SLC4A2-mediated Cl-/HCO3- exchange activity is essential for calpain-dependent regulation of the actin cytoskeleton in osteoclasts.

Bone remodeling requires osteoclasts to generate and maintain an acidified resorption compartment between the apical membrane and the bone surface to solubilize hydroxyapatite crystals within the bone matrix. This acidification process requires (i) apical proton secretion by a vacuolar H(+)-ATPase, (ii) actin cytoskeleton reorganization into a podosome belt that forms a gasket to restrict lacunar acid leakage, and (iii) basolateral chloride uptake and bicarbonate extrusion by an anion exchanger to provide Cl(-) permissive for apical acid secretion while preventing cytoplasmic alkalinization. Here we show that osteoclast-targeted deletion in mice of solute carrier family 4 anion exchanger member 2 (Slc4a2) results in osteopetrosis. We further demonstrate a previously unrecognized consequence of SLC4A2 loss of function in the osteoclast: dysregulation of calpain-dependent podosome disassembly, leading to abnormal actin belt formation, cell spreading, and migration. Rescue of SLC4A2-deficient osteoclasts with functionally defined mutants of SLC4A2 indicates regulation of actin cytoskeletal reorganization by anion-exchange activity and intracellular pH, independent of SLC4A2's long N-terminal cytoplasmic domain. These data suggest that maintenance of intracellular pH in osteoclasts through anion exchange regulates the actin superstructures required for bone resorption.

Variation in hospital mortality rates with inpatient cancer surgery.

OBJECTIVE: To elucidate clinical mechanisms underlying variation in hospital mortality after cancer surgery BACKGROUND: : Thousands of Americans die every year undergoing elective cancer surgery. Wide variation in hospital mortality rates suggest opportunities for improvement, but these efforts are limited by uncertainty about why some hospitals have poorer outcomes than others. METHODS: Using data from the 2006-2007 National Cancer Data Base, we ranked 1279 hospitals according to a composite measure of perioperative mortality after operations for bladder, esophagus, colon, lung, pancreas, and stomach cancers. We then conducted detailed medical record review of 5632 patients at 1 of 19 hospitals with low mortality rates (2.1%) or 30 hospitals with high mortality rates (9.1%). Hierarchical logistic regression analyses were used to compare risk-adjusted complication incidence and case-fatality rates among patients experiencing serious complications. RESULTS: The 7.0% absolute mortality difference between the 2 hospital groups could be attributed to higher mortality from surgical site, pulmonary, thromboembolic, and other complications. The overall incidence of complications was not different between hospital groups [21.2% vs 17.8%; adjusted odds ratio (OR) = 1.34, 95% confidence interval (CI): 0.93-1.94]. In contrast, case-fatality after complications was more than threefold higher at high mortality hospitals than at low mortality hospitals (25.9% vs 13.6%; adjusted OR = 3.23, 95% CI: 1.56-6.69). CONCLUSIONS: Low mortality and high mortality hospitals are distinguished less by their complication rates than by how frequently patients die after a complication. Strategies for ensuring the timely recognition and effective management of postoperative complications will be essential in reducing mortality after cancer surgery.

Loss of Slc4a1b chloride/bicarbonate exchanger function protects mechanosensory hair cells from aminoglycoside damage in the zebrafish mutant persephone.

Mechanosensory hair cell death is a leading cause of hearing and balance disorders in the human population. Hair cells are remarkably sensitive to environmental insults such as excessive noise and exposure to some otherwise therapeutic drugs. However, individual responses to damaging agents can vary, in part due to genetic differences. We previously carried out a forward genetic screen using the zebrafish lateral line system to identify mutations that alter the response of larval hair cells to the antibiotic neomycin, one of a class of aminoglycoside compounds that cause hair cell death in humans. The persephone mutation confers resistance to aminoglycosides. 5 dpf homozygous persephone mutants are indistinguishable from wild-type siblings, but differ in their retention of lateral line hair cells upon exposure to neomycin. The mutation in persephone maps to the chloride/bicarbonate exchanger slc4a1b and introduces a single Ser-to-Phe substitution in zSlc4a1b. This mutation prevents delivery of the exchanger to the cell surface and abolishes the ability of the protein to import chloride across the plasma membrane. Loss of function of zSlc4a1b reduces hair cell death caused by exposure to the aminoglycosides neomycin, kanamycin, and gentamicin, and the chemotherapeutic drug cisplatin. Pharmacological block of anion transport with the disulfonic stilbene derivatives DIDS and SITS, or exposure to exogenous bicarbonate, also protects hair cells against damage. Both persephone mutant and DIDS-treated wild-type larvae show reduced uptake of labeled aminoglycosides. persephone mutants also show reduced FM1-43 uptake, indicating a potential impact on mechanotransduction-coupled activity in the mutant. We propose that tight regulation of the ionic environment of sensory hair cells, mediated by zSlc4a1b activity, is critical for their sensitivity to aminoglycoside antibiotics.

