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Li M, Robles-Planells C, Liu D, Graves SA, Vasquez-Martinez G, Mayoral-Andrade G, Lee D, Rastogi P, Marks BM, Sagastume EA, Weiss RM, Linn-Peirano SC, Johnson FL, Schultz MK, Zepeda-Orozco D. Pre-clinical evaluation of biomarkers for the early detection of nephrotoxicity following alpha-particle radioligand therapy. Eur J Nucl Med Mol Imaging 2024; 51:1395-1408. [PMID: 38095674 PMCID: PMC10957612 DOI: 10.1007/s00259-023-06559-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Accepted: 12/01/2023] [Indexed: 12/26/2023]
Abstract
PURPOSE Cancer treatment with alpha-emitter-based radioligand therapies (α-RLTs) demonstrates promising tumor responses. Radiolabeled peptides are filtered through glomeruli, followed by potential reabsorption of a fraction by proximal tubules, which may cause acute kidney injury (AKI) and chronic kidney disease (CKD). Because tubular cells are considered the primary site of radiopeptides' renal reabsorption and potential injury, the current use of kidney biomarkers of glomerular functional loss limits the evaluation of possible nephrotoxicity and its early detection. This study aimed to investigate whether urinary secretion of tubular injury biomarkers could be used as an additional non-invasive sensitive diagnostic tool to identify unrecognizable tubular damage and risk of long-term α-RLT nephrotoxicity. METHODS A bifunctional cyclic peptide, melanocortin 1 ligand (MC1L), labeled with [203Pb]Pb-MC1L, was used for [212Pb]Pb-MC1L biodistribution and absorbed dose measurements in CD-1 Elite mice. Mice were treated with [212Pb]Pb-MC1L in a dose-escalation study up to levels of radioactivity intended to induce kidney injury. The approach enabled prospective kidney functional and injury biomarker evaluation and late kidney histological analysis to validate these biomarkers. RESULTS Biodistribution analysis identified [212Pb]Pb-MC1L reabsorption in kidneys with a dose deposition of 2.8, 8.9, and 20 Gy for 0.9, 3.0, and 6.7 MBq injected [212Pb]Pb-MC1L doses, respectively. As expected, mice receiving 6.7 MBq had significant weight loss and CKD evidence based on serum creatinine, cystatin C, and kidney histological alterations 28 weeks after treatment. A dose-dependent urinary neutrophil gelatinase-associated lipocalin (NGAL, tubular injury biomarker) urinary excretion the day after [212Pb]Pb-MC1L treatment highly correlated with the severity of late tubulointerstitial injury and histological findings. CONCLUSION Urine NGAL secretion could be a potential early diagnostic tool to identify unrecognized tubular damage and predict long-term α-RLT-related nephrotoxicity.
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Affiliation(s)
- Mengshi Li
- Viewpoint Molecular Targeting, Inc. Dba Perspective Therapeutics, Coralville, IA, USA
| | - Claudia Robles-Planells
- Kidney and Urinary Tract Center, Abigail Wexner Research Institute at Nationwide Children's, Columbus, OH, USA
| | - Dijie Liu
- Viewpoint Molecular Targeting, Inc. Dba Perspective Therapeutics, Coralville, IA, USA
| | - Stephen A Graves
- Department of Radiology, The University of Iowa, Iowa City, IA, USA
| | - Gabriela Vasquez-Martinez
- Kidney and Urinary Tract Center, Abigail Wexner Research Institute at Nationwide Children's, Columbus, OH, USA
| | - Gabriel Mayoral-Andrade
- Kidney and Urinary Tract Center, Abigail Wexner Research Institute at Nationwide Children's, Columbus, OH, USA
| | - Dongyoul Lee
- Department of Physics and Chemistry, Korea Military Academy, Seoul, Republic of Korea
| | - Prerna Rastogi
- Department of Pathology, The University of Iowa, Iowa City, IA, USA
| | - Brenna M Marks
- Viewpoint Molecular Targeting, Inc. Dba Perspective Therapeutics, Coralville, IA, USA
| | - Edwin A Sagastume
- Viewpoint Molecular Targeting, Inc. Dba Perspective Therapeutics, Coralville, IA, USA
| | - Robert M Weiss
- Department of Internal Medicine, The University of Iowa, Iowa City, IA, USA
| | - Sarah C Linn-Peirano
- Kidney and Urinary Tract Center, Abigail Wexner Research Institute at Nationwide Children's, Columbus, OH, USA
- Department of Veterinary Biosciences, The Ohio State University College of Veterinary Medicine Columbus, Columbus, OH, USA
| | - Frances L Johnson
- Viewpoint Molecular Targeting, Inc. Dba Perspective Therapeutics, Coralville, IA, USA
| | - Michael K Schultz
- Viewpoint Molecular Targeting, Inc. Dba Perspective Therapeutics, Coralville, IA, USA.
