INHIBITION OF TMEM16A BY BENZBROMARONE OR NICLOSAMIDE FOR TREATING POLYCYSTIC KIDNEY DISEASE AND/OR POLYCYSTIC LIVER DISEASE

Abstract

The present invention relates to a compound for use in a method of treating a pathological condition selected from polycystic kidney disease, polycystic liver disease, and a combination thereof. The present invention further relates to a composition for use in a method of treating a pathological condition selected from polycystic kidney disease, polycystic liver disease, and a combination thereof.

Claims

1. A method of treating and/or preventing a pathological condition selected from polycystic kidney disease, polycystic liver disease, and a combination thereof, wherein said method comprises administering a compound which is a TMEM16 inhibitor selected from benzbromarone, niclosamide, and pharmaceutically acceptable salts thereof, to a patient in need thereof.

2. The method according to claim 1, wherein said pathological condition is a combination of polycystic kidney disease and polycystic liver disease.

3. The method according to claim 1, wherein said pathological condition is characterized by cyst development.

4. The method according to claim 1, wherein said pathological condition is characterized by increased TMEM16A expression and/or increased TMEM16F expression.

5. The method according to claim 1, wherein said polycystic kidney disease is autosomal dominant polycystic kidney disease (ADPKD) or autosomal recessive polycystic kidney disease (ARPKD).

6. The method according to claim 1, wherein said compound is capable of inhibiting renal cyst growth and/or hepatic cyst growth by inhibiting TMEM16A and/or TMEM16F.

7. The method according to claim 1, wherein said compound is administered in an amount of from 10 mg per day to 800 mg per day.

8. The method according to claim 1, wherein said compound is administered once every 4-8 h, once daily, or once weekly.

9. The method according to claim 1, wherein said compound is administered to a patient in need thereof, wherein said patient is a mammal, preferably a human.

10. The method according to claim 1, wherein said compound is administered topically or systemically.

11. The method according to claim 1, wherein said compound is administered intravenously, intravascularly, orally, intraarticularly, nasally, mucosally, intrabronchially, intrapulmonarily, intrarenally, intrahepatically, intradermally, subcutaneously, intramuscularly, intraocularly, intrathecally, or intranodally.

12. The method according to claim 1, wherein said compound is co-administered with an agent selected from an antihypertensive agent, an antiinfective agent, an antibiotic agent, an analgesic agent, a vasopressin antagonist such as tolvaptan, a somatostatin analogue such as octreotide, and an mTOR antagonist such as sirolimus or everolimus.

13. The method according to claim 1, wherein said compound is a biologically active derivative of benzbromarone or a biologically active derivative of niclosamide.

14. The method according to claim 1, wherein said compound is administered as a composition wherein said composition comprises said compound and a pharmaceutically acceptable excipient.

15. The method according to claim 14, wherein said composition further comprises any of an antihypertensive agent, an antiinfective agent, an antibiotic agent, an analgesic agent, a vasopressin antagonist such as tolvaptan, a somatostatin analogue such as octreotide, an mTOR antagonist such as sirolimus or everolimus, a disintegrant, and a pharmaceutically acceptable carrier.

16. The method according to claim 4, wherein said pathological condition is characterized by increased TMEM16A expression in kidney cells.

17. The method according to claim 5, wherein said polycystic kidney disease is ADPKD.

18. The method according to claim 7, wherein said compound is administered in an amount of from 40 mg to 600 mg per day.

19. The method according to claim 8, wherein said compound is administered once daily.

20. The method according to claim 9, wherein said patient is a human.

21. The method according to claim 11, wherein said compound is administered orally.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0050] The present invention is now further described by reference to the following figures.

[0051] All methods mentioned in the figure descriptions below were carried out as described in detail in the examples.

[0052] FIG. 1 shows that TMEM16A augments Ca.sup.2+ signaling and ion transport in MDCK cells.

[0053] A) RT-PCR indicating expression of TMEM16A in MDCK-C7 cells but not in MDCK-M2 cells.

[0054] B) Summary of basal Ca.sup.2+ levels in MDCK-C7 and MDCK-M2 cells.

[0055] C,D) ATP or UTP induced peak and plateau Ca.sup.2+ levels (both 100 μM).

[0056] E) Original recordings and summary of ATP or UTP induced transepithelial voltages and effect of TMEM16A-knockout.

[0057] F,G) Effect of siRNA on expression of TMEM16A and TMEM16F, respectively, as assessed by semiquantitative RT-PCR.

[0058] Mean±SEM (number of cells measured). #significant difference when compared to C7 and scrambled, respectively.

[0059] FIG. 2 shows the role of TMEM16A in plasma membrane and primary cilium of MDCK cells.

[0060] A) Acetylated tubulin (red/upper panel) and TMEM16A (green/lower panel) in a primary cilium of MDCK cells.

