{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,16]],"date-time":"2026-05-16T16:20:48Z","timestamp":1778948448200,"version":"3.51.4"},"reference-count":55,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2023,1,7]],"date-time":"2023-01-07T00:00:00Z","timestamp":1673049600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Basic Science Research Program through the National Research Foundation of Korea (NRF)","award":["NRF-2021R1I1A3055927"],"award-info":[{"award-number":["NRF-2021R1I1A3055927"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Bone metastasis resulting from advanced breast cancer causes osteolysis and increases mortality in patients. Kalkitoxin (KT), a lipopeptide toxin derived from the marine cyanobacterium Moorena producens (previously Lyngbya majuscula), has an anti-metastatic effect on cancer cells. We verified that KT suppressed cancer cell migration and invasion in vitro and in animal models in the present study. We confirmed that KT suppressed osteoclast-soup-derived MDA-MB-231 cell invasion in vitro and induced osteolysis in a mouse model, possibly enhancing\/inhibiting metastasis markers. Furthermore, KT inhibits CXCL5 and CXCR2 expression, suppressing the secondary growth of breast cancer cells on the bone, brain, and lungs. The breast-cancer-induced osteolysis in the mouse model further reveals that KT plays a protective role, judging by micro-computed tomography and immunohistochemistry. We report for the first time the novel suppressive effects of KT on cancer cell migration and invasion in vitro and on MDA-MB-231-induced bone loss in vivo. These results suggest that KT may be a potential therapeutic drug for the treatment of breast cancer metastasis.<\/jats:p>","DOI":"10.3390\/ijms24021207","type":"journal-article","created":{"date-parts":[[2023,1,9]],"date-time":"2023-01-09T02:09:39Z","timestamp":1673230179000},"page":"1207","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Kalkitoxin: A Potent Suppressor of Distant Breast Cancer Metastasis"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8932-3468","authenticated-orcid":false,"given":"Saroj Kumar","family":"Shrestha","sequence":"first","affiliation":[{"name":"Department of Dental Pharmacology, School of Dentistry, Jeonbuk National University, Jeonju 561-756, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kyung Hyun","family":"Min","sequence":"additional","affiliation":[{"name":"Laboratory of Pharmacology, School of Pharmacy, Jeonbuk National University, Jeonju 561-756, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Se Woong","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Dental Pharmacology, School of Dentistry, Jeonbuk National University, Jeonju 561-756, Republic of Korea"},{"name":"Laboratory of Pharmacology, School of Pharmacy, Jeonbuk National University, Jeonju 561-756, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2774-8727","authenticated-orcid":false,"given":"Hyoungsu","family":"Kim","sequence":"additional","affiliation":[{"name":"College of Pharmacy, Ajou University, San 5, Woncheon-dong, Youngtong-gu, Suwon 443-749, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1403-4458","authenticated-orcid":false,"given":"William H.","family":"Gerwick","sequence":"additional","affiliation":[{"name":"Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California at San Diego, La Jolla, CA 92037, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yunjo","family":"Soh","sequence":"additional","affiliation":[{"name":"Department of Dental Pharmacology, School of Dentistry, Jeonbuk National University, Jeonju 561-756, Republic of Korea"},{"name":"Laboratory of Pharmacology, School of Pharmacy, Jeonbuk National University, Jeonju 561-756, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,1,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"djv360","DOI":"10.1093\/jnci\/djv360","article-title":"CAPG and GIPC1: Breast cancer biomarkers for bone metastasis development and treatment","volume":"108","author":"Westbrook","year":"2016","journal-title":"J. Natl. Cancer Inst."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"66","DOI":"10.1186\/s12943-015-0332-2","article-title":"PinX1 inhibits the invasion and metastasis of human breast cancer via suppressing NF-\u03baB\/MMP-9 signaling pathway","volume":"14","author":"Shi","year":"2015","journal-title":"Mol. Cancer"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"584","DOI":"10.1038\/nrc867","article-title":"Metastasis: Metastasis to bone: Causes, consequences and therapeutic opportunities","volume":"2","author":"Mundy","year":"2002","journal-title":"Nat. Rev. Cancer"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"3949","DOI":"10.1200\/JCO.2017.73.7437","article-title":"Cost-Effectiveness Analysis of Monthly Zoledronic Acid, Zoledronic Acid Every 3 Months, and Monthly Denosumab in Women With Breast Cancer and Skeletal Metastases: CALGB 70604 (Alliance)","volume":"35","author":"Shapiro","year":"2017","journal-title":"J. Clin. Oncol. Off. J. Am. Soc. Clin. Oncol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"8319","DOI":"10.1158\/0008-5472.CAN-06-0410","article-title":"Reassessing epithelial to mesenchymal transition as a prerequisite for carcinoma invasion and metastasis","volume":"66","author":"Christiansen","year":"2006","journal-title":"Cancer Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"989","DOI":"10.1158\/0008-5472.CAN-07-2017","article-title":"Epithelial-mesenchymal transition in breast cancer relates to the basal-like phenotype","volume":"68","author":"Hardisson","year":"2008","journal-title":"Cancer Res."