PKC-beta II expression has prognostic impact in nodal diffuse large B-cell lymphoma

Protein Kinase C (PKC) Isozymes as Diagnostic and Prognostic Biomarkers and Therapeutic Targets for Cancer

Protein kinase C (PKC) is a large family of calcium- and phospholipid-dependent serine/threonine kinases that consists of at least 11 isozymes. Based on their structural characteristics and mode of activation, the PKC family is classified into three subfamilies: conventional or classic (cPKCs; α, βI, βII, and γ), novel or non-classic (nPKCs; δ, ε, η, and θ), and atypical (aPKCs; ζ, ι, and λ) (PKCλ is the mouse homolog of PKCι) PKC isozymes. PKC isozymes play important roles in proliferation, differentiation, survival, migration, invasion, apoptosis, and anticancer drug resistance in cancer cells. Several studies have shown a positive relationship between PKC isozymes and poor disease-free survival, poor survival following anticancer drug treatment, and increased recurrence. Furthermore, a higher level of PKC activation has been reported in cancer tissues compared to that in normal tissues. These data suggest that PKC isozymes represent potential diagnostic and prognostic biomarkers and therapeutic targets for cancer. This review summarizes the current knowledge and discusses the potential of PKC isozymes as biomarkers in the diagnosis, prognosis, and treatment of cancers.

NADPH Oxidase 5 upregulation is associated with lymphoma aggressiveness

OBJECTIVES

Lymphomas are a heterogeneous set of malignant neoplasias of lymphoid B and NK/T mature and immature cells at various stages of differentiation. Genetic and molecular biology tools are used to appropriately classify the type and prognosis of the lymphomas, which have implications in therapeutic effectiveness. Among them, the nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) oxidase (NOX5) enzymes have been explored. This study analyzed the expression of NADPH oxidase 5 in lymphoma tissue according to the degree of tumor aggressiveness.

METHODS

Slides from 64 patients with lymphoma who had paraffin-embedded tissue available were reviewed by two independent, experienced pathologists. They classified tumors according to the WHO classification (2017). NOX5 expression in tissues was assessed by immunohistochemical staining using a tissue microarray. The assay was interpreted using a scoring system of 0, 1, 2, and 3, for cytoplasmic staining of NOX5 corresponding to negative, weak, intermediate, and strong staining, respectively. We compared the expression of NOX5 in patients with aggressive versus non-aggressive lymphomas.

RESULTS

NOX5 expression was positive in 100% (27/27) of aggressive lymphomas and in 19% (7/37) of non-aggressive ones. The seven patients with positive expression of NOX5 presented intermediate staining (2); strong staining (3) was observed only in tissues of aggressive lymphomas, and negative and weak staining (0 and 1) were observed only in non-aggressive lymphomas.

CONCLUSIONS

Aggressive lymphomas overexpress NOX5 protein. The higher NOX5 expression in aggressive lymphomas can suggest an involvement of this enzyme on the acquisition of an aggressive phenotype in lymphoid neoplasia.

Frontline rituximab, cyclophosphamide, doxorubicin, and prednisone with bortezomib (VR-CAP) or vincristine (R-CHOP) for non-GCB DLBCL

