A novel HPV16 E7-affitoxin for targeted therapy of HPV16-induced human cervical cancer

Cervical cancer, the second most common cause of cancer death in women worldwide, is significantly associated with infection of high-risk human papillomaviruses (HPVs), especially the most common genotype, HPV 16. To date, there is no established noninvasive therapy to treat cervical cancer. Methods: Here, we report a novel affitoxin that targets HPV16 E7 protein, one of the primary target proteins in molecular targeted therapy for HPV-induced cervical cancer. The affitoxin, Z(HPV16E7) affitoxin384 was generated by fusing the modified Pseudomonas Exotoxin A (PE38KDEL) to the HPV16 E7-specific affibody. The expressed and purified Z(HPV16E7) affitoxin384 was characterized using numerous methods. SPR assay, indirect immunofluorescence assay, and near-infrared (NIR) optical imaging were respectively performed to assess the targeting ability of Z(HPV16E7) affitoxin384 to HPV16 E7 protein both in vitro and in vivo. Cell viability assays and SiHa tumor-bearing nude mice were used to evaluate the efficacy of Z(HPV16 E7) affitoxin384 in vitro and in vivo, respectively. Results: Using in vitro methods the SPR assay and indirect immunofluorescence assay showed that Z(HPV16E7) affitoxin384 targeted HPV16 E7 with high binding affinity and specificity. Significant reduction of cell viability in HPV16 positive cells was observed in the presence of Z(HPV16 E7) affitoxin384. By NIR optical imaging, Z(HPV16 E7) affitoxin384 specifically targeted HPV16 positive tumors in vivo. Z(HPV16E7) affitoxin384 showed significant in vivo antitumor efficacy in two kinds of tumor-bearing nude mouse models. Conclusions: Z(HPV16E7) affitoxin384 is a potent anti-cervical cancer therapeutic agent that could be effective against HPV16 positive tumors in humans.