Stephen R Hammes

University of Rochester, Rochester, New York, United States

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Publications (65)318.53 Total impact

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    ABSTRACT: Obesity is considered detrimental to women's reproductive health. Although most of the attention has been focused on the effects of obesity on hypothalamic function, studies suggest a multifactorial impact. In fact, obesity is associated with reduced fecundity even in women with regular cycles, indicating that there may be local ovarian effects modulating fertility. Here we describe a novel mechanism for leptin actions directly in the ovary that may account for some of the negative effects of obesity on ovarian function. We find that normal cycling, obese, hyperleptinemic mice fed with a high fat diet are sub-fertile and ovulate fewer oocytes compared to animals fed with a normal diet. Importantly, we show that leptin induces expression of the neuropeptide Cocaine-and Amphetamine-Regulated Transcript (CART) in the granulosa cells of ovarian follicles both in vitro and in vivo. CART then negatively affects intra-cellular cAMP levels, MAPK signaling, and aromatase gene expression, which leads to lower estradiol synthesis in granulosa cells and altered ovarian folliculogenesis. Finally, in human samples from patients undergoing in vitro fertilization, we show a significant positive correlation between patient BMI, CART mRNA expression in granulosa cells, and CART peptide levels in follicular fluid. These observations suggest that, under obese conditions, CART acts as a local mediator of leptin in the ovary to cause ovarian dysfunction and reduced fertility.
    No preview · Article · Jan 2016 · Endocrinology
  • Stephen R Hammes

    No preview · Article · Aug 2015 · Molecular Endocrinology
  • Allison Light · Stephen R Hammes
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    ABSTRACT: Oocyte maturation and cumulus cell expansion depend on LH-mediated upregulation of membrane bound EGF-like ligands, including amphiregulin, epiregulin, and betacellulin. These ligands then trans-activate the EGF receptor (EGFR) after release by matrix metalloproteinases (MMPs). However, direct measurement of released EGF-like ligands or MMPs from granulosa cells has not been formally evaluated, nor has direct identification of responsible MMPs. Here we address these issues by analyzing LH-induced steroidogenesis, which is also MMP- and EGFR-dependent, in freshly isolated mouse primary granulosa cells. We demonstrate a correlation between amphiregulin and epiregulin mRNA induction and steroid production in LH-treated granulosa cells as well as in ovaries of hCG-treated mice. In contrast, LH does not alter Mmp1, Mmp2, Mmp3, Mmp8, Mmp9, or Adam17 mRNA expression. We demonstrate that, in primary mouse granulosa cells, LH triggers release of soluble amphiregulin that correlates with steroid production, both of which are blocked by MMP2/9 inhibition, confirming that MMP2/9 likely regulates LH-induced amphiregulin release and downstream processes. Notably, LH does not alter secretion of MMP2/9 from primary granulosa cells, nor does it modulate MMP activity. These findings indicate that, in the ovary, LH dictates EGFR-mediated processes not by regulating MMPs, but instead by increasing EGF-like ligand availability. In contrast, LH stimulation of primary mouse Leydig cells does not induce EGF-like ligand expression or require MMP2/9 for steroidogenesis, confirming marked differences in LH receptor-induced processes in the testes. Our results suggest that MMP inhibition may be a means of attenuating excess ovarian steroid production in diseases like polycystic ovary syndrome. Copyright 2015 by The Society for the Study of Reproduction.
    No preview · Article · Jul 2015 · Biology of Reproduction
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    Stephen R Hammes

