Novel Celecoxib Derivative, RF26, Blocks Colon Cancer Cell Growth by Inhibiting PDE5, Activating cGMP/PKG Signaling, and Suppressing β-catenin-dependent Transcription
- Authors: Sigler S.1, Abdel-Halim M.2, Fathalla R.2, Da Silva L.1, Keeton A.3, Maxuitenko Y.3, Berry K.3, Zhou G.4, Engel M.5, Abadi A.2, Piazza G.3
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Affiliations:
- Department of Pharmacology, Drug Discovery Research Center, Mitchell Cancer Institute, University of South Alabama
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Biotechnology, German University in Cairo
- Department of Drug Discovery and Development, Harrison College of Pharmacy, Auburn University
- Georgia Cancer Center, Department of Medicine, Medical College of Georgia, Augusta University
- Pharmaceutical and Medicinal Chemistry, Saarland University
- Issue: Vol 25, No 1 (2025)
- Pages: 52-62
- Section: Oncology
- URL: https://kld-journal.fedlab.ru/1871-5206/article/view/694414
- DOI: https://doi.org/10.2174/0118715206318802240821114353
- ID: 694414
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Full Text
Abstract
Background:Previous studies have reported that the cGMP-specific PDE5 isozyme is overexpressed in colon adenomas and adenocarcinomas and essential for colon cancer cell proliferation, while PDE5 selective inhibitors (e.g., sildenafil) have been reported to have cancer chemopreventive activity.
Aim:This study aimed to determine the anticancer activity of a novel PDE5 inhibitor, RF26, using colorectal cancer (CRC) cells and the role of PDE5 in CRC tumor growth in vivo.
Objective:The objective of this study was to characterize the anticancer activity of a novel celecoxib derivative, RF26, in CRC cells previously reported to lack COX-2 inhibition but have potent PDE5 inhibitory activity.
Methods:Anticancer activity of RF26 was studied using human CRC cell lines. Its effects on intracellular cGMP levels, cGMP-dependent protein kinase (PKG) activity, β-catenin levels, TCF/LEF transcriptional activity, cell cycle distribution, and apoptosis were measured. CRISPR/cas9 PDE5 knockout techniques were used to determine if PDE5 mediates the anticancer activity of RF26 and validate PDE5 as a cancer target.
Results:RF26 was appreciably more potent than celecoxib and sildenafil to suppress CRC cell growth and was effective at concentrations that increased intracellular cGMP levels and activated PKG signaling. RF26 suppressed β-catenin levels and TCF/LEF transcriptional activity and induced G1 cell cycle arrest and apoptosis within the same concentration range. CRISPR/cas9 PDE5 knockout CRC cells displayed reduced sensitivity to RF26, proliferated slower than parental cells, and failed to establish tumors in mice.
Conclusion:Further evaluation of RF26 for the prevention or treatment of cancer and studying the role of PDE5 in tumorigenesis are warranted.
Keywords
About the authors
Sara Sigler
Department of Pharmacology, Drug Discovery Research Center, Mitchell Cancer Institute, University of South Alabama
Email: info@benthamscience.net
Mohammad Abdel-Halim
Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Biotechnology, German University in Cairo
Author for correspondence.
Email: info@benthamscience.net
Reem Fathalla
Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Biotechnology, German University in Cairo
Email: info@benthamscience.net
Luciana Da Silva
Department of Pharmacology, Drug Discovery Research Center, Mitchell Cancer Institute, University of South Alabama
Email: info@benthamscience.net
Adam Keeton
Department of Drug Discovery and Development, Harrison College of Pharmacy, Auburn University
Email: info@benthamscience.net
Yulia Maxuitenko
Department of Drug Discovery and Development, Harrison College of Pharmacy, Auburn University
Email: info@benthamscience.net
Kristy Berry
Department of Drug Discovery and Development, Harrison College of Pharmacy, Auburn University
Email: info@benthamscience.net
Gang Zhou
Georgia Cancer Center, Department of Medicine, Medical College of Georgia, Augusta University
Email: info@benthamscience.net
Matthias Engel
Pharmaceutical and Medicinal Chemistry, Saarland University
Email: info@benthamscience.net
Ashraf Abadi
Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Biotechnology, German University in Cairo
Email: info@benthamscience.net
Gary Piazza
Department of Drug Discovery and Development, Harrison College of Pharmacy, Auburn University
Author for correspondence.
