Development and preliminary evaluation of an integrin α 2 β 1 -targeted PET probe as a supplement and alternative of PSMA imaging for prostate cancer.

An integrin α ₂ β ₁ -targeted PET probe ( ⁶⁸ Ga-IABtP) was developed to serve as a supplement and alternative of PSMA imaging for prostate cancer. ⁶⁸ Ga-IABtP was synthesized by labeling the precursor peptide with ⁶⁸ Ga with 93% labeling yield and 4.14 MBq/μg specific radioactivity. ⁶⁸ Ga-IABtP showed no specific uptake in LNCaP prostate cancer cell with low integrin α ₂ β ₁ expression but significantly increased uptake in PC-3 prostate cancer cell with high integrin α ₂ β ₁ expression, which could be specifically blocked by the integrin α ₂ β ₁ monoclonal antibody. The efflux experiments demonstrated that ⁶⁸ Ga-IABtP could rapidly penetrate into PC-3 cell after cell binding, thereby prolonging the residence time in the tumor and allow enough time for probe clearance from the circulation and non-specific organs. The biodistribution study indicated that ⁶⁸ Ga-IABtP showed no specific accumulation in non-target organs and was quickly cleared from the kidney. The in vivo PET-CT imaging demonstrated that ⁶⁸ Ga-IABtP showed no specific uptake in LNCaP tumor but could specifically accumulate in the PC-3 tumor, and was rapidly cleared from spleen, intestine, kidney and liver, resulting in excellent contrast effect with low background signal and high target to non-target ratios.
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