Cancer Epidemiology in Hispanic Populations: An Analysis of Funded Observational Research at the National Cancer Institute.

BACKGROUND: More than 62 million people self-identified as Hispanic/Latino (H/L) in the 2020 United States census. The U.S. H/L population has higher burden of certain cancers compared with their non-Hispanic White counterparts. METHODS: Key term search using the NIH Query/View/Report (QVR) system, along with Research, Condition, and Disease Categorization codes identified cancer epidemiology research grants in H/L populations funded by the NCI as a primary or secondary funder from fiscal years 2016 through 2021. Three reviewers identified eligible grants based on specified inclusion/exclusion criteria and a codebook for consistency extracting key characteristics. RESULTS: A total of 450 grants were identified through the QVR system using key words related to H/Ls; 41 cancer epidemiology grants remained after applying exclusion criteria. These grants contained specific aims focused on H/Ls (32%) or included H/Ls as part of a racial/ethnic comparison (68%). NCI was the primary funder of the majority of the grants (85%), and most of the research grants focused on cancer etiology (44%) and/or survivorship (49%). Few grants (10%) investigated environmental exposures. CONCLUSIONS: This article provides an overview of NCI-funded cancer epidemiology research in H/L populations from 2016 to 2021. Future cancer epidemiology research should reflect the changing dynamics of the U.S. demography with diverse, representative populations and well-characterized ethnicity. IMPACT: Research that carefully measures the relevant biological, environmental, behavioral, psychologic, sociocultural, and clinical risk factors will be critical to better understanding the nuanced patterns influencing cancer-related outcomes in the heterogenous H/L population.

Epidemiologic Research of Rare Cancers: Trends, Resources, and Challenges.

BACKGROUND: The goals of this project were to assess the status of NCI's rare cancer-focused population science research managed by the Division of Cancer Control and Population Sciences (DCCPS), to develop a framework for evaluation of rare cancer research activities, and to review available resources to study rare cancers. METHODS: Cancer types with an overall age-adjusted incidence rate of less than 20 cases per 100,000 individuals were identified using NCI Surveillance, Epidemiology and End Results (SEER) Program data. SEER data were utilized to develop a framework based on statistical commonalities. A portfolio analysis of DCCPS-supported active grants and a review of three genomic databases were conducted. RESULTS: For the 45 rare cancer types included in the analysis, 123 active DCCPS-supported rare cancer-focused grants were identified, of which the highest percentage (18.7%) focused on ovarian cancer. The developed framework revealed five clusters of rare cancer types. The cluster with the highest number of grants (n = 43) and grants per cancer type (10.8) was the cluster that included cancer types of higher incidence, average to better survival, and high prevalence (in comparison with other rare cancers). Resource review revealed rare cancers are represented in available genomic resources, but to a lesser extent compared with more common cancers. CONCLUSIONS: This article provides an overview of the rare cancer-focused population sciences research landscape as well as information on gaps and opportunities. IMPACT: The findings of this article can be used to develop efficient and comprehensive strategies to accelerate rare cancer research.See related commentary by James V. Lacey Jr, p. 1300.

Identification of a 10/10 matched donor for patients with an uncommon haplotype is unlikely.

BACKGROUND: Despite over 6 million subjects contributing to the National Marrow Donor Program human leukocyte antigen (HLA) haplotype frequency reference data (HFD), haplotypes cannot be predicted from the HLA assignments of some patients searching for an unrelated donor (URD) in the Be The Match Registry®. We aimed to determine the incidence of these patient searches and whether haplotypes lacking from the HFD can be found among the low-resolution typed URD pool. MATERIALS AND METHODS: New NMDP searches with uncommon patient haplotypes (UPH), defined as a lack of haplotype pairs in any single ethnic group in the HFD based upon HLA-A˜C˜B˜DRB1˜DQB1, were identified. Each search had up to 20 potential 10/10 or 8/8 URDs typed to determine the likelihood of an allele match. RESULTS: The incidence of patient searches without haplotype pairs in a single ethnic group in the HFD was 1.2% (N=144 out of 12,172) and a majority of these patients (117; 81%) had one uncommon haplotype previously uncharacterized in the HFD. Non-White patients had the highest incidence of UPH. Importantly, no patients with UPH had a 10/10 URD identified. The transplant rate among UPH patients was 15%, and a majority of these patients utilized cord blood units as their transplant stem cell source. CONCLUSION: Therefore, the HLA HFD that informs the HapLogic matching algorithm is thorough as UPH patient searches were infrequent. Since such patients are highly unlikely to have a fully 10/10 matched URD identified, this study supports the identification of alternative stem cell sources including cord blood or a mismatched URD early in the search process.