- Department of Radiology, The University of Iowa, Iowa City, IA, USA.
- Department of Radiation Oncology, Free Radical, and Radiation Biology Program, The University of Iowa, Iowa City, IA, USA.
| | - Diana Zepeda-Orozco
- Kidney and Urinary Tract Center, Abigail Wexner Research Institute at Nationwide Children's, Columbus, OH, USA.
- Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA.
- Division of Nephrology and Hypertension, Nationwide Children's Hospital, Columbus, OH, USA.
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Lee D, Li M, Liu D, Baumhover NJ, Sagastume EA, Marks BM, Rastogi P, Pigge FC, Menda Y, Johnson FL, Schultz MK. Structural modifications toward improved lead-203/lead-212 peptide-based image-guided alpha-particle radiopharmaceutical therapies for neuroendocrine tumors. Eur J Nucl Med Mol Imaging 2024; 51:1147-1162. [PMID: 37955792 PMCID: PMC10881741 DOI: 10.1007/s00259-023-06494-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 10/26/2023] [Indexed: 11/14/2023]
Abstract
PURPOSE The lead-203 (203Pb)/lead-212 (212Pb) elementally identical radionuclide pair has gained significant interest in the field of image-guided targeted alpha-particle therapy for cancer. Emerging evidence suggests that 212Pb-labeled peptide-based radiopharmaceuticals targeting somatostatin receptor subtype 2 (SSTR2) may provide improved effectiveness compared to beta-particle-based therapies for neuroendocrine tumors (NETs). This study aims to improve the performance of SSTR2-targeted radionuclide imaging and therapy through structural modifications to Tyr3-octreotide (TOC)-based radiopharmaceuticals. METHODS New SSTR2-targeted peptides were designed and synthesized with the goal of optimizing the incorporation of Pb isotopes through the use of a modified cyclization technique; the introduction of a Pb-specific chelator (PSC); and the insertion of polyethylene glycol (PEG) linkers. The binding affinity of the peptides and the cellular uptake of 203Pb-labeled peptides were evaluated using pancreatic AR42J (SSTR2+) tumor cells and the biodistribution and imaging of the 203Pb-labeled peptides were assessed in an AR42J tumor xenograft mouse model. A lead peptide was identified (i.e., PSC-PEG2-TOC), which was then further evaluated for efficacy in 212Pb therapy studies. RESULTS The lead radiopeptide drug conjugate (RPDC) - [203Pb]Pb-PSC-PEG2-TOC - significantly improved the tumor-targeting properties, including receptor binding and tumor accumulation and retention as compared to [203Pb]Pb-DOTA0-Tyr3-octreotide (DOTATOC). Additionally, the modified RPDC exhibited faster renal clearance than the DOTATOC counterpart. These advantageous characteristics of [212Pb]Pb-PSC-PEG2-TOC resulted in a dose-dependent therapeutic effect with minimal signs of toxicity in the AR42J xenograft model. Fractionated administrations of 3.7 MBq [212Pb]Pb-PSC-PEG2-TOC over three doses further improved anti-tumor effectiveness, resulting in 80% survival (70% complete response) over 120 days in the mouse model. CONCLUSION Structural modifications to chelator and linker compositions improved tumor targeting and pharmacokinetics (PK) of 203/212Pb peptide-based radiopharmaceuticals for NET theranostics. These findings suggest that PSC-PEG2-TOC is a promising candidate for Pb-based targeted radionuclide therapy for NETs and other types of cancers that express SSTR2.
