Study Protocol for the Social Interventions for Support During Treatment for Endometrial Cancer and Recurrence (SISTER) study: a community engaged national randomized trial

Aim: Social isolation in cancer patients is correlated with prognosis and is a potential mediator of treatment completion. Black women with endometrial cancer (EC) are at increased risk for social isolation when compared with White patients. We developed the Social Interventions for Support during Treatment for Endometrial Cancer and Recurrence (SISTER) study to compare and evaluate interventions to address social isolation among Black women with high-risk EC in USA. The primary objective of the SISTER study is to determine whether virtual support interventions improve treatment completion compared with Enhanced Usual Care. Secondary objectives include comparing effectiveness virtual evidence-based interventions and evaluating barriers and facilitators to social support delivery. Patients & methods: This is a multi-site prospective, open-label, community-engaged randomized controlled trial, consisting of three intervention arms: enhanced usual care, facilitated support group and one-to-one peer support. Primary outcome will be measured using relative dose. Qualitative semi-structured interviews will be conducted with a subset of participants to contextualize the relative degree or lack thereof of social isolation, over time. Data analysis: Primary analysis will be based on an intent-to-treat analysis. Multivariable analysis will be performed to determine the effect of the intervention on the primary and secondary outcomes of interest, relative dose and social isolation score. Semi-structured interviews will be qualitatively analyzed using inductive and deductive approaches of content analysis. Discussion/conclusion: Endometrial cancer mortality disproportionately affects Black women, and social isolation contributes to this disparity. The SISTER study aims to identify whether and to what extent differing social support vehicles improve key outcomes for Black women in the United States with high-risk EC. Clinical Trial Registration: NCT04930159 (ClinicalTrials.gov).

The Integration of Value Assessment and Social Network Methods for Breast Health Navigation Among African Americans

OBJECTIVES

A major strategy to reduce the impact of breast cancer (BC) among African Americans (AA) is patient navigation, defined here as individualized assistance for reducing barriers to healthcare use. The primary focus of this study was to estimate the added value of incorporating breast health promotion by navigated participants and the subsequent BC screenings that network members may obtain.

METHODS

In this study, we compared the cost-effectiveness of navigation across 2 scenarios. First, we examine the effect of navigation on AA participants (scenario 1). Second, we examine the effect of navigation on AA participants and their networks (scenario 2). We leverage data from multiple studies in South Chicago. Our primary outcome (BC screening) is intermediate, given limited available quantitative data on the long-term benefits of BC screening for AA populations.

RESULTS

When considering participant effects alone (scenario 1), the incremental cost-effectiveness ratio was $3845 per additional screening mammogram. When including participant and network effects (scenario 2), the incremental cost-effectiveness ratio was $1098 per additional screening mammogram.

CONCLUSION

Our findings suggest that inclusion of network effects can contribute to a more precise, comprehensive assessment of interventions for underserved communities.

Increasing Racial and Ethnic Diversity in Cancer Clinical Trials: An American Society of Clinical Oncology and Association of Community Cancer Centers Joint Research Statement

A concerted commitment across research stakeholders is necessary to increase equity, diversity, and inclusion (EDI) and address barriers to cancer clinical trial recruitment and participation. Racial and ethnic diversity among trial participants is key to understanding intrinsic and extrinsic factors that may affect patient response to cancer treatments. This ASCO and Association of Community Cancer Centers (ACCC) Research Statement presents specific recommendations and strategies for the research community to improve EDI in cancer clinical trials. There are six overarching recommendations: (1) clinical trials are an integral component of high-quality cancer care, and every person with cancer should have the opportunity to participate; (2) trial sponsors and investigators should design and implement trials with a focus on reducing barriers and enhancing EDI, and work with sites to conduct trials in ways that increase participation of under-represented populations; (3) trial sponsors, researchers, and sites should form long-standing partnerships with patients, patient advocacy groups, and community leaders and groups; (4) anyone designing or conducting trials should complete recurring education, training, and evaluation to demonstrate and maintain cross-cultural competencies, mitigation of bias, effective communication, and a commitment to achieving EDI; (5) research stakeholders should invest in programs and policies that increase EDI in trials and in the research workforce; and (6) research stakeholders should collect and publish aggregate data on racial and ethnic diversity of trial participants when reporting results of trials, programs, and interventions to increase EDI. The recommendations are intended to serve as a guide for the research community to improve participation rates among people from racial and ethnic minority populations historically under-represented in cancer clinical trials. ASCO and ACCC will work at all levels to advance the recommendations in this publication.

