Prospective Study Testing a Simplified Paclitaxel Premedication Regimen in Patients with Early Breast Cancer.

BACKGROUND: In early trials, hypersensitivity reactions (HSRs) to paclitaxel were common, thus prompting the administration of antihistamines and corticosteroids before every paclitaxel dose. We tested the safety of omitting corticosteroids after cycle 2 during the paclitaxel portion of the dose-dense (DD) doxorubicin-cyclophosphamide (AC)-paclitaxel regimen. PATIENTS, MATERIALS, AND METHODS: In this prospective, single-arm study, patients who completed four cycles of DD-AC for stage I-III breast cancer received paclitaxel 175 mg/m2 every 2 weeks for four cycles. Patients received a standard premedication protocol containing dexamethasone, diphenhydramine, and a histamine H2 blocker prior to the first two paclitaxel cycles. Dexamethasone was omitted in cycles three and four if there were no HSRs in previous cycles. We estimated the rate of grade 3-4 HSRs. RESULTS: Among 127 patients enrolled, 125 received more than one dose of protocol therapy and are included in the analysis. Fourteen (11.2%; 90% confidence interval, 6.9%-20.0%) patients had any-grade HSRs, for a total of 22 (4.5%; 3.1%-6.4%) HSRs over 486 paclitaxel cycles. Any-grade HSRs occurred in 1.6% (0.3%-5.0%), 6.5% (3.3%-11.3%), 7.4% (3.9%-12.5%), and 2.6% (0.7%-6.6%) of patients after paclitaxel cycles 1, 2, 3, and 4, respectively. Dexamethasone use was decreased by 92.8% in cycles 3 and 4. Only one patient experienced grade 3 HSR in cycles 3 or 4, for a rate of grade 3/4 HSR 0.4% (0.02%-2.0%) (1/237 paclitaxel infusions). That patient had grade 2 HSR during cycle 2, and the subsequent grade 3 event occurred despite usual dexamethasone premedication. A sensitivity analysis restricted to patients not known to have received dexamethasone in cycles 3 and 4 found that any-grade HSRs occurred in 2.7% (3/111; 0.7%-6.8%) and 0.9% (1/109; 0.05%-4.3%) of patients in cycle 3 and 4, respectively. CONCLUSION: Corticosteroid premedication can be safely omitted in cycles 3 and 4 of dose-dense paclitaxel if HSRs are not observed during cycles 1 and 2. IMPLICATIONS FOR PRACTICE: Because of the potential for hypersensitivity reactions (HSRs) to paclitaxel, corticosteroids are routinely prescribed prior to each dose, on an indefinite basis. This prospective study, including 125 patients treated with 486 paclitaxel cycles, demonstrates that corticosteroids can be safely omitted in future cycles if HSRs did not occur during cycles 1 and 2 of paclitaxel and that this strategy reduces the use of corticosteroids in cycles 3 and 4 by 92.8% relative to current standard of care.

Quantitative measurements of HER2 and phospho-HER2 expression: correlation with pathologic response to neoadjuvant chemotherapy and trastuzumab.

BACKGROUND: Preoperative therapy with chemotherapy and the HER2-targeted monoclonal antibody trastuzumab is valuable for patients with large or locally advanced HER2-positive (HER2+) breast cancers but traditional methods of measuring HER2 expression do not accurately stratify patients for likelihood of response. Quantitative immunofluorescent approaches have the potential to provide a mathematically continuous measure of HER2. Here we seek to determine whether quantitative measurement of HER2 or phospho-HER2 correlates with likelihood of response to trastuzumab- containing neoadjuvant therapy. METHODS: We evaluated core biopsy samples from 27 HER2+ breast cancer patients enrolled in a preoperative clinical trial using trastuzumab, nab-paclitaxel and carboplatin combination therapy (BrUOG BR-211B (NCT00617942)). Tumor core biopsies were taken before initiation of treatment and 9-13 days after patients received "run-in" doses of either single agent trastuzumab or nab-paclitaxel. The AQUA method of quantitative immunofluorescence was used for analysis of in situ protein expression. Patients then received 18 weeks of treatment, followed by surgery to assess pathologic response to the neoadjuvant regimen. RESULTS: A HER2 score of 2111 by AQUA analysis has been shown to be equivalent to HER2 3+ by immunohistochemical staining in previous studies. Of 20 evaluable patients, 10 cases who achieved a pathologic complete response (pathCR) with neoadjuvant treatment had a mean HER2 level of 10251 compared with 4766 in the patients without pathCR (p = 0.0021). Measurement of phospho-HER2 showed no difference in pathCR vs non-pathCR groups. In 9 patients who had HER2 levels repeated after a single treatment with trastuzumab there was no evidence of a reduction in the HER2 or phospho-HER2 levels following that exposure. CONCLUSIONS: High levels of HER2 are associated with achievement of a pathCR in the preoperative setting, while levels of Phospho-HER2 were not predictive of response. This data suggests that accurate measurement of HER2 may help determine the likelihood of response in the pre-surgical setting. Further validation in larger cohorts is required, but this pilot data shows the feasibility of this approach.