[0061] B) Ca.sup.2+ sensor 5-HT6-G-GECO1 expressed in the primary cilium and near plasma membrane allowing measurement of Ca.sup.2+ in both compartments.

[0062] C,D) Original recordings and summary of Ca.sup.2+ signals elicited by stimulation with ATP or UTP (both 100 μM) in primary cilium and near plasma membrane.

[0063] E,F) Increase of Ca.sup.2+ in the absence of extracellular Ca.sup.2+.

[0064] G,H) Comparison of purinergic Ca.sup.2+ increase in MDCK-C7 (expressing TMEM16A) and MDCK-M2 (not expressing TMEM16A). Bars=2 μm.

[0065] Mean±SEM (number of cells measured). #significant difference when compared to membrane (p<0.05; unpaired t-test). §significant difference when compared to MDCK-C7 (p<0.05; unpaired t-test).

[0066] FIG. 3 shows a M1 renal organoid and cyst model.

[0067] A) RT-PCR analysis of mRNA expression of ion channels TMEM16A, TMEM16F, αβγ-ENaC (abg-Scnn1), and PKD1, as well as PKD2, and the receptor patched 1,2 (Ptch1,2). Similar expression patterns were found in mouse kidney and the collecting duct cell line M1. +/− indicate presence/absence of reverse transcriptase.

[0068] B) Growth of renal organoid in matrigel within 9 days. Bars=20 μm.

[0069] C) Reconstructed 3D image from a renal M1 organoid. Bars=20 μm.

[0070] D,E) Differential interference contrast (DIC) image and immunocytochemistry of a cross-section of an organoid. Green/light gray, primary cilia; red/medium gray, CFTR; blue/dark gray, DAPI. Bars=20 μm.

[0071] F) M1 organoid (middle) and cystic expansion by shRNA knockdown of PKD1 and PKD2. Bumetanide (100 μM) was continuously present in matrigel, indicating contribution of fluid secretion to cyst development (in shPKD1 and shPKD2 treated cells), which is absent in M1 renal organoids. Bars=50 μm.

[0072] G) Increase in volume during 9 days of organoid/cyst growth in matrigel and inhibition of cyst growth by bumetanide.

[0073] H) Increase in proliferative activity in shPKD1 and shPKD2 treated cells, as indicated by Ki-67 staining.

[0074] Bars=20 vtm. Mean±SEM (number of organoids measured). #significant difference when compared with scrambled (p<0.05; unpaired t-test). §significant difference when compared to absence of bumetanide (p<0.05; unpaired t-test).

[0075] FIG. 4 shows increased proliferation by knockdown of PKD1 or PKD2.

[0076] A) Ki-67 staining (red/medium gray) indicating increase in proliferation and enhanced expression of TMEM16A (green/light gray) in M1 cysts caused by knockdown of PKD1 or PKD2.

[0077] B) Western blot indicating small hairpin (sh) RNA-knockdown of PKD1 and PKD2, respectively.

[0078] C,D) Increase in cyst volume and proliferation upon knockdown of PKD1/PKD2, and inhibition by 5 μM benzbromarone or CaCCinhA01.

[0079] Bars=20 μm. Mean±SEM (number of organoids measured). #significant difference when compared control (p<0.05; ANOVA). §significant difference when compared to scrambled (p<0.05; ANOVA).

[0080] FIG. 5 shows induction of Cl.sup.− secretion by knockdown of PKD1 or PKD2.

[0081] A,B) Ussing chamber recordings on M1 cells of polarized grown permeable supports (2D culture). Enhanced Cl.sup.− secretion by luminal stimulation of ATP (100 μM) or forskolin/IBMX (IF; 2 μM/100 μM) in monolayers lacking expression of PKD1 or PKD2.

[0082] C-E) Summaries for calculated basal short circuit currents (I.sub.sc) and I.sub.sc activated by ATP and forskolin/IBMX, respectively.

[0083] Mean±SEM (number of organoids measured). #significant difference when compared control (p<0.05; ANOVA). §significant difference when compared to scrambled (p<0.05; ANOVA).

[0084] FIG. 6 shows upregulation of TMEM16A is essential for enhanced Ca.sup.2+ signaling upon knockdown of PKD1 and PKD2.

[0085] A) Western blot indicating siRNA-knockdown of TMEM16A in M1 collecting duct cells.

[0086] B-D) Original recordings and summaries of basal Ca.sup.2+ and ATP (100 μM) induced Ca.sup.2+ increase (Fura2) in control cells (scrbld), and cells with a knockdown of PKD1 or PKD2, respectively.

[0087] E,F) Original recordings and summaries of ATP-induced Ca.sup.2+ increase in cells lacking expression of TMEM16A (siT16A).

[0088] G) Expression of TMEM16A in M1 control cells (scrbld) and cells lacking expression of PKD1 or PKD2.

[0089] H-J) Original recordings and summaries of the effect of ATP on ER Ca.sup.2+ levels in control cells and cells lacking expression of PKD1 or PKD2.