Cancer recurrence: an important but missing variable in national cancer registries.

BACKGROUND: Cancer recurrence is a critically important outcome to patients and providers. However, no publicly available cancer registry data contain recurrence information. The National Cancer Data Base (NCDB) collects recurrence data; however, this information is not provided to researchers because of completeness and accuracy concerns. Our objective was to examine completeness of cancer recurrence information in the NCDB. METHODS: Stage I-III thyroid/colon/melanoma/pancreas/breast cancers diagnosed in 2002-2005 were identified. Recurrence status, recurrence type, and recurrence date were evaluated for data completeness. Patient, tumor, and hospital factors were examined using generalized linear mixed models. Pseudo-R (2) statistics estimated the relative contribution of patient and hospital factors. RESULTS: Of 702,144 patients with thyroid/colon/melanoma/pancreas/breast cancers treated in 1405 hospitals, recurrence information was incomplete in 21.5/24.0/20.2/34.8/18.2 % of patients, respectively. On average, hospitals had incomplete recurrence information on 56.7-66.7 % of their patients. Patients with incomplete information had more comorbidities, a higher cancer stage, non-private insurance, and lived farther from the hospital. Hospitals with the poorest collection were larger tertiary hospitals serving higher-income patients. However, these patients and hospital factors explained less than 3 %, while unexplained hospital variation accounted for the largest part of the observed variation (%ΔR (2) = 84 %). CONCLUSIONS: The majority of hospitals report incomplete recurrence information for more than half of their patients. The presence of incomplete recurrence information was largely dependent on undefined hospital factors, rather than patient or tumor characteristics. Attempts to improve cancer recurrence information should focus on hospital operational and process factors surrounding how the hospital tumor registries collect recurrence data.

Substitution of transmembrane domain Cys residues alters pH(o)-sensitive anion transport by AE2/SLC4A2 anion exchanger.

AE2/SLC4A2 is the most widely expressed of the Na(+)-independent SLC4 Cl(-)/HCO3 (-) exchangers and is essential for postnatal survival, but its structure remains unknown. We have generated and expressed a mouse AE2 construct devoid of transmembrane domain cysteine (Cys) residues, mAE2Cys-less, to enhance the utility of Cys-substitution mutagenesis for structural and structure-function studies of mAE2. mAE2Cys-less expressed in Xenopus oocytes exhibited partial reduction of stilbene disulfonate-sensitive anion exchange activity. This activity was independent of the mAE2 N-terminal cytosolic domain and was accompanied by near-normal surface expression, without change in K 1/2 for extracellular Cl(-). mAE2Cys-less exhibited wildtype activation of anion exchange by hypertonicity and by NH4Cl, and wildtype inhibition of anion exchange by acidic intracellular pH (pHi) in the absence of NH4 (+). However, inhibition of anion exchange by extracellular pH (pHo) exhibited an alkaline shifted pHo(50) value of at least 0.6-0.7 pH units. Although SO4 (2-) transport by mAE2Cys-less resembled wildtype mAE2 in its stimulation by acidic pHo, the absence of transmembrane domain Cys residues abrogated activation of oxalate transport by acidic pHo. The contrasting enhancement of SO4 (2-) transport by alkaline pHo in the mAE1 anion translocation pathway mutant E699Q (Am J Physiol Cell Physiol 295: C302) was phenocopied by the corresponding mutant E1007Q in both AE2 and AE2Cys-less. However, the absence of transmembrane domain Cys residues exacerbated the reduced basal anion transport function exhibited by this and other missense substitutions at AE2 residue E1007. AE2Cys-less will be a valuable experimental tool for structure-function studies of the SLC4 gene family, but its utility for studies of AE2 regulation by extracellular pH must be evaluated in the context of its alkaline-shifted pHo sensitivity, resembling that of AE2 gastric parietal cell variant AE2c1.

The role of clinicians in determining radioactive iodine use for low-risk thyroid cancer.