PACE: A Randomized Phase II Study of Fulvestrant, Palbociclib, and Avelumab After Progression on Cyclin-Dependent Kinase 4/6 Inhibitor and Aromatase Inhibitor for Hormone Receptor-Positive/Human Epidermal Growth Factor Receptor-Negative Metastatic Breast Cancer.

PURPOSE: Cyclin-dependent kinase (CDK) 4/6 inhibitors (CDK4/6is) are an important component of treatment for hormone receptor-positive/human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC), but it is not known if patients might derive benefit from continuation of CDK4/6i with endocrine therapy beyond initial tumor progression or if the addition of checkpoint inhibitor therapy has value in this setting. METHODS: The randomized multicenter phase II PACE trial enrolled patients with hormone receptor-positive/HER2- MBC whose disease had progressed on previous CDK4/6i and aromatase inhibitor (AI) therapy. Patients were randomly assigned 1:2:1 to receive fulvestrant (F), fulvestrant plus palbociclib (F + P), or fulvestrant plus palbociclib and avelumab (F + P + A). The primary end point was investigator-assessed progression-free survival (PFS) in patients treated with F versus F + P. RESULTS: Overall, 220 patients were randomly assigned between September 2017 and February 2022. The median age was 57 years (range, 25-83 years). Most patients were postmenopausal (80.9%), and 40% were originally diagnosed with de novo MBC. Palbociclib was the most common previous CDK4/6i (90.9%). The median PFS was 4.8 months on F and 4.6 months on F + P (hazard ratio [HR], 1.11 [90% CI, 0.79 to 1.55]; P = .62). The median PFS on F + P + A was 8.1 months (HR v F, 0.75 [90% CI, 0.50 to 1.12]; P = .23). The difference in PFS with F + P and F + P + A versus F was greater among patients with baseline ESR1 and PIK3CA alterations. CONCLUSION: The addition of palbociclib to fulvestrant did not improve PFS versus fulvestrant alone among patients with hormone receptor-positive/HER2- MBC whose disease had progressed on a previous CDK4/6i plus AI. The increased PFS seen with the addition of avelumab warrants further investigation in this patient population.

'ADVANCE' (a pilot trial) ADjuVANt chemotherapy in the elderly: Developing and evaluating lower-toxicity chemotherapy options for older patients with breast cancer.

INTRODUCTION: Older adults with breast cancer receiving neo/adjuvant chemotherapy are at high risk for poor outcomes and are underrepresented in clinical trials. The ADVANCE (ADjuVANt Chemotherapy in the Elderly) trial evaluated the feasibility of two neo/adjuvant chemotherapy regimens in parallel-enrolling cohorts of older patients with human epidermal growth factor receptor 2-negative breast cancer: cohort 1-triple-negative; cohort 2-hormone receptor-positive. MATERIALS AND METHODS: Adults age ≥ 70 years with stage I-III breast cancer warranting neo/adjuvant chemotherapy were enrolled. Cohort 1 received weekly carboplatin (area under the curve 2) and weekly paclitaxel 80 mg/m2 for twelve weeks; cohort 2 received weekly paclitaxel 80 mg/m2 plus every-three-weekly cyclophosphamide 600 mg/m2 over twelve weeks. The primary study endpoint was feasibility, defined as ≥80% of patients receiving ≥80% of intended weeks/doses of therapy. All dose modifications were applied per clinician discretion. RESULTS: Forty women (n = 20 per cohort) were enrolled from March 25, 2019 through August 3, 2020 from three centers; 45% and 35% of patients in cohorts 1 and 2 were age > 75, respectively. Neither cohort achieved targeted thresholds for feasibility. In cohort 1, eight (40.0%) met feasibility (95% confidence interval [CI] = 19.1-63.9%), while ten (50.0%) met feasibility in cohort 2 (95% CI = 27.2-72.8). Neutropenia was the most common grade 3-4 toxicity (cohort 1-65%, cohort 2-55%). In cohort 1, 80% and 85% required ≥1 dose holds of carboplatin and/or paclitaxel, respectively. In cohort 2, 10% required dose hold(s) for cyclophosphamide and/or 65% for paclitaxel. DISCUSSION: In this pragmatic pilot examining chemotherapy regimens in older adults with breast cancer, neither regimen met target goals for feasibility. Developing efficacious and tolerable regimens for older patients with breast cancer who need chemotherapy remains an important goal. CLINICALTRIALS: gov Identifier: NCT03858322.

