Innovative strategies for measuring kinase activity to accelerate the next wave of novel kinase inhibitors.

The development of protein kinase inhibitors (PKIs) has gained significance owing to their therapeutic potential for diseases like cancer. In addition, there has been a rise in refining kinase activity assays, each possessing unique biological and analytical characteristics crucial for PKI development. However, the PKI development pipeline experiences high attrition rates and approved PKIs exhibit unexploited potential because of variable patient responses. Enhancing PKI development efficiency involves addressing challenges related to understanding the PKI mechanism of action and employing biomarkers for precision medicine. Selecting appropriate kinase activity assays for these challenges can overcome these attrition rate issues. This review delves into the current obstacles in kinase inhibitor development and elucidates kinase activity assays that can provide solutions.

Novel kinome profiling technology reveals drug treatment is patient and 2D/3D model dependent in glioblastoma.

Glioblastoma is the deadliest brain cancer. One of the main reasons for poor outcome resides in therapy resistance, which adds additional challenges in finding an effective treatment. Small protein kinase inhibitors are molecules that have become widely studied for cancer treatments, including glioblastoma. However, none of these drugs have demonstrated a therapeutic activity or brought more benefit compared to the current standard procedure in clinical trials. Hence, understanding the reasons of the limited efficacy and drug resistance is valuable to develop more effective strategies toward the future. To gain novel insights into the method of action and drug resistance in glioblastoma, we established in parallel two patient-derived glioblastoma 2D and 3D organotypic multicellular spheroids models, and exposed them to a prolonged treatment of three weeks with temozolomide or either the two small protein kinase inhibitors enzastaurin and imatinib. We coupled the phenotypic evidence of cytotoxicity, proliferation, and migration to a novel kinase activity profiling platform (QuantaKinome™) that measured the activities of the intracellular network of kinases affected by the drug treatments. The results revealed a heterogeneous inter-patient phenotypic and molecular response to the different drugs. In general, small differences in kinase activation were observed, suggesting an intrinsic low influence of the drugs to the fundamental cellular processes like proliferation and migration. The pathway analysis indicated that many of the endogenously detected kinases were associated with the ErbB signaling pathway. We showed the intertumoral variability in drug responses, both in terms of efficacy and resistance, indicating the importance of pursuing a more personalized approach. In addition, we observed the influence derived from the application of 2D or 3D models in in vitro studies of kinases involved in the ErbB signaling pathway. We identified in one 3D sample a new resistance mechanism derived from imatinib treatment that results in a more invasive behavior. The present study applied a new approach to detect unique and specific drug effects associated with pathways in in vitro screening of compounds, to foster future drug development strategies for clinical research in glioblastoma.

Multiomics profiling of paired primary and recurrent glioblastoma patient tissues.

BACKGROUND: Despite maximal therapy with surgery, chemotherapy, and radiotherapy, glioblastoma (GBM) patients have a median survival of only 15 months. Almost all patients inevitably experience symptomatic tumor recurrence. A hallmark of this tumor type is the large heterogeneity between patients and within tumors itself which relates to the failure of standardized tumor treatment. In this study, tissue samples of paired primary and recurrent GBM tumors were investigated to identify individual factors related to tumor progression. METHODS: Paired primary and recurrent GBM tumor tissues from 8 patients were investigated with a multiomics approach using transcriptomics, proteomics, and phosphoproteomics. RESULTS: In the studied patient cohort, large variations between and within patients are observed for all omics analyses. A few pathways affected at the different omics levels partly overlapped if patients are analyzed at the individual level, such as synaptogenesis (containing the SNARE complex) and cholesterol metabolism. Phosphoproteomics revealed increased STMN1(S38) phosphorylation as part of ERBB4 signaling. A pathway tool has been developed to visualize and compare different omics datasets per patient and showed potential therapeutic drugs, such as abobotulinumtoxinA (synaptogenesis) and afatinib (ERBB4 signaling). Afatinib is currently in clinical trials for GBM. CONCLUSIONS: A large variation on all omics levels exists between and within GBM patients. Therefore, it will be rather unlikely to find a drug treatment that would fit all patients. Instead, a multiomics approach offers the potential to identify affected pathways on the individual patient level and select treatment options.

Analysis of NFATc1 amplification in T cells for pharmacodynamic monitoring of tacrolimus in kidney transplant recipients.

