The driving theme of all projects in the Hill lab is how DNA damage repair defects contribute to epithelial ovarian cancer. We have multiple active projects ongoing focusing on various aspects of ovarian cancer development and disease progression all with the goal of making ovarian cancer a more manageable disease for every patient.
Understanding how stressing tumor cell DNA damage repair defects leads to alterations in the tumor microenvironment and therapeutic response: Patients with High Grade Serous Ovarian Cancer (HGSC) have limited therapeutic options. Immune therapies have had limited effect thus far, however, genomic analysis suggests that up to 50% of HGSCs have genomic alterations that may confer a DNA damage repair defect in homologous recombination or stalled replication fork protection, making therapies that target repair defects, like carboplatin and PARP inhibitors, important additional options. As repair defects in tumor cells are stressed by initial treatment with crosslinking agents like platinum or later with PARP inhibitors, this stress can over time lead to loss of the targetable molecular DNA damage repair defects in the tumor cells, alterations in the overall tumor cell state, and alterations in the interaction of the tumor cells with the surrounding stroma and immune cells, all of which contribute to resistance of the tumor to systemic and targeted therapies. Studying the tumor cells by themselves is not enough to understand the complexity of tumor therapeutic resistance, and thus the Hill lab is focused on generating more complete organoid models containing tumor cells, stromal cells, and a full complement of immune cells based on our previous work generating media and growth conditions for HGSC organoids (Hill et al.). These more complete models will allow for more accurate modeling of drug response to chemotherapeutic, targeted, and immuno-oncologic agents in a complex and changing tumor microenvironment in which cellular interactions are critical. Each cell within the culture can be manipulated to understand how specific alterations to the system lead to altered therapeutic response. These models will give us mechanistic insight into tumor evolution and drug response and will also allow us to understand whether ovarian cancer organoids can be utilized to predict patient response. Beyond HGSC, we are also now modeling low grade serous, clear cell and mucinous subtypes and studying relevant therapies for each subtype. All in vitro findings are being validated in unique organoid xenograft models generated in the Hill lab and syngeneic or genetically engineered mouse models.
All organoids being generated are being tested with a standard series of functional assays to determine if functional assays specific for each ovarian cancer subtype performed in the tumor organoids alone will be predictive of patient response to specific therapies. A major goal of the Hill lab is to span the gap between the lab and the clinic by developing organoids as biomarkers for patient response to specific therapies.
Understanding the contribution of stalled replication fork protection defects to ovarian carcinogenesis and therapeutic response: Our initial work using functional assays to study the DNA damage response in high grade serous ovarian cancer (HGSC) organoid models has indicated that stalled replication fork protection defects are highly prevalent in HGSCs (S. Hill et al.) and that such defects may lead to specific therapeutic responses. However, a better understanding of each unique type of defect is required to determine which defects lead to specific drug responses, which defects lead to specific types of resistance, and what biomarkers can be utilized to predict which patients will respond to specific replication stress inducing agents. We are utilizing molecular biology and sequencing techniques in ovarian cancer cell lines, organoids, and mouse models to study specific proteins involved in replication stress both at the molecular and transcriptional level to help understand the mechanisms by which specific fork protection defects contribute to therapeutic response. In addition, we are utilizing functional assays in patient derived organoid models to better understand the prevalance of stalled fork defects across ovarian cancer subtypes and which functional defects lead to therapeutic response in each subtype. We hope that these organoid based functional assays may someday be used as biomarkers of patient response. Funding through DOD OCRP and AACR.
Finding methods of prevention and early detection for ovarian cancer: Ovarian cancer is a disease of prevention. Patients often present with late stage disease that has spread throughout the abdominal cavity that is difficult to treat both medically and surgically. Methods of early detection and prevention are desperately needed across all subtypes to make this disease more manageable. The ovary and fallopian tube are subject to constant exposure to estrogen and its metabolites along with fluid flow forces and cellular damage during ovulation. For high grade serous ovarian cancer, tumors are thought to develop from the fallopian tube, peritoneum, and possibly the ovarian surface epithelium, but it is not clear what the exact mechanisms of carcinogenesis are at each site. Since many high grade serous tumors harbor DNA damage repair gene mutations, our lab is generating patient-derived fallopian tube, peritoneal, and ovarian surface epithelium organoids from patients who carry mutations in DNA damage repair genes and utilizing these models to understand if these germline mutations lead to specific DNA damage repair defects in each cell type, and if so what happens to the epithelial and stromal cells when the repair defects are stressed by normal physiologic exposure and how this stress may contribute to high grade serous ovarian carcinogenesis. With this understanding, we may find changes in the benign cells that allow for biomarker development for detection of early lesions or methods to prevent malignant progression. In addition to high grade serous tumors, we are also exploring mechanisms of development of low grade serous carcinoma by studying serous borderline tumors and trying to understand how external stresses such as estrogen lead to malignant transformation and invasive capacity of these lesions which may also help develop biomarkers for detection of early lesions and possibly methods of prevention of progression to invasive lesions or disease spread. Funding through Tina's Wish.