Citral reduces breast tumor growth by inhibiting the cancer stem cell marker ALDH1A3.
Breast cancer stem cells (CSCs) can be identified by increased Aldefluor fluorescence caused by increased expression of aldehyde dehydrogenase 1A3 (ALDH1A3), as well as ALDH1A1 and ALDH2. In addition to being a CSC marker, ALDH1A3 regulates gene expression via retinoic acid (RA) signaling and plays a key role in the progression and chemotherapy resistance of cancer. Therefore, ALDH1A3 represents a druggable anti-cancer target of interest. Since to date, there are no characterized ALDH1A3 isoform inhibitors, drugs that were previously described as inhibiting the activity of other ALDH isoforms were tested for anti-ALDH1A3 activity. Twelve drugs (3-hydroxy-dl-kynurenine, benomyl, citral, chloral hydrate, cyanamide, daidzin, DEAB, disulfiram, gossypol, kynurenic acid, molinate, and pargyline) were compared for their efficacy in inducing apoptosis and reducing ALDH1A3, ALDH1A1 and ALDH2-associated Aldefluor fluorescence in breast cancer cells. Citral was identified as the best inhibitor of ALDH1A3, reducing the Aldefluor fluorescence in breast cancer cell lines and in a patient-derived tumor xenograft. Nanoparticle encapsulated citral specifically reduced the enhanced tumor growth of MDA-MB-231 cells overexpressing ALDH1A3. To determine the potential mechanisms of citral-mediated tumor growth inhibition, we performed cell proliferation, clonogenic, and gene expression assays. Citral reduced ALDH1A3-mediated colony formation and expression of ALDH1A3-inducible genes. In conclusion, citral is an effective ALDH1A3 inhibitor and is able to block ALDH1A3-mediated breast tumor growth, potentially via blocking its colony forming and gene expression regulation activity. The promise of ALDH1A3 inhibitors as adjuvant therapies for patients with tumors that have a large population of high-ALDH1A3 CSCs is discussed.
Department of Pathology, Dalhousie University, Halifax, NS, Canada.
Margaret Lois
ML
Thomas
Department of Microbiology & Immunology, Dalhousie University, Halifax, NS, Canada.
Roberto
R
de Antueno
Department of Pathology, Dalhousie University, Halifax, NS, Canada.
Krysta Mila
KM
Coyle
Department of Pathology, Dalhousie University, Halifax, NS, Canada.
Mohammad
M
Sultan
Department of Pathology, Dalhousie University, Halifax, NS, Canada.
Brianne Marie
BM
Cruickshank
Department of Pathology, Dalhousie University, Halifax, NS, Canada.
Michael Anthony
MA
Giacomantonio
Department of Pathology, Dalhousie University, Halifax, NS, Canada; Department of Surgery, Dalhousie University, Halifax, NS, Canada.
Carman Anthony
CA
Giacomantonio
Department of Microbiology & Immunology, Dalhousie University, Halifax, NS, Canada.
Roy
R
Duncan
Department of Pathology, Dalhousie University, Halifax, NS, Canada; Department of Microbiology & Immunology, Dalhousie University, Halifax, NS, Canada. Electronic address: paola.marcato@dal.ca.
Paola
P
Marcato
D000080462:Acyclic Monoterpenes; D000445:Aldehyde Oxidoreductases / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D014408:Biomarkers, Tumor / Q000378:metabolism*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D005453:Fluorescence; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D039821:Monoterpenes / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use*; D053758:Nanoparticles / Q000737:chemistry; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D014410:Tumor Stem Cell Assay; D023041:Xenograft Model Antitumor Assays
D000080462:Acyclic Monoterpenes; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D039821:Monoterpenes; D000445:Aldehyde Oxidoreductases; C018699:aldehyde dehydrogenase (NAD(P)+); C007076:citral
ALDH1A3; Aldefluor; Breast cancer; Cancer stem cell