BACKGROUND: Therapeutic drug monitoring (TDM) of tacrolimus, based on blood concentrations, shows an imperfect correlation with the occurrence of rejection. Here, we tested whether measuring NFATc1 amplification, a member of the calcineurin pathway, is suitable for TDM of tacrolimus. MATERIALS AND METHODS: NFATc1 amplification was monitored in T cells of kidney transplant recipients who received either tacrolimus- (n = 11) or belatacept-based (n = 10) therapy. Individual drug effects on NFATc1 amplification were studied in vitro, after spiking blood samples of healthy volunteers with either tacrolimus, belatacept or mycophenolate mofetil. RESULTS: At day 30 after transplantation, in tacrolimus-treated patients, NFATc1 amplification was inhibited in CD4+ T cells expressing the co-stimulation receptor CD28 (mean inhibition 37%; p = 0.01) and in CD8+CD28+ T cells (29% inhibition; p = 0.02), while this was not observed in CD8+CD28- T cells or belatacept-treated patients. Tacrolimus pre-dose concentrations of these patients correlated inversely with NFATc1 amplification in CD28+ T cells (rs = -0.46; p < 0.01). In vitro experiments revealed that 50 ng/ml tacrolimus affected NFATc1 amplification by 58% (mean; p = 0.02). CONCLUSION: In conclusion, measuring NFATc1 amplification is a direct tool for monitoring biological effects of tacrolimus on T cells in whole blood samples of kidney transplant recipients. This technique has potential that requires further development before it can be applied in daily practice.

Differential T Cell Signaling Pathway Activation by Tacrolimus and Belatacept after Kidney Transplantation: Post Hoc Analysis of a Randomised-Controlled Trial.

Pharmacokinetic immunosuppressive drug monitoring poorly correlates with clinical outcomes after solid organ transplantation. A promising method for pharmacodynamic monitoring of tacrolimus (TAC) in T cell subsets of transplant recipients might be the measurement of (phosphorylated) p38MAPK, ERK1/2 and Akt (activated downstream of the T cell receptor) by phospho-specific flow cytometry. Here, blood samples from n = 40 kidney transplant recipients (treated with either TAC-based or belatacept (BELA)-based immunosuppressive drug therapy) were monitored before and throughout the first year after transplantation. After transplantation and in unstimulated samples, p-p38MAPK and p-Akt were inhibited in CD8+ T cells and p-ERK in CD4+ T cells but only in patients who received TAC-based therapy. After activation with PMA/ionomycin, p-p38MAPK and p-AKT were significantly inhibited in CD4+ and CD8+ T cells when TAC was given, compared to pre-transplantation. Eleven BELA-treated patients had a biopsy-proven acute rejection, which was associated with higher p-ERK levels in both CD4+ and CD8+ T cells compared to patients without rejection. In conclusion, phospho-specific flow cytometry is a promising tool to pharmacodynamically monitor TAC-based therapy. In contrast to TAC-based therapy, BELA-based immunosuppression does not inhibit key T cell activation pathways which may contribute to the high rejection incidence among BELA-treated transplant recipients.

pERK-dependent defective TCR-mediated activation of CD4+ T cells in end-stage renal disease patients.

BACKGROUND: Patients with end-stage renal disease (ESRD) have an impaired immune response with a prematurely aged T-cell system. Mitogen-activated protein kinases (MAPKs) including extracellular signal-regulated kinase (ERK) and p38, regulate diverse cellular programs by transferring extracellular signals into an intracellular response. T cell receptor (TCR)-induced phosphorylation of ERK (pERK) may show an age-associated decline, which can be reversed by inhibiting dual specific phosphatase (DUSP) 6, a cytoplasmic phosphatase with substrate specificity to dephosphorylate pERK. The aim of this study was to assess whether ESRD affects TCR-mediated signaling and explore possibilities for intervening in ESRD-associated defective T-cell mediated immunity. RESULTS: An age-associated decline in TCR-induced pERK-levels was observed in the different CD4+ (P < 0.05), but not CD8+, T-cell subsets from healthy individuals (HI). Interestingly, pERK-levels of CD4+ T-cell subsets from young ESRD patients were in between young and elderly HI. A differentiation-associated decline in TCR-induced ERK and p38 phosphorylation was observed in T cells, although TCR-induced p38 phosphorylation was not significantly affected by age and/or ESRD. Frequencies of TCR-induced CD69-expressing CD4+ T cells declined with age and were positively associated with pERK. In addition, an age-associated tendency of increased expression of DUSP6 was observed in CD4+ T cells of HI and DUSP6 expression in young ESRD patients was similar to old HI. Inhibition of DUSP6 significantly increased TCR-induced pERK-levels of CD4+ T cells in young and elderly ESRD patients, and elderly HI. CONCLUSIONS: TCR-mediated phosphorylation of ERK is affected in young ESRD patients consistent with the concept of premature immunological T cell ageing. Inhibition of DUSP6 specific for pERK might be a potential intervention enhancing T-cell mediated immunity in ESRD patients.

