Abstract 4010: Identification of novel targeted and immunotherapy combinations by a high throughput assay of T cell-mediated cytotoxicity
Authors: Williams Leila , Malu Shruti , McKenzie Jodi , Mbofung Rina , Forget Marie-Andree , Bernatchez Chantale , Hwu Patrick 
Published: July 2016

Melanoma is the major cause of skin cancer-related deaths. However, the recent emergence of immune checkpoint inhibitors such as Ipilimumab (anti-CTLA-4) and Nivolumab (anti-PD-1), and adoptive cell therapy, using tumor infiltrating lymphocytes (TILs), has improved clinical outcomes and produced response rates of approximately 50%. Despite the progress made in melanoma immunotherapy, there is a large cohort of patients for which these treatments are currently not applicable. They are either inherently resistant to or acquire resistance to immunotherapy. As such, understanding mechanisms of resistance to immune response and ascertaining efficacious therapy combinations is important in overcoming immunoresistance and developing novel treatment regimens.

As proof of principle, preliminary work using a unique protocol for an in vitro T-cell mediated cytotoxicity screen was established. In this assay, intracellular staining of active caspase-3 in tumor cells, a marker of apoptosis, is measured by flow cytometry in a 96-well format. Using patient-derived tumor and TIL pairs, a screen of 850 compounds was performed to find candidate drugs that could modulate the sensitivity of tumor cells to T- cell mediated killing. Initial screens identified classes of compounds that inhibit Heat shock protein 90 (Hsp90), Aurora Kinase and Topoisomerase I, and studies to understand their mechanisms of action are currently underway.

However, as this screening process is very time-intensive, we are currently increasing the efficiency and feasibility of this screen by miniaturizing this workflow. This work presents the development of a screening method that is performed in a 384-well format, with a greater drug concentration range, and utilizing robotics to streamline and increase output. With this, we can specifically identify novel targeted and immunotherapy combinations that may be used in the clinic to treat melanoma. Additionally, by understanding the signaling pathways and molecular factors that regulate tumor response to T cell mediated killing, we can translate these findings into making immune-based cancer therapies applicable to other tumor types. This project aims to discover novel compounds that work synergistically with T-cell mediated tumor cell cytotoxicity, understand their mechanism of action and how they contribute to resistance and as a result identify innovative immune-based therapies that can be translated into clinical use.

Citation Format: Leila Williams, Shruti Malu, Jodi McKenzie, Rina Mbofung, Marie-Andree Forget, Chantale Bernatchez, Patrick Hwu. Identification of novel targeted and immunotherapy combinations by a high throughput assay of T cell-mediated cytotoxicity. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4010.