[0090] K) Attenuated ATP-induced Ca.sup.2+ release after knockdown of TMEM16A. Bars=20 μm.

[0091] Mean±SEM (number of monolayers measured). #significant difference when compared scrbld (p<0.05; ANOVA). §significant difference when compared to control (p<0.05; ANOVA).

[0092] FIG. 7 shows that TMEM16A is essential for enhanced Ca.sup.2+ store release by knockdown of PKD1 and PKD2.

[0093] A,B) Lack of effects of caffeine on intracellular Ca.sup.2+ and lack of expression of RyR1-3 in mouse primary renal medullary and M1 collecting duct cells.

[0094] C,D) CPA (10 μM) induced store release in the presence or absence PKD1/PKD2.

[0095] E,F) CPA-induced store release was strongly attenuated by siRNA-knockdown of TMEM16A.

[0096] G-J) Original recordings and summaries of CPA-induced Ca.sup.2+ store release and SOCE in the presence of SK&F96365 and YM58483 (both 5 μM).

[0097] Mean±SEM (number of monolayers measured). #significant difference when compared scrbld (p<0.05; ANOVA). §significant difference when compared to absence of siT16A or SK&F96365/YM58483, repectively (p<0.05; ANOVA).

[0098] FIG. 8 shows the contribution of TMEM16A to augmented Ca.sup.2+ signaling in ADPKD.

[0099] Proposed model suggesting cellular mislocalization of PKD2 and PKD1 in the ER, and upregulation/mislocalization of TMEM16A, upon knockout of PKD1 and PKD2, respectively. Ca.sup.2+ increase upon purinergic (P2Y) receptor stimulation is enhanced by knockout of PKD1/PKD2. TMEM16A strongly contributes to enhanced Ca.sup.2+ signals probably by tethering IP.sub.3R to the plasma membrane and/or by operating as a counter-ion channel to compensate Ca.sup.2+-diffusion potentials.

[0100] FIG. 9 shows the effect of the TMEM16A-blocker benzbromarone on cyst development in ADPKD. The experiments were performed with PKD1−/− mice. Benzbromarone significantly inhibits cyst growth.

[0101] FIG. 10 shows the inhibition of pathologic cell proliferation in ADPKD (PKD1−/− mice) by treatment with the TMEM16A—blocker benzbromarone.

[0102] FIG. 11 shows that niclosamide and nitazoxanide inhibit cyst growth in a dose-dependent manner. Polycystin-1-deficient collecting duct (plMDCK) cells were resuspended within a collagen I matrix where they spontaneously form cysts and grow in a secretion-dependent manner in the presence of 10 μM forskolin for 5 days. Medium was supplemented with either 0.1 μM or 1 μM niclosamide or 0.1 μM or 1 μM nitazoxanide. Thereafter, cyst volumes were analyzed. A) Mean cyst volumes±SEM (control=set 100%) from three individual experiments comprising the analysis of 310-330 cysts per condition. B) Photos show representative cysts at day 5. * significant compared to control. § significant compared to 0.1 μM niclosamide. # significant compared to 0.1 μM nitazoxanide. It is shown that niclosamide and niclosamide derivative nitazoxanide inhibit cyst growth in vitro.

[0103] In the following, reference is made to the examples, which are given to illustrate, not to limit the present invention.

EXAMPLES

Example 1

[0104] In the following, materials and methods are described that were used for obtaining the results presented in the further examples.

[0105] Cells, Virus Production RT-PCR, cDNA:

[0106] MDCK M2 and C7 cell lines were cultured in DMEM supplemented with 10% Fetal Bovine Serum (FBS). M1 cells were cultured DMEM/F12 medium supplemented with 5% (v/v) fetal bovine serum (FBS), 1% Insulin-Transferrin-Selenium boox (ITS), and 1% L-Glutamine 200 mM (all from Capricorn Scientific GmbH, Ebsdorfergrund, Germany) at 37° C. in a humidified incubator in 5% (v/v) CO.sub.2. M1 cells were transduced to downregulate Pkd1 and Pkd2. Cells were infected with lentiviral recombinant vectors containing the shRNAs of mouse Pkd1 (5′-GAATATCGGTGGGAGATAT; SEQ ID NO. 1) and Pkd2 (5′-GCATCTTGACCTACGGCATGA, SEQ ID NO. 2) with YFP.sub.I152L, as previously described. Stable transfected M1 cells were maintained in the presence of 5 μg/ml of Puromycin (Thermo Fisher Scientific, Darmstadt, Germany).