    Preview · Article · May 2015 · Molecular Endocrinology
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    Stephen R. Hammes · Paul J. Davis
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    ABSTRACT: The genomic actions of thyroid hormone and steroids depend upon primary interactions of the hormones with their specific nuclear receptor proteins. Formation of nuclear co-activator or co-repressor complexes involving the liganded receptors subsequently result in transcriptional events-either activation or suppression-at genes that are specific targets of thyroid hormone or steroids. Nongenomic actions of thyroid hormone and steroids are in contrast initiated at binding sites on the plasma membrane or in cytoplasm or organelles and do not primarily require formation of intranuclear receptor protein-hormone complexes. Importantly, hormonal actions that begin nongenomically outside the nucleus often culminate in changes in nuclear transcriptional events that are regulated by both traditional intranuclear receptors as well as other nuclear transcription factors. In the case of thyroid hormone, the extranuclear receptor can be the classical "nuclear" thyroid receptor (TR), a TR isoform, or integrin αvβ3. In the case of steroid hormones, the membrane receptor is usually, but not always, the classical "nuclear" steroid receptor. This concept defines the paradigm of overlapping nongenomic and genomic hormone mechanisms of action. Here we review some examples of how extranuclear signaling by thyroid hormone and by estrogens and androgens modulates intranuclear hormone signaling to regulate a number of vital biological processes both in normal physiology and in cancer progression. We also point out that nongenomic actions of thyroid hormone may mimic effects of estrogen in certain tumors. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.
    Preview · Article · Apr 2015 · Best Practice & Research: Clinical Endocrinology & Metabolism
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    ABSTRACT: We investigated the association of signaling proteins with epidermal growth factor (EGF) receptors (EGFR) using biotinylated EGF bound to streptavidin that is covalently coupled in an ordered array of micron-sized features on silicon surfaces. Using NIH-3T3 cells stably expressing EGFR, we observe concentration of fluorescently labeled receptors and stimulated tyrosine phosphorylation that are spatially confined to the regions of immobilized EGF and quantified by cross-correlation analysis. We observe recruitment of phosphorylated paxillin to activated EGFR at these patterned features, as well as β1-containing integrins that preferentially localize to more peripheral EGF features, as quantified by radial fluorescence analysis. In addition, we detect recruitment of EGFP-Ras, MEK, and phosphorylated Erk to patterned EGF in a process that depends on F-actin and phosphoinositides. These studies reveal and quantify the coformation of multiprotein EGFR signaling complexes at the plasma membrane in response to micropatterned growth factors. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.
    No preview · Article · Dec 2014 · Biophysical Journal
  • Quang V Ton · Stephen R Hammes
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    ABSTRACT: Pheochromocytomas are neuroendocrine tumors that commonly lead to excess catecholamine secretion, resulting in elevated blood pressure. In addition to potentiating vasoconstriction, catecholamines promote endothelial dysfunction, as evidenced by elevated markers of endothelial dysfunction, ADMA and sVCAM-1, in patients with pheochromcytoma. Importantly, catecholamine-induced endothelial dysfunction and hypertension may not only be due to catecholamine production by neuroendocrine tumors, as vascular endothelial cells have now been demonstrated to synthesize and secrete catecholamines. This local vascular catecholamine release appears to be triggered by hypoxia. In fact, chronic intermittent hypoxia both in vitro and in vivo leads to stabilization of hypoxic-inducible factors that increase gene expression of catecholamine-synthesizing enzymes. In an effort to target catecholamines as a means of treating hypertension, novel therapeutic options are being explored, including the generation of pharmacophores that mimic the suppressive effects of catestatin on catecholamine release as well as the use of renalase enhancers to increase catecholamine metabolism.
    No preview · Article · Dec 2014 · Current Hypertension Reports
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    Stephen R Hammes

    Preview · Article · Nov 2014 · Molecular Endocrinology
  • Stephen R Hammes · Susanne U Miedlich · Aritro Sen
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    ABSTRACT: Paxillin is a well-characterized cytoplasmic adaptor protein that is known to play important roles in cytoskeletal rearrangement, cell adhesion, and cell motility. In addition to its structural functions, paxillin has more recently been shown to function as a regulator of cell division-mediating steroid-triggered meiosis in oocytes as well as steroid- and growth factor-induced proliferation in prostate and breast cancer. Paxillin mediates these processes through a conserved pathway that involves both extranuclear (nongenomic) and nuclear (genomic) steroid signaling, as well as both cytoplasmic and nuclear kinase signaling. In fact, paxillin appears to serve as a critical liaison between extranuclear and nuclear signaling in response to multiple stimuli, making it a fascinating molecule to study when trying to determine how growth signals from the membrane lead to important proliferative changes in the nucleus. This chapter outlines recent advances in understanding how paxillin regulates both steroid and growth factor signaling, focusing on the conserved nature of its actions from a frog germ cell to a human cancer cell.
    No preview · Article · Sep 2014 · Methods in Molecular Biology
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    Stephen R Hammes