This phase 2 study evaluated whether substituting bortezomib for vincristine in frontline rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) therapy could improve efficacy in non-germinal center B-cell-like diffuse large B-cell lymphoma (non-GCB DLBCL), centrally confirmed by immunohistochemistry (Hans method). In total, 164 patients were randomized 1:1 to receive six 21-day cycles of rituximab 375 mg/m(2), cyclophosphamide 750 mg/m(2), and doxorubicin 50 mg/m(2), all IV day 1, prednisone 100 mg/m(2) orally days 1-5, plus either bortezomib 1.3 mg/m(2) IV days 1, 4, 8, 11 (rituximab, cyclophosphamide, doxorubicin, and prednisone with bortezomib [VR-CAP]; n = 84) or vincristine 1.4 mg/m(2) (maximum 2 mg) IV day 1 (R-CHOP; n = 80). There were no significant differences between VR-CAP and R-CHOP in complete response rate (64.5%, 66.2%; odds ratio [OR], 0.91; P = .80), overall response rate (93.4%, 98.6%; OR, 0.21; P = .11), progression-free survival (hazard ratio [HR], 1.12; P = .76), or overall survival (HR, 0.89; P = .75). Rates of grade ≥3 adverse events (AEs; 88%, 89%), serious AEs (38%, 34%), discontinuations due to AEs (7%, 3%), and deaths due to AEs (2%, 5%) were similar with VR-CAP and R-CHOP. Grade ≥3 peripheral neuropathy rates were 6% and 3%, respectively. VR-CAP did not improve efficacy vs R-CHOP in non-GCB DLBCL. This trial was registered at www.clinicaltrials.gov as #NCT01040871.

eIF6 anti-association activity is required for ribosome biogenesis, translational control and tumor progression

Here we discuss the function of eukaryotic initiation factor 6 (eIF6; Tif6 in yeast). eIF6 binds 60S ribosomal subunits and blocks their joining to 40S. In this context, we propose that eIF6 impedes unproductive 80S formation, namely, the formation of 80S subunits without mRNA. Genetic evidence shows that eIF6 has a dual function: in yeast and mammals, nucleolar eIF6 is necessary for the biogenesis of 60S subunits. In mammals, cytoplasmic eIF6 is required for insulin and growth factor-stimulated translation. In contrast to other translation factors, eIF6 activity is not under mTOR control. The physiological significance of eIF6 impacts on cancer and on inherited Shwachman-Bodian-Diamond syndrome. eIF6 is overexpressed in specific human tumors. In a murine model of lymphomagenesis, eIF6 depletion leads to a striking increase of survival, without adverse effects. Shwachman-Bodian-Diamond syndrome is caused by loss of function of SBDS protein. In yeast, point mutations of Tif6, the yeast homolog of eIF6, rescue the quasi-lethal effect due to the loss of the SBDS homolog, Sdo1. We propose that eIF6 is a node regulator of ribosomal function and predict that prioritizing its pharmacological targeting will be of benefit in cancer and Shwachman-Bodian-Diamond syndrome. This article is part of a Special Issue entitled: Translation and Cancer.

Protein Kinase C (PKC) Isozymes and Cancer

Protein kinase C (PKC) is a family of phospholipid-dependent serine/threonine kinases, which can be further classified into three PKC isozymes subfamilies: conventional or classic, novel or nonclassic, and atypical. PKC isozymes are known to be involved in cell proliferation, survival, invasion, migration, apoptosis, angiogenesis, and drug resistance. Because of their key roles in cell signaling, PKC isozymes also have the potential to be promising therapeutic targets for several diseases, such as cardiovascular diseases, immune and inflammatory diseases, neurological diseases, metabolic disorders, and multiple types of cancer. This review primarily focuses on the activation, mechanism, and function of PKC isozymes during cancer development and progression.

Open-label, single-arm, phase II study of enzastaurin in patients with follicular lymphoma

This open-label, phase II study investigated whether enzastaurin, a protein kinase C-beta (PKCβ) inhibitor, had activity in patients with grade 1 or 2 follicular lymphoma (FL). Adults with grade 1 or 2 FL who had no more than one prior treatment received oral enzastaurin continuously for up to 3 years. Of the 66 patients who received enzastaurin, 53 were evaluable for response. Overall response rate (ORR, primary efficacy endpoint) was 26.4% (3.8% complete response). Median (95% confidence interval) progression-free survival, time to response, and duration of response were 18.1 (11.5-28.3), 4.9 (2.8-8.1), and 22.3 (8.8-not applicable) months, respectively. In patients with tumour tissue available for biomarker analysis, ORRs in low versus high PKCβ2 expression groups were 41.7% and 8.3%, respectively (P = 0.041). The most common, mainly low-grade drug-related adverse events were fatigue (25.8%), diarrhoea (25.8%), nausea (18.2%), and chromaturia (18.2%). Four (6.1%) patients had Grade 3 toxicity and one (1.5%) patient had Grade 4 toxicity. Enzastaurin demonstrated limited clinical activity in grade 1 or 2 FL. Patients with low PKCβ2 expression in tumours had higher ORR than those with high PKCβ2 expression. Enzastaurin was well tolerated with mostly grade 1 or 2 toxicities. Further studies may be warranted in select patient populations.