[0107] For semi-quantitative RT-PCR total RNA from M1 cells, MDCK cells and murine kidney were isolated using NucleoSpin RNA II columns (Macherey-Nagel, Duren, Germany). Total RNA (1 μg/50 μl reaction) was reverse-transcribed using random primer (Promega, Mannheim, Germany) and M-MLV Reverse Transcriptase RNase H Minus (Promega, Mannheim, Germany). Each RT-PCR reaction contained sense (0.5 μM) and antisense primer (0.5 μM) (table 1), 0.5 μl cDNA and GoTaq Polymerase (Promega, Mannheim, Germany). After 2 min at 95° C. cDNA was amplified (30 cycles) for 30 s at 95° C., 30 s at 57° C. and 1 min at 72° C. PCR products were visualized by loading on peqGREEN (Peqlab; Dusseldorf, Germany) containing agarose gels and analysed using ImageJ.

[0108] Western Blotting:

[0109] Protein was isolated from cells using a sample buffer containing 25 mM Tris-HCl, 150 mM NaCl, 100 mM dithiothreitol, 5.5% Nonidet P-40, 5% glycerol, 1 mM EDTA and 1% protease inhibitor mixture (Roche, cOmplete, EDTA-free, Mannheim, Germany). Proteins were separated by 7% sodium dodecyl sulfate (SDS) polyacrylamide gel and transferred to a polyvinylidene difluoride membrane (GE Healthcare Europe GmbH, Munich, Germany) or 4-20% Mini-PROTEAN TGX Stain-Free (Bio-Rad) using a semi-dry transfer unit (Bio-Rad). Membranes were incubated with primary anti-Tmem16a rabbit polyclonal antibody (Davids Biotech, Regensburg, Germany; 1:1000), anti-PKD1 (Polycystin-1 (7E12), Santa Cruz; 1:500) mouse antibody or anti-PKD2 (Polycystin-2 (D-3), Santa Cruz; 1:500) mouse antibody, overnight at 4° C. Proteins were visualized using horseradish peroxidase-conjugated secondary antibody and ECL detection. Actin was used as a loading control.

[0110] M1 Organoid Model:

[0111] M1 cells were resuspended as a single-cell suspension in 50/50% Matrigel/type I collagen and transferred into 24-well plates (30×10.sup.3 cells/well, four wells per condition) for 9 days. Medium was changed every 3 days. Every 3 days thirty random visual fields per well were photographed with an Axiovert 200 microscope (Zeiss, Germany). Cyst area of the lumina (˜30-150 cysts per condition and single experimental procedure) were measured with AxioVision (Zeiss, Germany). Cyst volume was then estimated using the formula for the volume of a sphere, 4/3πr.sup.3.

[0112] Immunocytochemistry:

[0113] M1 cells grown under confluent conditions for 4 days on glass coverslips and M1 organoids grown for 6 days were fixed for 10 min with methanol at −20° C. Organoids were isolated with ice cold 5 mM EDTA in PBS and seeded in poly-L-lysine coated coverslips. After seeded, cells were fixed for 10 min with methanol at −20° C. After washing, the cells were permeabilized with 0.5% (v/v, PBS) Triton X-100 for 10 min and blocked with 1% (w/v, PBS) bovine serum albumin for 1 h at room temperature. The cells were incubated overnight with primary antibodies (moo) against rabbit anti-TMEM16A (Davids Biotechnologie, Regensburg, Germany), or rat anti-Ki-67 (DAKO, M7249, Germany) or mouse anti-acetylated tubulin (T7451, Sigma-Aldrich, Germany). Binding of the primary antibody was visualized by incubation with appropriate secondary antibodies conjugated with Alexa Fluor 488 or Alexa Fluor 546 (1:300, Molecular Probes, Invitrogen). Nuclei were stained with Hoe33342 (0.1 g/ml PBS, AppliChem, Darmstadt, Germany). Glass coverslips were mounted on glass slides with fluorescent mounting medium (DakoCytomation, Hamburg, Germany) and examined with an ApoTome Axiovert 200M fluorescence microscope (Zeiss, Germany).

[0114] Cell Proliferation assay:

[0115] M1 cells were plated in 96-well plates at a density of 2×10.sup.3 cells per well for the time duration as indicated (0, 3, 6 and 9 days). Medium was changed every 3 days. Cells were incubated for 2 h in 100 μl of fresh media containing 0.5 mg/ml of the tetrazolium salt MTT. The dark blue formazan product was dissolved with DMSO and the absorbance measured at 595 nm.

[0116] Ussing Chamber:

[0117] MDCK or M1 cells were grown as polarized monolayers on permeable supports (Millipore MA, Germany) for 8 days. Cells were mounted into a perfused micro-Ussing chamber, and the luminal and basolateral surfaces of the epithelium were perfused continuously with Ringer's solution (mmol/l: NaCl 145; KH.sub.2PO.sub.4 0.4; K.sub.2HPO.sub.4 1.6; glucose 5; MgCl.sub.2 1; Ca.sup.2+ gluconate 1.3) at a rate of 5 ml/min (chamber volume 2 ml). Bath solutions were heated to 37° C., using a water jacket. Experiments were carried out under open circuit conditions. In addition, 100 μM ATP/UTP were added on the apical or basolateral side, or 100 μM 3-isobutyl-1-methylxanthine and 2 μM Forskolin (I/F) were added on the basolateral side, or 2 μM Ionomycin were added on the apical side, as indicated in the figure. Data were collected continuously using PowerLab (AD Instruments, Australia). Values for transepithelial voltages (V.sub.te) were referred to the basolateral side of the epithelium. Transepithelial resistance (R.sub.te) was determined by applying short (1 s) current pulses (ΔI=0.5 μA). R.sub.te and equivalent short circuit currents (I.sub.′SC) were calculated according to Ohm's law (R.sub.te=ΔV.sub.te/ΔI, I.sub.′SC=V.sub.te/R.sub.te).

