Abstract A61: FAK activity sustains intrinsic and acquired ovarian cancer resistance to platinum chemotherapy

Gene copy number alterations, tumor cell stemness, and development of platinum chemotherapy resistance contribute to high-grade serous ovarian cancer (HGSOC) recurrence. Stemness phenotypes involving Wnt-beta-catenin, aldehyde dehydrogenase activities, intrinsic platinum resistance, and tumorsphere formation are here associated with spontaneous genetic gains in KRAS, MYC, and FAK (KMF) genes, in a new aggressive murine model of ovarian cancer. Noncanonical signaling via FAK sustained KMF and human tumorsphere proliferation as well as resistance to cisplatin cytotoxicity. Platinum-resistant tumorspheres can acquire a dependence on FAK for growth. Accordingly, increased FAK tyrosine phosphorylation was observed within HGSOC patient tumors surviving neoadjuvant chemotherapy. Combining a FAK inhibitor with platinum overcame chemoresistance, triggering tumor cell apoptosis. FAK transcriptomic analyses across knockout and reconstituted cells identified 135 genes elevated by a FAK activity-dependent, beta-catenin, and Myc signaling axis including pluripotency and DNA repair genes. Identified target increases in HGSOC tumors may reflect oncogenic FAK signaling.

Citation Format: Carlos J. Díaz Osterman, Duygu Ozmadenci, Elizabeth G. Kleinschmidt, Kristin N. Taylor, Allison M. Barrie, Shulin Jiang, Lisa M. Bean, Florian J. Sulzmaier, Jian Li, Xiao Lei Chen, Guo Fu, Marjaana Ojalill, Pekka Rappu, Jyrki Heino, Adam A. Mark, Guorong Xu, Kathleen M. Fisch, David T. Weaver, Jonathan A. Pachter, Balázs Győrffy, Michael T. McHale, Denise C. Connolly, Alfredo Molinolo, Dwayne G. Stupack, David D. Schlaepfer. FAK activity sustains intrinsic and acquired ovarian cancer resistance to platinum chemotherapy [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr A61.

FAK activity sustains intrinsic and acquired ovarian cancer resistance to platinum chemotherapy

Gene copy number alterations, tumor cell stemness, and the development of platinum chemotherapy resistance contribute to high-grade serous ovarian cancer (HGSOC) recurrence. Stem phenotypes involving Wnt-β-catenin, aldehyde dehydrogenase activities, intrinsic platinum resistance, and tumorsphere formation are here associated with spontaneous gains in Kras, Myc and FAK (KMF) genes in a new aggressive murine model of ovarian cancer. Adhesion-independent FAK signaling sustained KMF and human tumorsphere proliferation as well as resistance to cisplatin cytotoxicity. Platinum-resistant tumorspheres can acquire a dependence on FAK for growth. Accordingly, increased FAK tyrosine phosphorylation was observed within HGSOC patient tumors surviving neo-adjuvant chemotherapy. Combining a FAK inhibitor with platinum overcame chemoresistance and triggered cell apoptosis. FAK transcriptomic analyses across knockout and reconstituted cells identified 135 targets, elevated in HGSOC, that were regulated by FAK activity and β-catenin including Myc, pluripotency and DNA repair genes. These studies reveal an oncogenic FAK signaling role supporting chemoresistance.

Rgnef promotes ovarian tumor progression and confers protection from oxidative stress