Email: info@benthamscience.net
References
- Siegel, R.L.; Miller, K.D.; Goding Sauer, A.; Fedewa, S.A.; Butterly, L.F.; Anderson, J.C.; Cercek, A.; Smith, R.A.; Jemal, A. Colorectal cancer statistics, 2020. CA Cancer J. Clin., 2020, 70(3), 145-164. doi: 10.3322/caac.21601 PMID: 32133645
- Walther, A.; Johnstone, E.; Swanton, C.; Midgley, R.; Tomlinson, I.; Kerr, D. Genetic prognostic and predictive markers in colorectal cancer. Nat. Rev. Cancer, 2009, 9(7), 489-499. doi: 10.1038/nrc2645 PMID: 19536109
- Giles, R.H.; van Es, J.H.; Clevers, H. Caught up in a Wnt storm: Wnt signaling in cancer. Biochim. Biophys. Acta, 2003, 1653(1), 1-24. PMID: 12781368
- Powell, S.M.; Zilz, N.; Beazer-Barclay, Y.; Bryan, T.M.; Hamilton, S.R.; Thibodeau, S.N.; Vogelstein, B.; Kinzler, K.W. APC mutations occur early during colorectal tumorigenesis. Nature, 1992, 359(6392), 235-237. doi: 10.1038/359235a0 PMID: 1528264
- Cavallo, R.A.; Cox, R.T.; Moline, M.M.; Roose, J.; Polevoy, G.A.; Clevers, H.; Peifer, M.; Bejsovec, A. Drosophila Tcf and Groucho interact to repress Wingless signalling activity. Nature, 1998, 395(6702), 604-608. doi: 10.1038/26982 PMID: 9783586
- Goss, K.H.; Groden, J. Biology of the adenomatous polyposis coli tumor suppressor. J. Clin. Oncol., 2000, 18(9), 1967-1979. doi: 10.1200/JCO.2000.18.9.1967 PMID: 10784639
- Korinek, V.; Barker, N.; Morin, P.J.; van Wichen, D.; de Weger, R.; Kinzler, K.W.; Vogelstein, B.; Clevers, H. Constitutive transcriptional activation by a β-catenin-Tcf complex in APC-/- colon carcinoma. Science, 1997, 275(5307), 1784-1787. doi: 10.1126/science.275.5307.1784 PMID: 9065401
- Morin, P.J.; Sparks, A.B.; Korinek, V.; Barker, N.; Clevers, H.; Vogelstein, B.; Kinzler, K.W. Activation of β-catenin-Tcf signaling in colon cancer by mutations in β-catenin or APC. Science, 1997, 275(5307), 1787-1790. doi: 10.1126/science.275.5307.1787 PMID: 9065402
- Giardiello, F.M.; Hamilton, S.R.; Krush, A.J.; Piantadosi, S.; Hylind, L.M.; Celano, P.; Booker, S.V.; Robinson, C.R.; Offerhaus, G.J.A. Treatment of colonic and rectal adenomas with sulindac in familial adenomatous polyposis. N. Engl. J. Med., 1993, 328(18), 1313-1316. doi: 10.1056/NEJM199305063281805 PMID: 8385741
- Steinbach, G.; Lynch, P.M.; Phillips, R.K.S.; Wallace, M.H.; Hawk, E.; Gordon, G.B.; Wakabayashi, N.; Saunders, B.; Shen, Y.; Fujimura, T.; Su, L.K.; Levin, B.; Godio, L.; Patterson, S.; Rodriguez-Bigas, M.A.; Jester, S.L.; King, K.L.; Schumacher, M.; Abbruzzese, J.; DuBois, R.N.; Hittelman, W.N.; Zimmerman, S.; Sherman, J.W.; Kelloff, G. The effect of celecoxib, a cyclooxygenase-2 inhibitor, in familial adenomatous polyposis. N. Engl. J. Med., 2000, 342(26), 1946-1952. doi: 10.1056/NEJM200006293422603 PMID: 10874062
- Gurpinar, E.; Grizzle, W.E.; Piazza, G.A. NSAIDs inhibit tumorigenesis, but how? Clin. Cancer Res., 2014, 20(5), 1104-1113. doi: 10.1158/1078-0432.CCR-13-1573 PMID: 24311630