Prevalence and correlates of receiving and sharing high-penetrance cancer genetic test results: findings from the Health Information National Trends Survey.

BACKGROUND/AIMS: The aim of this study was to explore the prevalence and correlates of receiving and sharing high-penetrance cancer genetic test results. METHODS: Participants completed the population-based, cross-sectional 2013 Health Information National Trends Survey. We examined sociodemographic characteristics of participants reporting having had BRCA1/2 or Lynch syndrome genetic testing, and sociodemographic and psychosocial correlates of sharing test results with health professionals and family members. RESULTS: Participants who underwent BRCA1/2 or Lynch syndrome genetic testing (n = 77; 2.42% of respondents) were more likely to be female and to have a family or personal history of cancer than those not undergoing testing. Approximately three-quarters of participants shared results with health professionals and three-quarters with their family; only 4% did not share results with anyone. Participants who shared results with health professionals reported greater optimism, self-efficacy for health management, and trust in information from their doctors. Participants who shared results with their family were more likely to be female and to have a personal history of cancer, and had greater self-efficacy for health management, perceived less ambiguity in cancer prevention recommendations, and lower cancer prevention fatalism. CONCLUSIONS: We identified several novel psychosocial correlates of sharing genetic information. Health professionals may use this information to identify patients less likely to share information with at-risk family members.

Management of the pediatric patient with choledocholithiasis in an era of advanced minimally invasive techniques.

BACKGROUND: The treatment algorithm for children with suspected choledocholithiasis is not well established because the breadth of minimally invasive surgery and endoscopic techniques continues to evolve. We reviewed our experience with common bile duct explorations (CBDEs) in order to detail the techniques used and describe the rate of complications of laparoscopic CBDE in children. SUBJECTS AND METHODS: As part of an Institutional Review Board-approved study, medical records were reviewed for all patients, 1 month to 21 years of age, undergoing a cholecystectomy at a large tertiary-care children's hospital over an 11-year period. Those undergoing an intraoperative cholangiogram (IOC) were documented, and operative reports and postoperative records were examined. RESULTS: Over 11 years, 464 cholecystectomies were performed, and an IOC was attempted on 174 patients with a 97% success rate (n=168). Of the patients who underwent a cholangiogram, 30% (n=52) had an obstructing stone. Laparoscopic CBDE was attempted in 50 patients with a conversion rate of 8%. Postoperatively, 3 CBDE patients underwent endoscopic retrograde cholangiopancreatography (ERCP) for the following reasons: retained stone (n=1), persistent hyperbilirubinemia (n=1), and bile leak (n=1). CONCLUSIONS: Laparoscopic CBDE is a safe initial approach to choledocholethiasis and is successful at relieving the obstruction the majority of the time. The authors conclude that in situations where there is limited availability of ERCP, laparoscopic CBDE should be considered as a first step in the management of obstructive choledocholethiasis.

Influence of quercetin-rich food intake on microRNA expression in lung cancer tissues.

