety and OS.

The NEDD4-1 E3 ubiquitin ligase: A potential molecular target for bortezomib sensitivity in multiple myeloma

E3 ubiquitin ligases primarily determine the substrate specificity of the ubiquitin-proteasome system and play an essential role in the resistance to bortezomib in multiple myeloma (MM). Neural precursor cell-expressed developmentally downregulated gene 4-1 (NEDD4-1, also known as NEDD4) is a founding member of the NEDD4 family of E3 ligases and is involved in the proliferation, migration, invasion and drug sensitivity of cancer cells. In the present study, we investigated the role of NEDD4-1 in MM cells and explored its underlying mechanism. Clinically, low NEDD4-1 expression has been linked to poor prognosis in patients with MM. Functionally, NEDD4-1 knockdown (KD) resulted in bortezomib resistance in MM cells in vitro and in vivo. The overexpression (OE) of NEDD4-1, but not an enzyme-dead NEDD4-1-C867S mutant, had the opposite effect. Furthermore, the overexpression of NEDD4-1 in NEDD4-1 KD cells resensitized the cells to bortezomib in an add-back rescue experiment. Mechanistically, pAkt-Ser473 levels and Akt signaling were elevated and decreased by NEDD4-1 KD and OE, respectively. NEDD4-1 ubiquitinated Akt and targeted pAkt-Ser473 for proteasomal degradation. More importantly, the NEDD4-1 KD-induced upregulation of Akt expression sensitized MM cells to growth inhibition after treatment with an Akt inhibitor. Collectively, our results suggest that high NEDD4-1 levels may be a potential new therapeutic target in MM.

FCX-146, a potent allosteric inhibitor of Akt kinase in cancer cells: Lead optimization of the second-generation arylidene indanone scaffold

Akt, a serine-threonine protein kinase, is regulated by class-I PI3K signaling. Akt regulates a wide variety of cell processes including cell proliferation, survival, and angiogenesis through serine/threonine phosphorylation of downstream targets including mTOR and glycogen-synthase-kinase-3-beta (GSK3β). Targeting cancer-specific overexpression of Akt protein could be an efficient way to control cancer-cell proliferation. However, the ATP-competitive inhibitors are challenged by the highly conserved ATP binding site, and by competition with high cellular concentrations of ATP. We previously developed an allosteric inhibitor, 2-arylidene-4, 7-dimethyl indan-1-one (FXY-1) that showed promising activity against several lung cancer models. In this work, we designed a congeneric series of molecules based on FXY-1 and optimized lead based on computational, in vitro assays. Computational screening followed by enzyme-inhibition and cell-proliferation assays identified a derivative (FCX-146) as a new lead molecule with threefold greater potency than the parent compound. FCX-146 increased apoptosis in HL-60 cells, mediated in part through decreased expression of antiapoptotic Bcl-2 protein and increased levels of Bax-2 and Caspase-3. Molecular-dynamic simulations showed stable binding of FCX-146 to an allosteric (i.e., noncatalytic) pocket in Akt. Together, we propose FCX-146 as a potent second-generation arylidene indanone compound that binds to the allosteric pocket of Akt and potently inhibits its activation.

Metformin and Its Benefits for Various Diseases

Metformin is a widely used biguanide drug due to its safety and low cost. It has been used for over 60 years to treat type 2 diabetes at the early stages because of its outstanding ability to decrease plasma glucose levels. Over time, different uses of metformin were discovered, and the benefits of metformin for various diseases and even aging were verified. These diseases include cancers (e.g., breast cancer, endometrial cancer, bone cancer, colorectal cancer, and melanoma), obesity, liver diseases, cardiovascular disease, and renal diseases. Metformin exerts different effects through different signaling pathways. However, the underlying mechanisms of these different benefits remain to be elucidated. The aim of this review is to provide a brief summary of the benefits of metformin and to discuss the possible underlying mechanisms.

