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Purpose: Adagrasib (MRTX849) is an oral, highly selective, small-molecule, covalent inhibitor of KRAS G12C . We report results from a phase I/IB study of adagrasib in non-small-cell lung cancer, colorectal cancer, and other solid tumors harboring the KRAS G12C mutation., Materials and Methods: Patients with advanced KRAS G12C -mutant solid tumors were treated with adagrasib 150 mg orally once daily, 300 mg once daily, 600 mg once daily, 1,200 mg once daily, or 600 mg orally twice a day using an accelerated titration design, which transitioned to a modified toxicity probability interval design when a predefined degree of toxicity was observed or target adagrasib exposure was achieved. Safety, pharmacokinetics, and clinical activity were evaluated., Results: Twenty-five patients were enrolled and received at least one dose of adagrasib. The recommended phase II dose (RP2D) was 600 mg twice a day on the basis of safety, tolerability, and observed pharmacokinetics properties. No maximum tolerated dose was formally defined. After a median follow-up of 19.6 months, eight of 15 patients (53.3%; 95% CI, 26.6 to 78.7) with RECIST-evaluable KRAS G12C -mutant non-small-cell lung cancer treated at 600 mg twice a day achieved a confirmed partial response. The median duration of response was 16.4 months (95% CI, 3.1 to not estimable). The median progression-free survival was 11.1 months (95% CI, 2.6 to not estimable). One of two patients with KRAS G12C -mutant colorectal cancer treated at 600 mg twice a day achieved a partial response (duration of response, 4.2 months). At the RP2D, the most common treatment-related adverse events (any grade) were nausea (80.0%), diarrhea (70.0%), vomiting (50.0%), and fatigue (45.0%). The most common grade 3-4 treatment-related adverse event was fatigue (15.0%)., Conclusion: Adagrasib 600 mg twice a day was well tolerated and exhibited antitumor activity in patients with advanced solid tumors harboring the KRAS G12C mutation., Competing Interests: Sai-Hong Ignatius OuStock and Other Ownership Interests: Turning Point Therapeutics, Elevation OncologyHonoraria: Pfizer, Roche Pharma AG, Genentech/Roche, ARIAD/Takeda, AstraZeneca, BeiGeneConsulting or Advisory Role: Pfizer, Roche/Genentech, AstraZeneca, Takeda, Janssen/JNJSpeakers' Bureau: AstraZeneca, Genentech/RocheResearch Funding: Pfizer (Inst), Roche Pharma AG (Inst), AstraZeneca/MedImmune (Inst), AstraZeneca (Inst), ARIAD (Inst), Revolution Medicines (Inst), Mirati Therapeutics (Inst), Janssen/JNJ (Inst) Pasi A. JänneStock and Other Ownership Interests: Gatekeeper Pharmaceuticals, Loxo OncologyConsulting or Advisory Role: Pfizer, Boehringer Ingelheim, AstraZeneca, Merrimack, Chugai Pharma, Roche/Genentech, LOXO, Mirati Therapeutics, Araxes Pharma, Ignyta, Lilly, Takeda, Novartis, Biocartis, Voronoi, SFJ Pharmaceuticals Group, Sanofi, Daiichi