[0118] Measurement of [Ca.sup.2+]i:

[0119] Primary cilium and membrane Ca.sup.2+ signals were detected after MDCK M2 and C7 cell were transfected with 5HT6-mCherry-GECO1.0 (5HT6-GECO, Addgene, Cambridge, Mass., USA). Cells were grown to confluence in glass coverslips and serum starved for 4-6 days to induce cilium formation. Afterwards, the cells were mounted and perfused in Ringer's solution. The mCherry fluorescence of the indicator was used to localize the Ca.sup.2+ sensor. Therefore, before each experiment, a photo was taken exciting the 5HT6-GECO at 560 nm, and the emission was recorded between 620±30 nm using a CCD-camera (CoolSnap HQ, Visitron Systems, Germany). To measure the ciliary Ca.sup.2+ changes, 5HT6-GECO was excited at 485/405 nm, and the emission was recorded between 535±12.5 nm. The results for [Ca.sup.2+ ]cilium and [Ca.sup.2+]cyt were obtained at 485/405 nm changes and given in ratio. Measurement of the global cytosolic Ca.sup.2+ changes were performed as described recently. In brief, cells were loaded with 5 μM Fura-2, AM (Molecular Probes) in OptiMEM (Invitogen) with 0.02% pluronic (Molecular Probes) for 1 h at RT and 30 min at 37° C. Fura-2 was excited at 340/380 nm, and the emission was recorded between 470 and 550 nm using a CCD-camera (CoolSnap HQ, Visitron Systems, Germany). Control of experiment, imaging acquisition, and data analysis were done with the software package Meta-Fluor (Universal imaging, USA). [Ca2+].sub.i was calculated from the 340/380 nm fluorescence ratio after background subtraction. The formula used to calculate [Ca.sup.2+].sub.i was [Ca.sup.2+].sub.i=Kd×(R−R.sub.min)/(R.sub.max−R)×(S.sub.f2/S.sub.b2), where R is the observed fluorescence ratio. The values R.sub.max and R.sub.min (maximum and minimum ratios) and the constant S.sub.f2/S.sub.b2 (fluorescence of free and Ca.sup.2+-bound Fura-2 at 380 nm) were calculated using 1 μmol/liter ionomycin (Calbiochem), 5 μmol/liter nigericin, 10 μmol/liter monensin (Sigma), and 5 mmol/liter EGTA to equilibrate intracellular and extracellular Ca.sup.2+ in intact Fura-2-loaded cells. The dissociation constant for the Fura-2.Math.Ca.sup.2+ complex was taken as 224 nmol/liter. ER Ca.sup.2+ signals were detected in Ca.sup.2+ sensor ER-LAR-GECO1 (Addgene, Cambridge, Mass., USA) expressing M1 cells. Cells were excited at 560 nm and emission was recorded between 620±30 nm.

[0120] Materials and Statistical Analysis:

[0121] All compounds used were of highest available grade of purity. Data are reported as mean±SEM. Student's t-test for unpaired samples and ANOVA were used for statistical analysis. p<0.05 was accepted as significant difference.

Example 2

[0122] In the following, results are presented showing the importance of TMEM16A in polycystic kidney disease and/or polycystic liver disease, as well as the potential of TMEM16A inhibitors benzbromarone and/or niclosamide for the treatment of PKD/PLD.

[0123] TMEM16A Augments Fluid Secretion by Increase in Intracellular Ca.sup.2+:

[0124] The impact of TMEM16A on fluid secretion and cyst growth in a MDCK cyst model and in embryonic kidney cultures was described previously by the present inventors. MDCK cells derived from dog principal cells exist as a TMEM16A-expressing MDCK-C7 clone and as a MDCK-M2 clone, which lacks expression of TMEM16A (FIG. 1A). C7 cells show a remarkable increase in intracellular Ca.sup.2+ and a pronounced Cl.sup.− secretion when stimulated with the purinergic receptor agonists ATP (100 μM) or UTP (100 μM) (FIG. 1B-D). SiRNA-knockout of TMEM16A inhibited Cl.sup.− secretion by purinergic receptor stimulation (FIG. 1E). Furthermore, siRNA-knockdown of TMEM16F did not affect Ca.sup.2+ activated Cl.sup.− currents (data not shown; FIG. 1F,G). TMEM16A is expressed in plasma membrane and primary cilium (FIG. 2A). Ca.sup.2+ changes in primary cilium and near the plasma membrane were measured using 5-HT6-G-GECO1 (FIG. 2B). A Ca.sup.2+ rise in both cilium and near plasma membrane was detected upon purinergic receptor stimulation with ATP or UTP (FIG. 2C,D). Purinergic Ca.sup.2+ rise was larger in the primary cilium than close to the plasma membrane, but otherwise qualitatively similar. It was attenuated in MDCK-M2 cells lacking expression of TMEM16A (FIG. 2G,H).

