Controlling systemic corruption through group size and salary dispersion of public servants

We investigate an agent-based model for the emergence of corruption in public contracts. There are two types of agents: business people and public servants. Both business people and public servants can adopt two strategies: corrupt or honest behavior. Interactions between business people and public servants take place through defined payoff rules. Either type of agent can switch between corrupt or honest strategies by comparing their payoffs after interacting. We measure the level of corruption in the system by the fractions of corrupt and honest agents for asymptotic times. We study the effects of the group size of the interacting agents, the dispersion with respect to the average salary of the public servants, and a parameter representing the institutional control of corruption. We characterize the fractions of honest and corrupt agents as functions of these variables. We construct phase diagrams for the level of corruption in the system in terms of these variables, where three collective states can be distinguished: i) a phase where corruption dominates; ii) a phase where corruption remains in less than 50% of the agents; and iii) a phase where corruption disappears. Our results indicate that a combination of large group sizes of interacting servants and business people and small dispersion of the salaries of public servants, contributes to the decrease of systemic corruption in public contracts.

Rhabdomyosarcoma in low- and middle-income countries: A report from the Asociacion de Hemato-oncología Pediatrica de Centro América (AHOPCA)

This report describes the results of an observational study dedicated to rhabdomyosarcoma developed by the Asociación de Hemato-oncología Pediatrica de Centro América (AHOPCA) between 2001 and 2018. Overall, 337 previously untreated patients < 18 years old were included in the analysis; 58% had unresected disease, and 19% were metastatic at diagnosis. With a median follow-up of 6.6 years, five-year event-free and overall survival rates were 30% and 33%, respectively. Local progression/relapse was the main cause of treatment failure.

Frequency of Pathogenic Germline Variants in Cancer-Susceptibility Genes in Patients With Osteosarcoma

Importance

Osteosarcoma, the most common malignant bone tumor in children and adolescents, occurs in a high number of cancer predisposition syndromes that are defined by highly penetrant germline mutations. The germline genetic susceptibility to osteosarcoma outside of familial cancer syndromes remains unclear.

Objective

To investigate the germline genetic architecture of 1244 patients with osteosarcoma.

Design, Setting, and Participants

Whole-exome sequencing (n = 1104) or targeted sequencing (n = 140) of the DNA of 1244 patients with osteosarcoma from 10 participating international centers or studies was conducted from April 21, 2014, to September 1, 2017. The results were compared with the DNA of 1062 individuals without cancer assembled internally from 4 participating studies who underwent comparable whole-exome sequencing and 27 173 individuals of non-Finnish European ancestry who were identified through the Exome Aggregation Consortium (ExAC) database. In the analysis, 238 high-interest cancer-susceptibility genes were assessed followed by testing of the mutational burden across 736 additional candidate genes. Principal component analyses were used to identify 732 European patients with osteosarcoma and 994 European individuals without cancer, with outliers removed for patient-control group comparisons. Patients were subsequently compared with individuals in the ExAC group. All data were analyzed from June 1, 2017, to July 1, 2019.

Main Outcomes and Measures

The frequency of rare pathogenic or likely pathogenic genetic variants.

Results

Among 1244 patients with osteosarcoma (mean [SD] age at diagnosis, 16 [8.9] years [range, 2-80 years]; 684 patients [55.0%] were male), an analysis restricted to individuals with European ancestry indicated a significantly higher pathogenic or likely pathogenic variant burden in 238 high-interest cancer-susceptibility genes among patients with osteosarcoma compared with the control group (732 vs 994, respectively; P = 1.3 × 10-18). A pathogenic or likely pathogenic cancer-susceptibility gene variant was identified in 281 of 1004 patients with osteosarcoma (28.0%), of which nearly three-quarters had a variant that mapped to an autosomal-dominant gene or a known osteosarcoma-associated cancer predisposition syndrome gene. The frequency of a pathogenic or likely pathogenic cancer-susceptibility gene variant was 128 of 1062 individuals (12.1%) in the control group and 2527 of 27 173 individuals (9.3%) in the ExAC group. A higher than expected frequency of pathogenic or likely pathogenic variants was observed in genes not previously linked to osteosarcoma (eg, CDKN2A, MEN1, VHL, POT1, APC, MSH2, and ATRX) and in the Li-Fraumeni syndrome-associated gene, TP53.

Conclusions and Relevance

In this study, approximately one-fourth of patients with osteosarcoma unselected for family history had a highly penetrant germline mutation requiring additional follow-up analysis and possible genetic counseling with cascade testing.

Treatment challenges and support needs of underserved Hispanic patients diagnosed with lung cancer and head-and-neck cancer

Purpose: We explored the treatment challenges and support needs that Hispanic underserved lung cancer and head-and-neck cancer patients face while undergoing cancer treatment.Design: Qualitative design - ethnography.Sample: Using a sample of 29 participants, we conducted semi-structured interviews with nine lung cancer and head-and-neck cancer survivors and seven health care providers and focus group interviews with six caregivers and seven patient navigators.Method: Relevant themes were extracted with Ethnographic content analysis.Findings: Participants reported treatment challenges and support needs in four areas: medical, financial, socio-cultural, and mental health. Health care providers and navigators primarily identified medical and financial challenges that impact treatment adherence, while patients and caregivers expressed the need for support for mental health problems (i.e., depression, anxiety).Implications for psychosocial providers: Understanding the experiences of underserved Hispanic cancer survivors can aid in creating psychosocial interventions that successfully target treatment-related challenges and provide them with the support they need.

Establishing Cancer Treatment Programs in Resource-Limited Settings: Lessons Learned From Guatemala, Rwanda, and Vietnam

Purpose

The global burden of cancer is slated to reach 21.4 million new cases in 2030 alone, and the majority of those cases occur in under-resourced settings. Formidable changes to health care delivery systems must occur to meet this demand. Although significant policy advances have been made and documented at the international level, less is known about the efforts to create national systems to combat cancer in such settings.

Methods

With case reports and data from authors who are clinicians and policymakers in three financially constrained countries in different regions of the world—Guatemala, Rwanda, and Vietnam, we examined cancer care programs to identify principles that lead to robust care delivery platforms as well as challenges faced in each setting.

Results

The findings demonstrate that successful programs derive from equitably constructed and durable interventions focused on advancement of local clinical capacity and the prioritization of geographic and financial accessibility. In addition, a committed local response to the increasing cancer burden facilitates engagement of partners who become vital catalysts for launching treatment cascades. Also, clinical education in each setting was buttressed by international expertise, which aided both professional development and retention of staff.

Conclusion

All three countries demonstrate that excellent cancer care can and should be provided to all, including those who are impoverished or marginalized, without acceptance of a double standard. In this article, we call on governments and program leaders to report on successes and challenges in their own settings to allow for informed progression toward the 2025 global policy goals.