BACKGROUND: There is controversy regarding the optimal management of thyroid cancer. The proportion of patients with low-risk thyroid cancer who received radioactive iodine (RAI) treatment increased over the last 20 years, and little is known about the role played by clinicians in hospital-level RAI use for low-risk disease. METHODS: Thyroid surgeons affiliated with 368 hospitals that had Commission on Cancer-accredited cancer programs were surveyed. Survey data were linked to data reported to the National Cancer Database. A multivariable analysis was used to assess the relation between clinician decision makers and hospital-level RAI use after total thyroidectomy in patients with stage I, well differentiated thyroid cancer. RESULTS: The survey response rate was 70% (560 of 804 surgeons). The surgeon was identified as the primary decision maker by 16% of the surgeons; the endocrinologist was identified as the primary decision maker by 69%, and a nuclear medicine, radiologist, or other physician was identified as the primary decision maker by 15%. In a multivariable analysis controlling for hospital case volume and hospital type, when the primary decision maker was in a specialty other than endocrinology or surgery, there was greater use of RAI at the hospital (P < .001). A greater number of providers at the hospital where RAI was administered and having access to a tumor board also were associated with increased use of RAI (P < .001 and P = .006, respectively). CONCLUSIONS: The specialty of the primary decision maker, the number of providers administering RAI, and having access to a tumor board were associated significantly with the use of RAI for stage I thyroid cancer. The findings have implications for addressing nonclinical variation between hospitals, with a marked heterogeneity in decision making suggesting that standardization of care will be challenging.

Effect of including cancer-specific variables on models examining short-term outcomes.

BACKGROUND: The American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) generally has not collected cancer-specific variables. Because increasing numbers of studies are using ACS NSQIP data to study cancer surgery, the objectives of the current study were 1) to examine differences between existing ACS NSQIP variables and cancer registry variables, and 2) to determine whether the addition of cancer-specific variables improves modeling of short-term outcomes. METHODS: Data from patients in the ACS NSQIP and National Cancer Data Base (NCDB) who underwent colorectal resection for cancer were linked (2006-2008). By using regression methods, the relative importance of cancer staging and neoadjuvant therapy variables were assessed along with their effects on morbidity, serious morbidity, and mortality. RESULTS: From 146 hospitals, 11,405 patients were identified who underwent surgery for colorectal cancer (colon, 85%; rectum, 15%). The NCDB metastatic cancer variable and the ACS NSQIP disseminated cancer variables agreed marginally (Cohen kappa coefficient, 0.454). For mortality, only the ACS NSQIP disseminated cancer variable and the NCDB stage IV variable were identified as important predictors; whereas the variables stage I through III, tumor (T)-classification, and lymph node (N)-classification were not selected. Cancer stage variables were inconsistently important for serious morbidity (stage IV, T-classification), superficial surgical site infection (N-classification), venous thromboembolism (metastatic cancer), and pneumonia (T-classification). With respect to neoadjuvant therapy, ACS NSQIP and NCDB variables agreed moderately (kappa, 0.570) and predicted superficial surgical site infection, serious morbidity, and organ space surgical site infection. The model fit was similar regardless of the inclusion of stage and neoadjuvant therapy variables. CONCLUSIONS: Although advanced disease stage and neoadjuvant therapy variables were predictors of short-term outcomes, their inclusion did not improve the models.

The relationship between extent of thyroid cancer surgery and use of radioactive iodine.

UNLABELLED: By linking surgeon surveys to the National Cancer Database, we found that surgeons' tendency to perform more extensive thyroid resection is associated with greater use of radioactive iodine for stage I thyroid cancer. OBJECTIVE: To determine the relationships between surgeon recommendations for extent of resection and radioactive iodine use in low-risk thyroid cancer. BACKGROUND: There has been an increase in thyroid cancer treatment intensity; the relationship between extent of resection and medical treatment with radioactive iodine remains unknown. METHODS: We randomly surveyed thyroid surgeons affiliated with 368 hospitals with Commission on Cancer-accredited cancer programs. Survey responses were linked to the National Cancer Database. The relationship between extent of resection and the proportion of the American Joint Committee on Cancer stage I well-differentiated thyroid cancer patients treated with radioactive iodine after total thyroidectomy was assessed with multivariable weighted regression, controlling for hospital and surgeon characteristics. RESULTS: The survey response rate was 70% (560/804). Surgeons who recommend total thyroidectomy over lobectomy for subcentimeter unifocal thyroid cancer were significantly more likely to recommend prophylactic central lymph node dissection for thyroid cancer regardless of tumor size (P < 0.001). They were also more likely to favor radioactive iodine in patients with intrathyroidal unifocal cancer ≤1 cm (P = 0.001), 1.1-2 cm (P = 0.004), as well as intrathyroidal multifocal cancer ≤1 cm (P = 0.004). In multivariable analysis, high hospital case volume, fewer surgeon years of experience, general surgery specialty, and preference for more extensive resection were independently associated with greater hospital-level use of radioactive iodine for stage I disease. CONCLUSIONS: In addition to surgeon experience and specialty, surgeons' tendency to perform more extensive thyroid resection is associated with greater use of radioactive iodine for stage I thyroid cancer.