Abstract PO-208: The value of estimating spillover effects in health equity interventions: A case study to promote mammogram uptake among African American women and their social networks

Introduction: Standard economic evaluation methods may underestimate the value of health equity interventions by focusing exclusively on program costs and direct effects on participants' health. Yet, these interventions have spillover effects – wherein participants transition from being intervention recipients to becoming health advocates for their social networks. Consequently, interventions may improve the health of participants and other community members who are not directly connected with interventions. This study demonstrates the utility of incorporating spillover effects by comparing incremental cost-effectiveness ratios via a patient navigation intervention to promote mammography screening among African American (AA) women. Specifically, we compare the relative costs and cost-effectiveness when including mammography uptake of: (1) AA intervention participants (egos) only versus (2) AA intervention participants (egos) and their screening eligible social network members (alters). Methods: Our study draws from two studies: (1) an individual randomized trial to test the efficacy of patient navigation on mammography uptake (Patient Navigation in Medically Underserved Areas [PNMUA]) and (2) an observational ancillary study to test the effects of PNMUA on breast cancer survivor egos and their alters (Offering AA Survivors Increased Support [OASIS]). Overall, we used a healthcare system perspective. For 2021 cost data, we collected data from study records and expense reports. For effects data, we used: (1) medical record data for egos' mammography uptake, (2) self-report data from egos regarding their alters' mammography uptake, and (3) self-report data from alters about their own mammography uptake. We consequently computed incremental cost-effectiveness ratios (ICERs), using different data sources, to assess the impact of estimating spillover effects on economic evaluation of patient navigation. Results: Total cost of the intervention was $196,601. The greatest expense were breast cancer navigators' salaries and fringe rates ($126,745). In PNMUA, more navigated vs. non-navigated egos obtained biennial mammograms (45% vs. 39%). In terms of spillover effects, more navigation arm alters obtained biennial mammograms compared to alters in the non-navigated arm (ego self-report: n=1296 vs 949; alter self-report: n=1521 vs. 1195). Navigation had lower value when only incorporating participants' mammography uptake ($3,277 per each additional woman screened) versus when incorporating spillover effects ($2,027-$2,114 per each additional woman screened). Conclusion: Our results suggest breast cancer navigation programs may be more valuable when including spillover effects. This case study provides insight with real-world applicability into integrating spillover effects into economic evaluation. Our methods offer a new avenue for improved cost and effect estimates of health equity interventions, which may be useful for assessing future resource allocation in healthcare practice and policy.

Citation Format: Nyahne Bergeron, Veronica Fitzpatrick, Carl Asche, Karriem S. Watson, Aditya S. Khanna, Bridgette Hempstead, Elizabeth A. Calhoun, Jean McDougall, Yamilé Molina. The value of estimating spillover effects in health equity interventions: A case study to promote mammogram uptake among African American women and their social networks [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-208.

Oncology provider and African-American breast cancer survivor perceptions of the emotional experience of transitioning to survivorship

PURPOSE

To examine the emotional experience of African American breast cancer survivors (BCS), and the information exchange between providers and patients, during transitioning to post-treatment survivorship.

RESEARCH APPROACH

We conducted a qualitative study using interviews and focus groups.

PARTICIPANTS

We sought perspectives of oncology providers (n = 27) and African-American breast cancer survivors (BCS) (n = 45) who provided and received care in three counties in Washington State.

METHODS

African-American community consultants conducted interviews and focus groups. Thematic coding and constant comparison were applied to identify emergent themes.

FINDINGS

Participants reported emotional health information and support were needed but not consistently provided, resulting in a sense of survivor isolation. Systemic challenges limited providers' ability to deliver emotional support information. Survivors and providers expressed similar understandings of the emotional impact of transition, but each group highlighted different, yet complementary priorities to address emotional needs of African-American BCS.

CONCLUSIONS

There is congruence between African-American BCS and oncology providers perceptions of the emotional experience of transitioning to post-treatment survivorship, but patients are not receiving adequate information and resources to help them adequately address their emotional needs.