Impact of Neoadjuvant Paclitaxel/Trastuzumab/Pertuzumab on Breast Tumor Downsizing for Patients with HER2+ Breast Cancer: Single-Arm Prospective Clinical Trial.

BACKGROUND: The impact of abbreviated neoadjuvant regimens for HER2+ breast cancer on rates of breast conservation therapy (BCT) is unclear. We aimed to determine BCT rates in a single-arm prospective trial of neoadjuvant paclitaxel/trastuzumab/pertuzumab (THP) in patients with stage II or III HER2+ breast cancer. STUDY DESIGN: BCT eligibility was prospectively recorded before and after THP. Pre- and posttreatment mammogram and breast ultrasound were required; breast MRI was encouraged. Patients with a large tumor to breast size ratio were eligible for downsizing. Multifocal/multicentric tumors, extensive calcifications, and contraindications to radiation were considered BCT contraindications. RESULTS: Overall, 92 patients who received neoadjuvant THP on trial were included. At presentation, 39 (42.4%) were considered eligible for BCT and 53 (57.6%) were not. BCT-eligible patients were older (median 54 vs 47 years, respectively; p = 0.006) and had smaller tumors by palpation (median 2.5 vs 3 cm, respectively; p = 0.004). Of 53 BCT-ineligible patients, 28 were candidates for tumor downsizing, whereas 25 had contraindications to BCT. Overall, 51 (55.4%) patients underwent BCT. Of the 28 patients who were candidates for downsizing, 22 (78.6%) became BCT-eligible after THP and 18 of 22 (81.8%) underwent BCT. In total, 44 of 92 (47.8%) patients experienced breast pathologic complete response (ypT0), including 11 of 25 (44.0%) patients with BCT contraindications at presentation. CONCLUSIONS: De-escalated neoadjuvant systemic therapy led to high BCT rates in this cohort. The impact of de-escalated systemic therapy on local therapy and outcomes in early stage HER2+ breast cancer warrants further investigation.

Clonal hematopoiesis in older patients with breast cancer receiving chemotherapy.

BACKGROUND: The expansion of hematopoietic stem cells carrying recurrent somatic mutations, termed clonal hematopoiesis (CH), is common in elderly individuals and is associated with increased risk of myeloid malignancy and all-cause mortality. Though chemotherapy is a known risk factor for developing CH, how myelosuppressive therapies affect the short-term dynamics of CH remains incompletely understood. Most studies have been limited by retrospective design, heterogeneous patient populations, varied techniques to identifying CH, and analysis of single timepoints. METHODS: We examined serial samples from 40 older women with triple-negative or hormone receptor-positive breast cancer treated on the prospective ADjuVANt Chemotherapy in the Elderly trial to evaluate the prevalence and dynamics of CH at baseline and throughout chemotherapy (6 and 12 weeks). RESULTS: CH was detected in 44% of patients at baseline and in 53% at any timepoint. Baseline patient characteristics were not associated with CH. Over the course of treatment, mutations exhibited a variety of dynamics, including emergence, expansion, contraction, and disappearance. All mutations in TP53 (n = 3) and PPM1D (n = 4), genes that regulate the DNA damage response, either became detectable or expanded over the course of treatment. Neutropenia was more common in patients with CH, particularly when the mutations became detectable during treatment, and CH was significantly associated with cyclophosphamide dose reductions and holds (P = .02). CONCLUSIONS: Our study shows that CH is common, dynamic, and of potential clinical significance in this population. Our results should stimulate larger efforts to understand the biological and clinical importance of CH in solid tumor malignancies. TRIAL REGISTRATION: ClinicalTrials.gov (https://clinicaltrials.gov/ct2/show/NCT03858322). Clinical trial registration number: NCT03858322.

A prospective trial of treatment de-escalation following neoadjuvant paclitaxel/trastuzumab/pertuzumab in HER2-positive breast cancer.