- Piazza, G.A.; Alberts, D.S.; Hixson, L.J.; Paranka, N.S.; Li, H.; Finn, T.; Bogert, C.; Guillen, J.M.; Brendel, K.; Gross, P.H.; Sperl, G.; Ritchie, J.; Burt, R.W.; Ellsworth, L.; Ahnen, D.J.; Pamukcu, R. Sulindac sulfone inhibits azoxymethane-induced colon carcinogenesis in rats without reducing prostaglandin levels. Cancer Res., 1997, 57(14), 2909-2915. PMID: 9230200
- Charalambous, D.; O’Brien, P. Inhibition of colon cancer precursors in the rat by sulindac sulphone is not dependent on inhibition of prostaglandin synthesis. J. Gastroenterol. Hepatol., 1996, 11(4), 307-310. doi: 10.1111/j.1440-1746.1996.tb01376.x PMID: 8713695
- Piazza, G.A.; Rahm, A.L.K.; Krutzsch, M.; Sperl, G.; Paranka, N.S.; Gross, P.H.; Brendel, K.; Burt, R.W.; Alberts, D.S.; Pamukcu, R. Antineoplastic drugs sulindac sulfide and sulfone inhibit cell growth by inducing apoptosis. Cancer Res., 1995, 55(14), 3110-3116. PMID: 7606732
- Arber, N.; Kuwada, S.; Leshno, M.; Sjodahl, R.; Hultcrantz, R.; Rex, D. Sporadic adenomatous polyp regression with exisulind is effective but toxic: a randomised, double blind, placebo controlled, dose-response study. Gut, 2006, 55(3), 367-373. doi: 10.1136/gut.2004.061432 PMID: 16150858
- Piazza, G.A.; Keeton, A.B.; Tinsley, H.N.; Gary, B.D.; Whitt, J.D.; Mathew, B.; Thaiparambil, J.; Coward, L.; Gorman, G.; Li, Y.; Sani, B.; Hobrath, J.V.; Maxuitenko, Y.Y.; Reynolds, R.C. A novel sulindac derivative that does not inhibit cyclooxygenases but potently inhibits colon tumor cell growth and induces apoptosis with antitumor activity. Cancer Prev. Res. (Phila.), 2009, 2(6), 572-580. doi: 10.1158/1940-6207.CAPR-09-0001 PMID: 19470791
- Grösch, S.; Tegeder, I.; Niederberger, E.; Bräutigam, L.; Geisslinger, G. COX‐2 independent induction of cell cycle arrest and apoptosis in colon cancer cells by the selective COX‐2 inhibitor celecoxib. FASEB J., 2001, 15(14), 1-22. doi: 10.1096/fj.01-0299fje PMID: 11606477
- Sade, A.; Tunçay, S.; Çimen, İ.; Severcan, F.; Banerjee, S. Celecoxib reduces fluidity and decreases metastatic potential of colon cancer cell lines irrespective of COX-2 expression. Biosci. Rep., 2012, 32(1), 35-44. doi: 10.1042/BSR20100149 PMID: 21401528
- Schiffmann, S.; Maier, T.J.; Wobst, I.; Janssen, A.; Corban-Wilhelm, H.; Angioni, C.; Geisslinger, G.; Grösch, S. The anti-proliferative potency of celecoxib is not a class effect of coxibs. Biochem. Pharmacol., 2008, 76(2), 179-187. doi: 10.1016/j.bcp.2008.04.017 PMID: 18547544
- Zhu, J.; Huang, J.W.; Tseng, P.H.; Yang, Y.T.; Fowble, J.; Shiau, C.W.; Shaw, Y.J.; Kulp, S.K.; Chen, C.S. From the cyclooxygenase-2 inhibitor celecoxib to a novel class of 3-phosphoinositide-dependent protein kinase-1 inhibitors. Cancer Res., 2004, 64(12), 4309-4318. doi: 10.1158/0008-5472.CAN-03-4063 PMID: 15205346
- Thompson, W.J.; Piazza, G.A.; Li, H.; Liu, L.; Fetter, J.; Zhu, B.; Sperl, G.; Ahnen, D.; Pamukcu, R. Exisulind induction of apoptosis involves guanosine 3′,5′-cyclic monophosphate phosphodiesterase inhibition, protein kinase G activation, and attenuated β-catenin. Cancer Res., 2000, 60(13), 3338-3342. PMID: 10910034
