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Al Jofi FE, Ma T, Guo D, Schneider MP, Shu Y, Xu HHK, Schneider A. Functional organic cation transporters mediate osteogenic response to metformin in human umbilical cord mesenchymal stromal cells. Cytotherapy 2018; 20:650-659. [PMID: 29555409 DOI: 10.1016/j.jcyt.2018.02.369] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 01/28/2018] [Accepted: 02/11/2018] [Indexed: 02/07/2023]
Abstract
BACKGROUND Compelling evidence indicates that metformin, a low-cost and safe orally administered biguanide prescribed to millions of type 2 diabetics worldwide, induces the osteoblastic differentiation of mesenchymal stromal cells (MSCs) through the 5' adenosine monophosphate (AMP)-activated protein kinase (AMPK) pathway. As a highly hydrophilic cationic compound, metformin uptake is facilitated by cell membrane organic cation transporters (OCTs) of the solute carrier 22A gene family. We hypothesized that to effectively enhance osteogenic differentiation, and ultimately bone regeneration, metformin must gain access into functional OCT-expressing MSCs. METHODS Data was obtained through immunoblotting, cellular uptake, mineralization and gene expression assays. RESULTS We demonstrate for the first time that functional OCTs are expressed in human-derived MSCs from umbilical cord Wharton's jelly, an inexhaustible source of nonembryonic MSCs with proven osteogenic potential. A clinically relevant concentration of metformin led to AMPK activation, enhanced mineralized nodule formation and increased expression of the osteogenic transcription factor Runt-related transcription factor 2 (RUNX2). Indeed, targeting OCT function through pharmacological and genetic approaches markedly blunted these responses. CONCLUSIONS Our findings indicate that functional OCT expression in UC-MSCs is a biological prerequisite that facilitates the intracellular uptake of metformin to induce an osteogenic effect. Future pre-clinical studies are warranted to investigate whether the expression of functional OCTs may serve as a potential biomarker to predict osteogenic responses to metformin.
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Affiliation(s)
- Faisal E Al Jofi
- Department of Oncology and Diagnostic Sciences, School of Dentistry, University of Maryland, Baltimore, Maryland, USA; Department of Preventive Dental Science, Division of Periodontics, Imam Abdulrahman Bin Faisal University, College of Dentistry, Dammam, Saudi Arabia
| | - Tao Ma
- Department of Oncology and Diagnostic Sciences, School of Dentistry, University of Maryland, Baltimore, Maryland, USA
| | - Dong Guo
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland, USA
| | - Monica P Schneider
- Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Maryland, Baltimore, Maryland, USA
| | - Yan Shu
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland, USA; Greenebaum Comprehensive Cancer Center, Program in Oncology, School of Medicine, University of Maryland, Baltimore, Maryland, USA
| | - Hockin H K Xu
- Greenebaum Comprehensive Cancer Center, Program in Oncology, School of Medicine, University of Maryland, Baltimore, Maryland, USA; Biomaterials and Tissue Engineering Division, Department of Advanced Oral Sciences and Therapeutics, School of Dentistry, University of Maryland, Baltimore, Maryland, USA; Center for Stem Cell Biology and Regenerative Medicine, School of Medicine, University of Maryland, Baltimore, Maryland, USA
| | - Abraham Schneider
- Department of Oncology and Diagnostic Sciences, School of Dentistry, University of Maryland, Baltimore, Maryland, USA; Greenebaum Comprehensive Cancer Center, Program in Oncology, School of Medicine, University of Maryland, Baltimore, Maryland, USA.
