Use of a novel antigen expressing system to study the Salmonella enterica serovar Typhi protein recognition by T cells.

Salmonella enterica serovar Typhi (S. Typhi), the causative agent of the typhoid fever, is a pathogen of great public health importance. Typhoid vaccines have the potential to be cost-effective measures towards combating this disease, yet the antigens triggering host protective immune responses are largely unknown. Given the key role of cellular-mediated immunity in S. Typhi protection, it is crucial to identify S. Typhi proteins involved in T-cell responses. Here, cells from individuals immunized with Ty21a typhoid vaccine were collected before and after immunization and used as effectors. We also used an innovative antigen expressing system based on the infection of B-cells with recombinant Escherichia coli (E. coli) expressing one of four S. Typhi gene products (i.e., SifA, OmpC, FliC, GroEL) as targets. Using flow cytometry, we found that the pattern of response to specific S. Typhi proteins was variable. Some individuals responded to all four proteins while others responded to only one or two proteins. We next evaluated whether T-cells responding to recombinant E. coli also possess the ability to respond to purified proteins. We observed that CD4+ cell responses, but not CD8+ cell responses, to recombinant E. coli were significantly associated with the responses to purified proteins. Thus, our results demonstrate the feasibility of using an E. coli expressing system to uncover the antigen specificity of T-cells and highlight its applicability to vaccine studies. These results also emphasize the importance of selecting the stimuli appropriately when evaluating CD4+ and CD8+ cell responses.

Neoadjuvant therapy for localized prostate cancer: Examining mechanism of action and efficacy within the tumor.

OBJECTIVES: Efforts to improve the clinical outcome for patients with localized high-risk prostate cancer have led to the development of neoadjuvant systemic therapies. We review the different modalities of neoadjuvant therapies for localized prostate cancer and highlight emerging treatment approaches including immunotherapy and targeted therapy. METHODS: We performed a PubMed search of clinical trials evaluating preoperative systemic therapies for treating high-risk prostate cancer published after 2000, and those studies with the highest clinical relevance to current treatment approaches were selected for review. The database at clinicaltrials.gov was queried for neoadjuvant studies in high-risk prostate cancer, and those evaluating novel targeted therapies and immunotherapies are spotlighted here. RESULTS: Neoadjuvant chemotherapy has become standard of care for treating some malignancies, including breast and bladder cancers. In prostate cancer, preoperative hormonal therapy or chemotherapy has failed to demonstrate improvements in overall survival. Nevertheless, the emergence of novel treatment modalities such as targeted small molecules and immunotherapy has spawned neoadjuvant clinical trials that provide a unique vantage from which to study mechanism of action and biological potency. Tissue-based biomarkers are being developed to elucidate the biological efficacy of these treatments. With targeted therapy, these can include phospho-proteomic signatures of target pathway activation and deactivation. With immunotherapies, including sipuleucel-T and ipilimumab, recruitment of immune cells to the tumor microenvironment can also be used as robust markers of a biological effect. Such studies can provide insight not only into mechanism of action for these therapies but can also provide paths forward to improving clinical efficacy like with rationally designed combinations and dose selection. CONCLUSIONS: The use of neoadjuvant androgen-deprivation therapy and chemotherapy either singly or in combination before radical prostatectomy is generally safe and feasible while reducing prostate volume and tumor burden. However, pathologic complete response rates are low and no long-term survival benefit has been observed with the addition of neoadjuvant therapies over surgery alone at present, and therefore preoperative therapy is not the current standard of care in prostate cancer treatment.

Direct identification of PTEN phosphorylation sites.

The PTEN tumor suppressor gene encodes a phosphatidylinositol 3'-phosphatase that is inactivated in a high percentage of human tumors, particularly glioblastoma, melanoma, and prostate and endometrial carcinoma. Previous studies showed that PTEN is a seryl phosphoprotein and a substrate of protein kinase CK2 (CK2). However, the sites in PTEN that are phosphorylated in vivo have not been identified directly, nor has the effect of phosphorylation on PTEN catalytic activity been reported. We used mass spectrometric methods to identify Ser(370) and Ser(385) as in vivo phosphorylation sites of PTEN. These sites also are phosphorylated by CK2 in vitro, and phosphorylation inhibits PTEN activity towards its substrate, PIP3. We also identify a novel in vivo phosphorylation site, Thr(366). Following transient over-expression, a fraction of CK2 and PTEN co-immunoprecipitate. Moreover, pharmacological inhibition of CK2 activity leads to decreased Akt activation in PTEN+/+ but not PTEN-/- fibroblasts. Our results contrast with previous assignments of PTEN phosphorylation sites based solely on mutagenesis approaches, suggest that CK2 is a physiologically relevant PTEN kinase, and raise the possibility that CK2-mediated inhibition of PTEN plays a role in oncogenesis.

Oncogenic and wild-type Ras play divergent roles in the regulation of mitogen-activated protein kinase signaling.