Pharmacodynamic Monitoring of Tacrolimus-Based Immunosuppression in CD14+ Monocytes After Kidney Transplantation.

BACKGROUND: Monocytes significantly contribute to ischemia-reperfusion injury and allograft rejection after kidney transplantation. However, the knowledge about the effects of immunosuppressive drugs on monocyte activation is limited. Conventional pharmacokinetic methods for immunosuppressive drug monitoring are not cell type-specific. In this study, phosphorylation of 3 signaling proteins was measured to determine the pharmacodynamic effects of immunosuppression on monocyte activation in kidney transplant patients. METHODS: Blood samples from 20 kidney transplant recipients were monitored before and during the first year after transplantation. All patients received induction therapy with basiliximab, followed by tacrolimus (TAC), mycophenolate mofetil, and prednisolone maintenance therapy. TAC whole-blood predose concentrations were determined using an antibody-conjugated magnetic immunoassay. Samples were stimulated with phorbol 12-myristate 13-acetate (PMA)/ionomycin, and phosphorylation of p38MAPK, ERK, and Akt in CD14 monocytes was quantified by phospho-specific flow cytometry. RESULTS: Phosphorylation of p38MAPK and Akt in monocytes of immunosuppressed recipients was lower after 360 days compared with before transplantation in the unstimulated samples [mean reduction in median fluorescence intensity 36%; range -28% to 77% for p-p38MAPK and 20%; range -22% to 53% for p-Akt; P < 0.05]. P-ERK was only decreased at day 4 after transplantation (mean inhibition 23%; range -52% to 73%; P < 0.05). At day 4, when the highest whole-blood predose TAC concentrations were measured, p-p38MAPK and p-Akt, but not p-ERK, correlated inversely with TAC (rs = -0.65; P = 0.01 and rs = -0.58; P = 0.03, respectively). CONCLUSIONS: Immunosuppressive drug combination therapy partially inhibits monocyte activation pathways after kidney transplantation. This inhibition can be determined by phospho-specific flow cytometry, which enables the assessment of the pharmacodynamic effects of immunosuppressive drugs in a cell type-specific manner.

Targeting the Monocyte-Macrophage Lineage in Solid Organ Transplantation.

There is an unmet clinical need for immunotherapeutic strategies that specifically target the active immune cells participating in the process of rejection after solid organ transplantation. The monocyte-macrophage cell lineage is increasingly recognized as a major player in acute and chronic allograft immunopathology. The dominant presence of cells of this lineage in rejecting allograft tissue is associated with worse graft function and survival. Monocytes and macrophages contribute to alloimmunity via diverse pathways: antigen processing and presentation, costimulation, pro-inflammatory cytokine production, and tissue repair. Cross talk with other recipient immune competent cells and donor endothelial cells leads to amplification of inflammation and a cytolytic response in the graft. Surprisingly, little is known about therapeutic manipulation of the function of cells of the monocyte-macrophage lineage in transplantation by immunosuppressive agents. Although not primarily designed to target monocyte-macrophage lineage cells, multiple categories of currently prescribed immunosuppressive drugs, such as mycophenolate mofetil, mammalian target of rapamycin inhibitors, and calcineurin inhibitors, do have limited inhibitory effects. These effects include diminishing the degree of cytokine production, thereby blocking costimulation and inhibiting the migration of monocytes to the site of rejection. Outside the field of transplantation, some clinical studies have shown that the monoclonal antibodies canakinumab, tocilizumab, and infliximab are effective in inhibiting monocyte functions. Indirect effects have also been shown for simvastatin, a lipid lowering drug, and bromodomain and extra-terminal motif inhibitors that reduce the cytokine production by monocytes-macrophages in patients with diabetes mellitus and rheumatoid arthritis. To date, detailed knowledge concerning the origin, the developmental requirements, and functions of diverse specialized monocyte-macrophage subsets justifies research for therapeutic manipulation. Here, we will discuss the effects of currently prescribed immunosuppressive drugs on monocyte/macrophage features and the future challenges.

The Effect of Tacrolimus and Mycophenolic Acid on CD14+ Monocyte Activation and Function.

