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BACKGROUND: Therapies for relapsed/refractory acute myeloid leukemia remain limited and outcomes poor, especially amongst patients who are ineligible for cytotoxic chemotherapy or targeted therapies. PATIENTS AND METHODS: This phase 1b trial evaluated venetoclax, a B-cell lymphoma-2 (BCL-2) inhibitor, plus cobimetinib, a MEK1/2 inhibitor, in patients with relapsed/refractory acute myeloid leukemia, ineligible for cytotoxic chemotherapy. Two-dimensional dose-escalation was performed for venetoclax dosed daily, and for cobimetinib dosed on days 1-21 of each 28-day cycle. RESULTS: Thirty patients (median [range] age: 71.5 years [60-84]) received venetoclax-cobimetinib. The most common adverse events (AEs; in ≥40.0% of patients) were diarrhea (80.0%), nausea (60.0%), vomiting (40.0%), febrile neutropenia (40.0%), and fatigue (40.0%). Overall, 66.7% and 23.3% of patients experienced AEs leading to dose modification/interruption or treatment withdrawal, respectively. The composite complete remission (CRc) rate (complete remission [CR]â¯+â¯CR with incomplete blood count recoveryâ¯+â¯CR with incomplete platelet recovery) was 15.6%; antileukemic response rate (CRcâ¯+â¯morphologic leukemia-free state/partial remission) was 18.8%. For the recommended phase 2 dose (venetoclax: 600 mg; cobimetinib: 40 mg), CRc and antileukemic response rates were both 12.5%. Failure to achieve an antileukemic response was associated with elevated baseline phosphorylated ERK and MCL-1 levels, but not BCL-xL. Baseline mutations in ≥1 signaling gene or TP53 were noted in nonresponders and emerged on treatment. Pharmacodynamic biomarkers revealed inconsistent, transient inhibition of the mitogen-activated protein kinase (MAPK) pathway. CONCLUSION: Venetoclax-cobimetinib showed limited preliminary efficacy similar to single-agent venetoclax, but with added toxicity. Our findings will inform future trials of BCL-2/MAPK pathway inhibitor combinations.
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Protocolos de Quimioterapia Combinada Antineoplásica , Azetidinas , Compostos Bicíclicos Heterocíclicos com Pontes , Leucemia Mieloide Aguda , Piperidinas , Sulfonamidas , Humanos , Compostos Bicíclicos Heterocíclicos com Pontes/uso terapêutico , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Compostos Bicíclicos Heterocíclicos com Pontes/administração & dosagem , Sulfonamidas/farmacologia , Sulfonamidas/uso terapêutico , Sulfonamidas/administração & dosagem , Idoso , Masculino , Feminino , Pessoa de Meia-Idade , Azetidinas/uso terapêutico , Azetidinas/farmacologia , Azetidinas/administração & dosagem , Piperidinas/uso terapêutico , Piperidinas/farmacologia , Idoso de 80 Anos ou mais , Leucemia Mieloide Aguda/tratamento farmacológico , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Resultado do Tratamento , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacosRESUMO
Inhibiting individual histone deacetylase (HDAC) is emerging as well-tolerated anticancer strategy compared with pan-HDAC inhibitors. Through preclinical studies, we demonstrated that the sensitivity to the leading HDAC6 inhibitor (HDAC6i) ricolinstat can be predicted by a computational network-based algorithm (HDAC6 score). Analysis of ~3,000 human breast cancers (BCs) showed that ~30% of them could benefice from HDAC6i therapy. Thus, we designed a phase 1b dose-escalation clinical trial to evaluate the activity of ricolinostat plus nab-paclitaxel in patients with metastatic BC (MBC) (NCT02632071). Study results showed that the two agents can be safely combined, that clinical activity is identified in patients with HR+/HER2- disease and that the HDAC6 score has potential as predictive biomarker. Analysis of other tumor types also identified multiple cohorts with predicted sensitivity to HDAC6i's. Mechanistically, we have linked the anticancer activity of HDAC6i's to their ability to induce c-Myc hyperacetylation (ac-K148) promoting its proteasome-mediated degradation in sensitive cancer cells.
