As representatively shown for OSPC-ARK-1, a high grade serous papillary ovarian carcinoma (Figure 2 upper panel), fluorescein imaging revealed that CPE peptide bound to all highly chemotherapy-resistant tumor cell lines overexpressing claudin-3 and/or -4 while lack of intrinsic fluorescence was noted in the primary ovarian carcinoma tested (Figure 2 upper panel). The gene discussed is CLDN3; the disease is ovarian carcinoma.