IMPLICATIONS FOR POLICY

Improved care continuity, team-based approaches, and partnerships between health systems and community organization partnerships may help patients and providers recognize and address emotional needs during the transition.

Seeking Black Women's Voices in Endometrial Cancer Research via Deliberate Community Engagement

BACKGROUND

Black women with endometrial cancer (EC) are diagnosed at advanced stages and have markedly high mortality rates compared with women of other races. EC disparities research lacks both qualitative work and engagement of Black women. We sought to describe developing a community-research partnership to examine EC among Black women.

METHODS

We apply the Public Health Critical Race (PCHR) praxis to examine how race and racism shaped our partnership development. We used story telling, goal setting, and iterative collaboration tools to build our relationship and research study.

RESULTS

Common racial and gender identities played an important role in establishing partnership. Active management of historical institutional discrimination, co-learning activities, and transparency were critical to successful collaboration and research development.

CONCLUSIONS

Using community engagement and race-conscious approaches, we laid the groundwork for addressing a major knowledge gap in racial inequity in EC.

Assessment of Prediagnostic Experiences of Black Women With Endometrial Cancer in the United States

IMPORTANCE

Black women with endometrial cancer have a 90% higher mortality rate than white women with endometrial cancer. The advanced disease stage at which black women receive a diagnosis of endometrial cancer is a major factor in this disparity and is not explained by differences in health care access.

OBJECTIVE

To describe the prediagnostic experiences of symptoms and symptom disclosure among black women with endometrial cancer.

DESIGN, SETTING, AND PARTICIPANTS

This community-engaged qualitative study developed an interview guide to collect data during semistructured interviews among a sample of 15 black women with endometrial cancer in the United States. Interviews were conducted in person or via a secure conferencing platform. An exploratory and descriptive content analysis was performed using iterative rounds of inductive coding, case summaries, and coanalysis with community input to identify emergent themes. Data were collected from October 3, 2017, to April 15, 2019, and the descriptive content analysis was performed from October 11, 2017, to May 6, 2019.

MAIN OUTCOMES AND MEASURES

Beliefs, interpretations, and experiences of black women with endometrial cancer from symptom onset to diagnostic confirmation of cancer.

RESULTS

Participants included 15 women who self-identified as black or African American and ranged in age from 31 to 72 years. Eight participants lived in the Puget Sound region of Washington, 2 participants lived in California, and 1 participant each lived in Alabama, Michigan, Louisiana, Georgia, and New York. Twelve participants were receiving adjuvant therapy during the study, which indicated that they were either in a high-risk group and/or had advanced-stage disease. Thirteen participants had health insurance at the time of symptom onset, and all participants had elected to receive cancer treatment. Participants described knowledge gaps and silence about menopause, misinterpretation of vaginal bleeding, and responses by first-line health care practitioners that were not aligned with the risk of endometrial cancer among black women in the United States.

CONCLUSIONS AND RELEVANCE

The responses of interviewed black women with endometrial cancer suggest that several mechanisms may be associated with a delay in care before diagnosis among this high-risk population and represent modifiable factors that may be useful in the development of targeted interventions to improve the rates of early diagnosis among black women with endometrial cancer.

Community Empowerment Partners (CEPs): A Breast Health Education Program for African-American Women

Peer educators have been shown to provide effective interventions in breast cancer screening. Few studies have compared the effects of peer education on breast cancer knowledge among peer educators and the community members who are subsequently reached through the peer education. Further, little is known as to whether those who received the education then go on to educate others in the community. The purpose of this study is to address those gaps. Using a pre- and post-test study design, we trained peer educators, provided the educators with resources to train community members, and assessed changes in knowledge. We sought to train ten educators and recommended each train ten community members in breast cancer knowledge and screening strategies. A total of 14 peer educators were trained, who subsequently trained a total of 121 community members, of whom 94 were African American women. Peer educators and community members, showed comparable increases in knowledge. Community members who were educated also increased intention to discuss breast cancer and breast cancer screening with their family, friends, and acquaintances. Our study suggests that it is feasible to train peer educators to increase knowledge among community members to the same level that they themselves experience when trained. Further, community members are interested in sharing information learned related to how much they learn from peer educators.