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Affiliation(s)
- Dongyoul Lee
- Department of Physics and Chemistry, Korea Military Academy, Seoul, Republic of Korea
| | - Mengshi Li
- Perspective Therapeutics, Inc., Coralville, IA, USA
| | - Dijie Liu
- Perspective Therapeutics, Inc., Coralville, IA, USA
| | | | | | | | - Prerna Rastogi
- Department of Pathology, The University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - F Christopher Pigge
- Department of Chemistry, The University of Iowa, ML B180 FRRBP, 500 Newton Road, Iowa City, IA, 52240, USA
| | - Yusuf Menda
- Department of Radiology, The University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | | | - Michael K Schultz
- Perspective Therapeutics, Inc., Coralville, IA, USA.
- Department of Chemistry, The University of Iowa, ML B180 FRRBP, 500 Newton Road, Iowa City, IA, 52240, USA.
- Department of Radiology, The University of Iowa Hospitals and Clinics, Iowa City, IA, USA.
- Department of Radiation Oncology, The University of Iowa Hospitals and Clinics, Iowa City, IA, USA.
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Li M, Robles-Planells C, Liu D, Graves SA, Vasquez-Martinez G, Mayoral-Andrade G, Lee D, Rastogi P, Marks BM, Sagastume EA, Weiss RM, Linn-Peirano SC, Johnson FL, Schultz MK, Zepeda-Orozco D. Pre-clinical Evaluation of Biomarkers for Early Detection of Nephrotoxicity Following Alpha-particle Radioligand Therapy. bioRxiv 2023:2023.09.27.559789. [PMID: 37808634 PMCID: PMC10557737 DOI: 10.1101/2023.09.27.559789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Purpose Cancer treatment with alpha-emitter-based radioligand therapies (α-RLTs) demonstrates promising tumor responses. Radiolabeled peptides are filtered through glomeruli, followed by potential reabsorption of a fraction by proximal tubules, which may cause acute kidney injury (AKI) and chronic kidney disease (CKD). Because tubular cells are considered the primary site of radiopeptides' renal reabsorption and potential injury, the current use of kidney biomarkers of glomerular functional loss limits the evaluation of possible nephrotoxicity and its early detection. This study aimed to investigate whether urinary secretion of tubular injury biomarkers could be used as additional non-invasive sensitive diagnostic tool to identify unrecognizable tubular damage and risk of long-term α-RLTs nephrotoxicity. Methods A bifunctional cyclic peptide, melanocortin ligand-1(MC1L), labeled with [ 203 Pb]Pb-MC1L, was used for [ 212 Pb]Pb-MC1L biodistribution and absorbed dose measurements in CD-1 Elite mice. Mice were treated with [ 212 Pb]Pb-MC1L in a dose escalation study up to levels of radioactivity intended to induce kidney injury. The approach enabled prospective kidney functional and injury biomarker evaluation and late kidney histological analysis to validate these biomarkers. Results Biodistribution analysis identified [ 212 Pb]Pb-MC1L reabsorption in kidneys with a dose deposition of 2.8, 8.9, and 20 Gy for 0.9, 3.0, and 6.7 MBq injected [ 212 Pb]Pb-MC1L doses, respectively. As expected, mice receiving 6.7 MBq had significant weight loss and CKD evidence based on serum creatinine, cystatin C, and kidney histological alterations 28 weeks after treatment. A dose-dependent urinary Neutrophil gelatinase-associated lipocalin (NGAL, tubular injury biomarker) urinary excretion the day after [ 212 Pb]Pb-MC1L treatment highly correlated with the severity of late tubulointerstitial injury and histological findings. Conclusion urine NGAL secretion could be a potential early diagnostic tool to identify unrecognized tubular damage and predict long-term α-RLT-related nephrotoxicity.