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Neoplasias da Mama , Humanos , Feminino , Desacetilase 6 de Histona/metabolismo , Neoplasias da Mama/tratamento farmacológico , Histona Desacetilases/metabolismo , Ácidos Hidroxâmicos/farmacologia , Ácidos Hidroxâmicos/uso terapêuticoRESUMO
This phase 1b trial (NCT02670044) evaluated venetoclax-idasanutlin in patients with relapsed/refractory (R/R) acute myeloid leukemia (AML) ineligible for cytotoxic chemotherapy. Two-dimensional dose escalation (DE, n = 50) was performed for venetoclax daily with idasanutlin on days 1 to 5 in 28-day cycles, followed by dosing schedule optimization (n = 6) to evaluate reduced venetoclax schedules (21-/14-day dosing). Common adverse events (occurring in ≥40% of patients) included diarrhea (87.3% of patients), nausea (74.5%), vomiting (52.7%), hypokalemia (50.9%), and febrile neutropenia (45.5%). During DE, across all doses, composite complete remission (CRc; CR + CR with incomplete blood count recovery + CR with incomplete platelet count recovery) rate was 26.0% and morphologic leukemia-free state (MLFS) rate was 12%. For anticipated recommended phase 2 doses (venetoclax 600 mg + idasanutlin 150 mg; venetoclax 600 mg + idasanutlin 200 mg), the combined CRc rate was 34.3% and the MLFS rate was 14.3%. Pretreatment IDH1/2 and RUNX1 mutations were associated with higher CRc rates (50.0% and 45.0%, respectively). CRc rate in patients with TP53 mutations was 20.0%, with responses noted among those with co-occurring IDH and RUNX1 mutations. In 12 out of 36 evaluable patients, 25 emergent TP53 mutations were observed; 22 were present at baseline with low TP53 variant allele frequency (median 0.0095% [range, 0.0006-0.4]). Venetoclax-idasanutlin showed manageable safety and encouraging efficacy in unfit patients with R/R AML. IDH1/2 and RUNX1 mutations were associated with venetoclax-idasanutlin sensitivity, even in some patients with co-occurring TP53 mutations; most emergent TP53 clones were preexisting. Our findings will aid ongoing/future trials of BCL-2/MDM2 inhibitor combinations. This trial was registered at www.clinicaltrials.gov as #NCT02670044.
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Antineoplásicos , Leucemia Mieloide Aguda , Humanos , Subunidade alfa 2 de Fator de Ligação ao Core , Leucemia Mieloide Aguda/tratamento farmacológico , Leucemia Mieloide Aguda/genética , Antineoplásicos/uso terapêutico , Compostos Bicíclicos Heterocíclicos com Pontes/efeitos adversos , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversosRESUMO
INTRODUCTION: Mitogen-activated protein kinase pathway mutations are present in >50% of patients with relapsed/refractory (R/R) multiple myeloma (MM). MEK inhibitors show limited single-agent activity in R/R MM; combination with B-cell lymphoma-2 (BCL-2) and programmed death-ligand 1 inhibition may improve efficacy. This phase Ib/II trial (NCT03312530) evaluated safety and efficacy of cobimetinib (cobi) alone and in combination with venetoclax (ven) with/without atezolizumab (atezo) in patients with R/R MM. PATIENTS AND METHODS: Forty-nine patients were randomized 1:2:2 to cobi 60 mg/day on days 1-21 (nâ¯=â¯6), cobi 40 mg/day on days 1-21â¯+â¯ven 800 mg/day on days 1-28 with/without atezo 840 mg on days 1 and 15 of 28-day cycles (cobi-ven, nâ¯=â¯22; cobi-ven-atezo, nâ¯=â¯21). Safety run-in cohorts evaluated cobi-ven and cobi-ven-atezo dose levels. RESULTS: Any-grade common adverse events (AEs) with cobi, cobi-ven, and cobi-ven-atezo, respectively, included diarrhea (33.3%, 81.8%, 90.5%) and nausea (16.7%, 50.0%, 66.7%); common grade ≥3 AEs included anemia (0%, 22.7%, 23.8%), neutropenia (0%, 13.6%, 38.1%), and thrombocytopenia (0%, 18.2%, 23.8%). The overall response rate for all-comers was 0% (cobi), 27.3% (cobi-ven), and 28.6% (cobi-ven-atezo), and 0%, 50.0%, and 100%, respectively, in patients with t(11;14)+. Biomarker analysis demonstrated non-t(11;14) patient selection with NRAS/KRAS/BRAF mutation or high BCL-2/BCL-2-L1 ratio (>52% of the study population) could enrich for responders to the cobi-ven combination. CONCLUSIONS: Cobi-ven and cobi-ven-atezo demonstrated manageable safety with moderate activity in all-comers, and higher activity in patients with t(11;14)+ MM, supporting a biomarker-driven approach for ven in MM.