An Adiponectin Receptor Agonist Reduces Type 2 Diabetic Periodontitis

Periodontitis is twice as prevalent in diabetics as in nondiabetics, and type 2 diabetes (T2D)-associated periodontitis is severe in many cases due to the altered and aberrant functions of bone cells in hyperglycemic conditions. Therefore, developing an effective method to halt the disease process, as well as restore and regenerate lost alveolar bone to reserve the natural teeth in diabetics, is critically important. In the current study, we applied a newly discovered adiponectin receptor agonist AdipoRon (APR) in experimental periodontitis in diabetic animal models and demonstrated the underlying molecular mechanisms. We found that when APR systemically quenched the blood sugar level in diet-induced obesity (DIO) diabetic mice, it reduced osteoclast numbers and alveolar bone loss significantly due to APR's inhibition on osteoclast differentiation shown in our in vitro studies. APR also decreased the production of proinflammatory molecules CC chemokine ligand 2 and interleukin 6 in diseased gingival tissues. On the other hand, APR promoted alveolar bone regeneration through enhancing osteogenic differentiation and decreasing stromal cell-derived factor 1 in the bone marrow that facilitates stem cell migration. Same results were achieved by APR treatment of periodontitis induced in adiponectin (APN) knockout mice, indicating the ability of APR to activate the endogenous APN receptors to exert osteoanabolic effects. In summary, our study supports the notion that APR could be used as an effective multipronged approach to target T2D-associated periodontitis.

What are patient navigators doing, for whom, and where? A national survey evaluating the types of services provided by patient navigators

OBJECTIVE

A nationwide cross-sectional study was conducted to assess patient navigator, patient population, and work setting characteristics associated with performance of various patient navigation (PN) tasks.

METHODS

Using respondent-driven sampling, 819 navigators completed a survey assessing frequency of providing 83 PN services, along with information about themselves, populations they serve, and setting in which they worked. Analyses of variance and Pearson correlations were conducted to determine differences and associations in frequency of PN services provided by various patient, navigator, and work setting characteristics.

RESULTS

Nurse navigators and navigators with lower education provide basic navigation; social workers typically made arrangements and referrals; and individuals with higher education, social workers, and nurses provide treatment support and clinical trials/peer support. Treatment support and clinical trials/peer support are provided to individuals with private insurance. Basic navigation, arrangements and referrals, and care coordination are provided to individuals with Medicaid or no insurance.

CONCLUSION

Providing basic navigation is a core competency for patient navigators. There may be two different specialties of PN, one which seeks to reduce health disparities and a second which focuses on treatment and emotional support.

PRACTICE IMPLICATIONS

The selection and training of patient navigators should reflect the specialization required for a position.

Improvement in treatment abandonment in pediatric patients with cancer in Guatemala

BACKGROUND

Treatment refusal and abandonment are major causes of treatment failure for children with cancer in low- and middle-income countries (LMICs), like Guatemala. This study identified risk factors for and described the intervention that decreased abandonment.

METHODS

This was a retrospective study of Guatemalan children (0-18 years) with cancer treated at the Unidad Nacional de Oncología Pediátrica (UNOP), 2001-2008, using the Pediatric Oncology Network Database. Treatment refusal was a failure to begin treatment and treatment abandonment was a lapse of 4 weeks or longer in treatment. The impact of medicina integral, a multidisciplinary psychosocial intervention team at UNOP was evaluated. Cox proportional hazards analysis identified the effect of demographic and clinical factors on abandonment. Kaplan-Meier analysis estimated the survival.

RESULTS

Of 1,789 patients, 21% refused or abandoned treatment. Abandonment decreased from 27% in 2001 to 7% in 2008 following the implementation of medicina integral. Factors associated with increased risk of refusal and abandonment: greater distance to the centre (P < 0.001), younger age (P = 0.017) and earlier year of diagnosis (P < 0.001). Indigenous race/ethnicity (P = 0.002) was associated with increased risk of abandonment alone. Abandonment correlated with decreased overall survival: 0.57 ± 0.02 (survival ± standard error) for those who completed therapy versus 0.06 ± 0.02 for those who abandoned treatment (P < 0.001) at 8.3 years.

CONCLUSION

This study identified distance, age, year of diagnosis and indigenous race/ethnicity as risk factors for abandonment. A multidisciplinary intervention reduced abandonment and can be replicated in other LMICs.

Supporting Peer Learning Networks for Case-Based Learning in Public Health: Experience of the Rocky Mountain Public Health Training Center With the ECHO Training Model

Extension for Community Healthcare Outcomes (ECHO) is a model for professional training and support now being used widely in clinical health care. ECHO provides training for health care professionals in their own communities by creating peer learning groups connected by live bidirectional video communications. Topic experts lead the sessions, but most of the learning occurs through case presentations and consultations. Although similar to telemedicine, ECHO differs in that the responsibility for patient care remains with the primary care learners. The Rocky Mountain Public Health Training Center—which supports training for the public health workforce in the six-state region of Colorado, Utah, Wyoming, Montana, and North and South Dakota—has adapted the ECHO health care model for public health training, using the ECHO learning principles of creating and supporting peer learning networks connected by live bidirectional video, and employing a case-based learning approach. The public health ECHO trainings are facilitated by subject matter experts, focus on real-life public health challenges, and use programs or scenarios within communities as “cases.” This article looks at early success in using the ECHO model for public health training on topics such as local public health agency quality improvement, patient navigation, food safety, tobacco control, obesity prevention, tuberculosis management, and HIV prevention. The Rocky Mountain Public Health Training Center continues to refine its implementation of the ECHO learning model across a wide range of public health and population health topics and shows great promise as a framework for regional public health training.

Potassium Channel-blockers as Therapeutic Agents to Interfere with Bone Resorption of Periodontal Disease

Inflammatory lesions of periodontal disease contain all the cellular components, including abundant activated/memory T- and B-cells, necessary to control immunological interactive networks and to accelerate bone resorption by RANKL-dependent and -independent mechanisms. Blockade of RANKL function has been shown to ameliorate periodontal bone resorption and other osteopenic disorders without affecting inflammation. Development of therapies aimed at decreasing the expression of RANKL and pro-inflammatory cytokines by T-cells constitutes a promising strategy to ameliorate not only bone resorption, but also inflammation. Several reports have demonstrated that the potassium channels Kv1.3 and IKCa1, through the use of selective blockers, play important roles in T-cell-mediated events, including T-cell proliferation and the production of pro-inflammatory cytokines. More recently, a potassium channel-blocker for Kv1.3 has been shown to down-regulate bone resorption by decreasing the ratio of RANKL-to-OPG expression by memory-activated T-cells. In this article, we first summarize the mechanisms by which chronically activated/memory T-cells, in concert with B-cells and macrophages, trigger inflammatory bone resorption. Then, we describe the main structural and functional characteristics of potassium channels Kv1.3 and IKCa1 in some of the cells implicated in periodontal disease progression. Finally, this review elucidates some recent advances in the use of potassium channel-blockers of Kv1.3 and IKCa1 to ameliorate the clinical signs or side-effects of several immunological disorders and to decrease inflammatory bone resorption in periodontal disease. ABBREVIATIONS: AICD, activation-induced cell death; APC, antigen-presenting cells; B(K), large conductance; CRAC, calcium release-activated calcium channels; DC, dendritic cell; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; IFN-γ, interferon-γ; IP3, inositol (1,4,5)-triphosphate; (K)ir, inward rectifier; JNK, c-Jun N-terminal kinase; I(K), intermediate conductance; LPS, lipopolysaccharide; L, ligand; MCSF, macrophage colony-stimulating factor; MHC, major histocompatibility complex; NFAT, nuclear factor of activated T-cells; RANK, receptor activator of nuclear factor-κB; TCM, central memory T-cells; TEM, effector memory T-cells; TNF, tumor necrosis factor; TRAIL, TNF-related apoptosis-inducing ligand; OPG, osteoprotegerin; Omp29, 29-kDa outer membrane protein; PKC, protein kinase C; PLC, phospholipase C; RT-PCR, reverse-transcriptase polymerase chain-reaction; S(K), small conductance; TCR, T-cell receptor; and (K)v, voltage-gated.

