MBs_NRP2-based ultrasound molecular imaging for early diagnosis of castration-resistant prostate cancer

Prostate cancer is one of the most prevalent malignancies in men. Once prostate cancer advances to castration-resistant prostate cancer (CRPC), the 5-year survival rate can decrease to as low as 14 months. However, the current primary diagnostic method, PSA testing, is associated with a lengthy detection cycle, limited accuracy, and delays in identifying disease progression. Consequently, there is an urgent need to develop an imaging technique that enables early and accurate diagnosis of CRPC.

First, immunofluorescence was used to verify that the expression of NRP2 on endothelial cells of neovasculature increased with the progression of prostate cancer. Next, NRP2-modified microbubbles (MBs_NRP2) were prepared, and their specific targeting ability to endothelial cells was validated through parallel plate flow experiments. Subsequently, co-culture systems of prostate cancer cells and endothelial cells were established. Based on this, the proangiogenic effect of prostate cancer was systematically explored, and the differential expression of NRP2 was analyzed. A combination of immunofluorescence localization, flow cytometry, western blotting, and angiogenesis assays was used. Finally, in a subcutaneous tumor-bearing mouse model, ultrasound molecular imaging (USMI) was implemented, and the ultrasound contrast intensity of attached MBs_NRP2 was monitored and quantitatively analyzed.

This study confirmed the clear colocalization of NRP2 with CD31 in prostate cancer tissues. Secondly, MBs_NRP2 exhibited specific binding ability under dynamic conditions to microvascular endothelial cells (HMEC-1). Subsequently, with the progression of CRPC, the expression of NRP2 on HMEC-1 cells gradually increased, accompanied by a significant enhancement in their angiogenic capacity. Lastly, compared with control mice, the USMI signals in tumor-bearing mice from the hormone-sensitive prostate cancer (HSPC), non metastatic, castration-resistant prostate cancer (nmCRPC), and metastatic, castration-resistant prostate cancer (mCRPC) groups were significantly increased. This finding provides a potential new pathway for clinical diagnosis of the development of CRPC.

Regarding the progression of prostate cancer, the expression of NRP2 on neovascular endothelial cells gradually increases, potentially serving as a molecular target for early diagnosis of CRPC. The attached MBs_NRP2 intensity has significant differences in prostate cancer models at different stages. These findings suggest that ultrasound contrast imaging based on MBs_NRP2 could be a novel strategy for the early diagnosis of CRPC.