Sankyo, Silicon Therapeutics, Nuvalent, Inc, Eisai, Bayer, Syndax, AbbVie, Allorion Therapeutics, Accutar Biotech, TranscentaResearch Funding: AstraZeneca, Astellas Pharma, Daiichi Sankyo, Lilly, Boehringer Ingelheim, Puma Biotechnology, Takeda, Revolution MedicinesPatents, Royalties, Other Intellectual Property: I am a coinventor of a DFCI-owned patent on EGFR mutations licensed to Lab Corp. I receive postmarketing royalties from this invention Ticiana A. LealConsulting or Advisory Role: Takeda, Jazz Pharmaceuticals, AstraZeneca, EMD Serono, Merck, Boehringer Ingelheim, Blueprint Medicines, Daiichi Sankyo/Lilly, Bayer, Genentech, Lilly, Janssen, Mirati Therapeutics, Daiichi-Sankyo, Eisai, Daiichi Sankyo/AstraZeneca, Novocure Igor I. RybkinConsulting or Advisory Role: AstraZeneca Joshua K. SabariConsulting or Advisory Role: AstraZeneca, Janssen Oncology, Navire, Pfizer, Regeneron, Medscape, Takeda Minal A. BarveEmployment: Texas OncologyStock and Other Ownership Interests: Texas OncologyResearch Funding: Mary Crowley Research Center Lyudmila BazhenovaStock and Other Ownership Interests: Epic SciencesConsulting or Advisory Role: Genentech/Roche, Boehringer Ingelheim, Novartis, Regeneron, Merck, Johnson and Johnson, BMSi, Daichi, NEUVOGEN, Bayer, Sanofi, ORCIC, Turning Point TherapeuticsResearch Funding: BeyondSpring Pharmaceuticals Melissa L. JohnsonEmployment: HCA HealthcareConsulting or Advisory Role: Otsuka, Genentech/Roche (Inst), Boehringer Ingelheim (Inst), AstraZeneca (Inst), Calithera Biosciences (Inst), Merck (Inst), Loxo (Inst), Sanofi (Inst), Mirati Therapeutics (Inst), Pfizer (Inst), Guardant Health (Inst), Ribon Therapeutics (Inst), Incyte (Inst), AbbVie (Inst), Achilles Therapeutics (Inst), Atreca (Inst), GlaxoSmithKline (Inst), Gritstone Oncology (Inst), Janssen Oncology (Inst), Lilly (Inst), Novartis (Inst), Amgen (Inst), Bristol Myers Squibb (Inst), Daiichi Sankyo (Inst), EMD Serono (Inst), G1 Therapeutics (Inst), WindMIL (Inst), Checkpoint Therapeutics (Inst), Eisai (Inst), Axelia Oncology (Inst), Black Diamond Therapeutics (Inst), CytomX Therapeutics (Inst), EcoR1 Capital (Inst), Editas Medicine (Inst), Genmab (Inst), IDEAYA Biosciences (Inst), ITeos Therapeutics (Inst), Oncorus (Inst), Regeneron (Inst), Turning Point Therapeutics (Inst)Research Funding: EMD Serono (Inst), Kadmon (Inst), Janssen (Inst), Mirati Therapeutics (Inst), Genmab (Inst), Pfizer (Inst), AstraZeneca (Inst), Stemcentrx (Inst), Novartis (Inst), Checkpoint Therapeutics (Inst), Array BioPharma (Inst), Regeneron (Inst), Merck (Inst), Hengrui Pharmaceutical (Inst), Lycera (Inst), BeiGene (Inst), Tarveda Therapeutics (Inst), Loxo (Inst), AbbVie (Inst), Boehringer Ingelheim (Inst), Guardant Health (Inst), Daiichi Sankyo (Inst), Sanofi (Inst), CytomX Therapeutics (Inst), Dynavax Technologies (Inst), Corvus Pharmaceuticals (Inst), Incyte (Inst), Genocea Biosciences (Inst), Gritstone Oncology (Inst), Amgen (Inst), Genentech/Roche (Inst), Adaptimmune (Inst), Syndax (Inst), Neovia Oncology (Inst), Acerta Pharma (Inst), Takeda (Inst), Shattuck Labs (Inst), GlaxoSmithKline (Inst), Apexigen (Inst), Atreca (Inst), OncoMed (Inst), Lilly (Inst), Immunocore (Inst), Jounce Therapeutics (Inst), University of Michigan (Inst), WindMIL (Inst), TCR2 Therapeutics (Inst), Arcus Biosciences (Inst), Ribon Therapeutics (Inst), BerGenBio (Inst), Calithera Biosciences (Inst), Tmunity Therapeutics, Inc (Inst), Seven and Eight Biopharmaceuticals (Inst), Rubius Therapeutics (Inst), Curis (Inst), Silicon Therapeutics (Inst), Dracen (Inst), PMV Pharma (Inst), Artios (Inst), BioAtla (Inst), Elicio Therapeutics (Inst), Erasca, Inc (Inst), Harpoon (Inst), Helsinn Healthcare (Inst), Hutchison MediPharma (Inst), IDEAYA Biosciences (Inst), IGM Biosciences (Inst), Memorial Sloan-Kettering Cancer Center (Inst), NeoImmuneTech (Inst), Numab (Inst), RasCal (Inst), Relay Therapeutics (Inst), Revolution Medicines (Inst), Tempest Therapeutics (Inst), Tizona Therapeutics, Inc (Inst), Turning Point Therapeutics (Inst), Vyriad (Inst), Y-mAbs Therapeutics (Inst)Travel, Accommodations, Expenses: AbbVie, AstraZeneca, Genentech, Incyte, Merck, Pfizer, Sanofi Karen L. VelasteguiEmployment: Mirati Therapeutics, Arena PharmaStock and Other Ownership Interests: Mirati Therapeutics, Arena Pharma Cornelius CilliersEmployment: Mirati TherapeuticsStock and Other Ownership Interests: Mirati Therapeutics James G. ChristensenEmployment: Mirati TherapeuticsLeadership: Mirati TherapeuticsStock and Other Ownership Interests: Mirati TherapeuticsConsulting or Advisory Role: BridgeBio PharmaPatents, Royalties, Other Intellectual Property: Multiple patents in the last 2 years while employed at Mirati Therapeutics covering discovery of KRAS, LSD1, and EZH2 inhibitors (Inst) Xiaohong YanEmployment: Mirati TherapeuticsStock and Other Ownership Interests: Mirati TherapeuticsTravel, Accommodations, Expenses: Mirati Therapeutics Richard C. ChaoEmployment: Mirati TherapeuticsStock and Other Ownership Interests: Mirati Therapeutics, Pfizer, Merck Kyriakos P. PapadopoulosConsulting or Advisory Role: Basilea, Turning Point Therapeutics, Bicycle TherapeuticsResearch Funding: AbbVie (Inst), MedImmune (Inst), Daiichi Sankyo (Inst), Regeneron (Inst), Amgen (Inst), Calithera Biosciences (Inst), Incyte (Inst), Merck (Inst), Peloton Therapeutics (Inst), ADC Therapeutics (Inst), 3D Medicines (Inst), EMD Serono (Inst), Syros Pharmaceuticals (Inst), Mersana (Inst), MabSpace Biosciences (Inst), Jounce Therapeutics (Inst), Bayer (Inst), AnHeart Therapeutics (Inst), F-star (Inst), Linnaeus Therapeutics (Inst), Mirati Therapeutics (Inst), Tempest Therapeutics (Inst), Treadwell Therapeutics (Inst), Lilly (Inst), Pfizer (Inst), BioNTech (Inst), Bicycle Therapeutics (Inst), Kezar Life Sciences (Inst)No other potential conflicts of interest were reported.