Monocytes and macrophages play key roles in many disease states, including cellular and humoral rejection after solid organ transplantation (SOT). To suppress alloimmunity after SOT, immunosuppressive drug therapy is necessary. However, little is known about the effects of the immunosuppressive drugs tacrolimus and mycophenolic acid (MPA) on monocyte activation and function. Here, the effect of these immunosuppressants on monocytes was investigated by measuring phosphorylation of three intracellular signaling proteins which all have a major role in monocyte function: p38MAPK, ERK and Akt. In addition, biological functions downstream of these signaling pathways were studied, including cytokine production, phagocytosis and differentiation into macrophages. To this end, blood samples from healthy volunteers were spiked with diverse concentrations of tacrolimus and MPA. Tacrolimus (200 ng/ml) inhibited phosphorylation of p38MAPK by 30% (mean) in CD14+ monocytes which was significantly less than in activated CD3+ T cells (max 60%; p < 0.05). This immunosuppressive agent also partly inhibited p-AKT (14%). MPA, at a therapeutic concentration showed the strongest effect on p-AKT (27% inhibition). p-ERK was inhibited with a maximum of 15% after spiking with either tacrolimus or MPA. The production of IL-1ß and phagocytosis by monocytes were not affected by tacrolimus concentrations, whereas MPA did inhibit IL-1ß production by 50%. Monocyte/macrophage polarization was shifted to an M2-like phenotype in the presence of tacrolimus, while MPA increased the expression of M2 surface markers, including CD163 and CD200R, on M1 macrophages. These results show that tacrolimus and MPA do not strongly affect monocyte function, apart from a change in macrophage polarization, to a clinically relevant degree.

Targeting JAK/STAT Signaling to Prevent Rejection After Kidney Transplantation: A Reappraisal.

The profound involvement of cytokines in allograft rejection makes the molecules that control their actions, members of the Jak-Stat pathway, ideal targets for pharmacological intervention. Numerous studies have demonstrated that Jak3 is widely involved in the activation cascade and function of most immune cells. Tofacitinib, an oral Janus kinase inhibitor that targets Jak1/Jak3 dependent Stat activation, has been assessed as a substitute for calcineurin inhibitor therapy after low-to-moderate risk kidney transplantation in 3 randomized trials. Results using fixed-dose regimens showed a low incidence of rejection and better renal function with less interstitial fibrosis/tubular atrophy versus calcineurin inhibitor therapy. However, the safety profile of tofacitinib was poor, including increased incidences of cytomegalovirus disease, herpes zoster, BK virus, and nephropathy, which led to the discontinuation of its development for transplantation. High tofacitinib concentrations were independently associated with serious infection. Dosing according to exposure levels, coupled with pharmacodynamic monitoring based on phosphorylation of Stat5, could improve safety compared to the early fixed-dose regimens. Future studies could assess individualized dosing based on pharmacokinetic and pharmacodynamic monitoring. Additionally, because the increase of viral infections under tofacitinib may have been influenced by overlapping toxicity with concomitant mycophenolic acid, exploration of alternative adjunctive therapies (eg, a mammalian target of rapamycin inhibitor or belatacept) may demonstrate a better efficacy/safety profile. We believe that Jak inhibitors are a good and useful addition to the immunosuppressive armentarium for kidney transplant patients, and that new studies with personalized drug dosing, improved immune monitoring, and better patient selection should be performed.

Conversion to Once-Daily Tacrolimus Results in Increased p38MAPK Phosphorylation in T Lymphocytes of Kidney Transplant Recipients.

BACKGROUND: The once-daily formulation of tacrolimus (TAC(OD)) has been developed to overcome adherence problems. Conversion from the twice-daily TAC (TAC(BID)) formulation to TAC(OD) on a 1:1 basis, however, often leads to a decrease of TAC predose concentrations, which averages ∼15%. Switching between the two TAC formulations may thus influence drug efficacy and necessitates therapeutic drug monitoring. As an additional tool in transplantation diagnostics, phospho-specific flow cytometry was used to study the biological effects of conversion on p38MAPK phosphorylation, a kinase involved in T-lymphocyte activation. METHODS: Stable renal transplant recipients (n = 12), at least 1 year after their transplantation, were converted from TAC(BID) to TAC(OD) on 1:1 mg for mg base. Comedication consisted of mycophenolate mofetil (n = 10) and prednisolone (n = 3). TAC whole-blood predose concentrations were determined by immunoassay before and 3 months after conversion. P38MAPK phosphorylation was measured in T lymphocytes by whole-blood phospho-specific flow cytometry. RESULTS: Three months after conversion, no significant decreases in TAC predose concentrations (C0) were found (P = 0.54), whereas p38MAPK phosphorylation increased with 11.4% (P < 0.05) in CD4 and with 15.6% (P < 0.05) in CD8 T lymphocytes. The TAC C0 during treatment with TAC(BID) correlated inversely with p38MAPK phosphorylation in T lymphocytes (rs = -0.638; P < 0.05). CONCLUSIONS: These results suggest that the measurement of p38MAPK phosphorylation status in T lymphocytes is a sensitive method to determine the biological effects of TAC before and after conversion from TAC(BID) to TAC(OD). This method could be a more sensitive tool for therapeutic drug monitoring of TAC.