BACKGROUND: Epidemiologic studies have reported that frequent consumption of quercetin-rich foods is inversely associated with lung cancer incidence. A quercetin-rich diet might modulate microRNA (miR) expression; however, this mechanism has not been fully examined. METHODS: miR expression data were measured by a custom-made array in formalin-fixed paraffin-embedded tissue samples from 264 lung cancer cases (144 adenocarcinomas and 120 squamous cell carcinomas). Intake of quercetin-rich foods was derived from a food-frequency questionnaire. In individual-miR-based analyses, we compared the expression of miRs (n = 198) between lung cancer cases consuming high versus low quercetin-rich food intake using multivariate ANOVA tests. In family-miR-based analyses, we used Functional Class Scoring (FCS) to assess differential effect on biologically functional miR families. We accounted for multiple testing using 10,000 global permutations (significance at P(global) < 0.10). All multivariate analyses were conducted separately by histology and by smoking status (former and current smokers). RESULTS: Family-based analyses showed that a quercetin-rich diet differentiated miR expression profiles of the tumor suppressor let-7 family among adenocarcinomas (P(FCS) < 0.001). Other significantly differentiated miR families included carcinogenesis-related miR-146, miR-26, and miR-17 (P (FCS) < 0.05). In individual-based analyses, we found that among former and current smokers with adenocarcinoma, 33 miRs were observed to be differentiated between highest and lowest quercetin-rich food consumers (23 expected by chance; P(global) = 0.047). CONCLUSIONS: We observed differential expression of key biologically functional miRs between high versus low consumers of quercetin-rich foods in adenocarcinoma cases. IMPACT: Our findings provide preliminary evidence on the mechanism underlying quercetin-related lung carcinogenesis.

Helicobacter pylori seropositivity and risk of lung cancer.

Lung cancer is the leading cause of cancer mortality worldwide. Helicobacter pylori (H. pylori) is a risk factor for distal stomach cancer, and a few small studies have suggested that H. pylori may be a potential risk factor for lung cancer. To test this hypothesis, we conducted a study of 350 lung adenocarcinoma cases, 350 squamous cell carcinoma cases, and 700 controls nested within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study (ATBC) cohort of male Finnish smokers. Controls were one-to-one matched by age and date of baseline serum draw. Using enzyme-linked immunosorbent assays to detect immunoglobulin G antibodies against H. pylori whole-cell and cytotoxin-associated gene (CagA) antigens, we calculated odds ratios (ORs) and 95% confidence intervals (95% CIs) for associations between H. pylori seropositivity and lung cancer risk using conditional logistic regression. H. pylori seropositivity was detected in 79.7% of cases and 78.5% of controls. After adjusting for pack-years and cigarettes smoked per day, H. pylori seropositivity was not associated with either adenocarcinoma (OR: 1.1, 95% CI: 0.75-1.6) or squamous cell carcinoma (OR: 1.1, 95% CI: 0.77-1.7). Results were similar for CagA-negative and CagA-positive H. pylori seropositivity. Despite earlier small studies suggesting that H. pylori may contribute to lung carcinogenesis, H. pylori seropositivity does not appear to be associated with lung cancer.

GSTM1 and GSTT1 copy numbers and mRNA expression in lung cancer.

Large fractions of the human population do not express GSTM1 and GSTT1 (GSTM1/T1) enzymes because of deletions in these genes. These variations affect xenobiotic metabolism and have been evaluated in relation to lung cancer risk, mostly based on null/present gene models. We measured GSTM1/T1 heterozygous deletions, not tested in genome-wide association studies, in 2,120 controls and 2,100 cases from the Environment And Genetics in Lung cancer Etiology (EAGLE) study. We evaluated their effect on mRNA expression on lung tissue and peripheral blood samples and their association with lung cancer risk overall and by histology types. We tested the null/present, dominant, and additive models using logistic regression. Cigarette smoking and gender were studied as possible modifiers. Gene expression from blood and lung tissue cells was strongly down regulated in subjects carrying GSTM1/T1 deletions by both trend and dominant models (P < 0.001). In contrast to the null/present model, analyses distinguishing subjects with 0, 1, or 2 GSTM1/T1 deletions revealed several associations. There was a decreased lung cancer risk in never-smokers (OR = 0.44; 95%CI = 0.23-0.82; P = 0.01) and women (OR = 0.50; 95%CI = 0.28-0.90; P = 0.02) carrying 1 or 2 GSTM1 deletions. Analogously, male smokers had an increased risk (OR = 1.13; 95%CI = 1.0-1.28; P = 0.05) and women a decreased risk (OR = 0.78; 95%CI = 0.63-0.97; P = 0.02) for increasing GSTT1 deletions. The corresponding gene smoking and gene-gender interactions were significant (P < 0.05). Our results suggest that decreased activity of GSTM1/T1 enzymes elevates lung cancer risk in male smokers, likely due to impaired carcinogens' detoxification. A protective effect of the same mutations may be operative in never-smokers and women, possibly because of reduced activity of other genotoxic chemicals.