- Piazza, G.A.; Thompson, W.J.; Pamukcu, R.; Alila, H.W.; Whitehead, C.M.; Liu, L.; Fetter, J.R.; Gresh, W.E., Jr; Klein-Szanto, A.J.; Farnell, D.R.; Eto, I.; Grubbs, C.J. Exisulind, a novel proapoptotic drug, inhibits rat urinary bladder tumorigenesis. Cancer Res., 2001, 61(10), 3961-3968. PMID: 11358813
- Kwon, I.K.; Schoenlein, P.V.; Delk, J.; Liu, K.; Thangaraju, M.; Dulin, N.O.; Ganapathy, V.; Berger, F.G.; Browning, D.D. Expression of cyclic guanosine monophosphate‐dependent protein kinase in metastatic colon carcinoma cells blocks tumor angiogenesis. Cancer, 2008, 112(7), 1462-1470. doi: 10.1002/cncr.23334 PMID: 18260092
- Saha, S.; Chowdhury, P.; Pal, A.; Chakrabarti, M.K. Downregulation of human colon carcinoma cell (COLO‐205) proliferation through PKG‐MAP kinase mediated signaling cascade by E. coli heat stable enterotoxin (STa), a potent anti‐angiogenic and anti‐metastatic molecule. J. Appl. Toxicol., 2008, 28(4), 475-483. doi: 10.1002/jat.1297 PMID: 17828804
- Shailubhai, K.; Yu, H.H.; Karunanandaa, K.; Wang, J.Y.; Eber, S.L.; Wang, Y.; Joo, N.S.; Kim, H.D.; Miedema, B.W.; Abbas, S.Z.; Boddupalli, S.S.; Currie, M.G.; Forte, L.R. Uroguanylin treatment suppresses polyp formation in the Apc(Min/+) mouse and induces apoptosis in human colon adenocarcinoma cells via cyclic GMP. Cancer Res., 2000, 60(18), 5151-5157. PMID: 11016642
- Tinsley, H.N.; Gary, B.D.; Thaiparambil, J.; Li, N.; Lu, W.; Li, Y.; Maxuitenko, Y.Y.; Keeton, A.B.; Piazza, G.A. Colon tumor cell growth-inhibitory activity of sulindac sulfide and other nonsteroidal anti-inflammatory drugs is associated with phosphodiesterase 5 inhibition. Cancer Prev. Res. (Phila.), 2010, 3(10), 1303-1313. doi: 10.1158/1940-6207.CAPR-10-0030 PMID: 20876730
- Tinsley, H.N.; Gary, B.D.; Keeton, A.B.; Zhang, W.; Abadi, A.H.; Reynolds, R.C.; Piazza, G.A. Sulindac sulfide selectively inhibits growth and induces apoptosis of human breast tumor cells by phosphodiesterase 5 inhibition, elevation of cyclic GMP, and activation of protein kinase G. Mol. Cancer Ther., 2009, 8(12), 3331-3340. doi: 10.1158/1535-7163.MCT-09-0758 PMID: 19996273
- Tinsley, H.N.; Gary, B.D.; Keeton, A.B.; Lu, W.; Li, Y.; Piazza, G.A. Inhibition of PDE5 by sulindac sulfide selectively induces apoptosis and attenuates oncogenic Wnt/β-catenin-mediated transcription in human breast tumor cells. Cancer Prev. Res. (Phila.), 2011, 4(8), 1275-1284. doi: 10.1158/1940-6207.CAPR-11-0095 PMID: 21505183
- Li, N.; Xi, Y.; Tinsley, H.N.; Gurpinar, E.; Gary, B.D.; Zhu, B.; Li, Y.; Chen, X.; Keeton, A.B.; Abadi, A.H.; Moyer, M.P.; Grizzle, W.E.; Chang, W.C.; Clapper, M.L.; Piazza, G.A. Sulindac selectively inhibits colon tumor cell growth by activating the cGMP/PKG pathway to suppress Wnt/β-catenin signaling. Mol. Cancer Ther., 2013, 12(9), 1848-1859. doi: 10.1158/1535-7163.MCT-13-0048 PMID: 23804703
- Li, N.; Chen, X.; Zhu, B.; Ramírez-Alcántara, V.; Canzoneri, J.C.; Lee, K.; Sigler, S.; Gary, B.; Li, Y.; Zhang, W.; Moyer, M.P.; Salter, E.A.; Wierzbicki, A.; Keeton, A.B.; Piazza, G.A. Suppression of β-catenin/TCF transcriptional activity and colon tumor cell growth by dual inhibition of PDE5 and 10. Oncotarget, 2015, 6(29), 27403-27415. doi: 10.18632/oncotarget.4741 PMID: 26299804