Ovarian cancer is the fifth-leading cause of cancer death among women. The dissemination of ovarian tumors and growth as spheroids accompanies late-stage disease. In cell culture, ovarian tumor cell spheroids can exhibit elevated resistance to environmental stressors, such as reactive oxygen species. Homeostatic balance of the antioxidant response is a protective mechanism that prevents anoikis, a form of programmed cell death. Signaling pathways activated by integrin receptors suppress anoikis. Rgnef (ARHGEF28/p190RhoGEF) is a guanine nucleotide exchange factor that is activated downstream of integrins. We find that Rgnef protein levels are elevated in late-stage serous ovarian cancer, high Rgnef mRNA levels are associated with decreased progression-free and overall survival, and genomic ARHGEF28 loss is associated with increased patient survival. Using transgenic and transplantable Rgnef knockout mouse models, we find that Rgnef is essential for supporting three-dimensional ovarian spheroid formation in vitro and tumor growth in mice. Using RNA-sequencing and bioinformatic analyses, we identify a conserved Rgnef-supported anti-oxidant gene signature including Gpx4, Nqo1, and Gsta4; common targets of the NF-kB transcription factor. Antioxidant treatment enhanced growth of Rgnef-knockout spheroids and Rgnef re-expression facilitated NF-κB-dependent tumorsphere survival. These studies reveal a new role for Rgnef in ovarian cancer to facilitate NF-κB-mediated gene expression protecting cells from oxidative stress.

Abstract B47: Rgnef (p190RhoGEF/Arhgef28) loss impairs ovarian tumor metastatic growth

Increased activation of FAK and Rho GTPase regulatory pathways is associated with shorter survival in patients with high-grade serous ovarian carcinoma (HGSOC). However, the key mediators of these signaling events in HGSOC remain unknown. We have previously shown that the Rho guanine nucleotide exchange factor Rgnef (also named p190RhoGEF or Arhgef28) activates FAK as well as RhoA GTPase in mouse fibroblasts. Here we find that Rgnef protein expression is elevated in Stage 3-4 HGSOC and that Rgnef knockout prevents ovarian tumor spheroid growth in vitro and in vivo. We isolated ascites-associated murine ID8 cells to generate a more aggressive cell line, termed ID8-IP. ID8-IP cells exhibit higher Rgnef and FAK expression than parental ID8 cells. CRISPR/Cas9-induced knockout of Rgnef in ID8-IP cells does not alter 2D growth as compared to Rgnef-KO cells re-expressing GFP-Rgnef. However, Rgnef loss significantly decreased growth as spheroids in a 3D Matrigel-on-Top assay. At five weeks following intraperitoneal injection into syngeneic C57Bl/6 mice, ID8-IP Rgnef-KO cells form significantly fewer ascites-associated cells, as well as fewer metastatic lesions on the peritoneal wall. Notably, ID8-IP Rgnef-KO cells display lower FAK and ERK1/2 phosphorylation. These studies demonstrate that Rgnef loss impedes metastatic growth in the peritoneal cavity, and suggest that an integrin-mediated Rgnef-FAK linkage facilitates ovarian tumor metastasis.

Citation Format: Elizabeth G. Kleinschmidt, Isabelle Tancioni, Kristin Taylor, Carlos Osterman-Diaz, Nichol L. G. Miller, Shulin Jiang, David D. Schlaepfer. Rgnef (p190RhoGEF/Arhgef28) loss impairs ovarian tumor metastatic growth. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr B47.

Abstract 1991: Vulnerability of platinum-resistant ovarian cancer to FAK inhibition

Platinum (CP)-resistant ovarian cancer (OC) has few effective treatment options. Adaptive chemotherapy resistance occurs in part through cancer stem cell (CSC) generation. Wnt/beta-catenin signaling is a driver of CSC survival via induction of gene expression, including aldehyde dehydrogenase (ALDH) enzymes. The gene for focal adhesion kinase (FAK) is commonly amplified in advance-stage OC and this is associated with decreased patient survival. How FAK is activated in OC and whether this is connected to CSC survival is unknown. Here, we find that FAK Y397 phosphorylation (a marker of FAK activation) is increased in non-necrotic Pax8-positive OC tumor tissue after neo-adjuvant chemotherapy compared to paired pre-treatment tumor biopsy samples. FAK activation occurs after CP plus paclitaxel treatment of xenograft tumors, within 60 min of CP treatment of OC cells, and FAK Y397 levels are constitutively-elevated in OC cells pre-adapted to exhibit elevated CP resistance. Pharmacological FAK inhibition (VS-4718, 0.1 µM) selectively prevented CP-resistant tumorsphere formation in vitro and combined with CP to promote cell apoptosis. Combinatorial VS-4718, CP, and paclitaxel chemotherapy exhibited additive inhibitory effects in preventing CP-resistant tumor growth in mice. VS-4718 monotherapy of tumor-bearing mice reduced tumor-associated ALDH activity and resulted in an 85-fold reduction in secondary tumors formed in limiting dilution assays. CRISPR-mediated FAK knockout in OVCAR3 cells combined with stable re-expression of FAK wildtype or a kinase-inactive FAK (K454R) mutant revealed that intrinsic FAK activity was essential for beta-catenin activation, ALDH-1A1 expression, and OVCAR3 tumorsphere growth. As activated constructs of beta-catenin but not YAP1 rescued FAK KO OVCAR3 phenotypes, these studies provide important insights into a FAK signaling linkage to beta-catenin in promoting CSC survival and adaptive resistance to CP chemotherapy. These studies provide the foundational support for a Phase I-II clinical trial for treatment of recurrent platinum-resistant ovarian cancer (NCT03287271) termed ROCKIF: Re-sensitization of carboplatin-resistant Ovarian Cancer by Kinase Inhibition of FAK. As FAK is activated in tumor cells surviving carboplatin-paclitaxel chemotherapy, co-targeting of this FAK/beta-catenin adaptive resistance pathway may expose a vulnerability of CP-resistant tumors.