Effect of postoperative complications on adjuvant chemotherapy use for stage III colon cancer.

OBJECTIVE: The National Quality Forum has endorsed a quality metric concerning the use of adjuvant chemotherapy administration in stage III colon cancer, yet a substantial treatment gap exists. Our objective was to evaluate the association of postoperative complications on the use of adjuvant therapy after colectomy for cancer. PATIENTS AND METHODS: Data from the American College of Surgeons National Surgical Quality Improvement Program and National Cancer Data Base were linked to augment cancer registry information with robust clinical data on comorbidities and postoperative complications (2006-2008). The association of complications on adjuvant chemotherapy use was assessed using hierarchical multivariable regression models. RESULTS: From 126 hospitals, 2368 patients underwent resection for stage III colon adenocarcinoma. Overall utilization of adjuvant chemotherapy was 63.2% (1497/2368). Of the 871 patients who did not receive chemotherapy, 652 met National Quality Forum exclusion criteria: death, severe comorbidity, refusal of care, advanced age (≥80 years), or prior malignancy. Of the remaining 219 patients, 19.1% (42/219) had 1 or more serious postoperative complications (eg, pneumonia, pulmonary failure). After accounting for the aforementioned potential explanations, the utilization rate was 87.2% (1497/1716). The strongest predictors of adjuvant chemotherapy omission were prolonged postoperative ventilation, renal failure, reintubation, and pneumonia (all Ps < 0.05). Superficial surgical site infection did not decrease adjuvant therapy receipt but delayed the time to its use by 3-fold. Serious complications increased time to chemotherapy by 65%. Abscess/anastomotic leak increased time to adjuvant chemotherapy by more than 5-fold. CONCLUSIONS: Serious postoperative complications explained nearly 20% of the adjuvant chemotherapy treatment gap for patients with stage III colon cancer. The use of clinical data remains important when judging provider performance.

Comparison of cases captured in the national cancer data base with those in population-based central cancer registries.

BACKGROUND: The National Cancer Data Base (NCDB) is a large, geographically diverse hospital-based cancer registry that has been used to study factors related to cancer diagnosis, treatment, and survival. The primary purpose of this study was to compare the case counts and characteristics of patients in NCDB with population-based registries reported in the United States Cancer Statistics (USCS). METHODS: Cancer case counts from NCDB were compared to case counts from USCS to measure NCDB's case coverage, or the percentage of cases captured. Case coverage was examined by a variety of characteristics, including state of residence, race/ethnicity, age, and primary cancer site. RESULTS: The overall NCDB case coverage was 67.4 %, ranging from a high of 88.7 % for Delaware to a low of 27.1 % for Arizona. Case coverage for white, black, and Asian/Pacific Islander cases was high (64.7 % to 67.4 %), but it was much lower for American Indians/Alaskan Natives (32.8 %) and those of Hispanic ethnicity (51.1 %). Among the elderly (aged 65 + years), case coverage is much lower compared to persons younger than 65 (63.0 % and 73.0 %, respectively). Case coverage also varied widely by site, with the highest being cervix (77.9 %) and the lowest being melanoma (50.6 %). CONCLUSIONS: This study highlights the geographic- and site-specific variation in NCDB case coverage, primarily as a result of NCDB facility presence and data collection and processing protocols. These findings illustrate the strengths and limitations of NCDB as a resource for nationwide data on cancer diagnosis, treatment, and survival.

Surgeon training and use of radioactive iodine in stage I thyroid cancer patients.