De-escalating adjuvant therapy following pathologic complete response (pCR) to an abbreviated neoadjuvant regimen in human epidermal growth factor receptor 2-positive (HER2+) breast cancer is the focus of international research efforts. However, the feasibility of this approach and its appeal to patients and providers had not been formally investigated. We aimed to assess adherence to de-escalated adjuvant antibody doublet therapy (trastuzumab and pertuzumab [HP], without chemotherapy) among patients with pCR following neoadjuvant paclitaxel/HP (THP). In this single-arm prospective trial, patients with treatment-naïve stage II-III HER2+ breast cancer received neoadjuvant weekly paclitaxel ×12 and HP every 3 weeks ×4. The primary endpoint was receipt of adjuvant non-HER2-directed cytotoxic chemotherapy. Ninety-eight patients received ≥1 dose of THP on study. Patients had median age of 50 years, 86% had stage II tumors, and 34% were hormone receptor-negative. Five patients had incomplete clinical response following THP and received doxorubicin and cyclophosphamide before surgery; they were classified as non-pCR and censored from further analyses. The overall pCR rate was 56.7%. Among patients with pCR, the adherence rate to de-escalated antibody-only therapy (HP) was 98.2% (95% CI 90.3-100.0%), and the primary feasibility endpoint was reached. The majority of patients felt positive or neutral about their adjuvant treatment plans. With brief follow-up (median 19.1 months), there were no breast cancer recurrences. De-escalation of adjuvant chemotherapy among patients who experience pCR in early-stage HER2+ breast cancer is a practicable approach for both patients and physicians. Planned and ongoing prospective trials will determine the long-term efficacy of this approach.Trial registration clinicaltrials.gov, NCT03716180, https://clinicaltrials.gov/ct2/show/NCT03716180 .

Accuracy of screening mammography in older women.

OBJECTIVE: The objective of our study was to determine the accuracy and cancer detection rate of screening mammography in women as they age. MATERIALS AND METHODS: Using data from the Vermont Breast Cancer Surveillance System (1996-2006), we calculated the sensitivity, specificity, positive predictive value, negative predictive value, and cancer detection rate by decade of age for 403,448 mammograms of 96,193 women 50-101 years old. Confounding variables were assessed using logistic regression analysis. RESULTS: The sensitivity of screening mammography increased from 77.3% for the 50- to 59-year-old group to 93.8% for the 90- to 101-year-old group (p = 0.015). Specificity increased from 98.7% to 98.8% at age 50-59 compared with age 90-101 (p < 0.001), respectively. The cancer detection rate increased from 3.7 cases per 1000 mammograms at age 50-59 to 14.4 cases per 1000 mammograms at age 90-101 (p < 0.001). The prevalence of breast cancer increased from 4.8% to 15.4% across age groups (p < 0.001) as did the positive predictive value from 22.2% to 55.6% (p <0.001). There was no evidence of confounding by body mass index, breast density, or other factors. Tumors were more likely to be small, hormone receptor-positive, and more invasive as women aged. Accuracy parameters were all associated with age without evidence of confounding by regression analysis. CONCLUSION: Screening mammography is more accurate in older women than in younger women, suggesting that it may be of value in assessing women in all age groups. These data do not address the impact of mammography screening on mortality or breast cancer outcomes.

From Beethoven to Beyoncé: Do Changing Aesthetic Cultures Amount to "Cumulative Cultural Evolution?"

Culture can be defined as "group typical behaviour patterns shared by members of a community that rely on socially learned and transmitted information" (Laland and Hoppitt, 2003, p. 151). Once thought to be a distinguishing characteristic of humans relative to other animals (Dean et al., 2014) it is now generally accepted to exist more widely, with especially abundant evidence in non-human primates, cetaceans, and birds (Rendell and Whitehead, 2001; Aplin, 2019; Whiten, 2021). More recently, cumulative cultural evolution (CCE) has taken on this distinguishing role (Henrich, 2015; Laland, 2018). CCE, it is argued, allows humans, uniquely, to ratchet up the complexity or efficiency of cultural traits over time. This "ratchet effect" (Tomasello, 1994) gives the capacity to accumulate beneficial modifications over time beyond the capacities of a single individual (Sasaki and Biro, 2017). Mesoudi and Thornton (2018) define a core set of criteria for identifying CCE in humans and non-human animals that places emphasis on some performance measure of traits increasing over time. They suggest this emphasis is also pertinent to cultural products in the aesthetic domain, but is this the case? Music, art and dance evolve over time (Savage, 2019), but can we say they gain beneficial modifications that increase their aesthetic value? Here we bring together perspectives from philosophy, musicology and biology to build a conceptual analysis of this question. We summarise current thinking on cumulative culture and aesthetics across fields to determine how aesthetic culture fits into the concept of CCE. We argue that this concept is problematic to reconcile with dominant views of aesthetics in philosophical analysis and struggles to characterise aesthetic cultures that evolve over time. We suggest that a tension arises from fundamental differences between cultural evolution in aesthetic and technological domains. Furthermore, this tension contributes to current debates between reconstructive and preservative theories of cultural evolution.

