Radiosynthesis of carbon-11-labeled camptothecin derivatives as potential positron emission tomography tracers for imaging of topoisomerase I in cancers

FL118: A potential bladder cancer therapeutic compound targeting H2A.X identified through library screening

The treatment of bladder cancer is limited by low drug efficacy and drug resistance. Hence, this study aimed to screen and identify potential drug precursors and investigate their mechanism of action. A set of camptothecin derivatives showing high anti-tumor potential was selected from early-stage research or literature and synthesized to construct a compound library. A total of 135 compounds were screened in T24 and J82 cells, revealing that FL118 significantly inhibited the proliferation of GC (gemcitabine + cisplatin)-sensitive/insensitive cells. FL118 exhibited excellent penetration and killing ability in organoids and three GC-insensitive patient-derived xenografts. Chemical proteomic and docking calculations were employed to identify binding proteins, indicating that FL118 can bind into H2A.X and its entwined DNA. The results of Cellular thermal shift assay and surface plasmon resonance (Kd = 3.77E-6) support the above findings. Fluorescence localization revealed widespread binding of FL118 within the cell nucleus. Furthermore, WB showed that FL118 increased cellular DNA damage, resulting in significant cell cycle inhibition. The binding of FL118 to H2A.X hindered the damage repair process, leading to apoptosis. Controllable adverse reactions were observed in mice treated with FL118. In conclusion, FL118 may be a superior anti-bladder cancer compound that acts as a molecular glue binding to both H2A.X and DNA. The resistance mediated by the DNA damage repair to DNA damage caused by GC regimen can be reversed by FL118. This distinct mechanism of FL118 has the potential to complement existing mainstream treatment approaches for bladder cancer.

Development of a RNA-protein complex based smart drug delivery system for 9-hydroxycamptothecin

Camptothecin (CPT) is a monoterpenoid indole alkaloid with a wide spectrum of anticancer activity. However, its application is hindered by poor solubility, lack of targeting specificity, and severe side effects. Structural derivatization of CPT and the development of suitable drug delivery systems are potential strategies for addressing these issues. In this study, we discovered that the protein Cytochrome P450 Family 1 Subfamily A Member 1 (CYP1A1) from Homo sapiens catalyzes CPT to yield 9-hydroxycamptothecin (9-HCPT), which exhibits increased water solubility and cytotoxicity. We then created a RNA-protein complex based drug delivery system with enzyme and pH responsiveness and improved the targeting and stability of the nanomedicine through protein module assembly. The subcellular localization of nanoparticles can be visualized using fluorescent RNA probes. Our results not only identified the protein CYP1A1 responsible for the structural derivatization of CPT to synthesize 9-HCPT but also offered potential strategies for enhancing the utilization of silk-based drug delivery systems in tumor therapy.

Identification and characterization of camptothecin tailoring enzymes in Nothapodytes tomentosa

Camptothecin is a complex monoterpenoid indole alkaloid with remarkable antitumor activity. Given that two C-10 modified camptothecin derivatives, topotecan and irinotecan, have been approved as potent anticancer agents, there is a critical need for methods to access other aromatic ring-functionalized congeners (e.g., C-9, C-10, etc.). However, contemporary methods for chemical oxidation are generally harsh and low-yielding when applied to the camptothecin scaffold, thereby limiting the development of modified derivatives. Reported herein, we have identified four tailoring enzymes responsible for C-9 modifications of camptothecin from Nothapodytes tomentosa, via metabolomic and transcriptomic analysis. These consist of a cytochrome P450 (NtCPT9H) which catalyzes the regioselective oxidation of camptothecin to 9-hydroxycamptothecin, as well as two methyltransferases (NtOMT1/2, converting 9-hydroxycamptothecin to 9-methoxycamptothecin), and a uridine diphosphate-glycosyltransferase (NtUGT5, decorating 9-hydroxycamptothecin to 9-β-D-glucosyloxycamptothecin). Importantly, the critical residues that contribute to the specific catalytic activity of NtCPT9H have been elucidated through molecular docking and mutagenesis experiments. This work provides a genetic basis for producing camptothecin derivatives through metabolic engineering. This will hasten the discovery of novel C-9 modified camptothecin derivatives, with profound implications for pharmaceutical manufacture.