[0125] Loss of PKD1 or PKD2 Induces Cl.sup.− Secretion in M1 Renal Organoids:

[0126] The present inventors examined the role of TMEM16A for Ca.sup.2+ signaling and renal cyst growth, as well as the impact of polycystins in an improved M1 mouse collecting duct model. M1 cells show expression of polycystins (PKD1, PKD2), TMEM16A, TMEM16F, CFTR, and ENaC subunits similar to native mouse medullary kidney cells (FIG. 3A). M1 cells readily produce spherical renal organoids when grown as a 3D culture in matrigel (FIG. 3B,C). The cells appear highly differentiated and form primary cilia (FIG. 3D,E). Importantly, M1 renal organoids do not seem to secrete fluid, because the NKCC1 inhibitor bumetanide did not interfere with the formation of the organoid (FIG. 3F,G). However, they express epithelial Na.sup.+ channels and increase their volume when grown in amiloride (not shown). In contrast, knockdown of either PKD1 or PKD2 increased the organoid volume, and this increase in volume was inhibited by bumetanide, indicating activation of ion secretion upon knockdown of polycystins and induction of a cystic phenotype (FIG. 3F,G, FIG. 4C).

[0127] In a renal organoid model with M1 collecting duct cells, the present inventors found upregulation of TMEM16A with loss of expression of PKD1 or PKD2. TMEM16A supports Ca.sup.2+ store release, cell proliferation and fluid secretion and thereby contributes to cyst growth. TMEM16A therefore contributes to the pathogenic events observed in ADPKD.

[0128] Enhanced Secretion and Proliferation in PKD Requires TMEM16A:

[0129] A hallmark of renal cysts is the upregulation of proliferation. Ki-67 staining in M1 renal organoids caused strong upregulation of proliferation upon knockdown of PKD1 or PKD2 (FIG. 3H). Notably with knockdown of PKD1 or PKD2 and increase in proliferation, expression of TMEM16A was strongly increased (FIG. 4A). Benzbromarone or CaCCinhAO1, two potent inhibitors of TMEM16A, blocked increase in volume and proliferation (FIG. 4A-D). When grown as 2D cultures on permeable supports, cells with knockdown of PKD1 or PKD2 demonstrated larger ATP-activated TMEM16A and cAMP-activated CFTR currents (FIG. 5). The data suggest that enhanced secretion and proliferation caused by knockdown of PKD1 or PKD2 is strongly dependent on TMEM16A.

[0130] Disturbed Ca.sup.2+ Signaling in PKD Relies on TMEM16A:

[0131] Abrogated Ca.sup.2+ signaling in ADPKD has been intensely examined, but controversial results have been reported. The present inventors reported a role of TMEM16A in Ca.sup.2+ signaling, i.e. enhanced agonist-induced Ca.sup.2+-store release by TMEM16A. Herein the present inventors show the impact of TMEM16A on ER Ca.sup.2+-store release through IP.sub.3R and ryanodine receptors (RyR) upon knockdown of PKD1 and PKD2 (FIG. 6A). Knockdown of PKD1 or PKD2 enhanced basal [Ca.sup.2+], and augmented ATP-induced store release (FIG. 6B-D). The enhanced Ca.sup.2+ signals observed in the absence of PKD1 or PKD2 required the presence of TMEM16A, as both basal Ca.sup.2+ levels and ATP-induced store release were strongly attenuated by knockdown of TMEM16A (FIG. 6C-F). Similar to M1-organoids, also M1-monolayers demonstrated lower expression levels for TMEM16A when compared to M1 cells with knockout in PKD1 or PKD2 (FIG. 6G). Using the ER Ca.sup.2+ sensor ER-LAR-GECO1, the present inventors found higher basal ER Ca.sup.2+ levels and enhanced ATP-induced Ca.sup.2+ release in cells lacking expression of PKD1 or PKD2 (FIG. 6H-J). In contrast, knockdown of TMEM16A strongly reduced store filling and ATP-induced Ca.sup.2+-release (FIG. 6K).