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Mieloma Múltiplo , Humanos , Mieloma Múltiplo/tratamento farmacológico , Mieloma Múltiplo/etiologia , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Compostos Bicíclicos Heterocíclicos com Pontes/efeitos adversos , Proteínas Proto-Oncogênicas c-bcl-2RESUMO
BACKGROUND: Treatment with venetoclax + hypomethylating agents (HMAs) is standard-of-care for newly diagnosed (ND) patients with acute myeloid leukemia (AML) aged ≥75 years, or with comorbidities precluding intensive chemotherapy. We describe real-world venetoclax + HMA treatment practices and outcomes in patients with ND AML in the US. PATIENTS AND METHODS: This retrospective cohort study used an electronic health record-derived, US nationwide, de-identified database, and included adults with ND AML, initiating venetoclax + HMA treatment ≤30 days from diagnosis (June 1, 2018-January 31, 2020). Venetoclax treatment variables included dosing information, schedule modifications, and drug-drug interactions. The median venetoclax + HMA treatment duration and overall survival (OS) from venetoclax initiation to discontinuation, death, or end of follow-up (August 31, 2020) were examined by Kaplan-Meier analyses. RESULTS: Overall, 169 patients were included. The median age at diagnosis was 77 years; 85.2% of patients were treated in community practice. Ninety-five of 169 patients (56.2%) had evaluable bone marrow response data following the start of treatment; 53.7% were assessed approximately at the end of cycle 1. Following the first treatment cycle, treatment schedule modifications were recorded in 101 patients and dose changes in 56, primarily due to toxicity. The median treatment duration was 5.2 months; the median OS was 8.6 months (median follow-up was 7.2 months). Venetoclax dose changes did not modify efficacy outcomes, but longer median OS was associated with venetoclax treatment schedule modifications (P = .02). CONCLUSIONS: This study reflects early real-world experience with venetoclax + HMAs in a predominantly community setting and emphasizes the importance of appropriate venetoclax management in optimizing patient outcomes.