Rapid acute treatment of agitation in individuals with schizophrenia: multicentre, randomised, placebo-controlled study of inhaled loxapine.

BACKGROUND: There is a need for a rapid-acting, non-injection, acute treatment for agitation. AIMS: To evaluate inhaled loxapine for acute treatment of agitation in schizophrenia. METHOD: This phase III, randomised, double-blind, placebo-controlled, parallel-group study (ClinicalTrials.gov number NCT00628589) enrolled 344 individuals who received one, two or three doses of inhaled loxapine (5 or 10 mg) or a placebo. Lorazepam rescue was permitted after dose two. The primary efficacy end-point was change from baseline in Positive and Negative Syndrome Scale-Excited Component (PANSS-EC) 2 h after dose one. The key secondary end-point was Clinical Global Impression-Improvement scale (CGI-I) score 2 h after dose one. RESULTS: Inhaled loxapine (5 and 10 mg) significantly reduced agitation compared with placebo as assessed by primary and key secondary end-points. Reduced PANSS-EC score was evident 10 min after dose one with both 5 and 10 mg doses. Inhaled loxapine was well tolerated, and the most common adverse events were known effects of loxapine or minor oral effects common with inhaled medications. CONCLUSIONS: Inhaled loxapine provided a rapid, well-tolerated acute treatment for agitation in people with schizophrenia.

Identifying rheumatoid arthritis susceptibility genes using high-dimensional methods.

Although several genes (including a strong effect in the human leukocyte antigen (HLA) region) and some environmental factors have been implicated to cause susceptibility to rheumatoid arthritis (RA), the etiology of the disease is not completely understood. The ability to screen the entire genome for association to complex diseases has great potential for identifying gene effects. However, the efficiency of gene detection in this situation may be improved by methods specifically designed for high-dimensional data. The aim of this study was to compare how three different statistical approaches, multifactor dimensionality reduction (MDR), random forests (RF), and an omnibus approach, worked in identifying gene effects (including gene-gene interaction) associated with RA. We developed a test set of genes based on previous linkage and association findings and tested all three methods. In the presence of the HLA shared-epitope factor, other genes showed weaker effects. All three methods detected SNPs in PTPN22 and TRAF1-C5 as being important. But we did not detect any new genes in this study. We conclude that the three high-dimensional methods are useful as an initial screening for gene associations to identify promising genes for further modeling and additional replication studies.

Carotenoids and the risk of developing lung cancer: a systematic review.