Citation Format: Carlos J. Diaz Osterman, Lisa M. Bean, Florian J. Sulzmaier, Kristin N. Taylor, Shulin A. Jiang, Isabelle Tancioni, Kristen Anderson, Christine Jean, Xiao Lei Chen, Elizabeth G. Kleinschmidt, Vihren N. Kolev, David T. Weaver, Jonathan A. Pachter, Denise C. Connolly, Alfredo Molinolo, David D. Schlaepfer. Vulnerability of platinum-resistant ovarian cancer to FAK inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1991.

Abstract TMEM-027: TARGETING RGNEF (P190RHOGEF/ARHGEF28) IMPAIRS OVARIAN TUMOR INITIATION AND PROGRESSION

Rho GTPase regulatory and integrin signaling pathways are associated with poor high-grade serous ovarian carcinoma (HGSOC) patient survival1. Focal adhesion kinase (FAK) transmits signals from integrins and promotes HGSOC tumor progression through mechanisms involving tumor-stromal cell interactions2. We previously found that the Rho guanine nucleotide exchange factor Rgnef (also named p190RhoGEF or Arhgef28) activates FAK as well as RhoA GTPase activity in mouse fibroblasts3. Here we find that Rgnef protein expression is elevated in Stage 3-4 HGSOC and that Rgnef knockout prevents spontaneous ovarian tumor formation in the MISIIR-T-antigen (TAg) induced C57BL/6 mouse model. At 17 weeks, Rgnef-/-;TAg ovarian tumors were significantly smaller (p<0.001) than Rgnef+/+;TAg controls. Primary Rgnef-/-;TAg and Rgnef+/+;TAg tumor cells were isolated and expanded ex vivo. Although loss of Rgnef did not alter growth as 3D spheroids, Rgnef-/-;TAg orthotopic (ovarian bursa) and intraperitoneal tumors were significantly smaller (p<0.01) than Rgnef+/+;TAg tumors in MISIIR-TAg-Low C57BL/6 syngeneic mice. Notably, FAK activation (as measured by FAK Y397 phosphorylation) was decreased in Rgnef-/-;TAg ascites-associated tumor cells. Together, these studies show that Rgnef loss impedes tumor growth independently of stromal Rgnef status and supports the notion that an Rgnef-FAK signaling linkage facilitates ovarian tumor initiation and progression.

1.Zhang, H., et al. Integrated Proteogenomic Characterization of Human High-Grade Serous Ovarian Cancer. Cell 166 (2016).

2.Sulzmaier, F.J., Jean, C. & Schlaepfer, D.D. FAK in cancer: mechanistic findings and clinical applications. Nat. Rev. Cancer 14, 598-610 (2014).

3.Miller, N.L., et al. A non-canonical role for Rgnef in promoting integrin-stimulated focal adhesion kinase activation. J. Cell Sci. 126, 5074-5085 (2013).