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Li M, Baumhover NJ, Liu D, Cagle BS, Boschetti F, Paulin G, Lee D, Dai Z, Obot ER, Marks BM, Okeil I, Sagastume EA, Gabr M, Pigge FC, Johnson FL, Schultz MK. Preclinical Evaluation of a Lead Specific Chelator (PSC) Conjugated to Radiopeptides for 203Pb and 212Pb-Based Theranostics. Pharmaceutics 2023; 15:414. [PMID: 36839736 PMCID: PMC9966725 DOI: 10.3390/pharmaceutics15020414] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 12/30/2022] [Accepted: 01/14/2023] [Indexed: 01/28/2023] Open
Abstract
203Pb and 212Pb have emerged as promising theranostic isotopes for image-guided α-particle radionuclide therapy for cancers. Here, we report a cyclen-based Pb specific chelator (PSC) that is conjugated to tyr3-octreotide via a PEG2 linker (PSC-PEG-T) targeting somatostatin receptor subtype 2 (SSTR2). PSC-PEG-T could be labeled efficiently to purified 212Pb at 25 °C and also to 212Bi at 80 °C. Efficient radiolabeling of mixed 212Pb and 212Bi in PSC-PEG-T was also observed at 80 °C. Post radiolabeling, stable Pb(II) and Bi(III) radiometal complexes in saline were observed after incubating [203Pb]Pb-PSC-PEG-T for 72 h and [212Bi]Bi-PSC-PEG-T for 5 h. Stable [212Pb]Pb-PSC-PEG-T and progeny [212Bi]Bi-PSC-PEG-T were identified after storage in saline for 24 h. In serum, stable radiometal/radiopeptide were observed after incubating [203Pb]Pb-PSC-PEG-T for 55 h and [212Pb]Pb-PSC-PEG-T for 24 h. In vivo biodistribution of [212Pb]Pb-PSC-PEG-T in tumor-free CD-1 Elite mice and athymic mice bearing AR42J xenografts revealed rapid tumor accumulation, excellent tumor retention and fast renal clearance of both 212Pb and 212Bi, with no in vivo redistribution of progeny 212Bi. Single-photon emission computed tomography (SPECT) imaging of [203Pb]Pb-PSC-PEG-T and [212Pb]Pb-PSC-PEG-T in mice also demonstrated comparable accumulation in AR42J xenografts and renal clearance, confirming the theranostic potential of the elementally identical 203Pb/212Pb radionuclide pair.
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Affiliation(s)
- Mengshi Li
- Viewpoint Molecular Targeting, Inc., 2500 Crosspark Road, Coralville, IA 52241, USA
| | | | - Dijie Liu
- Viewpoint Molecular Targeting, Inc., 2500 Crosspark Road, Coralville, IA 52241, USA
| | - Brianna S. Cagle
- Viewpoint Molecular Targeting, Inc., 2500 Crosspark Road, Coralville, IA 52241, USA
| | | | | | - Dongyoul Lee
- Department of Physics and Chemistry, Korea Military Academy, Seoul 01805, Republic of Korea
| | - Zhiming Dai
- Department of Chemistry, The University of Iowa, Iowa City, IA 52240, USA
| | - Ephraim R. Obot
- Viewpoint Molecular Targeting, Inc., 2500 Crosspark Road, Coralville, IA 52241, USA
| | - Brenna M. Marks
- Viewpoint Molecular Targeting, Inc., 2500 Crosspark Road, Coralville, IA 52241, USA
| | - Ibrahim Okeil
- Viewpoint Molecular Targeting, Inc., 2500 Crosspark Road, Coralville, IA 52241, USA
| | - Edwin A. Sagastume
- Viewpoint Molecular Targeting, Inc., 2500 Crosspark Road, Coralville, IA 52241, USA
| | - Moustafa Gabr
- Department of Radiology, Weill Cornell Medicine, New York, NY 10021, USA
| | | | - Frances L. Johnson
- Viewpoint Molecular Targeting, Inc., 2500 Crosspark Road, Coralville, IA 52241, USA
| | - Michael K. Schultz
- Viewpoint Molecular Targeting, Inc., 2500 Crosspark Road, Coralville, IA 52241, USA
- Department of Radiology, The University of Iowa, Iowa City, IA 52246, USA
- Department of Radiation Oncology, The University of Iowa, Iowa City, IA 52246, USA
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Li M, Liu D, Lee D, Cheng Y, Baumhover NJ, Marks BM, Sagastume EA, Ballas ZK, Johnson FL, Morris ZS, Schultz MK. Targeted Alpha-Particle Radiotherapy and Immune Checkpoint Inhibitors Induces Cooperative Inhibition on Tumor Growth of Malignant Melanoma. Cancers (Basel) 2021; 13:cancers13153676. [PMID: 34359580 PMCID: PMC8345035 DOI: 10.3390/cancers13153676] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 07/13/2021] [Accepted: 07/16/2021] [Indexed: 12/23/2022] Open
