Darren R. Tyson

O-Sulfonation of Serine and Threonine Mass Spectrometric Detection and Characterization of a New Posttranslational Modification in Diverse Proteins Throughout the Eukaryotes

Protein sulfonation on serine and threonine residues is described for the first time. This post-translational modification is shown to occur in proteins isolated from organisms representing a broad span of eukaryote evolution, including the invertebrate mollusk Lymnaea stagnalis, the unicellular malaria parasite Plasmodium falciparum, and humans. Detection and structural characterization of this novel post-translational modification was carried out using liquid chromatography coupled to electrospray tandem mass spectrometry on proteins including a neuronal intermediate filament and a myosin light chain from the snail, a cathepsin-C-like enzyme from the parasite, and the cytoplasmic domain of the human orphan receptor tyrosine kinase Ror-2. These findings suggest that sulfonation of serine and threonine may be involved in multiple functions including protein assembly and signal transduction.

Periprostatic Adipose Tissue as a Modulator of Prostate Cancer Aggressiveness

PURPOSE Adipose tissue has been suggested to contribute to the pathogenesis of various disease states, including prostate cancer. We investigated the association of cytokines and growth factors secreted by periprostatic adipose tissue with pathological features of aggressive prostate cancer. MATERIALS AND METHODS Periprostatic adipose tissue was harvested from patients undergoing radical prostatectomy and cultured for 24 hours to generate conditioned medium or snap frozen immediately for functional signaling profiling. Multiplex analysis of the periprostatic adipose tissue conditioned medium was used to detect cytokine levels and compared to patient matched serum from 7 patients. Interleukin-6 in serum and periprostatic adipose tissue conditioned medium was further analyzed by enzyme-linked immunosorbent assay and correlated with clinical variables, such as age, body mass index and Gleason score, in 45 patients. Interleukin-6 expression in periprostatic adipose tissue was determined by immunohistochemistry. Reverse phase protein microarray technology was used to analyze cell signaling networks in periprostatic adipose tissue. RESULTS Interleukin-6 in periprostatic adipose tissue conditioned medium was approximately 375 times greater than that in patient matched serum and levels correlated with pathological grade. This finding was further extended by cell signaling analysis of periprostatic adipose tissue, which showed greater phosphorylation on Stat3 with high grade tumors (any component of Gleason score 4 or 5). CONCLUSIONS Higher Gleason score correlated with high levels of conditioned medium derived interleukin-6. Moreover, cell signaling analysis of periprostatic adipose tissue identified activated signaling molecules, including STAT3, that correlated with Gleason score. Since STAT3 is interleukin-6 regulated, these findings suggest that periprostatic adipose tissue may have a role in modulating prostate cancer aggressiveness by serving as a source of interleukin-6. Also, we found low numbers of inflammatory cells in the fat, suggesting that adipocytes are the major secretors of interleukin-6.

Bone marrow stem cells for urologic tissue engineering

ObjectivesExperiments in rats and dogs have demonstrated the potential of bone marrow-derived mesenchymal stem cells (MSCs) for urinary tract tissue engineering. However, the small graft size in rats and a failure to identify the MSCs in engineered tissues made it difficult to assess the true potential of these cells. Our goals were to characterize MSCs from pigs, determine their ability to differentiate into smooth muscle cells (SMCs) and use them in an autologous augmentation cystoplasty.MethodsMSCs were isolated from pigs and analyzed for common markers of MSCs by flow cytometry. SMC differentiation was determined by immunoblotting. MSCs were isolated, genetically labeled, expanded in vitro, seeded onto small intestinal submucosa (SIS) and used for autologous bladder augmentation.ResultsPorcine MSCs are morphologically and immunophenotypically similar to human MSCs. Culturing MSCs at low density enhances proliferation rates. MSCs consistently differentiate into mature SMCs in vitro when maintained at confluence. Labeled MSCs grew on SIS over one week in vitro and survived a 2-week implantation as an autologous bladder augment in vivo. Some label-positive cells with SMC morphology were detected, but most SMCs were negative. Notably, many cells with a urothelial morphology stained positively.ConclusionsPorcine MSCs have similar properties to MSCs from other species and consistently undergo differentiation into mature SMC in vitro under specific culture conditions. Labeled MSCs within SIS may assist tissue regeneration in augmentation cystoplasty but may not significantly incorporate into smooth muscle bundles.

