Atrxdeletion impairs cGAS-STING signaling and increases response to radiation and oncolytic herpesvirus in sarcoma

Abstract

ATRX is one of the most frequently altered genes in solid tumors, and mutation is especially frequent in soft tissue sarcomas. However, the role of ATRX in tumor development and response to cancer therapies remains poorly understood. Here, we developed a primary mouse model of soft tissue sarcoma and showed that Atrx deleted tumors are more sensitive to radiation therapy. In the absence of Atrx, irradiated sarcomas have increased persistent DNA damage, telomere dysfunction, and mitotic catastrophe. We find that Atrx deleted sarcomas have a reduced adaptive immune response, impaired cGAS-STING signaling, and increased sensitivity to an oncolytic herpesvirus therapy. Translation of these results to patients with ATRX mutant cancers could enable genomically-guided cancer therapeutic approaches that improve patient outcomes.

Loss of function ofAtrxleads to activation of alternative lengthening of telomeres in a primary mouse model of sarcoma

“…To initiate primary tumors in these mice, we designed a two-plasmid system to activate oncogenic Kras G12D and to induce the loss of function of either Trp53 (CAST KP model) or Trp53 and Atrx (CAST KPA model). In this model, the intramuscular injection and electroporation of plasmids into the right hind limb of mice leads to the formation of spatially and temporally restricted soft tissue sarcomas after approximately 60 days, and this is similar to previously published models 27,28 (Figure 1A). The first plasmid activates oncogenic Kras G12D using homology directed repair and the second plasmid contains single guide RNAs (sgRNAs) which induce insertion/deletion (indel) mutations to either Trp53 alone or Trp53 and Atrx (Figure 1B).…”

“…Cell lines with either wild type or non-frameshift sequences demonstrated normal levels of protein expression of Atrx , while a cell line with frameshift and structural variant sequences demonstrated loss of Atrx protein expression (Figure 2C). Because the loss of Trp53 and activation of oncogenic Kras G12D is sufficient to drive tumorigenesis in mice, an additional loss of function mutation of Atrx is not required for tumor formation 27 . Therefore, tumors which retain expression of Atrx after non-frameshift mutations are classified as CAST KPA* to denote the existence of non-frameshift mutations of Atrx and the possible retention of Atrx function.…”

“…Cell lines with either wild type or non-frameshift sequences demonstrated normal levels of protein expression of Atrx, while a cell line with frameshift and structural variant sequences demonstrated loss of Atrx protein expression (Figure 2C). Because the loss of Trp53 and activation of oncogenic Kras G12D is sufficient to drive tumorigenesis in mice, an additional loss of function mutation of Atrx is not required for tumor formation 27 .…”

Emerging mechanisms and implications of cGAS-STING signaling in cancer immunotherapy strategies

“…In a primary mouse model of soft tissue sarcoma, depletion of alpha-thalassemia mental retardation X-linked (Atrx), a chromatin remodeling protein and tumor suppressor, significantly intensifies radiation-induced persistent DNA damage, telomere dysfunction, and mitotic catastrophe. Remarkably, this process coincides with a pronounced impairment in the cGAS-STING-interferon signaling pathway 91 .…”