Deletion of Pim kinases elevates the cellular levels of reactive oxygen species and sensitizes to K-Ras-induced cell killing.

The Pim protein kinases contribute to transformation by enhancing the activity of oncogenic Myc and Ras, which drives significant metabolic changes during tumorigenesis. In this report, we demonstrate that mouse embryo fibroblasts (MEFs) lacking all three isoforms of Pim protein kinases, triple knockout (TKO), cannot tolerate the expression of activated K-Ras (K-Ras(G12V)) and undergo cell death. Transduction of K-Ras(G12V) into these cells markedly increased the level of cellular reactive oxygen species (ROS). The addition of N-acetyl cysteine attenuated ROS production and reversed the cytotoxic effects of K-Ras(G12V) in the TKO MEFs. The altered cellular redox state caused by the loss of Pim occurred as a result of lower levels of metabolic intermediates in the glycolytic and pentose phosphate pathways as well as abnormal mitochondrial oxidative phosphorylation. TKO MEFs exhibit reduced levels of superoxide dismutase (Sod), glutathione peroxidase 4 (Gpx4) and peroxiredoxin 3 (Prdx3) that render them susceptible to killing by K-Ras(G12V)-mediated ROS production. In contrast, the transduction of c-Myc into TKO cells can overcome the lack of Pim protein kinases by regulating cellular metabolism and Sod2. In the absence of the Pim kinases, c-Myc transduction permitted K-Ras(G12V)-induced cell growth by decreasing Ras-induced cellular ROS levels. These results demonstrate that the Pim protein kinases have an important role in regulating cellular redox, metabolism and K-Ras-stimulated cell growth.

Higher levels of antibodies to the tumour-associated antigen cyclin B1 in cancer-free individuals than in patients with breast cancer.

Cyclin B1 is a checkpoint protein that regulates cell division from G2 to the M phase. Studies in mice have shown that cyclin B1 vaccine-induced immunity significantly delayed or prevented the spontaneous cancer development later in life. We hypothesized that if these results showing a protective effect of anti-cyclin B1 antibodies could be extrapolated to the human condition, cancer-free individuals should have higher levels of endogenous antibodies than patients with cancers characterized by the over-expression of this tumour-associated antigen. To test this hypothesis, we characterized a large (1739 subjects) number of multi-ethnic patients with breast cancer (which over-expresses cyclin B1) and matched controls for anti-cyclin B1 immunoglobulin (Ig)G antibodies. Multivariate analyses, after adjusting for the covariates, showed that cancer-free individuals had significantly higher levels of naturally occurring IgG antibodies to cyclin B1 than patients with breast cancer (mean ± standard deviation: 148·0 ± 73·6 versus 126·1 ± 67·8 arbitrary units per ml; P < 0·0001). These findings may have important implications for cyclin B1-based immunotherapy against breast cancer and many other cyclin B1-over-expressing malignancies.

Racially restricted contribution of immunoglobulin Fcγ and Fcγ receptor genotypes to humoral immunity to human epidermal growth factor receptor 2 in breast cancer.

Tumour-associated antigen human epidermal growth factor receptor 2 (HER2) is over-expressed in 25-30% of breast cancer patients and is associated with poor prognosis. Naturally occurring anti-HER2 antibody responses have been described in patients with HER2 over-expressing tumours. There is significant interindividual variability in antibody responsiveness, but the host genetic factors responsible for this variability are poorly understood. The aim of the present investigation was to determine whether immunoglobulin genetic markers [GM (genetic determinants of γ chains)] and Fcγ receptor (FcγR) alleles contribute to the magnitude of natural antibody responsiveness to HER2 in patients with breast cancer. A total of 855 breast cancer patients from Japan and Brazil were genotyped for several GM and FcγR alleles. They were also characterized for immunoglobulin (Ig)G antibodies to HER2. In white subjects (n = 263), GM 23-carriers had higher levels of anti-HER2 antibodies than non-carriers of this allele (p = 0·004). At the GM 5/21 locus, the homozygotes for the GM 5 allele had higher levels of anti-HER2 antibodies than the other two genotypes (P = 0·0067). In black subjects (n = 42), FcγRIIa-histidine/histidine homozygotes and FcγRIIIa-phenylalanine/valine heterozygotes were associated with high antibody responses (P = 0·0071 and 0·0275, respectively). FcγR genotypes in white subjects and GM genotypes in black subjects were not associated with anti-HER2 antibody responses. No significant associations were found in other study groups. These racially restricted contributions of GM and FcγR genotypes to humoral immunity to HER2 have potential implications for immunotherapy of breast cancer.

