Synthesis and Preclinical Evaluation of [⁶⁸Ga]SP94 for Micro-PET Imaging of GRP78 Expression in Hepatocellular Carcinoma

Abstract

Glucose-regulated protein 78 (GRP78) is overexpressed in a wide variety of solid tumors, serving as a well-characterized target for tumor imaging or therapy. In this work, we developed a GRP78-responsive radiotracer (DOTA-68Ga)-Gly-Gly-Gly-Ser-Phe-Ser-Ile-Ile-His-Thr-Pro-Ile-Leu-Pro-Leu-Gly-Gly-Cys ([68Ga]­SP94) for hepatocellular carcinoma (HCC) micro-PET imaging. DOTA-SP94 was synthesized by solid phase synthesis and then radiolabeled with 68GaCl3 with >99% radiochemical purity. The expression levels of GRP78 in HepG2 cells were confirmed by Western blotting. In vitro and in vivo study of [68Ga]­SP94 showed high stability and high uptake in GRP78-overexpressing HepG2 cells and tumor, fast clearance, and low nontarget uptake. Micro-PET images showed excellent tumor accumulation of [68Ga]­SP94 in the HepG2-implanted nude mice tumor model. Additionally, the radiotracer uptake in HepG2 tumors can be blocked by unlabeled DOTA-SP94, suggesting that the tracer uptake by HCC was receptor-mediated. We envision that our radiotracer can be used for noninvasive imaging of HCC and is worthy of further clinical investigations.

Targeted Wolfram-Doped Polypyrrole for Photonic Hyperthermia-Synergized Radiotherapy

“…WPPy@IR780-treated HepG2 cells showed relatively faint red fluorescence signals even after 9 h of incubation, which were equivalent to that of free IR780. In contrast, the cellular uptake efficiency of the WPPy@IR780@SP94 group gradually increased with the time extension, well confirming SP94-enhanced endocytosis via specific interactions with GRP78 receptors overexpressed on HepG2 cells (Figure D). − Encouraged by the strong optical absorbance, excellent photothermal performance, and impressive cellular uptake of WPPy@SP94, its antitumor effects were further tested by a CCK-8 test. The relative cell viability of both cancer cells (HepG2 and HCC-LM3 cells) and normal cells (HUVEC and MIHA cells) all remained above 85% after 24 or 48 h of incubation with WPPy@SP94, suggesting the outstanding biocompatibility (Figure A,B).…”

Synthesis and Evaluation of [18F]AlF-NOTA-c-DVAP: A Novel PET Probe for Imaging GRP78 in Cancer

“…11 A variety of PET probes have been developed for preclinical studies. For example, [ 188 Re]-liposomes linked to csGRP78 peptides increased uptake in tumor imaging and therapeutic efficacy than its nontargeted counterpart; 21 [ 64 Cu]Gu-DOTA-MAb159 utilized for pancreatic cancer xenografts imaging; 12 [ 68 Ga]Ga-SP94 can perform for HCC imaging, 14 [ 68 Ga]Ga-DOTA-VAP and [ 18 F]AlF-NOTA-D VAP can noninvasively and accurately classify TNBC from other breast cancer subtypes.…”

“…In comparison with [ 68 Ga]SP94, whose tumor uptake decreased to background levels at later time points, [ 18 F]AlF-NOTAc-D VAP exhibited remarkably better tumor retention, distinguishing tumor from background at 2 h p.i. 14 [ 64 Cu]DOTA-Mab159 shows higher tumor uptake and retention compared to [ 68 Ga]DOTA-VAP and [ 68 Ga]SP94. 12 However, radiolabeled antibodies lead to high abdominal background signal, such as high liver accumulation, which could hamper tumor visualization and cause radiation damage.…”

“…Zhao et al constructed a Ga-68-radiolabeled DOTA-VAP conjugate ([ 68 Ga]­Ga-DOTA-VAP) based on VAP peptide (peptide sequence: SNTRVAP) and provided a practical approach for the accurate classification of triple-negative breast cancer from other breast cancer subtypes . Moreover, Xu et al developed a radiotracer [ 68 Ga]­Ga-SP94 (peptide sequence: SFSIIHTPILPL) for hepatocellular carcinoma (HCC) micro-PET imaging . However, both probes have high uptake in the liver, low target/nontarget ratio, and poor stability in vivo.…”

“…13 Moreover, Xu et al developed a radiotracer [ 68 Ga]Ga-SP94 (peptide sequence: SFSIIHTPILPL) for hepatocellular carcinoma (HCC) micro-PET imaging. 14 However, both probes have high uptake in the liver, low target/nontarget ratio, and poor stability in vivo.…”