Abstract 2008: Induced macropinocytosis by DNA-PK inhibitor for KRAS mutant cancer targeting of albumin-binding peptide drug conjugate
Authors: Kim Ha Rin , Park Seong Jin , Mudhibadhi Moyo Knowledge , Park Jae Hee , Byun Youngro 
Published: April 2023

Although Kirsten Rat Sarcoma Viral Oncogene Homolog (KRAS) is the most well-known tumor driver gene with the highest mutation rate in several types of cancer, there is no effective mutant KRAS targeting drug yet. Recent studies have reported that macropinocytosis can be increased in cancers with the KRAS mutation. Accordingly, several attempts have been made to deliver therapeutic agents to tumor using the phenomena related to albumin metabolism.To target KRAS mutant cancer cells, we adopted a previously developed albumin-binding caspase-3 cleavable peptide doxorubicin conjugate (MPD1). MPD1 is composed of albumin-binding moiety, caspase-3 substrate (DEVD peptide), and doxorubicin. The albumin-bound MPD1 is delivered into KRAS mutant cancer cells via macropinocytosis and induces apoptosis. Then, the induced caspase-3 cleaves DEVD sequence of MPD1 in the tumor microenvironment and produces free doxorubicin successively exerting in situ amplification and overcoming tumor heterogeneity. In this study, we proposed a strategy for effectively delivering and accumulating MPD1 to tumors by promoting altered albumin uptake of KRAS-mutated tumors. We discovered that DNA-PK inhibitor, one of the anticancer drugs that inhibit DNA damage repairing, selectively increases albumin uptake in tumor cells with KRAS mutation. We found that this is due to activated PI3K signaling in KRAS mutant tumor cells. In particular, this investigation has revealed that DNA-PK inhibitor increased albumin uptake by activating the AMPK in PI3K signaling enhanced cancer. AMP-activated protein kinase (AMPK) is a vital cellular energy sensor, so once AMPK is activated by insufficient nutrition level of cells, it activates albumin uptake for nutrient scavenging to restore low energy status. Therefore, because DNA-PK inhibitor activate AMPK-dependent macropinocytosis, it selectively increases albumin uptake in KRAS mutant cancer, enabling tumor targeting of MPD1. In addition, doxorubicin is accumulated in tumors through the caspase-3 amplification system described above overcoming tumor heterogeneity. We demonstrated that MPD1 and DNA-PK inhibitor combination therapy exerted 100% complete remission in the KRAS mutant TNBC xenograft model, suggesting its potent clinical applicability.In conclusion, our results indicate that DNA-PK inhibitor enhances macropinocytosis in an AMPK-dependent manner. We further demonstrate that DNA-PK inhibitor has a dual role of preventing DNA repair as an anticancer agent and elevating nutrient-scavenging pathway in KRAS mutant cancer as a mean of drug delivery. Thus, the albumin-binding self-amplifying MPD1 synergizes its cytotoxic effects at the tumor site with the DNA-PK inhibitors. We believe that this proposed strategy is a valuable approach to broadening the therapeutic benefit for PI3K-activated cancers including KRAS mutant cancer.

Citation Format: Ha Rin Kim, Seong Jin Park, Moyo Knowledge Mudhibadhi, Jae Hee Park, Youngro Byun. Induced macropinocytosis by DNA-PK inhibitor for KRAS mutant cancer targeting of albumin-binding peptide drug conjugate [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2008.