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Compostos Bicíclicos Heterocíclicos com Pontes , Leucemia Mieloide Aguda , Adulto , Humanos , Idoso , Decitabina/efeitos adversos , Estudos Retrospectivos , Compostos Bicíclicos Heterocíclicos com Pontes/uso terapêutico , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversosRESUMO
BACKGROUND: Ovarian suppression from chemotherapy results in bone loss in premenopausal women with breast cancer (BC). Less is known about bone microarchitecture changes. We used high-resolution peripheral quantitative computed tomography (HR-pQCT) to measure volumetric bone density and trabecular and cortical microarchitecture in this population. MATERIALS AND METHODS: The primary endpoint was to assess changes in cortical thickness and trabecular bone density by HR-pQCT. Premenopausal women with stage I to III BC undergoing adjuvant chemotherapy underwent a bone mineral density (BMD) dual energy x-ray absorptiometry scan and HR-pQCT (voxel size, 82 microns) at baseline and 12 months. Paired t tests were used to observe the change over time in bone microarchitecture and areal and volumetric density. RESULTS: Eighteen patients were evaluated, of which 12 patients had baseline and matched 12-month imaging. The mean age was 45.2 years (range, 35-51 years), 17 (94%) patients had hormone receptor-positive BC, and 16 (89%) initiated tamoxifen. At 12 months, there was a significant decrease in femoral neck (P < .05) and lumbar spine and total hip (P < .01) BMD. Changes detected by HR-pQCT at 12 months included significant decreases in cortical thickness and area at the tibia (P < .05), and total and cortical volumetric BMD at the radius and tibia (P < .01), as well as an increase in tibial trabecular area (P < .05). CONCLUSION: Premenopausal women undergoing chemotherapy experience BMD decline and trabecular and cortical bone microarchitecture deterioration. In this population, future efforts should focus on therapy-induced bone loss and optimizing bone density-related management.
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Densidade Óssea/efeitos dos fármacos , Neoplasias da Mama/terapia , Osso Esponjoso/efeitos dos fármacos , Osso Cortical/efeitos dos fármacos , Osteoporose/diagnóstico , Absorciometria de Fóton , Adulto , Osso Esponjoso/diagnóstico por imagem , Osso Esponjoso/fisiopatologia , Quimioterapia Adjuvante/efeitos adversos , Quimioterapia Adjuvante/métodos , Osso Cortical/diagnóstico por imagem , Osso Cortical/fisiopatologia , Feminino , Colo do Fêmur/diagnóstico por imagem , Colo do Fêmur/efeitos dos fármacos , Articulação do Quadril/diagnóstico por imagem , Articulação do Quadril/efeitos dos fármacos , Humanos , Vértebras Lombares/diagnóstico por imagem , Vértebras Lombares/efeitos dos fármacos , Mastectomia , Pessoa de Meia-Idade , Osteoporose/induzido quimicamente , Pré-Menopausa , Estudos Prospectivos , Rádio (Anatomia)/diagnóstico por imagem , Rádio (Anatomia)/efeitos dos fármacos , Tíbia/diagnóstico por imagem , Tíbia/efeitos dos fármacos , Tomografia Computadorizada por Raios XRESUMO
PURPOSE: Intraoperative radiation therapy (IORT) as a form of accelerated partial breast irradiation (APBI) is controversial given the limited evidence to support its efficacy. However, it remains an attractive option for low-risk patients with ductal carcinoma in situ (DCIS), who derive a small absolute benefit in local control with standard whole breast irradiation (WBI). We examine how the American Society for Therapeutic Radiation Oncology (ASTRO) APBI consensus guidelines (CG) may be applied to the preoperative selection of patients with DCIS for IORT and determine treatment outcomes by CG group. METHODS AND MATERIALS: We identified patients with biopsy-proven pure DCIS enrolled in an institutional prospective registry IORT database using the Zeiss Intrabeam® device between September 2013 and February 2017. Based on available preoperative clinicopathologic information, patients were deemed suitable, cautionary, or unsuitable for IORT according to the ASTRO CG. Change in CG group based on final pathologic diagnosis was determined, and additional therapy was recommended for unsuitable patients. Outcome in terms of ipsilateral breast tumor recurrence was determined. RESULTS: A total of 61 DCIS lesions in 60 patients were treated with IORT. Preoperatively, 21 patients (35%) were suitable and 36 (59%) were cautionary. Four (6%) were unsuitable because of lesion size but declined WBI. Final pathologic diagnosis changed the CG grouping of 10 patients (16%) because of either occult high-grade disease in 2 (3%) or close/positive margins in 8 (13%). Ultimately 12 patients total were considered unsuitable, of whom 8 (66%) accepted additional WBI after IORT. At a median follow-up of 2.2 years, ipsilateral breast tumor recurrence was identified among 2 suitable, 1 cautionary, and no unsuitable patients. CONCLUSION: Further investigation is necessary to refine selection of patients with DCIS who may be optimally treated with IORT alone. High acceptance of additional therapy among unsuitable patients resulted in excellent outcomes. The use of biomarkers in addition to traditional clinical and pathologic factors may help to better select patients for IORT.