Improvement of Abandonment of Therapy in Pediatric Patients with Cancer in Guatemala

Abstract 59

Background:

Abandonment of therapy is a major cause of therapeutic failure in the treatment of childhood cancer in Low and Middle Income Countries (LMIC). This study examines factors associated with increased risk of therapy abandonment in Guatemalan children with cancer and the rates of therapy abandonment before and after implementation of a multidisciplinary psychosocial intervention program.

Methods:

A retrospective population-based study was performed to identify risk factors for abandonment of therapy in Guatemalan children, ages 0-18, with cancer who were seen at UNOP from 2001-2008. Patient data was collected from the Pediatric Oncology Networked Database (POND4Kids). Abandonment was defined as a lapse of 4 weeks in planned treatment or failure to begin treatment for a potentially curable cancer. Cox proportional hazards analysis identified the effect of age, sex, year of diagnosis, distance travelled to UNOP, ethnicity, and principal diagnosis on abandonment of therapy. Kaplan Meier analysis was used to evaluate survival.

Results:

A retrospective analysis of 1,789 charts was performed and 367 patients abandoned therapy. The rate of abandonment decreased from 27% in 2001 to 7% in 2008 following a multidisciplinary psychosocial intervention program. Greater distance to UNOP (p = 0.00), younger age (p = 0.02) and earlier year of diagnosis (p = 0.00) were associated with increased risk of abandonment. Abandonment of therapy correlated with decreased survival. The cumulative survival at 8.3 years was 0.57 ± 0.02 (survival±SE) for those who completed therapy vs 0.06 ± 0.02 for those who abandoned and refused therapy (p=0.000) in an abandonment sensitive analysis.

Conclusion:

This study identified distance, age, and year of diagnosis as risk factors for abandonment of therapy for pediatric cancer in Guatemala. This study highlights risk factors for abandonment of therapy and the role of targeted interventions in altering rates of abandonment that could be replicated in other LMIC countries.

AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST:

No COIs from the authors.

An Analysis of Treatment Failure in Wilms Tumor (WT): A Report from the Central American Association of Pediatric Hematology/Oncology (AHOPCA)

Abstract 57

Background:

Patients with WT in AHOPCA present late with large abdominal masses, in poor clinical condition. This analysis focuses on treatment failure.

Methods:

Between 2012 and 2015, 182 evaluable patients were diagnosed with unilateral WT. Patients were staged with abdominal ultrasound/computed tomography and thorax radiograph/CT. Therapy was adapted from National Wilms Tumor Study-5 except for patients with large abdominal masses and/or severe malnutrition who received preoperative doxorubicin, vincristine, actinomycin-D for 4 to 6 weeks. Treatment failure was defined as abandonment of therapy, recurrent/progressive disease (PD), and death: early (< 2 weeks from diagnosis) or toxic (> 2 weeks after diagnosis).

Results:

49% were male; 23% were <2 years (median age 3.5y). Stage distribution: I, 8; II, 21; III, 116; IV, 37 cases. For 123/181 (68%) preoperative therapy was warranted (volume 579cm3). Treatment failures were: recurrence/PD 28; abandonment 19; early death 3, and toxic death 2. 2/29 (7%) patients with stage I/II suffered recurrence/PD, 13/116 (11%) stage III, and 13/37 (35%) stage IV. Most failures were metastatic (68%). Abandonment-sensitive 3-years EFS was 68%±0.04% (SE) for the all stages, 77%±0.043% abandonment-censored, and abandonment-sensitive OS was 71%±0.05%.

Conclusion:

Multicenter protocol-driven therapy tailored to fit regional needs is feasible in patients with WT. Abandonment remains a challenge as do early and toxic deaths due to advanced disease presentations in fragile children. Compared to previous eras 2000-2004 (3-year EFS 50%±4.3% and 2005-2011 (3-year EFS 59%±3.1%) survivals continue to improve. This improvement reflects the engagement of the whole multidisciplinary team including surgery, radiation oncology, and pathology.

AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST:

No COIs from the authors.

Satisfaction with cancer care among underserved racial-ethnic minorities and lower-income patients receiving patient navigation

BACKGROUND

Patient navigation is a barrier-focused program of care coordination designed to achieve timely and high-quality cancer-related care for medically underserved racial-ethnic minorities and the poor. However, to the authors' knowledge, few studies to date have examined the relationship between satisfaction with navigators and cancer-related care.

METHODS

The authors included data from 1345 patients with abnormal cancer screening tests or a definitive cancer diagnosis who participated in the Patient Navigation Research Program to test the efficacy of patient navigation. Participants completed demographic questionnaires and measures of patient satisfaction with cancer-related care (PSCC) and patient satisfaction with interpersonal relationship with navigator (PSN-I). The authors obtained descriptive statistics to characterize the sample and conducted regression analyses to assess the degree of association between PSN-I and PSCC, controlling for demographic and clinical factors. Analyses of variance were conducted to examine group differences controlling for statistically significant covariates.

RESULTS

Statistically significant relationships were found between the PSCC and PSN-I for patients with abnormal cancer screening tests (1040 patients; correlation coefficient (r), 0.4 [P<.001]) and those with a definitive cancer diagnosis (305 patients; correlation coefficient, 0.4 [P<.001]). The regression analysis indicated that having an abnormal colorectal cancer screening test in the abnormal screening test group and increased age and minority race-ethnicity status in the cancer diagnosis group were associated with a higher satisfaction with cancer care (P<.01).

CONCLUSIONS

Satisfaction with navigators appears to be significantly associated with satisfaction with cancer-related care. Information regarding the patient-navigator relationship should be integrated into patient navigation programs to maximize the likelihood of reducing caner disparities and mortality for medically underserved racial-ethnic minorities and the poor.