Network analysis of the focal adhesion to invadopodia transition identifies a PI3K-PKCα invasive signaling axis.

The activity of the lipid kinase PI3K governs whether the protein kinase PKCα promotes invasive behavior of cancer cells. Becoming Invasive Invasive and metastatic cancer cells form cellular protrusions called invadopodia that can degrade the extracellular matrix. Hoshino et al. integrated data from head and neck carcinomas with network analysis of invadopodia and focal adhesions, cellular structures that contain many of the same components as invadopodia but have decreased ability to degrade the extracellular matrix. They identified phosphatidylinositol 3-kinase (PI3K) and protein kinase C α (PKCα) as key determinants in the formation of invadopodia. The formation of invadopodia was enhanced by PKCα in cells with wild-type PI3K but was inhibited by PKCα in cells with enhanced PI3K activity (due to expression of components of the PI3K pathway with cancer-associated mutations). These results suggested that PKCα participated in a negative feedback loop that limited the activity of PI3K and thus cellular invasiveness, which the authors confirmed. The combination of high PI3K activity with low PKCα activity correlated with increased number of invadopodia in cell lines derived from head and neck carcinoma, breast cancer, or melanoma. This PI3K-high and PKCα-low signaling state may be useful as a biomarker for cancer aggressiveness. In cancer, deregulated signaling can produce an invasive cellular phenotype. We modeled the invasive transition as a theoretical switch between two cytoskeletal structures: focal adhesions and extracellular matrix–degrading invadopodia. We constructed molecular interaction networks of each structure and identified upstream regulatory hubs through computational analyses. We compared these regulatory hubs to the status of signaling components from head and neck carcinomas, which led us to analyze phosphatidylinositol 3-kinase (PI3K) and protein kinase C α (PKCα). Consistent with previous studies, PI3K activity promoted both the formation and the activity of invadopodia. We found that PI3K induction of invadopodia was increased by overexpression of SH2 (Src homology 2) domain–containing inositol 5′-phosphatase 2 (SHIP2), which converts the phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] that is produced by PI3K activity to phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2], which is believed to promote invadopodia formation. Knockdown of PKCα had divergent effects on invadopodia formation, depending on the status of PI3K. Loss of PKCα inhibited invadopodia formation in cells with wild-type PI3K pathway status. Conversely, in cells with constitutively active PI3K (through activating PI3K mutants or lacking the endogenous opposing enzyme PTEN), PKCα knockdown increased invadopodia formation. Mechanistic studies revealed a negative feedback loop from PKCα that dampened PI3K activity and invasive behavior in cells with genetic hyperactivation of the PI3K pathway. These studies demonstrated the potential of network modeling as a discovery tool and identified PI3K and PKCα as interacting regulators of invasive behavior.

Annexin A2 positively contributes to the malignant phenotype and secretion of IL-6 in DU145 prostate cancer cells.

Several groups, including ours, have reported that annexin A2 (ANXA2) expression is reduced in most prostate cancer (CaP). More recently, however, we reported that ANXA2 is expressed in some high‐grade tumors, but the biologic consequence of this is currently unknown. To elucidate the function of ANXA2 in CaP, we reduced its expression in DU145 cells using shRNA and tested the impact on characteristics of malignancy. Reduction of ANXA2 suppressed anchorage‐dependent and ‐independent cell growth without affecting invasiveness. Interestingly, interleukin‐6 (IL‐6) secretion was reduced concomitantly with the reduction of ANXA2 but independently of S100A10. IL‐6 expression was restored when wild type but not mutant ANXA2 was reexpressed in these cells. In a retrospective study of radical prostatectomy specimens from patients with nonmetastatic CaP, 100% of patients with ANXA2‐positive tumors (n = 4) had a biochemical relapse while only 50% of patients with ANXA2 negative tumors (n = 20) relapsed, suggesting that ANXA2 expression in prostate tumors may be predictive of biochemical relapse. Significant cytoplasmic staining of ANXA2 was detected in 3 of 4 ANXA2‐positive tumors, whereas ANXA2 is localized to the plasma membrane in benign prostatic glands. These finding, taken together, suggests a possible mechanism whereby ANXA2 expression positively contributes to an aggressive phenotype in a subset of CaP and suggest that ANXA2 has markedly different functions depending on its cellular context. Finally, this is the first description of a role for ANXA2 in IL‐6 expression, and ANXA2 represents a new therapeutic target for reducing IL‐6 in high‐grade prostate cancer.