BACKGROUND: Carotenoids are thought to have anti-cancer properties, but findings from population-based research have been inconsistent. OBJECTIVE: We aimed to conduct a systematic review of the associations between carotenoids and lung cancer. DESIGN: We searched electronic databases for articles published through September 2007. Six randomized clinical trials examining the efficacy of beta-carotene supplements and 25 prospective observational studies assessing the associations between carotenoids and lung cancer were analyzed by using random-effects meta-analysis. RESULTS: The pooled relative risk (RR) for the studies comparing beta-carotene supplements with placebo was 1.10 (95% confidence limits: 0.89, 1.36; P = 0.39). Among the observational studies that adjusted for smoking, the pooled RRs comparing highest and lowest categories of total carotenoid intake and of total carotenoid serum concentrations were 0.79 (0.71, 0.87; P < 0.001) and 0.70 (0.44, 1.11; P = 0.14), respectively. For beta-carotene, highest compared with lowest pooled RRs were 0.92 (0.83, 1.01; P = 0.09) for dietary intake and 0.84 (0.66, 1.07; P = 0.15) for serum concentrations. For other carotenoids, the RRs comparing highest and lowest categories of intake ranged from 0.80 for beta-cryptoxanthin to 0.89 for alpha-carotene and lutein-zeaxanthin; for serum concentrations, the RRs ranged from 0.71 for lycopene to 0.95 for lutein-zeaxanthin. CONCLUSIONS: beta-Carotene supplementation is not associated with a decrease in the risk of developing lung cancer. Findings from prospective cohort studies suggest inverse associations between carotenoids and lung cancer; however, the decreases in risk are generally small and not statistically significant. These inverse associations may be the result of carotenoid measurements' function as a marker of a healthier lifestyle (higher fruit and vegetable consumption) or of residual confounding by smoking.

Arsenic in drinking water and lung cancer: a systematic review.

Exposure to inorganic arsenic via drinking water is a growing public health concern. We conducted a systematic review of the literature examining the association between arsenic in drinking water and the risk of lung cancer in humans. Towards this aim, we searched electronic databases for articles published through April 2006. Nine ecological studies, two case-control studies, and six cohort studies were identified. The majority of the studies were conducted in areas of high arsenic exposure (100 microg/L) such as southwestern Taiwan, the Niigata Prefecture, Japan, and Northern Chile. Most of the studies reported markedly higher risks of lung cancer mortality or incidence in high arsenic areas compared to the general population or a low arsenic exposed reference group. The quality assessment showed that, among the studies identified, only four assessed arsenic exposure at the individual level. Further, only one of the ecological studies presented results adjusted for potential confounders other than age; of the cohort and case-control studies, only one-half adjusted for cigarette smoking status in the analysis. Despite these methodologic limitations, the consistent observation of strong, statistically significant associations from different study designs carried out in different regions provide support for a causal association between ingesting drinking water with high concentrations of arsenic and lung cancer. The lung cancer risk at lower exposure concentrations remains uncertain.

Efficacy and safety of intramuscular aripiprazole in patients with acute agitation: a randomized, double-blind, placebo-controlled trial.

OBJECTIVE: This multicenter, randomized, double-blind, placebo-controlled study evaluated the efficacy and safety of intramuscular (IM) aripiprazole in patients with acute agitation with a DSM-IV diagnosis of schizophrenia, schizoaffective disorder, or schizo-phreniform disorder. METHOD: Patients were randomly assigned to IM aripiprazole 1 mg, 5.25 mg, 9.75 mg, or 15 mg; IM haloperidol 7.5 mg; or placebo and observed for 24 hours. The primary efficacy measure was mean change in the Positive and Negative Syndrome Scale-Excited Component (PEC) score from baseline to 2 hours after initial dosing. Secondary measures included the Agitation-Calmness Evaluation Scale (ACES) score. The study was carried out at 50 centers worldwide between April 2002 and January 2003. RESULTS: A total of 357 patients were randomly assigned to treatment. Intramuscular aripiprazole 5.25 mg, 9.75 mg, and 15 mg and IM haloperidol 7.5 mg demonstrated significantly greater reduction in the primary efficacy measure versus placebo. These changes were statistically significant as early as 45 minutes for the IM aripiprazole 9.75-mg group, with a trend toward significance (p = .051) at 30 minutes. Intramuscular haloperidol 7.5 mg first showed a significant reduction in PEC score versus placebo at 105 minutes. At 30 minutes, significantly more patients responded (defined as a greater than or equal to 40% reduction in PEC score) to IM aripiprazole 9.75 mg versus placebo (27% vs. 13%, p = .05). Intramuscular aripiprazole 9.75 mg significantly improved agitation, without oversedation, as measured by change in ACES score from baseline to 2 hours versus placebo (p = .003). No patient discontinued the study because of treatment-emergent adverse events. Extrapyramidal symptoms occurred most frequently in the IM haloperidol group. The most common adverse event in IM aripiprazole recipients was headache. CONCLUSION: Intramuscular aripiprazole 9.75 mg is a rapidly effective and well-tolerated alternative to IM haloperidol for the control of agitation, without oversedation, in patients with schizophrenia, schizo-affective disorder, or schizophreniform disorder. CLINICAL TRIALS REGISTRATION: ClinicalTrials.gov identifier NCT00036127.