Community-based navigators for tobacco cessation treatment: a proof-of-concept pilot study among low-income smokers

BACKGROUND

A majority of continuing smokers in the United States are socioeconomically disadvantaged (SED) adults, who are less likely than others to achieve and maintain abstinence despite comparable quit-attempt rates. A national research initiative seeks effective new strategies for increasing successful smoking cessation outcomes among SED populations. There is evidence that chronic and acute stressors may interfere with SED smokers who try to quit on their own. Patient navigators have been effectively used to improve adherence to chronic disease treatment. We designed and have pilot-tested an innovative, non-clinical community-based intervention--smoking cessation treatment navigators--to determine feasibility (acceptance, adherence, and uncontrolled results) for evaluation by randomized controlled trial (RCT).

METHODS

The intervention was developed for smokers among parents and other household members of inner city pre-school for low-income children. Smoking cessation treatment navigators were trained and deployed to help participants choose and adhere to evidence-based cessation treatment (EBCT). Navigators provided empathy, resource-linking, problem-solving, and motivational reinforcement. Measures included rates of study follow-up completion, EBCT utilization, navigation participation, perceived intervention quality, 7-day point abstinence and longest abstinence at three months. Both complete-case and intent-to-treat analyses were performed.

RESULTS

Eighty-five percent of study participants (n = 40) completed final data collection. More than half (53%) enrolled in a telephone quitline and nearly three-fourths (71%) initiated nicotine replacement therapy. Participants completed a mean 3.4 navigation sessions (mean 30 min duration) and gave the intervention very high quality and satisfaction ratings. Self-reported abstinence was comparable to rates for evidence-based cessation strategies (21% among study completers, 18% using intent-to-treat analysis; median 21 days abstinent among relapsers).

CONCLUSIONS

The pilot results suggest that smoking cessation treatment navigators are feasible to study in community settings and are well-accepted for increasing use of EBCT among low-income smokers. Randomized controlled trial for efficacy is warranted.

Outcome of children treated for relapsed acute myeloid leukemia in Central America

BACKGROUND

Relapsed childhood acute myeloid leukemia (AML) outcomes have not been documented in resource-limited settings. We examined survival after relapse for children with AML (non-APML) and acute promyelocytic leukemia (APML) in Central America.

PROCEDURE

We retrospectively evaluated outcomes of children with first relapse of AML (non-APML) and APML in Guatemala, Honduras, or El Salvador diagnosed between 1997 and 2011. Predictors of subsequent event-free survival (EFS) and overall survival (OS) were examined.

RESULTS

We identified 140 children with relapsed AML (non-APML), and 24 with relapsed APML. Two-year subsequent EFS and OS (±SE) were 7.0 ± 2.5% and 9.1 ± 2.8%, respectively. Worse outcomes were associated with Hispanic or Indigenous heritage, white blood cell count at diagnosis ≥50 × 10(9) /L, and time to relapse <18 months. For those with relapsed APML, subsequent 2-year EFS and OS were 36.7 ± 10.8% and 43.4 ± 12.1%, although few patients survived beyond 3 years. 15.2% of all patients were managed solely with palliative intent following first relapse.

CONCLUSIONS

Children with relapsed AML in Central America rarely survive, so palliative strategies should be considered following relapse in this population. However, children with late relapse or with APML may have a prolonged period of remission with second treatment, and consideration of re-treatment may be appropriate.

Increased incidence and disparity of diagnosis of retinoblastoma patients in Guatemala

Analysis of 327 consecutive cases at a pediatric referral hospital of Guatemala reveals that retinoblastoma accounts for 9.4% of all cancers and the estimated incidence is 7.0 cases/million children, higher than the United States or Europe. The number of familial cases is low, and there is a striking disparity in indigenous children due to late diagnosis, advanced disease, rapid progression and elevated mortality. Nine germline mutations in 18 patients were found; two known and five new mutations. Hypermethylation of RB1 was identified in 13% of the tumors. An early diagnosis program could identify cases at an earlier age and improve outcome of retinoblastoma in this diverse population.

Patient navigation improves cancer diagnostic resolution: an individually randomized clinical trial in an underserved population

BACKGROUND

Barriers to timely resolution of abnormal cancer screening tests add to cancer health disparities among low-income, uninsured, and minority populations. We conducted a randomized trial to evaluate the impact of lay patient navigators on time to resolution and completion of follow-up testing among patients with abnormal screening tests in a medically underserved patient population.

METHODS

Denver Health, the safety-net health care system serving Denver, is one of 10 performance sites participating in the Patient Navigation Research Program. Of 993 eligible subjects with abnormal screening tests randomized to navigation and no-navigation (control) arms and analyzed, 628 had abnormal breast screens (66 abnormal clinical breast examinations, 304 BIRADS 0, 200 BIRADS 3, 58 BIRADS 4 or 5) whereas 235 had abnormal colorectal and 130 had abnormal prostate screens.

RESULTS

Time to resolution was significantly shorter in the navigated group (stratified log rank test, P < 0.001). Patient navigation improved diagnostic resolution for patients presenting with mammographic BIRADS 3 (P = 0.0003) and BIRADS 0 (P = 0.09), but not BIRADS 4/5 or abnormal breast examinations. Navigation shortened the time for both colorectal (P = 0.0017) and prostate screening resolution (P = 0.06). Participant demographics included 72% minority, 49% with annual household income less than $10,000, and 36% uninsured.

CONCLUSIONS

Patient navigation positively impacts time to resolution of abnormal screening tests for breast, colorectal, and prostate cancers in a medically underserved population.

IMPACT

By shortening the time to and increasing the proportion of patients with diagnostic resolution patient navigation could reduce disparities in stage at diagnosis and improve cancer outcomes.

Patient navigation for breast and colorectal cancer treatment: a randomized trial

BACKGROUND

There is limited high-quality evidence about the impact of patient navigation (PN) on outcomes for patients with diagnosed cancer.

METHODS

We pooled data from two sites from the national Patient Navigation Research Program. Patients (n = 438) with newly diagnosed breast (n = 353) or colorectal cancer (n = 85) were randomized to PN or usual care. Trained lay navigators met with patients randomized to PN to help them assess treatment barriers and identify resources to overcome barriers. We used intent-to-treat analysis to assess time to completion of primary treatment, psychologic distress (impact of events scale), and satisfaction (patient satisfaction with cancer-related care) within 3 months after initiation of cancer treatment.

RESULTS

The sample was predominantly middle-aged (mean age = 57) and female (90%); 44% were race-ethnic minorities (44%), 46% reported lower education levels, 18% were uninsured, and 9% reported a non-English primary language. The randomized groups were comparable in baseline characteristics. Primary analysis showed no statistically significant group differences in time to completion of primary cancer treatment, satisfaction with cancer-related care, or psychologic distress. Subgroup analysis showed that socially disadvantaged patients (i.e., uninsured, low English proficiency, and non-English primary language) who received PN reported higher satisfaction than those receiving usual care (all P < 0.05). Navigated patients living alone reported greater distress than those receiving usual care.

CONCLUSIONS

Although the primary analysis showed no overall benefit, the subgroup analysis suggests that PN may improve satisfaction with care for certain disadvantaged individuals.

IMPACT

PN for cancer patients may not necessarily reduce treatment time nor distress.

