Alexander M. Stessin

Soluble adenylyl cyclase mediates nerve growth factor-induced activation of Rap1.

Nerve growth factor (NGF) and the ubiquitous second messenger cyclic AMP (cAMP) are both implicated in neuronal differentiation. Multiple studies indicate that NGF signals to at least a subset of its targets via cAMP, but the link between NGF and cAMP has remained elusive. Here, we have described the use of small molecule inhibitors to differentiate between the two known sources of cAMP in mammalian cells, bicarbonate- and calcium-responsive soluble adenylyl cyclase (sAC) and G protein-regulated transmembrane adenylyl cyclases. These inhibitors, along with sAC-specific small interfering RNA, reveal that sAC is uniquely responsible for the NGF-elicited rise in cAMP and is essential for the NGF-induced activation of the small G protein Rap1 in PC12 cells. In contrast and as expected, transmembrane adenylyl cyclase-generated cAMP is responsible for Rap1 activation by the G protein-coupled receptor ligand PACAP (pituitary adenylyl cyclase-activating peptide). These results identify sAC as a mediator of NGF signaling and reveal the existence of distinct pathways leading to cAMP-dependent signal transduction.

Calcium-sensing soluble adenylyl cyclase mediates TNF signal transduction in human neutrophils

Through chemical screening, we identified a pyrazolone that reversibly blocked the activation of phagocyte oxidase (phox) in human neutrophils in response to tumor necrosis factor (TNF) or formylated peptide. The pyrazolone spared activation of phox by phorbol ester or bacteria, bacterial killing, TNF-induced granule exocytosis and phox assembly, and endothelial transmigration. We traced the pyrazolones mechanism of action to inhibition of TNF-induced intracellular Ca2+ elevations, and identified a nontransmembrane (“soluble”) adenylyl cyclase (sAC) in neutrophils as a Ca2+-sensing source of cAMP. A sAC inhibitor mimicked the pyrazolones effect on phox. Both compounds blocked TNF-induced activation of Rap1A, a phox-associated guanosine triphosphatase that is regulated by cAMP. Thus, TNF turns on phox through a Ca2+-triggered, sAC-dependent process that may involve activation of Rap1A. This pathway may offer opportunities to suppress oxidative damage during inflammation without blocking antimicrobial function.

Neoadjuvant radiation is associated with improved survival in patients with resectable pancreatic cancer: an analysis of data from the surveillance, epidemiology, and end results (SEER) registry.

PURPOSE Cancer of the exocrine pancreas is the fifth leading cause of cancer death in the United States. Neoadjuvant chemoradiation has been investigated in several trials as a strategy for downstaging locally advanced disease to resectability. The aim of the present study is to examine the effect of neoadjuvant radiation therapy (RT) vs. other treatments on long-term survival for patients with resectable pancreatic cancer in a large population-based sample group. METHODS AND MATERIALS The Surveillance, Epidemiology, and End Results (SEER) registry database (1994-2003) was queried for cases of surgically resected pancreatic cancer. Retrospective analysis was performed. The endpoint of the study was overall survival. RESULTS Using Kaplan-Meier analysis we found that the median overall survival of patients receiving neoadjuvant RT was 23 months vs. 12 months with no RT and 17 months with adjuvant RT. Using Cox regression and controlling for independent covariates (age, sex, stage, grade, and year of diagnosis), we found that neoadjuvant RT results in significantly higher rates of survival than other treatments (hazard ratio [HR], 0.55; 95% confidence interval, 0.38-0.79; p = 0.001). Specifically comparing adjuvant with neoadjuvant RT, we found a significantly lower HR for death in patients receiving neoadjuvant RT rather than adjuvant RT (HR, 0.63; 95% confidence interval, 0.45-0.90; p = 0.03). CONCLUSIONS This analysis of SEER data showed a survival benefit for the use of neoadjuvant RT over surgery alone or surgery with adjuvant RT in treating pancreatic cancer. Therapeutic strategies that use neoadjuvant RT should be further explored for patients with resectable pancreatic cancer.