Purpose: Recent randomized studies have suggested improvements in progression-free and overall survival with the addition of stereotactic body radiation therapy (SBRT, also known as SABR) in patients with oligometastatic non-small cell lung cancer. Given the novelty and complexity of incorporating SBRT in the oligometastatic setting, the multidisciplinary American Radium Society Lung Cancer Panel was assigned to create appropriate use criteria on SBRT as part of consolidative local therapy for patients with oligometastatic and oligoprogressive non-small cell lung cancer., Methods and Materials: A review of the current literature was conducted from January 1, 2008, to December 25, 2020, using the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines to systematically search the PubMed database to retrieve a comprehensive set of relevant articles., Results: Based on representation in existing randomized trials, the panel defined the term "oligometastasis" as ≤3 metastatic deposits (not including the primary tumor) in the previously untreated setting or after first-line systemic therapy after the initial diagnosis. "Oligoprogression" also referred to ≤3 discrete areas of progression in the setting of prior or ongoing receipt of systemic therapy. In all appropriate patients, the panel strongly recommends enrollment in a clinical trial whenever available. For oligometastatic disease, administering first-line systemic therapy followed by consolidative radiation therapy (to all sites plus the primary/nodal disease) is preferred over up-front radiation therapy. Owing to a dearth of data, the panel recommended that consolidative radiation therapy be considered on a case-by-case basis for 4 to 5 sites of oligometastatic disease, driver mutation-positive oligometastatic disease without progression on up-front targeted therapy, and oligoprogressive cases., Conclusions: Although SBRT/SABR appears to be both safe and effective in treating patients with limited metastatic sites of disease, many clinical circumstances require individualized management and strong multidisciplinary discussion on account of the limited existing data., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Introduction: Telisotuzumab vedotin (Teliso-V) is an anti-c-Met-directed antibody-drug conjugate that has exhibited antitumor activity as monotherapy in NSCLC. Its potential activity combined with programmed cell death protein-1 inhibitors has not been previously evaluated., Methods: In a phase 1b study (NCT02099058), adult patients (≥18 y) with advanced NSCLC received combination therapy with Teliso-V (1.6, 1.9, or 2.2 mg/kg, every 2 wk) plus nivolumab (3 mg/kg, 240 mg, or per locally approved label). The primary objective was to assess safety and tolerability; secondary objectives included the evaluation of antitumor activity., Results: As of January 2020, a total of 37 patients received treatment with Teliso-V (safety population) in combination with nivolumab; 27 patients (efficacy population) were c-Met immunohistochemistry-positive. Programmed death-ligand 1 (PD-L1) status was evaluated in the efficacy population (PD-L1-positive [PD-L1+]: n = 15; PD-L1-negative [PD-L1-]: n = 9; PD-L1-unknown: n = 3). The median age was 67 years and 74% (20 of 27) of patients were naive to immune checkpoint inhibitors. The most common any-grade treatment-related adverse events were fatigue (27%) and peripheral sensory neuropathy (19%). The pharmacokinetic profile of Teliso-V plus nivolumab was similar to Teliso-V monotherapy. The objective response rate was 7.4%, with two patients (PD-L1+, c-Met immunohistochemistry H-score 190, n = 1; PD-L1-, c-Met H-score 290, n = 1) having a confirmed partial response. Overall median progression-free survival was 7.2 months (PD-L1+: 7.2 mo; PD-L1-: 4.5 mo; PD-L1-unknown: not reached)., Conclusions: Combination therapy with Teliso-V plus nivolumab was well tolerated in patients with c-Met+ NSCLC with limited antitumor activity., (© 2021 The Authors.)

Purpose: Increasing use of oral chemotherapy has created unique challenges related to patient safety and compliance. To address this issue, the Henry Ford Cancer Institute at Henry Ford Health System developed and implemented a system-wide, multidisciplinary program named the Oral Chemotherapy Management Program (OCMP). The purpose of this study was to evaluate the impact of OCMP on patient outcomes in those receiving capecitabine., Methods: This was a retrospective, quasi-experimental study that compared outcomes in patients receiving capecitabine before and after OCMP implementation. The co-primary outcomes were incidence(s) of grade 1-4 and grade 3-4 adverse effects (AEs) associated with capecitabine. Secondary outcomes were emergency department (ED) visits, hospitalizations because of toxicity, and adherence rate., Results: OCMP patients had significantly lower overall incidence of AE of any grade (58.9% v 70.3%; 95% CI, 0.39 to 0.94; P = .03). OCMP implementation significantly lowered incidence of any grade and grade 3-4 nausea, vomiting, and/or diarrhea, and grade 3-4 hand-foot syndrome. It resulted in the decreased number of ED visits (8.9% v 18.9%; P = .005) and hospitalizations (6.3% v 17.1%; P = .002), as well as improved medication adherence rates (0.94 v 0.97; P = .03)., Conclusion: Most patients who developed capecitabine-related AE required intervention by OCMP. Implementation of OCMP reduced the incidence of high-grade AE, decreased the number of ED visits and hospitalizations because of AE, and improved the medication adherence rate., Competing Interests: Diana KostoffResearch Funding: Pfizer Igor I. RybkinConsulting or Advisory Role: AstraZenecaNo other potential conflicts of interest were reported.