Abstract
Simple Summary Radiation therapy and immune checkpoint inhibitors (ICIs) have been demonstrated to cooperatively activate adaptive anti-tumor immunity with curative potential in preclinical models of melanoma. Receptor-targeted radionuclide therapy can be systemically injected to selectively deliver ionizing radiation to tumor sites throughout the body, potentially rendering all tumor sites more susceptible to anti-tumor immune response. In this study, we demonstrated the feasibility of delivering alpha-particle radiation to murine melanoma tumors using a 212Pb radiolabeled peptide [212Pb]VMT01 that targets the melanocortin 1 receptor (MC1R). Our data showed anti-tumor cooperation between [212Pb]VMT01 and ICIs in melanoma, mediated by induction of tumor-specific immunity. The immunogenicity of [212Pb]VMT01 in melanoma was also evidenced by enhanced tumor infiltrating lymphocytes and tumor vaccination assays. Abstract Radiotherapy can facilitate the immune recognition of immunologically “cold” tumors and enhance the efficacy of anti-PD-1 and anti-CTLA-4 immune checkpoint inhibitors (ICIs) in melanoma. Systemic administration of receptor-targeted radionuclide therapy has the potential to selectively deliver radionuclides to multiple tumors throughout the body in metastatic settings. By triggering immunologic cell death and increasing the immune susceptibility of surviving tumor cells in these locations, targeted radionuclide therapies may overcome resistance to ICIs and render immunologically “cold” tumors throughout the body responsive to ICIs and immunologically “hot”. Here, we show the anti-tumor cooperation of targeted α-particle radionuclide therapy (α-TRT) and ICIs in preclinical models of melanoma. Melanocortin 1 receptor (MC1R)-targeted radiopeptide [212Pb]VMT01 was employed to deliver α-radiation to melanoma tumors in mice. A single injection of 4.1 MBq [212Pb]VMT01 significantly slowed the tumor growth of B16-F10 melanoma and the combination of [212Pb]VMT01 and ICIs induced a cooperative anti-tumor effect leading to 43% complete tumor response with no sign of malignancy on autopsy. Animals with complete response developed anti-tumor immunity to reject further tumor inoculations. This therapeutic cooperation was completely abolished in RAG1 KO mice, which are deficient in T-cell maturation. In addition, the anti-tumor cooperation was compromised when fractionated [212Pb]VMT01 was used in the combination. We also demonstrated that [212Pb]VMT01 induced immunogenic cell death in tumor vaccination assays and in vitro exposure to [212Pb]VMT01 sensitized immunotolerant melanoma to ICIs treatment in vivo. Enhanced tumor infiltrating CD3+, CD4+, CD8+ lymphocytes were observed following injection of 1.4 MBq [212Pb]VMT01. Overall, we demonstrated anti-tumor cooperation between α-TRT and ICIs in melanoma that is mediated by tumor specific immunity.
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Affiliation(s)
- Mengshi Li
- Viewpoint Molecular Targeting, Inc., Coralville, IA 52241, USA; (M.L.); (D.L.); (N.J.B.); (B.M.M.); (E.A.S.); (F.L.J.)
- Department of Radiology, University of Iowa, Iowa City, IA 52242, USA;
| | - Dijie Liu
- Viewpoint Molecular Targeting, Inc., Coralville, IA 52241, USA; (M.L.); (D.L.); (N.J.B.); (B.M.M.); (E.A.S.); (F.L.J.)
- Department of Radiology, University of Iowa, Iowa City, IA 52242, USA;
| | - Dongyoul Lee
- Department of Radiology, University of Iowa, Iowa City, IA 52242, USA;
| | - Yinwen Cheng
- Interdisciplinary Graduate Program in Human Toxicology, University of Iowa, Iowa City, IA 52242, USA;
- Department of Pathology, University of Iowa, Iowa City, IA 52242, USA
| | - Nicholas J. Baumhover
- Viewpoint Molecular Targeting, Inc., Coralville, IA 52241, USA; (M.L.); (D.L.); (N.J.B.); (B.M.M.); (E.A.S.); (F.L.J.)