Does adjuvant external-beam radiotherapy improve outcomes for nonbenign meningiomas? A Surveillance, Epidemiology, and End Results (SEER)–based analysis

OBJECT The aim of this study was to examine the effect of postoperative external-beam radiation therapy (EBRT) on disease-specific survival in patients with nonbenign meningiomas. METHODS The Surveillance, Epidemiology, and End Results (SEER) database from 1988 to 2007 was queried for cases of resected Grades II (atypical) and III (malignant) meningioma. Disease-specific survival outcomes were determined using Kaplan-Meier survival analysis and Cox proportional hazards models. Logistic regression analysis was used to determine the likelihood of receiving EBRT for Grade II versus Grade III. Because atypical and malignant meningiomas underwent WHO reclassification in 2000, the authors carried out an additional analysis of outcomes of these tumors from 2000 to 2008. RESULTS There were 657 patients included in the analysis; of these, 244 received adjuvant radiation. Compared with patients with Grade II meningioma, patients with Grade III disease were 41.9% more likely to receive EBRT after gross-total resection and 36.7% more likely to receive it after subtotal resection (95% CI 0.58-3.26). Controlling for grade, extent of resection, size and anatomical location of the tumor, year of diagnosis, race, age, and sex, adjuvant EBRT did not impart a survival benefit (HR 1.492; 95% CI 0.827-2.692). There was also no survival advantage to EBRT in an analysis of cases diagnosed after the WHO 2000 reclassification of meningiomas (HR 0.828; 95% CI 0.350-1.961). CONCLUSIONS The results of this population-based retrospective analysis demonstrate that the role of radiation remains unclear. They underscore the need for randomized prospective clinical trials to assess the usefulness of adjuvant EBRT in Grades II and III meningioma so as to define more precisely the subset of patients who may benefit from the addition of adjuvant radiation.

The Role of Postoperative Radiation Therapy in the Treatment of Meningeal Hemangiopericytoma—Experience From the SEER Database

PURPOSE The aim of this study was to examine the effect of postoperative radiation therapy (RT) on cause-specific survival in patients with meningeal hemangiopericytomas. METHODS AND MATERIALS The Surveillance, Epidemiology, and End Results database from 1990-2008 was queried for cases of surgically resected central nervous system hemangiopericytoma. Patient demographics, tumor location, and extent of resection were included in the analysis as covariates. The Kaplan-Meier product-limit method was used to analyze cause-specific survival. A Cox proportional hazards regression analysis was conducted to determine which factors were associated with cause-specific survival. RESULTS The mean follow-up time is 7.9 years (95 months). There were 76 patients included in the analysis, of these, 38 (50%) underwent gross total resection (GTR), whereas the other half underwent subtotal resection (STR). Postoperative RT was administered to 42% (16/38) of the patients in the GTR group and 50% (19/38) in the STR group. The 1-year, 10-year, and 20-year cause-specific survival rates were 99%, 75%, and 43%, respectively. On multivariate analysis, postoperative RT was associated with significantly better survival (HR = 0.269, 95% CI 0.084-0.862; P=.027), in particular for patients who underwent STR (HR = 0.088, 95% CI: 0.015-0.528; P<.008). CONCLUSIONS In the absence of large prospective trials, the current clinical decision-making of hemangiopericytoma is mostly based on retrospective data. We recommend that postoperative RT be considered after subtotal resection for patients who could tolerate it. Based on the current literature, the practical approach is to deliver limited field RT to doses of 50-60 Gy while respecting the normal tissue tolerance. Further investigations are clearly needed to determine the optimal therapeutic strategy.

FTY720, sphingosine 1-phosphate receptor modulator, selectively radioprotects hippocampal neural stem cells.

Cranial irradiation is an effective treatment modality for both primary and metastatic brain tumors, yet it induces cognitive decline in a substantial number of patients. At present, there are no established methods for neuroprotection. Recent investigations have revealed a link between radiation-induced cognitive dysfunction and the loss of neural precursor cells in the hippocampus. Hence, identifying pharmacological agents, capable of protecting this cell population, is of interest. FTY720 (fingolimod), an FDA-approved oral drug for the treatment of multiple sclerosis, has been shown to promote the survival and differentiation of neural progenitors, as well as remyelination and repair after brain injury. In this study, we show that FTY720, used at nanomolar concentrations, is capable of increasing the viability and neurogenicity of irradiated neural stem cells from the hippocampus. In contrast, it does not provide radioprotection in a human breast cancer cell line and two glioma cell lines. These results suggest a potential therapeutic role for FTY720 as a neuroprotector during cranial irradiation. Further preclinical studies are warranted to evaluate this possibility.