Citation Format: Elizabeth G. Kleinschmidt, Nichol L.G. Miller, Isabelle Tancioni, Denise C. Connolly, David D. Schlaepfer. TARGETING RGNEF (P190RHOGEF/ARHGEF28) IMPAIRS OVARIAN TUMOR INITIATION AND PROGRESSION [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr TMEM-027.

Abstract NTOC-106: FAK INHIBITION RE–SENSITIZES PLATINUM–RESISTANT SEROUS OVARIAN CANCER

Most ovarian cancer patients respond well to surgical debulking and platinum-taxol chemotherapy. However, ~80% of patients with a complete response to therapy will exhibit tumor recurrence, and in time develop platinum and chemotherapy-resistant disease. It is hypothesized that recurrent disease emanates from the regrowth of microscopic clusters of chemotherapy-resistant tumor cells - also termed cancer stem cells (CSCs). Here, we find that cisplatin chemotherapy elevates focal adhesion (FAK) tyrosine kinase phosphorylation (Y397 FAK) in 3D ovarian tumor spheroids. Notably, FAK is not known as a DNA-damage sensing kinase. Instead, FAK is linked to integrin adhesion-, migration-, and CSC-promoting signaling pathways. In mouse tumors, CP-taxol chemotherapy increases FAK Y397 phosphorylation and aldehyde dehydrogenase (ALDH-1A1, a known markers of CSCs) in tumor areas not associated with necrosis. FAK Y397 phosphorylation is constitutively-elevated in CP-resistant ovarian cancer cells and nanomolar levels of FAK inhibitor (VS-4718) block 3D colony cell growth. Oral VS-4718 administration to mice reduces CP-resistant orthotopic tumor burden with a concomitant decrease in tumor-associated ALDH activity and secondary tumor-initiating capacity. CRISPR-mediated FAK knockout or VS-4718 treated ovarian carcinoma cells exhibit diminished ALDH-1A1 expression. Importantly, co-administration of VS-4718 enhances the anti-tumor effectiveness of CP-taxol chemotherapy in an orthotopic CP-resistant mouse tumor model. As CP activates FAK and FAK signaling sustains ovarian carcinoma CSC phenotypes, our results support the future testing of FAK inhibitors in combination with CP to prevent recurrent and chemo-resistant ovarian cancer.

Citation Format: Lisa M. Bean, Florian J. Sulzmaier, Kristen M. Anderson, Isabelle Tancioni, Cheyenne R. Butcher, Sean Uryu, Christine Jean, Christine Lawson, Xiao Lei Chen, Elizabeth G. Kleinschmidt, Vihren N. Kolev, Jonathan A. Pachter, Dwayne G. Stupack, and David D. Schlaepfer. FAK INHIBITION RE–SENSITIZES PLATINUM–RESISTANT SEROUS OVARIAN CANCER [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr NTOC-106.

Focal adhesion kinase signaling in unexpected places

Focal adhesion kinase (FAK) is a cytoplasmic protein-tyrosine kinase first identified at extracellular matrix and integrin receptor cell adhesion sites and is a key regulator of cell movement. FAK is activated by a variety of stimuli. Herein, we discuss advances in conformational-associated FAK activation and dimerization mechanisms. Additionally, new roles have emerged for FAK signaling at cell adhesions, adherens junctions, endosomes, and the nucleus. In light of these new findings, we review how FAK activation at these sites is connected to the regulation of integrin recycling-activation, vascular permeability, cell survival, and transcriptional regulation, respectively. Studies uncovering FAK signaling connections in unexpected places within cells have yielded important new regulatory insights in cell biology.

FAK activity protects nucleostemin in facilitating breast cancer spheroid and tumor growth

Introduction

Focal adhesion kinase (FAK) controls cell growth and survival downstream of integrin-matrix receptors. Upon adhesion loss or FAK inhibition, FAK can translocate to the nucleus. The nucleolus is a non-membrane nuclear structure that regulates ribosome biogenesis and cell proliferation. Nucleostemin (NS), a nucleolar-localized protein, modulates cell cycle progression, stemness, and three-dimensional tumor spheroid formation. The signaling pathways that regulate NS levels in tumors remain undefined.

