Molecular Imaging of Breast Cancer: Role of RGD Peptides.

Breast cancer is the leading cause of cancer deaths among women of all ages worldwide. With advances in molecular imaging procedures, it has been possible to detect breast cancer in its early stage, determine the extent of the disease to administer appropriate therapeutic protocol and also monitor the effects of treatment. By accurately characterizing the tumor properties and biological processes involved, molecular imaging can play a crucial role in minimizing the morbidity and mortality associated with breast cancer. The integrin αvβ3 plays an important role in breast cancer angiogenesis and is expressed on tumor endothelial cells as well as on some tumor cells. It is a receptor for the extracellular matrix proteins with the exposed arginine-glycine-aspartic acid (RGD) tripeptide sequence and therefore RGD peptides can preferentially bind to integrin αvβ3. In this context, targeting tumor vasculature or tumor cells by RGD-based probes is a promising strategy for molecular imaging of breast cancer. Using RGD-based probes, several preclinical studies have employed different imaging modalities such as positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), ultrasound and optical imaging for visualization of integrin αvβ3 expression in breast cancer models. Limited clinical trials using (18)F-labeled RGD peptides have also been initiated for non-invasive detection and staging of breast cancer. Herein, we provide a comprehensive overview of the latest advances in molecular imaging of breast cancer using RGD peptide-based probes and discuss the challenges and opportunities for advancement of the field. The reported strategies for molecular imaging of breast cancer using RGD peptide-based probes holds promise for making clinically translatable advances that can positively impact the overall diagnostic and therapeutic processes and result in improved quality of life for breast cancer patients.