Establishing common cost measures to evaluate the economic value of patient navigation programs

BACKGROUND

Patient navigation is an intervention aimed at reducing barriers to health care for underserved populations as a means to reduce cancer health disparities. Despite the proliferation of patient navigation programs across the United States, information related to the economic impact and sustainability of these programs is lacking.

METHODS

After a review of the relevant literature, the Health Services Research (HSR)-Cost workgroup of the American Cancer Society National Patient Navigator Leadership Summit met to examine cost data relevant to assessing the economic impact of patient navigation and to propose common cost metrics.

RESULTS

Recognizing that resources available for data collection, management, and analysis vary, 5 categories of core and optional cost measures were identified related to patient navigator programs, including program costs, human capital costs, direct medical costs, direct non-medical costs, and indirect costs.

CONCLUSIONS

Information demonstrating economic as well as clinical value is necessary to make decisions about sustainability of patient navigation programs. Adoption of these common cost metrics are recommended to promote understanding of the economic impact of patient navigation and comparability across diverse patient navigation programs.

Treating Pediatric soft tissue sarcomas in a country with limited resources: the experience of the Unidad Nacional de Oncologia Pediatrica in Guatemala

BACKGROUND

About 250-300 children with newly diagnosed cancer are treated each year at the Unidad Nacional de Oncologia Pediatrica in Guatemala City; less than 5% of them have soft tissue sarcomas (STS). The aim of the article was to evaluate whether the therapeutic standards achieved in STS in developed countries could be reproduced in a low-income country.

PATIENTS AND METHODS

We reviewed the clinical data, treatment and outcome of 80 patients, 47 cases of rhabdomyosarcoma (RMS) and 33 of non-rhabdomyosarcoma soft tissue sarcoma (NRSTS), treated between January 2000 and October 2007.

RESULTS

Most of the RMS patients had advanced disease at diagnosis (87% groups III-IV). Their 3-year event-free survival rate (EFS) was 26.4% if abandoning the treatment was considered as an event, or 32.4% if it was censored (14 patients abandoned the treatment), and the 3-year overall survival rate (OS) was 43.5%. Local progression/relapse was the main cause of treatment failure. Among the patients with NRSTS, the EFS at 3 years was 36.4% (when abandoning the treatment was considered as an event) or 43.3% (when it was censored), and the OS was 44.2%. Outcome was satisfactory for synovial sarcoma patients, those with tumors < or =5 cm, and those with localized disease.

CONCLUSIONS

Overall results were unsatisfactory compared to results reported from developed countries. Late diagnosis and the consequently high proportion of cases of advanced disease at diagnosis, the large number of patients failing to complete the treatment, and the poor quality of local control (in RMS) adversely influence outcome.

Pharmacotherapies to manage bone loss-associated diseases: a quest for the perfect benefit-to-risk ratio

In this review, benefits and side-effects of current and emerging therapies to treat and prevent pathological bone loss are described. Bisphosphonates are the antiresorptive compounds most widely used in the treatment of bone-loss associated diseases. They are generally well-tolerated although have recently been associated with osteonecrosis of the jaw and other complications. Therapies modulating estrogen receptor activation are indicated in the prevention and treatment of either breast cancer or osteoporosis in postmenopausal women. Thus, hormone replacement therapy is effective in prevention of osteoporosis, but its long-term use can increase the risk of breast cancer, stroke and embolism. Tamoxifen benefits all stages of breast cancer, but its use may lead to uterine cancer and thromboembolism. Raloxifene is approved in prevention of breast cancer and treatment of postmenopausal osteoporosis, but its use can increase the risk of fatal stroke. Aromatase inhibitors are superior to tamoxifen at advanced stages of disease and as adjuvants, but their use increase fracture incidence. Fulvestrant is as effective as aromatase inhibitors in the treatment of advanced breast cancer and does not cause bone fractures. Another antiresorptive available for the treatment of postmenopausal osteoporosis, Paget's disease and hypercalcemia is calcitonin, which also exhibits analgesic effects. A promising antiresorptive agent currently in clinical trials is denosumab. Aditional therapies for osteoporosis that decrease fracture risk consist of PTH-like anabolic agents and the dual action bone agent strontium ranelate. Antiseptics and antibiotics are used extensively in periodontal disease intervention to target bacterial biofilm, although host-directed therapies are also being developed.

Phenotypic analysis of Dlx5 overexpression in post-natal bone

Dlx5 plays an important role in the embryonic development of mineralized tissues. We hypothesized that Dlx5 also functions in regulating post-natal bone formation in mice. To prove this hypothesis, we infected 5-day-old bone sialoprotein (BSP)/avian retroviral receptor gene (TVA) transgenic mice with replication-competent retroviral vectors expressing wild-type Dlx5 (RCAS-Dlx5WT) and mutated Dlx5 at arginine (R) 31 of its homeodomain (RCAS-Dlx5RH). Immunohistochemistry indicated that RCAS-Dlx5WT increased BSP and osteopontin (OPN) expression, whereas it decreased that of osteocalcin (OC). RCAS-Dlx5RH mediated opposite effects. Semi-quantitative RT-PCR confirmed these results. Ex vivo overexpression of RCAS-Dlx5WT in BSP/TVA calvarial cells promoted, whereas that of RCAS-Dlx5RH inhibited, mineralized nodule formation as compared with that in control cells. Our results suggest that Dlx5 promotes expression of early markers of osteogenic differentiation and increases mineralization post-natally.

Results from two years of field studies to determine Mancozeb based spray programmes with minimal impact on predatory mites in European vine cultivation

Mancozeb is a dithiocarbamate fungicide with contact activity against a wide range of economically important fungal diseases. Its multi-site mode of action means that to date there have been no recorded incidences of resistance developing despite many years of use on high risk diseases. One such disease, Grape downy mildew (Plasmopara viticola) has developed resistance to a wide range of important oomycete specific fungicides following their introduction onto the market. The role of Mancozeb either as a mixing or alternation partner in helping to manage these resistance situations remains critically important. Historical use patterns for mancozeb in tree and vine crops involved many applications of product at high use rates. Although this gave excellent disease control, a negative impact on predatory mites was often reported by researchers. This has lead to the development of mancozeb spray programmes in vines and other crops with a much reduced impact on predatory mites. A range of field studies was conducted over two years in France, Germany, Italy, Portugal and Spain where 2, 3 or 4 applications of mancozeb containing products were made per season at different spray timings. In this paper findings from field studies over two years in five different vine growing regions in Europe indicated that two to four applications of mancozeb at 1.6 kg a.i./ha as part of a spray programme caused minimal impact on naturally occurring populations of predatory mites which in turn was compatible with Integrated Pest Management programmes and the conservation of predatory mites.

