Senolytic agent ABT-263 mitigates low- and high-LET radiation-induced gastrointestinal cancer development in Apc1638N/+ mice.

Abstract

Exposure to ionizing radiation (IR), both low-LET (e.g., X-rays, γ rays) and high-LET (e.g., heavy ions), increases the risk of gastrointestinal (GI) cancer. Previous studies have linked IR-induced GI cancer to cellular senescence associated secretory phenotype (SASP) signaling. This study explores the potential of senolytic therapy to mitigate IR-induced GI carcinogenesis. Male Apc^1638N/+ mice were exposed to γ and ²⁸Si-ions (69 keV/μm) IR. Two months later, they were treated with the senolytic agent ABT-263 orally for 5 days/week until euthanasia, followed by tumor counting and biospecimen collection at five months post-exposure. Tumors were classified as adenoma or carcinoma by a pathologist. Serum cytokine levels were measured, and the markers of senescence (p16), SASP (IL6), and oncogenic β-catenin signaling were assessed using in-situ immunostaining of intestinal tissue. Both low- and high-LET radiation exposure led to an increased frequency of adenoma and carcinoma in Apc^1638N/+ mice, accompanied by increased cellular senescence, acquisition of SASP, and overexpression of BCL-XL protein in a subset of these cells. Furthermore, administration of ABT-263 resulted in the elimination of senescent/SASP cells, a decrease in pro-inflammatory cytokines (TNFRSF1B, CCL20, CXCL4, P-selectin, CCL27, and CXCL16) at the systemic level, and downregulation of β-catenin signaling that coincided with decreased GI cancer development. This study suggests a link between IR-induced senescent/SASP cell accumulation and GI cancer development. It also shows that the senolytic agent ABT-263 can regulate IR-induced inflammatory cytokines and carcinogenic mediators both systemically and in intestinal tissue. These findings support the potential of senolytic intervention to reduce IR-induced GI cancer risk.