Background: Clinical trials of the KRAS inhibitors adagrasib and sotorasib have shown promising activity in cancers harboring KRAS glycine-to-cysteine amino acid substitutions at codon 12 (KRAS G12C ). The mechanisms of acquired resistance to these therapies are currently unknown., Methods: Among patients with KRAS G12C -mutant cancers treated with adagrasib monotherapy, we performed genomic and histologic analyses that compared pretreatment samples with those obtained after the development of resistance. Cell-based experiments were conducted to study mutations that confer resistance to KRAS G12C inhibitors., Results: A total of 38 patients were included in this study: 27 with non-small-cell lung cancer, 10 with colorectal cancer, and 1 with appendiceal cancer. Putative mechanisms of resistance to adagrasib were detected in 17 patients (45% of the cohort), of whom 7 (18% of the cohort) had multiple coincident mechanisms. Acquired KRAS alterations included G12D/R/V/W, G13D, Q61H, R68S, H95D/Q/R, Y96C, and high-level amplification of the KRAS G12C allele. Acquired bypass mechanisms of resistance included MET amplification; activating mutations in NRAS , BRAF , MAP2K1 , and RET ; oncogenic fusions involving ALK , RET , BRAF , RAF1 , and FGFR3 ; and loss-of-function mutations in NF1 and PTEN . In two of nine patients with lung adenocarcinoma for whom paired tissue-biopsy samples were available, histologic transformation to squamous-cell carcinoma was observed without identification of any other resistance mechanisms. Using an in vitro deep mutational scanning screen, we systematically defined the landscape of KRAS mutations that confer resistance to KRAS G12C inhibitors., Conclusions: Diverse genomic and histologic mechanisms impart resistance to covalent KRAS G12C inhibitors, and new therapeutic strategies are required to delay and overcome this drug resistance in patients with cancer. (Funded by Mirati Therapeutics and others; ClinicalTrials.gov number, NCT03785249.)., (Copyright © 2021 Massachusetts Medical Society.)

Introduction: The standard-of-care therapy for extensive-stage SCLC has recently changed with the results of two large randomized trials revealing improved survival with the addition of immunotherapy to first-line platinum or etoposide chemotherapy. This has led to a lack of clarity around the role of consolidative thoracic radiation and prophylactic cranial irradiation in the setting of chemoimmunotherapy., Methods: The American Radium Society Appropriate Use Criteria are evidence-based guidelines for specific clinical conditions that are reviewed by a multidisciplinary expert panel. The guidelines include a review and analysis of current evidence with the application of consensus methodology (modified Delphi) to rate the appropriateness of treatments recommended by the panel for extensive-stage SCLC., Results: Current evidence supports either prophylactic cranial irradiation or surveillance with magnetic resonance imaging every 3 months for patients without evidence of brain metastases. Patients with brain metastases should receive whole-brain radiation with a recommended dose of 30 Gy in 10 fractions. Consolidative thoracic radiation can be considered in selected cases with the recommended dose ranging from 30 to 54 Gy; this recommendation was driven by expert opinion owing to the limited strength of evidence, as clinical trials addressing this question remain ongoing., Conclusions: Radiation therapy remains an integral component in the treatment paradigm for ES-SCLC., (Copyright © 2020. Published by Elsevier Inc.)