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"192","DOI":"10.1093\/carcin\/bgp289","article-title":"Activation of JAK2\/STAT3 signaling by osteopontin promotes tumor growth in human breast cancer cells","volume":"31","author":"Behera","year":"2010","journal-title":"Carcinogenesis"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1186\/s12964-020-0527-z","article-title":"Role of STAT3 signaling pathway in breast cancer","volume":"18","author":"Ma","year":"2020","journal-title":"Cell Commun. Signal."},{"key":"ref_9","first-page":"1","article-title":"The CXCL5\/CXCR2 axis is sufficient to promote breast cancer colonization during bone metastasis","volume":"10","author":"Curtis","year":"2019","journal-title":"Nat. Commun."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2473","DOI":"10.1158\/1535-7163.MCT-15-0252","article-title":"CXCR4 protein epitope mimetic antagonist POL5551 disrupts metastasis and enhances chemotherapy effect in triple-negative breast cancer","volume":"14","author":"Xiang","year":"2015","journal-title":"Mol. Cancer Ther."},{"key":"ref_11","first-page":"2892","article-title":"Molecular mechanisms of osteolytic bone metastases","volume":"88","author":"Guise","year":"2000","journal-title":"Cancer Interdiscip. Int. J. Am. Cancer Soc."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"92","DOI":"10.1016\/j.ctrv.2007.09.002","article-title":"RANK ligand as a therapeutic target for bone metastases and multiple myeloma","volume":"34","author":"Roodman","year":"2008","journal-title":"Cancer Treat. Rev."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"45969","DOI":"10.1074\/jbc.M408795200","article-title":"Essential role of p38 mitogen-activated protein kinase in cathepsin K gene expression during osteoclastogenesis through association of NFATc1 and PU","volume":"279","author":"Matsumoto","year":"2004","journal-title":"1. J. Biol. Chem."},{"key":"ref_14","unstructured":"Nannini, C.J. (2002). Novel Secondary Metabolites from a Madagascar Collection of Lyngbya Majuscula. [Masters Thesis, Oregon State University]."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"12041","DOI":"10.1021\/ja005526y","article-title":"Structure, Synthesis, and Biological Properties of Kalkitoxin, a Novel Neurotoxin from the Marine Cyanobacterium Lyngbya m ajuscula","volume":"122","author":"Wu","year":"2000","journal-title":"J. Am. Chem. Soc."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1552","DOI":"10.3390\/md13031552","article-title":"Kalkitoxin inhibits angiogenesis, disrupts cellular hypoxic signaling, and blocks mitochondrial electron transport in tumor cells","volume":"13","author":"Morgan","year":"2015","journal-title":"Mar. Drugs"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1016\/j.toxlet.2005.03.007","article-title":"The neurotoxic lipopeptide kalkitoxin interacts with voltage-sensitive sodium channels in cerebellar granule neurons","volume":"158","author":"Lepage","year":"2005","journal-title":"Toxicol. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"2092","DOI":"10.1039\/b404205k","article-title":"Total synthesis and biological evaluation of (+)-kalkitoxin, a cytotoxic metabolite of the cyanobacterium Lyngbya majuscula","volume":"2","author":"White","year":"2004","journal-title":"Org. Biomol. Chem."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"889","DOI":"10.1016\/S1534-5807(02)00369-6","article-title":"Induction and activation of the transcription factor NFATc1 (NFAT2) integrate RANKL signaling in terminal differentiation of osteoclasts","volume":"3","author":"Takayanagi","year":"2002","journal-title":"Dev. Cell"},{"key":"ref_20","first-page":"98","article-title":"The distribution of secondary growths in cancer of the breast","volume":"8","author":"Paget","year":"1989","journal-title":"Cancer Metastasis Rev."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"2192","DOI":"10.1101\/gad.225334.113","article-title":"Epithelial\u2013mesenchymal plasticity in carcinoma metastasis","volume":"27","author":"Tsai","year":"2013","journal-title":"Genes Dev."