Selectivity of the ubiquitin pathway for oxidatively modified proteins: relevance to protein precipitation diseases

There is now consensus that the accumulation of oxidatively modified proteins is cytotoxic and causally related to several age-related diseases, including the amyloid diseases and age-related cataracts. There is also general agreement that proteolytic pathways provide a quality control mechanism to limit accumulation of damaged proteins. Although many researchers assume that the ubiquitin pathway is involved in recognition and proteolytic removal of oxidatively modified proteins, which are produced upon cellular stress, there has been no direct evidence to support this hypothesis. In this work, we used a novel proteolysis-resistant ubiquitin variant to demonstrate that ubiquitin conjugates isolated from oxidatively stressed mammalian cells are enriched 3.3-15-fold for oxidatively modified proteins and that failure to execute ubiquitin-dependent proteolysis renders various cell types more susceptible to oxidative stress-related cytotoxicity. These results were corroborated using several inhibitors of the ubiquitin proteasome pathway, including PS-341, an anticancer drug in clinical use. Taken together the data indicate that the ubiquitin proteolytic pathway recognizes and removes oxidatively modified proteins, and that failure of this system, as occurs upon aging or stress, may be involved in and exacerbate cytotoxicity and age-related syndromes in which accumulation of ubiquitinated and oxidatively modified proteins has an etiologic role.

Role of Gas6/Axl signaling in lens epithelial cell proliferation and survival

Axl is a receptor tyrosine kinase that is activated by Gas6, a growth factor that belongs to the vitamin K-dependent protein family. Although Gas6 binding to Axl has been shown to transmit mitogenic and/or antiapoptotic signals to a variety of cell types, the role of the Axl-Gas6 system in normal and pathological lens biology is not known. We demonstrate for the first time that Axl protein is expressed in normal rat and bovine lens and that its ligand, Gas6, is present in bovine aqueous humor. In addition, we have detected tyrosine-phosphorylated Axl in normal rat and bovine lens epithelial tissues. We further show that human recombinant Gas6 is able to act as a growth factor in cultured human lens epithelial cells by activating Axl and then the AKT signaling pathway. Gas6 mediates a survival and anti-apoptotic response in cultured human lens epithelial cells subjected to serum-starvation (48-72hr), or treated with transforming growth factor beta1 (5 ng ml(-1), 48hr) or tumor necrosis alpha (100 ng ml(-1), 48hr), as demonstrated by increased number of viable cells, and decreased DNA condensation or caspase-3 activity. In contrast, Gas6 is not able to block apoptosis induced by staurosporin (1microM, 5-24hr) in human lens epithelial cells. Taken together, these data suggest that the Gas6/Axl signaling plays an important role in the control of lens epithelial cell growth and survival and hence in the maintenance of lens homeostasis.

Melanocyte stimulating hormone activation of tyrosinase in B16 mouse melanoma cells Evidence for a differential induction of two distinct isoenzymes

Tyrosinase induction in murine malignant melanocytes by alpha MSH is well known, but its molecular basis has not been characterized. Treatment of B16 melanoma cells with theophylline or alpha MSH mediates a larger induction of tyrosine hydroxylase than of dopa oxidase activity in total cell extracts, and in the melanosomal and microsomal fractions. No evidence for the modulation of a tyrosinase effector was found. SDS-PAGE and specific activity stain demonstrated two forms of tyrosinase, with different degrees of induction by theophylline. These results agree with the recent proposal that two tyrosinases, encoded by different genes, are present in murine melanocytes.

Cloning, expression, and mapping of hWW45, a novel human WW domain-containing gene

WW domain-containing proteins are found in all eukaryotes and play an important role in the regulation of a wide variety of cellular functions such as protein degradation, transcription, and RNA splicing. The cloning and characterization of a novel human WW domain-containing gene, hWW45, which encodes a protein of approximately 45 kDa consisting of 2 WW domains and a coiled-coil region is reported here. The murine homologue cDNA, mWW45, displays a different 3'-untranslated region and predicts a protein identity of 93% to hWW45. Northern blot and RT-PCR analysis demonstrated that both mWW45 and hWW45 transcripts are ubiquitously expressed in adult tissues. The mouse embryonic expression is first seen at 7 days post coitum in Northern blot analysis of whole embryos. Chromosomal localization by radiation hybrid mapping revealed that hWW45 is localized at chromosome 14, 10.31cR from the marker D14S269.

Purification and preliminary characterization of a cardiac Kv1.5 repressor element binding factor

We have previously demonstrated that the cell-specific expression of Kv1.5 promoter is regulated by a silencer (Kv1.5 repressor element; KRE) containing a dinucleotide-repetitive element, (GT)19(GA)1(CA) 15(GA)16. Electromobility gel shift assays (EMSAs) of KRE with GH3 nuclear extracts detected a unique DNA-protein complex, which was not detectable in Chinese hamster ovary or COS-7 cells. We further delineated KRE and determined that a 52-bp fragment that contained a (GT)10(GA)1(CA)10 dinucleotide-repetitive element was sufficient for silencer activity. EMSAs using nuclear extracts isolated from the heart and from GH3 cells demonstrated that the 52-bp element formed specific and identical gel shift effects. These complexes were not detectable in EMSA experiments with liver nuclear extracts. Magnetic DNA affinity purification and UV cross-linking experiments identified a 27-kDa KRE binding factor (KBF) in GH3 cell nuclear extracts. Purified KBF reacted specifically with double-stranded KRE, abolishing the formation of multimeric KRE-DNA complexes. Thus, the interaction between KRE and KBF may play an important role in regulating the GH3- and cardiac-specific expression of Kv1.5.

Tyrosinase may protect human melanocytes from the cytotoxic effects of the superoxide anion

Reactive oxygen species (ROS) are potentially cytotoxic and several mechanisms have evolved to protect against their damaging effects. In melanocytes, tyrosinase may have such a rôle by utilising the superoxide anion (O2-) in the production of melanin. In the present study, we have examined the cytotoxic effects of O2- and hydrogen peroxide (H2O2) in human melanocytes both before and following the activation of tyrosinase. Xanthine oxidase (XO, 5-150 mU.ml-1) and glucose oxidase (GO, 0.1-20 mU.ml-1) were used to generate the O2- and H2O2 respectively, and the cytotoxic effects assessed by measuring cell survival using the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium (MTT) assay. 3 h later, dose-related decreases in melanocyte survival were seen. Similar experiments with keratinocytes and fibroblasts showed that these cells were more resistant to the cytotoxic effects of O2- than were the melanocytes. The effect of increasing tyrosinase activity was examined by growing the melanocytes in the presence of an analogue of melanocyte-stimulating hormone (MSH) Nle4DPhe7 alpha-MSH (10(-8) M), for 48 h. This increased tyrosinase activity, melanin content, the ability to trap O2- and the resistance of the melanocytes to the cytotoxic effects of this ROS, but failed to alter their susceptibility to the damaging effects of H2O2.Nle4DPhe7 alpha-MSH had no effect on the resistance of keratinocytes and fibroblasts to either O2- or H2O2. After 3 h, XO, as opposed to GO, also increased the melanin content of human melanocytes; this effect was not accompanied by an increase in tyrosinase activity. The present results suggest that tyrosinase may utilise O2- to produce melanin and that this process may protect melanocytes from the potentially damaging effects of this ROS.