Protein kinase C-beta inhibition induces apoptosis and inhibits cell cycle progression in acquired immunodeficiency syndrome-related non-hodgkin lymphoma cells

INTRODUCTION

Acquired immunodeficiency syndrome (AIDS)-related non-Hodgkin lymphoma (NHL) constitutes an aggressive variety of lymphomas characterized by increased extranodal involvement, relapse rate, and resistance to chemotherapy. Protein kinase C-beta (PKCβ) targeting showed promising results in preclinical and clinical studies involving a wide variety of cancers, but studies describing the role of PKCβ in AIDS-NHL are primitive if not lacking.

METHODS

In the present study, 3 AIDS-NHL cell lines were examined: 2F7 (AIDS-Burkitt lymphoma), BCBL-1 (AIDS-primary effusion lymphoma), and UMCL01-101 (AIDS-diffuse large B-cell lymphoma).

RESULTS

Immunoblot analysis demonstrated expression of PKCβ1 and PKCβ2 in 2F7 and UMCL01-101 cells, and PKCβ1 alone in BCBL-1 cells. The viability of 2F7 and BCBL-1 cells decreased significantly in the presence of PKCβ-selective inhibitor at half-maximal inhibitory concentration of 14 and 15 μmol/L, respectively, as measured by tetrazolium dye reduction assay. In contrast, UMCL01-101 cells were relatively resistant. As determined using flow cytometric deoxynucleotidyl transferase dUTP nick-end labeling assay with propidium iodide staining, the responsiveness of sensitive cells was associated with apoptotic induction and cell cycle inhibition. Protein kinase C-beta-selective inhibition was observed not to affect AKT phosphorylation but to induce a rapid and sustained reduction in the phosphorylation of glycogen synthase kinase-3 beta, ribosomal protein S6, and mammalian target of rapamycin in sensitive cell lines.

CONCLUSIONS

The results indicate that PKCβ plays an important role in AIDS-related NHL survival and suggest that PKCβ targeting should be considered in a broader spectrum of NHL. The observations in BCBL-1 were unexpected in the absence of PKCβ2 expression and implicate PKCβ1 as a regulator in those cells.

Influence of Tumor Location on the Composition of Immune Infiltrate and Its Impact on Patient Survival. Lessons from DCBCL and Animal Models

Diffuse large B-cell lymphomas (DLBCLs) are heterogeneous diseases growing either in nodal or extranodal locations including the central nervous system. One key issue is to decipher the prognostic value of immune cells infiltrating these tumors as DLBCLs developing in sanctuaries are more aggressive than nodal DLCBLs. Here, we summarize available data from the literature regarding the prognostic values of the different immune cell types found in these two types of human primary tumors (i.e., nodal vs brain). In nodal DLBCLs, memory T-cells and dendritic cells (DCs) densities are of good prognostic value whereas the influence of regulatory T-cells (Tregs) is less clear, in accordance with other types of cancers. Data for primary central nervous system lymphomas are very sparse for these cell types. By contrast, CD8⁺ cytotoxic T-cells seem to be of poor prognosis in either location. Their presence is linked to a loss of MHC expression providing a possible immune escape mechanism for these tumors. Clearly, tumor-associated macrophages are not associated to a significant prognostic value even in the brain where they highly infiltrate the tumor. Animal models indicate some specific features of lymphoma developing in sanctuaries by comparison to splenic location, with a higher infiltration of Tregs and less DCs, most likely reflecting the immunosuppressive context of these organs. All these informations illustrate the high impact of the immune system on patient outcome, encourage the pursuit of the immune environment’s analysis and of immunotherapeutic approaches.

