Carbonic Anhydrase IX Targeting Mn(II)-Based Magnetic Resonance Molecular Imaging Probe for Hypoxia Tumors

Abstract

Physiological hypoxic conditions in the tumor microenvironment and consequential overexpression of carbonic anhydrase IX (CA IX) are two characteristics shared by numerous types of solid malignant tumors. Early detection with hypoxia assessment is crucial to improve the prognosis and therapy outcomes of hypoxia tumors. Herein, using acetazolamide (AZA) as a CA IX-targeting moiety, we design and synthesize an Mn(II)-based MR imaging probe (named AZA-TA-Mn) incorporating AZA and two Mn(II) chelates of Mn-TyEDTA on a rigid triazine (TA) scaffold. The per Mn relaxivity of AZA-TA-Mn is 2-fold higher than its monomeric Mn-TyEDTA, which allows it for lowdose imaging of hypoxic tumors. In a xenograft mice model of esophageal squamous cell carcinoma (ESCC), a low dosage of AZA-TA-Mn (0.05 mmol/kg) can selectively produce prolonged and stronger contrast enhancement in the tumor compared to the non-specific Gd-DTPA (0.1 mmol/kg). A competition study of co-injection of free AZA and Mn(II) probes confirms the in vivo tumor selectivity of AZA-TA-Mn, resulting in a more than 2.5fold decreased tumor-to-muscle contrast-to-noise ratio (ΔCNR) at 60 min post-injection. MR imaging results were further supported by the quantitative analysis of Mn tissue levels, as the co-injection of free AZA resulted in significantly reduced Mn accumulation in tumor tissues. Finally, immunofluorescence staining of tissue sections confirms the positive correlation between the tumor accumulation of AZA-TA-Mn and CA IX overexpression. Hence, using CA IX as the hypoxia biomarker, our results illustrate a practical strategy for the development of novel imaging probes for hypoxic tumors.

Chiral Gd-DOTA as a Versatile Platform for Hepatobiliary and Tumor Targeting MRI Contrast Agents

“…Rapid growth of tumor leads to dysfunctional microvasculature, generally featured with hypoxia, which protects tumors from therapy, thus with it emerging as an inevitable biomarker for consideration in developing tumor specific CAs. − For example, sulfonamides have been widely incorporated in CAs for targeting hypoxia via interacting with the carbonic anhydrase IX/XII overexpressed in hypoxic cancers. − Yet, the lack of selectivity among isoforms of human carbonic anhydrase usually brought unwanted side effects in their therapeutic applications . 3-Nitrobenzene-sulfonamide analogue exhibited better inhibition on tumor associated carbonic anhydrase IX/XII, and the reduction of nitro to amine group under hypoxic environment did not only improve the selectivity but also exerted enhanced cytotoxicity to tumor cells. , The overexpression of various glucose transporters on cell membrane of cancers would be another ideal biomarker for targeting .…”

Facile Synthesis of Rigid Binuclear Manganese Complexes for Magnetic Resonance Angiography and SLC39A14-Mediated Hepatic Imaging

“…Finally, the exact ratio of ligand to manganese­(II) ion was determined by NMR titration of an aliquot ligand solution with manganese­(II) ion according to previous literature (Figure S27). − Also, the final complexes were prepared by mixing the ligand and MnCl 2 ·4H 2 O and adjusting the pH to 7.4 using a 1 M NaOH aqueous solution. NMR and mass spectrometry (Figures S1–S24) were used to characterize all intermediates, and the final manganese­(II) complexes were confirmed by mass spectrometry.…”

Imaging of Carbonic Anhydrase Level in Epilepsy with an Environment-Sensitive Fluorescent Probe

“…To date, fluorescent probes are considered to be one of the most powerful tools for monitoring biological species in biological systems. – On account of their desirable selectivity and sensitivity, excellent biocompatibility, and favorable spatial and temporal resolution, they have got a wide application in the CA detection. – Up to now, dozens of different types of CA fluorescent probes have been reported, – e.g., direct-conjugated recognition group on fluorophores; , one- or two-step photoaffinity probes; and one- or two-step electrophilic reaction probes. , However, in view of the availability, stability, and structural characterization clarity of CAs, most researchers regard CAs as model proteins for highlighting more modular research in probe designs. – In addition, the emission wavelength of the existing CAs environment-sensitive probes is short, which limits the in-depth application of probes in living tissues. ,, A red or near-infrared fluorescent probe (>600 nm) allows penetration into deep tissues with little autofluorescence interference, which is suitable for imaging CAs in living cells or tissues and is an ideal choice for exploring biological systems. – …”