The Asp84Glu variant of the melanocortin 1 receptor (MC1R) is associated with melanoma

Melanocyte stimulating hormone (MSH) plays an important role in determining the cutaneous response to ultraviolet radiation and may also influence melanoma progression. We have previously shown that variants of the melanocortin receptor present on melanocytes, MC1R, are associated with sun sensitivity and red hair in a UK population and therefore now consider the gene as a candidate for melanoma susceptibility. We have compared the frequency of known MC1R variants in the second and seventh transmembrane domains in 43 melanoma cases and 44 controls. MC1R variants were more common in cases than controls (chi 2 = 6.75, 1 d.f.; P = 0.0094) with a relative risk to carriers of variant alleles compared with normal homozygotes of 3.91 (95% c.l.: 1.48-10.35), and a population risk attributable to carriers of 34.6% (95% c.i. 10.7-52.1%). The Asp84Glu variant was only present in melanoma cases and appears to be of particular significance. The contribution of variant MC1R alleles was largely independent of skin type. Variants of the MC1R gene are likely to be causally associated with the development of melanoma.

Activation of tyrosinase reduces the cytotoxic effects of the superoxide anion in B16 mouse melanoma cells

Tyrosinase may protect against oxidative stress by using the superoxide anion (O2-1.) in the production of melanin. We have examined this by comparing its cytotoxic effects in B16/F10 and B16/F10-differential deficient (-DD) mouse melanoma cells that express high and low levels of tyrosinase activity respectively. Xanthine oxidase (XO) was used to generate O2.1 and cytotoxicity assessed by measuring cell survival. XO increased O2.- concentrations and 3 h later dose related decreases in cell survival were seen. F10 cells were more resistant to these cytotoxic effects than the F10-DD cells. [Nle4, DPhe7]MSH increased tyrosinase activity and melanin content, reduced O2.- concentration and increased the resistance of F10 cells to the cytotoxic effects of O2.-. No such effects were seen in F10-DD cells. The effect of [Nle4, DPhe7]MSH on the resistance of the F10 cells was time-dependent and noticeable when tyrosinase activity but not melanin was increased. This suggests that it was the activation of tyrosinase rather than the increase in the melanin that provided the protection against O2.-. In support of this, inhibition of tyrosinase with phenylthiocarbamide reduced the increased resistance induced by [Nle4, DPhe7]MSH. Moreover, although melanin was capable of scavenging O2.- it had little effect at concentrations comparable to those in the activated F10 cells. XO also increased the melanin content of F10 but not F10-DD cells. We conclude that tyrosinase is able to utilise O2.- to produce melanin and this provides pigment cells with a unique anti-oxidant mechanism.

Variants of the melanocyte-stimulating hormone receptor gene are associated with red hair and fair skin in humans

Melanin pigmentation protects the skin from the damaging effects of ultraviolet radiation (UVR). There are two types of melanin, the red phaeomelanin and the black eumelanin, both of which are present in human skin. Eumelanin is photoprotective whereas phaeomelanin, because of its potential to generate free radicals in response to UVR, may contribute to UV-induced skin damage. Individuals with red hair have a predominance of phaeomelain in hair and skin and/or a reduced ability to produce eumelanin, which may explain why they fail to tan and are at risk from UVR. In mammals the relative proportions of phaeomelanin and eumelanin are regulated by melanocyte stimulating hormone (MSH), which acts via its receptor (MC1R), on melanocytes, to increase the synthesis of eumelanin and the product of the agouti locus which antagonises this action. In mice, mutations at either the MC1R gene or agouti affect the pattern of melanogenesis resulting in changes in coat colour. We now report the presence of MC1R gene sequence variants in humans. These were found in over 80% of individuals with red hair and/or fair skin that tans poorly but in fewer than 20% of individuals with brown or black hair and in less than 4% of those who showed a good tanning response. Our findings suggest that in humans, as in other mammals, the MC1R is a control point in the regulation of pigmentation phenotype and, more importantly, that variations in this protein are associated with a poor tanning response.

Melatonin antagonizes alpha-melanocyte-stimulating hormone enhancement of melanogenesis in mouse melanoma cells by blocking the hormone-induced accumulation of the c locus tyrosinase

Melatonin was found to have a small inhibitory effect on tyrosinase activity and a slight stimulatory action on dopachrome tautomerase activity in B16 mouse melanoma cells. These effects were time and dose dependent, with the maximal response being observed after 24-48 h treatment and at concentrations of melatonin higher than the physiologic levels of the circulating hormone. Although these effects on the melanogenic activities were modest, incubation of melanocytes with melatonin prior to the addition of the melanotropin mediated a dramatic inhibition of alpha-melanocyte-stimulating-hormone-(alpha-MSH)-induced melanogenesis. This inhibitory effect was evident at melatonin concentrations as low as 10 nM. Inhibition was nearly total at 0.1 mM melatonin, even at high concentrations of alpha-MSH (1 microM). The inhibitory effect of melatonin on alpha-MSH stimulation of melanogenesis was investigated. Melatonin appeared to act at least at two stages. Pharmacological concentrations of melatonin diminished the number of alpha-MSH receptors to about 75% of the control values without an apparent effect on receptor affinity, as determined by receptor-binding studies using 125I-[N-Leu4-D-Phe7]alpha-MSH as a probe. Physiological concentrations of melatonin also appeared to interfere with the intracellular events coupling increased cAMP levels and induction of the c locus tyrosinase, since it strongly inhibited the theophylline-mediated stimulation of melanogenesis. The inhibition of tyrosinase stimulation was higher in the microsomal than in the melanosomal fractions of cells which were treated with melatonin, then exposed to either alpha-MSH (1 microM) or theophylline (1 mM), suggesting that one of the main effects of melatonin might be inhibition of the induction of tyrosinase de novo synthesis.

Improved tyrosinase activity stains in polyacrylamide electrophoresis gels

Mammalian tyrosinase exists in a variety of subcellular locations and maturation states that result from a complex post-translational processing with possible regulatory implications. So far, SDS-PAGE has proven to be the method of choice for the resolution of tyrosinase isoforms. However, the relatively poor sensitivity of the currently available specific activity stain based on incubation of the gels with L-dopa until the formation of melanin has severely limited the use of electrophoresis in regulation studies. Two alternative staining procedures are presented and discussed. The first one involves the fluorographic detection of radioactive melanin after incubation of the gels in the presence of L-[3-14C]-dopa. A similar method has already been used by others (Tsukamoto et al., 1992, Pigment Cell Res. [Suppl.] 2:84-89), but its performance has not yet been compared to the one of the dopa procedure. The sensitivity of this method can be varied by adjusting the isotopic dilution of the tracer and/or the time of exposure of the gel, but it is at least ten times higher than the one of the colorimetric stain. Moreover, the intensity of the bands is proportional to the initial tyrosinase activity over a wide range. Using this procedure, the activity present in the different subcellular fractions of melanocytes in culture can be easily detected. The second procedure involves the formation of a colored adduct between dopaquinone and MBTH.(ABSTRACT TRUNCATED AT 250 WORDS)