Methods

Human breast carcinoma cells were evaluated for growth in culture (adherent and anchorage-independent spheroid) and as orthotopic tumors. FAK signaling was evaluated by pharmacological FAK inhibitor addition (PF-271, IC50 ~ 0.1 μM) and by small hairpin RNA (shRNA) knockdown followed by re-expression of FAK wildtype (WT) or a kinase-dead (KD, K454R) FAK point mutant. Immunoblotting was used to evaluate FAK, NS, nucleolar phosphoprotein B23, and nucleolin levels. Total and phosphospecific antibody imunoblotting were used to detect changes in FAK, Akt kinase (Akt also known as protein kinase B), and 4E-binding protein 1 (4E-BP1) phosphorylation, a translation repressor protein and target of the mammalian target of rapamycin (mTOR) complex. Immunohistochemical, co-immunoprecipitation, and cellular fractionation analyses were used to evaluate FAK association with nucleoli.

Results

Pharmacological (0.1 μM PF-271) or genetic inhibition of FAK activity prevents MDA-MB-231 and 4T1L breast carcinoma growth as spheroids and as orthotopic tumors. FAK inhibition triggers proteasome-mediated decreased NS levels but no changes in other nucleolar proteins such as B23 (nucleophosmin) or nucleolin. Active FAK was associated with purified nucleoli of anchorage-independent cells and present within nucleoli of human invasive ductal carcinoma tumor samples. FAK co-immunoprecipitated with B23 that binds NS and a complex between FAK, NS, Akt, and mTOR was detected. Constitutively-active Akt kinase promoted tumor spheroid growth, stabilized NS levels, and promoted pS65 4E-BP1 phosphorylation in the presence of inhibited FAK. Rapamycin lowered NS levels and inhibited pS65 4E-BP1 phosphorylation in cells with activated Akt-mTOR signaling.

Conclusions

FAK signaling occurs in the nucleolus, active FAK protects NS, and Akt-mTOR pathway regulates NS protein stability needed for breast carcinoma spheroid and tumor growth.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-015-0551-x) contains supplementary material, which is available to authorized users.

RhoGEFs in cell motility: novel links between Rgnef and focal adhesion kinase

Rho guanine exchange factors (GEFs) are a large, diverse family of proteins defined by their ability to catalyze the exchange of GDP for GTP on small GTPase proteins such as Rho family members. GEFs act as integrators from varied intra- and extracellular sources to promote spatiotemporal activity of Rho GTPases that control signaling pathways regulating cell proliferation and movement. Here we review recent studies elucidating roles of RhoGEF proteins in cell motility. Emphasis is placed on Dbl-family GEFs and connections to development, integrin signaling to Rho GTPases regulating cell adhesion and movement, and how these signals may enhance tumor progression. Moreover, RhoGEFs have additional domains that confer distinctive functions or specificity. We will focus on a unique interaction between Rgnef (also termed Arhgef28 or p190RhoGEF) and focal adhesion kinase (FAK), a non-receptor tyrosine kinase that controls migration properties of normal and tumor cells. This Rgnef-FAK interaction activates canonical GEF-dependent RhoA GTPase activity to govern contractility and also functions as a scaffold in a GEF-independent manner to enhance FAK activation. Recent studies have also brought to light the importance of specific regions within the Rgnef pleckstrin homology (PH) domain for targeting the membrane. As revealed by ongoing Rgnef-FAK investigations, exploring GEF roles in cancer will yield fundamental new information on the molecular mechanisms promoting tumor spread and metastasis.