[0132] Upregulated TMEIM6A Causes Enhanced ER Store Release and Store Refill in ADPKD:

[0133] Ryanodine receptors (RyR) are inhibited by Polycystin-2 in mouse heart and have been reported to operate as Ca.sup.2+ release channels in cultured human renal epithelial cells. RyR was reported to have an essential role in flow-induced Ca.sup.2+ increase in mouse kidney. However, the activator of RyR, caffeine, did not increase intracellular Ca.sup.2+, and the present inventors did not detect expression of RyR1-3 in mouse wt and PKD1−/− primary renal epithelial and M1 collecting duct cells (FIG. 7A,B). In contrast, signals for RyR1-3 were clearly present in skeletal muscle, heart muscle, and brain, respectively (not shown). The present inventors therefore conclude that RyR are not relevant for changes in Ca.sup.2+ signaling induced by knockout of polycystins in mouse renal epithelial cells. Lack of PKD1 or PKD2 increased store emptying induced by inhibition of SERCA with cyclopiazonic acid (CPA). Moreover, store operated Ca.sup.2+ entry (SOCE) was also enhanced by knockdown of PKD1/PKD2 (FIG. 7C,D). Enhanced store release and enhanced SOCE was strongly reduced in the absence of TMEM16A (FIG. 7E,F). Moreover, the inhibitor of transient receptor potential (TRP) channels SK&F96365 and the ORAL inhibitor YM58483 inhibited enhanced Ca.sup.2+ entry in PKD1/PKD2 knockout cells and abolished enhanced CPA-induced store release (FIG. 7G-J). Taken together the present data demonstrate augmented Ca.sup.2+ signals in the absence of either PKD1 or PKD2. Enhanced Ca.sup.2+ signaling requires the presence of the TMEM16A Cl.sup.− channel, which therefore represents a suitable drug target in ADPKD (FIG. 8).

Example 3

[0134] Aberrant intracellular Ca.sup.2+ signaling, enhanced cell proliferation and fluid secretion are essential factors that drive growth of renal cysts. The present inventors herein demonstrate ATP-induced Ca.sup.2+ increase in both the primary cilium as well as in the cytosol near the plasma membrane of MDCK cells (FIG. 2). Although ciliary Ca.sup.2+ increase by ATP was larger, the responses in the cilium and cytoplasm were similar. The present inventors therefore continued to analyze cytosolic Ca.sup.2+ changes.

[0135] Inhibition of the IP.sub.3 receptors by PKD1 with attenuation of Ca.sup.2+ release from IP.sub.3-sensitive stores has been reported earlier. Accordingly, receptor mediated Ca.sup.2+ release is enhanced with the loss of PKD1. The present inventors show that a lack of PKD1 is likely to augment store operated calcium entry, which was detected in the herein disclosed study (FIG. 7). Enhanced Ca.sup.2+ entry was blocked by the inhibitor of receptor-mediated Ca.sup.2+ entry SK&F96365, and by the inhibitor of store operated ORAI1 Ca.sup.2+ influx channels, YM58483 (FIG. 7). Enhanced (and mislocalized) expression of PKD2 in the ER in the absence of PKD1 is likely to operate as a Ca.sup.2+ activated ER Ca.sup.2+ leakage channel, which will contribute to enhanced Ca.sup.2+ release from IP.sub.3-sensitive (IP.sub.3R) stores (FIG. 8). Notably, abnormal Ca.sup.2+ permeability of the ER membrane in ADPKD may account for both change in apoptotic activity and increased proliferation.

[0136] TMEM16A channels enhance ER-Ca.sup.2+ store release by sequestering the ER and IP3 receptors to Ca.sup.2+ signaling compartments near the plasma membrane. ER-located TMEM16A supports both release of Ca.sup.2+ from intracellular ER-Ca.sup.2+ stores, as well as reuptake of Ca.sup.2+ by the SERCA (FIG. 8). In contrast to earlier reports, the present inventors did not detect expression of RyR channels or effects of caffeine on [Ca.sup.2+].sub.i in mouse primary renal epithelial cells or M1 cells (FIG. 7I,J).

[0137] The expression of TMEM16A being upregulated through activation of STATE (and STAT3) may be the reasons for the upregulation of TMEM16A in M1 cysts observed in the study disclosed herein (FIG. 4A). TMEM16A supports proliferation, cell migration and development of cancer by recruiting a number of intracellular signaling pathways. Conclusively, the present inventors show herein that TMEM16A is a highly potential drug target for treating polycystic kidney disease.

Example 4

[0138] Inhibition of Cyst Growth In Vivo

[0139] Inducible and tubule-specific PKD1 knockout (PKD1−/−) leads to ADPKD and polycystic kidney disease. Wt mice and mice with a knockout in the gene PKD1 were treated with benzbromarone (1 μg/kg/day intraperitoneal (I.P.) benzbromarone (BBR)) for 30 days starting 4 weeks after induction of the PKD1 knockout at postnatal (PN) 20-22. As shown in FIG. 9, treatment with benzbromarone (BBR) for only 4 weeks leads to a remarkable delay in cyst development.