Long-Term Impact of a Robot Assisted Laparoscopic Prostatectomy Mini Fellowship Training Program on Postgraduate Urological Practice Patterns

PURPOSE Robot assisted laparoscopic prostatectomy has stimulated a great deal of interest among urologists. We evaluated whether a mini fellowship for robot assisted laparoscopic prostatectomy would enable postgraduate urologists to incorporate this new procedure into clinical practice. MATERIALS AND METHODS From July 2003 to July 2006, 47 urologists participated in the robot assisted laparoscopic prostatectomy mini fellowship program. The 5-day course had a 1:2 faculty-to-attendee ratio. The curriculum included lectures, tutorials, surgical case observation, and inanimate, animate and cadaveric robotic skill training. Questionnaires assessing practice patterns 1, 2 and 3 years after the mini fellowship program were analyzed. RESULTS One, 2 and 3 years after the program the response rate to the questionnaires was 89% (42 of 47 participants), 91% (32 of 35) and 88% (21 of 24), respectively. The percent of participants performing robot assisted laparoscopic prostatectomy in years 1 to 3 after the mini fellowship was 78% (33 of 42), 78% (25 of 32) and 86% (18 of 21), respectively. Among the surgeons performing the procedure there was a progressive increase in the number of cases each year with increasing time since the mini fellowship training. In the 3 attendees not performing the procedure 3 years after the mini fellowship training the reasons were lack of a robot, other partners performing it and a feeling of insufficient training to incorporate the procedure into clinical practice in 1 each. One, 2 and 3 years following the mini fellowship training program 83%, 84% and 90% of partnered attendees were performing robot assisted laparoscopic prostatectomy, while only 67%, 56% and 78% of solo attendees, respectively, were performing it at the same followup years. CONCLUSIONS An intensive, dedicated 5-day educational course focused on learning robot assisted laparoscopic prostatectomy enabled most participants to successfully incorporate and maintain this procedure in clinical practice in the short term and long term.

Reverse Phase Protein Array profiling of oropharyngeal cancer and significance of PIK3CA mutations in HPV-associated head and neck cancer

PURPOSE Human papilloma virus (HPV)-associated (HPV+) oropharyngeal squamous cell carcinomas (OPSCC) have different molecular and biologic characteristics and clinical behavior compared with HPV-negative (HPV-) OPSCC. PIK3CA mutations are more common in HPV(+) OPSCC. To define molecular differences and tumor subsets, protein expression and phosphorylation were compared between HPV(+) and HPV(-) OPSCC and between tumors with and without PIK3CA mutations. EXPERIMENTAL DESIGN Expression of 137 total and phosphorylated proteins was evaluated by reverse-phase protein array in 29 HPV(+) and 13 HPV(-) prospectively collected OPSCCs. Forty-seven OPSCCs were tested for hotspot-activating mutations in PIK3CA and AKT. Activation of PIK3CA downstream targets and sensitivity to pathway inhibitors were determined in HPV(+) head and neck cancer cells overexpressing wild-type or mutant PIK3CA. RESULTS Analyses revealed 41 differentially expressed proteins between HPV(+) and HPV(-) OPSCC categorized into functional groups: DNA repair, cell cycle, apoptosis, phosphoinositide 3-kinase (PI3K)/AKT/mTOR, and receptor kinase pathways. All queried DNA repair proteins were significantly upregulated in HPV(+) samples. A total of 8 of 33 HPV(+) and 0 of 14 HPV(-) tumors contained activating PIK3CA mutations. Despite all activating PIK3CA mutations occurring in HPV(+) samples, HPV(+) tumors had lower mean levels of activated AKT and downstream AKT target phosphorylation. Ectopic expression of mutant PIK3CA in HPV(+) cells increased mTOR, but not AKT activity. HPV E6/E7 overexpression inhibited AKT phosphorylation in HPV-negative cells. Mutant PIK3CA overexpressing cells were more sensitive to a dual PI3K/mTOR inhibitor compared with an AKT inhibitor. CONCLUSIONS Protein expression analyses suggest that HPV(+) and HPV(-) OPSCC differentially activate DNA repair, cell cycle, apoptosis, PI3K/AKT/mTOR, and receptor kinase pathways. PIK3CA mutations are more common in HPV(+) OPSCC and are associated with activation of mTOR, but not AKT. These data suggest that inhibitors for mTOR may have activity against HPV(+) PIK3CA mutant oropharyngeal cancers.