BACKGROUND: The majority of thyroid cancer diagnoses in the United States are stage I well-differentiated cancer. The use of radioactive iodine (RAI) in these low-risk patients has increased over time. The role of surgeon training in decision making regarding treatment with RAI is unknown. METHODS: Thyroid surgeons affiliated with 368 hospitals associated with the US National Cancer Database (NCDB) were surveyed. Survey data were linked to the NCDB data. A multivariable weighted analysis controlling for surgeon and hospital characteristics was conducted to examine the relationship between surgeon training, continuing education and hospital-level RAI use for stage I well-differentiated thyroid cancer. RESULTS: The response rate was 70% (560 of 804). In both univariate and multivariable analysis controlling for hospital case volume, practice setting and surgeon specialty, training with a thyroid surgeon was associated with less RAI use for stage I thyroid cancer (P = 0.022 and 0.028, respectively). Attending one or more professional society meetings a year was associated with a lower rate of hospital-level RAI use in univariate analysis (P = 0.044) but not multivariable analysis. CONCLUSIONS: Training with a surgeon or group of surgeons who focus on thyroid surgery was associated with a lower proportion of stage I thyroid cancer patients receiving RAI after total thyroidectomy. This study emphasizes the importance of surgeon training in hospital practice patterns.

Effect of including cancer-specific variables on risk-adjusted hospital surgical quality comparisons.

BACKGROUND: Quality initiatives are increasingly focusing on the quality of oncologic surgery. However, there is concern that a lack of cancer-specific variables may make risk-adjusted hospital quality comparisons inadequate. Our objective was to assess whether hospital quality rankings for cancer surgery are influenced by the addition of cancer-specific variables to the risk-adjusted models. METHODS: Patients from the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) and National Cancer Data Base (NCDB) who underwent colon or rectal resection for cancer were linked (2006-2008). Hierarchical models were developed predicting ACS NSQIP outcomes based on ACS NSQIP only vs a model using NSQIP and NCDB-derived cancer variables (e.g., stage and neoadjuvant therapy). Changes in hospital quality rankings were compared. RESULTS: A total of 11,405 patients underwent colon (n = 9,678, 146 hospitals) or rectal (n = 1,727, 135 hospitals) resection for cancer (2006-2008). Hospital-level complication rates (and standard deviation) after colon surgery were 2.2 % (±2.7 %) for mortality and 17.2 % (±8.7 %) for serious morbidity. After rectal cancer resection, complication rates were 0.9 % (±3.8 %) for mortality and 22.3 % (±20.4 %) for serious morbidity. When cancer-specific variables were included in risk-adjustment, outlier agreement was very good (kappa >0.85), and hospital odds ratio correlations were nearly identical (R > 0.98) for all outcomes assessed. Median changes in hospital rankings with the addition of the cancer-specific variables ranged from 1 to 2 after colon resection to 2-4 after rectal resection. CONCLUSIONS: Addition of the available cancer-specific variables to risk-adjustment models did not affect hospital quality rankings for cancer surgery. Existing ACS NSQIP risk-adjustment variables appears to be sufficient for accurate comparisons of hospital quality.

Deletion of Slc26a6 alters the stoichiometry of apical Cl-/HCO-3 exchange in mouse pancreatic duct.

To define the stoichiometry and molecular identity of the Cl(-)/HCO(3)(-) exchanger in the apical membrane of pancreatic duct cells, changes in luminal pH and volume were measured simultaneously in interlobular pancreatic ducts isolated from wild-type and Slc26a6-null mice. Transepithelial fluxes of HCO(3)(-) and Cl(-) were measured in the presence of anion gradients favoring rapid exchange of intracellular HCO(3)(-) with luminal Cl(-) in cAMP-stimulated ducts. The flux ratio of Cl(-) absorption/HCO(3)(-) secretion was ∼0.7 in wild-type ducts and ∼1.4 in Slc26a6(-/-) ducts where a different Cl(-)/HCO(3)(-) exchanger, most likely SLC26A3, was found to be active. Interactions between Cl(-)/HCO(3)(-) exchange and cystic fibrosis transmembrane conductance regulator (CFTR) in cAMP-stimulated ducts were examined by measuring the recovery of intracellular pH after alkali-loading by acetate prepulse. Hyperpolarization induced by luminal application of CFTRinh-172 enhanced HCO(3)(-) efflux across the apical membrane via SLC26A6 in wild-type ducts but significantly reduced HCO(3)(-) efflux in Slc26a6(-/-) ducts. In microperfused wild-type ducts, removal of luminal Cl(-), or luminal application of dihydro-4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid to inhibit SLC26A6, caused membrane hyperpolarization, which was abolished in Slc26a6(-/-) ducts. In conclusion, we have demonstrated that deletion of Slc26a6 alters the apparent stoichiometry of apical Cl(-)/HCO(3)(-) exchange in native pancreatic duct. Our results are consistent with SLC26A6 mediating 1:2 Cl(-)/HCO(3)(-) exchange, and the exchanger upregulated in its absence, most probably SLC26A3, mediating 2:1 exchange.