[0140] Cell proliferation was examined in kidneys of control animals (PKD+/+) and PKD1−/− animals using the proliferation marker Ki-67. As shown in FIG. 10, the treatment with the TMEM16A-inhibitor benzbromarone largely abolished pathologic proliferation in ADPKD (PKD1−/− mice).

Example 5

[0141] Polycystic kidney disease (PKD) leads to continuous decline of renal function by growth of renal cysts. Enhanced proliferation and transepithelial chloride secretion through cystic fibrosis transmembrane conductance regulator (CFTR) is observed to cause an increase in cyst volume. Ca.sup.2+ activated Cl.sup.− channel TMEM16A (anoctamin 1) has a pro-proliferative role and TMEM16A contributes to CFTR-dependent Cl.sup.− secretion. The present application demonstrates an increase in intracellular Ca.sup.2+ ([Ca.sup.2+]i) signals and Cl.sup.− secretion by TMEM16A, in renal collecting duct principal cells from dog (MDCK) and mouse (M1). M1 organoids strongly proliferate, increase expression of TMEM16A and secrete Cl.sup.− upon knockdown of endogenous polycystin-1 or -2 (PKD1,2) by retroviral transfection of shRNA directed against PKD1 and PKD2 (shPKD1 and shPKD2), respectively. Knockdown of PKD1 or PKD2 increased basal intracellular Ca.sup.2+ levels and enhanced purinergic/inositol trisphosphate (IP3)-induced Ca.sup.2+ release from endoplasmic reticulum. In contrast, ryanodine receptors were not expressed and caffeine had no effects on [Ca.sup.2+]i. Ca.sup.2+ signals, proliferation and Cl.sup.− secretion were largely reduced by knockdown or blockade of TMEM16A. Thus, the present inventors conclude that TMEM16A is essential for enhanced Ca.sup.2+ release from IP3-sensitive Ca.sup.2+ stores in autosomal dominant polycystic kidney disease (ADPKD). The data suggest TMEM16A as a major pathogenic factor during ADPKD, and thus represents a suitable therapeutic target in polycystic kidney disease.

Example 6

[0142] The effect of niclosamide and derivatives thereof, e.g. nitazoxanide, on cyst growth was analyzed. Particularly, it was analyzed whether there is a dose-dependent effect on cyst growth. Polycystin-1-deficient collecting duct (p1MDCK) cells were resuspended in a collagen I matrix to form cysts in vitro and were cultured in the presence of lovIM forskolin for 5 days. The cells were treated with either 0.1 μM or 1 μM niclosamide, or with 0.1 μM or 1 μM of an exemplary niclosamide derivative, namely nitazoxanide. It was shown (FIG. 11) that the mean cyst volumes were significantly decreased when treated with niclosamide or niclosamide derivative nitazoxanide. Niclosamide and derivative nitazoxanide efficiently inhibit cyst growth in vitro. Furthermore, higher concentrations of niclosamide and niclosamide derivative, namely 1 μM, achieved a higher reduction in cyst volumes than lower concentrations, namely 0.1 μM, of niclosamide and niclosamide derivative. Conclusively, both niclosamide and niclosamide derivative nitazoxanide effectively inhibit cyst growth.

REFERENCES

[0143] [1] Huang, F. et al. Calcium-activated chloride channel TMEM16A modulates mucin secretion and airway smooth muscle contraction. Proc. Natl. Acad. Sci U.S.A 109, 16354-16359 (2012). [0144] [2] Miner, K. et al. The Anthelminthic Niclosamide And Related Compounds Represent Potent Tmem16a Antagonists That Fully Relax Mouse And Human Airway Rings. Frontiers in pharmacology 14,10:51 (2019). [0145] [3] Schreiber et al. Lipid peroxidation drives renal cyst growth in vitro through activation of TMEM16A. J. Am. Soc. Nephrol. 30: 228-242 (2019). [0146] [4] Buchholz B, et al. Anoctamin 1 induces calcium-activated chloride secretion and proliferation of renal cyst-forming epithelial cells. Kidney international advance online publication, 23 Oct. 2013. [0147] [5] Irazabal M V, Rangel L J, Bergstralh E J et al. Imaging Classification of Autosomal Dominant Polycystic Kidney Disease: A Simple Model for Selecting Patients for Clinical Trials. J. Am. Soc. Nephrol. (2015) 26: 160-172. [0148] [6] Gansevoort R T, Arici M, Benzing T et al. Recommendations for the use of tolvaptan in autosomal dominant polycystic kidney disease: a position statement on behalf of the ERA-EDTA Working Groups on Inherited Kidney Disorders and European Renal Best Practice. Nephrol. Dial. Transpl. (2016) 31: 337-48.

[0149] The features of the present invention disclosed in the specification, the claims, and/or in the accompanying figures may, both separately and in any combination thereof, be material for realizing the invention in various forms thereof.