Abstract 3157: An Rgnef (p190RhoGEF/Arhgef28) signaling axis regulates ovarian cancer progression

Ovarian cancer is a leading cause of cancer death in women, is usually diagnosed in late stage, and currently has insufficient effective targeted therapies. The primary mode of metastasis is unique in that dissemination occurs via tumor cell shedding into the peritoneal cavity, survival and growth within ascites, and re-adhesion and proliferation of tumor cells at sites within the abdomen. Therefore, molecules and pathways involving cell adhesion and survival in non-adherent environments are of particular interest. Rgnef (p190RhoGEF/Arhgef28) is a Rho family guanine exchange factor that associates with focal adhesion kinase (FAK) and functions both as a downstream target of FAK tyrosine kinase activity and a regulator of FAK activity following integrin stimulation. FAK regulates cell adhesion, migration, and survival. Expression of FAK is associated with poor clinical outcome, its activity (as measured by FAK Y397 phosphorylation) is frequently increased in serous ovarian carcinomas, and it is currently under investigation as a therapeutic target in ongoing clinical trials. Immunohistochemical analysis of human tumor tissue arrays with antibodies specific for Rgnef and FAK pY397 reveal a positive correlation between Rgnef expression and FAK activation and increased stage/grade of serous-type ovarian cancer. Stable knockdown of Rgnef in human ovarian carcinoma cells grown as subcutaneous or intraperitoneal xenografts in mice suggest that Rgnef may play roles in both primary tumor growth and ascites-associated cell survival and spread. Here, we use a transgenic model of spontaneous ovarian cancer (MISIIR-T-Antigen) to test the role of Rgnef in ovarian cancer progression. Female Rgnef+/+;TAg+ and Rgnef-/-;TAg+ mice were monitored by ultrasound imaging from age 12 to 17 weeks before euthanasia. Rgnef-/-;TAg+ tumors were significantly smaller (p=0.0006) and contained fewer Ki67 positive cells than Rgnef+/+;TAg+ controls at 17 weeks. Tumors and ovarian carcinoma cells isolated from Rgnef-/-;TAg+ mouse ascites have reduced FAK pY397 and increased E-cadherin expression compared to controls, suggesting that loss of Rgnef results in a less aggressive tumor phenotype. These findings identify Rgnef as a component in signaling pathways promoting FAK activation and regulating ovarian tumor progression.

Citation Format: Nichol L. G. Miller, Isabelle Tancioni, Sean Uryu, Elizabeth G. Kleinschmidt, Denise C. Connolly, David D. Schlaepfer. An Rgnef (p190RhoGEF/Arhgef28) signaling axis regulates ovarian cancer progression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3157. doi:10.1158/1538-7445.AM2014-3157

A non-canonical role for Rgnef in promoting integrin-stimulated focal adhesion kinase activation

Rgnef (also known as p190RhoGEF or ARHGEF28) is a Rho guanine-nucleotide-exchange factor (GEF) that binds focal adhesion kinase (FAK). FAK is recruited to adhesions and activated by integrin receptors binding to matrix proteins, such as fibronectin (FN). Canonical models place Rgnef downstream of integrin-FAK signaling in regulating Rho GTPase activity and cell movement. Herein, we establish a new, upstream role for Rgnef in enhancing FAK localization to early peripheral adhesions and promoting FAK activation upon FN binding. Rgnef-null mouse embryo fibroblasts (MEFs) exhibit defects in adhesion formation, levels of FAK phosphotyrosine (pY)-397 and FAK localization to peripheral adhesions upon re-plating on FN. Rgnef re-expression rescues these defects, but requires Rgnef-FAK binding. A mutation in the Rgnef pleckstrin homology (PH) domain inhibits adhesion formation, FAK localization, and FAK-Y397 and paxillin-Y118 phosphorylation without disrupting the Rgnef-FAK interaction. A GEF-inactive Rgnef mutant rescues FAK-Y397 phosphorylation and early adhesion localization, but not paxillin-Y118 phosphorylation. This suggests that, downstream of FN binding, paxillin-pY118 requires Rgnef GEF activity through a mechanism distinct from adhesion formation and FAK activation. These results support a scaffolding role for Rgnef in FAK localization and activation at early adhesions in a PH-domain-dependent but GEF-activity-independent manner.

[Evaluation of nasal mucociliary clearance with a modified saccharin test]

To measure the complex nasal clearance we propose to perform our variation of the Andersen saccharin method as a saccharin liquid test (SLT). The application of 3 molar aqueous sodium saccharin solutions with a Wiretrol capillary on the concha nasalis inferior or media allows simple handling, exact dosage, minimal nasal irritation and an increase in reproducibility. Application of 1 microlitre is sufficient to carry out the test. In the present study 48 healthy volunteers without any nose disease or history of sinusitis showed a saccharin transport rate of 10.4 (SD 4.2) minutes.