Demographic Disparities in Patterns of Care and Survival Outcomes for Patients with Resected Gastric Adenocarcinoma

Background: Several reports showed incomplete adoption of adjuvant radiotherapy (RT) for resectable gastric cancer since the publication of Intergroup 0116 trial results. The aims of this study were to identify demographic factors associated with omission of adjuvant RT and assess the impact of this omission on survival. Methods: SEER database was queried for cases of resected gastric cancer. Multivariate analyses with logistic and Cox regressions were used to examine (a) likelihood of receiving adjuvant RT for different patient and county demographics and (b) effect of demographics on survival outcomes. Results: A total of 7,348 patients met the study criteria. Adjuvant RT was used in 33.1% of cases diagnosed in 1998–2001 and in 45.3% of cases in 2002–2007 (P < 0.001). Controlling for independent covariates, African Americans were 8.9% less likely to receive adjuvant RT than Caucasians or Asians (P < 0.001). Correspondingly, overall survival rates were significantly lower for African Americans than other races (HR = 1.38, P < 0.001). Furthermore, both the likelihood of receiving RT and the survival rates were significantly affected by county demographics: percent of population without high school education, percent of households below the poverty line, and median household income. Survival rates were highest among Asians, but this finding did not reflect more frequent use of RT. Conclusions: Race and socioeconomic factors are significant predictors of treatment and survival outcomes for patients with resectable gastric cancer. Impact: The findings of this and similar studies may aide the medical community in designing more effective strategies to ameliorate the standards of care nationwide. Cancer Epidemiol Biomarkers Prev; 20(2); 223–33. ©2011 AACR.

Soluble adenylyl cyclase-generated cyclic adenosine monophosphate promotes fast migration in PC12 cells.

In a model for neuronal movement, PC12 cells undergo fast migration in response to nerve growth factor (NGF) and phorbol ester (PMA). We previously showed that NGF increases intracellular cAMP via activation of soluble adenylyl cyclase (sAC). In this report, we demonstrate that sAC activation is an essential component of NGF‐ + PMA‐induced fast migration in PC12 cells. Interestingly, PMA also raises intracellular cAMP but does so by stimulating transmembrane adenylyl cyclases (tmAC); however, this tmAC‐generated cAMP does not contribute to fast migration. Therefore, cells must possess independent pools of cAMP capable of modulating distinct functions.

Soluble Adenylyl Cyclase Is Necessary and Sufficient to Overcome the Block of Axonal Growth by Myelin-Associated Factors

Neurons in the CNS do not regenerate following injury; regeneration is blocked by inhibitory proteins in myelin, such as myelin-associated glycoprotein (MAG). Elevating neuronal levels of the second messenger cAMP overcomes this blocked axonal outgrowth. One way to elevate cAMP is pretreating neurons with neurotrophins, such as brain-derived neurotrophic factor (BDNF). However, pleiotropic effects and poor bioavailability make exogenous administration of neurotrophins in vivo problematic; therefore, alternative targets must be considered. In neurons, two families of adenylyl cyclases synthesize cAMP, transmembrane adenylyl cyclases (tmACs), and soluble adenylyl cyclase (sAC). Here, we demonstrate that sAC is the essential source of cAMP for BDNF to overcome MAG-dependent inhibition of neurite outgrowth. Elevating sAC in rat and mouse neurons is sufficient to induce neurite outgrowth on myelin in vitro and promotes regeneration in vivo. These results suggest that stimulators of sAC might represent a novel therapeutic strategy to promote axonal growth and regeneration.

Does adjuvant radiotherapy benefit patients with diffuse‐type gastric cancer? Results from the Surveillance, Epidemiology, and End Results database

Diffuse‐type gastric cancer is observed in approximately one‐third of gastric cancers, yet the optimal treatment remains controversial. In the recently published Intergroup 0116 trial, a subgroup analysis demonstrated a lack of a long‐term survival benefit for adjuvant chemoradiation therapy among patients with diffuse‐type gastric cancer.