Investigating the Molecular and Phenotypic Differences in Pancreatic Neuroendocrine Tumor (PanNET) Cells with Functional Loss of Either ATRX or DAXX

Abstract

Telomeres are hexameric DNA repeats at the ends of linear chromosomes that protect genomic integrity. Telomeres shorten after each cell division until a critically shortened length is reached, whereby the cell enters a state of cellular senescence. Cancer cells must overcome this replicative barrier by either upregulating the enzyme telomerase or by using the Alternative Lengthening of Telomeres (ALT) pathway, which uses homology‐directed repair to maintain telomere lengths. ALT is present in ~10% of cancers, yet the exact underlying mechanisms are still being elucidated. However, two known drivers of ALT are loss of function mutations in either ATRX or DAXX, genes that encode a chromatin remodeling complex. Mutations in these genes were initially identified and linked to ALT in pancreatic neuroendocrine tumors (PanNETs), which are the second most common malignancy of the pancreas. This study evaluated the molecular and phenotypic differences between parental PanNET cells (BON1 and QGP1) and isogenic clones with either ATRX or DAXX knocked out via CRISPR‐Cas9 gene editing. The matched parental and isogenic clones were assessed for cell proliferation (MTS assay), clonogenic survival (colony formation assay), and invasion potential (Matrigel invasion assay). Preliminary results for QGP1 cells indicate that the ATRXKO clones show decreased proliferation and colony formation, as well as alterations in invasion potential compared to the parental cell line, thereby suggesting that functional loss of ATRX alters these phenotypic properties. Future studies will help to contribute to the ongoing efforts to understand the underlying mechanisms of ALT and work towards the overall goal of identifying potential biomarkers for early detection, prognosis, and targeted therapies for ALT‐positive cancers.