Induction of Transcriptional Activity of the Cyclic Adenosine Monophosphate Response Element Binding Protein by Parathyroid Hormone and Epidermal Growth Factor in Osteoblastic Cells

Previously, we have shown that parathyroid hormone (PTH) transactivation of cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) requires both serine 129 (S129) and serine 133 (S133) in rat osteosarcoma cells UMR 106‐01 (UMR) cells. Furthermore, although protein kinase A (PKA) is responsible for phosphorylation at S133, glycogen synthase kinase 3β (GSK‐3β) activity is required and may be responsible for phosphorylation of CREB at S129. Here, we show, using the GAL4‐CREB reporter system, that epidermal growth factor (EGF) can transactivate CREB in UMR cells in addition to PTH. Additionally, treatment of UMR cells with both PTH and EGF results in greater than additive transactivation of CREB. Furthermore, using mutational analysis we show that S129 and S133 are required for EGF‐induced transcriptional activity. EGF activates members of the MAPK family including p38 and extracellular signal—activated kinases (ERKs), and treatment of UMR cells with either the p38 inhibitor (SB203580) or the MEK inhibitor (PD98059) prevents phosphorylation of CREB at S133 by EGF but not by PTH. Treatment of cells with either SB203580 or PD98059 alone or together significantly inhibits transactivation of CREB by EGF but not by PTH, indicating that EGF regulates CREB phosphorylation and transactivation through p38 and ERKs and PTH does not. Finally, the greater than additive transactivation of CREB by PTH and EGF is significantly inhibited by the PKA inhibitor H‐89 or by cotreatment with SB203580 and PD98059. Thus, several different signaling pathways in osteoblastic cells can converge on and regulate CREB activity. This suggests, in vivo, that circulating agents such as PTH and EGF are acting in concert to exert their effects.

The contribution of age structure to cell population responses to targeted therapeutics

Cells grown in culture act as a model system for analyzing the effects of anticancer compounds, which may affect cell behavior in a cell cycle position-dependent manner. Cell synchronization techniques have been generally employed to minimize the variation in cell cycle position. However, synchronization techniques are cumbersome and imprecise and the agents used to synchronize the cells potentially have other unknown effects on the cells. An alternative approach is to determine the age structure in the population and account for the cell cycle positional effects post hoc. Here we provide a formalism to use quantifiable lifespans from live cell microscopy experiments to parameterize an age-structured model of cell population response.

Loss of annexin A1 disrupts normal prostate glandular structure by inducing autocrine IL-6 signaling

Annexin A1 (ANXA1) expression is commonly reduced in premalignant lesions and prostate cancer, but a causal relationship of ANAX1 loss with carcinogenesis has not been established. ANXA1 levels have been shown to inversely correlate with interleukin 6 (IL-6) expression in other cell types and IL-6 has been suggested to enhance prostate cancer initiation and promotion. To investigate whether loss of ANXA1 may contribute to prostate carcinogenesis, ANXA1 expression was reduced using RNA interference in non-tumorigenic human prostatic epithelial cells (RWPE-1/rA1). No effect on morphology, apoptosis, migration or anchorage-dependent or -independent growth was detected. However, IL-6 mRNA and secreted protein levels were elevated in RWPE-1/rA1 cells. In addition, re-expression of ANXA1 in these cells suppressed IL-6 secretion, and altering ANXA1 levels in prostate cancer cells had similar effects on IL-6. The effects of ANXA1 loss and increased IL-6 expression on prostate epithelium were examined using an assay of acinar morphogenesis in vitro. Acini formed by RWPE-1/rA1 cells had delayed luminal clearing and larger mean diameters than control cells. The RWPE-1/rA1 phenotype was recapitulated by treating control cells with recombinant IL-6 and was reversed in RWPE-1/rA1 cells by blocking IL-6 bioactivity. Taken together, these data support a direct role for decreased ANXA1 expression in prostate carcinogenesis and enhancing tumor aggressiveness via the upregulation of IL-6 expression and activity.