GL-V9 exerts anti-T cell malignancies effects via promoting lysosome-dependent AKT1 degradation and activating AKT1/FOXO3A/BIM axis

T-cell malignancies are characterized by the excessive proliferation of hematopoietic precursor cells of T-cell lineage lymphocytes in the bone marrow. Previous studies suggest that T-cell malignancies are usually accompanied by highly activated PI3K/AKT signaling which confers the ability of cancer cells to proliferate and survive. Here, we found that GL-V9, a newly synthesized flavonoid compound, had a potent to inhibit the activation of AKT1 and induce the cell apoptosis in T-cell malignancies including cell lines and primary lymphoblastic leukemia. Results showed that GL-V9-induced degradation of AKT1 blocked PI3K/AKT1 signaling and the degradation of AKT1 could be reversed by NH₄Cl, an inhibitor of lysosomal function. Inhibiting AKT1 promoted dephosphorylation of FOXO3A and its nuclear translocation. We further demonstrated that GL-V9-induced apoptosis effects were dependent on the binding of FOXO3A to the BIM promoter, resulting in the production of BH3-only protein BIM. Moreover, GL-V9 showed a more persistent and stronger apoptosis induction effects than pharmacologic PI3K inhibitor. The in vivo studies also verified that GL-V9 possessed the anti-tumor effects by reducing the leukemic burden in T-ALL-bearing BALB/c nude mice. In conclusion, our study provides a new insight into the mechanism of GL-V9-induced apoptosis, suggesting the potency of GL-V9 to be a promising agent against T-cell malignancies.

Alkylphospholipids are Signal Transduction Modulators with Potential for Anticancer Therapy

BACKGROUND

Alkylphospholipids (APLs) are synthetically derived from cell membrane components, which they target and thus modify cellular signalling and cause diverse effects. This study reviews the mechanism of action of anticancer, antiprotozoal, antibacterial and antiviral activities of ALPs, as well as their clinical use.

METHODS

A literature search was used as the basis of this review.

RESULTS

ALPs target lipid rafts and alter phospholipase D and C signalling cascades, which in turn will modulate the PI3K/Akt/mTOR and RAS/RAF/MEK/ERK pathways. By feedback coupling, the SAPK/JNK signalling chain is also affected. These changes lead to a G2/M phase cell cycle arrest and subsequently induce programmed cell death. The available knowledge on inhibition of AKT phosphorylation, mTOR phosphorylation and Raf down-regulation renders ALPs as attractive candidates for modern medical treatment, which is based on individualized diagnosis and therapy. Corresponding to their unusual profile of activities, their side effects result from cholinomimetic activity mainly and focus on the gastrointestinal tract. These aspects together with their bone marrow sparing features render APCs well suited for modern combination therapy. Although the clinical success has been limited in cancer diseases so far, the use of miltefosine against leishmaniosis is leading the way to better understanding their optimized use.

CONCLUSION

Recent synthetic programs generate congeners with the increased therapeutic ratio, liposomal formulations, as well as diapeutic (or theranostic) derivatives with optimized properties. It is anticipated that these innovative modifications will pave the way for the further successful development of ALPs.

Emerging protein kinase inhibitors for the treatment of multiple myeloma

Introduction: Significant advances have been made during the last two decades in terms of new therapeutic options but also of innovative approaches to diagnosis and management of multiple myeloma (MM). While patient survival has been significantly prolonged, most patients relapse. Including the milestone approval of the first kinase inhibitor imatinib mesylate for CML in 2001, 48 small molecule protein kinase (PK) inhibitors have entered clinical practice until now. However, no PK inhibitor has been approved for MM therapy yet. Areas covered: This review article summarizes up-to-date knowledge on the pathophysiologic role of PKs in MM. Derived small molecules targeting receptor tyrosine kinases (RTKs), the Ras/Raf/MEK/MAPK- pathway, the PI3K/Akt/mTOR- pathway as well as Bruton tyrosine kinase (BTK), Aurora kinases (AURK), and cyclin-dependent kinases (CDKs) are most promising. Preclinical as well as early clinical data focusing on these molecules will be presented and critically reviewed. Expert opinion: Current MM therapy is directed against general vulnerabilities. Novel therapeutic strategies, inhibition of PKs in particular, are directed to target tumor-specific driver aberrations such as genetic abnormalities and microenvironment-driven deregulations. Results of ongoing Precision Medicine trials with PK inhibitors alone or in combination with other agents are eagerly awaited and hold the promise of once more improving MM patient outcome.