Effect of Eribulin With or Without Pembrolizumab on Progression-Free Survival for Patients With Hormone Receptor-Positive, ERBB2-Negative Metastatic Breast Cancer: A Randomized Clinical Trial.

Importance: Prior studies have shown that only a small proportion of patients with hormone receptor (HR)-positive metastatic breast cancer (MBC) experience benefit from programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1) inhibitors given as monotherapy. There are data suggesting that activity may be greater with combination strategies. Objective: To compare the efficacy of eribulin plus pembrolizumab vs eribulin alone in patients with HR-positive, ERBB2 (formerly HER2)-negative MBC. Design, Setting, and Participants: Multicenter phase 2 randomized clinical trial of patients with HR-positive, ERBB2-negative MBC who had received 2 or more lines of hormonal therapy and 0 to 2 lines of chemotherapy. Interventions: Patients were randomized 1:1 to eribulin, 1.4 mg/m2 intravenously, on days 1 and 8 plus pembrolizumab, 200 mg/m2 intravenously, on day 1 of a 21-day cycle or eribulin alone. At time of progression, patients in the eribulin monotherapy arm could cross over and receive pembrolizumab monotherapy. Main Outcomes and Measures: The primary end point was progression-free survival (PFS). Secondary end points were objective response rate (ORR) and overall survival (OS). Exploratory analyses assessed the association between PFS and PD-L1 status, tumor-infiltrating lymphocytes (TILs), tumor mutational burden (TMB), and genomic alterations. Results: Eighty-eight patients started protocol therapy; the median (range) age was 57 (30-76) years, median (range) number of prior lines of chemotherapy was 1 (0-2), and median (range) number of prior lines of hormonal therapy was 2 (0-5). Median follow-up was 10.5 (95% CI, 0.4-22.8) months. Median PFS and ORR were not different between the 2 groups (PFS, 4.1 vs 4.2 months; hazard ratio, 0.80; 95% CI, 0.50-1.26; P = .33; ORR, 27% vs 34%, respectively; P = .49). Fourteen patients started crossover treatment with pembrolizumab; 1 patient experienced stable disease. All-cause adverse events occurred in all patients (grade ≥3, 65%) including 2 treatment-related deaths in the combination group, both from immune-related colitis in the setting of sepsis, attributed to both drugs. The PD-L1 22C3 assay was performed on archival tumor samples in 65 patients: 24 (37%) had PD-L1-positive tumors. Analysis indicated that PD-L1 status, TILs, TMB, and genomic alterations were not associated with PFS. Conclusions and Relevance: In this randomized clinical trial of patients with HR-positive, ERBB2-negative MBC, the addition of pembrolizumab to eribulin did not improve PFS, ORR, or OS compared with eribulin alone in either the intention-to-treat or PD-L1-positive populations. Further efforts to explore the benefits of adding checkpoint inhibition to chemotherapy among less heavily pretreated patients are needed. Trial Registration: ClinicalTrials.gov Identifier: NCT03051659.

Avoiding Peg-Filgrastim Prophylaxis During the Paclitaxel Portion of the Dose-Dense Doxorubicin-Cyclophosphamide and Paclitaxel Regimen: A Prospective Study.