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PURPOSE: Breast cancer (BC) is a risk factor for major depressive disorder (MDD), yet little research has tested the efficacy of different psychotherapies for depressed women with BC. This study, the largest to date, compared outcomes of three evidence-based, 12-week therapies in treating major depressive disorder among women with breast cancer. METHODS: This randomized trial compared interpersonal psychotherapy (IPT), problem solving therapy (PST), and brief supportive psychotherapy (BSP). Conducted at the outpatient clinic of the New York State Psychiatric Institute/Columbia University, the trial offered bilingual treatment by treatment-specific psychotherapists supervised by treatment experts. The primary outcome was change in the Hamilton Depression Rating Scale (HAM-D) at 12 weeks. Secondary outcomes included other validated patient-reported outcomes for depression and quality of life. RESULTS: Of 179 women with breast cancer screening positive for depression at the Columbia Cancer Center, 134 eligible patients signed informed treatment consent. Half of patients were Hispanic and economically disadvantaged. Most women had stage I (35.2%) or II (36.9%) BC; 9% had stage IV. The three brief psychotherapies showed similar improvements on the HAM-D, with large pre-post effect sizes (d ~ 1.0); a priori defined response rates were 35% for IPT, 50% for PST and 31% for BSP, and remission rates 25%, 30% and 27%, respectively. The three treatments also showed similar improvements in the Quality of Life Enjoyment and Satisfaction Questionnaire. Dropout was high, ranging from 37 to 52% across treatments. Predictors of dropout included having < 16 years of education and annual family income < $20,000. CONCLUSIONS: Among patients who completed treatment, all three psychotherapies were associated with similar, meaningful improvements in depression. Physical distance between the oncology and psychiatric treatment sites might have contributed to high dropout. This study suggests various psychotherapy approaches may benefit patients with breast cancer and major depression.
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Neoplasias da Mama/psicologia , Transtorno Depressivo Maior/terapia , Psicoterapia/métodos , Qualidade de Vida , Adulto , Idoso , Idoso de 80 Anos ou mais , Transtorno Depressivo Maior/diagnóstico , Transtorno Depressivo Maior/psicologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Escalas de Graduação Psiquiátrica , Resultado do TratamentoRESUMO
Normalization of fluorodeoxyglucose positron emission tomography (FDG PET) imaging prior to high-dose therapy and autologous stem cell transplantation (ASCT) improves outcomes in relapsed and refractory (RR) Hodgkin lymphoma (HL), but many patients refractory to platinum-based salvage regimens are unable to achieve this goal. We therefore investigated whether brentuximab vedotin (BV) could normalize FDG PET in platinum-refractory HL prior to ASCT. Fifteen consecutive patients with RR HL and FDG PET positive disease after platinum-based salvage therapy were treated with a median of 4 cycles of BV. Normalization of FDG PET (Deauville ≤2) occurred in 8/15 (53%) patients but was only observed in patients that had achieved partial remission or stable disease after platinum-based salvage therapy. All patients eventually proceeded to ASCT, regardless of FDG PET status. Our data suggest that BV can normalize FDG PET in a subset of patients with platinum-refractory HL prior to ASCT.