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.

Metformin and blood cancers

Type 2 diabetes mellitus and cancer are correlated with changes in insulin signaling, a pathway that is frequently upregulated in neoplastic tissue but impaired in tissues that are classically targeted by insulin in type 2 diabetes mellitus. Many antidiabetes treatments, particularly metformin, enhance insulin signaling, but this pathway can be inhibited by specific cancer treatments. The modulation of cancer growth by metformin and of insulin sensitivity by anticancer drugs is so common that this phenomenon is being studied in hundreds of clinical trials on cancer. Many meta-analyses have consistently shown a moderate but direct effect of body mass index on the incidence of multiple myeloma and lymphoma and the elevated risk of leukemia in adults. Moreover, new epidemiological and preclinical studies indicate metformin as a therapeutic agent in patients with leukemia, lymphomas, and multiple myeloma. In this article, we review current findings on the anticancer activities of metformin and the underlying mechanisms from preclinical and ongoing studies in hematologic malignancies.

Bufalin Enhances the Cytotoxity of Human Multiple Myeloma Cells H929 to AKT Inhibitor MK2206: The Role of Protein AKT Phosphorylation

This study was purposed to investigate bufalin combined with AKT inhibitor MK2206 on growth inhibition and apoptosis of multiple myeloma cell line H929. CCK-8 assay and Annexin/PI staining were used to access the effects of bufalin and MK2206 in single or in combination, on inhibition of proliferation and induction of apoptosis in H929 cells. The apoptotic cells markedly increased after treated with nM bufalin and μM MK2206, including caspase3 and PARP1 proteins activated. The difference was statistically significant (P < 0.05) when compared with these drugs in single use. The apoptosis associated proteins and AKT/p-AKT proteins were determined by Western blots. We confirmed that AKT performed contradictory results in H929 with the two agents, and concluded p-AKT was vital in the synergy. The underlying mechanisms warrant further investigation.

The novel compound STK405759 is a microtubule-targeting agent with potent and selective cytotoxicity against multiple myeloma in vitro and in vivo

Despite advances in treatment, multiple myeloma (MM) remains incurable. Here we propose the use of STK405759, a novel microtubule targeting agent (MTA) and member of the furan metotica family for MM therapy.

STK405759 inhibited tubulin polymerization in a cell-free system and in myeloma cells. This molecule had potent cytotoxic activity against several MM cell lines and patient-derived MM cells. Moreover, STK405759 demonstrated cytotoxicity against drug-resistant myeloma cells that overexpressed the P-glycoprotein drug-efflux pump. STK405759 was not cytotoxic to peripheral blood mononuclear cells, including activated B and T lymphocytes. This compound caused mitotic arrest and apoptosis of myeloma cells characterized by cleavage of poly (ADP-ribose) polymerase-1 and caspase-8, as well as decreased protein expression of mcl-1. The combination of STK405759 with bortezomib, lenalidomide or dexamethasone had synergistic cytotoxic activity. In in vivo studies, STK405759-treated mice had significantly decreased MM tumor burden and prolonged survival compared to vehicle treated- mice.

These results provide a rationale for further evaluation of STK405759 as monotherapy or part of combination therapy for treating patients with MM.