Simple automated radiosynthesis of 10-[11C]methoxy-20(S)-camptothecin and biodistribution in normal mice

10-[(11)C]methoxy-20(S)-camptothecin was synthesized automatically. The radiochemical yield was 30%-50% (all calculated at EOB, n=20) with [(11)C]methyl triflate as a methylating agent. The radiochemical purity was greater than 96%, and the specific activity was 8.72±2.18 GBq/μmoL at EOS. Biodistribution showed that 10-[(11)C]methoxy-20(S)-camptothecin is characterized by quick clearance from the blood and by significant uptake in the liver (5.72±1.92% ID/g at 15 min), intestines (2.43±0.38% ID/g at 15 min), and kidney (1.57±0.85% ID/g at 15 min). Micro-PET imaging clearly showed high radioactivity accumulation in liver, intestines and bladder, indicating that the primary modes of excretion of the radiotracer are through the hepatobiliary system and, to a lesser extent, through the renal system.

Synthesis of radiolabeled stilbene derivatives as new potential PET probes for aryl hydrocarbon receptor in cancers

New carbon-11 and fluorine-18 labeled stilbene derivatives, cis-3,5-dimethoxy-4'-[11C]methoxystilbene (4'-[11C]8a), cis-3,4',5-trimethoxy-3'-[11C]methoxystilbene (3'-[11C]8b), trans-3,5-dimethoxy-4'-[11C]methoxystilbene (4'-[11C]10a), trans-3,4',5-trimethoxy-3'-[11C]methoxystilbene (3'-[11C]10b), cis-3,5-dimethoxy-4'-[18F]fluorostilbene (4'-[18F]12a), and trans-3,5-dimethoxy-4'-[18F]fluorostilbene (4'-[18F]13a), were designed and synthesized as potential PET probes for aryl hydrocarbon receptor (AhR) in cancers.

Potent antitumor activity of 10-methoxy-9-nitrocamptothecin

The present data showed that 10-methoxy-9-nitrocamptothecin (MONCPT), a family of camptothecin analogues, possessed high antitumor activity in vitro and in vivo. Cytotoxicity assays showed that MONCPT was a potential and highly efficient antitumor compound with IC50 values of 0.1 to 500 nmol/L in nine tumor cell lines. The high cytotoxic potency of MONCPT was paralleled with its ability to increase the cellular accumulation of DNA damage. DNA relaxation assay also showed that MONCPT exerted high potency as a topoisomerase I inhibitor. Moreover, administration of MONCPT (5-20 mg/kg) for 15 to 17 days significantly inhibited tumor growth in human androgen-independent prostate tumor (PC3) and human non-small cell lung tumor (A549) xenografts; the inhibition rates ranged from 29.6% to 98%. The cytotoxic effect of 1,000 nmol/L of MONCPT in PC3 cells was associated with causing an arrest in G0-G1 phase, whereas that of 10 and 100 nmol/L MONCPT was relative to a persistent block in G2-M phase. Furthermore, down-regulation of CDK2, CDK4, and cyclin D1 was observed in PC3 cells treated with 1,000 nmol/L of MONCPT, whereas overexpression of CDK7, CDK1, and cyclin B1 was seen in PC3 cells treated with 10 and 100 nmol/L of MONCPT. These results suggested that cell cycle regulation might contribute to the anticancer properties of MONCPT and strongly support the further anticancer development of MONCPT.

Synthesis of carbon-11 and fluorine-18 labeled N-acetyl-1-aryl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline derivatives as new potential PET AMPA receptor ligands

New carbon-11 and fluorine-18 labeled N-acetyl-1-aryl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline derivatives were designed and synthesized as potential positron emission tomography AMPA (2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid) receptor ligands to image brain diseases. The single crystal structure of the most potent compound N-acetyl-1-(4'-chlorophenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (5a) is first reported.