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Fluordesoxiglucose F18/uso terapêutico , Doença de Hodgkin/tratamento farmacológico , Imunoconjugados/uso terapêutico , Platina/metabolismo , Tomografia por Emissão de Pósitrons/métodos , Adolescente , Adulto , Brentuximab Vedotin , Feminino , Doença de Hodgkin/patologia , Humanos , Imunoconjugados/administração & dosagem , Masculino , Pessoa de Meia-Idade , Prognóstico , Resultado do Tratamento , Adulto JovemRESUMO
OBJECTIVE: To investigate the usefulness of point-of-care hand and wrist joint ultrasound (US) examination in patients with established rheumatoid arthritis (RA). METHODS: Fifty-one RA patients were evaluated using clinical disease activity measures and gray-scale and power Doppler (PD) US. Agreement between US and clinical findings and its impact on physicians' confidence and clinical decision were assessed. RESULTS: Agreement between intraarticular PD signal and joint swelling (JS) was moderate (82%; κ = 0.44). Agreement between PD signal and joint tenderness to palpation (TTP) was fair (75%; κ = 0.24). The greatest agreement between PD signal and clinical findings was seen in the 5th metacarpophalangeal (MCP) joint (96% JS, 88% TTP) and the poorest agreement was seen in the wrist (69% JS, 65% TTP) and 2nd (75% JS, 72% TTP) and 3rd (82% JS, 72% TTP) MCP joints. The presence of PD signal in nonswollen and/or nontender joints accounted for most of the disagreement in the wrists, while the opposite was true for the 2nd/3rd MCP joints. Agreement between sonographic synovial thickening and clinical findings was poor. Total sonographic synovial hypertrophy or PD score correlated significantly with physician-recorded, but not patient-recorded, clinical outcomes. US increased both physicians' confidence in their clinical decision (P < 0.0005, irrespective of Clinical Disease Activity Index score) and patients' confidence in physicians' medical decisions (88.4% of the cases). US modified biologic agent and/or disease-modifying antirheumatic drug (DMARD) use in 7 individual cases, but it did not affect the overall treatment plan (P > 0.15) or DMARD (P < 0.062) or biologic agent (P > 1.0) use in this group of RA patients. CONCLUSION: PD examination of the wrist and 2nd/3rd MCP joints might be feasible and clinically meaningful in evaluation of disease activity in patients with established RA. US examination of the hand/wrist joints in RA increases physicians' confidence in their clinical decision and can help to individualize DMARD and biologic agent use.
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Antirreumáticos/uso terapêutico , Artrite Reumatoide/diagnóstico por imagem , Artrite Reumatoide/tratamento farmacológico , Articulação da Mão/efeitos dos fármacos , Articulação da Mão/diagnóstico por imagem , Ultrassonografia Doppler , Articulação do Punho/efeitos dos fármacos , Articulação do Punho/diagnóstico por imagem , Adulto , Idoso , Idoso de 80 Anos ou mais , Artrite Reumatoide/patologia , Estudos de Casos e Controles , Técnicas de Apoio para a Decisão , Avaliação da Deficiência , Estudos de Viabilidade , Articulação da Mão/patologia , Humanos , Pessoa de Meia-Idade , Medição da Dor , Satisfação do Paciente , Seleção de Pacientes , Sistemas Automatizados de Assistência Junto ao Leito , Valor Preditivo dos Testes , Inquéritos e Questionários , Membrana Sinovial/diagnóstico por imagem , Membrana Sinovial/efeitos dos fármacos , Sinovite/diagnóstico por imagem , Sinovite/tratamento farmacológico , Resultado do Tratamento , Articulação do Punho/patologiaRESUMO
From breathing to walking, rhythmic movements encompass physiological processes important across the entire animal kingdom. It is thought by many that the generation of rhythmic behavior is operated by a central pattern generator (CPG) and does not require peripheral sensory input. Sensory feedback is, however, required to modify or coordinate the motor activity in response to the circumstances of actual movement. In contrast to this notion, we report here that sensory input is necessary for the generation of Drosophila larval locomotion, a form of rhythmic behavior. Blockage of all peripheral sensory inputs resulted in cessation of larval crawling. By conditionally silencing various subsets of larval peripheral sensory neurons, we identified the multiple dendritic (MD) neurons as the neurons essential for the generation of rhythmic peristaltic locomotion. By recording the locomotive motor activities, we further demonstrate that removal of MD neuron input disrupted rhythmic motor firing pattern in a way that prolonged the stereotyped segmental motor firing duration and prevented the propagation of posterior to anterior segmental motor firing. These findings reveal that MD sensory neuron input is a necessary component in the neural circuitry that generates larval locomotion.