    Preview · Article · Jul 2014 · Molecular Endocrinology
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    ABSTRACT: Background elevated sympathetic nervous system activity is a salient characteristic of heart failure (HF) progression. It causes pathologic desensitization of β -adrenergic receptors (β -AR), facilitated predominantly through Gβ γ-mediated signaling. The adrenal glands are key contributors to the chronically elevated plasma catecholamine levels observed in HF, where adrenal α2-AR feedback inhibitory function is impaired also through Gβ γ-mediated signaling. Objective we propose simultaneous inhibition of Gβ γ signaling in the heart and the adrenal gland as a novel therapeutic approach for HF. Methods and results we investigated the efficacy of a small molecule Gβ γ inhibitor, gallein, in a clinically relevant, pressure-overload model of HF. Daily gallein treatment (10 mg/kg/day), initiated four weeks following transverse aortic constriction, improved survival and cardiac function, and attenuated cardiac remodeling. Mechanistically, gallein restored β-AR membrane density in cardiomyocytes, attenuated Gβ γ-mediated GRK2-PI3Kγ membrane recruitment, and reduced Akt and GSK-3β phosphorylation. Gallein also reduced circulating plasma catecholamine levels as well as catecholamine production in isolated mouse adrenal glands by restoring adrenal α2-AR feedback inhibition. In human adrenal endocrine tumors (pheochromocytoma), gallein attenuated catecholamine secretion, as well as GRK2 expression and membrane translocation. Conclusions these data suggest small molecule Gβ γ inhibition as a systemic pharmacologic therapy for HF by simultaneously normalizing pathologic adrenergic/Gβ γ signaling in both the heart and the adrenal gland. Our data also suggest important endocrine/cardiovascular interactions and a possible role for small molecule Gβ γ inhibition in treating endocrine tumors such as pheochromocytoma, in addition to HF.
    Preview · Article · Jun 2014 · Journal of the American College of Cardiology
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    ABSTRACT: Steroid receptors are found in discrete cellular locations, but it is unknown whether extranuclear pools are necessary for normal organ development. To assess this, we developed a point mutant estrogen receptor α (ERα) knockin mouse (C451A) that precludes palmitoylation and membrane trafficking of the steroid receptor in all organs. Homozygous knockin female mice (nuclear-only ERα [NOER]) show loss of rapid signaling that occurs from membrane ERα in wild-type mice. Multiple developmental abnormalities were found, including infertility, relatively hypoplastic uteri, abnormal ovaries, stunted mammary gland ductal development, and abnormal pituitary hormone regulation in NOER mice. These abnormalities were rescued in heterozygous NOER mice that were comparable to wild-type mice. mRNAs implicated in organ development were often poorly stimulated by estrogen only in homozygous NOER mice. We conclude that many organs require membrane ERα and resulting signal transduction to collaborate with nuclear ERα for normal development and function.
    Full-text · Article · May 2014 · Developmental Cell
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    ABSTRACT: Although androgen excess is considered detrimental to women's health and fertility, global and ovarian granulosa cell-specific androgen-receptor (AR) knockout mouse models have been used to show that androgen actions through ARs are actually necessary for normal ovarian function and female fertility. Here we describe two AR-mediated pathways in granulosa cells that regulate ovarian follicular development and therefore female fertility. First, we show that androgens attenuate follicular atresia through nuclear and extranuclear signaling pathways by enhancing expression of the microRNA (miR) miR-125b, which in turn suppresses proapoptotic protein expression. Second, we demonstrate that, independent of transcription, androgens enhance follicle-stimulating hormone (FSH) receptor expression, which then augments FSH-mediated follicle growth and development. Interestingly, we find that the scaffold molecule paxillin regulates both processes, making it a critical regulator of AR actions in the ovary. Finally, we report that low doses of exogenous androgens enhance gonadotropin-induced ovulation in mice, further demonstrating the critical role that androgens play in follicular development and fertility. These data may explain reported positive effects of androgens on ovulation rates in women with diminished ovarian reserve. Furthermore, this study demonstrates mechanisms that might contribute to the unregulated follicle growth seen in diseases of excess androgens such as polycystic ovary syndrome.
    Full-text · Article · Feb 2014 · Proceedings of the National Academy of Sciences
  • Stephen R Hammes