Adulthood consumption of preserved and nonpreserved vegetables and the risk of nasopharyngeal carcinoma: a systematic review.

The incidence rates of nasopharyngeal carcinoma (NPC) are dramatically higher in certain regions of Asia compared to the rest of the world. Few risk factors for NPC are known; however, in contrast to the hypothesized health benefits of nonpreserved vegetables, it is thought that preserved vegetable intake may play a role in contributing to the higher incidence of NPC in high-risk regions. Therefore, the purpose of this study was to systematically review the epidemiologic evidence on the associations between adulthood intake of preserved and nonpreserved vegetables and NPC risk. A search of the epidemiological literature from 1966 to 2004 was performed using several bibliographic databases, including PubMed and the Chinese Biomedical Literature Database System. There were no language restrictions. Meta-analysis was conducted to obtain pooled odds ratios (ORs) for the highest-versus-lowest categories of preserved and nonpreserved vegetable intake. A total of 16 case-control studies were identified in the search. Results showed that highest-versus-lowest preserved vegetable intake was associated with a 2-fold increase in the risk of NPC (Random Effects Odds Ratio (RE OR) 2.04; 95% Confidence Limits (CL) 1.43, 2.92). Conversely, high nonpreserved vegetable intake was associated with 36% decrease in the risk of NPC (RE OR 0.64; 95% CL 0.48, 0.85). Findings for both preserved and nonpreserved vegetables were consistent across vegetable type and by country of study. Further research in high-risk areas to gain insight into the risk associated with preserved vegetables and protection associated with nonpreserved vegetables may advance understanding of NPC and yield clues for prevention.

Encouraging Vietnamese-American women to obtain Pap tests through lay health worker outreach and media education.

BACKGROUND: Five times more Vietnamese-American women develop cervical cancer than white women. Few studies have examined whether community-based participatory research can effectively address Asian immigrants' health problems. This article reports the preliminary evaluation of 1 such project. METHODS: A coalition of 11 organizations in Santa Clara County, California worked with university researchers to design and simultaneously implement a media education (ME) campaign and a lay health worker outreach (LHWO) program to increase Vietnamese-American women's cervical cancer awareness, knowledge, and screening. Two agencies each recruited 10 lay health workers (LHWs), who, in turn, each recruited 20 women who were then randomized into 2 groups: 10 to LHWO+ME (n = 200) and 10 to ME alone (n = 200). LHWs organized meetings with women to increase their knowledge and to motivate them to obtain Pap tests. Participants completed pre- and post-intervention questionnaires. RESULTS: At post-intervention, significantly more LHWO+ME women understood that human papillomavirus and smoking cause cervical cancer. The number of women who had obtained a Pap test increased significantly among women in both LHWO+ME and ME groups, but substantially more in the LHWO+ME group. Significantly more LHWO+ME women said they intended to have a Pap test. CONCLUSIONS: Media education campaigns can increase Vietnamese women's awareness of the importance of Pap tests, but lay health workers are more effective at encouraging women to actually obtain the tests. Lay health workers are effective because they use their cultural knowledge and social networks to create change. Researchers, community members, and community-based organizations can share expert knowledge and skills, and build one another's capacities.

Parathyroid hormone-induced retraction of MC3T3-E1 osteoblastic cells is attenuated by the calpain inhibitor N-Ac-Leu-Leu-norleucinal.