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Kearney AY, Fan YH, Giri U, Saigal B, Gandhi V, Heymach JV, Zurita AJ. 8-Chloroadenosine Sensitivity in Renal Cell Carcinoma Is Associated with AMPK Activation and mTOR Pathway Inhibition. PLoS One 2015; 10:e0135962. [PMID: 26313261 PMCID: PMC4552467 DOI: 10.1371/journal.pone.0135962] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 07/28/2015] [Indexed: 12/25/2022] Open
Abstract
The adenosine analog 8-chloroadenosine has been shown to deplete ATP and inhibit tumor growth in hematological malignancies as well as in lung and breast cancer cell lines. We investigated effects of 8-chloroadenosine on clear cell (cc) renal cell carcinoma (RCC) cell lines. 8-chloroadenosine was effective against ccRCC cell viability in vitro, with IC50 ranging from 2 μM in the most sensitive CAKI-1 to 36 μM in the most resistant RXF-393. Proteomic analysis by reverse-phase protein array revealed that 8-chloroadenosine treatment leads to inhibition of the mTOR pathway. In time-course experiments, 8-chloroadenosine treatment rapidly activated AMPK, measured by AMPK and ACC phosphorylation, and subsequently caused dephosphorylation of p70S6K and ribosomal protein RPS6 in the sensitive cell lines. However, in the resistant cell lines, AMPK activity and the mTOR pathway were unaffected by the treatment. We also noted that the resistant cell lines had elevated basal levels of phospho RPS6 and AKT. Inhibition of PI3K pathway enhanced the efficacy of 8-chloroadenosine across all cell lines. Our observations indicate that 8-chloroadenosine activity is associated with inhibition of the mTOR pathway, and that phospho RPS6 and PI3K pathway activation status may determine resistance. Among solid tumors, RCC is one of the few susceptible to mTOR inhibition. We thus infer that 8-chloroadenosine may be effective in RCC by activating AMPK and inhibiting the mTOR pathway.
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Affiliation(s)
- Alper Y. Kearney
- Department of Genitourinary Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - You-Hong Fan
- Department of Thoracic & Head and Neck Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Uma Giri
- Department of Thoracic & Head and Neck Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Babita Saigal
- Department of Thoracic & Head and Neck Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Varsha Gandhi
- Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - John V. Heymach
- Department of Thoracic & Head and Neck Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Amado J. Zurita
- Department of Genitourinary Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
- * E-mail:
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Patel H, Younis RH, Ord RA, Basile JR, Schneider A. Differential expression of organic cation transporter OCT-3 in oral premalignant and malignant lesions: potential implications in the antineoplastic effects of metformin. J Oral Pathol Med 2012; 42:250-6. [PMID: 22861817 DOI: 10.1111/j.1600-0714.2012.01196.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/12/2012] [Indexed: 01/01/2023]
Abstract
BACKGROUND Recent evidence indicates that metformin, a biguanide used as first-line treatment for type 2 diabetes, prevents the conversion of carcinogen-induced oral dysplasias into head and neck squamous cell carcinomas (HNSCC), most likely by inhibiting mammalian target of rapamycin complex 1 (mTORC1) oncogenic signaling. Whether metformin acts directly at the primary tumor site or indirectly by modulating hormonal secretion from extratumoral organs remains unknown. As organic cation transporters (OCT) belonging to the solute carrier 22A gene family, including OCT-1, OCT-2, and OCT-3, mediate metformin uptake and activity, it is critical to define what role they play in the antineoplastic activity of metformin. METHODS Immunohistochemical and immunoblotting techniques were used in normal, dysplastic and HNSCC tissues, and HNSCC cell lines, respectively, to determine OCTs expression levels. RESULTS We report that only OCT-3 was highly expressed in a number of HNSCC cell lines, oral epithelial dysplasias, and well to moderately differentiated HNSCC. Indeed, inhibition of OCT-3 expression and activity in HNSCC cells prevented metformin-induced AMP-activated protein kinase activation and mTORC1 pathway inhibition. Moreover, in oral dysplasias, high OCT-3 expression localized to epithelial compartments where mTORC1 signaling was also upregulated suggestive of a potential local effect of metformin. CONCLUSIONS The concept of using metformin as a chemopreventive agent to control head and neck carcinogenesis is promising. Further work is warranted to elucidate largely unexplored mechanisms of metformin uptake and pharmacologic action that may ultimately influence the selection of the most suitable patients who can benefit from metformin in head and neck cancer chemoprevention.
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Affiliation(s)
- Harsh Patel
- Department of Oncology and Diagnostic Sciences, University of Maryland School of Dentistry, Baltimore, MD, USA
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