    No preview · Article · Jan 2014 · Molecular Endocrinology

  • No preview · Article · Dec 2013 · Endocrine Practice
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    ABSTRACT: Lymphangioleiomyomatosis (LAM) is a rare disease characterized by proliferation of abnormal smooth-muscle cells in the lungs, leading to functional loss and sometimes lung transplantation. While the origin of LAM cells is unknown, several features of LAM provide clues. First, LAM cells contain inactivating mutations in genes encoding Tsc1 or Tsc2, proteins that limit mTORC1 activity. Second, LAM tumors recur after lung transplantation, suggesting a metastatic pathogenesis. Third, LAM is found almost exclusively in women. Finally, LAM shares features with uterine leiomyomas, benign tumors of myometrial cells. From these observations, we proposed that LAM cells might originate from uterine leiomyomas containing Tsc mutations. To test our hypothesis, and to develop mouse models for leiomyoma and LAM, we targeted Tsc2 deletion primarily in uterine cells. In fact, nearly 100% of uteri from uterine-specific Tsc2 knockout mice developed myometrial proliferation and uterine leiomyomas by 12 and 24 weeks, respectively. Myometrial proliferation and mTORC1/S6 activity were abrogated by the mTORC1 inhibitor rapamycin or by elimination of sex steroid production through ovariectomy or aromatase inhibition. In ovariectomized Tsc2 null mice, mTORC1/S6 activity and myometrial growth were restored by estrogen but not progesterone. Thus, even without Tsc2, estrogen appears to be required for myometrial mTORC1/S6 signaling and proliferation. Finally, we found Tsc2 null myometrial tumors in lungs of older Tsc2 uterine-specific knockout females, suggesting that lung LAM-like myometrial lesions may indeed originate from the uterus. This mouse model may improve our understanding of LAM and leiomyomas, and might lead to novel therapeutic strategies for both diseases.
    No preview · Article · Jul 2013 · Molecular Endocrinology
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    ABSTRACT: Histologically, malignant struma ovarii metastasizes rarely, and only a few cases reported bone metastasis. Here, we describe 2 cases of biologically malignant struma ovarii with pelvic bone metastasis. Case 1 is a 22-year-old female who was found to have a large left ovarian mass during routine prenatal ultrasound. Papillary thyroid cancer arising in struma ovarii was identified after laparoscopic salpingo-oophorectomy. After total thyroidectomy, radioactive iodine whole-body scan revealed extrathyroidal iodine uptake in left anterior pelvis. Subsequent I-131 treatment resolved the pelvic metastasis. Case 2 is a 49-year-old female who was diagnosed with malignant struma ovarii in 1996 and presented in 2007 with pelvic recurrence and extensive left hip metastasis. Treatment with resection of the pelvic tumor, total thyroidectomy, and multiple I-131 ablation led to eventual resolution of the abdominal and left hip foci. In conclusion, we present 2 rare cases of malignant struma ovarii, both with metastasis to the pelvic bone. This report makes pelvic bone the most frequent site for bone metastasis in malignant struma ovarii. It also emphasizes the importance of total thyroidectomy in allowing identification and treatment of bony metastasis with radioactive iodine.
    No preview · Article · Feb 2013 · Gynecologic and Obstetric Investigation
  • Allison Light · Stephen R Hammes
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    ABSTRACT: Steroid production by all three major steroidogenic tissues, the adrenals, testes, and ovaries, is critical for survival and reproduction of all animals. As such, the pathways that regulate steroidogenesis are conserved between these tissues, from the steroidogenic enzymes and cofactors that synthesize steroids, to the intracellular signaling molecules and Gα(s)-coupled receptors that mediate the activity of these enzymes. Recent work has revealed another important conserved pathway in steroidogenesis: crosstalk between membrane G protein-coupled receptors and membrane receptor tyrosine kinases. Luteinizing hormone (LH) or adrencorticotropic hormone (ACTH) binding to their cognate Gα(s)-coupled membrane receptors in the gonads and adrenals, respectively, leads to cAMP-induced trans-activation of the epidermal growth factor (EGF) receptor, followed by activation of Akt and Erk signaling. These kinase signals then activate Steroidogenic Acute Regulatory (StAR) protein, which promotes steroid production. Inhibition of this pathway abrogates both LH- and ACTH-induced steroidogenesis. Interestingly, LH-induced transactivation of the EGF receptor in the ovary uniquely requires matrix metalloproteinase-mediated release of EGF receptor ligands, and inhibition of these proteases blocks LH-induced steroidogenesis. Given this unique need for matrix metalloproteinases in ovarian steroidogenesis, MMP inhibition may prove to be useful when treating diseases of excess ovarian steroid production, such as polycystic ovary syndrome.
    No preview · Article · Feb 2013 · Steroids
  • Stephen Hammes · Martin Kelly · Joyce Slingerland