TRIP13 impairs mitotic checkpoint surveillance and is associated with poor prognosis in multiple myeloma

AAA-ATPase TRIP13 is one of the chromosome instability gene recently established in multiple myeloma (MM), the second most common and incurable hematological malignancy. However, the specific function of TRIP13 in MM is largely unknown. Using sequential gene expression profiling, we demonstrated that high TRIP13 expression levels were positively correlated with progression, disease relapse, and poor prognosis in MM patients. Overexpressing human TRIP13 in myeloma cells prompted cell growth and drug resistance, and overexpressing murine TRIP13, which shares 93% sequence identity with human TRIP13, led to colony formation of NIH/3T3 fibroblasts in vitro and tumor formation in vivo. Meanwhile, the knockdown of TRIP13 inhibited myeloma cell growth, induced cell apoptosis, and reduced tumor burden in xenograft MM mice. Mechanistically, we observed that the overexpression of TRIP13 abrogated the spindle checkpoint and induced proteasome-mediated degradation of MAD2 primarily through the Akt pathway. Thus, our results demonstrate that TRIP13 may serve as a biomarker for MM disease development and prognosis, making it a potential target for future therapies.

Kinase inhibitors as potential agents in the treatment of multiple myeloma

Recent years have witnessed a dramatic increase in the number of therapeutic options available for the treatment of multiple myeloma (MM) - from immunomodulating agents to proteasome inhibitors to histone deacetylase (HDAC) inhibitors and, most recently, monoclonal antibodies. Used in conjunction with autologous hematopoietic stem cell transplantation, these modalities have nearly doubled the disease's five-year survival rate over the last three decades to about 50%. In spite of these advances, MM still is considered incurable as resistance and relapse are common. While small molecule protein kinase inhibitors have made inroads in the therapy of a number of cancers, to date their application to MM has been less than successful. Focusing on MM, this review examines the roles played by a number of kinases in driving the malignant state and the rationale for target development in the design of a number of kinase inhibitors that have demonstrated anti-myeloma activity in both in vitro and in vivo xenograph models, as well as those that have entered clinical trials. Among the targets and their inhibitors examined are receptor and non-receptor tyrosine kinases, cell cycle control kinases, the PI3K/AKT/mTOR pathway kinases, protein kinase C, mitogen-activated protein kinase, glycogen synthase kinase, casein kinase, integrin-linked kinase, sphingosine kinase, and kinases involved in the unfolded protein response.

CAR-T cells and combination therapies: What's next in the immunotherapy revolution?

Cancer immunotherapies are dramatically reshaping the clinical management of oncologic patients. For many of these therapies, the guidelines for administration, monitoring, and management of associated toxicities are still being established. This is especially relevant for adoptively transferred, genetically-modified T cells, which have unique pharmacokinetic properties, due to their ability to replicate and persist long-term, following a single administration. Furthermore, in the case of CAR-T cells, the use of synthetic immune receptors may impact signaling pathways involved in T cell function and survival in unexpected ways. We, herein, comment on the most salient aspects of CAR-T cell design and clinical experience in the treatment of solid tumors. In addition, we discuss different possible scenarios for combinations of CAR-T cells and other treatment modalities, with a special emphasis on kinase inhibitors, elaborating on the strategies to maximize synergism. Finally, we discuss some of the technologies that are available to explore the molecular events governing the success of these therapies. The young fields of synthetic and systems biology are likely to be major players in the advancement of CAR-T cell therapies, providing the tools and the knowledge to engineer patients' T lymphocytes into intelligent cancer-fighting micromachines.

VS-5584 mediates potent anti-myeloma activity via the upregulation of a class II tumor suppressor gene, RARRES3 and the activation of Bim

The PI3K/mTOR/AKT pathway is an integral regulator of survival and drug resistance in multiple myeloma (MM). VS-5584 was synthesized with dual-specific and equipotent activity against mTORC1/2 and all four Class I PI3K isoforms so as to durably inhibit this pathway. We show that VS-5584 is highly efficacious against MM cell lines even in the presence of IL-6 and IGF-1 and that this growth inhibition is partially dependent on Bim. Importantly, VS-5584 triggers apoptosis in patient cells with a favorable therapeutic index. Gene expression profiling revealed a VS-5584-induced upregulation of RARRES3, a class II tumor suppressor gene. MM patient databases, UAMS and APEX, show that RARRES3 is under-expressed in 11q13 subsets which correlates with the reduced effectiveness of VS-5584 in 11q13 cell lines. Silencing RARRES3 expression significantly rescues VS-5584-induced cell death and increases cyclin D2 expression but not cyclin D1 or other cyclins implying a role for RARRES3 in cell cycle arrest. In vivo, VS-5584 significantly reduces the tumor burden of MM mouse xenografts. We further identified that VS-5584 synergised with Dexamethasone, Velcade, and exceptionally so with HDAC inhibitor, Panobinostat. Interestingly, this was consistently observed in several patient samples, proposing a promising novel clinical strategy for combination treatment especially in relapsed/refractory patients.