Role for Prdx1 as a specific sensor in redox-regulated senescence in breast cancer.

Recent studies suggest that Peroxiredoxin 1 (Prdx1), in addition to its known H2O2-scavenging function, mediates cell signaling through redox-specific protein-protein interactions. Our data illustrate how Prdx1 specifically coordinates p38MAPK-induced signaling through regulating p38MAPKα phosphatases in an H2O2 dose-dependent manner. MAPK phosphatases (MKP-1 and/or MKP-5), which are known to dephosphorylate and deactivate the senescence-inducing MAPK p38α, belong to a group of redox-sensitive phosphatases (protein tyrosine phosphatases) characterized by a low pKa cysteine in their active sites. We found that Prdx1 bound to both MKP-1 and MKP-5, but dissociated from MKP-1 when the Prdx1 peroxidatic cysteine Cys52 was over-oxidized to sulfonic acid, which in turn resulted in MKP-1 oxidation-induced oligomerization and inactivity toward p38MAPKα. Conversely, over-oxidation of Prdx1-Cys52 was enhancing in the Prdx1:MKP-5 complex with increasing amounts of H2O2 concentrations and correlated with a protection from oxidation-induced oligomerization and inactivation of MKP-5 so that activation toward p38MAPK was maintained. Further examination of this Prdx1-specific mechanism in a model of reactive oxygen species-induced senescence of human breast epithelial cells revealed the specific activation of MKP-5, resulting in decreased p38MAPKα activity. Taken together, our data suggest that Prdx1 orchestrates redox signaling in an H2O2 dose-dependent manner through the oxidation status of its peroxidatic cysteine Cys52.

A latent modeling approach to genotype-phenotype relationships: maternal problem behavior clusters, prenatal smoking, and MAOA genotype.

This study illustrates the application of a latent modeling approach to genotype-phenotype relationships and gene × environment interactions, using a novel, multidimensional model of adult female problem behavior, including maternal prenatal smoking. The gene of interest is the monoamine oxidase A (MAOA) gene which has been well studied in relation to antisocial behavior. Participants were adult women (N = 192) who were sampled from a prospective pregnancy cohort of non-Hispanic, white individuals recruited from a neighborhood health clinic. Structural equation modeling was used to model a female problem behavior phenotype, which included conduct problems, substance use, impulsive-sensation seeking, interpersonal aggression, and prenatal smoking. All of the female problem behavior dimensions clustered together strongly, with the exception of prenatal smoking. A main effect of MAOA genotype and a MAOA × physical maltreatment interaction were detected with the Conduct Problems factor. Our phenotypic model showed that prenatal smoking is not simply a marker of other maternal problem behaviors. The risk variant in the MAOA main effect and interaction analyses was the high activity MAOA genotype, which is discrepant from consensus findings in male samples. This result contributes to an emerging literature on sex-specific interaction effects for MAOA.

ETS1 transcriptional activity is increased in advanced prostate cancer and promotes the castrate-resistant phenotype.

Advanced disease accounts for the majority of prostate cancer-related deaths and androgen deprivation therapy (ADT) is the standard of care for these patients. Many patients undergoing ADT become resistant to its effects and progress to castrate-resistant prostate cancer (CRPC). Current therapies for CRPC patients are inadequate, with progression-free survival rates as low as 2 months. The molecular events that promote CRPC are poorly understood. ETS (v-ets erythroblastosis virus E26 oncogene) transcription factors are regulators of carcinogenesis. Protein levels of the archetypical ETS factor, ETS1, are increased in clinical and latent prostate cancer relative to benign prostatic hyperplasia and normal prostate to promote multiple cancer-associated processes, such as energy metabolism, matrix degradation, survival, angiogenesis, migration and invasion. Our studies have found that ETS1 expression is highest in high-grade prostate cancer (Gleason 7 and above). Increased ETS1 expression and transcriptional activity promotes an aggressive and castrate-resistant phenotype in immortalized prostate cancer cells. Elevated AKT (v-akt murine thymoma viral oncogene homolog) activity was demonstrated to increase ETS1 protein levels specifically in castrate-resistant cells and exogenous ETS1 expression was sufficient to rescue invasive potential decreased by inhibition of AKT activity. Significantly, targeted androgen receptor activity altered ETS1 expression, which in turn altered the castrate-resistant phenotype. These data suggest a role for oncogenic ETS1 transcriptional activity in promoting aggressive prostate cancer and the castrate-resistant phenotype.