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

Abstract

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. <b>Methods:</b> 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 <i>Pseudomonas</i> 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 <i>in vitro</i> and <i>in vivo</i>. Cell viability assays and SiHa tumor-bearing nude mice were used to evaluate the efficacy of Z_{HPV16 E7} affitoxin384 <i>in vitro</i> and <i>in vivo</i>, respectively. <b>Results:</b> Using <i>in vitro</i> 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 <i>in vivo</i>. Z_HPV16E7 affitoxin384 showed significant <i>in vivo</i> antitumor efficacy in two kinds of tumor-bearing nude mouse models. <b>Conclusions:</b> Z_HPV16E7 affitoxin384 is a potent anti-cervical cancer therapeutic agent that could be effective against HPV16 positive tumors in humans.