pH-Sensitive Nano-Complexes Overcome Drug Resistance and Inhibit Metastasis of Breast Cancer by Silencing Akt Expression

The therapy of breast cancer is encumbered by drug resistance and metastasis, which can be due to a defective PI3K/AKT/mTOR signaling pathway. This study was aimed at improving the anti-cancer effect of the chemotherapeutic agent paclitaxel (PTX) on the drug resistant and metastatic breast cancer by co-delivering PTX and a siRNA, siAkt, directed at silencing the Akt expression.

Methods: The pH-sensitive amphiphilic polymer, poly [(1,4-butanediol)-diacrylate-β-N, N-diisopropylethylenediamine]-polyethyleneimine (BDP) was synthesized. The PTX-loaded BDP micelle/siAkt nano-complex (PMA) was prepared and characterized. The cellular uptake, cytotoxicity, RNA interference efficiency, biodistribution, pharmacokinetics, pharmacodynamics, and biocompatibility of PMA in the murine metastatic breast cancer 4T1 cells and the 4T1 tumor-bearing mice were evaluated.

Results: PMA was stable at the neutral as well as tumor extracellular pH and released the drugs in the intra-endo/lysosome acidic environment. In 4T1 cells, the RNA interference against the Akt gene down-regulated the expression of Akt and P-glycoprotein and up-regulated the expression of Caspase-3. The down-regulated P-gp inhibits the efflux of PTX thereby increasing its intracellular concentration, improving the cytotoxicity, and inhibiting the migration and invasion of 4T1 cells. In the 4T1 tumor-bearing mice, co-delivery of PTX and siAkt by PMA achieved a tumor inhibiting rate of 94.1% and suppressed 96.8% lung metastases. PMA did not cause pathological lesions in normal organs.

Conclusion: PMA, by virtue of overcoming drug resistance and simultaneously restraining lung metastasis, might be an efficient drug delivery system for the therapy of breast cancer.

Inactivation of CK1α in multiple myeloma empowers drug cytotoxicity by affecting AKT and β-catenin survival signaling pathways

Recent evidence indicates that protein kinase CK1α may support the growth of multiple myeloma (MM) plasma cells. Here, by analyzing a large cohort of MM cases, we found that high CK1α mRNA levels are virtually associated with all MM patients. Moreover, we provided functional evidence that CK1α activity is essential for malignant plasma cell survival even in the protective niche generated by co-cultures with bone marrow stromal cells. We demonstrated that CK1α inactivation, while toxic for myeloma cells, is dispensable for the survival of healthy B lymphocytes and stromal cells. Disruption of CK1α function in myeloma cells resulted in decreased Mdm2, increased p53 and p21 and reduced expression of β-catenin and AKT. These effects were mediated partially by p53 and caspase activity. Finally, we discovered that CK1α inactivation enhanced the cytotoxic effect of both bortezomib and lenalidomide. Overall, our study supports a role for CK1α as a potential therapeutic target in MM in combination with proteasome inhibitors and/or immunomodulatory drugs.

