Described herein are compositions and methods for cancer cell biomarkers, such as pancreatic ductal adenocarcinoma (PDAC) cell biomarkers, and binding molecules for diagnosis and treatment of cancer, e.g., PDAC. Methods of identifying "accessible" proteomes are disclosed for identifying cancer biomarkers, such as plectin-1, a PDAC biomarker. Additionally, imaging compositions are provided comprising magnetofluorescent nanoparticles conjugated to peptide ligands for identifying PDACs.