Effect of histologic subtype on treatment and outcomes for esophageal cancer in the United States.

BACKGROUND: Esophageal adenocarcinoma (AC) and squamous cell carcinoma (SCC) have distinct clinico-pathologic characteristics; however, it is unclear whether treatment patterns differ by histologic subtype. The objective of this study was to examine differences in treatment use and outcomes by histologic subtype for esophageal cancer in the United States. METHODS: From the National Cancer Data Base, patients with esophageal cancer were identified. Regression models were formulated to assess the influence of histologic subtype on treatment use and overall survival. RESULTS: From 1998 to 2007, 80,961 patients were identified with esophageal cancer in the United States. A higher percentage of patients with nonmetastatic AC underwent surgical resection compared with patients with nonmetastatic SCC (AC, 65.7%; SCC, 36.0%; P<.001), who were more often treated with chemoradiotherapy alone (AC, 25.7%; SCC, 54.1%; P<.001). High-volume academic centers used surgery more frequently for both AC and SCC than did other centers, yet even at high-volume academic centers, surgery was used much less often to treat SCC than AC (AC, 79.3%; SCC, 53.7%; P<.001). The likelihood of operative treatment for nonmetastatic disease was significantly lower in patients with SCC compared with patients with AC (P<.001). Overall survival was lower for patients with stage II/III disease of either histologic subtype treated with chemoradiotherapy alone compared with surgery plus chemoradiotherapy (P<.001). CONCLUSION: A large proportion of patients with esophageal cancer are being treated nonoperatively, and treatment use varies according to tumor histology, particularly by center type.

Assessment of the quality of medical care among patients with early stage prostate cancer undergoing expectant management in the United States.

PURPOSE: Given the increased attention to the quality and cost of medical care, the Institute of Medicine and Centers for Medicare and Medicaid Services have called for performance measurement and reporting. The clinical management of prostate cancer has been outlined, yet is not intended to describe quality prostate cancer care. Therefore, RAND researchers developed quality indicators for early stage prostate cancer. The ACoS (American College of Surgeons) used these indicators to perform the first national assessment to our knowledge of the quality of care among men with early stage prostate cancer undergoing expectant management. MATERIALS AND METHODS: Information from medical records was abstracted for evidence of compliance with the RAND indicators (structure and process). Weighted and stratified proportions were calculated to assess indicator compliance. Logistic regression models were fit and evaluated by hospital type and patient factors. RESULTS: A weighted and stratified total of 13,876 early stage prostate cancer cases on expectant management in 2000 to 2001 were investigated. Compliance with structural indicators was high (greater than 80%) and compliance with process indicators varied (19% to 87%). Differences in process indicators were observed from models by hospital type and comorbid conditions, but not for age, race or insurance status. CONCLUSIONS: Using the RAND quality indicators this study revealed several process areas for quality improvement among men with early stage prostate cancer on expectant management in the United States. Efforts to improve the quality of early stage prostate cancer care need to move beyond the paradigm of age, race and insurance status.

A match made in heaven? Trying to combine ACS-NSQIP and NCDB databases.

BACKGROUND: As part of a larger study evaluating breast cancer care, we attempted to validate our matching strategies between the National Cancer Data Base (NCDB) and ACS National Surgical Quality Improvement Program (ACS-NSQIP). METHODS: Using 2002-2006 data, we attempted to match cases by a three-tiered approach. Three groups resulted: (1) successfully matched, (2) NCDB case with no corresponding match in ACS-NSQIP, and (3) ACS-NSQIP case with no match in NCDB. Single institution (University of Utah) data were used for a nested validation study of the unmatched groups. RESULTS: The initial match yielded a 23.4% net match rate (rate of 8.6% at the University of Utah). In subset review of unmatched University of Utah cancer registry cases (NCDB, n = 153), 56% (n = 86) of cases had their index surgery at the University of Utah, with 15 potential matches in the unmatched ACS-NSQIP data using age and date of surgery and no potential match for 41 cases. Twenty-five remaining cases had a potential surgery date match if age was varied by 1 y with 18 confirmed matches. Review of unmatched ACS-NSQIP cases (n = 107) yielded 15 potential matches in the University of Utah cancer registry, with no potential match for 63 cases. Twenty-nine cases had a potential surgery date match if age was varied, with 26 confirmed matches. Review of ACS-NSQIP cases from 2006 for cancer status and stage revealed two cancer patients who were not in the cancer registry. CONCLUSIONS: Linking ACS-NSQIP and NCDB without a captive patient population results in low overall match rates due, in part, to specific inclusion criteria and different variable definitions for each database.