MET/PKCbeta expression correlate with metastasis and inhibition is synergistic in lung cancer

Background:

Treatment of non-small cell lung cancer (NSCLC) remains a difficult task in oncology. Targeted inhibition of oncogenic proteins is promising. In this study, we evaluate the expression of MET and PKCß and in vitro effects of their inhibition using SU11274 and enzastaurin (LY317615.HCl) respectively.

Materials and Methods:

Patient samples were analyzed by immunohistochemistry for expression of PKCß and MET, utilizing tissue microarrays under an IRB-approved protocol. Expression of PKCß and MET was evaluated in cell lines by immunoblotting. Treatment with SU1174 against MET and enzastaurin against PKCß was performed in H1993 and H358 cell lines, and cell proliferation and downstream signaling (phosphorylation of MET, AKT, FAK, and GSK3ß) were evaluated by immunoblotting. Statistical analysis was performed using SPSS 16.0.

Results:

Expression of MET positively correlated with lymph node metastases (p=.0004), whereas PKCß showed no correlation (p=0.204). MET and PKCß expression were also strongly correlated (p<0.001). Expression of MET was observed in 5/8 cell lines (H358, H1703, A549, H1993, H2170; absent from H522, H661, or SW1573), whereas PKCß expression was observed in 8/8 cell lines. Cell proliferation was significantly impaired by treatment with SU11274 and enzastaurin, and their effects were synergistic in combination (CI=0.32 and 0.09). Phosphorylation of MET, FAK, AKT, and GSK3ß were strongly inhibited with both agents in combination.

Conclusions:

Concomitant inhibition of MET and PKCß significantly increased cytotoxicity in vitro against NSCLC, disrupting important downstream signaling pathways. Further evaluation in animal models is warranted.

Impairment of cytoplasmic eIF6 activity restricts lymphomagenesis and tumor progression without affecting normal growth

Eukaryotic Initiation Factor 6 (eIF6) controls translation by regulating 80S subunit formation. eIF6 is overexpressed in tumors. Here, we demonstrate that eIF6 inactivation delays tumorigenesis and reduces tumor growth in vivo. eIF6(+/-) mice resist to Myc-induced lymphomagenesis and have prolonged tumor-free survival and reduced tumor growth. eIF6(+/-) mice are also protected by p53 loss. Myc-driven lymphomas contain PKCβII and phosphorylated eIF6; eIF6 is phosphorylated by tumor-derived PKCβII, but not by the eIF4F activator mTORC1. Mutation of PKCβII phosphosite of eIF6 reduces tumor growth. Thus, eIF6 is a rate-limiting controller of initiation of translation, able to affect tumorigenesis and tumor growth. Modulation of eIF6 activity, independent from eIF4F complex, may lead to a therapeutical avenue in tumor therapy.

A novel bisindolymaleimide derivative (WK234) inhibits proliferation and induces apoptosis through the protein kinase Cβ pathway, in chronic myelogenous leukemia K562 cells

WK234, a novel bisindolymaleimide derivative, was designed as a protein kinase Cβ (PKCβ) inhibitor. The objective of this study was to evaluate the anti-tumor activity of WK234 in the human chronic myelogenous leukemia (CML) K562 cell line and to investigate possible mechanisms of its action. The results show that WK234 inhibited K562 cell proliferation in a time- and dose-dependent manner. WK234 increased cytochrome C release and caspase-3 cleavage, which indicates that it induced apoptosis via mitochondria- and caspase-mediated pathways. Western blotting showed that PKCβ1, PKCβ2, and their phosphorylation levels were effectively decreased after 2-4 h of WK234 treatment. Meanwhile the phosphorylation status of PKCβ downstream proteins, glycogen synthase kinase 3α/β (GSK3α/β) and extracellular signal-regulated kinase (ERK), were inhibited. WK234 blocked phorbol myristate acetate (PMA)-induced Ser(660) phosphorylation of PKCβ2 located at the cell membrane, and increased Ser(660) PKCβ2 expression within the cytoplasm and the nucleus. These results indicate that WK234 inhibited cell proliferation and induced apoptosis through suppressing the PKCβ signal pathway. WK234 might be a promising candidate for the treatment of CML.

