Pitt Pediatrics congratulates Amanda Poholek, PhD, for her grant award from the Career Enhancement Program (CEP) of the Melanoma and Skin Cancer Program SPORE at the University of Pittsburgh and UPMC Hillman Cancer Center. 
Poholek’s project titled “Identifying the immunotherapy driven epigenetic landscape that underlies transcriptional changes in tumor infiltrating CB8 T cells” is focused on understanding how immune cells integrate signals encountered in the environment to drive functional outcomes at the molecular and epigenetic level in both health and disease.
Checkpoint blockade immunotherapy for melanoma has been revolutionary for patients. However, not all patients respond, prompting research into the mechanisms. Believed to be a primary target of checkpoint blockade, CD8 T cells exhibit profound dysfunction (termed exhaustion) in the tumor, limiting their cytotoxic potential for tumor clearance. Exhaustion is a heterogenous state of differentiation, which we now understand to be progressive in response to both persistent antigenic stimulation and tumor microenvironmental signals. Initially thought to reverse exhaustion, the checkpoint blockade therapy anti-PD-1 is now understood to have several cellular targets in both the tumor and draining lymph node. Early studies investigating anti-PD-1 immunotherapy in settings of exhaustion mediated by chronic viral infection determined that exhausted T cells retained epigenetic features after anti-PD-1 despite increased effector function and transcriptional changes. However, a comprehensive study of the epigenome in a melanoma that assess changes across exhaustion subsets has not been reported.
In Poholek’s study, they wanted to revisit the question in context of melanoma. Using the anti-PD-1 sensitive murine melanoma cell line YUMMER1.7, she and her team would dive deep into the epigenome using CUT&Tag to profile 5 histone modifications and DNA binding proteins. Secondly, they will interrogate changes in the epigenome after anti-PD-1 therapy exploring both CD8 T cells from draining lymph node as well as precursor and terminal exhausted populations from the TIL. Finally, they would use a new adaptation of the CUT&Tag technology termed Multi-Cut&Tag to simultaneously profile epigenetic modifications of CD8 TIL isolated from melanoma at the single cell level.
This study will carefully assess epigenetic changes in response to immunotherapy and utilize an innovative tool to understand the single- cell epigenetic landscape that underlies the progression to exhaustion, and the outcome of this study will have important implications on the combination therapies that may better prevent exhaustion or increase the proliferative burst of anti-tumor CD8 T cells.
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