Introduction: Combined modality therapy with concurrent chemotherapy and radiation has long been the standard of care for limited-stage SCLC (LS-SCLC). However, there is controversy over best combined modality practices for LS-SCLC. To address these controversies, the American Radium Society (ARS) Thoracic Appropriate Use Criteria (AUC) Committee have developed updated consensus guidelines for the treatment of LS-SCLC., Methods: The ARS AUC are evidence-based guidelines for specific clinical conditions that are reviewed by a multidisciplinary expert panel. The guidelines include a review and analysis of current evidence with application of consensus methodology (modified Delphi) to rate the appropriateness of treatments recommended by the panel for LS-SCLC. Agreement or consensus was defined as less than or equal to 3 rating points from the panel median. The consensus ratings and recommendations were then vetted by the ARS Executive Committee and subject to public comment before finalization., Results: The ARS Thoracic AUC committee developed multiple consensus recommendations for LS-SCLC. There was strong consensus that patients with unresectable LS-SCLC should receive concurrent chemotherapy with radiation delivered either once or twice daily. For medically inoperable T1-T2N0 LS-SCLC, either concurrent chemoradiation or stereotactic body radiation followed by adjuvant chemotherapy is a reasonable treatment option. The panel continues to recommend whole-brain prophylactic cranial irradiation after response to chemoradiation for LS-SCLC. There was panel agreement that prophylactic cranial irradiation with hippocampal avoidance and programmed cell death protein-1/programmed death-ligand 1-directed immune therapy should not be routinely administered outside the context of clinical trials at this time., Conclusions: The ARS Thoracic AUC Committee provide consensus recommendations for LS-SCLC that aim to provide a groundwork for multidisciplinary care and clinical trials., (Copyright © 2020 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.)

Despite decades of research, efforts to directly target KRAS have been challenging. MRTX849 was identified as a potent, selective, and covalent KRAS G12C inhibitor that exhibits favorable drug-like properties, selectively modifies mutant cysteine 12 in GDP-bound KRAS G12C , and inhibits KRAS-dependent signaling. MRTX849 demonstrated pronounced tumor regression in 17 of 26 (65%) KRAS G12C -positive cell line- and patient-derived xenograft models from multiple tumor types, and objective responses have been observed in patients with KRAS G12C -positive lung and colon adenocarcinomas. Comprehensive pharmacodynamic and pharmacogenomic profiling in sensitive and partially resistant nonclinical models identified mechanisms implicated in limiting antitumor activity including KRAS nucleotide cycling and pathways that induce feedback reactivation and/or bypass KRAS dependence. These factors included activation of receptor tyrosine kinases (RTK), bypass of KRAS dependence, and genetic dysregulation of cell cycle. Combinations of MRTX849 with agents that target RTKs, mTOR, or cell cycle demonstrated enhanced response and marked tumor regression in several tumor models, including MRTX849-refractory models. SIGNIFICANCE: The discovery of MRTX849 provides a long-awaited opportunity to selectively target KRAS G12C in patients. The in-depth characterization of MRTX849 activity, elucidation of response and resistance mechanisms, and identification of effective combinations provide new insight toward KRAS dependence and the rational development of this class of agents. See related commentary by Klempner and Hata, p. 20 . This article is highlighted in the In This Issue feature, p. 1 ., (©2019 American Association for Cancer Research.)

Atrial cardiomyocytes, neurons, and endocrine tissues secrete neurotransmitters and peptide hormones via large dense-core vesicles (LDCVs). We describe a new member of the Ras family of G-proteins, named RRP17, which is expressed specifically in cardiomyocytes, neurons, and the pancreas. RRP17 interacts with Ca(2+)-activated protein for secretion-1 (CAPS1), one of only a few proteins known to be associated exclusively with LDCV exocytosis. Ectopic expression of RRP17 in cardiomyocytes enhances secretion of atrial natriuretic peptide (ANP), a regulator of blood pressure and natriuresis. Conversely, genetic deletion of RRP17 in mice results in dysmorphic LDCVs, impaired ANP secretion, and hypertension. These findings identify RRP17 as a component of the cellular machinery involved in regulated secretion within the heart and potential mediator of the endocrine influence of the heart on other tissues.