Apoptotic induction in B-cell acute lymphoblastic leukemia cell lines treated with a protein kinase Cβ inhibitor

B-cell acute lymphoblastic leukemia (B-ALL) in adults exhibits a 5-year disease-free survival rate of only 25-40% after currently available treatment. Protein kinase Cβ (PKCβ) is under active consideration as a rational therapeutic target in several B-cell malignancies, but studies of its possible utility in B-ALL are lacking. Expression of PKCβ1 and PKCβ2 isoforms was demonstrated in five B-ALL cell lines characterized by distinctive chromosomal translocations, and sensitivity to PKCβ-selective inhibition was examined. Inhibitor treatment resulted in a dose-dependent reduction in viability in all cell lines, although pro-B ALL with t(4;11)(q21;q23) was most sensitive. Apoptotic induction was evident after 24-48 h of treatment, and an inhibition of cell cycle progression was detected in one cell line. Treatment resulted in a rapid induction of poly(ADP-ribose) polymerase (PARP) cleavage, indicating caspase-3-mediated apoptosis, and a rapid reduction in phosphorylation of AKT and its downstream target glycogen synthase kinase 3β (GSK3β). These results indicate that PKCβ targeting should be considered as a potential treatment option in B-ALL.

Prognostic impact of protein kinase C beta II expression in R-CHOP-treated diffuse large B-cell lymphoma patients

Development of targeted agents for the treatment of diffuse large B-cell lymphoma includes clinical evaluation of enzastaurin, an agent that suppresses signaling through protein kinase C-beta and AKT pathways. To determine whether protein kinase C-beta expression has prognostic significance for diffuse large B-cell lymphoma patients treated with immunochemotherapy, we analyzed the expression of protein kinase C-beta II, BCL-2 and cell of origin immunohistochemically from pretreatment samples of 95 diffuse large B-cell lymphoma patients. All patients received rituximab with CHOP or CHOEP. According to Kaplan-Meier analyses, overall survival at 3 years was better among the patients with low than high protein kinase C-beta II protein levels (94 vs 76%, P=0.036). The prognostic value of protein kinase C-beta II expression on survival was seen in the patients with low and high International Prognostic Index risk groups, and in all molecular entities. Gene expression data from an independent set of 233 diffuse large B-cell lymphoma patients treated with a combination of rituximab and CHOP-like chemotherapy was analyzed in comparison. Accordingly, a better 3-year overall survival was observed among the subgroup with low protein kinase C-beta II mRNA levels (84 vs 68%, P=0.005). In multivariate analysis with cell of origin, protein kinase C-beta II mRNA expression remained as an independent predictor for overall survival. Together, the data show that protein kinase C-beta II expression has prognostic significance in diffuse large B-cell lymphoma patients treated with immunochemotherapy.