YIA19-001: Mechanisms of Diagnostic Delay Among Black women With Endometrial Cancer (EC): Results from Qualitative Interviews and a National Analysis of Healthcare Data

Background: A major contributor to the black-white mortality gap in endometrial cancer (EC) is late stage at diagnosis for black women, which may be driven by delays in diagnosis both prior to and after symptom disclosure. Methods: For phase 1, black women with EC were recruited through oncology clinics and a local cancer support group. In-depth interviews were conducted focused on experiences of menopause, postmenopausal bleeding (PMB), and symptom disclosure, and transcripts coded using directed content analysis. For phase 2, EC cases from 2001–2015 were identified in SEER-Medicare. Location, provider type, and dates of symptom report and diagnosis were defined by claims data. The diagnostic interval was then calculated and step-wise multivariate modeling used to determine factors associated with time to diagnosis. Results: Phase 1 included 11 black women from 4 states (WA, LA, GA, CA), ages 47–70, stages 1––3 at diagnosis, for a total of 147 pages of transcribed interviews. Most were insured, with access to routine medical care. Common themes were a lack of knowledge of normal vs abnormal menopausal symptoms and silencing about bleeding among friends and family. The predominant interpretation of PMB was a resumption of normal menstruation, leading to significant delay in symptom disclosure. Reporting to an MD was largely driven by increased severity of bleeding or the onset of pain. Phase 2 included 3,363 EC cases, with 293 (8%) black women. The median diagnostic interval was 28 days (IQR: 8–110 days). After adjusting for age, region, gynecologic history and other presenting symptoms, provider differences were noted with shorter time for ER MDs (84%; P<.01) and PCPs (16%; P=.05) vs OBGYN. Characterization of bleeding as ‘abnormal’ rather than ‘postmenopausal’ prolonged time to diagnosis by 60% (P<.001). Black race was associated with a 2.4-fold increased diagnostic time interval (P=.017). Step-wise modeling showed that this association was explained by differences in diagnostic work-up: Compared to those with a biopsy within 7 days of presentation, women who had an ultrasound or no procedures had longer intervals (42% and 99%, respectively) to diagnosis (P<.001 for all). Conclusion: Among black women with access to medical care, there are modifiable factors that contribute to delays in diagnosis of EC both prior to and after symptom disclosure to a physician. This is the first study to identify targets for intervention to reduce the mortality rate in this high-risk group.

Abstract A61: Perspectives on transitioning from cancer treatment to breast cancer survivorship

Introduction: The population of breast cancer survivors continues to grow due to improved medical treatments and education. Yet there is a lack of comprehensive survivorship care planning to manage overall health following cancer treatment. The Institute of Medicine (IOM) recommends psychosocial components be included in survivorship care plans to address long-term psychological distress. African Americans in particular experience disproportionate levels of psychosocial distress in breast cancer survivorship. Thus the goal of this study was to understand the psychosocial needs, resources, and cultural influences during the transition from treatment to survivorship from the perspectives of both the oncology professionals and survivors themselves.

Methods: Twenty-nine, semi-structured one-on-one interviews were conducted in Washington State by African-American community advocates as part of a larger on-going study. Twelve oncology professionals (OPs) and 17 female African-American breast cancer survivors (BCSs) were interviewed. Open-ended interview guides were tailored for BCSs and OPs respectively. Interviews were transcribed, coded, and analyzed using principles of constant comparison grounded theory, in which concepts were identified and themes derived from interview data. Interviews were approximately 45 minutes in duration and participants received $40 compensation for their time.

Results: Similar to previous literature, psychosocial needs identified by both BCSs and OPs included fear of recurrence, emotional and financial distress, and support issues. However, the role of daily stressors and microaggressions described by many BCSs were not widely identified by OPs. BCSs also indicated a need for more empathetic interactions from OPs during medical visits. A major gap identified between the BCSs and OPs was found in the source of psychosocial information provided to BCSs. Nearly half of the BCSs indicated psychosocial support was received from community-based programs (spiritual and secular) whereas many OPs believed support was provided as part of clinical services at their institution. However, several OPs did state that there are numerous community resources available to survivors. Many professionals stated that a structured protocol is not in place to help survivors identify available services and some specifically identified the need to include psychosocial factors in the survivorship care plan. A few OPs suggested that follow-up appointments with survivors 3-, 6- and 12-months after cancer treatment may reduce feelings of isolation and lack of support. With regard to cultural factors that may impact the transition to survivorship, many of the BCSs noted they did not openly share their cancer experience with others, family/friends or professionals, which they indicated is an African-American cultural trait; specifically, the desire to appear as a “strong” woman. Some OPs also mentioned this aspect of the African-American culture as a possible barrier to communication about psychosocial well-being during medical visits. Some survivors conveyed interest in mentoring future BCSs stating a need for African Americans to support each other, but did not specifically describe how this support would differ from other sources of support. OPs discussed historical injustices as a potential source of mistrust within African American breast cancer survivors.