Tyrosinase isoenzymes in mammalian melanocytes. 1. Biochemical characterization of two melanosomal tyrosinases from B16 mouse melanoma

B-16 mouse melanoma melanosomes contain two forms of tyrosinase that can be resolved by SDS/PAGE. These forms interact to different extents with the ion-exchanger DEAE-Sephadex and with hydroxyapatite, and have different affinity for the melanosomal membrane and/or the intraorganular matrix. After partial purification and complete separation of the two tyrosinases, several kinetic parameters were analyzed. The form of lower electrophoretic mobility displayed a higher Km for 3,4-dihydroxy-L-phenylalanine (L-dopa) and L-tyrosine, an absolute requirement for the cofactor L-dopa in its tyrosine hydroxylase activity, and a lower ratio of tyrosine hydroxylation to Dopa oxidation. The form of higher electrophoretic mobility displayed lower values of Km for both substrates and was able to exhibit tyrosine hydroxylase activity after a lag period even in the absence of L-dopa. Both forms were stereospecific for the L isomers and sensitive to the specific tyrosinase inhibitor 2-phenylthiourea. These forms do not appear to result from different degrees of glycosylation, nor from limited proteolysis and are also present in the microsomal fraction of B16 mouse melanoma. They might correspond to different gene products, most likely derived from the b and c loci.

Tyrosinase isoenzymes in mammalian melanocytes. 2. Differential activation by alpha-melanocyte-stimulating hormone

In mouse melanoma melanocytes, alpha-melanocyte-stimulating hormone (MSH) stimulates differentiation, melanin synthesis and tyrosinase activity. However, the molecular mechanisms underlying these events have not yet been characterized. We have studied the activation of tyrosinase by MSH. Treatment of B16 melanoma cells with either theophylline, MSH, or its superpotent analog [Ahx4, DPhe7]MSH promotes a larger induction of tyrosine hydroxylase than of dopa oxidase activity in whole cell extracts. This higher activation of tyrosine hydroxylation was found not only in the melanosomal but also in the microsomal fraction; it appears to be dependent on continued transcription and translation since it can be blocked by actinomycin and cycloheximide. The tyrosinase activity of control and theophylline-treated extracts displayed several kinetic differences, including different Km values for both substrates and requirements for the cofactor L-dopa. SDS/PAGE, followed by a sensitive specific activity stain, demonstrated that melanosomes of control cells contain one lower-electrophoretic-mobility form of tyrosinase, whereas melanosomes of cells treated with either theophylline or MSH display, in addition to the lower-mobility form, a faster-migrating activity band. These tyrosinase forms are not interconvertible by proteolysis or deglycosylation. Their nature is discussed as related to the properties of the previously described low- and high-electrophoretic-mobility tyrosinases (LEMT and HEMT), as well as of the proteins encoded by the c and b loci.

Preparation of purified tyrosinase devoid of dopachrome tautomerase from mammalian malignant melanocytes

Although tyrosinase has been considered for a long time the only enzyme involved in mammalian melanosynthesis, it has been shown that mouse melanoma melanosomes contain high levels of dopachrome tautomerase (DCT2), an enzyme catalyzing DC tautomerization to DHICA. At least in B16 mouse melanoma, DCT is present in higher catalytic amounts than tyrosinase. Moreover, it can be anticipated that tyrosinase and DCT should be very difficult to resolve by most conventional biochemical techniques because of the structural similarity between these enzymes, as predicted from the sequence of their corresponding cDNAs. It is shown that the presence of DCT can cause serious artifacts when tyrosinase activity is determined by most of the currently available methods, such as the Dopa oxidase and melanin formation assays. We describe a simple and convenient method for the preparation of tyrosinase devoid of DCT. The method takes advantage of the different thermal stability of both enzymes. Heating of crude melanosomal extracts at 60 degrees C for 1 hr results in a complete denaturation of DCT, while tyrosinase activity is recovered almost quantitatively. The resulting tyrosinase preparation is considerably purified and the electrophoretic, immunologic and kinetic characteristics of the enzyme appear unaltered. Because if its high yield and simplicity, the method can be used for the microscale partial purification of DCT-free tyrosinase from mammalian malignant melanocytes grown in culture.

Selective fluorescence of eosinophilic structures in grasshopper and mammalian testis stained with haematoxylin-eosin

After staining with Mayer's haematoxylin and eosin Y, paraffin sections of grasshopper and mouse testis were analysed by both transmitted light and fluorescence microscopy. Under violet-blue (436 nm) light excitation, a bright green emission was observed in all eosinophilic structures. Meiotic spindles (fibres and poles), mitochondrial aggregates, centriolar adjuncts in grasshopper spermatids, the basal lamina, flagellar bundles and remaining cytoplasmic droplets in the lumen of seminiferous tubules showed the most striking fluorescence induced by eosin Y. No emission was found in these structures after haemalum staining. Fluorescent microtubular components also revealed a positive immunoperoxidase reaction for alpha-tubulin. All fixation and embedding procedures (Bouin, Zenker, formaldehyde alone or followed by dichromate or glutaraldehyde, freeze-substitution) were suitable for observation by fluorescence microscopy. Acetylation, deamination, and prolonged washing of stained sections with water, salt solution or ethanol strongly reduced eosin Y fluorescence, while it slightly increased after methylation. These results show that routine haematoxylin-eosin stained tissue sections can be routinely analysed by fluorescence microscopy. The emission of eosin Y allows easy and precise recognition of eosinophilic structures, which are poorly visible under bright field illumination.

Proteolysis with trypsin of mammalian tyrosinase isoforms from B16 mouse melanoma

In spite of the central role of tyrosinase in mammalian pigmentation, few data are available on its structure and structure-function relationships based on direct analysis of the protein. A number of reasons have been invoked to account for this situation, including the problems for its purification and its resistance to proteases. However, no study on the effects of proteases on purified tyrosinase has been reported. We have purified the melanosomal and cytosolic tyrosinases from B16 mouse melanoma and analyzed their susceptibility to trypsin digestion. Both isoforms are sensitive to trypsin, and display similar peptide maps and kinetics of proteolysis, suggesting that they are products of the same gene. The peptide maps and the kinetics of appearance of the fragments were consistent with the sequential removal of N-terminal peptides, leading to a core of 55.3 kDa for the melanosomal form and 48.6 kDa for the cytosolic enzyme. This core was apparently resistant to further proteolysis and catalytically inactive. The difference in molecular weight for the core of the cytosolic and melanosomal forms is the same as that calculated for the native isoforms. The kinetics of enzyme inactivation indicate that the tyrosine hydroxylase and Dopa oxidase activities of tyrosinase are lost at the same rate, and should therefore display similar if not identical structural requirements. The results are discussed in terms of the relationship of both isoforms and of the putative protein sequences deduced from the cDNA clones proposed for tyrosinase.