PURPOSE: The use of growth factors adds considerable expense and some toxicity to adjuvant breast cancer chemotherapy. We tested the feasibility and safety of omitting routine peg-filgrastim use during the paclitaxel portion of the dose-dense doxorubicin-cyclophosphamide-paclitaxel regimen. PATIENTS AND METHODS: This was a prospective, single-arm study in which patients 18 to 65 years of age who completed 4 cycles of dose-dense doxorubicin-cyclophosphamide for stage I-III breast cancer received paclitaxel 175 mg/m2 every 2 weeks. Peg-filgrastim was administered after paclitaxel only if patients had had febrile neutropenia in a prior cycle or at investigator discretion if patients had infections or treatment delays of > 1 week. Once a patient received peg-filgrastim, it was administered in all future cycles. The primary end point was the rate of paclitaxel completion within 7 weeks from cycle 1 day 1 to cycle 4 day 1. If ≥ 100 out of 125 patients completed 4 cycles of paclitaxel without dose delay, the regimen would be considered feasible. RESULTS: The enrollment goal of 125 patients was met. Median age was 46 years (range, 21-65 years), and 112 patients (90% [95% CI, 83% to 94%]) completed dose-dense paclitaxel within 7 weeks. Omission of peg-filgrastim was not causally related to noncompletion of paclitaxel in any patients. The most common reasons for dose reduction or delays were nonhematologic. One patient experienced febrile neutropenia but was able to complete paclitaxel on time. Eight patients (6.4%) received peg-filgrastim during the trial. Overall, peg-filgrastim was administered in only 4.3% of paclitaxel cycles. CONCLUSION: Omission of routine peg-filgrastim during dose-dense paclitaxel according to a prespecified algorithm seems to be safe and feasible and was associated with a 95.7% reduction in the use of peg-filgrastim relative to the current standard of care.

Similar outcomes in Asian and Western patients with diffuse large B-cell lymphoma treated with R-CHOP.

BACKGROUND: Little is known on racial differences in patients with diffuse large B-cell lymphoma (DLBCL). The aim of this retrospective study is to compare characteristics, prognostic factors and outcomes of Asian and Western patients with DLBCL treated with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP). METHODS: Patient-level data was collected from 8 centers. All patients were diagnosed with DLBCL and treated with R-CHOP. Patients were divided into Asian and Western, according to the country of report. Comparisons and univariate/multivariate survival analyses were performed. RESULTS: 712 patients, 455 Asian and 257 Western patients were included. Westerners were more likely to present with elevated LDH (64% vs. 48%, p<0.01) and advanced stage (58% vs. 49%, p<0.01). After a median follow-up of 36 months, there was no difference in progression-free (PFS; p=0.33) or overall survival (OS; p=0.69). There were no PFS or OS differences between races when evaluating separately each age-adjusted International Prognostic Index category. In the multivariate analyses, performance status and stage were associated with PFS and OS in both races. CONCLUSIONS: There are no differences in prognostic factors, PFS and OS between Asian and Western patients with DLBCL treated with R-CHOP.

Gastrin regulates the heparin-binding epidermal-like growth factor promoter via a PKC/EGFR-dependent mechanism.

Gastrin is a known growth/differentiation factor for the gastric mucosa. Its effects are likely mediated by the induction of heparin-binding epidermal-like growth factor (HB-EGF), a member of the EGF family of growth factors that is expressed by gastric parietal cells. In this study, we investigated the regulation of the HB-EGF promoter by gastrin in a human gastric cancer cell line. Serial human HB-EGF promoter-luciferase reporter deletion constructs and heterologous promoter constructs were transfected into AGS-E cells and stimulated with gastrin (10(-7) M) with or without various signal transduction inhibitors. EMSA were also performed. Gastrin stimulation resulted in a fivefold increase in HB-EGF-luciferase activity. The cis-acting element mediating gastrin responsiveness was mapped to the -69 to -58 region of the HB-EGF promoter. Gastrin stimulation was PKC dependent and at least partially mediated by activation of the EGF receptor.

PACAP and gastrin regulate the histidine decarboxylase promoter via distinct mechanisms.

The enterochromaffin-like (ECL) cell controls gastric acid secretion via histamine, generated by l-histidine decarboxylase (HDC). HDC expression is regulated by gastrin. However, gastrin is not alone in controlling ECL cell function. For example, the neural peptide pituitary adenylate cyclase-activating polypeptide (PACAP) also increases ECL cell proliferation. To investigate a potential role of PACAP in regulating HDC expression, we generated a series of HDC promoter-luciferase reporter constructs and transiently transfected them into PC12 cells (stably expressing the gastrin-CCK-2 receptor). We found that PACAP regulates HDC promoter activity. This is temporally biphasic, involving both adenyl cyclase and phospholipase C-dependent pathways. Deletional analysis, block mutation, and EMSA demonstrated a PACAP-response element at -177 to -170, wholly necessary for the effects of PACAP and discrete from known gastrin-responsive elements. Discrete neural and endocrine pathways regulate ECL cells through different patterns of postreceptor signaling and promoter activation, which may be appropriate to their functions in vivo.