Conclusion: While there are many areas of overlap between BCSs and OPs regarding psychosocial needs of African-American BCSs, there remain gaps of primarily social and institutional systemic barriers to care. Study limitations and some recommendations to meet the psychosocial needs of African American breast cancer survivors have emerged from the interviews and are discussed.

Citation Format: Swati Somuri, Rachel M. Ceballos, Sarah H. Hohl, Rachel M. Malen, Bridgette Hempstead, Jacci Thompson-Dodd. Perspectives on transitioning from cancer treatment to breast cancer survivorship. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr A61.

Abstract A09: Perceptions of oncology professionals and African American breast cancer survivors on the experience of transitioning from breast cancer patient to survivor

Introduction: While survivor care planning is currently the focus of much research, the process of communication between providers and patients, as well as, perceptions of the patient experience during the time of transition from patient to survivor, is not well understood. While this period of transition can be one of joy and hope, emotional distress can occur for patients as they face fears of recurrence and reduced oversight of their cancer status. For African-American patients this period may include unique concerns that should be more closely investigated. To address this, the current study explored the needs, barriers, and facilitators present during the period of transition from the perspective of both oncology professionals (OP) and African-American breast cancer survivors (AA-BCS).

Methods: African-American community advocates with extensive skill in elicitation conducted 29 semi-structured one-on-one interviews. Twelve OPs (e.g. social workers, nurses, oncologists) and 17 female AA-BCSs were interviewed. The interview guides were tailored for BCSs and OPs respectively, and aimed to: 1) elicit perspectives about medical and psychosocial information presented to patients 2) understand the cognitive and emotional experience of AA-BCSs as they receive medical and psychosocial information about post-treatment cancer survivorship and 3) identify perceived barriers, facilitators, and goals toward providing necessary information and emotional support to AA-BCS in particular. Interviews were transcribed, coded, and analyzed using principles of constant comparison grounded theory, in which concepts were identified and themes derived from interview data.

Results: Many AA-BCSs reported feeling confident in their medical care but some noted concerns, such as, reluctance to ask questions of OPs and perceived micro-aggressions in the medical environment. Overall, AA-BCSs and OPs reported similar medical information being presented to patients (e.g., post-treatment care, medication side effects, and logistical considerations), but gaps were noted in both groups with regard to communication of psychosocial and financial resources. For instance, BCSs reported the majority of psychosocial information and social support needs were met through community-based not hospital-based programs. OPs, specifically, recognized there are often “gaps in patient handoffs” highlighting the need for more cross-communication between OPs providing dissimilar specialties. Medically, however, most AA-BCSs perceived their care as equivalent to that received by patients from other ethnicities. Few OPs identified differences in medical or cultural needs of many African-Americans, but a small number noted AA-BCSs may have more difficulty asking questions of OPs and would benefit from patient advocacy. While a limited number of OPs identified issues such as skin discoloration due to radiation, a lack of images that represented the African-American community during reconstructive surgery, the effect of historical insults on interaction with medical professionals, and the presence of more aggressive breast cancer among younger African-Americans, many OPs identified a need for more cross-cultural training. Many OPs, however, did mention observing higher rates of external social support, spirituality, and resilience among AA-BCSs, which was echoed by the AA-BCSs themselves. The benefit of compassionate communication was also identified by OPs and AA-BCSs as an important contributor to overcoming potential barriers during this period of transition.

Conclusion: The results of this study suggest, medically, AA-BCSs were generally satisfied with their care, but the presence of perceived micro-aggressions and reluctance to ask questions of OPs should be further explored. OPs acknowledged the need for more cross-cultural training, but appeared reluctant to discuss perceived differences in the needs or experience of AA-BCSs. These and other issues will be presented.