- Whitt, J.D.; Li, N.; Tinsley, H.N.; Chen, X.; Zhang, W.; Li, Y.; Gary, B.D.; Keeton, A.B.; Xi, Y.; Abadi, A.H.; Grizzle, W.E.; Piazza, G.A. A novel sulindac derivative that potently suppresses colon tumor cell growth by inhibiting cGMP phosphodiesterase and β-catenin transcriptional activity. Cancer Prev. Res. (Phila.), 2012, 5(6), 822-833. doi: 10.1158/1940-6207.CAPR-11-0559 PMID: 22556201
- Islam, B.N.; Sharman, S.K.; Hou, Y.; Bridges, A.E.; Singh, N.; Kim, S.; Kolhe, R.; Trillo-Tinoco, J.; Rodriguez, P.C.; Berger, F.G.; Sridhar, S.; Browning, D.D. Sildenafil suppresses inflammation-driven colorectal cancer in mice. Cancer Prev. Res. (Phila.), 2017, 10(7), 377-388. doi: 10.1158/1940-6207.CAPR-17-0015 PMID: 28468928
- Lin, S.; Wang, J.; Wang, L.; Wen, J.; Guo, Y.; Qiao, W.; Zhou, J.; Xu, G.; Zhi, F. Phosphodiesterase-5 inhibition suppresses colonic inflammation-induced tumorigenesis via blocking the recruitment of MDSC. Am. J. Cancer Res., 2017, 7(1), 41-52. PMID: 28123846
- Bhagavathula, A.S.; Tesfaye, W.; Vidyasagar, K. Phosphodiesterase type 5 inhibitors use and risk of colorectal cancer: A systematic review and meta-analysis. Int. J. Colorectal Dis., 2021, 36(12), 2577-2584. doi: 10.1007/s00384-021-04022-5 PMID: 34508301
- Mei, X-L.; Yang, Y.; Zhang, Y-J.; Li, Y.; Zhao, J-M.; Qiu, J-G.; Zhang, W-J.; Jiang, Q-W.; Xue, Y-Q.; Zheng, D-W.; Chen, Y.; Qin, W.M.; Wei, M.N.; Shi, Z. Sildenafil inhibits the growth of human colorectal cancer in vitro and in vivo. Am. J. Cancer Res., 2015, 5(11), 3311-3324. PMID: 26807313
- Klein, T.; Eltze, M.; Grebe, T.; Hatzelmann, A.; Kömhoff, M. Celecoxib dilates guinea-pig coronaries and rat aortic rings and amplifies NO/cGMP signaling by PDE5 inhibition. Cardiovasc. Res., 2007, 75(2), 390-397. doi: 10.1016/j.cardiores.2007.02.026 PMID: 17383621
- Abdel-Halim, M.; Sigler, S.; Racheed, N.A.S.; Hefnawy, A.; Fathalla, R.K.; Hammam, M.A.; Maher, A.; Maxuitenko, Y.; Keeton, A.B.; Hartmann, R.W.; Engel, M.; Piazza, G.A.; Abadi, A.H. From celecoxib to a novel class of phosphodiesterase 5 inhibitors: Trisubstituted pyrazolines as novel phosphodiesterase 5 inhibitors with extremely high potency and phosphodiesterase isozyme selectivity. J. Med. Chem., 2021, 64(8), 4462-4477. doi: 10.1021/acs.jmedchem.0c01120 PMID: 33793216
- Abdel-Halim, M.; Tinsley, H.; Keeton, A.B.; Weam, M.; Atta, N.H.; Hammam, M.A.; Hefnawy, A.; Hartmann, R.W.; Engel, M.; Piazza, G.A.; Abadi, A.H. Discovery of trisubstituted pyrazolines as a novel scaffold for the development of selective phosphodiesterase 5 inhibitors. Bioorg. Chem., 2020, 104, 104322. doi: 10.1016/j.bioorg.2020.104322 PMID: 33142429
- Butt, E.; Abel, K.; Krieger, M.; Palm, D.; Hoppe, V.; Hoppe, J.; Walter, U. cAMP- and cGMP-dependent protein kinase phosphorylation sites of the focal adhesion vasodilator-stimulated phosphoprotein (VASP) in vitro and in intact human platelets. J. Biol. Chem., 1994, 269(20), 14509-14517. doi: 10.1016/S0021-9258(17)36652-8 PMID: 8182057