    No preview · Article · Jan 2013 · Steroids
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    Stephen R Hammes · Vera P Krymskaya
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    ABSTRACT: Pulmonary lymphangioleiomyomatosis (LAM) is a rare disease found almost exclusively in women that is characterized by neoplastic growth of atypical smooth muscle-like cells in the lung, destruction of lung parenchyma, and obstruction of lymphatics. These processes lead to the formation of lung cysts, rupture of which results in spontaneous pneumothorax. Progression of LAM often results in loss of pulmonary function and death. LAM affects predominantly women of childbearing age and is exacerbated by pregnancy. The only proven treatment for LAM is lung transplantation, and even then LAM cells will often return to the transplanted lung. However, methodical and targeted approaches toward understanding LAM pathophysiology have led to the discovery of new potential therapeutic avenues. For example, the mutational inactivation of tumor suppressor complex genes tuberous sclerosis complex 1 or tuberous sclerosis complex 2 has been shown to be present in lung LAM cells. These mutations occur sporadically or in association with inherited hamartoma syndrome tuberous sclerosis (TSC). Since TSC genes function as negative regulators of the mammalian target of rapamycin, a major controller of cell growth, metabolism, and survival, rapamycin analogs have recently been used to treat LAM patients with promising results. Similarly, studies focusing on the importance of estrogen in LAM progression have suggested that anti-estrogen therapy might prove to be an alternative means of treating LAM. This minireview summarizes recent progress in understanding LAM pathophysiology, including the latest preclinical and clinical studies, and insights regarding the role of hormones in LAM.
    Full-text · Article · Nov 2012 · Hormones and Cancer

Publication Stats

2k Citations
318.53 Total Impact Points


  • 2010-2015
    • University of Rochester
      • • Department of Medicine
      • • Division of Hospital Medicine
      Rochester, New York, United States
  • 2014
    • University Center Rochester
      Рочестер, Minnesota, United States
  • 2001-2008
    • University of Texas Southwestern Medical Center
      • • Department of Developmental Biology
      • • Department of Internal Medicine
      • • Department of Pharmacology
      • • Division of Endocrinology
      Dallas, Texas, United States
    • University of Texas at Dallas
      Richardson, Texas, United States
  • 2007
    • University of Pittsburgh
      Pittsburgh, Pennsylvania, United States
  • 1999
    • Cardiovascular Research Foundation
      New York, New York, United States
  • 1998
    • University of California, San Francisco
      • Department of Medicine
      San Francisco, California, United States