[Threshold for electric stimulation of taste in diabetes mellitus]

This paper informs about the electrogustometrically determined stimulus-threshold of gustation in 82 patients with diabetes mellitus in comparison with a group of 107 non-diabetics without disturbance of gustation. The stimulation of the tongue was performed with a unipolar electrode switches as a cathode. The electric impulse was measured in microA and the threshold was found to increase with age, in general. In both groups the thresholds tend to higher values in males in contrast to females as well as smokers opposed to non-smokers. With references to the control group the diabetics showed higher values in the electric taste threshold (statistically significant with P = 0.1%). It was noticed that in the diabetics at the tip of the tongue a higher threshold was present than at the margins of the tongue, being in the inverse ratio to the control group and to normal.

[Olfactometric results of the olfactory function in diabetics]

Olfacto-odorimetrical examinations in 110 diabetics resulted in comparison to an examined control group of 110 rhinologically healthy non-diabetics (patients of an ENT-outpatient department) in olfactory disturbances in the sense of a quantitative dysosmia. The percental ratio of the patients with normosmia to patients with dysosmia in the entire group of diabetics was 23.6 : 76.4 in comparison to 58.2 : 41.8 in the non-diabetics. After the chi2-test the result was a significant difference between the two groups. In the diabetics as well as in the control group a decrease of the olfactory function with growing age which was shown in an increase of the olfactory perceptual threshold could be statistically ascertained. Clear connections between olfactory ability on the one hand and sex, number of births in women, smoker habits, blood sugar content and content of urinary sugar, kind of medication, relative metabolic condition, concomitant diseases and duration of diabetes on the other hand could not be established.

[Determination of the perilymph density in the cochlea of guinea pigs (author's transl)]

The perilymph density of the sc. tympani, sc. vestibuli and the density of liquor cerebrospinalis in guinea-pigs are measured by determination from mass and volume of the fluid column in a glass capillary tube. For the density of perilymph in sc. vest. a value of (formula: see text) in sc. tymp. a value of (formula: see text), and for liquor a value of (formula: see text) was obtained.

[Functional study on the sense of smell in patients with chronic liver disease]

In olfacto-odorimetrical examinations of 32 patients with chronic liver diseases (18 female and 14 male patients at the age of 23 to 77 years) 13 patients with a disturbed olfactory function were found. With one exclusion these patients suffered from liver cirrhosis. On the basis of the anamnesis in 10 of these patients a causal connection between disturbance of smelling and liver disease could be assumed. Out of this group with chronic active hepatitis of 10 patients only 1 patient had a disturbed olfactory function. In 8 patients with disturbed olfactory function suffering from liver cirrhosis a comparison of the olfactometrical findings with activity of GOT and GPT in the serum and the serum bilirubin content showed a correlation between possibilitiy of smelling and serum bilirubin level. Possible causes of appearing olfactory disturbances are demonstrated in short.

[Protein study on perilymph susbstitution during cerebrospinal fluid flow through cochlear aqueduct]

Total protein contents in the perilymphy of Scala vestibuli and Scala tympani as well as in the cerobrospinal fluid (CSF) of guinea-pigs were determined, by which specimens were taken under the following various conditions: With or without subarachnoidal puncture before perilymph collection, by varying the amount of perilymph taken from Scala tympani, by fractionating collection and under post mortem condition. The results suggest that under physiological conditions the CSF also flows through the cochleae aqueduct and the protein concentration in the Scala tympani decreases especially in the basal winding. Because the protein content in CSF is inaverage four times lower than in fluids of the inner ear it is of preference to consider the question of connection between the CSF and the fluids of the inner ear. In the specimens taken the blood contamination was estimated on the basisof erythrocytes in the connection capillaries under microscope. The protein content in the perilymph of Scala vestibuli was found significantly higher in relation to perilymph of Scala tympani.