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"272","DOI":"10.1016\/j.bbcan.2012.04.008","article-title":"The biological kinship of hypoxia with CSC and EMT and their relationship with deregulated expression of miRNAs and tumor aggressiveness","volume":"1826","author":"Bao","year":"2012","journal-title":"Biochim. Biophys. Acta (BBA)-Rev. Cancer"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"9258396","DOI":"10.1155\/2020\/9258396","article-title":"Signal transduction pathways in breast cancer: The important role of PI3K\/Akt\/mTOR","volume":"2020","author":"Ortega","year":"2020","journal-title":"J. Oncol."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Vafeiadou, V., Hany, D., and Picard, D. (2022). Hyperactivation of MAPK induces tamoxifen resistance in SPRED2-deficient ER\u03b1-positive breast cancer. Cancers, 14.","DOI":"10.3390\/cancers14040954"},{"key":"ref_25","first-page":"3264","article-title":"The effect of calcyclin binding protein on gastric cancer cell proliferation","volume":"86","author":"Ning","year":"2006","journal-title":"Zhonghua Yi Xue Za Zhi"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"313","DOI":"10.3389\/fendo.2018.00313","article-title":"Role of tumor-derived chemokines in osteolytic bone metastasis","volume":"9","author":"Coniglio","year":"2018","journal-title":"Front. Endocrinol."},{"key":"ref_27","first-page":"753","article-title":"Mechanisms of osteolytic and osteoblastic skeletal lesions","volume":"4","author":"Roodman","year":"2015","journal-title":"Bonekey Rep."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"2527","DOI":"10.1002\/ijc.26031","article-title":"The seed and soil hypothesis revisited--the role of tumor-stroma interactions in metastasis to different organs","volume":"128","author":"Langley","year":"2011","journal-title":"Int. J. Cancer"},{"key":"ref_29","first-page":"1573","article-title":"Levels of hypoxia-inducible factor-1\u03b1 independently predict prognosis in patients with lymph node negative breast carcinoma","volume":"97","author":"Bos","year":"2003","journal-title":"Cancer Interdiscip. Int. J. Am. Cancer Soc."},{"key":"ref_30","first-page":"5830","article-title":"Overexpression of hypoxia-inducible factor 1\u03b1 in common human cancers and their metastases","volume":"59","author":"Zhong","year":"1999","journal-title":"Cancer Res."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"207","DOI":"10.1016\/j.tips.2012.01.005","article-title":"Hypoxia-inducible factors: Mediators of cancer progression and targets for cancer therapy","volume":"33","author":"Semenza","year":"2012","journal-title":"Trends Pharmacol. Sci."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"2725","DOI":"10.1158\/0008-5472.CAN-05-3719","article-title":"Hypoxia-inducible factor-1-dependent repression of E-cadherin in von Hippel-Lindau tumor suppressor\u2013null renal cell carcinoma mediated by TCF3, ZFHX1A, and ZFHX1B","volume":"66","author":"Krishnamachary","year":"2006","journal-title":"Cancer Res."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"573","DOI":"10.1016\/0092-8674(89)90438-8","article-title":"Interleukin-6 triggers the association of its receptor with a possible signal transducer, gp130","volume":"58","author":"Taga","year":"1989","journal-title":"Cell"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"252","DOI":"10.1186\/bcr65","article-title":"Metalloproteinases: Role in breast carcinogenesis, invasion and metastasis","volume":"2","author":"Duffy","year":"2000","journal-title":"Breast Cancer Res."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"317","DOI":"10.1016\/B978-0-12-394311-8.00014-5","article-title":"Cadherins and Epithelial-To-Mesenchymal Transition","volume":"116","author":"Gheldof","year":"2013","journal-title":"Prog. Mol. Biol. Transl. Sci."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"118","DOI":"10.1038\/nrc1276","article-title":"Cell adhesion and signalling by cadherins and Ig-CAMs in cancer","volume":"4","author":"Cavallaro","year":"2004","journal-title":"Nat. Rev. Cancer"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"864","DOI":"10.1038\/ncb3013","article-title":"ATM-mediated stabilization of ZEB1 promotes DNA damage response and radioresistance through CHK1","volume":"16","author":"Zhang","year":"2014","journal-title":"Nat. Cell Biol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"4283","DOI":"10.1242\/jcs.02560","article-title":"Viral oncoprotein-induced mislocalization of select PDZ proteins disrupts tight junctions and causes polarity defects in epithelial cells","volume":"118","author":"Latorre","year":"2005","journal-title":"J. Cell Sci."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"374","DOI":"10.1002\/ijc.11571","article-title":"Reexpression of the TJ protein CLDN1 induces apoptosis in breast tumor spheroids","volume":"108","author":"Hoevel","year":"2004","journal-title":"Int. J. Cancer"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"825","DOI":"10.1248\/bpb.32.825","article-title":"Effect of claudin expression on paracellular permeability, migration and invasion of colonic cancer cells","volume":"32","author":"Takehara","year":"2009","journal-title":"Biol. Pharm. Bull."