MK2206 enhances the cytocidal effects of bufalin in multiple myeloma by inhibiting the AKT/mTOR pathway

Despite the development of promising cancer therapeutic drugs, multiple myeloma (MM) remains an incurable disease. Bufalin is a bufanolide steroid compound of the traditional Chinese medicine Chan Su that was previously shown to exert growth suppression effects on myeloma cell lines. Previous studies conducted by our group demonstrated that bufalin activated the AKT/mTOR pathway in myeloma cells, which is considered an essential pathway to disease progression and is related to drug resistance in MM. In view of the significant role of AKT in MM, the allosteric AKT inhibitor MK2206 was selected in order to enhance the antitumor effects of bufalin in different MM cell lines (NCI-H929, U266, LP-1 and RPMI8226). The data indicated that MK2206 enhanced the cytotoxicity of bufalin in MM cells, via the suppression of cellular proliferation and the induction of apoptosis, as demonstrated by cleavage of apoptosis-related proteins. This effect was further noted in the presence of exogenous interleukin-6 and/or following the co-culture of MM cells with bone marrow stromal cells (BMSC). This process was associated with the inhibition of the AKT/mTOR pathway. The combination of bufalin with MK2206 reduced the secretion of IL-6 in U266 cells. The combined treatment exhibited similar anti-MM effects in bortezomib-resistant cell lines (NCI-H929R, U266R). In addition to the in vitro cell line models, the synergistic effect was noted in primary MM cells and in MM xenografts of BALB-c and NOD-SCID mice. In conclusion, the data suggested that MK2206 significantly enhanced the cytocidal effects of bufalin in MM cells, regardless of the sensitivity to bortezomib, via the inhibition of the AKT/mTOR pathway. The study provided the basis of a promising treatment approach for MM.

The Role of Intracellular Signaling Pathways in the Pathogenesis of Multiple Myeloma and Novel Therapeutic Approaches

The introduction of novel agents, such as bortezomib, thalidomide, and lenalidomide, into daily practice has dramatically improved clinical outcomes and prolonged survival of patients with multiple myeloma (MM). However, despite these advanced clinical benefits, MM remains an incurable hematological malignancy. Therefore, development of new agents and novel therapeutic strategies is urgently needed. Recent advances toward understanding the mechanism of myeloma cell growth and drug resistance in the bone marrow milieu have provided clues for the development of next-generation agents aimed at improving patient outcomes. In this review article, we discuss new possible agents for the treatment of MM based on recent advances in the understanding of signaling pathways in myeloma cells.

CG13250, a novel bromodomain inhibitor, suppresses proliferation of multiple myeloma cells in an orthotopic mouse model

Multiple myeloma (MM) is characterized by the clonal proliferation of neoplastic plasma cells. Despite a stream of new molecular targets based on better understanding of the disease, MM remains incurable. Epigenomic abnormalities contribute to the pathogenesis of MM. bromodomain 4 (BRD4), a member of the bromodomain and extraterminal (BET) family, binds to acetylated histones during M/G1 transition in the cell cycle promoting progression to S phase. In this study, we investigated the effects of a novel BET inhibitor CG13250 on MM cells. CG13250 inhibited ligand binding to BRD4 in a dose-dependent manner and with an IC₅₀ value of 1.1 μM. It inhibited MM proliferation in a dose-dependent manner and arrested cells in G1, resulting in the induction of apoptosis through caspase activation. CG13250 inhibited the binding of BRD4 to c-MYC promoter regions suppressing the transcription of the c-MYC gene. Administered in vivo, CG13250 significantly prolonged survival of an orthotopic MM-bearing mice. In conclusion, CG13250 is a novel bromodomain inhibitor that is a promising molecular targeting agent against MM.

Renal Toxicities of Novel Agents Used for Treatment of Multiple Myeloma

Survival for patients with multiple myeloma has significantly improved in the last decade in large part due to the development of proteasome inhibitors and immunomodulatory drugs. These next generation agents with novel mechanisms of action as well as targeted therapies are being used both in the preclinical and clinical settings for patients with myeloma. These agents include monoclonal antibodies, deacetylase inhibitors, kinase inhibitors, agents affecting various signaling pathways, immune check point inhibitors, and other targeted therapies. In some cases, off target effects of these therapies can lead to unanticipated effects on the kidney that can range from electrolyte disorders to AKI. In this review, we discuss the nephrotoxicities of novel agents currently in practice as well as in development for the treatment of myeloma.