- Department of Radiology, University of Iowa, Iowa City, IA 52242, USA;
| | - Brenna M. Marks
- Viewpoint Molecular Targeting, Inc., Coralville, IA 52241, USA; (M.L.); (D.L.); (N.J.B.); (B.M.M.); (E.A.S.); (F.L.J.)
| | - Edwin A. Sagastume
- Viewpoint Molecular Targeting, Inc., Coralville, IA 52241, USA; (M.L.); (D.L.); (N.J.B.); (B.M.M.); (E.A.S.); (F.L.J.)
| | - Zuhair K. Ballas
- Department of Internal Medicine, University of Iowa, Iowa City, IA 52242, USA;
| | - Frances L. Johnson
- Viewpoint Molecular Targeting, Inc., Coralville, IA 52241, USA; (M.L.); (D.L.); (N.J.B.); (B.M.M.); (E.A.S.); (F.L.J.)
- Department of Internal Medicine, University of Iowa, Iowa City, IA 52242, USA;
| | - Zachary S. Morris
- Department of Human Oncology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705, USA;
| | - Michael K. Schultz
- Viewpoint Molecular Targeting, Inc., Coralville, IA 52241, USA; (M.L.); (D.L.); (N.J.B.); (B.M.M.); (E.A.S.); (F.L.J.)
- Department of Radiology, University of Iowa, Iowa City, IA 52242, USA;
- Interdisciplinary Graduate Program in Human Toxicology, University of Iowa, Iowa City, IA 52242, USA;
- Department of Pediatrics, University of Iowa, Iowa City, IA 52242, USA
- Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA
- Correspondence: ; Tel.: +1-(865)-356-1861
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Li M, Liu D, Lee D, Kapoor S, Gibson-Corley KN, Quinn TP, Sagastume EA, Mott SL, Walsh SA, Acevedo MR, Johnson FL, Schultz MK. Enhancing the Efficacy of Melanocortin 1 Receptor-Targeted Radiotherapy by Pharmacologically Upregulating the Receptor in Metastatic Melanoma. Mol Pharm 2019; 16:3904-3915. [PMID: 31318566 DOI: 10.1021/acs.molpharmaceut.9b00512] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Melanocortin 1 receptor (MC1R) is under investigation as a target for drug delivery for metastatic melanoma therapy and imaging. The purpose of this study was to determine the potential of using BRAF inhibitors (BRAFi) and histone deacetylase inhibitors (HDACi) to enhance the delivery of MC1R-targeted radiolabeled peptide ([212Pb]DOTA-MC1L) by pharmacologically upregulating the MC1R expression in metastatic melanoma cells and tumors. MC1R expression was analyzed in de-identified melanoma biopsies by immunohistochemical staining. Upregulation of MC1R expression was determined in BRAFV600E cells (A2058) and BRAF wild-type melanoma cells (MEWO) by quantitative real-time polymerase chain reaction, flow cytometry, and receptor-ligand binding assays. The role of microphthalmia-associated transcription factor (MITF) in the upregulation of MC1R was also examined in A2058 and MEWO cells. The effectiveness of [212Pb]DOTA-MC1L α-particle radiotherapy in combination with BRAFi and/or HDACi was determined in athymic nu/nu mice bearing A2058 and MEWO human melanoma xenografts. High expression of MC1R was observed in situ in clinical melanoma biopsies. BRAFi and HDACi significantly increased the MC1R expression (up to 10-fold in mRNA and 4-fold in protein levels) via MITF-dependent pathways, and this increase led to enhanced ligand binding on the cell surface. Inhibition of MITF expression antagonized the upregulation of MC1R in both BRAFV600E and BRAFWT cells. Combining [212Pb]DOTA-MC1L with BRAFi and/or HDACi improved the tumor response by increasing the delivery of 212Pb α-particle emissions to melanoma tumors via augmented MC1R expression. These data suggest that FDA-approved HDACi and BRAFi could improve the effectiveness of MC1R-targeted therapies by enhancing drug delivery via upregulated MC1R.
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Affiliation(s)
| | | | | | | | | | - Thomas P Quinn
- Department of Biochemistry , University of Missouri , Columbia , Missouri 65211 , United States
| | - Edwin A Sagastume
- Viewpoint Molecular Targeting, Inc. , Coralville , Iowa 52241 , United States
| | | | | | | | - Frances L Johnson
- Viewpoint Molecular Targeting, Inc. , Coralville , Iowa 52241 , United States
| | - Michael K Schultz
- Viewpoint Molecular Targeting, Inc. , Coralville , Iowa 52241 , United States
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