SLC26 anion exchangers of guinea pig pancreatic duct: molecular cloning and functional characterization.

The secretin-stimulated human pancreatic duct secretes HCO(3)(-)-rich fluid essential for normal digestion. Optimal stimulation of pancreatic HCO(3)(-) secretion likely requires coupled activities of the cystic fibrosis transmembrane regulator (CFTR) anion channel and apical SLC26 Cl(-)/HCO(3)(-) exchangers. However, whereas stimulated human and guinea pig pancreatic ducts secrete ∼140 mM HCO(3)(-) or more, mouse and rat ducts secrete ∼40-70 mM HCO(3)(-). Moreover, the axial distribution and physiological roles of SLC26 anion exchangers in pancreatic duct secretory processes remain controversial and may vary among mammalian species. Thus the property of high HCO(3)(-) secretion shared by human and guinea pig pancreatic ducts prompted us to clone from guinea pig pancreatic duct cDNAs encoding Slc26a3, Slc26a6, and Slc26a11 polypeptides. We then functionally characterized these anion transporters in Xenopus oocytes and human embryonic kidney (HEK) 293 cells. In Xenopus oocytes, gpSlc26a3 mediated only Cl(-)/Cl(-) exchange and electroneutral Cl(-)/HCO(3)(-) exchange. gpSlc26a6 in Xenopus oocytes mediated Cl(-)/Cl(-) exchange and bidirectional exchange of Cl(-) for oxalate and sulfate, but Cl(-)/HCO(3)(-) exchange was detected only in HEK 293 cells. gpSlc26a11 in Xenopus oocytes exhibited pH-dependent Cl(-), oxalate, and sulfate transport but no detectable Cl(-)/HCO(3)(-) exchange. The three gpSlc26 anion transporters exhibited distinct pharmacological profiles of (36)Cl(-) influx, including partial sensitivity to CFTR inhibitors Inh-172 and GlyH101, but only Slc26a11 was inhibited by PPQ-102. This first molecular and functional assessment of recombinant SLC26 anion transporters from guinea pig pancreatic duct enhances our understanding of pancreatic HCO(3)(-) secretion in species that share a high HCO(3)(-) secretory output.

Functional characterization and modified rescue of novel AE1 mutation R730C associated with overhydrated cation leak stomatocytosis.

We report the novel, heterozygous AE1 mutation R730C associated with dominant, overhydrated, cation leak stomatocytosis and well-compensated anemia. Parallel elevations of red blood cell cation leak and ouabain-sensitive Na(+) efflux (pump activity) were apparently unaccompanied by increased erythroid cation channel-like activity, and defined ouabain-insensitive Na(+) efflux pathways of nystatin-treated cells were reduced. Epitope-tagged AE1 R730C at the Xenopus laevis oocyte surface exhibited severely reduced Cl(-) transport insensitive to rescue by glycophorin A (GPA) coexpression or by methanethiosulfonate (MTS) treatment. AE1 mutant R730K preserved Cl(-) transport activity, but R730 substitution with I, E, or H inactivated Cl(-) transport. AE1 R730C expression substantially increased endogenous oocyte Na(+)-K(+)-ATPase-mediated (86)Rb(+) influx, but ouabain-insensitive flux was minimally increased and GPA-insensitive. The reduced AE1 R730C-mediated sulfate influx did not exhibit the wild-type pattern of stimulation by acidic extracellular pH (pH(o)) and, unexpectedly, was partially rescued by exposure to sodium 2-sulfonatoethyl methanethiosulfonate (MTSES) but not to 2-aminoethyl methanethiosulfonate hydrobromide (MTSEA) or 2-(trimethylammonium)ethyl methanethiosulfonate bromide (MTSET). AE1 R730E correspondingly exhibited acid pH(o)-stimulated sulfate uptake at rates exceeding those of wild-type AE1 and AE1 R730K, whereas mutants R730I and R730H were inactive and pH(o) insensitive. MTSES-treated oocytes expressing AE1 R730C and untreated oocytes expressing AE1 R730E also exhibited unprecedented stimulation of Cl(-) influx by acid pH(o). Thus recombinant cation-leak stomatocytosis mutant AE1 R730C exhibits severely reduced anion transport unaccompanied by increased Rb(+) and Li(+) influxes. Selective rescue of acid pH(o)-stimulated sulfate uptake and conferral of acid pH(o)-stimulated Cl(-) influx, by AE1 R730E and MTSES-treated R730C, define residue R730 as critical to selectivity and regulation of anion transport by AE1.