Skeletal muscles are a mosaic of slow and fast twitch myofibers. During embryogenesis, patterns of fiber type composition are initiated that change postnatally to meet physiological demand. To examine the role of the protein phosphatase calcineurin in the initiation and maintenance of muscle fiber types, we used a "Flox-ON" approach to obtain muscle-specific overexpression of the modulatory calcineurin-interacting protein 1 (MCIP1/DSCR1), an inhibitor of calcineurin. Myo-Cre transgenic mice with early skeletal muscle-specific expression of Cre recombinase were used to activate the Flox-MCIP1 transgene. Contractile components unique to type 1 slow fibers were absent from skeletal muscle of adult Myo-Cre/Flox-MCIP1 mice, whereas oxidative capacity, myoglobin content, and mitochondrial abundance were unaltered. The soleus muscles of Myo-Cre/Flox-MCIP1 mice fatigued more rapidly than the wild type as a consequence of the replacement of the slow myosin heavy chain MyHC-1 with a fast isoform, MyHC-2A. MyHC-1 expression in Myo-Cre/Flox-MCIP1 embryos and early neonates was normal. These results demonstrate that developmental patterning of slow fibers is independent of calcineurin, while the maintenance of the slow-fiber phenotype in the adult requires calcineurin activity.

Skeletal and cardiac muscle depend on high turnover of ATP made by mitochondria in order to contract efficiently. The transcriptional coactivator PGC-1alpha has been shown to function as a major regulator of mitochondrial biogenesis and respiration in both skeletal and cardiac muscle, but this has been based only on gain-of-function studies. Using genetic knockout mice, we show here that, while PGC-1alpha KO mice appear to retain normal mitochondrial volume in both muscle beds, expression of genes of oxidative phosphorylation is markedly blunted. Hearts from these mice have reduced mitochondrial enzymatic activities and decreased levels of ATP. Importantly, isolated hearts lacking PGC-1alpha have a diminished ability to increase work output in response to chemical or electrical stimulation. As mice lacking PGC-1alpha age, cardiac dysfunction becomes evident in vivo. These data indicate that PGC-1alpha is vital for the heart to meet increased demands for ATP and work in response to physiological stimuli.

Studies of cardiac muscle gene expression and signaling have been hampered by the lack of immortalized cardiomyocyte cell lines capable of proliferation and irreversible withdrawal from the cell cycle. With the goal of creating such cell lines, we generated transgenic mice using cardiac-specific cis-regulatory elements from the mouse Nkx2.5 gene to drive the expression of a simian virus 40 large T-antigen (TAg) gene flanked by sites for recombination by Cre recombinase. These transgenic mice developed tumors within the ventricular myocardium. Cells isolated from these tumors expressed cardiac markers and proliferated rapidly during serial passage in culture, without apparent senescence. However, they were unable to exit the cell cycle and failed to exhibit morphological features of terminal differentiation. Introduction of Cre recombinase to these cardiac cell lines by adenoviral delivery resulted in the elimination of TAg expression, accompanied by rapid cessation of cell division, and increase in cell size without an apparent induction of cellular differentiation. Incubation of cells lacking TAg in serum-deficient media with various pharmacological agents (norepinephrine, phenylephrine, or bone morphogenetic protein-2/4) or constitutively active calcium/calmodulin-dependent protein kinase I and/or calcineurin led to the formation of sarcomeres and up-regulation of cardiac genes involved in excitation-contraction coupling. The combination of TAg expression under the control of an early cardiac promoter and Cre-mediated recombination allowed us to derive an immortal cell line from the ventricular myocardium that could be controllably withdrawn from the cell cycle. The conditional expression of TAg in this manner permits propagation and regulated growth termination of cell types that are otherwise unable to be maintained in cell culture and may have applications for cardiac repair technologies.