- Tinsley, H.N.; Grizzle, W.E.; Abadi, A.; Keeton, A.; Zhu, B.; Xi, Y.; Piazza, G.A. New NSAID targets and derivatives for colorectal cancer chemoprevention. Recent Results Cancer Res., 2013, 191, 105-120. doi: 10.1007/978-3-642-30331-9_6 PMID: 22893202
- Vighi, E.; Rentsch, A.; Henning, P.; Comitato, A.; Hoffmann, D.; Bertinetti, D.; Bertolotti, E.; Schwede, F.; Herberg, F.W.; Genieser, H.G.; Marigo, V. New cGMP analogues restrain proliferation and migration of melanoma cells. Oncotarget, 2018, 9(4), 5301-5320. doi: 10.18632/oncotarget.23685 PMID: 29435180
- Zhu, B.; Lindsey, A.; Li, N.; Lee, K.; Ramirez-Alcantara, V.; Canzoneri, J.C.; Fajardo, A.; Madeira da Silva, L.; Thomas, M.; Piazza, J.T.; Yet, L.; Eberhardt, B.T.; Gurpinar, E.; Otali, D.; Grizzle, W.; Valiyaveettil, J.; Chen, X.; Keeton, A.B.; Piazza, G.A. Phosphodiesterase 10A is overexpressed in lung tumor cells and inhibitors selectively suppress growth by blocking β-catenin and MAPK signaling. Oncotarget, 2017, 8(41), 69264-69280. doi: 10.18632/oncotarget.20566 PMID: 29050202
- Ding, P.R.; Tiwari, A.K.; Ohnuma, S.; Lee, J.W.K.K.; An, X.; Dai, C.L.; Lu, Q.S.; Singh, S.; Yang, D.H.; Talele, T.T.; Ambudkar, S.V.; Chen, Z.S. The phosphodiesterase-5 inhibitor vardenafil is a potent inhibitor of ABCB1/P-glycoprotein transporter. PLoS One, 2011, 6(4), e19329. doi: 10.1371/journal.pone.0019329 PMID: 21552528
- Hussain, M.; Javeed, A.; Ashraf, M.; Al-Zaubai, N.; Stewart, A.; Mukhtar, M.M. Non-steroidal anti-inflammatory drugs, tumour immunity and immunotherapy. Pharmacol. Res., 2012, 66(1), 7-18. doi: 10.1016/j.phrs.2012.02.003 PMID: 22449788
- Zelenay, S.; van der Veen, A.G.; Böttcher, J.P.; Snelgrove, K.J.; Rogers, N.; Acton, S.E.; Chakravarty, P.; Girotti, M.R.; Marais, R.; Quezada, S.A.; Sahai, E.; Reis e Sousa, C. Cyclooxygenase-dependent tumor growth through evasion of immunity. Cell, 2015, 162(6), 1257-1270. doi: 10.1016/j.cell.2015.08.015 PMID: 26343581
- Piazza, G.A.; Ward, A.; Chen, X.; Maxuitenko, Y.; Coley, A.; Aboelella, N.S.; Buchsbaum, D.J.; Boyd, M.R.; Keeton, A.B.; Zhou, G. PDE5 and PDE10 inhibition activates cGMP/PKG signaling to block Wnt/β-catenin transcription, cancer cell growth, and tumor immunity. Drug Discov. Today, 2020, 25(8), 1521-1527. doi: 10.1016/j.drudis.2020.06.008 PMID: 32562844
- Serafini, P.; Meckel, K.; Kelso, M.; Noonan, K.; Califano, J.; Koch, W.; Dolcetti, L.; Bronte, V.; Borrello, I. Phosphodiesterase-5 inhibition augments endogenous antitumor immunity by reducing myeloid-derived suppressor cell function. J. Exp. Med., 2006, 203(12), 2691-2702. doi: 10.1084/jem.20061104 PMID: 17101732
- Noonan, K.A.; Ghosh, N.; Rudraraju, L.; Bui, M.; Borrello, I. Targeting immune suppression with PDE5 inhibition in end-stage multiple myeloma. Cancer Immunol. Res., 2014, 2(8), 725-731. doi: 10.1158/2326-6066.CIR-13-0213 PMID: 24878583
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