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Comportamento Animal/fisiologia , Dendritos/fisiologia , Drosophila melanogaster/fisiologia , Locomoção , Neurônios Aferentes/fisiologia , Potenciais de Ação , Animais , Larva/fisiologia , Proteínas Recombinantes de Fusão/metabolismoRESUMO
Recent studies have established that the T1R3 receptor plays a central role in the taste-mediated ingestive response to sweeteners by mice. First, transgenic mice lacking the gene for T1R3, Tas1r3, show dramatically reduced lick responsiveness to most sweeteners. Second, strains with the taster allele of Tas1r3 (T strains) are more sensitive to low sweetener concentrations than strains with the nontaster allele (NT strains) and consume greater quantities of low- to midrange concentrations of sweeteners during 24-h tests. We asked how Tas1r3 polymorphisms influence the initial licking responses of four T strains (FVB/NJ, SWR/J, SM/J, and C57BL/6J) and four NT strains (BALB/cJ, 129P3/J, DBA/2J, and C3H/HeJ) to two sweeteners (sucrose and SC-45647, an artificial sweetener). We used the initial licking response as a measure of the taste-mediated ingestive response because its brief duration minimizes the potential contribution of nontaste factors (e.g., negative and positive postingestive feedback). Further, we used two complimentary short-term intake tests (the brief-access taste test and a novel 1-min preference test) to reduce the possibility that our findings were an epiphenomenon of a specific testing procedure. In both tests, the T strains were more responsive than the NT strains to low concentrations of each sweetener. At higher concentrations, however, there was considerable overlap between the T and NT strains. In fact, the initial licking response of several NT strains was more vigorous than (or equivalent to) that of several T strains. There was also considerable variation among strains with the same Tas1r3 allele. We conclude that Tas1r3 polymorphisms contribute to strain differences in initial lick responsiveness to low but not high concentrations of sweeteners.
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Polimorfismo Genético/fisiologia , Receptores de Superfície Celular/genética , Edulcorantes/farmacologia , Paladar/genética , Animais , Comportamento Animal/efeitos dos fármacos , Relação Dose-Resposta a Droga , Camundongos , Camundongos Transgênicos , Receptores de Superfície Celular/fisiologia , Receptores Acoplados a Proteínas G , Sacarose/farmacologiaRESUMO
We examined the necessity of alpha-gustducin, a G protein alpha-subunit expressed in taste cells, to taste-mediated licking responses of mice to sapid stimuli. To this end, we measured licking responses of alpha-gustducin knock-out (Gus-/-) mice and heterozygotic littermate controls (Gus+/-) to a variety of 'bitter', 'umami', 'sweet', 'salty' and 'sour' taste stimuli. All previous studies of how Gus-/- mice ingest taste stimuli have used long-term (i.e. 48 h) preference tests, which may be confounded by post-ingestive and/or experiential effects of the taste stimuli. We minimized these confounds by using a brief-access taste test, which quantifies immediate lick responses to extremely small volumes of sapid solutions. We found that deleting alpha-gustducin (i) dramatically reduced the aversiveness of a diverse range of 'bitter' taste stimuli; (ii) moderately decreased appetitive licking to low and intermediate concentrations of an 'umami' taste stimulus (monosodium glutamate in the presence of 100 microM amiloride), but virtually eliminated the normal aversion to high concentrations of the same taste stimulus; (iii) slightly decreased appetitive licking to 'sweet' taste stimuli; and (iv) modestly reduced the aversiveness of high, but not low or intermediate, concentrations of NaCl. There was no significant effect of deleting alpha-gustducin on licking responses to NH4Cl or HCl.