The Impact of Chemical Probes in Drug Discovery: A Pharmaceutical Industry Perspective

Chemical probes represent an important component of both academic and pharmaceutical drug discovery research. As a complement to prior reviews that have defined this scientific field, we aim to provide an industry perspective on the value of having high-quality chemical probes throughout the course of preclinical research. By studying examples from the internal Merck pipeline, we recognize that these probes require significant collaborative investment to realize their potential impact in clarifying the tractability and translation of a given therapeutic target. This perspective concludes with recommendations for chemical probe discovery aimed toward maximizing their potential to identify targets that result in the successful delivery of novel therapeutics.

Novel agents in the treatment of multiple myeloma: a review about the future

Multiple myeloma (MM) is a disease that affects plasma cells and can lead to devastating clinical features such as anemia, lytic bone lesions, hypercalcemia, and renal disease. An enhanced understanding of MM disease mechanisms has led to new more targeted treatments. There is now a plethora of treatments available for MM. In this review article, our aim is to discuss many of the novel agents that are being studied or have recently been approved for the treatment of MM. These agents include the following: immunomodulators (pomalidomide), proteasome inhibitors (carfilzomib, marizomib, ixazomib, oprozomib), alkylating agents (bendamustine), AKT inhibitors (afuresertib), BTK inhibitors (ibrutinib), CDK inhibitors (dinaciclib), histone deacetylase inhibitors (panobinostat, rocilinostat, vorinostat), IL-6 inhibitors (siltuximab), kinesin spindle protein inhibitors (filanesib), monoclonal antibodies (daratumumab, elotuzumab, indatuximab, SAR650984), and phosphoinositide 3-kinase (PI3K) inhibitors.

Novel therapeutic strategies for multiple myeloma

Multiple myeloma (MM) is a plasma-cell malignancy which remains incurable despite the recent emergence of multiple novel agents. Importantly, recent genetic and molecular analyses have revealed the complexity and heterogeneity of this disease, highlighting the need for therapeutic strategies to eliminate all clones. Moreover, the bone marrow microenvironment, including stromal cells and immune cells, plays a central role in MM pathogenesis, promoting tumor cell growth, survival, and drug resistance. New classes of agents including proteasome inhibitors, immunomodulatory drugs, monoclonal antibodies, and histone deacetylase inhibitors have shown remarkable efficacy; however, novel therapeutic approaches are still urgently needed to further improve patient outcomes. In this review, we discuss the recent advances and future strategies to ultimately develop MM therapies with curative potential.

Loss of serum and glucocorticoid-regulated kinase 3 (SGK3) does not affect proliferation and survival of multiple myeloma cell lines

Multiple myeloma (MM) is a generally fatal plasma cell cancer that often shows activation of the phosphoinositide 3-kinase/Akt (PI3K/Akt) pathway. Targeted pharmacologic therapies, however, have not yet progressed beyond the clinical trial stage, and given the complexity of the PI3K/Akt signalling system (e.g. multiple protein isoforms, diverse feedback regulation mechanisms, strong variability between patients) it is mandatory to characterise its ramifications in order to better guide informed decisions about the best therapeutic approaches. Here we explore whether serum and glucocorticoid-regulated kinase 3 (SGK3), a potential downstream effector of PI3K, plays a role in oncogenic signalling in MM cells—either in concert with or independent of Akt. SGK3 was expressed in all MM cell lines and in all primary MM samples tested. Four MM cell lines representing a broad range of intrinsic Akt activation (very strong: MM.1s, moderate: L 363 and JJN-3, absent: AMO-1) were chosen to test the effects of transient SGK3 knockdown alone and in combination with pharmacological inhibition of Akt, PI3K-p110α, or in the context of serum starvation. Although the electroporation protocol led to strong SGK3 depletion for at least 5 days its absence had no substantial effect on the activation status of potential downstream substrates, or on the survival, viability or proliferation of MM cells in all experimental contexts tested. We conclude that it is unlikely that SGK3 plays a significant role for oncogenic signalling in multiple myeloma.