Evaluation of ^99mTc-HYNIC-VCAM-1_scFv as a Potential Qualitative and Semiquantitative Probe Targeting Various Tumors

Vascular cell adhesion molecule 1 (VCAM-1) is overexpressed in varieties of cancers. This study aimed to evaluate the application of a single chain variable fragment (scFv) of anti-VCAM-1 antibody labeled with ^99mTc as a possible imaging agent in several tumors. VCAM-1 scFv was labeled with ^99mTc using succinimidyl 6-hydrazinium nicotinate hydrochloride, and ^99mTc-HYNIC-VCAM-1_scFv was successfully synthesized with a high radiolabeling yield. VCAM-1 expression was evaluated in six cell lines by immunofluorescence staining. In vitro binding assays showed different binding affinities of ^99mTc-HYNIC-VCAM-1_scFv in different tumor cell lines, with high uptake in B16F10 melanoma and HT1080 fibrosarcoma cells, which was consistent with immunofluorescence staining results. In vivo SPECT planar imaging demonstrated that B16F10 and HT1080 tumors could be clearly visualized. Less intense uptake was observed in human SKOV3.ip ovarian tumor, and weak uptake was observed in human A375m melanoma, MDA-MB-231 breast cancer, and 786-O renal tumors. These findings were confirmed by biodistribution and immunofluorescence studies. High uptake by B16F10 tumors was inhibited by excess unlabeled VCAM-1_scFv. ^99mTc-HYNIC-VCAM-1_scFv, which selectively binds to VCAM-1, can provide a qualitative and semiquantitative method for noninvasive evaluation of VCAM-1 expression by tumors.