Citation Format: Rachel M. Ceballos, Sarah D. Hohl, Bridgette Hempstead, Jacci Thompson-Dodd, Rachel C. Malen. Perceptions of oncology professionals and African American breast cancer survivors on the experience of transitioning from breast cancer patient to survivor. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr A09. doi:10.1158/1538-7755.DISP13-A09

NGF activates similar intracellular signaling pathways in vascular smooth muscle cells as PDGF-BB but elicits different biological responses

The signaling pathways that regulate smooth muscle cell migration and proliferation are incompletely understood. Smooth muscle cells express at least 3 families of receptor tyrosine kinases that mediate cell migration: platelet-derived growth factor (PDGF) receptors, the trk family of neurotrophin receptors, and insulin-like growth factor 1 receptor. The neurotrophin, nerve growth factor (NGF), and insulin-like growth factor 1 induce the migration but not the proliferation of smooth muscle cells, whereas PDGF-BB stimulates both responses. To determine whether distinct signaling pathways downstream of receptor tyrosine kinases specifically mediate smooth muscle cell migration or proliferation, the ligand-induced activation of different signaling pathways in smooth muscle cells was examined. NGF induces prolonged activation of the Shc/MAP kinase pathway and phospholipase Cgamma compared with PDGF-BB. The activation of phosphatidylinositol-3 kinase, however, was 10-fold greater in response to PDGF-BB compared with NGF. Insulin-like growth factor 1 activates only phosphatidylinositol-3 kinase. Pharmacological inhibitors of phosphatidylinositol-3 kinase, Wortmannin and LY294002, inhibit PDGF-BB and NGF-induced migration, whereas an inhibitor of MAP kinase kinase, PD98059, has no effect. Our results suggest that (1) different receptor tyrosine kinases use similar patterns of activation of signaling pathways to mediate distinct biological outcomes of cell migration and proliferation, (2) NGF activates signaling proteins in smooth muscle cells similar to those activated during NGF-induced neuronal differentiation, and (3) the combinatorial effects of different signaling pathways are important for the regulation of smooth muscle cell migration and proliferation. Further studies using mutant trk receptors will help to define the signal transduction pathways mediating NGF-induced smooth muscle cell migration.

Differential modulation of neuron survival during development by nerve growth factor binding to the p75 neurotrophin receptor

Nerve growth factor (NGF) supports the survival and differentiation of distinct populations of peripheral and central neurons. NGF binds to two classes of cell-surface receptors, the protein tyrosine kinase TrkA and the smaller p75 receptor lacking intrinsic catalytic activity. It has been suggested that both receptors are required for NGF high affinity binding, although TrkA appears to be sufficient for transducing most of the biological effects of NGF. Some evidence suggests that p75 could play a modulatory role on TrkA activation by an as yet unknown mechanism. In this study, we have investigated functional roles of p75 using a purified triple mutant NGF (triNGF) deficient in p75 binding but retaining significant TrkA binding and activation. The mutant was found to be as potent as wild type NGF at promoting survival of serum-deprived TrkA-expressing fibroblasts. On developing chick sensory neurons, survival responses to mutant and native NGF were indistinguishable when assayed at nanomolar concentrations. However, triNGF was 3- to 4-fold less potent than wild type NGF at lower concentrations (i.e. 10(-11) M). Interestingly, in PC12 cells coexpressing TrkA and p75, no high affinity binding sites for triNGF could be detected. The reduced responsiveness to triNGF in sensory neurons was increasingly evident at later developmental stages; late embryonic neurons did not respond at all to concentrations of triNGF that were saturating at earlier developmental stages. Likewise, although no difference could be seen between wild type and mutant NGF on the survival responses of embryonic rat superior cervical ganglion sympathetic neurons, the mutant was much less potent than native NGF on postnatal sympathetic neurons. In sensory neurons, the decrease in responsiveness to triNGF correlated with a developmental reduction in the expression of both p75 and TrkA. Thus, NGF binding to p75 enhances responsiveness to ligand, particularly when this is present at limiting concentrations. During development, p75 modulates responsiveness to NGF so that binding to p75 becomes increasingly important in neurons undergoing a down-regulation of NGF receptors. These results support a ligand-dependent modulatory role for p75 in NGF-mediated neuron survival consistent with p75 functioning as a TrkA regulator and/or signaling receptor.