Native and recombinant Slc26a3 (downregulated in adenoma, Dra) do not exhibit properties of 2Cl-/1HCO3- exchange.

The recent proposal that Dra/Slc26a3 mediates electrogenic 2Cl(-)/1HCO(3)(-) exchange suggests a required revision of classical concepts of electroneutral Cl(-) transport across epithelia such as the intestine. We investigated 1) the effect of endogenous Dra Cl(-)/HCO(3)(-) activity on apical membrane potential (V(a)) of the cecal surface epithelium using wild-type (WT) and knockout (KO) mice; and 2) the electrical properties of Cl(-)/(OH(-))HCO(3)(-) exchange by mouse and human orthologs of Dra expressed in Xenopus oocytes. Ex vivo (36)Cl(-) fluxes and microfluorometry revealed that cecal Cl(-)/HCO(3)(-) exchange was abolished in the Dra KO without concordant changes in short-circuit current. In microelectrode studies, baseline V(a) of Dra KO surface epithelium was slightly hyperpolarized relative to WT but depolarized to the same extent as WT during luminal Cl(-) substitution. Subsequent studies indicated that Cl(-)-dependent V(a) depolarization requires the anion channel Cftr. Oocyte studies demonstrated that Dra-mediated exchange of intracellular Cl(-) for extracellular HCO(3)(-) is accompanied by slow hyperpolarization and a modest outward current, but that the steady-state current-voltage relationship is unaffected by Cl(-) removal or pharmacological blockade. Further, Dra-dependent (36)Cl(-) efflux was voltage-insensitive in oocytes coexpressing the cation channels ENaC or ROMK. We conclude that 1) endogenous Dra and recombinant human/mouse Dra orthologs do not exhibit electrogenic 2Cl(-)/1HCO(3)(-) exchange; and 2) acute induction of Dra Cl(-)/HCO(3)(-) exchange is associated with secondary membrane potential changes representing homeostatic responses. Thus, participation of Dra in coupled NaCl absorption and in uncoupled HCO(3)(-) secretion remains compatible with electroneutrality of these processes, and with the utility of electroneutral transport models for predicting epithelial responses in health and disease.

Loss-of-function and gain-of-function phenotypes of stomatocytosis mutant RhAG F65S.

Four patients with overhydrated cation leak stomatocytosis (OHSt) exhibited the heterozygous RhAG missense mutation F65S. OHSt erythrocytes were osmotically fragile, with elevated Na and decreased K contents and increased cation channel-like activity. Xenopus oocytes expressing wild-type RhAG and RhAG F65S exhibited increased ouabain and bumetanide-resistant uptake of Li(+) and (86)Rb(+), with secondarily increased (86)Rb(+) influx sensitive to ouabain and to bumetanide. Increased RhAG-associated (14)C-methylammonium (MA) influx was severely reduced in RhAG F65S-expressing oocytes. RhAG-associated influxes of Li(+), (86)Rb(+), and (14)C-MA were pharmacologically distinct, and Li(+) uptakes associated with RhAG and RhAG F65S were differentially inhibited by NH(4)(+) and Gd(3+). RhAG-expressing oocytes were acidified and depolarized by 5 mM bath NH(3)/NH(4)(+), but alkalinized and depolarized by subsequent bath exposure to 5 mM methylammonium chloride (MA/MA(+)). RhAG F65S-expressing oocytes exhibited near-wild-type responses to NH(4)Cl, but MA/MA(+) elicited attenuated alkalinization and strong hyperpolarization. Expression of RhAG or RhAG F65S increased steady-state cation currents unaltered by bath Li(+) substitution or bath addition of 5 mM NH(4)Cl or MA/MA(+). These oocyte studies suggest that 1) RhAG expression increases oocyte transport of NH(3)/NH(4)(+) and MA/MA(+); 2) RhAG F65S exhibits gain-of-function phenotypes of increased cation conductance/permeability, and loss-of-function phenotypes of decreased and modified MA/MA(+) transport, and decreased NH(3)/NH(4)(+)-associated depolarization; and 3) RhAG transports NH(3)/NH(4)(+) and MA/MA(+) by distinct mechanisms, and/or the substrates elicit distinct cellular responses. Thus, RhAG F65S is a loss-of-function mutation for amine transport. The altered oocyte intracellular pH, membrane potential, and currents associated with RhAG or RhAG F65S expression may reflect distinct transport mechanisms.