UNLABELLED: H-Ras, K-Ras, and N-Ras regulate cellular growth and survival and are often activated by somatic mutation in human tumors. Although oncogenic lesions occur in a single Ras isoform within individual tumors, it is unclear whether the remaining wild-type isoforms play supporting roles in tumor growth. Here, we show that oncogenic and wild-type Ras isoforms play independent and nonredundant roles within the cell. Oncogenic Ras regulates basal effector pathway signaling, whereas wild-type Ras mediates signaling downstream of activated receptor tyrosine kinases (RTK). We show that both are necessary for exponential growth of Ras-mutant cell lines. Furthermore, we show that oncogenic Ras desensitizes signaling from EGF receptor (EGFR). Depletion of oncogenic Ras with siRNA oligonucleotides relieves this negative feedback, leading to the hyperactivation of EGFR and wild-type Ras signaling. Consistent with this model, combining oncogenic Ras depletion with EGFR inhibition potently increases cell death. SIGNIFICANCE: The results of this study highlight a novel role for wild-type Ras signaling in cancer cells harboring oncogenic RAS mutations. Furthermore, these findings reveal that therapeutically targeting oncogenic Ras signaling alone may be ineffective owing to feedback activation of RTKs, and suggest that blocking upstream RTKs in combination with downstream effector pathways may be beneficial in the treatment of Ras-mutant tumors.

FOG: Fragment Optimized Growth algorithm for the de novo generation of molecules occupying druglike chemical space.

An essential feature of all practical de novo molecule generating programs is the ability to focus the potential combinatorial explosion of grown molecules on a desired chemical space. It is a daunting task to balance the generation of new molecules with limitations on growth that produce desired features such as stability in water, synthetic accessibility, or drug-likeness. We have developed an algorithm, Fragment Optimized Growth (FOG), which statistically biases the growth of molecules with desired features. At the heart of the algorithm is a Markov Chain which adds fragments to the nascent molecule in a biased manner, depending on the frequency of specific fragment-fragment connections in the database of chemicals it was trained on. We show that in addition to generating synthetically feasible molecules, it can be trained to grow new molecules that resemble desired classes of molecules such as drugs, natural products, and diversity-oriented synthetic products. In order to classify our grown molecules, we developed the Topology Classifier (TopClass) algorithm that is capable of classifying compounds, for example as drugs or nondrugs. The classification accuracies obtained with TopClass compare favorably with the literature. Furthermore, in contrast to "black-box" approaches such as Neural Networks, TopClass brings to light characteristics of drugs that distinguish them from nondrugs.

Gene targeting of CK2 catalytic subunits.

Protein kinase CK2 is a highly conserved and ubiquitous serine-threonine kinase. It is a tetrameric enzyme that is made up of two regulatory CK2beta subunits and two catalytic subunits, either CK2alpha/CK2alpha, CK2alpha/CK2alpha', or CK2alpha'/CK2alpha'. Although the two catalytic subunits diverge in their C termini, their enzymatic activities are similar. To identify the specific function of the two catalytic subunits in development, we have deleted them individually from the mouse genome by homologous recombination. We have previously reported that CK2alpha' is essential for male germ cell development, and we now demonstrate that CK2alpha has an essential role in embryogenesis, as mice lacking CK2alpha die in mid-embryogenesis, with cardiac and neural tube defects.

The alpha catalytic subunit of protein kinase CK2 is required for mouse embryonic development.

Protein kinase CK2 (formerly casein kinase II) is a highly conserved and ubiquitous serine/threonine kinase that is composed of two catalytic subunits (CK2alpha and/or CK2alpha') and two CK2beta regulatory subunits. CK2 has many substrates in cells, and key roles in yeast cell physiology have been uncovered by introducing subunit mutations. Gene-targeting experiments have demonstrated that in mice, the CK2beta gene is required for early embryonic development, while the CK2alpha' subunit appears to be essential only for normal spermatogenesis. We have used homologous recombination to disrupt the CK2alpha gene in the mouse germ line. Embryos lacking CK2alpha have a marked reduction in CK2 activity in spite of the presence of the CK2alpha' subunit. CK2alpha(-/-) embryos die in mid-gestation, with abnormalities including open neural tubes and reductions in the branchial arches. Defects in the formation of the heart lead to hydrops fetalis and are likely the cause of embryonic lethality. Thus, CK2alpha appears to play an essential and uncompensated role in mammalian development.

CK2 as a positive regulator of Wnt signalling and tumourigenesis.

CK2 is upregulated in rapidly dividing cells including most human tumours. Transgenic overexpression of CK2 in lymphoid or mammary lineages predisposes to transformation. Multiple signalling and oncogene pathways could be regulated by CK2 in this process. Our studies suggest that phosphorylation of critical oncogenes by CK2, as well as by other serine-threonine kinases, regulates their stability via susceptibility to the proteasomal degradation system. Beta-catenin is a transcriptional co-factor in the Wnt signalling pathway that is regulated in this fashion. Inactivating mutations in the adenomatosis polyposis coli (APC) gene, which encodes a carrier protein for beta-catenin, or stabilizing mutations in beta-catenin itself, frequently occur in human tumours. CK2 and the monomeric serine-threonine kinase GSK3 have opposing actions on beta-catenin: GSK-3 phosphorylation of the N-terminus of beta-catenin promotes degradation; while phosphorylation by CK2 in the armadillo repeat protein interaction domain protects it. Beta-catenin is overexpressed in mammary tumours occurring in mice transgenic for CK2 or a dominant negative form of GSK3, and also in mammary tumours arising following treatment with the environmental carcinogen DMBA. Experiments are underway to determine whether expression of both CK2 and kinase inactive GSK3 further accelerates tumorigenesis. Inhibitors of GSK3 under development for treatment of diabetes could promote tumours, while CK2 inhibitors should be useful agents for treatment of cancer.