Abstract 1512: Architectural protein HMGB3 interacts with cisplatin-resistance associated overexpressed protein (CROP/LUC7L3) in human cancer cells and modulates cisplatin-DNA adduct removal
Authors: Mukherjee Anirban , Benhamou Lorraine-Rana , Vasquez Karen M. 
Published: June 2022

Abstract
Cancer treatment and management have improved substantially in recent years resulting in increased overall patient survival. However, upon recurrence, many tumors can eventually stop responding to treatment and become resistant to therapy. Therefore, sensitizing cancer cells to therapy is an important approach to increase overall patient survival and improve their quality of life. We have previously shown that targeting the chromatin associated architectural protein High Mobility Group Box 3 (HMGB3) can sensitize cisplatin resistant human ovarian cancer cells to cisplatin. HMGB proteins are non-histone chromatin proteins, which bind to distorted DNA structures with higher affinity compared to double-stranded DNA. HMGB proteins have been shown to play important roles in DNA metabolism, such as replication, transcription and repair. We found that the sensitization of cisplatin resistant human A2780/CP70 ovarian cancer cells by siRNA-mediated targeting of HMGB3 is achieved, at least in part, by significantly lowering the expression of the DNA damage response (DDR) proteins ATR and CHK1. In addition, depletion of HMGB3 repressed global transcription by ~50% in human osteosarcoma (U2OS) cells. Here we report that GFP-tagged HMGB3 protein forms distinct foci in human A2780 ovarian cancer cells upon cisplatin treatment. Further, depleting HMGB3 in cisplatin resistant A2780/CP70 cells reduces the rate of cisplatin-DNA adduct removal, suggesting a possible role in chemoresistance. In addition, mass spectrometry studies reveal that HMGB3 interacts with the cisplatin resistance-associated overexpressed protein (CROP, also known as LUC7L3 ), following treatment with the DNA interstrand crosslink-inducing agent, psoralen (plus UVA irradiation). LUC7L3 is associated with the spliceosome and is overexpressed in A2780/CP70 cells compared to A2780 ovarian cancer cells. SiRNA-mediated depletion of HMGB3 reduces the transcription levels of LUC7L3. Further, siRNA-mediated depletion of LUC7L3 reduced the clone forming capacity of U2OS cells and ovarian cancer cells. Analysis of cancer patient databases revealed that LUC7L3 mRNA is overexpressed in many cancer types including ovarian cancer. Further analysis showed that ovarian cancer, gastric cancer, liver cancer and lung cancer patients overexpressing LUC7L3 have a significantly reduced overall survival than those with lower levels. Taken together, these data indicate that in addition to the architectural roles of HMGB3, which is important for DNA metabolism, transcriptional modulation of DDR proteins through interaction with the spliceosome may be another way that HMGB3 modulates chemotherapeutic DNA damage processing in human cancer cells.
Citation Format: Anirban Mukherjee, Lorraine-Rana Benhamou, Karen M. Vasquez. Architectural protein HMGB3 interacts with cisplatin-resistance associated overexpressed protein (CROP/LUC7L3) in human cancer cells and modulates cisplatin-DNA adduct removal [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1512.