CIGB-300 is a clinical-grade anti-
Protein Kinase CK2 peptide, binding both its substrate's phospho-acceptor site and the CK2α catalytic subunit. The cyclic p15 inhibitory domain of
CIGB-300 was initially selected in a phage display library screen for its ability to bind the CK2 phospho-acceptor domain ofHPV-16 E7. However, the actual role of this targeting in
CIGB-300 antitumoral mechanism remains unexplored. Here, we investigated the physical interaction of
CIGB-300 with HPV-E7 and its impact on CK2-mediated phosphorylation. Hence, we studied the relevance of targeting E7 phosphorylation for the cytotoxic effect induced by
CIGB-300. Finally, co-immunoprecipitation experiments followed by western blotting were performed to study the impact of the
peptide on the E7-pRB interaction. Interestingly, we found a clear binding of
CIGB-300 to the N terminal region of E7
proteins of the HPV-16 type. Accordingly, the in vivo physical interaction of the
peptide with HPV-16 E7 reduced CK2-mediated phosphorylation of E7, as well as its binding to the
tumor suppressor pRB. However, the targeting of E7 phosphorylation by
CIGB-300 seemed to be dispensable for the induction of cell death in HPV-18
cervical cancer-derived C4-1 cells. These findings unveil novel molecular clues to the means by which
CIGB-300 triggers cell death in
cervical cancer cells.