Parathyroid hormone (PTH) binding to its osteoblastic receptors stimulates cytoplasmic retraction within minutes. We hypothesized that the calpains (calcium-activated papain-like enzymes) contribute to PTH-induced osteoblastic retraction by catalyzing regulatory hydrolysis of cytoskeletal structural proteins or enzymes important in cytokinesis. N-Ac-Leu-Leu-norleucinal (ALLN), a reversible calpain inhibitor, was tested for its ability to inhibit PTH-induced retraction in murine MC3T3-E1 osteoblastic cells. ALLN inhibited PTH-induced retraction for 30 minutes in cells cultured on polystyrene cultureware or gelatin-coated glass cover slips, supporting the hypothesis that PTH-induced activation of the calpains contributes to short-term changes in MC3T3-E1 cell shape. Inhibition of PTH-induced retraction occurred on two substrata, suggesting that interactions between the extracellular matrix and cell surface proteins are not the sole determinants of morphology. Intracellular events, such as hydrolysis of focal adherens junction proteins on the cytoplasmic face of the plasma membrane, may contribute to PTH-induced retraction.

PTH-mediated osteoblast retraction: possible participation of the calpain pathway.

Parathyroid hormone (PTH)-induced osteoblast retraction may play a pivotal role a role in bone resorption by providing osteoclasts direct access to mineralized bone surface. We have been working on the hypothesis that the calpains participate in this retractile response through a calcium-dependent process. We have first demonstrated the presence of calpain activities in MC3T3-E1 osteoblastic cells and that these activities can be stimulated by PTH. Second, we have demonstrated that the PTH-induced osteoblast retraction is dramatically attenuated by two different cysteine protease inhibitors. Finally, initial immunofluorescent cytochemical studies suggest that this PTH-induced osteoblastic retraction is mediated through a calpain-dependent, proteolytic modification of the cytoskeletal organization.

PTH and PTH-rP elicit dissimilar retractile responses in murine MC3T3-E1 osteoblasts.

Parathyroid hormone (PTH) and PTH-related peptide (PTH-rP) bind to a common receptor and initiate second-messenger cascades that stimulate bone turnover and hypercalcemia. However, PTH is more potent than PTH-rP in inducing bone resorption and coupled bone metabolism in intact tissue, suggesting that these proteins elicit dissimilar postreceptor responses. We compared the effects of PTH and PTH-rP on osteoblastic retraction, an early event that must occur before the osteoclast can achieve access to the underlying bone mineral and begin resorption. MC3T3-E1 mouse osteoblasts were incubated in vehicle or 4.8 nM PTH or PTH-rP with or without 1 mM dibutyryl cAMP (Bt2cAMP). Morphologic changes were observed from 0 to 120 min. PTH caused marked retraction within minutes, which was not enhanced by Bt2cAMP. PTH-rP or Bt2cAMP induced slower, more modest retraction than PTH. The combined effect of PTH-rP plus Bt2cAMP was greater than that of PTH-rP, but less than that of PTH. PTH-rP and PTH had similar effects on cAMP generation. Thus, compared to PTH, PTH-rP induces less osteoblastic retractile response, exposing less bone surface to osteoclastic resorption. This may account for its lower hypercalcemic potency in vivo and contribute to its relative inability to stimulate coupled bone resorption and formation.

Identification of calcium-activated neutral protease activity and regulation by parathyroid hormone in mouse osteoblastic cells.

Calcium-activated neutral protease activity was detected in mouse MC3T3-E1 cell extracts. Inclusion of the cysteine protease inhibitor, E64c, reduced the activity, while pretreatment of intact cells with 10 nM parathyroid hormone for 90 minutes increased it. The presence of calpains in solubilized cells was confirmed by Western blotting using an antibody specific for the 80 K catalytic subunit. These results, combined with the observation that preincubation with a membrane-permeable cysteine protease inhibitor ablates 50% of the PTH-induced osteoblastic retraction, suggest that calpain-catalyzed hydrolysis of regulatory enzymes or structural proteins plays a role in mediating its short-term effects in bone.