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"442","DOI":"10.1038\/nrc822","article-title":"Epithelial\u2013mesenchymal transitions in tumour progression","volume":"2","author":"Thiery","year":"2002","journal-title":"Nat. Rev. Cancer"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"R64","DOI":"10.1016\/j.cub.2004.12.058","article-title":"\u03b2-Catenin: A pivot between cell adhesion and Wnt signalling","volume":"15","author":"Bienz","year":"2005","journal-title":"Curr. Biol."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"1429","DOI":"10.1172\/JCI36183","article-title":"Biomarkers for epithelial-mesenchymal transitions","volume":"119","author":"Zeisberg","year":"2009","journal-title":"J. Clin. Investig."},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Smith, B.N., Burton, L.J., Henderson, V., Randle, D.D., Morton, D.J., Smith, B.A., Taliaferro-Smith, L., Nagappan, P., Yates, C., and Zayzafoon, M. (2014). Snail promotes epithelial mesenchymal transition in breast cancer cells in part via activation of nuclear ERK2. PLoS ONE, 9.","DOI":"10.1371\/journal.pone.0104987"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"1461","DOI":"10.3892\/ijo.2015.2878","article-title":"Slug contributes to cancer progression by direct regulation of ER\u03b1 signaling pathway","volume":"46","author":"Li","year":"2015","journal-title":"Int. J. Oncol."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"1047","DOI":"10.1016\/j.neo.2014.10.006","article-title":"Suppression of invasion and metastasis of triple-negative breast cancer lines by pharmacological or genetic inhibition of slug activity","volume":"16","author":"Chiodoni","year":"2014","journal-title":"Neoplasia"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"4373","DOI":"10.1021\/pr2005617","article-title":"Identification of key players for colorectal cancer metastasis by iTRAQ quantitative proteomics profiling of isogenic SW480 and SW620 cell lines","volume":"10","author":"Ghosh","year":"2011","journal-title":"J. Proteome Res."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"218","DOI":"10.1097\/SPC.0b013e32830baea9","article-title":"Cathepsin K inhibitors as treatment of bone metastasis","volume":"2","author":"Bonnelye","year":"2008","journal-title":"Curr. Opin. Support Palliat. Care"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"S5","DOI":"10.1186\/ar2169","article-title":"Tumor metastasis to bone","volume":"9","author":"Virk","year":"2007","journal-title":"Arthritis Res. Ther."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"117","DOI":"10.1186\/s12943-015-0390-5","article-title":"Osteoprotegerin in breast cancer: Beyond bone remodeling","volume":"14","author":"Weichhaus","year":"2015","journal-title":"Mol. Cancer"},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Peng, X., Guo, W., Ren, T., Lou, Z., Lu, X., Zhang, S., Lu, Q., and Sun, Y. (2013). Differential expression of the RANKL\/RANK\/OPG system is associated with bone metastasis in human non-small cell lung cancer. PLoS ONE, 8.","DOI":"10.1371\/journal.pone.0058361"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"162","DOI":"10.1158\/1078-0432.162.11.1","article-title":"Expression of receptor activator of nuclear factor-kappaB is inversely correlated with metastatic phenotype in breast carcinoma","volume":"11","author":"Bhatia","year":"2005","journal-title":"Clin. Cancer Res."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1016\/j.jnci.2012.06.002","article-title":"Bone metastasis in breast cancer: The story of RANK-ligand","volume":"24","author":"Azim","year":"2012","journal-title":"J. Egypt. Natl. Cancer Inst."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"1977","DOI":"10.1021\/np0704250","article-title":"Cloning and biochemical characterization of the hectochlorin biosynthetic gene cluster from the marine cyanobacterium Lyngbya majuscula","volume":"70","author":"Ramaswamy","year":"2007","journal-title":"J. Nat. Prod."},{"key":"ref_55","doi-asserted-by":"crossref","unstructured":"Li, L., Yang, M., Shrestha, S., Kim, H., Gerwick, W., and Soh, Y. (2021). Kalkitoxin reduces osteoclast formation and resorption and protects against inflammatory bone loss. Int. J. Mol. Sci., 22.","DOI":"10.3390\/ijms22052303"}],"container-title":["International Journal of Molecular Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1422-0067\/24\/2\/1207\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T18:02:53Z","timestamp":1760119373000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1422-0067\/24\/2\/1207"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,1,7]]},"references-count":55,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2023,1]]}},"alternative-id":["ijms24021207"],"URL":"https:\/\/doi.org\/10.3390\/ijms24021207","relation":{},"ISSN":["1422-0067"],"issn-type":[{"value":"1422-0067","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,1,7]]}}}