Protein kinase C-beta II expression in diffuse large B-cell lymphoma predicts for inferior outcome of anthracycline-based chemotherapy with and without rituximab

Protein kinase C-beta II (PKC-beta II) expression has been reported to indicate inferior prognosis in diffuse large B-cell lymphoma (DLBCL) treated with anthracycline-based chemotherapy. This study compared prognostic significance of immunohistochemically determined PKC-beta II expression in de novo DLBCL treated with cyclophosphamide, doxorubicin, vincristine and prednisolone (CHOP) chemotherapy with and without rituximab. Outcomes were assessed in 80 consecutive patients, 48 treated with CHOP, and 32 with rituximab plus CHOP (R-CHOP). PKC-beta II expression correlated with inferior overall survival (OS) and progression-free survival (PFS) in CHOP-treated patients with low-risk International Prognostic Index (IPI) disease (0-2 adverse factors), but not in the overall patient group unstratified by IPI. PKC-beta II expression correlated with inferior OS and PFS in R-CHOP-treated patients unstratified by IPI status. Immunohistochemically demonstrated PKC-beta II expression thus identified patient subgroups where alternative treatment strategies may confer superior outcome. We now report that PKC-beta II expression has prognostic significance not only for CHOP therapy in low-risk IPI disease, but also for all patients receiving CHOP plus rituximab.

Evaluation of intra- and interobserver agreement and its clinical significance for scoring bcl-2 immunohistochemical expression in diffuse large B-cell lymphoma

Immunohistochemistry (IHC) has become an essential part of diagnosis and clinical research in lymphomas. There is considerable heterogeneity, however, in IHC findings regarding expression rate and positivity cut-offs, which creates a degree of uncertainty that has prevented its incorporation for prognostic purposes. The purpose of the present study was to assess intra- and interobserver agreement in scoring bcl-2 expression on IHC. The study materials were 81 diffuse large B-cell lymphomas. Slides were processed in the same laboratory, and were analyzed independently and in a blinded manner by four pathologists twice, at least 1 month apart. The positivity rates ranged from 31% to 41% in the first evaluation, and from 30% to 43% in the second evaluation. The two analyses by the same pathologist gave concordant results in 88-93% of cases (kappa = 0.71-0.83). Complete agreement among all observers varied from 72% to 79%. The experience of the observer did not influence intra-observer concordance. Cooperative analysis of discordant slides led to consensus in all cases. The variation observed in scoring bcl-2 expression is acceptable for use in lymphoma diagnosis and classification. The use of IHC stratification, however, for clinical decisions regarding treatment will require standardization and centralized consensus review, and must await the results of ongoing prospective trials.

Protein kinase C beta in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a disease with few therapeutic options. Protein kinase C beta (PKCbeta) is involved in important cellular functions. Enzastaurin (LY317615.HCl) is a novel inhibitor of PKC in clinical development. MPM cell lines (7) and patient tumor tissues (24) were evaluated for expression of PKCbeta by immunoblotting and immunohistochemistry, respectively. In-vitro cell growth assays were performed with enzastaurin with or without cisplatin. Cell migration was evaluated with the wound healing assay. Downstream signaling (survival and focal adhesion pathways) was studied by immunoblotting for related molecules in the presence of phorbol ester with or without enzastaurin. Expression for PKCbeta1 was seen in all cases, with a mean integrated optical density of 152.5 (standard deviation=95.47, n=24), whereas PKCbeta2 expression was less intense, with a mean integrated optical density of 11.45 (standard deviation=16.27, n=21). There was a trend toward lower overall survival among patients expressing above-median PKCbeta1 (P=0.064), but not PKCbeta2. Robust expression of PKCbeta1 and low expression of PKCbeta2 were observed in MPM cell lines. Treatment of MPM cell lines with enzastaurin revealed an IC50 of 5 micromol/l, and strong synergism was observed when combined with cisplatin. Wound healing assay revealed that treatment of H2461 cells with enzastaurin reduced migration by 59.2%. Enzastaurin treatment led to disruption of F-actin architecture. Downstream signaling showed reduced phosphorylation of AKT, FAK (focal adhesion kinase), p130Cas, S6 ribosomal protein, and paxillin. PKCbeta1 was expressed in the majority of MPM samples. Enzastaurin has preclinical activity against MPM, and exhibited synergism with cisplatin. PKCbeta inhibition in MPM might be able to reduce the invasiveness of MPM by affecting cytoskeletal function.