Neurotrophin and neurotrophin receptors in human fetal kidney

Vertebrate kidney development involves a series of complex interactions between the ureteric bud and undifferentiated mesenchyme resulting in the production of the nephron unit. These interactions are thought to be dependent on a variety of locally derived soluble factors, including peptide growth factors and their receptors. We have extensively analyzed the neurotrophins (NT) and their receptors during human kidney development. The neurotrophin receptors p75 and trk were both present within cells of early glomerular/tubular structures but absent from uninduced mesenchyme. Later in organogenesis, the NTs NT-3 and BDNF colocalized with their respective receptors in differentiated tubules. These findings suggested that the NT:receptor complex was not involved in the early inductive events of renal development but was responsible for postinductive tubulogenesis and epithelial integrity. In situ hybridization confirmed selective localization for the expression of trk B and trk C receptors and Western blot identified a full-length (kinase-active) trk receptor during human kidney development.

Nerve growth factor signal transduction in human B lymphocytes is mediated by gp140trk

Nerve growth factor (NGF) plays an important role in the regulation of the immune system. Recent studies from this laboratory demonstrated the presence of functional NGF receptors on human B lymphocytes; in addition, NGF has been shown to enhance B lymphocyte proliferation. NGF caused both concentration- and time-dependent increases in tyrosine phosphorylation of five proteins of 140, 110, 85, 60 and 42 kDa, which were identified as phospholipase C-gamma 1, phosphatidylinositol-3 kinase and mitogen-activated protein kinase. To elucidate the contribution of the Trk family of tyrosine kinases to the phosphorylation events induced by NGF, we identified gp140trk in human B cells and in human B cell lines. Analysis of specific gp140trk immunoprecipitates indicated that addition of NGF to B cells induced a rapid increase in the tyrosine phosphorylation of gp140trk and inhibition of this phosphorylation prevented the tyrosine phosphorylation of other proteins. These data identify the central role of gp40trk in NGF signaling of human B lymphocytes.

Identification of the neurotrophin receptors p75 and trk in a series of Wilms' tumors

The molecular mechanisms underlying the pathogenesis of Wilms' tumor (WT) are poorly understood, although a variety of growth factors including platelet-derived growth factor and insulin-like growth factor are expressed and are thought to contribute to tumor development. In earlier studies, WT cells in culture were found to express the low affinity nerve growth factor receptor, p75. These WT cells were capable of responding to the neurotrophin (NT) NGF, suggesting that NT may be involved in WT pathogenesis. We have examined a group of WT immunohistochemically with antibodies recognizing known trk receptor proteins, the p75 receptor, and the NTs, NGF and NT-3. Confirmatory immunoprecipitation and Western blots were then performed on representative WT samples from the study group. The p75 receptor was found predominantly in the epithelial and blastemal components where high levels of NT were also identified. The trk A and B receptors were primarily within stromal components, whereas the trk C and C' receptors were present within epithelial structures. Western blot analyses confirmed the presence of the respective receptor proteins with variations correlating in some cases with histological type. The selective presence of NT receptors and growth factors in this series of WT implies autocrine/paracrine mechanisms for tumor development.

Analysis of the trk NGF receptor tyrosine kinase using recombinant fusion proteins

Nerve growth factor (NGF) represents a family of structurally related trophic factors, including brain-derived neurotrophin factor (BDNF), neurotrophin-3 (NT-3), NT-4, and NT-5. These neurotrophin factors interact with two classes of receptors, the trk receptor tyrosine kinase family, and the low affinity p75 neurotrophin receptor. To study potential ligand-receptor interactions, recombinant trk fusion proteins have been constructed, and pan-trk polyclonal antisera directed against the cytoplasmic tyrosine kinase domain have been generated. The recombinant proteins were assessed for in vitro kinase activity and for the ability of K-252a to inhibit phosphorylation. Antibodies made against the fusion protein recognize all trk family members, and are effective in immunoprecipitation of affinity-crosslinked receptors. Comparative crosslinking indicates that NGF can recognize all trk receptor members, illustrating the large number of potential ligand-receptor interactions between neurotrophins and their receptors.