Inhibition of USP28 overcomes Cisplatin-Resistance of Squamous Tumors by Suppression of the Fanconi Anemia Pathway.
Squamous cell carcinomas (SCC) frequently have a limited response to or develop resistance to platinum-based chemotherapy, and have an exceptionally high tumor mutational burden. As a consequence, overall survival is limited and novel therapeutic strategies are urgently required, especially in light of a rising incidences. SCC tumors express {Delta}Np63, a potent regulator of the Fanconi Anemia (FA) DNA-damage response pathway during chemotherapy, thereby directly contributing to chemotherapy-resistance. Here we report that the deubiquitylase USP28 affects the FA DNA repair pathway during cisplatin treatment in SCC, thereby influencing therapy outcome. In an ATR-dependent fashion, USP28 is phosphorylated and activated to positively regulate the DNA damage response. Inhibition of USP28 reduces recombinational repair via an {Delta}Np63-Fanconi Anemia pathway axis, and weakens the ability of tumor cells to accurately repair DNA. Our study presents a novel mechanism by which tumor cells, and in particular {Delta}Np63 expressing SCC, can be targeted to overcome chemotherapy resistance. SignificanceLimited treatment options and low response rates to chemotherapy are particularly common in patients with squamous cancer. The SCC specific transcription factor {Delta}Np63 enhances the expression of Fanconi Anemia genes, thereby contributing to recombinational DNA repair and Cisplatin resistance. Targeting the USP28-{Delta}Np63 axis in SCC tones down this DNA damage response pathways, thereby sensitizing SCC cells to cisplatin treatment.