AN IN VITRO TUMOR ORGANOIDS PLATFORM TO UNCOVER MECHANISMS OF CANCER CHEMOTHERAPY

Abstract

Rare cancers individually consist of few cases, yet their combined public health burden is tremendous. With the rapid growth in therapeutic development, the opportunities to help patients with has never seemed more achievable. However, testing these new treatments remains difficult, with clinical trial design and execution lacking in the clinical setting and our subsequent understanding of these rare tumors remains stymied. One of the more promising methods of understanding how rare tumors may respond to treatment is through testing patient derived in vitro models. Organoids have risen to the challenge as an accurate, high throughput system which excels at maintaining primary cells. Our goal was to create organoid models to study rare cancers for their applications in clinical trial development and to better understand the mechanisms of HIPEC treatment, the gold standard therapeutic option in patients with appendiceal cancer presenting with peritoneal carcinomatosis. Specifically, we strived to determine the role of DNA repair in HIPEC treatment and to determine if there were potential predictive mechanisms for its efficacy.To achieve these goals, we created patient derived organoids from sarcoma and appendiceal tissues. These organoids were amenable to immune cell supplementation and could test both standard chemotherapy and immunotherapy for treatment selection. The next stage was the creation of a new platform for HIPEC treatment in colorectal and appendiceal tumor organoids Results demonstrated the importance of heat, timing, and choice of perfusate in this system, which matched the results of a multicenter clinical trial published after the completion of our study. We then elucidated the importance of PTIP, a protein with activity in multiple pathways of DNA repair, in dictating tumor resistance to HIPEC treatment. Patient tissues with low expression of the protein created PTOs more resistant to HIPEC treatment. siRNA knockdown of PTIP in a lab generated appendiceal cell line led to increased treatment resistance and decreased activation of the HR pathway. These results could be utilized to further our understanding of treatment resistance in appendiceal cancer for HIPEC and other, newer therapeutic options