Targeting the Lysosomal Acid Lipase A to Stress Out Ovarian Cancer
Abstract
Ovarian cancer (OCa) is the deadliest of all gynecologic cancers. The molecular basis of this disease is not completely understood. Currently approved therapies (such as cytoreductive surgery, combination of platinum-based chemotherapy, PARP inhibitors) have improved OCa survival for clinically localized disease and are widely used. Despite these advances, the majority (~90%) of patients with high-grade serous OCa (HGSOC) relapse with incurable metastases. Unfortunately, the overall survival for metastatic OCa is dismal (<20% 5-year survival) and has not changed significantly for several decades. The genetic variability and heterogeneity of OCa between tumors from the same patient and between tumors from different patients limits the utility of targeted therapies in OCa. New therapeutic strategies are desperately needed to improve OCa patient survival. OCa cells have a high growth rate and have a sustained and enhanced demand for new protein synthesis, folding, and maturation. Since proper folding and maturation of most cellular proteins occurs in a subcellular organelle called endoplasmic reticulum (ER), OCa cells have a high basal level of ER stress (ERS). While the OCa cells have evolved mechanisms to tolerate the high level of ERS, we and others have noted that further induction of ERS can be lethal to OCa cells via induction of apoptotic or cell death pathways. We reasoned that the enhanced basal level of ERS in OCa represents a critical and common vulnerability in OCa and drugs that further aggravate this already engaged system can cause cell death in OCa cells. From a screen of a curated small molecule library, we identified a small chemical molecule ERX-41 that dramatically induces ERS in OCa cells and causes OCa cell death. Importantly, ERX-41 enhances ERS in OCa cells from multiple genetic backgrounds, suggesting that it targets a common molecular vulnerability in OCa. In contrast, normal cells have low basal levels of ERS and are not affected by ERX-41, thus limiting the toxicity of ERX-41. Our initial studies strongly support our hypothesis that higher basal ERS in OCa represents a general and critical vulnerability for OCa cells. Using elegant genetic studies, we have identified a cellular protein, LIPA, as critical for ERX-41 activity. OCa cells that are genetically manipulated to not express LIPA do not respond to ERX-41. We have shown that LIPA binds ERX-41 and that this interaction is critical for ERX-41 activity. However, the mechanistic details of how the interaction of ERX-41 with LIPA causes changes in the ER to induce ERS in OCa cells are not known. Importantly, although normal cells express LIPA, the reasons for a lack of induction of ERS in normal cells by ERX-41 is also not known. Thus, the primary objective of this proposal is to perform a series of mechanistic studies that examine how ERX-41 binding to LIPA causes ERS in OCa. We will specifically contrast mechanistically how ERX-41 does not cause ERS in normal cells. We will also validate that ERX-41 is active against OCa from multiple genetic backgrounds, which will demonstrate the potential of our approach in overcoming the heterogeneity of OCa. We will test the hypothesis using two specific aims: In specific aim 1, we will determine molecular mechanisms by which targeting LIPA contribute to ERS in OCa. We have reconstituted OCa cells with LIPA mutants that do not bind ERX-41 and do not respond to LIPA. Using the parental OCa with LIPA and the LIPA mutant cells, we will define critical interactors of LIPA in the ER that are affected by ERX-41. We will study how morphologically ERX-41 changes the ER structure in OCa cells with LIPA, but not in OCa cells with LIPA mutants or in normal cells. We will use state-of-the-art molecular techniques to identify how ERX-41 binding to LIPA in the ER affects LIPA function in the ER and causes ERS. Using the same approach, we will also define why ERX-41 does not cause ERS in no
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 28, 2022
- Source ID
- W81XWH2210181
Entities
People
- Ganesh V Raj
Organizations
- United States Army
- University of Texas Southwestern Medical Center