Phosphorylation of the translation repressor eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) is thought to be partly responsible for increased protein synthesis induced by growth factors. This study investigated the effect of a G(q)-coupled receptor on protein synthesis and the phosphorylation state and function of 4E-BP1 in Rat-1 fibroblasts expressing the human alpha(1A) adrenergic receptor. Treatment of cells with phenylephrine (PE), a specific alpha(1) adrenergic receptor agonist, increased protein synthesis and induced the phosphorylation of 4E-BP1 and its release from translation initiation factor 4E. Although the PE-induced phosphorylation of 4E-BP1 was blocked by the phosphatidylinositol 3-kinase inhibitor LY294002, neither phosphatidylinositol 3-kinase nor Akt, its downstream effector, is activated in cells treated with PE (Ballou, L. M., Cross, M. E., Huang, S., McReynolds, E. M., Zhang, B. X., and Lin, R. Z., J. Biol. Chem. 275, 4803-4809). The effect of PE on 4E-BP1 phosphorylation was also abolished in cells depleted of intracellular Ca(2+) and in cells pretreated with calmodulin antagonists. By contrast, phosphorylation of 4E-BP1 still occurred in cells in which the Ca(2+)- and diacylglycerol-dependent isoforms of protein kinase C were down-regulated by prolonged exposure to a phorbol ester. We conclude that activation of the alpha(1A) adrenergic receptor in Rat-1 fibroblasts leads to phosphorylation of 4E-BP1 via a pathway that is Ca(2+)- and calmodulin-dependent. Phosphatidylinositol 3-kinase, Akt, and phorbol ester-sensitive protein kinase C isoforms do not appear to be required in this signaling pathway.

Exposure to the moderate stressor of 3-h restraint for 3 consecutive days causes a temporary drop in food intake but a permanent reduction in body weight in adult rats. Young rats did not show the same response. Food intake of adult rats exposed to repeated restraint was significantly lower than that of controls for 4 days after the end of stress, and there was no rebound hyperphagia. Body weight remained significantly lower for at least 40 days after stress. When the rats were fed a high-fat diet of 80% chow and 20% vegetable shortening (48% kcal fat, 16% protein), lean body mass accounted for all of the weight loss in stressed rats. When the experiment was repeated with a purified high-fat diet containing corn oil and coconut oil as the source of fat (41% kcal fat, 16% protein), weight loss consisted of both lean and fat tissue. There were no sustained changes in single time point measures of corticosterone, insulin, or leptin that could account for the reduced body weight in these rats.

Three experiments were conducted to investigate the effect of restraint stress applied at different times of the light-dark cycle on feeding behavior and body weight of rats. Sprague-Dawley rats were restrained for 3 h in restraining tubes either at the start or the end of the light cycle. There was a significant reduction in food intake on the day of restraint and no change in food intake during a 10-day recovery period in either experiment. Reductions of food intake on the day of restraint were about the same for both restrained groups compared with their controls. When stress was applied in the evening, eating was inhibited during the first 2 h after restraint, whereas in rats restrained in the morning, feeding was suppressed twice: during the 4 h after restraint and during the first 2 h of the dark cycle. Restraint induced a significant weight loss that was greater in the rats stressed in the morning. Neuropeptide Y (NPY) levels determined at the time of food suppression for both experiments (beginning of the dark cycle) revealed an elevation of NPY in the paraventricular nucleus of rats stressed in the morning compared with other groups, but no difference in hypothalamic NPY mRNA expression. Expression of uncoupling protein mRNA in brown adipose tissue and leptin mRNA in epididymal fat, measured at the start of the dark period, was not altered by stress. There was an elevation of dopamine turnover in the hypothalami of rats restrained at the end of light cycle, but not those restrained in the morning. These results show that restraint stress has a greater effect on metabolism and energy balance when it is applied in the morning. Additional studies are needed to elucidate mechanisms involved in the suppression of food intake 9 h after restraint.

Ventricular myocardium of 6 mature male Wistar line rats (100-129 g of body weight) cultured in vitro was exposed to the effect of vasopressin, oxitocin, dophamin and norepinephrine. The cell structures were observed by means of light microscopy. Nonapeptides and monoamines were found to cause cardiomyocyte hypertrophy and hyperplasia Vasopressin and oxytocin stimulate the endotheliocyte and myocyte proliferation and interstitial fibrillogenesis. Adequate trophic conditions were created to maintain energetic and anabolic metabolism of the surviving, hypertrophic and reorganizing cardiomyocytes.